Basic terms for Mechanical Engineering

Basic terms for Mechanical Engineering

List of basic terms for Mechanical Engineering

1. Torque or Turning Force
2. Couple
3. Moment
4. Stress
5. Strain
6. Spring
7. Specific Weight
8. Specific Volume
9. Specific Gravity
10. Specific Heat
11. Viscosity
12. Buoyancy
13. Discharge of Fluid
14. Bernoulli’s Equation
15. Device for Fluid
16. Mach Number
17. Hydraulic Machine
18. Draft Tube
19. Thermodynamics Laws

  •  zeroth law
  • First law
  • second law

20. Entropy
21. calorific value of fuel
22. Boiler/Steam Generator
23. Superheater
24. Air Preheater
25. Boiler Draught
26. Nozzle
27. Scavenging
28. Supercharging
29. Turbocharging
30. Governor
31. Flywheel
32. Rating of fuel-
S.I. engine
C.I. engine
33. Stoichiometric Mixture/ Stoichiometric Ratio
34. Heat Transfer
35. Thermal Conductivity
36. Heat Exchanger
37. Refrigeration
38. 1 tonne Refrigeration
39. Humidification
40. Dehumidification
41. Gear Train
42. Gyroscopic Couple
43. Heat Treatment
44. Ferrous-Metal
45. Non-ferrous metal
46. Allowance
47. Tolerance
48. Clearance
49. Stiffness
50. Toughness
51. Fatigue
52. Nuclear Fission
53. Nuclear Fussion
54. Welding
55. Machine Tool
56. Cutting Tool
57. Indexing
58. Jig
59. Fixture

Details

Torque or Turning Force:
It is the total amount of force which is required to create acceleration on moving substance.

Couple:
Two forces those acts on equally,parallely & oppositely on two separate points of same material.

Moment:
It is the amount of moving effect which is gained for action of turning force.

Stress:
It is the force that can prevent equal & opposite force. That means, it is the preventing force. If one force acts on outside of a material, then a reactive force automatically acts to protest that force. The amount of reactive force per unit area is called stress. e.g. Tensile Stress, Compressive Stress, Thermal Stress.

Strain:
If a force acts on a substance, then in that case if the substance would deform. Then the amount of deformation per unit length of that substance is called strain.

Spring:
It is one type of device which is being distorted under certain amount of load & also can also go to its original face after the removal of that load.

Its function:

  • To store energy.
  • To absorb energy.
  • To control motion of two elements.

Stiffness:
Load per unit deflection. The amount of load required to resist the deflection.

Specific Weight:
Weight per unit volume of the fluid.

Specific Volume:
Volume per unit mass of the fluid.

Specific Gravity:
It is the ratio of specific weight of required substance to specific weight of pure water at 4 degree centigrade temperature.

Specific heat:
The amount of heat required to increase 1 unit temperature of 1 unit mass.

Viscosity:
Dynamic Viscosity:
The amount of resistance of one layer of fluid over other layer of fluid.

Kinematic Viscosity:
It is the ratio of dynamic viscosity to density.

Buoyancy:
When a body is immersed in a liquid, it is lifted up by a force equal to weight of liquid displaced by the body. The tendency of liquid to lift up an immersed body is buoyancy. The upward thrust of liquid to lift up the body is called buoyancy force.

Bernoulli’s Equation:
P/γ +V²/2g +Z = Constant

Where, P = pressure,V = velocity,Z = Datumn Head

Devices for fluid:

Venturimeter:
It measures discharge of fluid.
Notches :
It measures discharge of fluid.
Orifice meter:
It measures discharge of fluid.
Pitot tube :
It measures velocity of fluid.

Mach Number:
It is the ratio of the velocity of fluid to the velocity of sound.
M=1 —————– Sonic flow
M> (1-6) ———– Super-Sonic flow
M>6 —————- Hyper-Sonic flow

Fluid discharge/Fluid flow:
Quantity of fluid flowing per second.

(through a section of pipe/ through a section of channel)

Q=AV

where, V= velocity of fluid,A= cross-sectional area of pipe/channel
Note: 1m³ = 1000 L1 cusec = 1 ft³/sec1 ft = 0.3048 m

Hydraulic Machine:
Turbine,Pump,Compressor etc.

Draft tube:
It attaches with reaction turbine . Its function is to reduce energy loss from reaction turbine & it also reduce pressure at outlet which is must blow the atmospheric pressure.

Thermodynamics Laws:
Zeroth Law:
If two body are in thermal equilibrium with a third body then these two body are also in thermal equilibrium with each other.

First Law of Thermodynamics:
In a closed system, work deliver to the surrounding is directly proportonal to the heat taken from the surrounding.And also, In a closed system, work done on a system is directly proportonal to the heat deliver to the surrounding.

Second Law of Thermodynamics:
It is impossible to make a system or an engine which can change 100 percent input energy to 100 percent output.

Entropy:
It is a thermodynamic property.

ds = dq/T

where, ds = change of entropy, dq = change of heat, T = Temperature.

In adiabatic process, entropy can not change. Actually,lacking or mal-adroitness of tranfering energy of a system is entropy.

Calorific Value of fuel:
It us the total amount of heat obtained from burning 1 kg solid or liquid fuel.

Boiler/Steam Generator:
It is a clossed vessel which is made of steel. Its function is to transfer heat to water to generate steam.

Economizer:
It is a part of boiler. Its function is to heat feed water which is supplied to boiler.

Super-heater:
It is a part of boiler. Its function is to increase temperature of steam into boiler.

Air-Preheater:
It is a part of boiler. Its funtion is to preheats the air to be supplied to furnace and it recover heat from exhaust gas.

Boiler Draught:
It is an important term for boiler. It is the difference of pressure above and below the fire grate. This pressure difference have to maintain very carefully inside the boiler. It actually maintains the rate of steam generation. This depends on rate of fuel burning. Inside the boiler rate of fuel burning is maintained with rate of entry fresh air. If proper amount of fresh air never entered into the boiler, then proper amount of fuel inside the boiler never be burnt. So, proper fresh air enters into the boiler only by maintaining boiler draught.

Nozzle:
Nozzle is a duct of varying cros-sectional area. Actually, it is a passage of varying cross-sectional area. It converts steam’s heat energy into mechanical energy. It is one type of pipe or tube that carrying liquid or gas.

Scavenging:
It is the process of removing burnt gas from combustion chamber of engine cylinder.

Supercharging:
Actually, power output of engine depends on what amount of air enter into the engine through intake manifold. Amount of entry air if increased, then must be engine speed will increased. Amount of air will be increased by increasing inlet air density. The process of increasing inlet air density is supercharging. The device which is used for supercharging is called supercharger. Supercharger is driven by a belt from engine crankshaft. It is installed in intake system.

