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Effect of Testing Speed on Several Alloys Susan Morford Alcoa Howmet Research Center susan.morford@alcoa.com 231.894.770

Effect of Testing Speed on Several Alloys Susan Morford Alcoa Howmet Research Center susan.morford@alcoa.com 231.894.7704. Overview of Methodology and Analysis Approach. Design of Experiment Alloys Strain rate / Crosshead speeds Three specimens for each test condition Analysis methodology

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Effect of Testing Speed on Several Alloys Susan Morford Alcoa Howmet Research Center susan.morford@alcoa.com 231.894.770

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  1. Effect of Testing Speed on Several AlloysSusan MorfordAlcoa Howmet Research Centersusan.morford@alcoa.com231.894.7704

  2. Overview of Methodology and Analysis Approach • Design of Experiment • Alloys • Strain rate / Crosshead speeds • Three specimens for each test condition • Analysis methodology • Graphical results • Ultimate Strength (KSI) • 0.2% Offset Yield Strength (KSI) • Percent Elongation (%) • Reduction of Area (%) • ANOVA to evaluate statistical significance of results • Summary of results

  3. Design of Experiment • Test Conditions (Full-factorial – all combinations were tested) • Strain rates • A – 0.005 inch/inch/minute • B – 0.015 inch/inch/minute • C – 0.050 inch/inch/minute • Crosshead rates • 1 – 0.05 inch/minute • 2 – 0.45 inch/minute • Strain Rate / Crosshead rates tested • A1, A2, B1, B2, C1, C2 • Strain rate measured with an extensometer directly attached to the reduced section of specimen; removed at 0.4% offset

  4. Design of Experiment • Equipment / Instrumentation • Tinius Olsen 60,000 pound load frame with Test Navigator version 7 software and 398 controller • Extensometer – 1 inch gauge length attached to reduced section of specimen

  5. Design of Experiment

  6. Analysis Methodology - Graphical Spread: ± 1 Standard Deviation Center Line: Mean of three (3) Specimens

  7. Analysis Methodology - ANOVA • Summary of ANOVA table obtained from SAS software • Interactions identified as significant are highlighted

  8. Ultimate Strength – 17-4PH

  9. 0.2% Offset Yield Strength – 17-4PH

  10. Percent Elongation – 17-4PH

  11. Percent Reduction of Area – 17-4PH

  12. Ultimate Strength – CMSX-4 ®

  13. 0.2% Offset Yield Strength – CMSX-4 ®

  14. Elongation – CMSX-4 ®

  15. Reduction of Area – CMSX-4 ®

  16. Ultimate Strength – Cast Alloy 718

  17. 0.2% Offset Yield Strength – Cast Alloy 718

  18. Elongation – Cast Alloy 718

  19. Reduction of Area – Cast Alloy 718

  20. Ultimate Strength – Wrought Alloy 718

  21. 0.2% Offset Yield Strength – Wrought Alloy 718

  22. Elongation – Wrought Alloy 718

  23. Reduction of Area – Wrought Alloy 718

  24. Ultimate Strength – Stellite 31®

  25. 0.2% Offset Yield Strength – Stellite 31®

  26. Elongation – Stellite 31®

  27. Reduction of Area – Stellite 31®

  28. Ultimate Strength – Ti-6-4

  29. 0.2% Offset Yield Strength – Ti-6-4

  30. Elongation – Ti-6-4

  31. Reduction of Area – Ti-6-4

  32. ANOVA Summary for Significant Relationships

  33. Variation in Time to Fracture

  34. Conclusions • Five of the six alloys evaluated at room temperature had at least one tensile property that is dependent on the speed of testing • ASTM E21-05 Standard Test Methods for Elevated Tension Test of Metallic Materials • Section 9.6 addresses “Strain Measurement and Strain Rate” • Tensile properties of materials at elevated temperature are affected by the rate of deformation • A similar statement should be included in ASTM E8

  35. Recommendations • Allow use of ASTM E-21-05 9.6.1.1 as an option or as a recommendation for room temperature testing • “During yield strength determination, maintain the stain rate in the uniform section of the specimen at 0.005 ± 0.002 /min. After yield strength determination, increase the crosshead motion to 0.05 ± 0.01 times the adjusted length of the reduced section of the specimen per minute.” • Add an Appendix to ASTM E8 and E21 addressing speed of testing

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