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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Autumn Examinations 2009/
Module Title: Mechanical Materials (2D)
Module Code: MECH
School: School of Mechanical & Process Engineering
Programme Title: Bachelor of Engineering (Honours) in Mechanical Engineering Bachelor of Engineering (Honours) in Biomedical Engineering
Programme Code: EMECH_8_Y EBIOM_8_Y
External Examiner(s): Prof. Robin Clarke, Mr. John J. Hayes Internal Examiner(s): Mr. W. Corr
Instructions: Answer any three questions
Duration: 2 Hours
Sitting: Autumn 2010
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. If in doubt please contact an Invigilator.
Q1. At a point on the free surface of a steel (E = 200 GPa and v = 0.30) machine part, the strain rosette shown in Fig.1 below was used to obtain the following normal strain data:
a 875 , b 700 , c 350 .
Determine: (a) The principal strains and the maximum shearing strain at the point. (5 marks) (b) The stress components x, y and xy at the point. (6 marks) (c) The principal stresses and the maximum shearing stress at the point. (5 marks) (d) Sketch Mohr’s Circle of stress for this loading situation. (4 marks) Note: This is not a “rectangular” rosette.
Q4. A rubber plug has a diameter of 30 mm and fits within a rigid sleeve having an inner diameter of 32 mm. Both the plug and the sleeve are 50 mm long. (a) Determine the axial pressure p that must be applied to the top of the plug to cause it to contact the sides of the sleeve. (8 marks) (b) Also, how far must the plug be compressed downward in order to do this? The plug is made from a material for which = 5 MPa. v = 0.45. (4 marks) (c) Finally, if a total downward compression of 10 mm is required, what additional pressure is required to achieve this? (8 marks) Hint: Treat the before-contact and after-contact situations separately.
Q5. (a) Figure 5.1 show a point in a test specimen which is stressed with a constant stress of 50 MN/m^2 in the x direction and with an increasing stress y in the y direction. If the specimen fails at a shearing stress of 35 MN/m^2 , what is the tensile value of y at failure? (6 marks) (b) A glued joint between two lengths of material is shown in figure 5.2. The glue used is one of a range of modern adhesives which have extremely high shear strength. The joint is therefore best orientated in a plane that has shear stress only acting on it. Determine the optimum value of the angle , and the magnitude of the corresponding shear stresses. (8 marks)
(c) Sketch (neat) Mohr’s circles of stress for each case (a) and (b) indicating key values. (6 marks)
Fig 5.1 Fig 5.
