Strength of three-sheet spot welds with critical nugget sizes in tensile shear, cross tension, peel and fatigue tests

2021 ◽  
pp. 146442072110663
Author(s):  
K Siimut ◽  
MFR Zwicker ◽  
CV Nielsen
Keyword(s):  
Ductile Fracture ◽  
Thin Sheet ◽  
Fatigue Tests ◽  
Weld Strength ◽  
Tensile Shear ◽  
Spot Welds ◽  
Load Range ◽  
Tension Tests ◽  
Lower Load ◽  
Cross Tension

Plug failures have been observed in three-sheet spot welds, where the weld nugget did not penetrate into the outer sheet. Such solid-state bonds were found to be formed as a result of high contact pressure and temperature during welding. The strength of single spot welds was studied in a three-sheet combination (0.61 mm DX54 on two 1.21 mm DP600) with nugget penetrations into the thin sheet below 40%. The static strength was evaluated by tensile shear, cross tension and mechanized peel testing, and fatigue tests were carried out in tensile shear configuration at 30 Hz and mean load of 2 kN. It was found that loading of the specimens in tensile shear, mechanized peel and cross tension tests leads to a plug failure and a ductile fracture of the thin sheet. The weld strength is not correlated with the nugget penetration into the thin sheet but is determined by the area of the bonded interface, instead, as shown by peel and cross tension tests. Fatigue tests revealed that the specimens break by a plug failure. The failure mechanism was found to be ductile for the highest load range after approximately 33 000 cycles. At lower load ranges, evidence of a crack was found in the DX54 sheet, leading to higher stress concentration and subsequent ductile fracture. It was estimated that a load range of 940 N leads to failure after approximately 106 cycles.

Investigations on the Mechanical Behavior of Advanced High Strength Steels Resistance Spot Welds in Cross Tension and Tensile Shear

2010 ◽  
Vol 89-91 ◽  
pp. 130-135 ◽  
Author(s):  
Sylvain Dancette ◽  
Véronique Massardier-Jourdan ◽  
Jacques Merlin ◽  
Damien Fabrègue ◽  
Thomas Dupuy
Keyword(s):  
Three Dimensional ◽  
High Strength Steels ◽  
Complex Loading ◽  
High Strength ◽  
Weld Strength ◽  
Tensile Shear ◽  
Spot Welds ◽  
Advanced High Strength Steels ◽  
Cross Tension ◽  
Failure Types

Advanced High Strength Steels (AHSS) are key materials in the conception of car body structures, permitting to reduce their weight while increasing their behavior in crash conditions. Nevertheless, the weldability of AHSS presents some particular aspects, in that complex failure types involving partial or full interfacial failure can be encountered more often than with conventional mild steels during destructive testing, despite high spot weld strength levels. This paper aims at characterizing the behavior of different AHSS spot welds under two quasi-static loading conditions, tensile shear and cross tension, often used in the automotive industry for the determination of their weldability. Interrupted cross tension and tensile shear tests were performed and spot welds failure was investigated with optical micrographs, SEM fractography and 3D-tomography in order to follow the three-dimensional crack paths due to the complex loading modes. A limited number of failure zones and damage mechanisms could be distinguished for all steel grades investigated. Moreover, numerical simulation of the tests was used to better understand the stress state in the weld and the influence of geometrical features such as weld size on the occurrence of the different failure types.

scholarly journals Comparison of Modified Mohr–Coulomb Model and Bai–Wierzbicki Model for Constructing 3D Ductile Fracture Envelope of AA6063

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Jianye Gao ◽  
Tao He ◽  
Yuanming Huo ◽  
Miao Song ◽  
Tingting Yao ◽  
...  
Keyword(s):  
Ductile Fracture ◽  
Fracture Criterion ◽  
Fracture Strain ◽  
Stress Triaxiality ◽  
Ductile Fracture Criterion ◽  
Forming Process ◽  
Tension Tests ◽  
Wide Range ◽  
Round Bar ◽  
Fracture Envelope

