simulation and modelling and material selection

1. NATIONAL INSTITUTE OF TECHNOLOGY,
UTTARAKHAND
PRESENTATION ON
Modelling & Simulation
Material Selection
Presented to Presented by
Mr. Anshul Ashwani Kumar
Assistant Professor Roll No. MT16MEC012
(Department of Mechanical Engg.)

2. What is Model
A Representation of an object , a system or an idea in
some form other than that of itself.
(Shannon)
Model is the small scale replica of the actual structure or
components.

3. Simulation
3
 A simulation of a system is the operation of a model. The model
can be reconfigured and experimented with the operation of the
model can be studied, and hence, properties concerning the
behaviour of the actual system or its subsystem.[1]
 In its broadest sense, simulation is a tool to evaluate the
performance of a system.
 Simulation is used before an existing system is altered or a new
system built, to reduce the chances of failure to meet
specifications, and to optimize system performance.

4. Simulation model has two inputs
i. Controllable inputs
ii. Probabilistic inputs
Fig. 1
 Controllable inputs are those inputs which are controlled by decision
maker such as total quantity of goods produced by a firm, unit selling
cost of that product
 Probabilistic inputs are those inputs which are not controlled by
decision maker such as direct labour cost, demand etc.
Model
Probabilistic
inputs
Controllable
inputs
Output

5. Why are models used?
 To test a system without having to create the system for
real (Building real-life systems can be expensive, and take a
long time)
 To predict what might happen to a system in the future
 To train people to use a system without putting them at risk
(Learning to fly an airplane is very difficult and mistake will
be made. In a real plane mistakes could be fatal!)
 To investigate a system in great detail (A model of a system
can be zoomed in/out or rotated.

6. Terminology
 System
 A group of objects that are joined together in some regular
interaction or interdependence toward the accomplishment
of some purpose.
● Entity
 An object of interest in the system.
 E.g., customers at a bank

7. Terminology (continued)
 Attribute
 a property of an entity
 E.g., checking account balance
 Activity
 Represents a time period of specified length.
 Instantaneous occurrence that transform the
state of an entity
 E.g., making bank deposits

8. Terminology (continued)
 Event:
 change in the system state.
 E.g., arrival, departure
 State Variables
 Define the state of the system
 E.g. length of the job queue.

9. Terminology (continued)
 Process
 Sequence of events ordered on time
 Note:
 the three concepts(event, process, and activity) give
rise to three alternative ways of building discrete
simulation models

10. Examples of systems and components
System Entities Attributes Activities Events State
Variables
Banking Customers Checking
account
balance
Making
deposits
Arrival;
Departure
# of busy
tellers; # of
customers
waiting

11. STEPS IN A SIMULATION STUDY
Problem
formulation
Setting of
objectives
and overall
project plan
Model
conceptualization
Data
collection
Model
translation
Verified?
No
Validated?
No
No
Experimental
Design
Production runs
and analysis
More runs?
Documentation
and reporting
No
Implementation
Yes
Yes
Yes
Yes
Fig. 2

12. Designing Safer Cars
 A computer model of a car can be used to
test how safe the design of the car is in a
crash.[2]
 The virtual car can be crashed over and
over again, the effects investigated and
the design easily changed until it is as safe
as possible.
 This is much quicker and cheaper than
building and crashing real cars!
Fig.3

13. Weather Forecasting
 A computer model of a weather system can
be used to predict storms.
 The wind patterns, temperatures, etc. for
the whole planet are simulated using very
powerful computers.
(Since weather is so complex, and the
models are not yet accurate enough, often
the weather forecast is wrong!)
Fig. 4

14. Bridge Design
 A computer model of a bridge can be used to test
the design.
 Bridges have to be able to survive extreme weather
conditions. It is obvious not practical to build a
real bridge and then wait to see if it falls down in a
storm. Instead, a computer model of the bridge is
created and tested in virtual storms.
 Bridges can also be tested to see if they can cope
with heavy traffic.
A similar system is used by building designers,
especially for very large or tall buildings.

15. Training Pilots
Trainee pilots have many hours of lessons in flight
simulators before being allowed to fly a real
airplane.
Flight simulators behave almost exactly like real
airplanes since they are controlled by a computer
with a very accurate and realistic model of the
airplane. The main difference is that the
simulator can’t actually crash!
Pilots can make mistakes without putting anyone’s
life at risk.
Flight simulators can provide a pilot with any
number of highly realistic flying situations:
storms, engine failures, low cloud hiding the
runway, etc.
Fig.6

16. Advantages of Simulation
• When mathematical analysis methods are not available,
simulation may be the only investigation tool
• When mathematical analysis methods are available, but are
so complex that simulation may provide a simpler solution
• Allows comparisons of alternative designs or alternative
operating policies

17. Disadvantages of Simulation
 Simulation estimates the output while an analytical
solution, if available, produces the exact output
 Often expensive and time consuming to develop
 An invalid model may result with confidence in wrong
results.

