Second law of Thermodynamics

Second law of Thermodynamics

There are two classical statements of the second law of thermodynamics

1) Kelvin – Planck statement

2) Clausius statement

Kelvin – Planck statement

“It is impossible to construct a device which will operate in a cycle & produce no effect other than the raising of a weight and the exchange of heat with a single reservoir”

i.e., it is impossible to construct an engine which will operate in a cycle will produce no effect other than the transfer of heat from a single thermal reservoir and the performance of an equivalent amount of work”.

No actual or ideal engine operating in cycles can convert into work all the heat supplied to the working substance, it must discharge some heat into a naturally accessible sink because of this aspect and the second law is often referred as the law of degradation of energy.

The statement implies that it is impossible to construct a heat engine that working in a cyclic process can absorb an amount of heat from a high temperature reservoir and can do an equivalent amount of work.  In other words it is not possible to construct a heat engine having thermal efficiency of 100 percent.

Clausius Statement 

It is impossible to construct a heat pump which operating in a cycle will produce no effect other than the transfer of heat from a low temperature thermal reservoir to a higher temperature thermal reservoir.

That is in order to transfer heat from a low temperature thermal reservoir to a high temperature thermal reservoir work must be done on the system by the surroundings.

Although the Kelvin – Planck and Clausius statements appear to be different, they are really equivalent in the sense that a violation of one statement involves violation of the other.

Although the Kelvin – Planck and Clausius statements appear to be different, they are really equivalent in the sense that a violation of one statement involves violation of the other.

Thermodynamic System

A Thermodynamic system is defined as a quantity of matter or a region in space upon which attention is concentrated in the analysis of a problem. Everything external to the system is called the surrounding or environment. The system is separated from the surrounding by the system boundary. Boundary may be either fixed or moving.  A system and its surrounding together comprise a universe.

Open System: The open system is one in which matter crosses the boundary of the system. There may be energy transfer also. Most of the engineering devices are generally open systems.

 Ex: An air compressor in which air enters at low pressure and leave at high pressure and there is energy transfer across the system boundary.

Closed System: A closed system is a system of fixed mass. There is no mass transfer across the system boundary.  

Ex: A certain quantity of fluid in a cylinder bounded by a piston constitutes a closed system.

Isolated System:  The isolated system is one in which there is no interaction between the system and surrounding. It is of the fixed mass and energy and there is no mass or energy transfer across the system boundary.

Homogeneous and Heterogeneous system:

A quantity of matter homogeneous throughout in chemical composition and physical structure is called a phase. Every substance can exist in any one of the three phases viz. Solid, Liquid or  gas. 

A system consisting of a single phase is called a homogeneous system while a system consisting of more than one phase is known as a heterogeneous system.

Fundamental Concepts of Fluid Mechanics

·         Mechanics : Deals with action of forces on bodies at rest or in motion.

·         State of rest and Motion: They are relative and depend on the frame of reference.  If the position with reference to frame of reference is fixed with time, then the body is said to be in a state of rest.  Otherwise, it is said to be in a state of motion.

·         Scalar and heater quantities: Quantities which require only magnitude to represent them are called scalar quantities.  Quantities which acquire magnitudes and direction to represent them are called vector quantities.

Eg: Mass, time internal, Distance traveled à Scalars

            Weight, Displacement, Velocity à Vectors

·         Velocity and Speed: Rate of displacement is called velocity and Rate and distance traveled is called Speed.

Unit: m/s

·         Acceleration: Rate of change of velocity is called acceleration. Negative acceleration is called retardation.

·         Momentum: The capacity of a body to impart motion to other bodies is called momentum.

The momentum of a moving body is measured by the product of mass and velocity the moving body

Momentum = Mass x Velocity

Unit: Kg m/s

·       Newton’s first law of motion: Every body continues to be in its state of rest or uniform motion unless compelled by an external agency.

·       Inertia: It is the inherent property the body to retain its state of rest or uniform motion.

