Equivalent fatigue crack growth rate model and life assessment method for the surface of welded joints under variable amplitude loading

IF 6 2区工程技术 Q1 ENGINEERING, MECHANICAL

Theoretical and Applied Fracture Mechanics Pub Date : 2026-04-01 Epub Date: 2026-02-04 DOI:10.1016/j.tafmec.2026.105470

Chao Wang, Kaiyun Wang, Tao Zhu, Jingke Zhang, Bing Yang, Shoune Xiao, Guangwu Yang

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Abstract

The surface fatigue crack growth mechanism of welded structures under random loads in service is complex, and the assessment method based on failure life lacks an effective description of the crack growth process. This study investigates the surface crack evolution mechanism in welded joints under random fatigue loading. First, a series of experiments were conducted to determine the through-thickness crack growth rate parameters of aluminum alloy butt joints. These experiments revealed the influence of thickness and stress ratio on the fatigue crack growth rate. The normalization of the growth rate of surface cracks under variable fatigue loading was achieved through the introduction of the constraint factor of surface cracks and the crack closure function(ΔK_eff-da/dN). Moreover, the effect of mean stress on the crack growth threshold was considered to describe the crack growth behavior of welded joints more accurately under near-threshold conditions and at high stress ratios. Furthermore, a two-stage model for surface fatigue crack growth in welded joints under variable-amplitude loading is proposed. The random load was converted into an equivalent variable-amplitude load spectrum, enabling a dynamic calculation of the surface fatigue crack growth life. Finally, this model significantly narrows the prediction error for test fatigue life from −25% ∼ 45% under the BS7910 standard analytical method to within −15% ∼ 25%, verifying the effectiveness of the proposed life assessment method for variable-amplitude fatigue crack growth in welded joints.

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变幅载荷下焊接接头表面等效疲劳裂纹扩展速率模型及寿命评估方法

随机载荷作用下焊接结构表面疲劳裂纹扩展机理复杂，基于失效寿命的评估方法缺乏对裂纹扩展过程的有效描述。研究了随机疲劳载荷作用下焊接接头表面裂纹的演化机理。首先，进行了一系列试验，确定了铝合金对接接头的裂纹扩展速率参数。这些实验揭示了厚度和应力比对疲劳裂纹扩展速率的影响。通过引入表面裂纹约束因子和裂纹闭合函数（ΔKeff-da/dN），实现了变疲劳载荷下表面裂纹扩展速率的归一化。此外，考虑了平均应力对裂纹扩展阈值的影响，可以更准确地描述近阈值和高应力比条件下焊接接头的裂纹扩展行为。在此基础上，提出了变幅载荷作用下焊接接头表面疲劳裂纹扩展的两阶段模型。将随机载荷转化为等效变幅载荷谱，实现了表面疲劳裂纹扩展寿命的动态计算。最后，该模型将BS7910标准分析方法下的试验疲劳寿命预测误差从- 25% ~ 45%显著缩小到- 15% ~ 25%，验证了所提出的焊接接头变幅疲劳裂纹扩展寿命评估方法的有效性。

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来源期刊

Theoretical and Applied Fracture Mechanics 工程技术-工程：机械

CiteScore

8.40

自引率

18.90%

发文量

435

审稿时长

37 days

期刊介绍： Theoretical and Applied Fracture Mechanics'' aims & scopes have been re-designed to cover both the theoretical, applied, and numerical aspects associated with those cracking related phenomena taking place, at a micro-, meso-, and macroscopic level, in materials/components/structures of any kind. The journal aims to cover the cracking/mechanical behaviour of materials/components/structures in those situations involving both time-independent and time-dependent system of external forces/moments (such as, for instance, quasi-static, impulsive, impact, blasting, creep, contact, and fatigue loading). Since, under the above circumstances, the mechanical behaviour of cracked materials/components/structures is also affected by the environmental conditions, the journal would consider also those theoretical/experimental research works investigating the effect of external variables such as, for instance, the effect of corrosive environments as well as of high/low-temperature.