Turbocharging:
Turbocharging is similar to the supercharging. But in that case turbocharger is installed in exhaust system whereas supercharger is installed in intake system. Turbocharger is driven by force of exhaust gas. Generally, turbocharger is used for 2-stroke engine by utilizing exhaust energy of the engine, it recovers energy otherwise which would go waste.

Governor:
Its function id to regulate mean speed of engine when there are variation in the load. If load incrases on the engine, then engine’s speed must decrease. In that case supply of working fluid have to increase. In the otherway, if load decrease on the engine, then engine’ speed must increase. In that case supply of working fluid have to decrease.Governor automatcally, controls the supply of working fluid to the engine with varying load condition.

Flywheel:
It is the one of the main parts of the I.C. engine. Its main function id to store energy in the time of working stroke or expansion stroke. And, it releasesenergy to the crankshaft in the time of suction stroke, compression stroke & exhaust stroke. Because, engine has only one power producing stroke.

Rating of fuel:
S.I. Engine:
Octane number. Octane number indicates ability of fuel to resist knock.

C.I. Engine:
Cetane Number. Cetane number indicates ability of ignition of diesel fuel. That means, how much fast ignites diesel fuel.

Stoichiometric ratio:
It is the chemically correct air-fuel ratio by volume. By which theoretically sufficient oxygen will be gotten to burn all combustible elements in fuel completely.

Heat Transfer:
It is a science which deals with energy transfer between material bodies as a result of temperature difference.There are three way to heat transfer such as-ConductionConvectionRadiation

Thermal Conductivity:
It is the quantity of heat flows between two parts of solid material by conduction. In this case following consideration will be important fact-

  • Time—— 1 sec
  • Area of that solid material——– 1 m²
  • Thickness of that solid material—— 1m
  • Temperature difference between two parts of that material—— 1k

Heat Exchanger:
It is one type of device which can transfer heat from one fluid to another fluid. Example- Radiator, inter-cooler, preheater, condenser, boiler etc.

Refrigeration:
It is the process of removing heat from a substance. Actually, extraction of heat from a body whose temperature is already below the temperature of its surroundings.

1 tonne of refrigeration:
It is amount of refrigeration effect or cooling effect which is produced by uniform melting of 1 tonne ice in 24 hours from or at 0 degree centigrade or freezing 1 tonne water in 24 hours from or at 0 degree centigrade.

Humidification:
It is the addition of moisture to the air without change dry bulb temperatur.

Dehumidification:
It is the removal of moisture from the air without change dry bulb temperature.

Gear Train:
Meshing of two or more gear. It can transmit power from one shaft to another shaft.

Heat Treatment:
Operation involving heating and cooling of a metal in solid state for obtaining desirable condition without being changed chemical composition.Its object-increase hardness of metal.increase quality of metal ( heat, corrosion,wear resistance quality )improve machinability.

Ferrous Metal:
1. Cast Iron – (2-6.67)%C, Si, Mn, P, S

2. Steel – (0-2)%C

3. Wrought Iron – 99.5% Fe

Non-Ferrous Metal:
1. Brass – (Cu+Zn)

2. Bronze –

(Sn+Cu) —— Tin Bronze

(Si+Cu) ——- Silicon Bronze

(Al+Cu) ——- Aluminium Bronze

Allowance:
It is the difference between basic dimension of mating parts. That means, minimum clearance between mating parts that can be allowed.

Tolerance:
It is the difference between upper limit of dimension. It is also the permissible variation above and below the basic size. That means maximum permissible variation in dimensions.

Clearance:
It is the difference in size between mating parts. That means, in that case the outside dimension of the shaft is less than internal dimension of the hole.

Stiffness:
It is the ability to resist deformation.

Toughness:
It is the property to resist fracture.

Fatigue:
When a material is subjected to repeated stress below yield point stress, such type of failure is fatigue failure.

Nuclear Fission:
It is a nuclear reaction by which one big nucleous divided into two or more nucleous.

Nuclear Fusion:
It is also a nuclear reaction by which one big nucleus will produced by adding two small nucleus.

Welding:
It is the process of joining two similar or dissimilar metal by fusion.

Arc Welding –

* need D.C current

* produced (6000-7000) Degree Centegrade Temperature

Gas Welding –

* Oxy – acetylene flame join metals

* Oxygen & acetylene gas works

* produced 3200 Degree Centegrade Temperature

Machine Tool:
It is the power driven tool. It cut & form all kinds of metal parts.

Example – 1. Lathe  2. Drill Press 3. Shaper 4. Planer 5. Grinding  6. Miling  7. Broaching 8. Boring

Cutting Tool:

Tool Materials for Cutting Tool:
1. High Carbon Steel

2. High Speed Steel (W+Cr+V)

3. Carbide (W Carbide+Ti Carbide+Co Carbide)

Indexing:

It is the method of dividing periphery of job into equal number of division. Actually, it is the process of dividing circular or other shape of workpiece into equal space, division or angle.

Jig:
It is one type of device which hold & locate workpiece and also guide & control cutting tool. It uses in drilling, reaming and tapping.

Fixture:
It is one type of device which hold and locate workpiece. It uses in miling, grinding, planning & turning.

Introduction to Robotics

Introduction to Robotics

Robotics is a relatively young field of modern technology that crosses traditional engineering boundaries. Understanding the complexity of robots and their applications requires knowledge of electrical engineering, mechanical engineering, systems and industrial engineering, computer science, economics, and mathematics. New disciplines of engineering, such as manufacturing engineering, applications engineering, and knowledge engineering have emerged to deal with the complexity of the field of robotics and factory automation.

 The term robot was first introduced into our vocabulary by the Czech playwright Karel Capek in his 1920 play Rossum’s Universal Robots, the word robota being the Czech word for work. Since then the term has been applied to a great variety of mechanical devices, such as teleoperators, underwater vehicles, autonomous land rovers, etc. Virtually anything that operates with some degree of autonomy, usually under computer control, has at some point been called a robot. In this text the term robot will mean a computer controlled industrial manipulator of the type shown in Figure 1.1.

Robotics

This type of robot is essentially a mechanical arm operating under computer control. Such devices, though far from the robots of science fiction, are nevertheless extremely complex electro-mechanical systems whose analytical description requires advanced methods, presenting many challenging and interesting research problems.

An official definition of such a robot comes from the Robot Institute of America (RIA): A robot is a reprogrammable multifunctional manipulator designed to move material, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks.