18. Fig.7
Material Selection

19. Materials are selected on the basis of four general criteria:
• Performance characteristics (properties)
• Processing (manufacturing) characteristics
• Environmental profile
• Business considerations
Material Selection Criteria

20. Fig.9

21. Material Selection Example
Consider the question of materials selection for an automotive exhaust system.[3] The product
design specification states that it must provide the following functions:
 Conduct engine exhaust gases away from the engine
 Prevent noxious fumes from entering the car
 Cool the exhaust gases
 Reduce the engine noise
 Reduce the exposure of automobile body parts to exhaust gases
 Affect the engine performance as little as possible
 Help control unwanted exhaust emissions
 Have an acceptably long service life
 Have a reasonable cost, both as original equipment and as a replacement part

22. Material Requirements for an Automotive Exhaust System
Mechanical property requirements not overly severe.
 Suitable rigidity to prevent excessive vibration
 Moderate fatigue resistance
 Good creep resistance in hot parts
Limiting property:
corrosion resistance , especially in the cold end where gases condense to form corrosive liquids.
Properties of unique interest:
The requirements are so special that only a few materials meet them regardless of cost.
 Pt-base catalysts in catalytic converter
 Special ceramic carrier that supports the catalyst
Fig.10

23. Previous materials used:
Low-carbon steel with corrosion-resistant coatings.
Material is relatively inexpensive, readily formed and welded. Life of tailpipe and muffler is limited.
Newer materials used:
With greater emphasis on automotive quality, many producers have moved to specially developed stainless
steels with improved corrosion and creep properties. Ferritic 11% Cr alloys are used in the cold end
components and 17 to 20% Cr ferritic alloys and austenitic Cr-Ni alloys in the hot end of the system.

24. Tolerance
 A tolerance is the permissible variation from the specified dimension
 The designer must decide how much variation is allowable from the basic dimension of the
component to accomplish the desired function.
 The tolerance on a part is the difference between the upper and lower allowable limits of a
basic size dimension

25. Types of Tolerance
Bilateral tolerance
The variation occurs in both directions from the basic dimension. That is, the upper limit
exceeds the basic value and the lower limit falls below it.
2.500 ± 0.005 (This is the most common way of specifying tolerances)
Unilateral tolerance:
The basic dimension is taken as one of the limits, and variation is in only one direction

26. Standards & Codes in Design
Code is a collection of laws and rules that assists a government agency in meeting its
obligation to protect the general welfare by preventing damage to property or injury or loss of
life to persons.
Standard is a generally agreed-upon set of procedures, criteria, dimensions, materials, or
parts. Engineering standards may describe the dimensions and sizes of small parts like screws
and bearings, the minimum properties of materials, or an agreed-upon procedure to measure a
property like fracture toughness.
Fig.11

27. Some Background:
 The U.S. federal government is the largest single creator
and user of standards: more than 45,000 (by current
estimates)!
 About 210 organization are designated Standard
Development Organizations (SDO’s)
 Most Standards (about 90%) come from about 20 of these
SDO’s
 ASTM, ASME, IEEE, AISI (ASM), ASCE, are some of the most
important SDO’s

28. Why Standards & Codes ?
• it makes the best practice available to everyone, thereby ensuring efficiency and safety.
• it promotes interchangeability and compatibility. With respect to the second point, anyone who has
traveled widely in other countries will understand the compatibility problems with connecting plugs
and electrical voltage and frequency when trying to use small appliances
Fig.12

29. How they’re used:
 Standards are a
“COMMUNICATION” tool that
allows all users to speak the
same language when reacting to
products or processes
 They provide a “Legal,” or at
least enforceable, means to
evaluate acceptability and sale-
ability of products and/or
services
 They can be taught and applied
globally!
 They, ultimately, are designed
to protect the public from
questionable designs, products
and practices
 They teach us, as
engineers, how we can
best meet
environmental, health,
safety and societal
responsibilities

30. Figure References
 Fig.1.Simulation and modelling images-template.png.google images
 Fig.2. Researchers stage largest military simulation ever -.jpeg.google images
 Fig.3. Wescott bob 2013 ,the every computer performance book. Chapter7 modelling
performance.
 Fig.4. C. Rolland and C. Thanons penici (1998). "A Comprehensive View of Process
Engineering". In: Proceedings of the 10th International Conference CAiSE'98, B. Lecture
Notes in Computer Science 1413, Pisa, Italy, Springer, June 1998.
 Fig.5. Mylopoulos, J."Conceptual modeling and Telos1". In Loucopoulos, P.; Zicari,
R. Conceptual Modeling, Databases, and Case An integrated view of information
systems development. New York: Wiley. pp. 49–68.

31. References
 T. T . Woodson , Introduction to Engineering Design, McGraw-Hill, New York , 1966
, pp. 131–35 .
 P. E . Wellstead , Introduction to Physical System Modeling , Academic Press, New
York , 1979 ; W. G . Reider and H. R . Busby , Introductory Engineering Modeling,
John Wiley & Sons, New York , 1986 ; D. E . Thompson , Design Analysis,Cambridge
University Press, New York , 1999 .
 J. K . Liker , M . Fleischer , and D . Arnsdorf , “ Fulfilling the Promise of CAD, ”
Sloan Management Review, Spring 1992 , pp. 74–86 .
 M. F . Ashby ,Materials Selection in Mechanical Design, 3d ed., Elsevier
Butterworth-Heinemann,Oxford, UK , 2005 .
 ASM Handbook, Vol. 8,Mechanical Testing and Evaluation, ASM International,
Materials Park,OH , 2000 , pp. 198–287 .