- A Nickel Titanium Alloy Is Used To Make Components For Jet Turbine Aircraft Engines Cracking Is A Potentially Serious P 1 (84.34 KiB) Viewed 29 times
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A nickel-titanium alloy is used to make components for jet turbine aircraft engines. Cracking is a potentially serious problem in the final part, as it can lead to non-recoverable failure. A test is run at the parts producer to determine the effects of four factors on cracks. The four factors are pouring temperature (A), titanium content (B), heat treatment method (C), and the amount of grain refiner used (D). Two replicates of a 24 design are run, and the length of crack (in um) induced in a sample coupon subjected to a standard test is measured. The data are shown below: Treatment Combination Replicate I Replicate II A B C D (1) a 7.037 14.707 11.635 17.273 h ab 6.376 15.219 12.089 17.815 10.151 4.098 9.253 12.923 с ac 10.403 4.368 9.360 13.440 bc abc d 8.561 16.867 8.951 17.052 ad bd 13.658 19.639 abd cd 12.337 13.876 19.824 11.846 6.125 11.190 15.653 acd bcd 5.904 10.935 15.053 abcd (a) Estimate the factor effects. (b) Which factors appear to be large? Hint: Construct a normal probability plot of the effect estimates. (c) Use the analysis of variance to confirm your conclusion. Do any of the factors affect cracking? Use a = 0.05. (d) Write down the fitted regression model that can be used to predict crack length as a function of the significant main effects and interactions you have identified in part (c). Hint: Consider the significant effects found in (c) into your model; follow hierarchy principle. (e) Analyze the residuals from this experiment. Are there any obvious problems? (f) What recommendations would you make regarding process operations? Use interaction and/or main effect plots to assist in drawing conclusions.