问题
问答题 简答题
简述疲劳腐蚀的外形特征。
答案
参考答案：
疲劳腐蚀的外形特征是：有许多深蚀孔，裂缝通过蚀孔可以有若干条。
方向和应力垂直，是典型的穿晶型，没有分支裂缝，缝边呈现锯齿形。
振动部件如泵轴和泵杆、螺旋浆轴、油气井管、吊索以及由于温度变化产生周期热应力的换热管和锅炉管等，都容易产生疲劳腐蚀。
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简述疲劳腐蚀的外形特征。
参考答案：
疲劳腐蚀的外形特征是：有许多深蚀孔，裂缝通过蚀孔可以有若干条。
方向和应力垂直，是典型的穿晶型，没有分支裂缝，缝边呈现锯齿形。
振动部件如泵轴和泵杆、螺旋浆轴、油气井管、吊索以及由于温度变化产生周期热应力的换热管和锅炉管等，都容易产生疲劳腐蚀。
I was doing a big clean-up and my kids were helping. One of my sons came across a handkerchief of mine with a coin inside. I took one look and was immediately to another time． In 1991，I had spent five months in Viger(尼日尔)，a hot African country. There were many things I found about this place—the climate and beggars who shouted “Cadeau! Cadeau!” It means gift． One was a lot worse．One day，a friend and I headed for neighboring Burkina Faso to work in a health clinic．However，a motorbike with two men slowly．Without warning，one of the men my backpack as the motorbike swept close by．The bag had my passport，money，an airline ticket and other things precious to me．I was in deep ．In the weeks that followed I looked at all with suspicion. All I wanted was to leave this place．One day，I was stopped by an old woman “Cadeau!” she cried. I’d had enough! I was sick and tired of the country．I told her firmly，“A thief stole all my money and now I can’t get off your country.” The beggar woman listened carefully and my words． “Then I will give you a cadeau,” she announced．Kindly，she placed an old brown coin in my palm. I looked at it ．Living in poverty，she gave me something priceless! I saw then the beauty of the people of Burkina Faso and deeply the quiet dignity of the small coin；she turned my perceptions upside down．
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