Laser-MIG hybrid welding to aluminium alloy carbody shell for railway vehicles

Yonetani, Hiroshi

doi:10.1080/09507110802465050

Cited by 17 publications

(4 citation statements)

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“…Compared with the upper part of the joint, more pores with equivalent diameter less than 15 μm denoted by a solid line (1) can be observed at the joint bottom. Meanwhile, very limited gas pores larger than 40 μm can be found inside welded joints, as indicated by a dashed line (2).…”

Section: Pore Characterizationmentioning

confidence: 99%

“…Peak‐hardened 7000 series aluminum alloys conventionally used into aerospace industries have currently been attempted for high‐speed railway components, such as sleeper beams, axle boxes, and pantographs . To improve the structural integrity, more attentions should be paid on the higher fatigue resistance of such high‐strength alloys due to welding, casting, and 3D printing .…”

Section: Introductionmentioning

confidence: 99%

“…Nomenclature: σ p0.2 , yield strength; σ b , ultimate tensile strength; A, tensile fracture elongation; P Laser , laser power; I Arc , arc current; U Arc , arc voltage; v Hybrid , hybrid welding speed; Δ, defocusing distance; η Laser , welding heat efficiency for laser; η Arc , welding heat efficiency for arc; E′, welding heat input per unit length; R, stress ratio; f , frequency; t, specimen thickness; a, crack length; N, number of cycles; da/dN, fatigue crack growth rate; ΔK, stress intensity factor range; Ψ, sphericity; Φ, equivalent diameter; √area, the square root of projected area of a pore perpendicular to the maximum principal stress; σ max , maximum nominal stress; N f , cycles to failure; h, distance from the nearest pore point to the free surface; σ eff , maximum effective stress in case of R = −1; γ, the empirical constant in Walker equation; σ, remote stress; E, Young's modulus; v, Poisson's ratio; s, distance from the pore centroid to the free surface; r, radius of pore; K t , stress concentration factor; σ′ max , maximum local stress; Δσ, stress range; r * , distance ahead of pores dominated by crack initiation; ρ, local radius of pore; Δσ e , endurance limit; N i , crack initiation life; α, fatigue life exponent; ζ, fatigue life coefficient; ΔK, stress intensity factor range; Ω, computational domain; Γ 1 , outer boundary of computational domain; Γ 2 , inner boundary of computational domain; Π e pore , elemental functional due to pore; Π e crack , elemental functional due to crack; σ, stress tensor; u, displacement tensor; t, traction tensor; S, elastic compliance matrix; D, matrix differential operator relevant strain to the displacement; K e pore , element stiffness matrix for a pore-embedded polygonal element; K e crack , element stiffness matrix for a crack-embedded polygonal element; G, integral along the outer boundary Γ 1 ; H 1 , integral along the matrix boundary Γ 1 ; H 2 , integral along the matrix boundary Γ 2 ; T, transformation matrix of local coordinate to global coordinate; d, distance from the pore centroid to crack tip; W, model width; K I,e , stress intensity factor of mode I cracking problem in case of a primary crack with a pore; K I,0 , stress intensity factor of mode I cracking problem in case of a primary crack without a pore; K I , the stress intensity factor for mode I cracking; K II , the stress intensity factor for mode II cracking 1 | INTRODUCTION Peak-hardened 7000 series aluminum alloys conventionally used into aerospace industries have currently been attempted for high-speed railway components, such as sleeper beams, axle boxes, and pantographs. 1,2 To improve the structural integrity, more attentions should be paid on the higher fatigue resistance of such highstrength alloys due to welding, casting, and 3D printing. [2][3][4] However, defects such as gas pores and hot cracks cannot be completely eliminated by high energy density beam welding despite subjected to optimum processing parameters and suitable filler metals.…”

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confidence: 99%

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Fatigue behaviors of laser hybrid welded AA7020 due to defects via synchrotron X‐ray microtomography

Song

Ding³

et al. 2019

Fatigue Fract Eng Mat Struct

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Defect or shrinkage is known to have a detrimental effect on the fatigue resistance of casting lightweight alloys and additively manufactured or 3D printed materials. However, very few works focus on the damage mechanism of fusion welded Al alloys due to gas pores or metallurgical defects. This paper performs an investigation on the effect of porosity on the damage evolution of laser hybrid welded 7020‐T651 alloys. The critical pore size comparable with average weld grain was assumed in terms of the population and dimension of micropores. To characterize the coupling effect between gas pores and cracks, an in situ fatigue testing rig was developed to well work at the synchrotron radiation tomography system. Combining synchrotron X‐ray microtomography and fatigue resistance testing, the pore size and location were correlated with the crack initiation and crack growth path but relatively less on the long crack propagation rate. Furthermore, the interaction between the porosity and stress concentration was elucidated by using finite element simulations, which shows that the gas pore appears to be a preferred cracking site especially near the surface.

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Section: Pore Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Fatigue behaviors of laser hybrid welded AA7020 due to defects via synchrotron X‐ray microtomography

Song

Ding³

et al. 2019

Fatigue Fract Eng Mat Struct

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“…To meet the needs of modern railway transportation, light weight and high speed has become more important. Now most high speed trains use the aluminum with medium and high strength, covering the advantages of reducing the weight of trains, saving the traction consumption, saving operating cost [1] . Because most of the external forces some important parts are undertaking during daily work are cyclic loading, the fatigue life of welding parts is of great importance.…”

Section: Introductionmentioning

confidence: 99%

Comparison for the Test Methods of Fatigue Life of Welded Structures

Yuan

Xie

2014

AMM

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Taking the local parts of high-speed training service as the research object, the static form of the finite element model is established, and the dangerous parts of the stress distribution under different load form corresponding to loading and displacement conditions applied in experimental test is calculated. Fatigue life of the same welding parts of the different forms due to the state of the uniaxial tensile and the bending is respectively tested in the lab, the life distribution and characteristics of their statistics are obtained; Compared to the stress distribution of dangerous parts and data of the test, analysis that the similar parameters of life and failure forms can be received if it choose the reasonable load parameters in different form and loading in the test.

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