Crack detection via strain measurements in fatigue testing

al-Karawi, Hassan; Polach, Franz von Bock und; Al‐Emrani, Mohammad

doi:10.1111/str.12384

Cited by 9 publications

(3 citation statements)

References 12 publications

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“…Looking at the HFMI groove, it can be seen that three regions contained indentation marks that were relatively widely spaced, suspected to be a sign of excessive travel speed during treatment. These regions were also mainly situated on one half of the specimen and could have acted as crack initiation sites [29]. Very similar observations were made for the HM2-2 specimen, which also failed far earlier than ex- trum compared with the 10 5 case.…”

Section: The Va Experimentssupporting

confidence: 73%

High‐cycle variable amplitude fatigue experiments and design framework for bridge welds with high‐frequency mechanical impact treatment

2022

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Fatigue enhancement by way of high-frequency mechanical impact (HFMI) treatment can enable effective design and construction of steel bridges. However, bridges may experience high and varying mean stresses, the effects of which are not covered today by any design recommendation or in the literature on HFMI-treated joints. In this study, fatigue experiments were conducted with realistic in-service bridge loading, which revealed the same high fatigue performance as for constant amplitude loading. The effect of mean stress in spectrum loading was quantified and a method to account for it in an equivalent manner is proposed. A design framework has been developed for design and engineering purposes.

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Section: The Va Experimentssupporting

confidence: 73%

High‐cycle variable amplitude fatigue experiments and design framework for bridge welds with high‐frequency mechanical impact treatment

2022

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“…The SGs were used to monitor the crack growth behaviour during the fatigue test. It has been shown that SGs installed a few millimetres away from the weld toe can be used to measure a 0.5 to 1 mm long fatigue crack, indicating the transition from the crack initiation (CI) to the crack propagation (CP) phase [22]. In this study, a recommended 5% change in the measured strain values was used as a threshold from CI to CP.…”

Section: Fatigue Test Resultsmentioning

confidence: 99%

Fatigue design of stress relief grooves to prevent weld root fatigue in butt-welded cast steel to ultra-high-strength steel joints

Havia,

Lipiäinen,

Ahola

et al. 2024

Weld World

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In the welded joints, fatigue failures typically originate from defects or notch-like geometries under cyclic loading. This study investigates the impact of stress relief grooves (SRG) on the fatigue performance of butt-welded cast steel to ultra-high-strength steel components using experimental fatigue tests and finite element method. The experiments examined the fatigue properties of hybrid joints between G26CrMo4 cast steel (t = 20 mm) and S960 steel plate (t = 6 mm) with and without SRG. Gas metal arc welding process was used to weld the butt joints that had a permanent root backing machined on the cast steel part, causing a crack-like defect to the weld root. Additionally, the top surfaces of the welded parts were aligned, resulting in a significant axial misalignment in the butt joint. The SRG, positioned close to the weld root, was found to have a beneficial influence on the joint’s fatigue performance by a factor of 1.2 when using the nominal stress criterion. However, the fatigue capacity was still roughly 35% lower compared to the symmetrical equivalent due to the secondary bending stress, caused by axial misalignment. The finite element analyses indicated that the SRG reduces the amount of secondary stresses at the weld root leading to lower total structural stress. The study recommends using the FAT80 (m = 3) design curve in the structural stress method, for similar butt-welds having a crack-like defect, parallel to the loading direction, at the weld root. However, for welded joints with crack-like defects, it is advisable to use linear elastic fracture mechanics rather than relying solely on stress-based local approaches.

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“…Chaudhuri (2019) [26] investigated the effect of the local weld toe geometry on fatigue crack initiation life by positioning a series of strain gauges across the weld toe. Al-Karwai (2021) [27] uses this same principle to measure the crack length in studying fatigue crack initiation and propagation in welds.…”

Section: Introductionmentioning

confidence: 99%

Front face strain compliance for quantification of short crack growth in fatigue testing

Hasan

Chaudhuri

Waele

2023

The Journal of Strain Analysis for Engineering Design

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Short fatigue crack growth investigation is of considerable scientific interest as it comprises a significant portion of the total fatigue life of a structure. It is very challenging to accurately quantify this stage of fatigue crack growth experimentally. In this article, a novel front face strain compliance technique for single-edge notched specimens subjected to four-point bending is proposed. Finite element analysis is performed to determine the correlation between crack length and strain change near the crack. This relationship is then validated by experiments in which strains are measured by strain gauges attached near the short crack, and crack length is quantified by examining beachmark lines at the fracture surfaces. Based on the numerical and experimental results, it is concluded that the strain measured near the notch allows quantifying short crack growth for normalised crack lengths in the range 0.01 ≤ a/W ≤ 0.06 ( a/W being the ratio of crack length over specimen width). A compliance equation based on the front face strain is finally presented.

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Crack detection via strain measurements in fatigue testing

Cited by 9 publications

References 12 publications

High‐cycle variable amplitude fatigue experiments and design framework for bridge welds with high‐frequency mechanical impact treatment

High‐cycle variable amplitude fatigue experiments and design framework for bridge welds with high‐frequency mechanical impact treatment

Fatigue design of stress relief grooves to prevent weld root fatigue in butt-welded cast steel to ultra-high-strength steel joints

Front face strain compliance for quantification of short crack growth in fatigue testing

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