Computer aided design questions and answers

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Computer aided design questions and answers

TWO MARK QUESTION AND ANSWERS

1.THE DESIGN PROCESS

Define geometric modeling?

The geometric modeling concerned with computer compatible mathematical description of geometry of an object. The mathematical description should be such that the image of the object can be displayed and manipulated in computer terminal, modification on the geometry can be done easily and the image can be stored in computer memory retrieve back to display in computer screen for review, analysis or alternation.

Name phases related to production-consumption cycle in morphology of design.

Planning for production
Planning for distribution
Planning for consumption
Planning for retirement

What is ADAMS?

ADAMS is an acronym of Automatic Dynamic Analysis of Mechanical
System. It is one of kinematics analysis software.

4. Mention two important design analysis carried out using 3D model.

Analysis for mass properties
Finite Element Analysis (FEA)

5. Define CAPP?
CAD database used for process planning activites (i.e. two determine the
order of machining other manufacturing processes) are known as computer
aided process planning (CAPP).

What is meant by CIPMS?

Many of the activities of production planning and control (PPC) can
be carried with help of computers are known “Computer Integrated
Production Management Systems” (CIPMS).

What are elements of CAE?

1. Computer Aided Drafting.
2. Computer Aided Design
3. Computer Aided Machining

8. Mention one application of CAE.
(a) In the design and development of plastic injection models, CAE helps in
(i) Design of mould base configurations which are based on constraints relating to
resin temperatures and pressure. (ii) Moulding requirements and (iii) the type of
mould and Moulding machine to be used etc.

9. Define CAD. Mention areas of application of CAD.
The computers help in design and draft is commonly expressed by the term “Computer Aided Design” (CAD). A CAD system helps designer in various ways
1. Invites and promotes interaction through various input/output devices.
2. Allows manipulation of image (such as scalling, translation, rotation) in the computer screen.
3. Enable the designer to carry out the engineering analyses for stress, vibration, noise thermal distortions and more using FEA.
4. Design optimization through simulation and animation.
5. Automated drafting.

Define CAM?

The computer help in any non design function (such as process planning, production planning&control, machining, quality control, assembling and packaging) 0f manufacturing known as “Computer Aided Manufacturing” (CAM).

Define and classify CAQC?

The computers used in quality control activities are known as computer aided quality control (CAQC).This can be classified into Computer Aided Inspection (CAI) and Computer Aided Testing (CAT)

What is meant by Modular construction and explain its use?

It means that the main assembly of the product should be divided into no of modular/sub assemblies. This makes the assembly process easier, since sub assembly works are carried out separately and hence time for assembly reduces.

What is meant by sandwich construction and explain its use?

Both in main assembly and sub assemblies of the product, components are to be assembled one by one. The positioning of a component is made easy by previously assembled parts. Advantages is that a pick and place robots can be used in assembly works.

What is meant by concurrent engineering?

The concept and practice of various functions or departments working together, from the beginning, to engineer a product.

What is DFM?

DFM (Design for manufacturability or manufacturing or manufacture).It is the set of rules to be followed at the product design stage itself, to facilitate production.

Define CAE?

CAE (Computer Aided Engineering).The use of computer system for functions that are essential to engineering a product.

Name any 4 reasons for implementing CAD in design?

1. CAD can make each design step much easier and less tedious for designer to perform.
2. Errors during change of design will be less.
3. Models generated can be easily manipulated and modification in the model can be done very easily carried out in the system itself.

What are main features of drafting software?

1. Drawing utilities-units, limits, scalling, grid, snap etc.layer, line type, text size, and, font etc.
2. Drawing entities-line, arc, circle, polygen, box, sphere, cone etc.
3. Editing- erace, undo, move, extent, offset etc.
4. Block option
5. Dimencing option.
6. Plotting.

What is an operating system?

An operating system (OS) is a set of interrelated collection of supervisory software that control the over all operation of a computer to supervise it’s own operation by calling in the application programs and managing the data need to produce the designed output by the user.

What is the Design lead time?

It is the time taken from identification of design problem to getting detail diagram as output of design.

What is DFA?

The concept and practice of taking all elements into account at the product design stage to ensure ease of assembling.

