权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Evaluation Procedure for High Strength Steels for Offshore Structures Considering Strength Mis-Matching in Welds

考虑焊缝强度失配的海上结构用高强度钢的评估程序

基本信息

批准号：
05302050
负责人：
TOYODA Masao
金额：
$ 9.22万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Co-operative Research (A)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-05302050/
关键词：
High Strength Steel Welds Offshore Structures Strength Mis-Matching HAZ Fracture Toughness Fracture Performance Constraint Effect CTOD Testing Local Approach 海洋構造用高強度鋼多層溶接継手き裂湾曲現象

项目摘要

This study developed a procedure for assessing fracture performance of welded joints of high strength steels in the light of design solution of weldments. Major concern was an influence of strength mis-matching between the base and weld metals on the fracture mechanical behavior of welded joints. TMCP steels for offshore structures with yield point 420 to 500MPa class were employed. The transferability of 3-point bend test results to fracture performance assessment of wide plates was discussed with attention to strength mis-matching effect.Strength overmatch of the weld metal gave rise to different effects on the fracture behavior of the heat affected zone (HAZ)depending on the toughness level of the HAZ.In the case that the HAZ had a moderate toughness, the overmatch condition resulted in deviation of ductile crack extension toward a softer material. The resultant high critical CTOD at unstable fracture does not necessarily mean the actual toughness of the HAZ itself. On the other hand, in the case of the embrittled HAZ,the overmatch condition promoted fracture initiation in the HAZ and lowers the fracture toughness of the HAZ.This was due to the elevation of plastic constraint in the HAZ.Strength overmatching is not always beneficial The specimen geometry also affects the degree of constraint in the crack tip region. The deep notch bend specimen produces the geometrical constraint to the largest extent. The geometrical constraint in the deep notch bend specimen was more intense than the constraint caused by 25% strength overmatching for the center notched wide plate subjected to tension. The present study developed the procedure to transfer toughness results to fracture assessment of wide plates with taking constraint effects into account. A new methodology for fracture toughness requirement of welds was proposed as a function of the required deformability of weldnents.

根据高强度钢焊接接头的设计方案，建立了高强度钢焊接接头断裂性能评定方法。主要关注的是母材和焊缝金属之间的强度不匹配对焊接接头断裂力学行为的影响。海洋结构用TMCP钢的屈服点为420-500 Mpa级。讨论了三点弯曲试验结果在宽板断裂性能评定中的可转换性，并考虑了强度失配效应。焊缝金属强度过匹配对热影响区断裂行为的影响因热影响区韧性水平的不同而不同。当热影响区具有中等韧性时，过匹配条件导致延性裂纹扩展偏向较软的材料。由此产生的不稳定断口的高临界CTOD并不一定意味着热影响区本身的实际韧性。另一方面，对于脆化的HAZ，过匹配条件促进了HAZ的断裂萌生，降低了HAZ的断裂韧性，这是由于HAZ中塑性约束的提高。强度过匹配并不总是有利的，试件的几何形状也影响裂纹尖端区域的约束程度。深槽弯曲试件最大程度地产生几何约束。深缺口弯曲试件的几何约束比中心缺口宽板拉伸时25%强度过匹配引起的约束更强烈。本文发展了一种将韧性结果转化为宽板断裂评定并考虑约束效应的方法。提出了一种新的焊缝断裂韧性要求方法，它是焊件所要求的变形能力的函数。