Quantitative fractography of fatigue and an illustrative case study

Goldsmith, N.T.; Wanhill, R.J.H.; Molent, L.

doi:10.1016/j.engfailanal.2018.10.013

Cited by 18 publications

(8 citation statements)

References 18 publications

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“…SEM photographs and the corresponding EDS spectrum of elements obtained from some areas around the fatigue fracture surface of the damaged elbow are presented in Figures 7 and 8. The presence of fatigue striations shown in Figure 7 indicated that a fatigue crack has been growing in that particular area of the damaged elbow as a result of some cyclic loadings [15]- [16]. As seen in Figure 7, the crack is growing from left to right or from inner side to the outer side of the elbow.…”

Section: Sem Fractography and Eds Analysismentioning

confidence: 99%

“…The crack pattern in the final fracture area can be ductile or brittle, depending on the type of material and loading conditions. If the signs of beach mark formation are not clearly visible, the fatigue crack propagation can be identified by formation of striations using SEM fractographs [15]- [16]. Meanwhile, in areas with final fractures, SEM fractographs usually exhibit dimple pattern in case of ductile fractures or chevron markings (or cleavage) pattern in case of brittle fractures [1]- [3].…”

Section: Introductionmentioning

confidence: 99%

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Fatigue Failure in a Longitudinal Welded Elbow of a Processing Vessel

Adnyana

2022

metal.

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A longitudinal welded elbow made of austenitic stainless steel type 316 and used as a drain line on a processing vessel had suffered damage (leakage) after it had only been in operation for a few years. Process fluid that was drained out of the vessel consists of fatty acid containing hydrogen gas at a temperature of 150°C and a pressure of 60 bar(g). Initially, the drain process was carried out only once a year, but recently due to frequent changes in the types of product being made, the frequency of drain process has increased to several times a month. This study aims to determine the type and factors that have caused leakage in the elbow. Metallurgical assessment was carried out by preparing a number of specimens from the leaking elbow. A number of laboratory examinations were performed including visual and macroscopic tests, chemical composition analysis, metallographic examination, hardness tests and scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS) analysis. The results obtained indicate that the leaking elbow has experienced fatigue failure due to cyclic loadings caused by the increasing frequency of the number of drain processes carried out through the elbow. The factor causing fatigue failure at the elbow is likely due to welding defect of imperfect shape that formed on the inner wall of the elbow around the HAZ (heat-affected zone)/fusion boundary, and causing high stress concentrations in that area.

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Section: Sem Fractography and Eds Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fatigue Failure in a Longitudinal Welded Elbow of a Processing Vessel

Adnyana

2022

metal.

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“…While optical microscopes are versatile and simple to use, they lack the resolution necessary for these highly detailed fracture surface observations. 27 This need for highresolution imaging led to the development of the earliest electron microscopes. 28 Continuous development has occurred in electron microscopes over the past decades to allow many modern electron microscopes to achieve sub-nm resolution.…”

Section: Introductionmentioning

confidence: 99%

An analysis of fatigue crack features at various crack lengths through mating fracture surface pairs

Field,

Kandare,

Dixon

et al. 2024

Fatigue Fract Eng Mat Struct

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This paper presents a novel high‐resolution direct analysis of mating AA7050‐T7451 fracture surfaces at crack lengths from 0.1 to 1.3 mm (Kmax of 4.51 to 16.39 MPa√m) for the purpose of analyzing the fatigue growth mechanisms. The various fractographic features observed at these crack lengths were then compared to the known accelerative effects of an applied loading sequence that contained underloads at regular intervals. A correlation was found between some of the observed features and the local fatigue crack growth rate. This study provides new insight into the prominent mechanisms that dictate crack growth rate and ultimately should assist with developing crack growth prediction methods that more accurately represent the physics of the fatigue crack growth mechanisms.

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“…In some works, scientists have tried to combine all fractographic methods and link them to fracture mechanisms or fatigue life, especially using surface roughness parameters evaluated from the fracture surfaces [ 36 , 37 , 38 ]. Examples of quantitative fractography cases are presented in the works by Goldsmith et al [ 39 ] and by Kobayashi et al [ 40 ]. However, as far as the authors know, there are no studies in the literature connecting multiaxial loadings and surface fracture parameters in round bars with blind holes subjected to multiaxial loading.…”

Section: Introductionmentioning

confidence: 99%

Fracture Surface Behavior of 34CrNiMo6 High-Strength Steel Bars with Blind Holes under Bending-Torsion Fatigue

2021

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The present study evaluates the fracture surface response of fatigued 34CrNiMo6 steel bars with transverse blind holes subjected to bending with torsion loading. The analysis of the geometric product specification was performed by means of height parameters Sx, functional volume parameters Vx, and fractal dimension Df. Surface topography measurements were carried out using an optical profilometer with focus variation technology. The experimental results show that the doubling the bending to torsion moment ratio B/T from B/T = 1 to B/T = 2, maintaining the same normal stress amplitude, greatly reduces both Sa, Vv as well as the fractal dimension Df of the analyzed specimen fractures by 32.1%, 29.8%, and 16.0%, respectively. However, as expected, a two-fold increase in the B/T ratio, maintaining the same normal stress amplitude, resulted in a larger number of cycles to fatigue crack initiation, Ni, which can be explained by the lower shear stress level. These experiments prove that parameters Sx, Vx, Df are smaller for larger Ni values, which is an important finding. In addition, it was found a high consistency of surface topography measurements for the two sides of the broken specimens. The proposed methodology is both reliable and applicable for other engineering applications involving different geometries and loading conditions.

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Quantitative fractography of fatigue and an illustrative case study

Cited by 18 publications

References 18 publications

Fatigue Failure in a Longitudinal Welded Elbow of a Processing Vessel

Fatigue Failure in a Longitudinal Welded Elbow of a Processing Vessel

An analysis of fatigue crack features at various crack lengths through mating fracture surface pairs

Fracture Surface Behavior of 34CrNiMo6 High-Strength Steel Bars with Blind Holes under Bending-Torsion Fatigue

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