Effect of Pre-Fatigue on Impact Tensile Properties of Laser Welded Butt Joint of High Strength Steel Plates

Tsuda, Hiroshi; Daimaruya, Masashi; Kobayashi, Hidetoshi; Sunayama, Yoshihiko

doi:10.2472/jsms.55.824

Cited by 8 publications

(4 citation statements)

References 11 publications

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“…In contrast with the above-mentioned tendency for Al alloys, such a deterioration of mechanical properties was not found for two kinds of structural steels for building structure (Itabashi and Fukuda, 2004). Tsuda et al (2006) also confirmed that even automotive sheet steels did not reveal such deterioration. They executed not only for low-cycle pre-fatigue, but also for high-cycle pre-fatigue.…”

Section: Introductionsupporting

confidence: 55%

Geometric features of MnS grains in damaged free-cutting steel SUM24L by fatigue and dynamic tension

Itabashi

2015

Mechanical Engineering Letters

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For free-cutting steels, their mechanical properties, especially local toughness, are functionally degraded. The second phase exists in steel matrix, as a chip breaker, tool edge stabilizer and tool life extender. For these purposes, the second phase plays the role of a solid lubricant. Typical materials as the second phase in free-cutting steels are Pb and MnS. The second phase grains are recognized as stress concentrated points during machining. Such points have the possibility to be new crack initiation sites during fatigue loading. Formerly, the present author found that some Al alloys are degraded by loading combination of fatigue and dynamic tension. On the other hand, for some structural steels, almost no degradation is found by the fatigue-impact loading in tension. However, in 2013 the present author reported that free-cutting steels are deteriorated to some extent by such a loading combination. The deterioration may be caused by the stress concentrated points around the second phase, MnS in SUM24L (JIS G 4804:2008, equivalent to AISI 12L14 steel), which is weakened by pre-fatigue process. In this paper, in order to detect microscopic difference between the specimens fractured in dynamic tension with/without pre-fatigue, geometric features of MnS grains are observed by an optical microscope. In the microscopic observation, typical deformation of surrounding matrix steel is found. Into MnS grain, steel matrix is penetrated. Focusing on the existence of the matrix penetration, the number of MnS grains in free-cutting steel is counted with geometrical features. The experimental results show that the information of the penetrations has a possibility to be an indicator of the dynamic strain rate, comparing with the specimens fractured by quasi-static tension.

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Section: Introductionsupporting

confidence: 55%

Geometric features of MnS grains in damaged free-cutting steel SUM24L by fatigue and dynamic tension

Itabashi

2015

Mechanical Engineering Letters

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“…The table shows which effects were observed on the results of tensile tests at quasi‐static and/or high strain rates after a given cyclic load had been applied. While the tensile properties of some materials are strongly affected even after a low number of loading cycles, 5,19,20 in some others the effect is negligible, 2,4,21–23 and several experiments have shown that the dynamic behaviour of the material may be affected although no effects are observed in quasi‐static tests or these effects are very small 4,5,22,24,25 …”

Section: State Of the Artmentioning

confidence: 99%

“…While the tensile properties of some materials are strongly affected even after a low number of loading cycles, 5,19,20 in some others the effect is negligible, 2,4,21-23 and several experiments have shown that the dynamic behaviour of the material may be affected although no effects are observed in quasi-static tests or these effects are very small. 4,5,22,24,25 The contribution of previous damage to the fracture process appears to be strongly linked with the materials microstructure. 23 During cyclic loading, the dislocations inside the material change the shape and position, forming new arrangements which can embrittle the material.…”

Section: Effect Of Fatigue Damage On Tensile Propertiesmentioning

confidence: 99%

Effect of fatigue damage on static and dynamic tensile behaviour of electro‐discharge machined Ti‐6Al‐4V

Lopez

Verleysen

Degrieck

2012

Fatigue Fract Eng Mat Struct

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The fatigue performance of electro-discharge machined Ti-6Al-4V and, more specifically, the effect of cyclic damage on the static and dynamic tensile properties of the material have been investigated. In a first step, fatigue failure was studied. Afterwards, tensile tests were performed on specimens that had been previously subjected to cyclic loading during predefined fractions of the fatigue life. In addition to conventional experiments at quasi-static strain rate, dynamic tests were performed using a split Hopkinson tensile bar setup. The edges of some of the specimens were removed after cyclic loading to discriminate between the effects of damage at the edges and in the bulk of the material. Results revealed that early fatigue failure is due to the growth of cracks on the machined edges of the specimens. Edge cracks can randomly reduce fracture strain and energy absorbing capacity. However, cyclic damage does not affect the tensile properties of the bulk material

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“…For the accurate prediction of crash characteristics of car bodies by CAE (computeraided engineering), it is necessary to examine not only the strength and fracture of welded joints such as spot welds and tailored blank welds [1][2][3][4][5], but also those of jointed steel plates of a bolted joint subjected to impact loads. There has been much work on bolted joints used in machine elements, in which strength of bolts, loosening processes and tightening torque of bolted joints are mainly examined [6,7].…”

Section: Introductionmentioning

confidence: 99%

Impact extractive fracture of jointed steel plates of a bolted joint

Daimaruya

Fujiki

Ambarita

2012

EPJ Web of Conferences

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Abstract. This study is concerned with the development of a fracture criterion for the impact fracture of jointed steel plates of a bolted joint used in a car body. For the accurate prediction of crash characteristics of car bodies by computer-aided engineering (CAE), it is also necessary to examine the behavior and fracture of jointed steel plates subjected to impact loads. Although the actual impact fracture of jointed steel plates of a bolted joint used in cars is complicated, for simplifying the problem it might be classified into the shear fracture and the extractive fracture of jointed steel plates. Attention is given to the extractive fracture of jointed steel plates in this study. The extractive behavior and fracture of three kinds of steel plates used for cars are examined in experiments and numerical simulations. The impact extraction test of steel plates jointed by a bolt is performed using the one-bar method, together with the static test. In order to understand the mechanism of extractive fracture process of jointed steel plates, numerical simulations by a FEM code LS-DYNA are also carried out. The obtained results suggest that a stress-based fracture criterion may be developed for the impact extractive fracture of jointed steel plates of a bolted joint used in a car body.

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Effect of Pre-Fatigue on Impact Tensile Properties of Laser Welded Butt Joint of High Strength Steel Plates

Cited by 8 publications

References 11 publications

Geometric features of MnS grains in damaged free-cutting steel SUM24L by fatigue and dynamic tension

Geometric features of MnS grains in damaged free-cutting steel SUM24L by fatigue and dynamic tension

Effect of fatigue damage on static and dynamic tensile behaviour of electro‐discharge machined Ti‐6Al‐4V

Impact extractive fracture of jointed steel plates of a bolted joint

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