·       Force: It is an external agency which overcomes or tends to overcome the inertia of a body.

·       Newton’s second law of motion: The rate of change of momentum of a body is directly proportional to the magnitudes of the applied force and takes place in the direction of the applied force.

·       Mass:   Measure of amount of matter contained by the body it is a scale of quantity.

                        Unit: Kg.   

                                                                   

·       Weight:  Gravitational force on the body. It is a vector quantity.

                        F = ma

                        W = mg

                        Unit: newton (N)                    g = 9.81 m/s²

·       Volume:  Measure of space occupied by the body.

                        Unit: m³

                                1 m³ = 1000 litres

·       Work:  Work done = Force x Displacement  à Linear motion.

                  Work done = Torques x Angular displacement  à Rotatory motion.

Unit: Nm or J

·       Energy:  Capacity of doing work is called energy.

Unit: Nm or J

FLUID MECHANICS

·       Matter: Anything which possess mass and requires space to occupy is called matter.

·       States of matter:

Matter can exist in the following states

¨      Solid state.

¨      Fluid state.

¨      Solid state: In case of solids intermolecular force is very large and hence molecules are not free to move. Solids exhibit definite shape and volume. Solids undergo certain amount of deformation and then attain state of equilibrium when subjected to tensile, compressive and shear forces.

¨      Fluid State: Liquids and gases together are called fluids. Incase of liquids Intermolecular force is comparatively small. Therefore liquids exhibit definite volume. But they assume the shape of the container

            Liquids offer very little resistance against tensile force.  Liquids offer maximum resistance against compressive forces. Therefore, liquids are also called incompressible fluids. Liquids undergo continuous or prolonged angular deformation or shear strain when subjected to tangential force or shear force. This property of the liquid is called flow of liquid. Any substance which exhibits the property of flow is called fluid. Therefore liquids are considered as fluids.

            In case of gases intermolecular force is very small. Therefore the molecules are free to move along any direction. Therefore gases will occupy or assume the shape as well as the volume of the container.

         Gases offer little resistance against compressive forces. Therefore gases are called compressible fluids. When subjected to shear force gases undergo continuous or prolonged angular deformation or shear strain. This property of gas is called flow of gases. Any substance which exhibits the property of flow is called fluid. Therefore gases are considered as fluids.

GASEOUS FUELS

Natural gas. The main constituents of natural gas are methane (CH4) and ethane (C2H6).

It has calorific value nearly 21000 kJ/m3. Natural gas is used alternately or simultaneously with oil for internal combustion engines.

Coal gas. Mainly consists of hydrogen, carbon monoxide and hydrocarbons. It is prepared by carbonisation of coal. It finds its use in boilers and sometimes used for commercial purposes.

Coke-oven gas. It is obtained during the production of coke by heating the bituminous coal. The volatile content of coal is driven off by heating and major portion of this gas is utilised in heating the ovens. This gas must be thoroughly filtered before using in gas engines.

Blast furnance gas. It is obtained from smelting operation in which air is forced through layers of coke and iron ore, the example being that of pig iron manufacture where this gas is produced as by product and contains about 20% carbon monoxide (CO). After filtering it may be blended with richer gas or used in gas engines directly. The heating value of this gas is very low.

Producer gas. It results from the partial oxidation of coal, coke or peat when they are burnt with an insufficient quantity of air. It is produced in specially designed retorts. It has low heating value and in general is suitable for large installations. It is also used in steel industry for firing open hearth furnaces.

Water or illuminating gas. It is produced by blowing steam into white hot coke or coal.

The decomposition of steam takes place liberating free hydrogen, and oxygen in the steam combines with carbon to form carbon monoxide according to the reaction.

The gas composition varies as the hydrogen content if the coal is used.

Sewer gas. It is obtained from sewage disposal vats in which fermentation and decay occur. It consists of mainly marsh gas (CH4) and is collected at large disposal plants. It works as a fuel for gas engines which in turn drive the plant pumps and agitators. Gaseous fuels are becoming popular because of following advantages they possess.

