Elongation Data - Material Science and Engineering - Exam, Exams of Material Engineering

Download Elongation Data - Material Science and Engineering - Exam and more Exams Material Engineering in PDF only on Docsity! - 1 - MECH 6012 CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ Semester 2 Examinations 2007/08 Module Title: Material Science & Engineering Module Code: MECH 6012 School: Mechanical & Process Engineering Programme Title: Bachelor of Engineering (Honours ) in Mechanical Engineering – Stage 1 Programme Code: EMECH_8_Y1 External Examiner(s): Mr. Peter Clarke, Prof. Michael Gilchrist Internal Examiner(s): Dr Gerard Kelly Instructions: Answer any three questions. All questions carry equal marks Note if you attempt question 3 please return the equilibrium diagram with your answer book. Duration: 2 HOURS Sitting: Summer 2008 Requirements for this examination: Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator. - 2 - MECH 6012 Q1. A cylindrical specimen of aluminum having a diameter of 12.8 mm and a gage length of 50.80 mm is pulled in tension. Use the load vs. elongation data shown in the table Q1 below to answer the questions posed in parts (a) through (e). Load (N) Specimen Length (mm) 0 50.800 7330 50.851 15100 50.902 23100 50.952 30400 51.003 34400 51.054 38400 51.308 41300 51.816 44800 52.832 46200 53.848 47300 54.864 47500 55.880 46100 56.896 44800 57.658 42600 58.420 36400 59.182 Table Q1 (a) Plot the data as engineering stress vs. engineering strain. (7 marks) (b) Compute the modulus of elasticity. (7 marks) (c) Determine the yield strength at a strain offset of 0.002. (7marks) (d) Determine the tensile strength of this alloy. ( 6 marks) (e) What is the approximate ductility, in percent elongation? ( 6 marks) - 5 - MECH 6012 Q5. (a) Sketch the composite materials classification tree indicating broad classification of composite materials and their reinforcement. (6 marks) (b) What is meant by specific strength and specific modulus of reinforcement used in composite materials. What practical information does it provide? (6 marks) (c) A specific grade of carbon fibres have a tensile strength of 3.0 Gpa and a relative density of 1.74. E-glass fibres have a tensile strength of 3.5 Gpa and a relative density of 2.55. Compute the specific strength of the fibres. Comment on the result. (6 marks) (d) A uniaxial epoxy-glass fibre composite is reinforced with fibres in the longitudinal direction only. If the volume fraction of the fibres Vf = 0.6, firstly compute Vm and then estimate the elastic modulus of the fibres Ef used to reinforce the composite which will yield an elastic modulus for the composite in the longitudinal direction of Ecl = 50 GPa. Assume the elastic modulus of the matrix Em = 4.0 Gpa (7 marks) (e) Compute the elastic modulus of the composite in the transverse direction. (8 marks) TABLE 5-3 @ Error function values for Fick’s second law Argument Value of of the error function the error function x x ert 2\/Dt 2\/Dt O O 0.10 0.1125 0.20 0.2227 0.30 0.3286 0.40 0.4284 0.50 0.5205 0.60 0.6039 0.70 0.6778 0.80 0.7421 0.90 0.7970 1.00 0.8427 1.50 0.9661 2.00 0.9953 Note that error function values are available on many software packages found on personal computers. MECH 6012  - 7 - MECH 6012 Q3 Pb Sn Equilibrium diagram Student Name