中国石油大学工程力学考试Exam11121A.docx

1、中国石油大学工程力学考试Exam11121AA卷 中国石油大学北京20112012学年第一学期 工程力学双语期末考试试卷考试方式闭卷考试班级： ： 学号： 题号IIIIII IVVVI总分得分 试卷不得拆开，所有答案均写在题后相应位置I (Total 30 points) Fill up the blanks with correct answer.1. (4 points) Stress-strain curves for three materials are shown below. Material (1, 2, 3) has the highest ultimate stress.

2、Material (1, 2, 3) has the largest elastic modulus.2. (6 points) As shown, a strain gage is pasted on the surface of a circular bar with diameter d to test the torques acting on two ends. If elastic modulus and poissions ratio of the material are known and the strain in gage is, the torque= .(a) (b)

3、 (c) (d) 3. (4 points) The boundary conditions on left end for a beam as shown are .a. v(a)=0,EIv”(a)=kv(a) b. v(a)=0, EIv”(a)=kv(a) c. v”(a)=0, EIv”(a)= -kv(a) d. v(a)=0, EIv”(a)= -kv(a)(MPa)4. (4 points) A stress cycle is shown in Fig. 3, the character of cycle r = , the mean stress = , the amplit

4、ude of stress = .5. (4 points) For two beams made of same material, the correct relationship for their maximum dynamic stresses is . 1d1d2； (4) Cannot be judged. 6. (4 points) Weight of the body is W, and pushing force is P. W=160N, P=500N. The static and kinetic sliding friction coefficients betwee

5、n the weight and the wall are S=0.3 and k=0.25 respectively. Then the friction between the weight and the wall is a. 150N; b. 125N; c. 100N; d. 500N. 7. (4 points) The bars in the structures as following are made of same material and with same diameter. | NBC1| _ (, =, , =, , =, , =, ) PCr2.7. (4 po

6、ints) For two beams made of same material, the correct relationship for their maximum dynamic stresses is . 1d1d2； (4) Cannot be judged. II (13 points) For a beam shown in Fig. II, draw its bending moment and shear force diagrams.Fig. II.III (10 points) Using the method of composite areas, calculate

7、 centroidal principal moments of inertia and for the shaded region as shown in Fig. III. Fig. III.IV (15 points) For the static indeterminate beam, find the reaction at B with energy method. is known。 V. (20 points) A horizontal bracket ABC is fixed at support A and free at C. The bracket is constru

8、cted from a circular cross-sectional bar with constant diameter d. A vertical load P acts at the free end C. (1) Determine the places of the critical points. (2) Draw stress elements to show the stress state of the critical points. (3) If d = 30mm, a = 1m, P = 180N and the allowable stress is = 80MP

9、a, exam the strength of the bracket according to the 3th strength condition.VI. (12 points) For the prismatic bar, taking its weight in consideration, find the displacement of section B. Loading F, l, cross section area A, elastic modulus E and mass density are known.C卷 中国石油大学北京20112012学年第一学期 工程力学双语

10、期末考试试卷考试方式闭卷考试班级： ： 学号： 题号IIIIII IVV总分得分 试卷不得拆开，所有答案均写在题后相应位置I (Total 40 points) Fill up the blanks with correct answer.1. (5 Points)Fig. I.1 is a typical low-carbon steel - diagram in tension. Such a diagram conveys important information about the mechanical behavior for the material. Point a repre

11、sents _, point b represents _, point c represents _, point d represents _, point e represents _. (1) yield stress (2) ultimate stress (3) elastic limit (4) percent elongation (5) proportional limit Fig.I.12. (5 points) A piece of chalk shown in Fig. I.2 is subjected to a combination of twisting and

12、tension, fails on the -degree plane with the longitudinal axis. The senses of the torques and axial forces must be indicated as shown in Fig. .Fig. I.23. (5 Points) For a real member undergoing repeated stress, its character of cycle r= . When r = , its endurance limit is the smallest. a. b. c. +1 d

13、. 1 e. 0 f. g. 0.54. (5 points) The boundary conditions on left end for a beam as shown are .a. v(a)=0,EIv”(a)=kv(a) b. v(a)=0, EIv”(a)=kv(a) c. v”(a)=0, EIv”(a)= -kv(a) d. v(a)=0, EIv”(a)= -kv(a)5. (5 points) When a train pass through a steel bridge, the strains tested by instrument are x = 0.0004,

14、 y = -0.00012 at point A. The normal stresses in directions x and y at point A are x = , y = . (E=200GPa, =0.3, z=0) 6. (5 points) For two beams made of same material, the correct relationship for their maximum dynamic stresses is . 1d1d2； (4) Cannot be judged. 7. (5 points) Weight of the body is W,

15、 and pushing force is P. W=160N, P=500N. The static and kinetic sliding friction coefficients between the weight and the wall are S=0.3 and k=0.25 respectively. Then the friction between the weight and the wall is a. 150N; b. 125N; c. 100N; d. 500N. 8. (5 points) The bars in the structures as follow

16、ing are made of same material and with same diameter. | NBC1| _ (, =, , =, ) PCr2. II (15 points) For a beam shown in Fig. II, draw its bending moment and shear force diagrams. Fig. II.III (15 points) In figure there is a manual winch. The diameter of the steel shaft is d=30mm and the allowable stre

17、ss is = 80MPa. Find the maximum load for the winch, according to the 4th strength condition.IV (15 points)A rigid bar AB of length L is hinged to a wall at A and supported by two vertical bars labeled 1 and 2 attached at points C and D. The bars 1 and 2 have the same cross-sectional area A and are m

18、ade of the same material (modulus E), but the bar 2 is twice as long as the bar 1. (a) Find the tensile forces N1 and N2 in the bars due to the vertical load P acting at end B of the bar. (b) Find the downward displacement B at end B of the bar. V. (15 points) Find the reaction at the support B for the beam with loads as following. (Energy Method recommended)