This paper introduces the reinforced concrete crack types and causes, from material factor, design factors and external factors three aspects discusses the specific methods of preventing the crack.

本文介绍了钢筋混凝土裂缝类型及产生原因，从材料因素、设计因素和外界因素三方面论述了预防裂缝的具体方法。

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It was indicated that the linear defect appeared after machining is not crack, it is the appearance of oxide film involved in the casting under the effect of external force.

结果表明，这种加工后出现的线性缺陷并非裂纹，而是卷入铸件的氧化膜受外力作用后在叶片表面的显现。

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The results showed that nonmetallic inclusions in weld seam served as crack initiation site under external bend load, and large amount of m a structure resulted in cleavage fracture of weld seam.

结果表明，焊缝金属中存在的非金属夹杂物，在低应力作用下形成微裂纹成为裂源，加之焊缝组织中存在大量的M A结构群，从而发生焊缝金属在室温下的解理断裂。

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