Fatigue strength assessment of laser stake-welded T-joints using local approaches

Frank, Darko

doi:10.1016/j.ijfatigue.2014.11.009

Cited by 16 publications

(16 citation statements)

References 29 publications

(75 reference statements)

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“…6,7 Further investigation revealed that by using local approaches the fatigue strengths of laser stake-welded T-joints are in very good agreement at 2-5 million cycles despite the different stress states at the notch tip, namely the pure tension or the combination of tension and shear stresses. [10][11][12] This obtained fatigue strength at 2-5 million cycles was also in the agreement with other steel joints from the literature. [13][14][15][16][17][18][19] It was further observed that the fatigue resistance curves based on the J-integral as the fatigue strength parameter can have slope values of 4 and 9 under tensile and bending loading in the weld, respectively.…”

supporting

confidence: 90%

“…4c. 14 The large slope values obtained in this study and the previous investigation 11,12 are likely to be related to the high stress concentration at the notch tip, 11 which is especially pronounced under bending loading as in the case of this study. The same difference in slopes can be observed for the nominal stress approach, i.e.…”

Section: R E S U L T S a N D Discussionsupporting

confidence: 58%

“…5 The same study 5 showed that this rotational (bending) stiffness of the joint has a significant variation along the weld line. [10][11][12] This obtained fatigue Fig. 6,7 The common observation in the fatigue tests involving T-joints is that the joint fails by a fatigue crack propagating through the weld regardless if the stresses are tensile or bending.…”

mentioning

confidence: 85%

“…[13][14][15][16][17][18][19] It was further observed that the fatigue resistance curves based on the J-integral as the fatigue strength parameter can have slope values of 4 and 9 under tensile and bending loading in the weld, respectively. [10][11][12] The contributions [6][7][8][9][10][11][12] were investigating fatigue resistance of the T-joints only considering the load ratio R = 0. However, a joint in the web-core panel can also be subjected to other ratios like R = À1.…”

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confidence: 99%

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Fatigue strength assessment of laser stake‐welded T‐joints subjected to reversed bending

Frank

Dissel

Remes

et al. 2016

Fatigue Fract Eng Mat Struct

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The paper investigates the fatigue strength of laser stake‐welded T‐joints subjected to reversed bending. The fatigue tests are carried out with the load ratio, R ≈ −0.8. The experimental data is firstly analysed using the nominal stress approach and then by the J‐integral as the local fatigue strength parameter in the finite element (FE) assessment. The nominal stress approach demonstrated that the fatigue strength of the investigated T‐joints is lower than encountered for any other steel joint under reversed tensile loading. The results also showed that the fatigue strength of this joint under the load ratio R ≈ −0.8 increases with respect to R = 0 bending by 22.6% in the case of the nominal stress approach and 13% in the case of the J‐integral approach. However, the slopes of the fatigue resistance curves for different load ratios appear very similar, suggesting that the load ratio has an insignificant influence to the slope. In contrast to the similar slopes, the scatter indexes were different. The nominal stress approach shows that the scatter index is 3.4 times larger for R ≈ −0.8 than R = 0 bending. The J‐integral approach showed that the scatter index for R ≈ −0.8 is only 67% larger than in the R = 0 case because the weld geometry is modelled in the FE analysis.

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confidence: 90%

Section: R E S U L T S a N D Discussionsupporting

confidence: 58%

mentioning

confidence: 85%

mentioning

confidence: 99%

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Fatigue strength assessment of laser stake‐welded T‐joints subjected to reversed bending

Frank

Dissel

Remes

et al. 2016

Fatigue Fract Eng Mat Struct

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“…For T-joint structures, adhesive bonding or the welding process is usually employed to join the skin and stringer [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on Electric Current-Aided Laser Stake Welding of Aluminum Alloy T-Joints

Zhang

Chen

et al. 2017

Metals

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Abstract:In the present study, aluminum alloy T-joints were welded using the laser stake-welding process. In order to improve the welding quality of the T-joints, an external electric current was used to aid the laser stake-welding process. The effects of the process parameters on the weld morphology, mechanical properties, and microstructure of the welded joints were analyzed and discussed in detail. The results indicate that the aided electric current should be no greater than a certain maximum value. Upon increasing the aided electric current, the weld width at the skin and stringer faying surface obviously increased, but there was an insignificant change in the penetration depth. Furthermore, the electric current and pressing force should be chosen to produce an expected weld width at the faying surface, whereas the laser power and welding speed should be primarily considered to obtain an optimal penetration depth. The tensile shear specimens failed across the faying surface or failed in the weld zone of the skin. The specimens that failed in the weld of the skin could resist a higher tensile shear load compared with specimens that failed across the faying surface. The microstructural observations and microhardness results demonstrated that the tensile shear load capacity of the aluminum alloy welded T-joint was mainly determined by the weld width at the faying surface.

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Fracture mechanics based estimation of fatigue lives of laser welded joints

Goyal¹,

Bogdanov

El-Zein

et al. 2018

Engineering Failure Analysis

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The conventional joining methods like resistance spot welding and arc welding have several challenges during joining of thin sheets of high strength steel materials. One of the main challenge is that application of these joining methods may result in a severe distortion of welded structure. Therefore laser welding process has emerged as an alternative joining process which can help mitigate some of these challenges. Lower heat input from laser during the welding process results in a smaller size weld heat affected zone and also in lower overall distortion of the structure. The laser welding process presents an exciting opportunity in designing lighter weight structures. However, the major roadblock to application of laser welding method for large structural parts is that fatigue behavior of laser welded joints is not yet well understood. In order to study the fatigue performance of laser welded joints, detailed experimental and numerical investigations have been carried out and the results are presented in this work. The scope of experimental studies included a large set of coupons with different thicknesses and material combinations. Experimental fatigue test data has been generated for the laser welded joints produced using thin sheets of three grades of high strength steel materials (HSLA and UHSS grades) of several thicknesses (1mm, 1.6mm, 2mm and 3mm). The fatigue test data sets were obtained at R-ratios of R=0.1, R=0.2 and R=0.3. Another variable introduced into experimental studies was an orientation of laser weld joint with respect to applied loading direction. After fatigue tests were completed, detailed metallurgical investigations have been carried out to understand the failure mechanism and the crack growth behavior in laser welded joints. Based on the observed experimental and numerical studies it was concluded that the strain life based fatigue analysis method which has been successfully applied to study weld toe failures for the arc weld joints is not sufficient for the evaluation of laser welded joints. This is due to the reason that laser welded joints have unique challenges due to weld root crack failures and extremely high stress concentration at the location of crack initiation in the root of laser welded joints between the plates. The fracture mechanics based method has been developed for the fatigue life assessment of laser welded joints. In order to apply this method comprehensive three dimensional finite element studies were performed. Numerical studies show good correlation of the estimated fatigue lives obtained using proposed fracture mechanics method with the experimental data.

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Fatigue strength assessment of laser stake-welded T-joints using local approaches

Cited by 16 publications

References 29 publications

Fatigue strength assessment of laser stake‐welded T‐joints subjected to reversed bending

Fatigue strength assessment of laser stake‐welded T‐joints subjected to reversed bending

Experimental Investigation on Electric Current-Aided Laser Stake Welding of Aluminum Alloy T-Joints

Fracture mechanics based estimation of fatigue lives of laser welded joints

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