东大机械设计基础I复习题答案

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机械设计基础I复习题答案

二、计算题

计算图示机构的自由度，指出存在的复合铰链、局部自由度或虚约束判断该机构是否具有确定的运动，说明理由。

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image002.gif

解：E（F）为虚约束，D和B处存在局部自由度

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image004.gif  file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image006.gif

该机构具有确定的运动，主动构件数与自由度数相等。

三、计算题

图示轮系中，已知file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image008.gif，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image010.gif，齿轮1的转速file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image012.gif，求file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image014.gif及行星架的转速file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image016.gif 时齿轮3的转速file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image018.gif。

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image020.gif

解：该轮系为一差动轮系。

     （1）根据同心条件，轮1和轮2的中心距应等于轮3和轮2的中心距，对于标准齿轮，相啮

合的齿轮模数相等，故

          file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image022.gif，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image024.gif，则有

         file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image026.gif，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image028.gif

     （2）当file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image016.gif时，即行星架H固定，该轮系成为定轴轮系，

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image030.gif,file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image032.gif

       齿轮3的转向与齿轮1的转向相反。

四、计算题

    图示为单个普通螺栓连接，当螺栓的预紧力为file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image034.gif时，试写出被连接件

所能承受的横向力file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image036.gif的表达式，并说明式中各符号的意义。

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image038.jpg

           解：根据不滑移条件，可知

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image040.gif    所以，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image042.gif，

式中，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image034.gif为预紧力，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image045.gif为接合面间的摩擦系数，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image047.gif摩擦接合面数，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image049.gif螺栓个数，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image051.gif可靠性系数，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image036.gif横向外载荷。题中，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image054.gif，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image056.gif，故    file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image058.gif

五、计算题

图示为轴系由一对30208滚动轴承支承。已知：轴向外载荷file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image060.gif，径向载荷分别为file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image062.gif，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image064.gif，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image066.gif。冲击载荷系数file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image068.gif，工作温度为100℃。轴承数据为file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image070.gif，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image072.gif，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image074.gif，派生轴向力file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image076.gif。file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image078.gif时，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image080.gif，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image082.gif；file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image084.gif时，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image086.gif，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image074.gif。试求该轴承寿命L10h。

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image089.gif

解:（1）计算派生轴向力file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image091.gif、file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image093.gif

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image095.gif，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image097.gif

（2）计算轴向载荷file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image099.gif、file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image101.gif

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image103.gif，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image105.gif

（3）计算当量动载荷file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image107.gif、file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image109.gif

       file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image111.gif，

        file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image113.gif

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image115.gif

    （4）计算轴承寿命file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image117.gif

     file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image119.gif，故按照轴承1计算，file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image121.gif

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image123.gif

六、分析题

图示为蜗杆——斜齿圆柱齿轮传动，蜗杆主动，右旋，转向如图。为使Ⅱ、Ⅲ轴上的轴向力方向相反。

试求：

（1）蜗轮的螺旋线方向；

（2）齿轮3、4的螺旋线方向；

（3）蜗轮2、齿轮3的受力分析。

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image125.gif

file:///C:/Users/ADMINI~1/AppData/Local/Temp/msohtmlclip1/01/clip_image127.gif