Theory of Machine and Mechanisms - 中国大学mooc

Chapter 1 Introduction

Chapter 1 Unit Test

1、The term “synthesis” differs from “design” which is the process of prescribing the size, shape, material compositions, arrangements of parts, calculations of strength, methods of production, etc.

2、Mechanisms used in machines which have different functions and profiles may be the same.

3、The radii of the holes and the cross-section areas of the links are the kinematics dimensions.

4、Machine is a mechanical system that can transmit or transform energy, materials or information.

5、Almost all machines contain only one basic mechanism.

Chapter 2 Structural Analysis of Planar Mechanisms

Chapter 2 Unit Test

1、In the following choices, which one is a planar higher pair?
    A、
    B、
    C、
    D、

2、In the following single-cylinder four-stroke internal combustion engine, which part is an output link?
    A、2
    B、3
    C、4
    D、5

3、In the following mechanisms, which one has not redundant DOF.
    A、
    B、
    C、
    D、

4、In the following mechanism, the DOF of the mechanism is .
    A、0
    B、1
    C、2
    D、3

5、In the following mechanisms, whose DOF differ from others.
    A、
    B、
    C、
    D、

6、If the compound pair contains K links, the number of revolute joints is .
    A、K-2
    B、K-1
    C、K
    D、K+1

7、In the following mechanism, it has redundant constraints.
    A、0
    B、1
    C、2
    D、3

8、In the following mechanism, in order to have a determined motion, the mechanism needs to have driving link(s).
    A、1
    B、2
    C、3
    D、4

9、In the following choices, which one cannot be deleted before the calculation of the DOF of a mechanism?
    A、compound pairs
    B、passive DOF
    C、redundant constraints
    D、all of the above

10、In the following mechanism, the mechanism has redundant constraint(s) and DOF.
    A、2，3
    B、2，1
    C、0，3
    D、0，1

Chapter 3 Kinematic Analysis of Planar Mechanisms

Chapter 3 Unit Test

1、How many instant centers in the mechanism below?
    A、5
    B、6
    C、7
    D、8

2、How many instant centers in the mechanism below?
    A、3
    B、4
    C、5
    D、6

3、The cam mechanism below has the dimensions: R=50mm, lOA=20mm,lAC=80mm, j1=90 degree. Cam 1 rotates at a constant angular velocity of w1 = 10 rad/s. counterclockwise. P12 is an instant center. The angular velocity w2 of follower 2 is equal to:
    A、
    B、
    C、
    D、

4、The velocity vector polygon and acceleration vector polygon of the link are similar to the shape of the link.

5、The method of instant center can be applied to calculate velocity and acceleration.

6、Kinematic analysis only involves the analysis of velocity and acceleration.

7、For a high pair, the contact point is the instant center.

8、For a planar mechanism, the number of instant centers can be calculated by the equation , where k is the number of links in the mechanism.

9、Instant centers can be classified into _______ and _______.

10、The instant center of a revolute pair in a planar mechanism is _________.

11、Relative motion graphic method is based on two theories,_____________ and ___________.

12、For relative motion graphic method, the velocity vector starting from the polar point is __________, while the velocity vector connecting two kinematic pairs is ________.

13、As for the sliding pair in a planar mechanism, the location of instant center is located at ______________.

Chapter 4 Planar Linkage Mechanisms

Chapter 4 Unit Test

1、Determine the type of the linkage and type of the two side links AB and DC (crank or rocker) according to the Grashof criterion. Can the coupler BC rotates 360° with respect to the frame? LAB = 80mm, LBC = 20mm, LDC = 45mm, LAD = 60mm
    A、Double crank mechanism
    B、Double rocker mechanism
    C、Crank -rocker mechanism
    D、Slider-crank mechanism

2、Determine the type of the linkage and type of the two side links AB and DC (crank or rocker) according to the Grashof criterion. Can the coupler BC rotates 360° with respect to the frame? LAB = 20mm, LBC = 45mm, LDC = 70mm, LAD = 90mm
    A、Double crank mechanism
    B、Double rocker mechanism
    C、Crank -rocker mechanism
    D、Slider-crank mechanism

3、Find the name of the mechanism
    A、Slider-crank mechanism
    B、Rotating guide-bar mechanism
    C、Swing guide-bar mechanism
    D、Crank and oscillating block mechanism

4、In a revolute four-bar linkage in the following figure,LBC=100mm, LCD=80mm,LAD=110mm. Find the range of the values for the length of link AB if the linkage is a crank-rocker mechanism with crank AB, ______________
    A、
    B、
    C、
    D、

5、In a revolute four-bar linkage in the following figure, LBC=100mm, LCD=80mm,LAD=110mm. Find the range of the values for the length of link AB if the linkage is a double-rocker mechanism, and AB is the shortest link, ____
    A、
    B、
    C、
    D、

6、In a revolute four-bar linkage in Fig. 4-1, LBC=100mm, LCD=80mm,LAD=110mm. Find the range of the values for the length of link AB if the linkage is a double-rocker mechanism, and AB is the longest link, ______
    A、
    B、
    C、
    D、

7、In a revolute four-bar linkage in Fig. 4-1, LBC=100mm, LCD=80mm,LAD=110mm. Find the range of the values for the length of link AB if the linkage is a double-rocker mechanism, and AB is neither the shortest nor the longest link, ______
    A、
    B、
    C、
    D、

8、Determine the type of the linkage and type of the two side links AB and DC (crank or rocker) according to the Grash of criterion. The coupler BC rotates 360° with respect to the frame. LAB = 45mm, LBC = 50mm, LDC = 60mm, LAD = 20mm

9、The function of a linkage mechanism is to transform the Continuous rotation into continuous rotation, with a constant or variable angular velocity ratio.

10、The function of a linkage mechanism is to transform the Continuous rotation into oscillation or reciprocation (or the reverse), with a constant or variable velocity ratio.

11、The planar linkage mechanisms have the advantage of great ability to trap lubricant between enveloping surfaces. Therefore, the contact pressure and wear between two links are low.

12、For the planar linkages, the balance design and analytical calculation are very easy.

13、ABCD is a crank -rocker mechanism,,shown in Fig.1 If the side link DC is a driver, γis γmin at this position, shown in Fig.2. Fig. 1 Fig. 2

14、This mechanism has quick-return characteristics.

15、An offset slider-crank mechanism is shown in following figure. the crank AB is a driver which runs at a constant speed. lAB=e=10mm, lBC=50mm. (1)Calculate the minimum and maximum pressure angle, amin= ____°and amax=_____°. (2)If the slider needs a higher speed in its rightward stroke than in leftward stroke, which rotation direction will the crank AB take?(clockwise or anticlockwise) ________ (3) Find the crank acute angle between two limiting positions q=_____°

16、In a revolute four-bar linkage in the following figure, LBC=100mm, LCD=80mm,LAD=110mm. Can the linkage be a double-crank mechanism by adjusting the length of LAB ？(Yes or No)____________Why?___________