Effect of Casting Defects on Mechanical Properties of Steel Structures with Cast Steel Joints
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摘要:为了研究铸钢件中铸造缺陷的等级大小、位置分布对其静力性能、疲劳性能的影响，通过Solidworks软件建立了包含铸钢节点的钢桁架结构的实体模型，根据已有研究成果确定了铸钢节点上缺陷的尺寸与位置；对带有不同铸造缺陷的桁架结构进行静力加载，通过分析结构的应力分布、位移分布情况确定铸造缺陷对其静力强度、静力刚度的影响；对带有不同铸造缺陷的桁架结构进行等幅疲劳加载，通过铸钢节点的修正应力疲劳寿命（ S- N）曲线求得模型的局部疲劳寿命，明确铸造缺陷对结构疲劳性能的影响. 研究结果表明：当铸钢节点的不同位置含有相同大小的铸造缺陷时，不同模型的应力极值最大相差11.7%，不同模型的疲劳寿命相差两个数量级；当铸钢节点的同一位置含有不同大小的铸造缺陷时，不同模型的应力极值最大相差1.7%，不同模型的疲劳寿命相差一个数量级；以上两种情况对结构整体和局部的位移分布均没有明显影响；当铸钢节点中铸造缺陷的分布发生变化时，不同模型间应力极值的变化率为8.8%，不同模型的疲劳性能均劣于只包含单个铸造缺陷的模型.Abstract:In order to study the influence of the grade size and position distribution of casting defects on the static and fatigue properties of steel castings, firstly, a three-dimensional solid steel truss model with cast steel joints was built by Solidworks, and the size and location of casting defects on the cast steel joints were determined based on the published literature; then, the truss structures containing different casting defects were subjected to static loading, and the stress distribution and displacement distribution of the structure were analyzed to determine the influence of casting defects on its static strength and static stiffness; finally, the truss structures with different casting defects were subjected to equal amplitude fatigue loading, and the local fatigue life of the model was obtained through the modified S- Ncurve of the cast steel joint to clarify the effect of casting defects on it fatigue performance. The results show that when the different positions of the cast steel joints contain casting defects with the same size, the maximum difference in maximum stress of different models is 11.7%, the fatigue life of the different models differs by two orders of magnitude. When the same position of the cast steel joint contains casting defects of different sizes, the maximum difference in maximum stress of different models is 1.7%, the fatigue life of the different models differs by one orders of magnitude. In spite of the different positions of the cast steel joints contain casting defects with the same size or the same position of the cast steel joint contains casting defects of different sizes, there is no significant effect for the overall and local displacement distribution of the structure. When the distribution of casting defects in the cast steel joint changes, the rate of change of maximum stress between different models is 8.8%, the fatigue performance between different models is inferior to the model that only contains one casting defect.
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Key words:
- cast steel joint/
- defect/
- mechanical property/
- casting quality evaluation
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图 3缺陷位于位置 ② 时钢桁架结构应力云图
Figure 3.Stress cloud diagram of the steel truss structure when the defect is at ②
表 1有限元模型的网格尺寸划分
Table 1.Mesh size of the finite element model
mm 模型分区 第 1 套 第 2 套 第 3 套 第 4 套 工字梁 50 79 79 100 钢管 15 20 30 40 铸钢节点 10 15 20 30 缺陷位置 1 2 4 5 
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表 2集中载荷作用下各模型的应力极值
Table 2.Maximum stress of each model under concentrated load
模型 铸造缺陷
位置铸造缺陷
等级Mises应力
最大值/MPa1 ① 2级 200 2 ① 3级 202 3 ② 2级 182 4 ② 3级 182 5 ③ 2级 182 6 ③ 3级 182 7 ④ 2级 180 8 ④ 3级 183 9 ⑨ 2级 200 10 ⑨ 3级 200 下载:
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表 3不同模型的应力极值
Table 3.Maximum stress of different model
模型 铸造缺陷位置 铸造缺陷
等级Mises应力
最大值/MPa11 ①、②、③ 2级 182 12 ①、③、④ 2级 198 13 ②、⑦、⑨ 2级 182 14 ④、⑤、⑥ 2级 183 15 ①、②、③、⑧、⑨ 2级 186 下载:
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表 4各缺陷位置处的尺寸系数
Table 4.Size factor at defect locations
缺陷位置 ①、⑨ ②、④、⑧ ③、⑤ ⑥ ⑦ 尺寸系数 0.95 0.90 0.83 0.82 0.80 下载:
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表 5缺陷位置对模型疲劳寿命的影响
Table 5.The effect of defect location on fatigue life of models
模型 铸造缺
陷位置铸造缺
陷等级疲劳寿命/
（× 105周次）A ① 2级 2.43 B ② 2级 3.49 C ③ 2级 1.91 D ④ 2级 — E ⑤ 2级 — F ⑥ 2级 — G ⑦ 2级 — H ⑧ 2级 49.4 I ⑨ 2级 23.65 注：—表示应力幅低于修正后的疲劳极限，达到无限寿命. 下载:
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表 6缺陷等级对模型疲劳寿命的影响
Table 6.The effect of defect size on fatigue life of models
模型 铸造缺
陷位置铸造缺
陷等级疲劳寿命/
（× 105周次）J ① 3级 0.55 K ③ 3级 0.68 L ④ 3级 — M ⑨ 3级 2.90 注：—表示应力幅低于修正后的疲劳极限，达到无限寿命. 下载:
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表 7缺陷分布对模型疲劳寿命的影响
Table 7.The effect of defect distribution on fatigue life of models
模型 铸造缺
陷位置铸造缺
陷等级疲劳寿命/
（× 105周次）N ① 2级 0.34 ② 2级 1.64 ③ 2级 1.64 O ① 2级 0.32 ③ 2级 1.64 ④ 2级 — P ② 2级 1.52 ⑧ 2级 — ⑨ 2级 8.67 Q ① 2级 0.36 ② 2级 1.64 ③ 2级 1.64 ⑧ 2级 — ⑨ 2级 8.67 注：—表示应力幅低于修正后的疲劳极限，达到无限寿命. 下载:
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