automotive engineering laboratory i lecturer prof.dr. demir bayka

AUTOMOTIVE ENGINEERING LABORATORY

I

LECTURER

PROF.Dr. DEMIR BAYKA

INTRODUCTION

APPROACH TO

EXPERIMENTATION

THEORY & EXPERIMENTATION in ENGINEERING

PROBLEM SOLVING APPROACHES

• There are 2 fundamental approaches for problem solving in engineering

1. Theoretical

2. Experimental


1. Theoretical : Physical / Mathematical Modeling

1. Experimental : Measurement


Regardless of the Discipline( ME, EE, ChE, CE,.....)

• or the Engineering Function( Design, Development, Research, Manufacturing,

Maintenance, etc.,..)

either of these or more probably a judiciously chosen mix of these techniques is required


• Some general characteristics of these methods which will be helpful in deciding on the proper blend when choice is necessary are identified below.

• This also helps to organize your thinking about the whole process.


• Whenever some device or process is described with mathematical equations based on physical principles, the real world is left behind to a greater or lesser degree.

i.e. all physical principles and their mathematical expression when applied to the real world situations are approximations of the real behaviour.


• These approximations may be good, fair or poor, but some disrepancy between modelled and real behaviour always exists.

• Although the quality of these approximations are improved as time goes by, perfection is an unreachable goal.


• We also need to remember that practical engineering, in contrast to pure science labors under constraints, sometimes overriding constraints of

Time

&

Money


i.e an engineer may be well aware of a nearly perfect theoretical aapproach to a problem but will conciously choose instead a simpler and less accurate method, which is judged

“good enough”

in terms of overall project objectives.


• Thus our first comparison of theory and experiment centers on the fact that• Theories are always approximations

involving simplifying assumptionswhere as

• Experiments are run on the actual system

and when properly designed and executed reveal the true behaviour.

Features of alternative methods of problem solving

Theoretical methods

• Study mathematical models of the real world which always require simplifying assumptions.

Experimental methods

• Study the real world, no simplifying assumptions are required.


Theoretical methods

• Study mathematical models of the real wold which always require simplifying assumptions.

• Give general results to a wide class of problems.

Experimental methods• Study the real world, no

simplifying assumptions are required.

• Give results specific to the apparatus studied.


Theoretical methods• Study mathematical

models of the real wold which always require simplifying assumptions.


• Relaxation of assumptions leads to more complex math. model




• Higher accuracy measurements require more complex instrumentation


Theoretical methods• Study mathematical models

of the real wold which always require simplifying assumptions.


• Relaxation of assumptions leads to more complex math. Model.

• Facilities needed to commence study can be meager( trained personnel + paper &pencil )




• Higher accuracy measurements require more complex instrumentation.

• Extensive

(and expensive ) laboratory facilities may be needed.


Theoretical methods• Study mathematical models of

the real wold which always require simplifying assumptions.


• Relaxation of assumptions leads to more complex math. Model.

• Facilities needed to commence studycan be meager (trained personnel + paper &pencil )

• Study can commence promptly




• Higher accuracy measurements require more complex instrumentation.

• Extensive (and expensive ) laboratory facilities may be needed.

• Time delays may occur in apparatus construction and debugging

Functional types of Engineering Experiments

1. Determination of material properties and object dimensions.


• Determination of material properties and object dimensions.

• Determination of component parameters, variable and performance indices.



2. Determination of component parameters, variable and performance indices.

3. Determination of system parameters, variables and performance indices.





4. Evaluation and improvement of theoretical models.






5. Product / process improvement by testing.






5. Product / process improvement by testing.

6. Exploratory experimentation.





4. Evaluation and improvement of theoretical models.5. Product / process improvement by testing.6. Exploratory experimentation.

7. Acceptance testing.





4. Evaluation and improvement of theoretical models.5. Product / process improvement by testing.6. Exploratory experimentation.7. Acceptance testing.

8. Use of physical models and analogues.





4. Evaluation and improvement of theoretical models.5. Product / process improvement by testing.6. Exploratory experimentation.7. Acceptance testing.8. Use of physical models and analogues.

9. Teaching / learning through experimentation.






5. Product / process improvement by testing.6. Exploratory experimentation.7. Acceptance testing.8. Use of physical models and analogues.9. Teaching / learning through experimentation.

FUNDAMENTAL CONCEPTSIN

MEASUREMENT&

EXPERIMENTATION

WHAT IS “MEASUREMENT” ?

IN GENERALIT IS THE AQUISITION OF INFORMATION

THEREFORE WITH RESPECT TO INFORMATION :

1. STRUCTURAL INFORMATION2. METRIC INFORMATION

1. STRUCTURAL INFORMATION

THIS IS THE INFORMATION ONSTATE OR NATURE

OF A CERTAIN CHARACTERISTIC


SO YOU ASK YOURSELF WHAT IS THE IMPORTANT CHARACTERISTIC OF THAT SOCKET ?

