A Construction of Judging System of Welding under Pulsating Loads

脉动载荷焊接判定系统的构建

基本信息

批准号：
05650950
负责人：
KIM You-chul
金额：
$ 1.47万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
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/en/grant/KAKENHI-PROJECT-05650950/
关键词：
Welding in service Repair work Reinforcement work Critical strain for hot crack Prevention of hot crack Prevention of solidification crack 高温割れ凝固割れ割れ防止荷重作用下の溶接割れ発生限界ひずみ割れ判定法変動荷重溶接割れ高温割れ発生条件限界ひずみ

项目摘要

The structures in service conditions such as offshore structures, towers, bridges and so on are always suffered the pulsating loads by waves, current, wind or moving vehicles, etc. So, repair, reinforcement or reconstruction works by welding on these structures are done under the pulsating loads.The weld cracking test under the pulsating loads is carried out. As the results of the experiments, the accumulation strain, epsilon_t, by which the weld metal was repeatedly applied at a short time from the liquidus to the solidus was proposed as a measure for deciding hot crack initiation under the pulsating loads. epsilon_t was expressed with the relative root gap opening displacement, DELTAdelta, which can be easily measured before welding. The practical deciding equation for hot crack initiation under the pulsating loads using DELTAdelta was derived. Applying the practical deciding equation to the results of the hot cracking test for the case that the uniform pulsating loads are applied, its validity was shown.It is found that the hot cracks under the pulsating loads can be classified into crack of solid-liquid state and crack of solid state by conducting the high temperature tensile test on the weld metal. The former is called a solidification crack and the latter is HS (Hot Crack in Solid state) - type crack. Concerning the solidification crack initiation, the main factor was the product of DELTAdelta by the external loads and repeated number. The main factor for HS-type crack initiation was the maximum strain rate (the maximum root gap opening rate) by the external loads in a cycle.Welding is applied to the actual work for a bridge in service and its validity demonstrated.

海上建筑物、塔架、桥梁等处于服役状态的结构物，经常受到波浪、海流、风或移动车辆等的脉动载荷作用，因此，对这些结构物进行焊接修复、加固或改造工程是在以下条件下进行的：进行脉动载荷下的焊缝裂纹试验。作为实验结果，提出了在短时间内反复施加从液相线到固相线的焊缝金属的累积应变epsilon_t，作为决定脉动载荷下热裂纹萌生的指标。 epsilon_t 用相对根部间隙张开位移 DELTAdelta 表示，可以在焊接前轻松测量。利用DELTAdelta 推导了脉动载荷下热裂纹萌生的实用判定方程。将实用判定方程应用到均匀脉动载荷情况下的热裂纹试验结果中，验证了其有效性。发现脉动载荷作用下的热裂纹可分为固-液态裂纹。通过对焊缝金属进行高温拉伸试验产生固态裂纹。前者称为凝固裂纹，后者为HS（固态热裂纹）型裂纹。关于凝固裂纹的萌生，主要因素是外部载荷与重复次数的乘积DELTAdelta。 HS型裂纹萌生的主要因素是一个周期内外荷载所产生的最大应变率(最大根部间隙张开率)。将焊接应用于某在役桥梁的实际工作中,验证了其有效性。