Advantages :

1. Better control of combustion.

2. Much less excess air is needed for complete combustion.

3. Economy in fuel and more efficiency of furnace operation.

4. Easy maintenance of oxidizing or reducing atmosphere.

5. Cleanliness.

6. No problem of storage if the supply is available from public supply line.

7. The distribution of gaseous fuels even over a wide area is easy through the pipe lines and

as such handling of the fuel is altogether eliminated.

8. Gaseous fuels give economy of heat and produce higher temperatures (as they can be preheated in regenerative furnances and thus heat from hot flue gases can be recovered).

LIQUID FUELS

The chief source of liquid fuels is petroleum which is obtained from wells under the earth’s crust. These fuels have proved more advantageous in comparison to sold fuels in the following respects.

Advantages :

1. Require less space for storage.

2. Higher calorific value.

3. Easy control of consumption.

4. Staff economy.

5. Absence of danger from spontaneous combustion.

6. Easy handling and transportation.

7. Cleanliness.

8. No ash problem.

9. Non-deterioration of the oil in storage.

Petroleum. There are different opinions regarding the origin of petroleum. However, now it is accepted that petroleum has originated probably from organic matter like fish and plant life etc., by bacterial action or by their distillation under pressure and heat. It consists of a mixture of gases, liquids and solid hydrocarbons with small amounts of nitrogen and sulphur compounds. In India, the main sources of Petroleum are Assam and Gujarat. Heavy fuel oil or crude oil is imported and then refined at different refineries. The refining of crude oil supplies the most important product called petrol. Petrol can also be made by polymerization of refinery gases.

Other liquid fuels are kerosene, fuels oils, colloidal fuels and alcohol.

SOLID FUELS

Coal. Its main constituents are carbon, hydrogen, oxygen, nitrogen, sulphur, moisture and ash. Coal passes through different stages during its formation from vegetation. These stages are enumerated and discussed below :

Plant debris—Peat—Lignite—Brown coal—sub-bituminous coal—Bituminous coal—Semibituminous coal—Semi-anthracite coal—Anthracite coal—Graphite.

Peat. It is the first stage in the formation of coal from wood. It contains huge amount of moisture and therefore it is dried for about 1 to 2 months before it is put to use. It is used as a domestic fuel in Europe and for power generation in Russia. In India it does not come in the categories of good fuels.

Lignites and brown coals. These are intermediate stages between peat and coal. They have a woody or often a clay like appearance associated with high moisture, high ash and low heat contents. Lignites are usually amorphous in character and impose transport difficulties as they break easily. They burn with a smoky flame. Some of this type are suitable for local use only.

Bituminous coal. It burns with long yellow and smoky flames and has high percentages of volatile matter. The average calorific value of bituminous coal is about 31350 kJ/kg. It may be of two types, namely caking or noncaking.

Semi-bituminous coal. It is softer than the anthracite. It burns with a very small amount of smoke. It contains 15 to 20 per cent volatile matter and has a tendency to break into small sizes during storage or transportation.

Semi-anthracite. It has less fixed carbon and less lustre as compared to true anthracite and gives out longer and more luminous flames when burnt.

Wood charcoal. It is obtained by destructive distillation of wood. During the process the volatile matter and water are expelled. The physical properties of the residue (charcoal), however depends upon the rate of heating and temperature.

Coke. It consists of carbon, mineral matter with about 2% sulphur and small quantities of hydrogen, nitrogen and phosphorus. It is solid residue left after the destructive distillation of certain kinds of coals. It is smokeless and clear fuel and can be produced by several processes. It is mainly used in blast furnace to produce heat and at the same time to reduce the iron ore.

Briquettes. These are prepared from fine coal or coke by compressing the material under high pressure.