The key element in the above definition is the reprogrammability of robots. It is the computer brain that gives the robot its utility and adaptability. The so-called robotics revolution is, in fact, part of the larger computer revolution.

Even this restricted version of a robot has several features that make it attractive in an industrial environment. Among the advantages often cited in favor of the introduction of robots are decreased labor costs, increased precision and productivity, increased flexibility compared with specialized machines, and more humane working conditions as dull, repetitive, or hazardous jobs are performed by robots.

The robot, as we have defined it, was born out of the marriage of two earlier technologies: teleoperators and numerically controlled milling machines. Teleoperators, or master-slave devices, were developed during the second world war to handle radioactive materials. Computer numerical control (CNC) was developed because of the high precision required in the machining of certain items, such as components of high performance aircraft. The first robots essentially combined the mechanical linkages of the teleoperator with the autonomy and programmability of CNC machines.

The first successful applications of robot manipulators generally involved some sort of material transfer, such as injection molding or stamping, where the robot merely attends a press to unload and either transfer or stack the finished parts. These first robots could be programmed to execute a sequence of movements, such as moving to a location A, closing a gripper, moving to a location B, etc., but had no external sensor capability. More complex applications, such as welding, grinding, deburring, and assembly require not only more complex motion but also some form of external sensing such as vision, tactile, or force-sensing, due to the increased interaction of the robot with its environment.

It should be pointed out that the important applications of robots are by no means limited to those industrial jobs where the robot is directly replacing a human worker. There are many other applications of robotics in areas where the use of humans is impractical or undesirable. Among these are undersea and planetary exploration, satellite retrieval and repair, the defusing of explosive devices, and work in radioactive environments. Finally, prostheses, such as artificial limbs, are themselves robotic devices requiring methods of analysis and design similar to those of industrial manipulators.

Classification of Robotic Manipulators

Robot manipulators can be classified by several criteria, such as their power source, or way in which the joints are actuated, their geometry, or kinematic structure, their intended application area, or their method of control. Such classification is useful primarily in order to determine which robot is right for a given task. For example, a hydraulic robot would not be suitable for food handling or clean room applications. We explain this in more detail below.

Power Source. Typically, robots are either electrically, hydraulically, or pneumatically powered. Hydraulic actuators are unrivaled in their speed of response and torque producing capability. Therefore, hydraulic robots are used primarily for lifting heavy loads. The drawbacks of hydraulic robots are that they tend to leak hydraulic fluid, require much more peripheral equipment (such as pumps, which require more maintenance), and they are noisy. Robots driven by DC- or AC-servo motors are increasingly popular since they are cheaper, cleaner and quieter. Pneumatic robots are inexpensive and simple but cannot be controlled precisely. As a result, pneumatic robots are limited in their range of applications and popularity.

Application Area. Robots are often classified by application into assembly and non-assembly robots. Assembly robots tend to be small, electrically driven and either revolute or SCARA (described below) in design. The main non-assembly application areas to date have been in welding, spray painting, material handling, and machine loading and unloading.

Method of Control. Robots are classified by control method into servo and non-servo robots. The earliest robots were non-servo robots. These robots are essentially open-loop devices whose movement is limited to predetermined mechanical stops, and they are useful primarily for materials transfer. In fact, according to the definition given previously, fixed stop robots hardly qualify as robots. Servo robots use closed-loop computer control to determine their motion and are thus capable of being truly multifunctional, reprogrammable devices.

Servo controlled robots are further classified according to the method that the controller uses to guide the end-effector. The simplest type of robot in this class is the point-to-point robot. A point-to-point robot can be taught a discrete set of points but there is no control on the path of the end-effector in between taught points. Such robots are usually taught a series of points with a teach pendant. The points are then stored and played back. Point-to-point robots are severely limited in their range of applications. In continuous path robots, on the other hand, the entire path of the end-effector can be controlled. For example, the robot end-effector can be taught to follow a straight line between two points or even to follow a contour such as a welding seam. In addition, the velocity and/or acceleration of the end-effector can often be controlled. These are the most advanced robots and require the most sophisticated computer controllers and software development.

Geometry. Most industrial manipulators at the present time have six or fewer degrees-of-freedom. These manipulators are usually classified kinematically on the basis of the first three joints of the arm, with the wrist being described separately. The majority of these manipulators fall into one of five geometric types: articulated (RRR), spherical (RRP), SCARA (RRP), cylindrical (RPP), or Cartesian (PPP)

Each of these five manipulator arms are serial link robots. A sixth distinct class of manipulators consists of the so-called parallel robot. In a parallel manipulator the links are arranged in a closed rather than open kinematic chain. 

Robotic Systems

A robot manipulator should be viewed as more than just a series of mechanical linkages. The mechanical arm is just one component in an overall Robotic System, illustrated in Figure 1.3, which consists of the arm, external power source, end-of-arm tooling, external and internal sensors, computer interface, and control computer.

Robotics

 Even the programmed software should be considered as an integral part of the overall system, since the manner in which the robot is programmed and controlled can have a major impact on its performance and subsequent range of applications.

Accuracy and Repeatability

The accuracy of a manipulator is a measure of how close the manipulator can come to a given point within its workspace. Repeatability is a measure of how close a manipulator can return to a previously taught point. The primary method of sensing positioning errors in most cases is with position encoders located at the joints, either on the shaft of the motor that actuates the joint or on the joint itself. There is typically no direct measurement of the end-effector position and orientation. One must rely on the assumed geometry of the manipulator and its rigidity to infer (i.e., to calculate) the end-effector position from the measured joint positions. Accuracy is affected therefore by computational errors, machining accuracy in the construction of the manipulator, flexibility effects such as the bending of the links under gravitational and other loads, ear backlash, and a host of other static and dynamic effects. It is primarily for this reason that robots are designed with extremely high rigidity. Without high rigidity, accuracy can only be improved by some sort of direct sensing of the end-effector position, such as with vision.

Once a point is taught to the manipulator, however, say with a teach pendant, the above effects are taken into account and the proper encoder values necessary to return to the given point are stored by the controlling computer. Repeatability therefore is affected primarily by the controller resolution. Controller resolution means the smallest increment of motion that the controller can sense. The resolution is computed as the total distance traveled by the tip divided by 2n, where n is the number of bits of encoder accuracy. In this context, linear axes, that is, prismatic joints, typically have higher resolution than revolute joints, since the straight-line distance traversed by the tip of a linear axis between two points is less than the corresponding arc length traced by the tip of a rotational link.

In addition, rotational axes usually result in a large amount of kinematic and dynamic coupling among the links with a resultant accumulation of errors and a more difficult control problem. One may wonder then what the advantages of revolute joints are in manipulator design.

