Engineering mechanics (II) (material)spring online homework

1、Engineering mechanics (II) (material) 13 spring online homework 214, autumn, landa, engineering mechanics (II)14, spring 13, engineering mechanics (material) 13 spring online homework 2, 3, 1Exam time: 100 test time:Single topic selectionMultiple choiceTrue or false(10 questions in total, 40 points.

2、)A round cross-section is the same as the pull on both ends. If the diameter is doubled, the other condition is the same.The axial force is constantStress invariantstiffnessD. the elongation is constantFull marks: 42. A solid shaft with circular cross section, the diameter of D1, another for hollow

3、circular shaft diameter D2, alpha = 0.8, if the two shaft torque and maximum shear stress on the cross section of equal, respectively, D1, D2 = ().A. 0.839B. 0.59C. 0.768D. 1.19Full marks: 4Strength, stiffness, and stability of the components.A. it only has to do with the mechanics of the materialB.

4、 Only the shape of the componentC. it has to do with bothD. it has nothing to do with eitherFull marks: 4Flexible constraints only limit the movement of objects along flexible constraints ().elongationShorten directionVertical directionDFull marks: 4The stress-strain curve of low carbon steel stretc

5、hes can be roughly divided into four phases, which are ().The stage of elastic deformation, the plastic deformation stage, the yield stage and the fracture phaseB. elastic deformation stage, plastic deformation stage, strengthening stage and neck contractionC. elastic deformation stage, yield stage,

6、 reinforcement stage, fracture stageD. elastic deformation stage, yield stage, reinforcement stage, and neck contractionFull marks: 4In the main plane of the cell.The positive stress must be greatestThe positive stress must be zeroC. shear stress must be minimalThe stress must be zeroFull marks: 4Wh

7、en the hollow cylinder is stretched by the shaft, if the lever is in the elastic range, the cross section is transformed into ().A. the diameter and thickness of the wall are enlargedB. the diameter and thickness of the wall are reducedC. The diameter is decreased and the wall is thickerD. The diame

8、ter increases and the wall decreasesFull marks: 4The condition that the component should be satisfied when working properly is: ().The component does not break upThe balance in the original form of the component is stableC. members have sufficient resistance to deformationD. the component has suffic

9、ient strength, stiffness and stabilityFull marks: 4The following statement about the application scope of the equation of flat bending positive stress, which is correct ().A. The slender beam and the elastic range are loadedThe load and load are added to the surface of a symmetrical surface or main

10、shaftC. slender beam, elastic range, load and load on symmetrical surface or main shaft planeThe long beams and loads are added to the surface of a symmetrical surface or main shaftFull marks: 4The allowable stress sigma of the component is the ().A. maximum working stressB. Minimum working stressC.

11、 Average working stressFull marks: 414, spring 13, engineering mechanics (material) 13 spring online homework 2, 3, 1Exam time: 100 test time:Single topic selectionMultiple choiceTrue or false(the total number of five questions is 20 points.)A two-state stress state is superimposed on the state of t

12、he other two, and the following conclusion is correct ().The result must remain A two-state stress stateB. The result is a three-way stress state if it is not a two-state stress stateThe result may be two stress states or three stress statesThe result may be one direction, two or three stress states

13、Full marks: 4The following conclusion is correct ().A. plane while the outside force action through the centroid cross section, but as long as it is with any cross section of the centroid axis is not parallel, then, the beam will be the combination of plane bending and torsion deformationThe neutral

14、 axis in the cross section of a curve is a straight line through the center of the curveC. whether it is curved or oblique, the neutral axis always divides the cross section into two areas of tension and compressionD. tensile bar (compressed) and the combination of bending deformation, the sexual ax

15、is though is a not through the centroid of the straight line, but it will always in tension and compression of cross section is divided into size two areaFull marks: 4The factors that affect the working stress of the rod are ().A. the loadMaterial propertiesSection sizeWorking conditionsFull marks:

16、4In the following statements, the meaning of the critical force of the pressure bar is correct.The pressure value of the stress in the cross section of A pressure barThe pressure bar can maintain the maximum pressure value of a stable straight lineC. The minimum pressure value when the lever loses a

17、 stable straight lineD. The pressure value of the lever in the bending equilibriumFull marks: 4It is advantageous to design the main beam of the bridge crane as the extension beam of the two sides, the reason is ().A. Reduces the maximum bending moment value of the beamB. reduces the maximum shear v

18、alue of the beamC. reduces the maximum deflection value of the beamThe bending stiffness of the beam is increasedFull marks: 414, spring 13, engineering mechanics (material) 13 spring online homework 2, 3, 1Exam time: 100 test time:Single topic selectionMultiple choiceTrue or false(10 questions, 40

19、points.)1. In the six sides of unit cell, there are only four relative to the side of the stress, the rest of the two sides is no stress, the stress of each side and 4 action line and the two free parallel to the side, the stress state is called the state of plane stress.A. mistakesB. rightFull mark

20、s: 4The size of E is independent of the length of the rod.A. mistakesB. rightFull marks: 4Stress is positive when stress is stressed.A. mistakesB. rightFull marks: 4Adding or subtracting any force in a known force system does not change the role of the force in the rigid body.A. mistakesB. rightFull

21、 marks: 45.In the bending of the straight beam, the strength of the beam is determined by the size of the bending moment and the size of the bending section coefficient.A. mistakesB. rightFull marks: 4The effects of stress concentration on the stress concentration are not considered in the function of static load.A. mistakesB. rightFull marks: 4Mo