Lecture 15: Test Procedure in Engineering Designmech350/Lectures/MECH350-Lecture-15.pdf · A good test plan/procedure must be developed prior to testing. This plan should include
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
MECH 350Engineering Design I
University of VictoriaDept. of Mechanical Engineering
In MECH350, we are interested in the evaluation of the design objectives. Hence, your tests should generally produce ‘quantitative’ results.Quantification of test results (with proper testing) allows for designers and clients to agree that the design objectives have been met.
Design of the Test (Also know as: Design of Experiment)Type of testing method and its significanceList of test apparatus and measurement equip, model #s, etc...Identify ‘dependant’ and ‘independent’ variables# of factors considered (single, double (factorial), etc...)Sampling procedure:
How are samples obtained?Number of samples
Detailed, step-by-step procedure to conduct the test.
Conduct/Perform the Test/ExperimentSafety precautionsData collection method (written, recorded, digital, etc...)Observation of external factors (temperature, wind, noise, vibration, etc...)
The subject of “Design of Experiments” is intimately related with statistics and statistical analysis, and is a major area of study. Hundreds of books, and courses are dedicated to the area.
Examples where “rigorous testing” is essential to demonstrate the performance of a consumer product:
If you are the engineer in charge, how are you going to “demonstrate the product meets performance expectations”? How are you going to prove/demonstrate it to the world?Answer: --> Proper Design of Experiment
Formal Hypothesis:A formal statement of what the experimenter expects to find in the data.For example: “Treatment of a material sample, will lower the percentage of sample failures under load.”
Null Hypothesis:A Hypothesis that is stated in a null form (which is more easily testable).For example: “There will be no difference in the percentage failures between those samples treated, and those that were not.”
Independent Variable:Is a controllable experimental variable. By changing/controlling the Independent Variable during an experiment, we seek to see if that contributes to a response in the Dependent Variable.
Dependent Variable (Response Variable):Is a characteristic outcome of an experiment on which information is to be gathered or obtained.The outcomes of a true experiment should be random, so a dependent variable is a random variable. There is a probability distribution associated with different kinds of random variables, such as: Normal, Poisson, Binomial, Chi-squared, Student t, Beta, Gamma, and many other distributions.
Full treatment of the subject of design of experiments is beyond the scope of MECH350, but it is vitally important in the testing phase of engineering design.
For further information, consider the following references:[1] C.R. Hicks, K.V. Turner, “Fundamental Concepts in the Design of Experiments”, Fifth Edition, Oxford University Press, 1999.Wikipedia, “Design of Experiments”, available online: http://en.wikipedia.org/wiki/Design_of_experiments
Good testing documentation serves to show others that your design has met the intended design objectives.
The test report should be written in such a way, as to allow an independent, third-party to review the test plan, the experimental design, the collected data, and the data analysis, and allow them to generally come to the same conclusions/test results that you did.
A good testing report is similar to a “laboratory report”, but includes extra elements (next page).
Elements of a Test Report:Scope (see page 9)Administrative Details (page 9)Design of Test (page 10)Procedure (step-by-step of how test is conducted)Data collected
Summary if lengthy, with raw data in Appendix.Other noteworthy observations (just state the facts and leave comments/discussion for later).
Analysis and Interpretation of DataSummary of Results and Discussion
Table format for this is helpful (see next page)Ideas for Further experiments or experimental improvementConclusion
Objective (Target) Test Result Objective Met? DiscussionSize (L x W x H) La x Wa x Ha Yes Explain . . .Weight (10 lbs) 12 lbs No Explain . . .Noise (73 dB) 70 dB Yes Explain . . .Cost ($350) $250 No Explain . . .