问题 问答题 论述题

试分析影响工件圆度的因素主要有哪些?

答案

参考答案:

(1)、中心孔的形状误差或中心孔内有污物;

(2)、中心孔或顶尖因润滑不良而磨损;

(3)、工件顶得过松或过紧;

(4)、砂轮过钝;

(5)、切屑液供给不充分;

(6)、误差复映;

(7)、工件不平衡;

(8)、砂轮主轴轴承间隙过大;

(9)用卡盘装夹磨外圆时,头架主轴的径向跳动过大;

阅读理解

Every day we use money to buy what we want. But have you ever really noticed the bill (钞票) in your hand? There are different pictures on both sides of banknotes (纸币) and interesting stories behind them.

Most banknotes have famous people on the front, such as a country’s leader or a great scientist, while on the back of the paper note there are usually some well-known scenes or national buildings.

The latest editions of Chinese banknotes use the picture of Mao Zedong, founding father of the People’s Republic of China, on the front of all yuan bills. However, the backs of the bills are different. The Great Hall of the People, on the 100-yuan note, is a landmark (地标) in Beijing. Important meetings are always held there. The Lijiang River in Guilin, on the 20-yuan note, is one of the most beautiful scenes in the world.

The US 1-dollar bill has the first president, George Washington, on the front side. A 13-level pyramid is on the back. Benjamin Franklin, a great scientist and politician (政治家) from the US, appears on the front of the 100-dollar bill. You can see the White House, where the presidents live, on the back of the 20-dollar bill.

小题1:According to Paragraph 2, which one probably appears on the back of the banknotes?

A.Abraham Lincoln.

B.Elizabeth II.

C.Taishan Mountain.

D.Titanic.小题2:The Lijiang River of Guilin is __________.

A.on the back of 20-yuan note

B.on the front of 20-yuan note

C.on the front of 100-yuan note

D.on the back of 100-yuan note小题3:On the front of the 100-dollar bill, we can see __________.

A.George Washington

B.Benjamin Franklin

C.a 13-level pyramid

D.the White House

判断题