MECHANICAL PROPERTIES OF MATERIALS 1) For a brass alloy, the stress at which plastic deformation begins is 345 MPa, and the modulus of elasticity is 103 GPa. a) What is the maximum load that may be applied to a specimen with a crosssectional area of 130 mm2 without plastic deformation? b) If the original specimen length is 76 mm, what is the maximum length to which it may be stretched without causing plastic deformation?
2) Consider cylindrical specimen of an aluminum alloy 10 mm in diameter and 75 mm long which is pulled in tension. Determine its elongation when a load of 13.5 kN is applied.
Tensile stress-strain behavior for an aluminum alloy 3) A cylindrical specimen of steel having a diameter of 15.2 mm and a length of 250 mm is deformed elastically in tension with a force of 48.9 kN. (E steel=207 GPa, Gsteel=830 GPa, steel = 0.27) Determine the following: a) The amount by which this specimen will elongate in the direction of the applied stress. b) The change in diameter of the specimen. Will the diameter increase or decrease? 4) Consider a cylindrical specimen of some hypothetical metal alloy that has a diameter of 10 mm. A tensile force of 1500 N produces an elastic reduction in diameter of 6.7x10-4 mm. Compute the modulus of elasticity for this alloy, given that Poisson’s ratio is 0.35. 5) A cylindrical metal specimen 12.7 mm in diameter and 254 mm long is to be subjected to a tensile stress of 28 Mpa; at this stress level the resulting deformation will be totally elastic. a) If the elongation must be less than 0.080 mm, which of the metals given in table are suitable candidates? Why? b) If, in addition, the maximum permissible diameter decrease is 1.2x10 -3 mm, which of the metals given in table may be used? Why?
6) A cylindrical rod 120 mm long and having a diameter of 15.0 mm is to be deformed using a tensile load of 35000 N. It must not experience either plastic deformation or a diameter reduction of more than 1.2x10-2 mm. Of the materials listed below, which are possible candidates? Justify your choice(s).
7) A cylindrical metal specimen having an original diameter of 12.8 mm and gauge length of 50.80 mm is pulled in tension until fracture occurs. The diameter at the point of fracture is 8.13 mm and fractured gauge length is 74.17 mm. Calculate the ductility.
8) Drive the following relations; T= (1+ ) and T= ln(1+ ) And also demonstrate that the expression used for true strain may also be represented by; T
Which expression ( true strain in term of length change or area reduction) is more valid during necking? Why?
9) For a brass alloy, the following engineering stresses produce the corresponding plastic engineering strains, prior to necking:
Engineering Stress(Mpa) 315 340
Engineering Strain 0.105
On the basis of this information, compute the engineering stress necessary to produce an engineering strain of 0.28.
10) A cylindrical specimen of a brass alloy 10 mm in diameter and 120 mm long is pulled in tension with a force of 11750 N; the force is subsequently released. a) Compute the final length of the specimen at this time. b) Compute the final specimen length when the load is increased to 23500 N and then released.