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     Engineering Mechanics》期末考试试卷/A

    Class: Name Registration No. Score

    No. I II III IV V VI Total


     Date: Jan. 11, 2008

I. Basic questions (Total 26 Points).

    1. (4 points) What are the endurance limit of a material and the endurance limit of a


    2. (4 points) Weight of the body is W, and pushing

    force is P. W=100N, P=500N. =0.3. S

    Determine the friction.

     3. (4 points) If a circular bar (d=2l), please , l) is replaced by another (d =2d, l112121

    compare their twist rigidity and strength.

     4. (4 points) If the impact loads are equal for the two bars, compare the impact stresses

    in the two bars.

     Fig. I-4 Fig. I-5

    5. (5 points) In order to enhance the load capacity of a beam, two proposals are offered as shown. (a) Two thick plates are piled up together directly without any bolt, and (b) two

    thick plates are piled up together with several bolts to tighten them (For instance, bolts are set at A, B and C). (1) Neglect the friction between plates in case (a), compare the load capacities in two cases. Write down relative equations. (2) Try to analyses the forces acting on bolts.

    6. (5 points) A connecting rod of a steam engine with an I-shaped cross section undergoes an axial compressive force. When the bending occurs in xy plane, it can be treated as

    two ends pin supported and as two ends fixed, when the bending occurs in xz plane. In

    which plane will it buckle? Please write down analysis process.

II. (12 points) Determine the force P required for the equilibrium of the compound lever

    if Q=4200N.

    III. (12 points) For a beam shown in the Fig. III, draw bending moment and shear force

    q=30kN/m P=20kN diagrams. M=10kNm

    A 2m 1m 1m B

    IV. (10 points) For the bar with rigidity EA shown in the Fig., find the reactions at ends

    and plot axial force diagram.

V(15 points) A horizontal bracket ABC is fixed at support A and free at C. The bracket is

    constructed from a circular cross-sectional bar with constant diameter d. A vertical

    acts at C. Find the vertical displacement δ at C (Energy method). load P v


     A B P a


    VI. (25 points) A circular shaft (d=200 mm) with bending moment M = 96kNm and

    torque T= 125kNm is shown in the figure. Points A and B are the points on the surface of the shaft. Let E=200GPa, = 0.25 and = 160 MPa. (a) Draw stress elements at allow

    th A and B; (b) Exam the shaft with 4strength theory; (c) Find ; (the normal strain 45

    along 45 direction with axis at B.) z

     M A M


    B y

     45 T T T x

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