Câu hỏi trắc nghiệm Tiếng Anh - Bài 1

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Câu hỏi trắc nghiệm Tiếng Anh - Bài 1 - Lớp MEC211B (16-17)

Đăng bởi: lethithanhbinh
Sinh viên
18/03/2017

Two identical circular rods of same diameter and same length are subjected to same magnitude of axial tensile force. One of the rods is made out of mild steel having the modulus of elasticity of 206 GPa. The other rod is made out of cast iron having the modulus of elasticity of 100 GPa. Assume both the materials to be homogeneous and isotropic and the axial force causes the same amount of uniform stress in both the rods. The stresses developed are within the proportional limit of the respective materials. Which of the following observations is correct?

(a) Both rods elongate by the same amount

(b) Mild steel rod elongates more than the cast iron rod

(d) As the stresses are equal strains are also equal in both the rods

A steel bar of 40 mm × 40 mm square cross-section is subjected to an axial compressive load of 200 kN. If the length of the bar is 2 m and E = 200 GPa, the elongation of the bar will be:

(a) 1.25 mm
(b) 2.70 mm
(c) 4.05 mm
(d) 5.40 mm

3. The ultimate tensile strength of a material is 400 MPa and the elongation up to maximum load is 35%. If the material obeys power law of hardening, then the true stress-true strain relation (stress in MPa) in the plastic deformation range is:

(a) 540.e^0.30

(b) 775. e^0.30
(c) 540. e^0.35
(d) 775. e^0.35

An axial residual compressive stress due to a manufacturing process is present on the outer surface of a rotating shaft subjected to bending. Under a given bending load, the fatigue life of the shaft in the presence of the residual compressive stress is:

(a) Decreased

(b) Increased or decreased, depending on the external bending load

(d) Increased

A static load is mounted at the centre of a shaft rotating at uniform angular velocity. This shaft will be designed for

(a) The maximum compressive stress (static)
(b) The maximum tensile stress (static)