What are the advantages of Concurrent engineering?
The design decisions are taken by a team of multi disciplinary experts.
Changes and modification on the product design will be faster.
Higher quality.
What are the benefits of CAD?
New products are desigbed faster. CAD can drastically reduce the number of steps involved in the design process for a particular product and can also make each design step much easier and less tedious for designer to perform.
Hard copy of the drawings are of better quality. hence there will be less ambiguity and better quality.
Errors during change of design will be less.

What are the characteristics of concurrent engineering?
Product responsibilities lies on team of multi disciplinary group.
Integration of design, process planning and production will be achieved.
Frequent review of design and development process.
Rapid prototyping.

2.INTERACTIVE COMPUTER GRAPHICS

Define computer graphics.

Computer graphics may be defined as the process of creation, stortage and manipulation of drawings and pictures with the aid of a number.

What are the functions of IGC?

Solid modeling
Storage
Manipulation
Viewing

What are the various display control facilities in graphics?

Vector Generation
Windowing and viewing transformation.
Clipping transformation
Zooming
Panning
Transmitting information on a network and
Graphics libraries.

What is meant by view point?

The viewpoint is the area on the screen in which the contents of the window are to be displayed as an image.

What is viewing transformation and windowing transformation?

The processs of mapping from the model co-ordinate system to the screen co-ordinate system is known as viewing transformation
The viewing transformation in which no rotation is applied is called the windowing transformation.

What is meant by Clipping?

Clipping is the process of determining the visible portion of a drawing lying within a window and discarding the rest.

State the use of reflection transformation.

It allows a copy of the object to be displayed while the object is reflected about a line or a plane.

What is the use shading Technique?

This technique is used to display the images in natural way. It is based on the recognition of distance and shape as a function of illumination.

How information is transmitted on a network?

The data must be encoded using a protocol. Protocol is a set of rules that control the exchange of data between the communicating devices.

What are the main types of 2D transformations?

Translation
Scaling
Reflection
Rotation
Shearing

State the hidden line elimination.

The hidden line elimination can be stated as, “For a given three dimensional scene, a given viewing point and a given direction, eliminate from an appropriate two dimensional projection of the edges and faces which the observer can not see”.

Give any two characteristics of Bezier curves.

The curve is tangent to the first and last segments of the characteristics polygon.
The curve is symmetric with respect to u and (1-u). Therefore, the sequence of control points defining the curve can be reversed without change of curve shape.

Distinguish between Bezier curves and Cubic Spline curve.

Sl.No.	Bezier curves	Cubic Spline curve
1.	The shape of Bezier curve is controlled by its defining points only	First order derivatives are used in the curve development.
2.	The curve does not pass through the given data points. Instead, these points are used to control the shape of the resulting curves.	These curves pass through the given data points only.

What are the characteristics of B-spline curves?

The B-spline curves do not pass through the first and last control points except when a linear blending functions are used
A non-periodic B-spline curve pass through the first and last control points and is tangent to first and last segments of control polygon.
A second degree curve (k=3) is always tangents to the midpoints of all the internal polygon segments

Define rational curve.

Rational curve is defined by the algebraic ratio of two polynomials while a non-rational curve is defined by one polynomial.

Define database.

Database can be defined as a collection of data in a single location designed to be used by different programmers for a variety of applications.

Mention the ways of using data structure in interactive modeling.

It allows interactive manipulation such as addition, modification and deletion of data.
It supports multiple types of data element like geometric, textual, dimensions, labels. Tool paths, finite, elements and so on.
It allows the property such as pen number, line style, color and so on to be associated with geometric elements.

Give the advantages of centralized data structure.

Enforce standards that mean with central control of the database, both the national and international standards are followed.
Access to sensitive data and projects can be checked and controlled by assigning each used proper access code to various parts of the database.
Balance conflicting requirements.

State the various activities of data base management.
Organize a database
Add a new data to the database
Sort the data in some meaningful order
search the database for types of information
Print the data into formatted reports
Edit the data and delete the data

What re the elements of information system?

Planning and control
Operation element and
Evaluation element

What are the problems surrounding database.