The answer lies primarily in the increased dexterity and compactness of revolute joint designs. For example, Figure 1.4 shows that for the same range of motion, a rotational link can be made much smaller than a link with linear motion. Thus, manipulators made from revolute joints occupy a smaller working volume than manipulators with linear axes. This increases the ability of the manipulator to work in the same space with other robots, machines, and people. At the same time revolute joint manipulators are better able to maneuver around obstacles and have a wider range of possible applications.

Robotics

Wrists and End-Effectors

The joints in the kinematic chain between the arm and end effector are referred to as the wrist. The wrist joints are nearly always all revolute. It is increasingly common to design manipulators with spherical wrists, by which we mean wrists whose three joint axes intersect at a common point. The spherical wrist is represented symbolically in Figure 1.5.

Robotics

The spherical wrist greatly simplifies the kinematic analysis, effectively allowing one to decouple the positioning and orientation of the end effector. Typically, therefore, the manipulator will possess three degrees-of-freedom for position, which are produced by three or more joints in the arm. The number of degrees-of-freedom for orientation will then depend on the degrees-of-freedom of the wrist. It is common to find wrists having one, two, or three degrees-of-freedom depending of the application. For example, the SCARA robot shown in Figure 1.14 has four degrees-of-freedom: three for the arm, and one for the wrist, which has only a rotation about the final z-axis.

Robotics

It has been said that a robot is only as good as its hand or end-effector. The arm and wrist assemblies of a robot are used primarily for positioning the end-effector and any tool it may carry. It is the end-effector or tool that actually performs the work. The simplest type of end-effectors are grippers, which usually are capable of only two actions, opening and closing. While this is adequate for materials transfer, some parts handling, or gripping simple tools, it is not adequate for other tasks such as welding, assembly, grinding, etc. A great deal of research is therefore devoted to the design of special purpose end-effectors as well as to tools that can be rapidly changed as the task dictates. There is also much research on the development of anthropomorphic hands. Such hands have been developed both for prosthetic use and for use in manufacturing. 

Reference

Alternator vs Generator

Alternator vs Generator

Alternators and generators are two devices which generate electricity. An alternator can be called a type of generator. Although both these devices serve the same function, they are quite different in every other aspect.

An alternator is a charging system for cars that produces electricity. Generators are used in the production of large-scale electricity. Both alternators and generators convert mechanical energy into electrical energy. The main difference between them is in regard to what spins and what is fixed.

Alternator vs Generator

In an alternator, electricity is produced when a magnetic field spins inside the stator (windings of wire). In a generator, on the other hand, the armature or windings of wire spin inside a fixed magnetic field to generate electricity.

Alternators are considered more efficient than generators. Alternators conserve energy by using only the energy that is needed, while generators use all the energy that is produced. Alternators have a higher output than generators.
When it comes to polarization, alternators and generators are very different. While generators have to be polarized after installation, there is no need for polarization in alternators.

Alternator vs Generator

Alternator brushes last longer than those of generators. This is because the brushes in an alternator are used only for carrying current to power the rotor and the slip rings they ride are smooth.

There is another difference between generators and alternators when it comes to charging. An alternator will not charge a dead battery and if you do try to charge it, there is a possibility that it will burn out. A generator, however, can be used for charging a dead battery.

There is also a difference in size as alternators can fit into a small space, while generators are larger.

Summary:

  • an alternator, electricity is produced when a magnetic field spins inside the stator (windings of wire). On the other hand, the armature or the windings of wire in a generator spin inside a fixed magnetic field to generate electricity.
  • Alternators conserve energy by using only the energy that is needed. Generators use all the energy that is produced.
  • Alternators produce voltage when needed and generators produce voltage at all times.
  • Alternators generate a higher output than generators.

COMMONLY USED COMPUTER PROGRAMS IN HVAC

The usual need to look up values from various tables and charts makes the conventional hand calculation
quite laborious, time consuming and prone to errors and inaccuracies because of the tendency to simplify
truncate or interpolate tabulated values. Listed below are the suggested applications and methodology of
two computer programs Elite CHVAC and TRACE 700 that may be used in the cooling and heating load
calculations.

Elite CHVAC

CHVAC is a commercial Heating, Ventilation and Air Conditioning software platform developed by Elite
Software. This computer program calculates the maximum heating and cooling loads in commercial and
industrial buildings.

Listed below are capabilities of CHVAC:

  • Calculates peak heating and cooling loads
  • Calculates both heating & cooling airflow CFM requirements
  • Calculates run out and main trunk duct sizes
  • Automates compliance with ASHRAE Standard 62
  • Provides overall building envelope report
  • Spreadsheet file compatibility
  • Performs complete psychrometric analysis
  • Prints bar graphs and exploded pie charts
  • Exterior shading handles overhangs, fins, & glass tilt
  • Uses exact ASHRAE CLTD procedures
  • Built-in design weather data for hundreds of cities
  • Analyzes up to 12 months per calculation
  • Calculates 24 hours per design day
  • Allows unlimited number of zones per project
  • Zones may be grouped under 100 air handlers
  • Zones may be optionally grouped under VAV boxes
  • Allows 12 walls, 12 windows, and 5 roofs per zone
  • Allows simultaneous infiltration and ventilation
  • Allows different summer and winter air rates
  • Allows varying indoor conditions within a project
  • Allows 6 master roof types,8 master wall types, 8 master partition types, and 20 master glass types
  • Allows glass to be tilted from 0 to 180 degrees
  • Allows for roof and wall color effects
  • Provision for both VAV and constant volume systems
  • Proper handling of return air plenum loads
  • Accounts for people diversity in total building load
  • Computes supply fan horsepower and heat gains
  • Accounts for both draw-thru and blow-thru fans
  • Calculates reheat requirements if necessary
  • Computes supply and return duct gains and losses
  • Allows direct specification of supply CFM quantities
  • Allows specification of minimum supply air quantities
  • Allows heating only, cooling only, or both
  • Excess supply air can be handled as reheat, reserve capacity, or by adjusting the leaving coil conditions
  • Leaving coil conditions can be specified with a desired dry bulb temperature or a relative humidity
  • Calculates chilled and hot water coil flow rates
  • Allows for pretreated outside air
  • Allows heating and cooling safety factors
  • Lighting & equipment watts along with no. of people can be entered directly or on a per square foot basis
Calculation Method

CHVAC performs calculations using the CLTD/CLF procedures described in the ASHRAE Handbook of Fundamentals. The programs use exact CLTD and MSHGF table values where possible, otherwise direct
calculations are made. This calculation technique allows the programs to calculate for any building
orientation and still produce output results that can be easily verified by hand.

