中国石油大学工程力学考试exam(2006_2007_1_80)(B).doc

中国石油大学（北京）20062007学年第1学期Engineering Mechanics期末考试试卷/BClass: Name： Registration No.： Score： No.IIIIIIIVVTotalScore Date: Jan. 12, 2007I. For the each question following, please choose a right answer. (5 Points/question). 1. The weight A and B are 100kN and 25kN respectively. Neglecting the friction at pulley, then the friction between weight A and earth is a. 20kN b. 16kNmS=0.2c. 15kNd. 12kN Fig. 12. Two forces act on a cubic frame with side length a as shown in Fig. 1. If this force system is reduced to an equivalent force-couple system acting at point O, the magnitude of the resultant couple is: a. ；b. ；c. ；Fig. 2d. 。3. 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. 1 e. 0 f. g. 0.54. For two slender compressing bars with same support conditions and made of same material but different cross sectional areas as show in Fig 3, PCr2= PCr1.2a2aa2aa. 4 b. 8 c. 12 d. 16 Fig.4 (1) Fig. 4 (2)5. If a circular bar in torsion fails along its cross section, it is made of _ material. If a circular bar in torsion fails along its section inclined at an angle 45, it is made of _ material. a. Ductile b. Brittle c. Cannot be judged. Fig. IIFig. 5 II. (15 points) Neglecting the weights of the members, determine the magnitude of the pin reaction at D when the frame is loaded by the 200-N.m couple.yIII. (20 points) Please solve one of (a) and (b).(a) The deflections and the rotation angles at x-section of three beams with flexural rigidity EI in Fig. III a are given as following. BAx q xyP Fig. III aAs shown in Fig. III b, a beam ABC (E1I1) rests on simple supports at A and B and is supported by a cable (E2A2) at point C. The beam has total length 2L and supports a uniform load of intensity q. Prior to the application of the load, there is no force in the cable nor is there any slack in the cable. When the load is applied, the beam deflects downward at point C and a tensile force T develops in the cable. Find the magnitude of this force.Fig. III b Fig III c BACqaabFig. IV b Fig. VI c(b) As in Fig. III c, a continuous frame ABC has a rigid corner connection at B. Members AB and BC each has flexural rigidity EI. The load is shown in the figure. Find all reactions of the frame (Only flexure is considered). IV. (25 points) A circular shaft (d=200 mm) with bending moment My and torque Mx is shown in the figure. Points A and B are on the surface of the shaft. From the test we know that the axial normal strain at A and the normal strain along 45 direction with axis at B are e0 = - 610-4 and e45 = 410-4 respectively. Let E=200GPa, n = 0.25 and sallow = 160 MPa. (a) Draw the stress element at A and B；（b）Find the magnitudes of My and Mx; (c) Exam the shaft with3th strength theory. zMy