Fracture Toughness Assessment of Weld Toes by Means of Simple Model Testing

通过简单模型测试评估焊趾的断裂韧性

• 批准号: 07555178
• 负责人: KUROBANE Yosihiaki
• 金额: $ 6.34万
• 依托单位: Kumamoto University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07555178/
• 关键词: Weld Toe; Brittle Fracture; Fibrous Crack; Crack Opening Displacement; J Integral; Finite Element Analysis; Earthquake Resistant Design; Strain Rate; 延性きれつ; きれつ開口変位; ひずみ速度

Welded T joint speciments were tested in combined bending and tensile loads. The specimens were tested by varying the material properties, thickness of the main plate, methods of prestraining the main plate, and temperature. A few specimens were tested after introducing fatigue cracks along the weld toes. The first crack was found in the central region of the main plate at te weld toes. This crack extended stably not only along the weld toes but also in the through thickness direction. Some specimens failed suddenly, at a certain stage, showing an unstable crack extension, while other specimens failed y ductile tear. The greater the plate thickness, the larger the prestrain, and the lower the temeprature, the specimens failed in a more brittle manner. The intitation of macrocracks, of about 0.1 mm in depth, was found to be predictable by a simple function of stress triaxiality, Mises's equivalent plastic strain and maximum uniform strain of material. This function is based on the conti … More nuum damage theory. The ductile cracks gave no appreciable effect on load-deflection curves, which can be reproduced accurately by a nonlinear finite element analysis, until they reach about 0.5 to 2.5 mm in depth, as far as they grow stably. After that, the cracks grow rather quickly, leading to ductile or brittle failures. The load-deformation curves leading to a final fracture following quick extensions of cracks have been unable to reproduce by any numerical technique.A crack tip is blunted and a new crack forms at the root of the tip. This behavior was found to be reproducible by an FE analysis. Study is now under way to find feasible numerical methodologies to control crack growth by using appropriate fracture parameters like the J integral or COA.The failure assessment diagram was found to be one feasible method to predict failures of welded joints with defects.The Kobe Earthquake revealed that modern steel building frames could sustain brittle fracture under the influence of a strong near field earthquake. Lessons learned from recent earthquakes were included as the subject of study of this research project. Above all brittle fractures that occurred in box section columns of high-rise Ahiyahama apartment buildings were investigated. Although several causes should have been combined to induce such failures, the effect of high strain rate was found to be one important cause. Additionally, a cyclic loading test of full-scale beam-to-column assemblies were performed to assess effects of weld defects. The test results pointed out the significance of geometry and location of defects in influencing the performance of the connections. Less

对焊接T型接头试件进行了弯曲和拉伸复合载荷试验。通过改变材料特性、主板厚度、主板预应变方法和温度对试样进行测试。在沿焊趾沿着引入疲劳裂纹后，对几个试样进行了试验。第一条裂纹出现在焊趾处的主板中心区域。该裂纹不仅沿着焊趾而且沿厚度方向稳定地扩展。有些试件在某一阶段突然破坏，表现为不稳定的裂纹扩展，而另一些试件则以韧性撕裂破坏。板厚越大，预应变越大，温度越低，试样的破坏方式越脆。宏观裂纹的起始深度约为0.1 mm，可以通过应力三轴度、Mises等效塑性应变和材料的最大均匀应变的简单函数来预测。此功能基于conti ...更多信息 自然损害理论。韧性裂纹对载荷-挠度曲线没有明显的影响，这可以通过非线性有限元分析准确地再现，直到它们达到约0.5至2.5 mm的深度，只要它们稳定地生长。在此之后，裂纹迅速扩展，导致韧性或脆性破坏。裂纹快速扩展导致最终断裂的载荷-变形曲线无法用任何数值方法再现，裂纹尖端被钝化，在尖端根部形成新的裂纹。通过FE分析发现这种行为是可再现的。目前正在研究通过使用合适的断裂参数如J积分或COA来控制裂纹扩展的可行数值方法。失效评定图被发现是预测含缺陷焊接接头失效的一种可行方法。科比地震揭示了现代钢结构建筑框架在强近场地震影响下可以承受脆性断裂。从最近的地震中吸取的教训被列为这一研究项目的研究主题。首先，对高层芦屋滨公寓楼箱形截面柱的脆性断裂进行了研究。虽然几个原因应该已经结合起来，以诱导这种故障，高应变率的影响被认为是一个重要的原因。此外，进行了全尺寸梁柱组件的循环载荷试验，以评估焊接缺陷的影响。试验结果指出了缺陷的几何形状和位置对连接性能的影响。少

项目成果

K.Azuma: "Fracture ductility of welded T joints under a very few cycles of reversed loading" Research Report, Kyushu Branch of Architectural Institute of Japan. 353-356 (1997)

K.Azuma：“极少数反向载荷循环下焊接 T 型接头的断裂延展性”研究报告，日本建筑学会九州分会。

東 康二: "予ひずみ材による溶接T継手止端部の破壊(その1〜2)" 日本建築学会大会学術講演梗概集、札幌. C-1. 589-592 (1995)

Koji Higashi：“由于预应变材料导致的焊接 T 形接头趾部断裂（第 1-2 部分）”日本建筑学会会议记录，札幌 C-1（1995 年）。

Bo Wang: "The prediction of plastic collapse load for welded T-joints under combined tensile and bending loads" 破壊力学シンポジウム、京都、日本材料学会. 262-266 (1995)

Bo Wang：“拉伸和弯曲复合载荷下焊接 T 型接头的塑性塌陷载荷预测”断裂力学研讨会，日本京都材料科学学会 262-266 (1995)。

Bo Wang: "Damage criteria and safety assessment for welded T-joints" J.Constructional Steel, Japanese Society of Steel Construction. Vol.4. 105-112 (1996)

王博：“焊接T型接头的损伤标准和安全评估”J.Constructional Steel，日本钢结构协会。

Bo Wang: "Fracture at toes of welded T-joints in prestrained material" 日本建築学会大会学術講演梗概集、札幌. C-1. 593-594 (1995)

Bo Wang：“预应变材料焊接 T 形接头的断裂”，日本建筑学会会议记录，札幌 C-1（1995 年）。