Test paper of《Mechanisms and Machine Theory》for Grade 00
I. Choose the correct answer and fill the corresponding letter in the bracket (5 %) 1. The proper meshing conditions for a pair of spur gears are ( B )
A. The modules of both gears are equal
B. The modules and pressure angles of both gears are equal respectively. C. Independent of the modules and pressure angles of both gears. 2. The modification coefficients of a pair of spur gears are x1 = 0.54 and x2 = ?0.75. The working pressure angle ?’ of this pair of gears must be ( C ) A. ?’ > ? = 20? B. ?’ = ? = 20? C. ?’ < ? = 20? 3．If a mechanism has quick return characteristics, its coefficient of travel speed variation k must be( B ) A. K>0 B. K>1 C. K<1
4. The standard parameters of a helical gear are defined on ( B )
A. The transverse plane B . The normal plane C. The axial plane 5. A straight bevel gear has the teeth number Z and reference cone angle ?. Its virtual number of teeth Zv is ( B )
A. Zv = Z/sin? B. Zv = Z/cos3? C. Zv = Z/cos? II. Fill the proper content in the blank (16％)
1. The conditions for a mechanism to have a determined motion are 自由度大于0且dof=主动杆数 2. The condition for static balancing of a rotor is The conditions for dynamic balancing of a rotor is 3. The cause of the periodic speed fluctuation of a machine is 4. A flywheel, if needed, should be mounted on a shaft with higher speed in a machine. The reason is .
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5. The conditions for a revolute four-bar linkage to become a double-crank
mechanism are 6. Consider cutting a spur gear with a rack-shaped cutter. Compared with the case as modification coefficient X = 0, are the following dimensions of a spur gear greater, smaller or unchanged when X > 0 ?
The dedendum hf is _____________, the diameter of the reference circle d is _______________, the diameter of the base circle db is _______________, the tooth thickness on the reference circle s is _____________, the pitch on the reference circle p is ______________, the base pitch pb is _____________.
7. If a planar mechanism has N links altogether, the mechanism will has (N-1) absolute instant centers and N*(N-1) /2 relative instant centers. 8. When the point on an involute curve moves towards its base circle, the radius of curvature of the involute curve___________________(increases or decreases) and the pressure angle ________________ (increases or decreases). III、Questions：
1. Besides crank-rocker mechanism, list and draw the schematic diagrams of another two mechanisms which can transform a continuous rotation into an oscillation(4%).
2. Besides slider-crank mechanism, list and draw the schematic diagrams of
another three mechanisms which can transform a continuous rotation into a translation back and forth(6%).
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3. Can the kinematic chain shown below become a mechanism? If not, please do
some modification so that it can become a mechanism. Draw the schematic diagrams of the new mechanism.(3%)
4. In the slider-crank mechanism shown below, crank AB is a driver. The slider 3
translates back and forth. Please generate a new mechanism by holding another link fixed as the frame, so that the new mechanism can transform a continuous rotation into an oscillation. Draw the schematic diagrams of the new mechanism. (3%)
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00级MMT期末考卷TestpaperofMechanismsandMachineTheory
