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APSC278 2004 - Applied Science 278 December Exam 2004 THE...

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Applied Science 278 December Exam - 2004 1 THE UNIVERSITY OF BRITISH COLUMBIA Department of Metals and Materials Engineering APPLIED SCIENCE 278 Engineering Materials FINAL EXAMINATION, December 21 st , 2004 This is a Closed Book Examination. The use of calculators having stored information of relevance to this course is forbidden. Time: 2.5 hours Answer 4 of 5 questions. Each question is worth 25 marks. The complete exam is 7 pages in length. Some useful formulae, material data and a phase diagram are given on the last 2 pages of the exam. The use of sketches or schematic diagrams are encouraged wherever these will aid in solving or discussing a problem. Show all work!! Good Luck. Marks Question 1 (5) Sketch the nominal stress-strain curve for a typical ductile metal. On this sketch identify a. The yield strength b. The ultimate tensile strength c. The work hardening zone d. The onset of necking e. Fracture (3) On a separate sketch, show how you measure the 0.2% offset yield strength. Why do we use this graphical technique? (2) A 20 mm long sample of a ductile material tested to failure in tension shows a change in length prior to necking of 4 mm and change in length after necking of another 4 mm. What is the total change in length of a 40 mm sample of the same material? (3) The modulus of steel is 207 GPa. An annealed medium carbon steel has a yield strength of 276 MPa and a spring steel has a yield strength of 1034 MPa. What are their respective moduli of resilience? Why is this measure relevant in selecting a material for use as a spring? (2) What do we mean by heterogeneous yielding in steel? Use a sketch. (2) A ductile material with Young’s Modulus of 69 GPa is loaded past the yield point to a stress of 200 MPa. How much elastic recovery will the specimen show on unloading?
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