Program Input

CHVAC is a true Windows program that uses all the latest data entry techniques such as toolbars, hyper linked help, and form tabs. All input data is checked at the time of entry so that no improper data can be entered. Five types of data are requested: general project data, outdoor design data, building material data, air handler data, and specific zone data. The general project data includes the project and client name, designer, building opening and closing hours, internal operating load schedules, and any desired safety factors. The outdoor design data includes the summer and winter outdoor design conditions (automatically looked up for you if a city reference is given) and the desired ventilation and infiltration rates. The building material data includes the definition of master building material types for roofs, walls, partitions, glass sections, and exterior shading. A user defined material library is available for saving the data on common material types. The air handler data includes the fan and terminal type, the desired heating and cooling supply air temperatures and data for duct heat gains and losses. The zone data includes the zone name, floor length and width, number of people, equipment watts, lighting watts, external shading data, and specific roof, wall, partition, floor, and glass data.

Program Output

The CHVAC program provides eleven types of reports,which can be selectively previewed onscreen or printed as desired. CHVAC supports all printers that work with Windows and numerous full color reports are available.The reports are: General Project Data, Air Handler Input Data, Zone Input Data, Detailed Project Zone Loads, Air System Zone Summary, Total Building, Air System, and Zone Load Profiles, Air System Total Load Summary, Air System Psychrometric Analysis, Overall Building Envelope Report, Pie Charts, Bar Graphs, and the Total Building Load Summary. Air system summary data can be exported to your favorite spreadsheet.

 

COMPUTER PROGRAMS HVAC

TRACE ® 700

The TRACE Load ® 700 program is a commercial Heating, Ventilation and Air Conditioning software platform developed by Trane’s CDS Group.

The Load phase of the program computes the peak sensible and latent zone loads, as well as the block sensible and latent loads for the building. In addition, the hourly sensible and latent loads, including weather-dependent loads, are calculated for each zone, based on the weather library. The building heating/cooling load calculations, used in the load phase of the program for annual energy consumption analysis, are of sufficient detail to permit the evaluation of the effect of building data such as orientation, size, shape and mass, heat transfer characteristics of air and moisture, as well as hourly climatic data. The Design phase of the TRACE program calculates the design supply air temperatures, heating and cooling capacities, and supply air quantities given the peak load files generated by the Load phase. For applications where the building design parameters are known, you can override the calculation of these values using optional entries to the System phase. This gives you the ability to simulate existing buildings
with installed equipment that may not be sized according to the loads calculated in the program’s Load Phase.

Beyond this, the calculations used to simulate the operation of the building and its service systems through a full-year operating period, are of sufficient detail to permit the evaluation of the effect of system design, climatic factors, operational characteristics and mechanical equipment operating characteristics on annual energy usage. Manufacturers’ data is used in the program for the simulation of all systems and equipment. The calculation procedures used in TRACE are based upon 8,760 hours of operation of the building and its service system. These procedures use techniques recommended in the appropriate ASHRAE publications or produce results that are consistent with such recommended techniques. The following are the program features:

Project Navigator View
  • Organizes entries by task to lead you through the modeling process
  • Displays the status of each modeling step
  • Accommodates up to 4 alternatives per project
Project Tree View
  • Organizes all rooms, systems, and plants in a hierarchical list
  • Displays all information about a system, zone, or room on 1 screen
  • Supports cut, copy, and paste to save entry time
Component Tree
  • Displays cooling set point for every room in the project on 1 screen
  • Makes it easy to check and edit your work

Task-oriented display guides you through the modeling process as follows:

Select weather information

  • Provides both design and typical weather data by location
  • Choose from 400 climate locations
  • Import standard weather files for a full-year (8760) analysis

Create rooms

  • Describe the construction, airflows, thermostat settings, heat sources, and schedules by room

Create airside systems

  • Choose from more than 30 methods of air distribution
  • Add energy recovery, economizers, and dedicated ventilation/makeup air

Assign rooms to systems

  • Create thermal zones and assign them to systems
  • Determine airflows, coil loads, and fan sizes for each airside system

If the only requirement is to calculate the cooling and/or heating loads and the project does not require energy analysis and economic evaluation, it is recommended that the Program Load ® 700 be utilized instead of Full TRACE 700.The only difference is that Trace Load ® 700 users only have access to the Load Design section (from Project Information to Assign Rooms to Systems). Full TRACE 700 users will have full access to the Load, Energy and Economic sections.

The advantage of using only Trace Load ® 700 is that all the added features and capabilities (applicable to load design) in full TRACE 700 program are also available to the Trace Load ® 700 users. Also, same file extensions and libraries will enable users of both programs to transfer archived files back and forth without any additional steps needed.

 

Finite Element Analysis FEA Terms and Definitions (A to Z) Part-6 (Final)

Finite Element Analysis FEA Terms and Definitions (A to Z) Part-5

(A to Z) of Finite Element Analysis

 

T

TEMPERATURE CONTOUR PLOTS
A plot showing contour lines connecting points of equal temperature.
TETRAHEDRON TETRAHEDRAL ELEMENT
A three dimensional four sided solid element with triangular faces.
THERMAL CAPACITY
The material property defining the thermal inertia of a material. It relates the rate of change of temperature with time to heat flux.
THERMAL CONDUCTIVITY
The material property relating temperature gradient to heat flux.
THERMAL LOADS
The equivalent loads on a structure arising from thermal strains. These in turn arise from a temperature change.
THERMAL STRAINS
The components of strain arising from a change in temperature.
THERMAL STRESS ANALYSIS
The computation of stresses and displacements due to change in temperature.
THIN SHELL ELEMENT THICK SHELL ELEMENT
In a shell element the geometry is very much thinner in one direction than the other two. It can then be assumed stresses can only vary linearly at most in the thickness direction. If the through thickness shear strains can be taken as zero then a thin shell model is formed. This uses the Kirchoff shell theory If the transverse shear strains are not ignored then a thick shell model is formed. This uses the Mindlin shell theory. For the finite element method the thick shell theory generates the most reliable form of shell elements. There are two forms of such elements, the Mindlin shell and the Semi -Loof shell.
TIMEDOMAIN
The structures forcing function and the consequent response is defined in terms of time histories. The Fourier transform of the time domain gives the corresponding quantity in the frequency domain.
TRACE OF THE MATRIX
The sum of the leading diagonal terms of the matrix.
TRANSFINITE MAPPING
A systematic method for generating element shape functions for irregular node distributions on an element.
TRANSFORMATION METHOD
Solution techniques that transform coordinate and force systems to generate a simpler form of solution. The eigenvectors can be used to transform coupled dynamic equations to a series of single degree of freedom equations.
TRANSIENT FORCE
A forcing function that varies for a short period of time and then settles to a constant value.
TRANSIENT RESPONSE
The component of the system response that does not repeat itself regularly with time.
TRANSITION ELEMENT
Special elements that have sides with different numbers of nodes. They are used to couple elements with different orders of interpolation, typically a transition element with two nodes on one edge and three on another is used to couple a 4 -node quad to an 8 -node quad.
TRANSIENT HEAT TRANSFER
Heat transfer problems in which temperature distribution varies as a function of time.
TRIANGULAR ELEMENTS
Two dimensional or surface elements that have three edges.
TRUSS ELEMENT
A one dimensional line element defined by two nodes resisting only axial loads.

