Papers by Keyword: Spot Weld

Abstract: The engineering parts joining by the spot welding require acceptable properties to survive the loading conditions XE "temperature". Several studies show that the welding variables have an effect on the properties of spot nugget XE "nugget" and on the future cracking. This review summarizes the resistance spot welding process (RSW). It introduces the basic spot welding principles, experiments XE"experiments" , limitation and defects XE "defects". The new concepts and awareness were presented. The results from the series of scientific works and literature are discussed. The metal’s weldability, XE "spotweldability" strength, XE"strength" and fracture are the main topics in several structural analysis. The welding variables effect on the mechanical properties and performance XE "mechanicalproperties" of the structures is the key analysis. In general, the increasing of the heat input by adjusting the current, time, and pressure producing higher weld area in turn enhance the toughness. However, by increasing the weld area, the defects and cracking tend to appear. Hence, a desired weld size with the mechanical properties is required. The nugget fracture mode is changing from plug or button tearing to shear failure mode depending on the weld properties. The crack grows either from the internal defects or around the nugget.

Abstract: One of the main concerns of the automotive industry is reduction in structural weight of automobiles. Reduction of weight on vehicles has been proven to lower the usage of fuel, and therefore save a lot of energy in order to move from one place to another. At the same time, reduction of weight often means reduction in material usage, often regarded to be threatening structural strength of parts, components or vehicles body in white (BIW). Truss Core Panel, which has been developed from the study of origami engineering, specifically plane-tilings and space fillings, is a suitable candidate because it can be produced from thin sheet metals and can be joined using spot welding. In this paper, method for evaluating truss core panels for crashworthiness has been established based previous research on crashworthiness evaluation on thin shells. The effect of different configuration of spot welding has been investigated. The number of spot weld (n) along central member and side members of truss core panel has been varied and modeled from n = 2, 4, 6 ... to n = 30, and compared to a truss core panel model that is fully welded along central member and side members. The results also show that it is possible to attain similar mean crush force to fully welded structure with smaller number of spot welds.

Abstract: The mode shape change of tension shear spot welds with propagation of crack was studied. Mode shape would change as crack exists, while the change is not so explicit. Difference between uncracked and cracked model modal shapes showed violent changes, but not give enough information of the crack location. Further Difference between two neighbouring points also can give information of crack, but also not saliently. Combination of the two would give explicit crack location information of the crack for tension shear spot welds.

Abstract: Finite element (FE) modeling of laser welds for dynamic analysis is a research issue because of the complexity and uncertainty of the welds and thus formed structures. A Bayesian probabilistic framework incorporating MCMC for updating the parameters of a spot weld structure model was presented, cooperation of finite element program and multiple chains sampling technology was realized, and statistical characteristics of structural parameters were obtained. Distribution ranges of the three frequencies were predicted based on parameter estimation. Numerical simulation indicates that there are little changes in standard deviations of posterior distribution compared to prior distribution, the posterior mean values are in good agreement with the corresponding measured average values. The convergence indicates the techniques feasibility and effectiveness. The present work offers an alternative approach to updating the spot weld structure parameters.

Abstract: Spot welds have been widely used in vehicle body assembly, and can affect the performance of a vehicle. This paper studies the mechanical properties of spot weld and utilizes those properties in the numerical simulation to predict the failure behavior of a spot-welded component. The mechanical properties of a spot weld are not easy to obtain due to the size of spot weld, and the non-uniformity around the weld zone. The study utilized the hardness measured on and around the spot weld, heat treated samples with the same hardness, and then performed the tensile tests on those heat treated specimens to obtain the corresponding mechanical properties. With those testing data, the numerical simulation model was then created based on the properties obtained. A single-spot-welded part was used to correlate the results of hardware tests and numerical simulation. The study compared the results of three different modeling schemes with those of the hardware test. The results showed that the simulation model with material properties assigned to their corresponding region provided better correlation with the hardware testing results.

Abstract: The effects of weld nugget size, base metal strength, mode of loading and pre-strain of base metal on the load bearing capacity of spot-welds have been investigated using two varieties of interstitial free steel sheets. The effect of bake hardening treatment after spot-welding of prestrained sheets has also been examined using an ultra low carbon bake hardening grade steel. The major results infer that: (i) the load bearing capacity of spot-welds increases with increasing nugget size and base metal strength, (ii) the load bearing capacity of spot-welds increases with increasing pre-strain of base metal, (iii) the remnant dislocation density around the spot-weld increases with increasing pre-strain, (iv) the strength of spot-welds on pre-strained sheets does not alter significantly after the baking treatment, but baking treatment increases the strength of pre-strained base metals, and (v) the location of failure is commonly at the interface of HAZ/base metal for tensile-shear specimens and at the HAZ for cross-tension specimens.

Abstract: This article firstly established two finite element models of seam weld and spot-weld for the front sub-frame, then used the two models for seam weld and spot weld fatigue simulation analysis, next cooperated with bench test results for verification. After the above steps, we not only found the weak portion of the front sub-frame, but also provide reference for both optimum design and improving the bench test design.

Abstract: This paper describes an innovative way to characterize the strength of spot welds. A wedge test has been developed to generate interfacial failures in weldments and observe in-situ the crack propagation. An energy analysis quantifies the spot weld crack resistance. Finite Element calculations investigate the stresses and strains along the crack front. A comparison of the local loading state with experimentally observed crack fronts provides the necessary data for a failure criterion in spot weld fusion zones. The method is applied to spot welds of Advanced High Strength steels.

Abstract: In order to accurately and conveniently simulate spot-weld in FEA, based on the typical specimen of stainless steel, three typical finite element models (FEM) of spot-welds have been created as analysis objects. Firstly, based on the calculation theory of the spot-weld fatigue, two sets of analytical solution, which were the maximum principle stress of the specimen around the spot-weld nugget, were obtained under the action of stretching and shearing, respectively. Then, their linear elastic FEM were established, and the stress states around the spot-weld nugget and the adjacent sheets were analyzed. Finally, according to the results compared between the analytical solution and simulation solution, it can be seen that, when the specimen was stretched, using the brick model to simulate the nugget can get the smallest absolute error of the principle stress, so its spot-weld fatigue damage is the most consistent with the actual situation, a stiff beam model followed, and an umbrella model is the worst; when the specimen was sheared, using the brick model to simulate the nugget can also get the smallest absolute error of the principle stress, so its spot-weld fatigue damage is also the most consistent with the actual situation, the umbrella model is followed, and the stiff beam model is the worst. The results show that appropriate selection of spot-weld FEM is extremely essential for fatigue life prediction under the initial design of products.

Abstract: A procedure that makes use of a conventional stress value (ERS) is applied to spot welded joints. The ERS can be evaluated for every spot weld of the structural model. Through the use of ERS-N curves, fatigue data performed on different joint geometries can be successfully mixed together. One of the main aspects is that progressive damage deeply influences fatigue behaviour, so that a simple numerical solution neglecting accumulated damage is unable to foresee the whole fatigue life. In the present paper the method has been applied to many experimental results: it is shown that a unique criterion is able to deal with several different structures and materials.