Anthracite. It is very hard coal and has a shining black lustre. It ignites slowly unless the furnace temperature is high. It is non-caking and has high percentage of fixed carbon. It burns either with very short blue flames or without flames. The calorific value of this fuel is high to the tune of 35500 kJ/kg and as such is very suitable for steam generation.

Reversibility and Irreversibility

If 100% efficiency is unattainable, what is the max possible efficiency which can be attained and what factors promote the attainment of this max value? In trying to answer these questions, thermodynamics has invented & used the concept of reversibility, absolute temperature and entropy.

Reversible Process:

-for a system is defined as a process which once having taken place, can be reversed and leaves no change in either the system or surroundings. Only ideal processes can do this and restore both system and surroundings to their initial states. Hence an ideal process must be a reversible process.

No real process is truly reversible but some processes may approach reversibility, to a close approximation.

Example:

1) Frictionless relative motion

2) Extension and compression of a spring

3) Frictionless adiabatic expansion or compression of fluid.

4) Polytropic expansion or compression etc.,

The conditions for a process to be reversible may be given as follows:

i) There should be no friction

ii) There should be no heat transfer across finite temperature difference.

iii) Both the system and surrounding be stored to original state after the process is reversed.

Any process which is not reversible is irreversible.

Example: Movement of solids with friction, A flow of viscous fluid in pipes and passages mixing of two different substances, A combustion process.

Every quasistatic process is reversible, because a quasistatic process is of an infinite succession of equilibrium states.

Comparison between work and heat:

Similarities:

· Both are path functions and inexact differentials.

· Both are boundary phenomenon i.e., both are recognized at the boundaries of the system as they cross them.

· Both represent transient phenomenon; these energy interactions occur only when a system undergoes change of state i.e., both are associated with a process, not a state. Unlike properties, work or heat has no meaning at a state.

· A system possesses energy, but not work or heat.

· Concepts of heat and work are associated not with a ‘store’ but with a ‘process’.

Dissimilarities:

· Heat is energy interaction due to temperature difference only; work is by reasons other than temperature difference.

· In a stable system, there cannot be work transfer; however there is no restriction for the transfer of heat.

· The sole effect external to the system could be reduced to rise of a weight but in the case of a heat transfer other effects are also observed.

· Heat is a low grade energy whereas work is a high grade energy.

Classification of Flows

1. Steady and unsteady flows:

A flow is said to be steady if the properties (P) of the fluid and flow do not change with time (t) at any section or point in a fluid flow.

A flow is said to be unsteady if the properties (P) of the fluid and flow change with time (t) at any section or point in a fluid flow.

Eg: Flow observed at a dam section during rainy season, wherein, there will be lot of inflow with which the flow properties like depth, velocity etc.. will change at the dam section over a period of time representing it as unsteady flow.

2. Uniform and non-uniform flows:

A flow is said to be uniform if the properties (P) of the fluid and flow do not change (with direction) over a length of flow considered along the flow at any instant.

A flow is said to be non-uniform if the properties (P) of the fluid and flow change (with direction) over a length of flow considered along the flow at any instant.

Eg: Flow observed at any instant, at the dam section during rainy season, wherein, the flow varies from the top of the overflow section to the foot of the dam and the flow properties like depth, velocity etc., will change at the dam section at any instant between two sections, representing it as non-uniform flow.

3. One, two and three dimensional flows:

Flow is said to be one-dimensional if the properties vary only along one axis / direction and will be constant with respect to other two directions of a three-dimensional axis system.

Flow is said to be two-dimensional if the properties vary only along two axes / directions and will be constant with respect to other direction of a three-dimensional axis system.

Flow is said to be three-dimensional if the properties vary along all the axes / directions of a three-dimensional axis system.

4. Laminar and Turbulent flows:

When the flow occurs like sheets or laminates and the fluid elements flowing in a layer does not mix with other layers, then the flow is said to be laminar. The Reynolds number (Re) for the flow will be less than 2000.

