HW 2 MET 14400 s24 (1)

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Purdue University *

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Mechanical Engineering

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Feb 20, 2024

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Grading instructions provided to the grader: -1 no questions (mark as NQ) -1 overly sloppy (mark as OS) For each answer: -0 if content is similar to key answer (it’s OK if the student answer is less comprehensive than the key answer) -1 if content is partially similar to key answer but has some errors -2 if content differs significantly from the key answer Name (last, first) ___________________ MET 14400 Materials and Processes II Homework #2 – 20 points Q&A due 11:59m ET on BrightSpace on Thursday, Jan 25 th Questions are taken from DeGarmo’s Materials and Processes in Manufacturing by Black and Kohser or related calculations. Book question numbers correspond to the 13 th edition. Any additional references should be cited. Each answer is worth two points . Show supporting work for all calculations. Upload questions and answers to BrightSpace as one Word or pdf file. Chapter 2 1. What are some of the important categories for properties of materials? 2. “Strong materials can be brittle and brittle materials can be strong.” Conversely, weak materials can be brittle and strong materials can be ductile. What does the engineering stress-strain plot of a relatively strong ductile material look like? What does the plot of a relatively weak brittle material look like? Sketch both curves on one set of axes. 3. What makes a static property? a dynamic property? 4. (Textbook #14, page P-3) What is Young’s modulus or stiffness, and why might it be an important material property? 5. Describe (or define) the modulus of resilience and the modulus of toughness. 6. Calculate the axial stress in a tube that is stretched by a tensile axial force of 4500 N if the tube has an outer diameter of 25 mm and an inner diameter of 20 mm. A tensile test was conducted on a flat dogbone specimen made of an unknown polymer. The stress-strain plot is shown. The coordinates for points A, B, and C are (0.003 mm/mm, 0.0 MPa). (0.027 mm/mm, 4.8 MPa), and (0.059 mm/mm, 9.9 MPa). The gage length for the test is 50.8 mm.

7. The tensile force stretches the specimen so that the length between gage marks at rupture (breaking) is 59.3 mm. Use the material’s percent elongation to show if it is brittle or ductile. 8. Determine the material’s modulus of elasticity and its modulus of resilience, based on the three known data points. 9. (book #50) What is the endurance limit? What occurs when stresses are above it? Below it? 10. (book #57) Why is it important for a design or manufacturing engineer to know a material’s properties at all possible temperatures of operation and production? 11. (book #74). Why is it important to consider the orientation of a test specimen with respect to the overall piece of material? C Stress, σ, MPa B A Strain, Ɛ, mm/mm

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