THE ANSWER IS : VOLTAGE

FOR EXAMPLE YOU WANT TO KNOW IF AN ELECTRIC SHAVER WILL WORK WHEN YOU PLUG IT IN TO THE SOCKET

AS A RESULT OF STRUCTURAL INFORMATION THE INDEPENDANT

VARIABLES THAT SHOULD BE OBSERVED ARE DETERMINED


THE AQUISITION OF STRUCTURAL INFORMATION IS CALLED QUALITATIVE MEASUREMENT

2. METRIC INFORMATION

THIS IS THE INFORMATION ABOUT THE QUANTITY OF AN

INDEPENDANT VARIABLE.

IT IS OBTAINED AS A RESULT OF QUANTITATIVE MEASUREMENT

IN THE FIELDS OF SCIENCE AND ENGINEERING BOTH STRUCTURAL

AND METRIC INFORMATION IS NECESSARY.

BEFORE METRIC INFORMATION IS AQUIRED STRUCTURAL

INFORMATION IS NEEDED

QUANTITATIVE MEASUREMENTS ARE ABOUT :

MATERIAL PROPERTIES• DENSITY• THERMAL CONDUCTIVITY• HEATING VALUE• VISCOSITY• MELTING POINT• LATENT HEAT OF EVAPORATION• ELASTIC MODULUS• SPECIFIC HEAT• ETC…...


COMPONENT PARAMETERS• DIAMETER• MASS• SPRING CONSTANT• ELECTRICAL INDUCTANCE• FLUID CAPACITANCE• THERMAL RESISTANCE• ETC…...


VARIABLES OF STATE• POSITION• FORCE• VOLTAGE• PRESSURE• TEMPERATURE• DIFFUSION RATE• ETC…...

SOME ASPECTS OF A MEASUREMENT

DESCRIPTIVESELECTIVEOBJECTIVE

REASONS FOR PERFORMING MEASUREMENTS

1. TO PROVIDE AN IMMEDIATE QUANTITATIVE ANSWER TO A SPECIFIC PROBLEM

• properties of a specific material• parameters of a specific object or a component• the state or performance of a specific system including system identification



systematic experimental tests to design and to develop new products



monitor and control engineering systems for

their proper operation and maintenance



To perform acceptance testing of components or systems by authorized agencies to demonstrate their conformity with preset standards before their use


2. TO COLLECT EMPIRICAL DATA WITH THE HOPE OF OBTAINING AN INSIGHT INTO A PHENOMENON AND LATER GO ON TO USE THE DATA TO FORM A THEORETICAL EXPLANATION OF IT.


3. TO VERIFY THE EXISTING THEORY

To collect data for complementing, verifying, and improving these theoretical or empirical models,

hypotheses, theorems, and laws by conducting “controlled

experiments”.

DISCOVERY OF NEPTUNE

AT 1820 FRENCH ASTRONOMER

ALEXIS BOUVARDOBSERVED A DESCREPENCY

IN URANUS’S PATHAS PREDICTED BY

NEWTON’S LAW

THE DEVIATION WAS SMALLBUT

IT WAS MORE THAN THEUNCERTAINTY OF THE

MEASUREMENT

NEWTON’S LAW OF GRAVITY WASFORMULATED AS A HYPOTHESIS

FOR EXPLAINING THEOBSERVATIONS OF

TYCO BRAHEKEPLER AND GALILEO

UNTIL THEN THOUSANDS OFPREDICTIONS HAD BEEN MADE

AND

THE PREDICTIONS HAD BEENOBSERVED

NOW THERE WAS A NEWOBSERVATION WHICH

DID NOT AGREE

WHAT SHOULD BE DONE ?

1. FORMULATE A NEW HYPOTHESIS WHICH WILL ALSO EXPLAIN THE NEW OBSERVATION

2. MODIFY THE BASIS OF THE EXISTING THEORY (ASSUMPTION OF THE FIXED NUMBER OF PLANETS)

A HYPOTHETICAL NEW PLANET WASCALCULATED AND LATER

OBSERVED

THUS NEPTUNE WAS DISCOVERED

LATER PLUTO WAS DISCOVEREDIN THE SAME MANNER

FOR TYPES 1 & 2 THE FOLLOWING

APPROACH CAN BE USED

STEP

A.1

QUESTION

WHAT IS THE OBJECTIVE OF THE EXPERIMENT ?

STEP POSSIBLE ACTION

A.1 a) THE PROBLEM MAY HAVE BEEN CLEARLY DEFINED FOR YOU

b) YOUR EXPERIENCE MAY HELP YOU TO DEFINE AN OBJECT

c) IN AN UNFAMILIAR SITUATION TRY A FEW TENTATIVE TESTS FROM WHICH AN OBJECTIVE MAY SUGGEST ITSELF

STEP CONCLUSION

A.1 OBJECTIVE IS DEFINED AND NOTED

STEP QUESTION

B.1 WHAT ARE THE IMPORTANT VARIABLES AND ARE THEY DEFINED ?


