Study on Fatigue Strength Design of Welded-joint under random loading

随机载荷下焊接接头疲劳强度设计研究

• 批准号: 05452312
• 负责人: MACHIDA Susumu
• 金额: $ 4.8万
• 依托单位: University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05452312/
• 关键词: Structual model specimen; "Storm Model" block loading; Fatigue assessment; The foatigue crack opening; closere phenomenon; "High-precision Compliance Mesurement System"; The effect of past loading history; Compliance; Change rate of compliance; R

The fatigue crack propagation tests using structural model specimens are carried out under constant loading and the "Storm Model" block loading. Also study on the reliability of the current fatigue assessment methods and the application of fracture mechanics to fatigue assesment are made.Moreover, for the purpose of proper understanding of the fatigue crack opening/closure phenomenon, detailed observations of change in the strain near fatigue crack tip using "High-precision Compliance Measurement System" and CCT specimens are carried out.As a result, the following four main points are obtained.1) The fatigue assessment based on S-N diagram obtained from constant loading fatigue tests can not take into account the effect of past loading history. So the accuracy of this assessment turn out to be extremely lowered under some loading patterns. (for example, the loading pattern in which retardation is remarkable)2) The fatigue assessment based on S-N diagram obtained form block loading fati … More gue tests can take into account the effect of the loading pattern within one block. So the accuracy of this assessment is higher than the above mentioned method 1) but it even can not take into account the effect of interaction of different block, then further high accuracy of this assessment depend on how quantitatively the block loading model reflects the actually loading pattern.3) The fatigue assessment based on fracture mechanics can take into account the effect of past loading history, so the accuracy of this assessment could be higher than above mentioned method 2) if proper fatigue crack propagation model was established. Also further high accuracy of this assessment depend on proper understanding of the fatigue crack propagation behavior especially of the fatigue crack opening/closure phenomenon.4) Successful measurement of the hysteresis curve of load vs.strain with high accuracy was made and, introducing the curve of compliance and the change rate of compliance during one cycle we succeeded in the automatically measurement of the Closing load and RPG load. Less

使用结构模型试件在恒定载荷和“风暴模型”块体载荷下进行疲劳裂纹扩展试验。本文还对现有疲劳评定方法的可靠性和断裂力学在疲劳评定中的应用进行了研究，并为了正确理解疲劳裂纹张开/闭合现象，利用高精度柔度测量系统和CCT试样对疲劳裂纹尖端应变的变化进行了详细的观测，结果表明，疲劳裂纹尖端应变的变化与疲劳裂纹尖端应变的变化有关。得出以下四个主要观点：1）基于恒载荷疲劳试验得到的S-N图的疲劳评估不能考虑过去载荷历史的影响。因此，这种评估的准确性在某些加载模式下变得非常低。(for 2）根据块体加载疲劳试验数据， ...更多信息 gue测试可以考虑一个块内的加载模式的影响。因此，该评估方法的准确性高于上述方法1），但它甚至不能考虑不同块体之间的相互作用的影响，因此该评估方法的准确性进一步取决于块体加载模型如何定量地反映实际加载模式。3）基于断裂力学的疲劳评估方法可以考虑过去加载历史的影响，因此，如果建立合适的疲劳裂纹扩展模型，该方法的评定精度可高于上述方法2）。此外，该评估的进一步高精度取决于对疲劳裂纹扩展行为，特别是疲劳裂纹张开/闭合现象的正确理解。4）成功地测量了高精度的载荷-应变滞后曲线，并引入柔度曲线和一个循环过程中柔度的变化率，成功地自动测量了闭合载荷和RPG载荷。少

项目成果

町田進: "ブロック荷重を受ける溶接構造の疲労寿命推定法に関する一考察" 日本造船学会論文集. 172. 579-587 (1992)

Susumu Machida：“承受块载荷的焊接结构的疲劳寿命估计方法的研究”日本造船学会汇刊 172. 579-587 (1992)。

町田進: "過大荷重下におけるき裂進展(その1)" 日本造船協会第219研究部会 平成6年度報告書. 44-57 (1995)

Susumu Machida：“超载下的裂纹扩展（第 1 部分）”日本造船研究所第 219 届研究小组委员会 1994 年报告 44-57（1995 年）。

町田進: "従来き裂進展解析法による推定との比較" 日本造船協会第219研究部会 総合報告書. (予定). (1996)

Susumu Machida：“与传统裂纹扩展分析方法的估计比较”日本造船研究所第 219 期研究小组的综合报告（计划）（1996 年）。

町田進: "スパイク荷重下におけるき裂進展" 日本造船協会第219研究部会 総合報告書. (予定). (1996)

Susumu Machida：“峰值载荷下的裂纹扩展”日本造船研究所第 219 个研究组的综合报告（计划）。

Susumu Machida: "Effects of Loading Series on Fatigue Behavior" Japan Ship Research Report No.216 Final Report. 407-409 (1994)

Susumu Machida：“加载系列对疲劳行为的影响”日本船舶研究报告第 216 号最终报告。