 

U

ULTIMATE STRESS
The failure stress (or equivalent stress) for the material.
UNDAMPED NATURAL FREQUENCY
The square root of the ratio of the stiffness to the mass (the square root of the eigenvalue). It is the frequency at which an undamped system vibrates naturally. A system with n degrees of freedom has n natural frequencies.
UNDER DAMPED SYSTEM
A system which has an equation of motion where the damping is less than critical. It has an oscillatory impulse response.
UNIT MATRIX
A diagonal matrix with unit values down the diagonal.
UPDATED LAGRANGIAN TOTAL LAGRANGIAN
The updated Lagrangian coordinate system is one where the stress directions are referred to the last known equilibrium state. The total Lagrangian coordinate system is one where the stress directions are referred to the initial geometry.
UPWINDING IN FLUIDS
A special form of weighting function used in viscous flow problems (solution to the NavierStokes equations) used in the weighted residual method to bias the results in the direction of the flow.

[AdtoAppearHere]

 

V

VARIABLE BANDWIDTH (SKYLINE)
A sparse matrix where the bandwidth is not constant. Some times called a skyline matrix.
VELOCITY
The first time derivative of the displacement.
VIRTUAL CRACK EXTENSION CRACK PROPAGATION
A technique for calculating the energy that would be released if a crack increased in size. This gives the energy release rate which can be compared to the critical energy release (a material property) to decide if a crack will propagate.
VIRTUAL DISPLACEMENTS
An arbitrary imaginary change of the system configuration consistent with its constraints.
VIRTUAL WORK VIRTUAL DISPLACEMENTS VIRTUAL FORCES
Techniques for using work arguments to establish equilibrium equations from compatibility equations (virtual displacements) and to establish compatibility equations from equilibrium (virtual forces).
VISCOUS DAMPING
The damping is viscous when the damping force is proportional to the velocity.
VISCOUS DAMPING MATRIX
The matrix relating a set of velocities to their corresponding velocities
VOLUME DISTORTION VOLUMETRIC DISTORTION
The distortion measured by the determinant of the Jacobian matrix, det j.
VON MISES STRESS
An “averaged” stress value calculated by adding the squares of the 3 component stresses (X, Y and Z directions) and taking the square root of their sums. This value allows for a quick method to locate probable problem areas with one plot.
VON MISES EQUIVALENT STRESS TRESCA EQUIVALENT STRESS
Equivalent stress measures to represent the maximum shear stress in a material. These are used to characterize flow failures (e.g. plasticity and creep). From test results the VonMises form seems more accurate but the Tresca form is easier to handle.

 

W

WAVE PROPAGATION
The dynamic calculation involving the prediction of the history of stress and pressure waves in solids and fluids.
WAVEFRONT (FRONT)
The wavefront of a symmetric matrix is the maximum number of active nodes at any time during a frontal solution process. It is a measure of the time required to factorise the equations in a frontal solution. It is minimized be element renumbering.
WEIGHTED RESIDUALS
A technique for transforming a set of partial differential equations to a set of simultaneous equations so that the solution to the simultaneous equations satisfy the partial differential equations in a mean sense. The form used in the finite element method is the Galerkin process. This leads to identical equations to those from virtual work arguments.
WHIRLING STABILITY
The stability of rotating systems where centrifugal and Coriolis are also present.
WHITE NOISE
White noise has a constant spectral density for all frequencies.
WILSON THETA METHOD
An implicit solution method for integrating second order equations of motion. It can be made unconditionally stable.
WORD LENGTH
Within a digital computer a number is only held to a finite number of significant figures. A 32bit (single precision) word has about 7 significant figures. A 64bit (double precision) word has about 13 significant figures. All finite element calculations should be conducted in double precision.

 

Y

YOUNG’S MODULUS
The material property relating a uniaxial stress to the corresponding strain.

 

Z

ZERO ENERGY MODES ZERO STIFFNESS MODES
Non-zero patterns of displacements that have no energy associated with them. No forces are required to generate such modes, Rigid body motions are zero energy modes. Buckling modes at their buckling loads are zero energy modes. If the elements are not fully integrated they will have zero energy displacement modes. If a structure has one or more zero energy modes then the matrix is singular.

[AdtoAppearHere]

 

REFERENCES

http://www.cae.tntech.edu/~chriswilson/FEA/ANSYS/

www.nafems.org

Finite Element Analysis FEA Terms and Definitions (A to Z) Part-5

Finite Element Analysis FEA Terms and Definitions (A to Z) Part-4

(A to Z) of Finite Element Analysis

 

O

OPTIMAL SAMPLING POINTS
The minimum number of Gauss points required to integrate an element matrix. Also the Gauss points at which the stresses are most accurate (see reduced Gauss points).
OVER DAMPED SYSTEM
A system which has an equation of motion where the damping is greater than critical. It has an exponentially decaying, non-oscillatory impulse response.
OVERSTIFF SOLUTIONS
Lower bound solutions. These are associated with the assumed displacement method.

P

PARAMETRIC STUDIES PILOT STUDIES
Initial studies conducted on small -simplified models to determine the important parameters in the solution of a problem. These are often used to determine the basic mesh density required.
PARTICIPATION FACTOR
The fraction of the mass that is active for a given mode with a given distribution of dynamic loads. Often this is only defined for the specific load case of inertia (seismic) loads.