B.1 a) THE ANSWER MAY BE SELF EVIDENT

b) STEP A.1 MAY GIVE YOU A LEAD (BEWARE OF INCLUDING

DEPENDENT VARIABLES)

STEP CONCLUSION

B.1 THE VARIABLES ARE SELECTED AND PERHAPS A HYPOTHESIS IS MADE

STEP QUESTION

B.2 WILL GROUPING OF VARIABLES REDUCE THE AMOUNT OF TESTING ?


B.2 a) GROUPING CAN BE BASED ON PHYSICAL ARGUMENTS

b) PERFORM A DIMENSIONAL ANALYSIS

STEP CONCLUSION

B.2 ANY GROUPINGS ARE DECIDED UPON

STEP QUESTION

C.1 WHAT APPARATUS IS REQUIRED ?


C.1a) YOU WILL HAVE TO WORK

WITHIN THE LIMITS OF THE APPARATUS AVAILABLE

( DO YOU NOW HAVE TO REVISE THE CONCLUSION OF

B.1) ?

CONCLUSION OF B.1

THE VARIABLES ARE SELECTED AND PERHAPS A HYPOTHESIS IS MADE

b) REQUEST ADDITIONAL FACILITIES

STEP CONCLUSION

C.1 NECESSARY EQUIPMENT IS NOW AVAILABLE

STEP QUESTION

C.2 HOW WILL THE TESTS BE ORGANIZED ?


C.2 a) DECIDE WHICH QUANTITIES YOU WILL VARY AND IN WHAT ORDER

b) DECIDE WHO IS GOING TO DO WHAT

STEP CONCLUSION

C.2 TEST PLAN IS DRAWN UP AND JOBS ARE ALLOCATED

STEP QUESTION

C.3 HOW WILL THE DATA APPEAR ON YOUR NOTES ?


C.3 a) DECIDE ON THE RANGE OVER WHICH EACH VARIABLE MAY CHANGE C.1 a) MAY IMPOSE A LIMITATION

C.1 a) YOU WILL HAVE TO WORK WITHIN THE LIMITS OF THE APPARATUS AVAILABLE


C.3

a) DECIDE ON THE RANGE OVER WHICH EACH VARIABLE MAY CHANGE C.1 a) MAY IMPOSE A LIMITATION

b) PREPARE A TABLE INTO WHICH DATA CAN BE ENTERED. IS A REFERENCE TEST NUMBER NEEDED ?

c) DECIDE WHETHER ACCURACY OF THE MEASUREMENTS WILL ENSURE A MEANINGFUL RESULT

d) PREPARE AXIS ON WHICH CONTROL CURVES CAN BE PLOTTED

STEP CONCLUSION

C.3 a) NOTEBOOKS ARE PREPARED

b) TEST IS PERFORMED

c) DATA IS RECORDED

d) CONTROL CURVES ARE DRAWN

STEP QUESTION

D.1 WHAT DO THE CONTROL CURVES SHOW ?


D.1 a) TAKE ADDITIONAL READINGS WHERE BAD POINTS OCCUR

b) TAKE ADDITIONAL READINGS IN BADLY DEFINED AREAS

STEP CONCLUSION

D.1 DATA IS NOW COMPLETE

STEP QUESTION

E.1 HOW WILL THE RESULTS BE PRESENTED ?


E.1 a) DECIDE BETWEEN GRAPHICAL, TABULAR OR FORMULA PRESENTATION

b) IF (a) DEMANDS IT PERFORM A CURVE FITTING EXERCISE

STEP CONCLUSION

E.1 RESULTS ARE ANALYSED

STEP QUESTION

E.2 WHAT DO THE RESULTS MEAN ?


E.2 a) ESTABLISH THE VALIDITY OR OTHERWISE OF THE HYPOTHESIS MADE IN B.1

b) ESTABLISH THE CONFIDENCE WHICH CAN BE PLACED IN THE NUMERICAL RESULTS

c) EXPLAIN THE NATURE OF ANY TRENDS

d) EXPLAIN DEVIATIONS FROM ANY THEORETICAL EXPECTATIONS

STEP CONCLUSION

E.2 a) RESULTS ARE ANALYSED

b) EXPERIMENTAL ERRORS ARE INVESTIGATED

c) DISCUSSION SECTION IS WRITTEN

STEP QUESTION

F.1 IS THE TEST FINISHED ?


F.1 a) STATE THE LAWS YOU HAVE DISCOVERED

b) STATE ANY FURTHER INVESTIGATION YOU CONSIDER NECESSARY

STEP CONCLUSION

F.1 CONCLUSIONS ARE DRAWN AND RECOMMENDATIONS MADE

STEP QUESTION

F.2 HAVE YOU FINISHED ?


F.2 a) PROCEED AS DICTATED BY F.1(b)

b) STATE ANY FURTHER INVESTIGATION YOU CONSIDER NECESSARY

F.1

STEP CONCLUSION

F.2 TEST CONTINUES OR

REPORT IS PREPARED

automotive engineering laboratory i lecturer prof.dr. demir bayka

Documents

real behaviour

real wold

real world situations

relaxation of assumptions

mathematical expression

mathematical equations

modelexperimental methodsstudy

general results