AbstractDuctile fracture of metal often occurs in the plastic forming process of parts. The establishment of ductile fracture criterion can effectively guide the selection of process parameters and avoid ductile fracture of parts during machining. The 3D ductile fracture envelope of AA6063-T6 was developed to predict and prevent its fracture. Smooth round bar tension tests were performed to characterize the flow stress, and a series of experiments were conducted to characterize the ductile fracture firstly, such as notched round bar tension tests, compression tests and torsion tests. These tests cover a wide range of stress triaxiality (ST) and Lode parameter (LP) to calibrate the ductile fracture criterion. Plasticity modeling was performed, and the predicted results were compared with corresponding experimental data to verify the plasticity model after these experiments. Then the relationship between ductile fracture strain and ST with LP was constructed using the modified Mohr–Coulomb (MMC) model and Bai-Wierzbicki (BW) model to develop the 3D ductile fracture envelope. Finally, two ductile damage models were proposed based on the 3D fracture envelope of AA6063. Through the comparison of the two models, it was found that BW model had better fitting effect, and the sum of squares of residual error of BW model was 0.9901. The two models had relatively large errors in predicting the fracture strain of SRB tensile test and torsion test, but both of the predicting error of both two models were within the acceptable range of 15%. In the process of finite element simulation, the evolution process of ductile fracture can be well simulated by the two models. However, BW model can predict the location of fracture more accurately than MMC model.

scholarly journals Experimental studies on the possibility of using a pulsed laser for spot welding of thin metallic foils

2020 ◽  
Vol 10 (1) ◽  
pp. 674-680
Author(s):  
Piotr Sęk
Keyword(s):  
Experimental Studies ◽  
Pulsed Laser ◽  
Welding Process ◽  
Pulse Mode ◽  
Weld Strength ◽  
Spot Welds ◽  
Butt Welding ◽  
Strength Tests ◽  
Metallic Foils ◽  
The Impact

AbstractThe purpose of the experiment was to study the influence of the laser beam in pulse mode on metallic foils in order to obtain a spot weld. The welding process was carried out using the overlap weld method, using spot welds in various quantities. The Nd - YAG BLS 720 pulsed laser was used to conduct the experiment. The impact of the number of spot welds on the value of force needed to break the sample was examined. A number of measurements were carried out to determine the best process parameters. Butt welding and overlap welding were also performed using a continuous weld consisting of spot welds. Weld strength tests were performed to select the most appropriate parameters for the process under consideration.

scholarly journals Investigations on arc brazing for galvanized heavy steel plates in steel and shipbuilding

2021 ◽  
Author(s):  
Philipp Andreazza ◽  
Andreas Gericke ◽  
Knuth-Michael Henkel
Keyword(s):  
Low Cost ◽  
Thin Sheet ◽  
Steel Structures ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Steel Plates ◽  
Galvanized Steel ◽  
Filler Materials ◽  
Static Tensile ◽  
Brazed Joints

AbstractArc brazing with low-melting copper-based filler materials, which has long been established and standardized in the thin sheet sector, offers numerous advantages in the processing of predominantly electrolytically galvanized steel structures. In steel and shipbuilding, on the other hand, equipment parts made of thick steel sheets are hot-dip galvanized at low cost and with good corrosion-inhibiting properties. Quality welding of such constructions is not possible without special precautions such as removing the zinc layer and subsequent recoating. With regard to greater plate thicknesses, arc brazing was analyzed in these investigations as an alternative joining method with regard to its suitability for practical use. Within the scope of the investigations, CuSi3Mn, CuMn12Ni2, and four different aluminum bronzes were examined on different sheet surface conditions with regard to the geometrical and production parameters. This was carried out by build-up and connection brazing, executed as butt and cross joints. Quasi-static tensile tests and fatigue tests were used to assess the strength behavior. In addition, metallographic analyses are carried out as well as hardness tests. The suitability for multi-layer brazing and the tendency to distortion were also investigated, as well as the behavior of arc brazed joints under corrosive conditions.

Characterisation of the plane anisotropy and its effect on interstitial free steel thin sheet metal forming simulation

2021 ◽  
pp. 146442072110534
Author(s):  
Latifa Arfaoui ◽  
Amel Samet ◽  
Amna Znaidi
Keyword(s):  
Thin Sheet ◽  
Rolling Direction ◽  
Tensile Tests ◽  
Interstitial Free ◽  
Experimental Database ◽  
Forming Simulation ◽  
Hardening Law ◽  
Tension Tests ◽  
Interstitial Free Steel ◽  
Thin Sheet Metal

The main purpose of this paper is to study the orthotropic plastic behaviour of the cold-rolled interstitial free steel HC260Y when it is submitted to various loading directions under monotonic tests. The experimental database included tensile tests carried out on specimens (in the as-received condition and after undergoing an annealing heat treatment) cut in different orientations according to the rolling direction. A model was proposed, depending on a plasticity criterion, a hardening law and an evolution law, which takes into account the anisotropy of the material. To validate the proposed identification strategy, a comparison with the experimental results of the planar tension tests, carried out on specimens cut parallel to the rolling direction, was considered. The obtained results allowed the prediction of the behaviour of this material when it is subjected to other solicitations whether simple or compound.

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