PATCH TEST
A test to prove that a mesh of distorted elements can represent constant stress situations and strain free rigid body motions (i.e. the mesh convergence requirements) exactly.
PERIODIC RESPONSE FORCE
A response (force) that regularly repeats itself exactly.
PHASE ANGLE
The ratio of the in phase component of a signal to its out of phase component gives the tangent of the phase angle of the signal relative to some reference.
PLANE STRAIN PLANE STRESS
A two dimensional analysis is plane stress if the stress in the third direction is assumed zero. This is valid if the dimension of the body in this direction is very small, e.g. a thin plate. A two dimensional analysis is plane strain if the strain in the third direction is assumed zero. This is valid if the dimension of the body in this direction is very large, e.g. a cross- sectional slice of a long body.
PLATE BENDING ELEMENTS
Two-dimensional shell elements where the in plane behavior of the element is ignored. Only the out of plane bending is considered.
POISSONS RATIO
The material property in Hooke s law relating strain in one direction arising from a stress in a perpendicular direction to this.
POST ANALYSIS CHECKS
Checks that can be made on the results after the analysis. For a stress analysis these could include how well stress free boundary conditions have been satisfied or how continuous stresses are across elements.
POST-PROCESSING
The interrogation of the results after the analysis phase. This is usually done with a combination of graphics and numerics.

banner_05

POTENTIAL ENERGY
The energy associated with the static behavior of a system. For a structure this is the strain energy.
POTENTIAL FLOW
Fluid flow problems where the flow can be represented by a scalar potential function.
POWER METHOD
A method for finding the lowest or the highest eigenvalue of a system.
PRANDTL-REUSS EQUATIONS
The equations relating an increment of stress to an increment of plastic strain for a metal undergoing plastic flow.
PREPROCESSING
The process of preparing finite element input data involving model creation, mesh generation,material definition, and load and boundary condition application.
PRIMARY COMPONENT

Those parts of the structure that are of direct interest for the analysis. Other parts are secondary components.
PRINCIPAL CURVATURE
The maximum and minimum radii of curvature at a point.
PRINCIPAL STRESSES
The maximum direct stress values at a point. They are the eigenvalues of the stress tensor.
PROFILE
The profile of a symmetric matrix is the sum of the number of terms in the lower (or upper) triangle of the matrix ignoring the leading zeros in each row. Embedded zeros are included in the count. It gives a measure of the work required to factorize the matrix when using the Cholesky solution. Node renumbering minimizes it.
PROPORTIONAL DAMPING
A damping matrix that is a linear combination of the mass and stiffness matrices. The eigenvectors of a proportionally damped system are identical to those of the undamped system.
P-METHOD
A method of finite element analysis that uses P- convergence to iteratively minimize the error of analysis.
QR METHOD
A technique for finding eigenvalues. This is currently the most stable method for finding eigenvalues but it is restricted in the size of problem that it can solve.
RANDOM VIBRATIONS
The applied loading is only known in terms of its statistical properties. The loading is nondeterministic in that its value is not known exactly at any time but its mean, mean square, variance and other statistical quantities are known.

R

RANK DEFICIENCY
A measure of how singular a matrix is.
RAYLEIGH DAMPING
Damping that is proportional to a linear combination of the stiffness and mass. This assumption has no physical basis but it is mathematically convenient to approximate low damping in this way when exact damping values are not known.
RAYLELGH QUOTIENT
The ratio of stiffness times displacement squared (2*strain energy) to mass times
displacement squared. The minimum values of the Rayleigh quotient are the eigenvalues.
REACTION FORCES
The forces generated at support points when a structure is loaded.
REFERENCE TEMPERATURE
The reference temperature defines the temperature at which strain in the design does not
result from thermal expansion or contraction. For many situations, reference temperature
is adequately defined as room temperature. Define reference te mperature in the
properties of an environment.
RECEPTANCE

The ratio of the steady state displacement response to the value of the forcing function for
a sinusoidal excitation. It is the same as the dynamic flexibility.
REDUCED INTEGRATION
If an element requires an l*m*n Gauss rule to integrate the element matrix exactly then (l-1)*(m-1)*(n-1) is the reduced integration rule. For many elements the stresses are most
accurate at the reduced integration points. For some elements the matrices are best
evaluated by use of the reduced integration points. Use of reduced integration for
integrating the elements can lead to zero energy and hour glassing modes.
RESPONSE SPECTRUM METHOD
A method for characterizing a dynamic transient forcing function and the associated
solution technique. It is used for seismic and shock type loads.
RESTARTS CHECKPOINTS
The process whereby an analysis can be stopped part way through and the analysis restarted at a later time.
RIGID BODY DEFORMATIONS
A non-zero displacement pattern that h as zero strain energy associate with it.
RIGID BODY DISPLACEMENT
A non-zero displacement pattern that has zero strain energy associate with it.
RIGID BODY MODES
If a displaced shape does not give rise to any strain energy in the structure then this a rigid body mode. A general three-dimensional unsupported structure has 6 rigid body modes, 3 translation and 3 rotation.
RIGID LINKS RIGID OFFSETS
This is a connection between two non-coincident nodes assuming that the connection is infinitely stiff. This allows the degrees of freedom at one of the nodes (the slave node) to be deleted from the system. It is a form of multi-point constraint.
ROUNDOFF ERROR
Computers have a fixed word length and hence only hold numbers to a certain number of significant figures. If two close numbers are subtracted one from another then the result loses the first set of significant figures and hence loses accuracy. This is round off error.
ROW VECTOR ROW MATRIX
A 1xn matrix written as a horizontal string of numbers. It is the transpose of a column vector.

S

SCALARS VECTORS
Quantities that have no direction associated with them, e.g. temperatures. Scalar problems only have one degree of freedom at a node. Vector quantities have a direction associated with them, e.g. displacements. Vector problems have more than one degree of freedom at a node.
SECANT STIFFNESS
The stiffness defined by the slope of the line from the origin to the current point of interest on a load/deflection curve.
SECONDARY COMPONENTS

Components of a structure not of direct interest but they may have some influence of the behavior of the part of the structure that is of interest (the primary component) and have to be included in the analysis in some approximate form.
SEEPAGE FLOW
Flows in porous materials
SEISMIC ANALYSIS
The calculation of the dynamic displacement and stress response arising from earthquake excitations.
SELECTED REDUCED INTEGRATION
A form of Gaussian quadrature where different sets of Gauss points are used for different strain components.
SELF ADJOINT EQUATIONS
A form of matrix products that preserves symmetry of equations. The product A*B*A(transpose) is self -adjoint if the matrix B is symmetric. The result of the product will be symmetric for any form of A that is of a size compatible with B. This form o f equation occurs regularly within the finite element method. Typically it means that for a structural analysis the stiffness (and mass) matrices for any element or element assembly will be
symmetric.
SELF EQUILIBRATING LOADS
A load set is self -equilibrating if all of its resultants are zero. Both translation and moment resultants are zero.
SEMI-LOOF ELEMENT
A form of thick shell element.
SHAKEDOWN
If a structure is loaded cyclically and initially undergoes some plastic deformation then it is said to shakedown if the behavior is entirely elastic after a small number of load cycles.
SIMPSONS RULE
A method for numerically integrating a function.
SIMULTANEOUS VECTOR ITERATION
A method for finding the first few eigenvalues and eigenvectors of a finite element system. This is also known as subspace vector iteration.
SINGLE DEGREE OF FREEDOM
The system is defined by a single force/displacement equation.
SINGLE POINT CONSTRAINT
Where the constraint is unique to a single node point.
SINGULAR MATRIX
A square matrix that cannot be inverted.
SKEW DISTORTION (ANGULAR DISTORTION)
A measure of the angular distortion arising between two vectors that are at right angles in the basis space when these are mapped to the real coordinate space. If this angle approaches zero the element becomes ill-conditioned.
SOLID ELEMENTS

