问题 问答题 简答题

摩擦副表面层设计

答案

参考答案:

一般设计准则在摩擦学设计中,摩擦副的耐磨层薄膜(包括单层连续梯度膜和多层梯度膜)通常有三种设计法则。摩擦副若是粘着磨损为主,则采用互溶性孝化学活性强而抗剪切强度低的表面层,即用抗剪切强度正梯度法则设计。摩擦副若是磨粒磨损为主,则采用非常硬的表面,如TiC,TiN及表面淬硬层等,即采用表面硬度负梯度法则设计。摩擦副若是几种摩擦磨损过程混合的情况,即采用强度正梯度法则-硬度负梯度法则的复合梯度法则设计。

阅读理解

阅读理解。

     My friend, Dick, has a large police dog. Its name is Jack. Every Saturday afternoon, Dick takes Jack for a long walk in the park. Jack likes these long walks very much. One afternoon,a young man came to visit my friend.  He stayed a long time.  He talked and talked.  Soon it was time for my friend to take Jack for a walk.  But the man was still there. Jack became very worried. He walked around the room several times and then sat down in front of the man and looked at him. But the man kept talking. Finally Jack couldn't stand it. He went out of the room and came back a few minutes later.  He sat down again in front of the man, but this time he held the man's hat in his mouth.

根据短文内容,选择正确答案。

1. From the story, we know that Jack is______.

A. Dick's good friend

B.a large police dog

C.a young man

D.the young man's dog

2. Where does Dick walk his dog every Saturday afternoon?

A. In his room.

B.In the street.

C. In the park.

D.In the field.

3. Jack became very worried one afternoon because______.

A. Dick couldn't take him out for a walk at the usual time

B. a young man cameto visit Dick that afternoon

C. Dick walkedaround his room several times

D. he couldn't find the young man's hat

4. What does the underlined word“stand"mean in the passage? It means ______in Chinese.

A. 站立

B. 理解

C. 支持

D. 忍受

5. Why did Jack sit down again in front of the man with the hat in his mouth?

A. He tried to make the man laugh.

B. He liked the young man very much.

C. He asked the young man to leave.

D. He wanted to talk with the young man.

单项选择题