When the flow velocity increases, the sheet like flow gets mixed up and the fluid elements mix with other layers there by causing turbulence. There will be eddy currents generated and flow reversal takes place. This flow is said to be Turbulent. The Reynolds number for the flow will be greater than 4000.

For flows with Reynolds number between 2000 to 4000 is said to be transition flow.

5. Compressible and Incompressible flows:

Flow is said to be Incompressible if the fluid density does not change (constant) along the flow direction and is Compressible if the fluid density varies along the flow direction

r = Constant (incompressible) and r ¹ Constant (compressible)

6. Rotational and Irrotational flows:

Flow is said to be Rotational if the fluid elements does not rotate about their own axis as they move along the flow and is Rotational if the fluid elements rotate along their axis as they move along the flow direction

KINEMATICS OF FLUID FLOW

Fluid kinematics refers to the features of a fluid in motion. It only deals with the motion of fluid particles without taking into account the forces causing the motion. Considerations of velocity, acceleration, flow rate, nature of flow and flow visualization are taken up under fluid kinematics.

A fluid motion can be analyzed by one of the two alternative approaches, called Lagrangian and Eulerian.

In Lagrangian approach, a particle or a fluid element is identified and followed during the course of its motion with time.

Difficulty in tracing a fluid particle (s) makes it nearly impossible to apply the Lagrangian approach. The alternative approach, called Eulerian approach consists of observing the fluid by setting up fixed stations (sections) in the flow field.

Motion of the fluid is specified by velocity components as functions of space and time. This is considerably easier than the previous approach and is followed in Fluid Mechanics.

Eg: Observing the variation of flow properties in a channel like velocity, depth etc, at a section.

CATIA

CATIA (Computer Aided Three-dimensional Interactive Application) is a multi-platform CAD/CAM/CAE commercial software suite developed by the French company Dassault Systemes and marketed worldwide by IBM. Written in the C++ programming language, CATIA is the cornerstone of the Dassault Systemes product lifecycle management software suite.

The software was created in the late 1970s and early 1980s to develop Dassault's Mirage fighter jet, then was adopted in the aerospace, automotive, shipbuilding, and other industries.

CATIA competes in the CAD/CAM/CAE market with Siemens NX, Pro/ENGINEER, Autodesk Inventor and SolidEdge.

History

CATIA started as an in-house development in 1977 by French aircraft manufacturer Avions Marcel Dassault, at that time customer of the CADAM CAD software.

Initially named CATI (Conception Assistée Tridimensionnelle Interactive — French for Interactive Aided Three-dimensional Design ) — it was renamed CATIA in 1981, when Dassault created a subsidiary to develop and sell the software, and signed a non-exclusive distribution agreement with IBM.

In 1984, the Boeing Company chose CATIA as its main 3D CAD tool, becoming its largest customer.

In 1988, CATIA version 3 was ported from mainframe computers to UNIX.

In 1990, General Dynamics Electric Boat Corp chose CATIA as its main 3D CAD tool, to design the U.S. Navy's Virginia class submarine.

In 1992, CADAM was purchased from IBM and the next year CATIA CADAM V4 was published. In 1996, it was ported from one to four Unix operating systems, including IBM AIX, Silicon Graphics IRIX, Sun Microsystems SunOS and Hewlett-Packard HP-UX.

In 1998, an entirely rewritten version of CATIA, CATIA V5 was released, with support for UNIX, Windows NT and Windows XP since 2001.

In 2008, Dassault announced and released CATIA V6. While the server can run on Microsoft Windows, Linux or AIX, client support for any operating system other than Microsoft Windows is dropped.

Features

Commonly referred to as a 3D Product Lifecycle Management software suite, CATIA supports multiple stages of product development (CAx), from conceptualization, design (CAD), manufacturing (CAM), and engineering (CAE).

CATIA can be customized via application programming interfaces (API). V4 can be adapted in the Fortran and C programming languages under an API called CAA. V5 can be adapted via the Visual Basic and C++ programming languages, an API called CAA2 or CAA V5 that is a component object model (COM)-like interface.

