Corrosion fatigue in metals has been defined as the

Chapter , Problem 9.4

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Corrosion fatigue in metals has been defined as the simultaneous action of cyclic stress and chemical Exercises 407 attack on a metal structure. A widely used technique for minimizing corrosion fatigue damage in aluminum involves the application of a protective coating. A study conducted by the Department of Mechanical Engineering at Virginia Tech used 3 different levels of humidity (Low: 2025% relative humidity; Medium: 55 60% relative humidity; High: 8691% relative humidity) and 3 types of surface coatings (Uncoated: no coating; Anodized: sulfuric acid anodic oxide coating; Conversion: chromate chemical conversion coating). The corrosion fatigue data, expressed in thousands of cycles to failure, were recorded as follows: Relative Humidity Coating Low Medium High Uncoated 361 466 1069 469 937 1357 314 244 261 522 739 134 1344 1027 1011 1216 1097 1011 Anodized 114 1236 533 1032 92 211 322 306 68 471 130 398 78 387 130 466 107 327 Conversion 130 841 1595 1482 529 754 252 105 847 874 755 573 586 402 846 524 751 529 (a) Perform an analysis of variance with = 0.05 to test for significant main and interaction effects. (b) Use Tukeys multiple-range test at the 0.05 level of significance to determine which humidity levels result in different corrosion fatigue damage.