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Spring Examinations 2011/ 2012
Exam Code(s) 3BM, 3BG, 3BSE Exam(s) 3 rd^ Mechanical Engineering 3 rd^ Biomedical Engineering 3 rd^ Energy Systems Engineering
Module Code(s) ME Module(s) Metals and Metal Processing
Paper No. 1 Repeat Paper
External Examiner(s) Prof. Robin Clarke Internal Examiner(s) Prof. Sean Leen Dr. Mark Bruzzi Dr. Barry O’Brien*
Instructions: (^) This paper contains 4 questions. Answer 3 questions.
Duration 2 hours
No. of Pages 4 including cover sheet Department(s) Mechanical & Biomedical Engineering Course Co-ordinator(s) Dr. Barry O’Brien
Requirements: MCQ Handout Statistical/ Log Tables Cambridge Tables Graph Paper Log Graph Paper Other Materials
Release to Library: Yes
a) Give brief definitions for strength, stiffness, ductility, toughness and hardness. [3]
b) Describe the difference between Vickers, Brinell and Rockwell hardness tests in terms of indentor types, loading conditions and features measured during or after loading. [4]
c) Figure Q1 (c) illustrates a bonding energy curve for two different atomic bonds (material 1 and 2). Which material has the highest melting point and which material has the highest elastic modulus? Provide brief explanations for your answer with respect to the curves. [4]
d) Explain why metals have higher thermal and electrical conductivity than other materials. [4]
e) Sketch a (001) plane and a (110) plane in a simple cubic crystal structure. [2]
f) Sketch a (111) plane for a Face Centred Cubic (FCC) crystal structure. On this plane show three close packed directions. What is the significance of close packed planes and directions? [3]
Figure Q1 (c)
a) Sketch the iron-carbon phase diagram up to approx 1.2 wt % carbon and up to approx 900°C. Show where Ferrite, Austenite+Ferrite, Austenite, Austenite+Cementite and Ferrite+Cementite exist. [4]
b) Sketch and label the equilibrium microstructures that exist for a 0.4 wt% carbon steel, a 0. wt% carbon steel and a 1.2 wt% carbon steel. Describe how the phases present influence both strength and ductility of these respective steels. [6]
c) Briefly describe the processes of carburizing and nitriding that can be used to surface harden steel components. In your description, explain the mechanism through which hardening is achieved. [4]
d) Describe what undesirable phase may form during the welding of a high carbon or alloy steel, explaining briefly the mechanism involved. Describe how a pre-heat treatment before welding may alleviate this. Use a schematic TTT diagram with superimposed cooling curves to support your answer. [6]