Although later versions of CATIA V4 implemented NURBS, V4 principally used piecewise polynomial surfaces. CATIA V4 uses a non-manifold solid engine.

Catia V5 features a parametric solid/surface-based package which uses NURBS as the core surface representation and has several workbenches that provide KBE support.

V5 can work with other applications, including Enovia, Smarteam, and various CAE Analysis applications.

Supported operating systems and platforms

CATIA V6 runs only on Microsoft Windows.

CATIA V5 runs on Microsoft Windows (both 32-bit and 64-bit), and as of Release 18 Service Pack 4 on Windows Vista 64. IBM AIX, Hewlett Packard HP-UX and Sun Microsystems Solaris are supported.

CATIA V4 is supported for those Unixes and IBM MVS and VM/CMS mainframe platforms up to release 1.7.

CATIA V3 and earlier run on the mainframe platforms.

Notable industries using CATIA

CATIA is widely used throughout the engineering industry, especially in the automotive and aerospace sectors. CATIA V4, CATIA V5, Pro/ENGINEER, NX (formerly Unigraphics), and SolidWorks are the dominant systems.

Aerospace

The Boeing Company used CATIA V3 to develop its 777 airliner, and is currently using CATIA V5 for the 787 series aircraft. They have employed the full range of Dassault Systemes' 3D PLM products — CATIA, DELMIA, and ENOVIA LCA — supplemented by Boeing developed applications.

European aerospace giant Airbus has been using CATIA since 2001.

Canadian aircraft maker Bombardier Aerospace has done all of its aircraft design on CATIA.

Automotive

Many automotive companies use CATIA to varying degrees, including BMW, Porsche, Daimler Chrysler, Audi, Volkswagen, Bentley Motors Limited, Volvo, Fiat, Benteler AG, PSA Peugeot Citroën, Renault, Toyota, Ford, Scania, Hyundai, Škoda Auto, Tesla Motors, Proton, Tata motors and Mahindra & Mahindra Limited. Goodyear uses it in making tires for automotive and aerospace and also uses a customized CATIA for its design and development. Many automotive companies use CATIA for car structures — door beams, IP supports, bumper beams, roof rails, side rails, body components — because CATIA is very good in surface creation and Computer representation of surfaces.

Shipbuilding

Dassault Systems has begun serving shipbuilders with CATIA V5 release 8, which includes special features useful to shipbuilders. GD Electric Boat used CATIA to design the latest fast attack submarine class for the United States Navy, the Virginia class. Northrop Grumman Newport News also used CATIA to design the Gerald R. Ford class of supercarriers for the US Navy.

Other

Architect Frank Gehry has used the software, through the C-Cubed Virtual Architecture company, now Virtual Build Team, to design his award-winning curvilinear buildings. His technology arm, Gehry Technologies, has been developing software based on CATIA V5 named Digital Project. Digital Project has been used to design buildings and has successfully completed a handful of projects.

CATIA V4 to V5/V6 Conversion

CATIA V5 and V6 can directly use the CATIA V4 models, but changes in the CATIA data structure requires data conversion from CATIA V4 to V5/V6. This is due to both a change in geometric kernel between CATIA V4 and CATIA V5, and changes in the CAD data structure between CATIA V5 and CATIA V6.

Dassault Systemes provides utilities to convert CATIA V4 data to CATIA V5 with a one-to-one mapping. Still, cases show that there can be issues in the data conversion from CATIA V4 to V5, from either differences in the geometric kernel between CATIA V4 and CATIA V5, or by the modelling methods employed by end users. Experiment results show that there can be data loss during the conversion (from 0% to 90%). The percentage loss can be minimized by using the appropriate pre-conversion clean-up, choosing the appropriate conversion options, and clean-up activities after conversion.

Engineering service providers have solutions, but mostly they are unique to a particular company and its processes / standard of modeling method. A common solution for 100% data conversion has yet to be devised. It is important to note that ANY change from one modeling kernel to another would cause similar problems; this issue is not unique to CATIA.