There is possibility of invalid input information by a unit wishing to maintain information security.
If anybody enters the ‘error’ data, it affects other departments immediately and produces “multiplier effect”.

What re the aspects of data life cycles?

We need how data are generated i.e. how they are born.
We need to know what manipulation or processing of data is carried out.

What are the special features for a good database system?

Satisfy current and future application needs.
Validate data before storage
Be easy to modify with changes
Be expandable with growth and changes
Allows access for the data only to authorized persons.

What are the characteristics needed for a good information system?

It should undertake the various activities of acquisition, processing, retention, transmission and reporting of information.
It should be designed to follow the pattern and structure of management at all levels of the organization.
It should not restrict the informal passage of information throughout the organization.

What are the two modes of data storage?

Sequential form and
Random form

What are the advantages of data bank?

The accumulation of information in an information center where “One set of books” is maintained avoids the maintenance of separate record files.
It tends to integrate the separate functions and departments of the company/Industry.

What are the advantages of having centralized control of database?

Eliminate redundancy
Maintain integrity which ensures its accuracy. Integrity proceeds consistency.
Balance conflicting requirements.

What a re the characteristics of relational data structure?

Each cell in the table holds any one field.
No two rows or records can be identical. In an at least one of the columns there must be at least one entry that is unique.

3.SOLID MODELLING
1. Classify geometric modeling.
1.wire frame modeling.
2. Surface modeling.
3.solid modeling.

Define sculptured surface.

Sculpture surface means the surface produced by combining two families of curves
that intersect one another in crisscross manner. Creating network of inter connected patches.

3. What is meant by lofted surface?
This is linear surface. It interpolates linearly between two-boundary curves.

List the common entities of a typical surface modeler?

           1. Plane surface.
2. Ruled (lofted) surface.
3. Surface of revolution.
4. Tabulated surface.
5. Bezier surface.
6. B- spline surface.
7. Cones patch.
8. Fillet surface.

Offset surface.

5. Name the two basic approaches followed in solid modeling.
a. Constructive solid geometry (CSG) or (C-rep).
b. Boundary representation (B - rep).

6. List the basic entities available in CSG approach of solid modeling.
(1) Cubold (2) Cylinder (3) Sphere (4) Cone (5) Wedge (6) Torus.

8. State Euler rule for topological checking.
V-E+F=2
Where,       V = number of vertices.
E = number of edges.
F = number of faces.

9. State Euler-Poincare formula for topological checking.
V - E + F - H + 2F = 2B
Where,          V = number of vertices.
E = number of edges.
F = number of faces.
H = number of holes.
F = number of passes or through holes.
B = number of separate bodies.

10. List some of the solid modeling softwares?
Pro/E, IDEAS. Unigraphics, CATIA, Solid works, Solid Edge, AutoCAD etc.

11.Define parametric modeling.
An approach to model parts belong to a family, rather than modeling the exact parts, a generic part is modeled with its dimensions as variable. The designer or application program simply specifies the variables value parameters) to develop a specific part model from the generic model.

12). What are the types of parametric modeling?
(1). Geometrically parameterized model: - in which dimensions of the
shape only be changed, but not the structure of the model.
(2). Topologically (or) structural parameterized model: - in which
both shape and topological arrangement of the model along with
dimensional change will be incorporated in the model.

13. What is meant by feature?
Feature has two meaning (a) Geometrical meaning: - shapes such as drilled holes, ribs, bosses in casting, grooves on the shaft etc are considered as feature. (b)Engineering meaning: - machining operations or attributes of components or data of components like material properties etc. In general, feature means prototypical shape with some engineering or memory.

14. What is meant by Implicit/unevaluated feature?
In this, the full detail of the feature will not be given only essential details will be given. Other data is calculated from essential details. Example: for gears only module and number of teeth will be given as essential data.

15. List the types of interfacing in CADCAM environment
a. Hardware - hardware interfacing.
b. Hardware - software interfacing.
c. Software - software interfacing.

16.List some of neutral file format to achieve software interfacing?
IOES - initial graphics exchange format.
DXF - data exchange format.
STEP- standard for exchange of product data
PDES - product data exchange.

