问题 问答题 简答题

简述滚动轴承的工作条件及对滚动轴承钢的要求。

答案

参考答案:

滚动轴承的工作条件有两个方面:一是滚动轴承与座圈之间为接触应力极高的点(或线)接触,接触应力高达(1500-5000)MPa;二是轴承作为一个滚动体,轴承表面各点忍受着频率极高(数十万次/min)的压缩-拉伸循环载荷。另外,轴承还会受到一定的冲击载荷作用。

作为制造滚动轴承的座圈和滚动体用钢,应满足下列要求:高的淬硬性(61-65)HRC和淬透性;高的弹性极限和接触疲劳强度;服役期间尺寸稳定,有较高的抗润滑油及大气腐蚀能力。

阅读理解

[1] Scientist proves better busy than doing nothing, research has found. Keeping the mind occupied with tasks—no matter how meaningless—keeps off negativeemotions, the study found.

[2] However, the bad news is that humans seem born to be lazy in order to save energy, according to Professor Christopher Hsee, a behavioural scientist at Chicago University.

[3] In a study 98 students were asked to complete two surveys. After they had completed the first they were made to wait 15 minutes to receive the next one. They were given a choice of either handing in the first survey nearby or at a more distant location they had to walk to. Whichever choice they chose, they received a chocolate bar. Two-thirds (68 per cent) chose to take a shortcut. Those who had taken the walk reported feeling happier than those who had stayed put. Prof Hsee concluded __________________ helped keep people happy.

[4] He said the findings, reported in the journal Psychological Science, had policy guidance. "Governments may increase the happiness of idle(闲散的)citizens by having them build bridges that are actually useless", he suggested.

[5] At the individual level, he advised: "Get up and do something. Anything. Even if there really is no point to what you are doing, you will feel better for it." He added, "By the way, thinking deeply or busy with self-reflection counts as keeping busy, too. You do not need to be running around—you just need to be busy, either physically or mentally."

小题1:What is the purpose of the text? (no more than 8 words)

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小题2:Why did two-thirds (68 per cent) choose to take a shortcut? (no more than 8 words)

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小题3:Fill in the blank in Paragraph 3 with proper words. (no more than 2 words)

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小题4:What does the word “it” in Paragraph 5 probably refer to? ( no more than 2 words)

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小题5:What is the main idea of the last paragraph? (no more than 10 words)

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