SolidWorks

SolidWorks is a 3D mechanical CAD (computer-aided design) program that runs on Microsoft Windows and was developed by Dassault Systèmes SolidWorks Corp., a subsidiary of Dassault Systèmes, S. A. (Vélizy, France). SolidWorks is currently used by over 3.4 million engineers and designers at more than 100,000 companies worldwide.

History

SolidWorks was introduced in 1995 as a competitor to CAD programs such as Pro/ENGINEER, I-DEAS, Unigraphics, and CATIA. SolidWorks Corporation was founded in 1993 by Jon Hirschtick, who recruited a team of engineers to build a company that developed 3D CAD software, with its headquarters at Concord, Massachusetts, and released its first product, SolidWorks 95, in 1995. In 1997 Dassault Systèmes, best known for its CATIA CAD software, acquired the company and currently owns 100% of its shares. SolidWorks was headed by John McEleney from 2001 to July 2007, and is now headed by Jeff Ray.

Modeling Methodology

SolidWorks is a parasolid-based solid modeler, and utilizes a parametric feature-based approach to create models and assemblies.

Parameters refer to constraints whose values determine the shape or geometry of the model or assembly. Parameters can be either numeric parameters, such as line lengths or circle diameters, or geometric parameters, such as tangent, parallel, concentric, horizontal or vertical, etc. Numeric parameters can be associated with each other through the use of relations, which allows them to capture design intent.

Design intent is how the creator of the part wants it to respond to changes and updates. For example, you would want the hole at the top of a beverage can to stay at the top surface, regardless of the height or size of the can. SolidWorks allows you to specify that the hole is a feature on the top surface, and will then honor your design intent no matter what the height you later gave to the can

Features refer to the building blocks of the part. They are the shapes and operations that construct the part. Shape-based features typically begin with a 2D or 3D sketch of shapes such as bosses, holes, slots, etc. This shape is then extruded or cut to add or remove material from the part. Operation-based features are not sketch-based, and include features such fillets, chamfers, shells, applying draft to the faces of a part, etc.

Building a model in SolidWorks usually starts with a 2D sketch (although 3D sketches are available for power users). The sketch consists of geometry such as points, lines, arcs, conics (except the hyperbola), and splines. Dimensions are added to the sketch to define the size and location of the geometry. Relations are used to define attributes such as tangency, parallelism, perpendicularity, and concentricity. The parametric nature of SolidWorks means that the dimensions and relations drive the geometry, not the other way around. The dimensions in the sketch can be controlled independently, or by relationships to other parameters inside or outside of the sketch.

SolidWorks pioneered the ability of a user to roll back through the history of the part in order to make changes, add additional features, or change the sequence in which operations are performed. Later feature-based solid modeling software has copied this idea.

In an assembly, the analog to sketch relations are mates. Just as sketch relations define conditions such as tangency, parallelism, and concentricity with respect to sketch geometry, assembly mates define equivalent relations with respect to the individual parts or components, allowing the easy construction of assemblies. SolidWorks also includes additional advanced mating features such as gear and cam follower mates, which allow modeled gear assemblies to accurately reproduce the rotational movement of an actual gear train.

Finally, drawings can be created either from parts or assemblies. Views are automatically generated from the solid model, and notes, dimensions and tolerances can then be easily added to the drawing as needed. The drawing module includes most paper sizes and standards (ANSI, ISO, DIN, GOST, JIS, BSI and GB).

Market

Solidworks Corp. has sold over a million licenses of Solidworks worldwide. The Sheffield Telegraph comments that Solidworks is the world's most popular CAD software. Its user base ranges from individuals to large companies, and covers a very wide cross-section of manufacturing market segments. Commercial sales are made through an indirect channel, which includes dealers and partners throughout the world. Directly competitive products to SolidWorks include Pro/ENGINEER, Solid Edge, and Autodesk Inventor.