A slope-based J-integral approach and advanced image processing for assessment of the cyclic fatigue delamination behavior of adhesive joints

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue Pub Date : 2024-11-23 DOI:10.1016/j.ijfatigue.2024.108730

Gabriel Riedl , Francesco Baldi , Gernot M. Wallner

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Abstract

A fatigue fracture mechanics methodology was developed and established, employing a slope-based J-integral approach combined with advanced image processing techniques. Adhesively bonded double cantilever beam (DCB) specimens were tested under constant displacement amplitude loading. The beam rotation was tracked by affixing a repetitive pattern on the DCB specimens and capturing images at the maximum displacement amplitude. Using a custom-developed image processing procedure, the beam rotation was deduced. To validate the methodology, DCB fatigue experiments were conducted at 23, 60 and 75 °C on aluminum adherends bonded with a structural 2-K epoxy adhesive. The J-based approach was compared with a conventional, compliance-based linear elastic fracture mechanics (LEFM) method. The epoxy was a rather brittle, high-modulus adhesive with a bond line thickness of 0.25 mm, resulting in predominantly linear elastic material behavior. By analyzing the images taken during fatigue testing, a stiffening effect of the steel load blocks was observed. Excluding pattern elements directly below the load block yielded the best agreement between J-integral and LEFM data. Both approaches were in excellent agreement within the investigated temperature range. The investigated adhesive exhibited a highly temperature-dependent behavior, which was associated with higher crack propagation rates and a lower fatigue threshold at 60 and 75 °C.

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基于斜率的 J 积分法和先进的图像处理技术用于评估粘合剂接头的循环疲劳分层行为

采用基于斜率的 J 积分方法，结合先进的图像处理技术，开发并建立了疲劳断裂力学方法。在恒定位移振幅加载条件下，对粘合双悬臂梁（DCB）试样进行了测试。通过在 DCB 试样上粘贴重复图案并捕捉最大位移振幅时的图像来跟踪梁的旋转。利用定制开发的图像处理程序，可以推断出梁的旋转情况。为了验证该方法，在 23、60 和 75 °C 温度条件下，对使用 2-K 结构环氧树脂粘合剂粘合的铝质附着物进行了 DCB 疲劳实验。基于 J 的方法与传统的、基于顺应性的线性弹性断裂力学（LEFM）方法进行了比较。环氧树脂是一种相当脆的高模量粘合剂，粘合线厚度为 0.25 毫米，因此材料行为主要为线性弹性。通过分析疲劳测试期间拍摄的图像，可以观察到钢加载块的加固效应。排除负载块正下方的图案元素后，J 积分和 LEFM 数据的一致性最好。在所研究的温度范围内，两种方法都非常一致。所研究的粘合剂表现出与温度高度相关的行为，在 60 和 75 ° C 时，裂纹扩展率较高，疲劳阈值较低。

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来源期刊

International Journal of Fatigue 工程技术-材料科学：综合

CiteScore

10.70

自引率

21.70%

发文量

619

审稿时长

58 days

期刊介绍： Typical subjects discussed in International Journal of Fatigue address: Novel fatigue testing and characterization methods (new kinds of fatigue tests, critical evaluation of existing methods, in situ measurement of fatigue degradation, non-contact field measurements) Multiaxial fatigue and complex loading effects of materials and structures, exploring state-of-the-art concepts in degradation under cyclic loading Fatigue in the very high cycle regime, including failure mode transitions from surface to subsurface, effects of surface treatment, processing, and loading conditions Modeling (including degradation processes and related driving forces, multiscale/multi-resolution methods, computational hierarchical and concurrent methods for coupled component and material responses, novel methods for notch root analysis, fracture mechanics, damage mechanics, crack growth kinetics, life prediction and durability, and prediction of stochastic fatigue behavior reflecting microstructure and service conditions) Models for early stages of fatigue crack formation and growth that explicitly consider microstructure and relevant materials science aspects Understanding the influence or manufacturing and processing route on fatigue degradation, and embedding this understanding in more predictive schemes for mitigation and design against fatigue Prognosis and damage state awareness (including sensors, monitoring, methodology, interactive control, accelerated methods, data interpretation) Applications of technologies associated with fatigue and their implications for structural integrity and reliability. This includes issues related to design, operation and maintenance, i.e., life cycle engineering Smart materials and structures that can sense and mitigate fatigue degradation Fatigue of devices and structures at small scales, including effects of process route and surfaces/interfaces.