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A study on prediction method for low cycle fatigue strength of steel welded members

钢焊接构件低周疲劳强度预测方法研究

基本信息

批准号：
16360229
负责人：
TATEISHI Kazuo
金额：
$ 7.81万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16360229/
关键词：
Low cycle fatigue strength Image technique Welded joints Heat affected zone Damage mechanics Local strain TIG dressing 低サイクル疲労溶接継手鋼製橋脚熱影響部変動ひずみ

项目摘要

A new low cycle fatigue testing system has been developed, in which strains of the specimen are measured by image technique. The low cycle fatigue tests of steel plain material and welded portion under constant and variable strain amplitude, particularly the fatigue life less than ten cycles, was conducted by using the newly developed testing system. The test results indicated that the fatigue life of welded portion, such as deposit metal and heat affected zone (HAZ), was much shorter than that of plain material. Particularly, HAZ was the weakest spot, of which fatigue life was about 30% of the plain material. And fatigue strength curves for the plain material, the deposited metal and the HAZ were proposed, individually.As an estimation method of low cycle fatigue strength of "welded joint", peak strain based fatigue assessment method was verified. T-shape welded joints were employed for the verification test. The specimen was analyzed by elasto-plastic finite element method in order to quantify the local strain field around welded portion and the peak strain at the cracked point. On the other hand, fatigue life of the specimen was experimentally obtained by low cycle fatigue tests. The relationship between the peak strain and the fatigue life was consistent with the fatigue strength curve for the deposited metal. Consequently, it was demonstrated that the fatigue assessment method by peak strain approach was available even in low cycle fatigue region. And the improvement of fatigue strength of welded joints by TIG dressing was investigated. T-shape welded joint specimens of which weld toes were finished by TIG dressing were tested. The fatigue test results were compared with that of as-welded specimens tested in the same conditions. The test results indicated that TIG dressing could substantially increase the low cycle fatigue strength of welded joints.

开发了一种新的低周疲劳测试系统，其中通过图像技术测量样本的应变。利用新开发的试验系统，对钢质素材和焊接部进行了等应变幅和变应变幅下的低周疲劳试验，特别是小于10次循环的疲劳寿命试验。试验结果表明，熔敷金属和热影响区（HAZ）等焊接部分的疲劳寿命比普通材料短得多。其中HAZ是最薄弱的部位，其疲劳寿命约为普通材料的30%。并分别提出了普通材料、熔敷金属和热影响区的疲劳强度曲线。作为“焊接接头”低周疲劳强度的估算方法，对基于峰值应变的疲劳评估方法进行了验证。验证试验采用T型焊接接头。采用弹塑性有限元法对样本进行分析，以量化焊接部分周围的局部应变场和裂纹点处的峰值应变。另一方面，通过低周疲劳试验获得了试件的疲劳寿命。峰值应变与疲劳寿命之间的关系与熔敷金属的疲劳强度曲线一致。结果表明，即使在低周疲劳区域，峰值应变法的疲劳评估方法也是可用的。并研究了TIG修整对焊接接头疲劳强度的提高。对焊趾经过TIG修整的T形焊接接头试件进行了试验。疲劳试验结果与相同条件下测试的焊态试样的结果进行了比较。试验结果表明，TIG修整可显着提高焊接接头的低周疲劳强度。