Three dimensional continuum elements.
SOLUTION DIAGNOSTICS
Messages that are generated as the finite element solution progresses. These should always be checked for relevance but the are often only provided for information purposes
SOLUTION EFFICIENCY
A comparative measure between two solutions of a given problem defining which is the ‘best’. The measures can include accuracy, time of solution, memory requirements and disc storage space.
SPARSE MATRIX METHODS
Solution methods that exploit the sparse nature of finite element equations. Such methods include the frontal solution and Cholesky (skyline) factorization for direct solutions, conjugate gradient methods for iterative solutions and the Lanczos method and subspace iteration (simultaneous vector iteration) for eigenvalue solutions.
SPECTRAL DENSITY
The Fourier transform of the correlation function. In random vibrations it gives a measure of the significant frequency content in a system. White noise has a constant spectral density for all frequencies.
SPLINE CURVES
A curve fitting technique that preserves zero, first and second derivative continuity across segment boundaries.
SPURIOUS CRACKS
Cracks that appear in a mesh when the elements are not correctly connected together. This is usually an error in the mesh generation process.
STATIC ANALYSIS
Analysis of stresses and displacements in a structure when the applied loads do not vary with time.
STATICALLY DETERMINATE STRUCTURE
A structure where all of the unknowns can be found from equilibrium considerations alone.
STATICALLY EQUIVALENT LOADS
Equivalent nodal loads that have the same equilibrium resultants as the applied loads but do not necessarily do the same work as the applied loads.
STATICALLY INDETERMINATE STRUCTURE REDUNDANT
A structure where all of the unknowns can not be found from equilibrium considerations alone. The compatibility equations must also be used. In this case the structure is said to be redundant.
STATIONARY RANDOM EXCITATION
A force or response that is random but its statistical characteristics do not vary with time.
STEADY-STATE HEAT TRANSFER
Determination of the temperature distribution of a mechanical part having reached thermal equilibrium with the environmental conditions. There are no time varying changes in the resulting temperatures.
STEADY STATE RESPONSE

The response of the system to a periodic forcing function when all of the transient components of the response have become insignificant.
STEP-BY-STEP INTEGRATION
Methods of numerically integrating time varying equations of motion. These methods can be either explicit or implicit.
STIFFNESS
A set of values which represent the rigidity or softness of a particular element. Stiffness is determined by material type and geometry.
STIFFNESS MATRIX
The parameter(s) that relate the displacement(s) to the force(s). For a discrete parameter multi degree of freedom model this is usually given as a stiffness matrix.
STRAIN
A dimensionless quantity calculated as the ratio of deformation to the original size of the body.
STRAIN ENERGY
The energy stored in the system by the stiffness when it is displaced from its equilibrium position.
STRESS
The intensity of internal forces in a body (force per unit area) acting on a plane within the material of the body is called the stress on that plane.
STRESS ANALYSIS
The computation of stresses and displacements due to applied loads. The analysis may be elastic, inelastic, time dependent or dynamic.
STRESS AVERAGING STRESS SMOOTHING
The process of filtering the raw finite element stress results to obtain the most realistic estimates of the true state of stress.
STRESS CONCENTRATION
A local area of the structure where the stresses are significantly higher than the general stress level. A fine mesh of elements is required in such regions if accurate estimates of the stress concentration values are required.
STRESS CONTOUR PLOT
A plot of a stress component by a series of color filled contours representing regions of equal stress.
STRESS DISCONTINUITIES STRESS ERROR ESTIMATES
Lines along which the stresses are discontinuous. If the geometry or loading changes abruptly along a line then the true stress can be discontinuous. In a finite element solution the element assumptions means that the stresses will generally be discontinuous across element boundaries. The degree of discontinuity can then be used to form an estimate of the error in the stress within the finite element calculation.
STRESS EXTRAPOLATION
The process of taking the stress results at the optimum sampling points for an element and extrapolating these to the element node points.
STRESS INTENSITY FACTORS

A measure of the importance of the stress at a sharp crack tip (where the actual stress values will be infinite) used to estimate if the crack will propagate.

STRESS VECTOR STRESS TENSOR STRAIN VECTOR STRAIN TENSOR
The stress (strain) vector is the components of stress (strain) written as a column vector. For a general three dimensional body this is a (6×1) matrix. The components of stress (strain) written in tensor form. For a general three dimensional body this forms a (3×3) matrix with the direct terms down the diagonal and the shear terms as the off-diagonals.
STRESS-STRAIN LAW
The material property behavior relating stress to strain. For a linear behavior this is Hookes law (linear elasticity). For elastic plastic behavior it is a combination of Hookes law and the Prandtl-Reuss equations.
SUBSPACE VECTOR ITERATION
A method for finding the first few eigenvalues and eigenvectors of a finite element system. This is also known as simultaneous vector iteration.
SUBSTRUCTURING
An efficient way of solving large finite element analysis problems by breaking the model into several parts or substructures, analyzing each one individually, and then combining them for the final results.
SUBSTRUCTURING SUPER ELEMENT METHOD
Substructuring is a form of equation solution method where the structure is split into a series of smaller structures -the substructures. These are solved to eliminate the internal freedoms and the complete problem solved by only assembling the freedoms on the common boundaries between the substructures. The intermediate solution where the internal freedoms of a substructure have been eliminated gives the super element matrix
for the substructure.
SURFACE MODELING
The geometric modeling technique in which the model is created in terms of its surfaces only without any volume definition.

[AdtoAppearHere]

 

Finite Element Analysis FEA Terms and Definitions (A to Z) Part-6 (Final)

REFERENCES

http://www.cae.tntech.edu/~chriswilson/FEA/ANSYS/

www.nafems.org

Subscribe and receive the following...

  • Blog and News updates
  • Forum Discussions
  • Tutorial alerts