17. What are the types of design analysis that can be carried our using 3D models?
a. Mass property analysis.
b. Finite element analysis.

18.What is PDES?
PDES(product data exchange specification). A specification for breading IGES to incorporates both design and manufacturing data. PDES bridges the gap between CAD and CAM by encouraging data exchange among different CADICAM system.

4.FINITE ELEMENT ANALYSIS

Classify the boundary conditions.

Primary boundary condition (or) Essential B.C. (or) geometric B.C.
Secondary boundary conditions (or) natural B.C.

What are the three phases of FEM?

Bandwidth solver
Skyline solver
Frontal solver

What are the three phases of FEM?

Pre processing
Analysis
Post processing

White are the different forms in which the FEM solutions are represented in post processing?

Tabulation Form: Here, the required numerical results are printed in a table at all nodes and/or at all elements at selected nodes or elements or at selected points inside element.
Graphical Form: To aid the visualization of results, the results are also represented in graphical form, like stress contours, animation of displacement etc.

What is meant by discretization in FEM?

Divide the domain into nodes and elements is known as discretization.

What do you mean by D.O.F. of a node?

In FEM, number of primary variables to be determined per node is known as “Degree Of Freedom of a node”.

Name the different variational methods.

Ritz method
Rayleigh-Ritz method

During discretization, mention the place where it is necessary to place a node?

Points at which the concentrated load acts.
Points at which abrupt change in load occurs.
Points at which the cross section change occurs
Points at which different materials interjunction occurs.

Where are ‘h’’ and ‘p’ versions in F.E. method?

The accuracy of the FEM solution can be improved by several ways. IN conventional approach called h-version of finite element method, the order of polynomial approximation for all elements is kept constant and the number of elements are increased in such a way that the size of the largest element (hmax) approaches to zero. But in p-versions the number of elements is maintained constant and the order of polynomial approximation of element is increased.

What is the difference between static and dynamic analysis?

Static analysis:
The solution of the problem that does not vary with time is known as static analysis.
Example: Stress analysis on a beam, hoop stress distribution on the            cylindrical wall subjected to internal pressure, etc.
The static analysis can be further divide into Linear A non-linear static analysis. The non-linearity in the static analysis arises because of one or more combinations of the factors given below.
1. Material non-linearity of the material is not linear.
2. Large strain/large deformation-here stress or strain is within elastic limit
But deformation is high
Dynamic analysis:
The solution of the problem varies with time. Example: Impact load
On a structure, vibration problems to find natural frequency or
Transient response.
Here also the analysis can be further divided into linear and non-linear
analysis.

Name any four FEA softwares.

ABASCUS
ADINA
ANSYS
NASTRAN
COSMOS
NISA

What is meant by “Boundary value” problem?

In physical problems, we seek a solution of differential equation which satisfies some specified conditions known as the boundary conditions. The differential equation together with these boundary conditions, constitute a boundary value problems. There are two types of boundary value problems viz. linear and non-linear.

Slate the meaning and significance of shape function.

In FEM, field variables within an element are normally expressed in terms of nodal values. For example, 1D axial element
U=N1U1+N2U2
The shape functions decide the field variable contribution from each node. The field variable ‘U’ within the element depends upon the nodal value U1 and U2 and the actual magnitude depends on the shape functions N1 and N2

What are Global and natural co-ordinates?

Global co-ordinates: It is a co-ordinate system using which all elements are referred.
Natural co-ordinate: It is a local co-ordinate within the element which normally varies between 0 to 1 and -1 to +1. This system is normally represented by ξ in 1D and by ξ and η in 2D elements.

What is meant by element conductivity?

Element conductivity is nodal information of each individual element to form the complete physical system.

What is meant by “Initial value problem”?

The differential equation together with initial conditions constitutes an initial value problem. The general form of nth order initial problem is in the form of

dyn (t) = f{t, y(t), y1(t), y11(t),…}
dt
With initial conditions
y(to) = yo, y1(to) = y1o

What is higher order element?

Any element with a second order or a higher order interpolation function is called as higher order element. Within the element the field variable varies non-linearly.

What is truss element?

The truss element is the part of a truss structure linked together by point joints that transmit only axial force to the element.

Briefly explain node numbering and bandwidth.

                 The half band width or semi band width or semi band width is defined as the
Greatest number of coefficient of stiffness in any row of the global stiffness
Matrix from and leading diagonal to the outside right-hand non-zero coefficient.
The half band-width of the banded stiffness matrix is given by
nb = nd*(m+1)
where,     nd =Degrees of freedom per node
m= Max difference in node numbers of an element.

What is meant by “Aspect Ratio”?

The aspect ratio is defined as the ratio of the longest dimension Vs the shortest dimension of a quadrilateral element. In many cases, as the aspect ratio increases, the inaccuracy of the solution increases.

Mention the D.O.F. for a space frame element?

The space frame element will have 6 D.O.F. per node. Therefore, total D.O.F. of the element is 12.

Name two advantages of post processing.

Required result can be obtained in tabular or graphical form.
Contour diagrams and animated views will help to understand the solution easily and quickly.

What is post processing in FEM?

Post processor is also a graphical aid, which helps in interpretation of analysis result. The post processor accepts the nodal solutions from analysis and calculates the required results like stress, strain etc. It displays the result in the form of tables, graphs, contour diagram etc. for better understanding.

What is pre processing in FEM?

Manual preparation of input data is tedious, time consuming and error prone work, particularly while modeling 3D geometries, preprocessor is a graphical aid which helps in preparation of input data. It gets min input the user, and creates the F.E. model and other required for analysis and displays the model in the screen for checking and correction to be done on the model interactively by user.

What are advantages of FEM

Irregular geometries can be modeled more accurately and easily
Implementation of any type of boundary conditions is very easy.
Any type of loading can be handled.

What are the limitations of FEM?

FEA softwares are costlier
Output result will vary considerably, when the body is modeled with fine mesh when compared to body modeled with course mesh.

PART –B

Unit 1
The Design Process

1.What Is Design Process. Explain Briefly The Steps Involved In Design Process By Shiegly ?

Dr.Sadhu Singh Pageno :282-285

2. Explain Briefly The Four Models Of For The Design Process?

Dr.Sadhu Singh Pageno :283-292

3. What Is Computer Aidede Design ? Discuss The Various Design Related Tasks Performed In CAD?

Dr.Sadhu Singh Pageno : 292-295

4.Write A Short Note On Simultaneous Engineering & Concurrent Engineering?

Dr.Sadhu Singh Pageno :581-585

5.Compare Simultaneous Engineering & The Concurrent Engineering?

Dr.Sadhu Singh Pageno :581-585

6.What Are The Various Steps Involved In The Product Cycle?

Dr.Sadhu Singh Pageno :580-581

Unit 2

Interface Computer Graphics

1.What Are The 2d &3d Control Facilities. Explain In Brief With Figures.?

Dr.Sadhu Singh Pageno : 363-365
369-371

2. Explain The Varios 2d Transformation?

Dr.Sadhu Singh Pageno : 366-369

3.Explain The Various 3d Transformation?

Dr.Sadhu Singh Pageno : 369-372

4. List The Various Input Devices For Graphics &State Their Function?
Dr.Sadhu Singh Pageno : 330-334

5.Explain In Brief The Clipping Transformation?

Dr.Sadhu Singh Pageno : 364

6. Write Short Notes On Model Stroage &Data Structure?

Dr.Sadhu Singh Pageno :382-392

Unit 3
Solid Modelling

1.What Is Geometric Modelling? Explain The Geometric Models, Bringing Out Limitations & Applications?

Dr.Sadhu Singh Pageno :392-397

2. Describe The Technique For Surface Modelling?

Dr.Sadhu Singh Pageno : 428-430
Ibrahim Zied Page no:263-270
3. Compare B-Rep & C-Rep?

Dr.Sadhu Singh Pageno: 405-413

4. How 3d Solid Models Can Be Created . Explain Briefly The Methods?

Dr.Sadhu Singh Pageno :419-421

5.What Is Solid Modelling? Expain In Briefly The B-Rep & C-Rep?

Dr.Sadhu Singh Pageno : 402-413
Ibrahim Zied Pageno : 368-378

388-415

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