3D FE Simulations Of Resistance Spot Welding
3D FE Simulations Of Resistance Spot Welding >>> https://geags.com/2tEskG
RSW is a complicated process that involves mechanical, thermal, electrical, and metallurgical phenomena [11]. The primary numerical approach to RSW deformation is based on the electrical-thermal-mechanical coupling analyzing method [12,13,14]. Many coupling analyses have been conducted to investigate weld-nugget formation [15,16,17]. However, the coupling analysis requires (i) a lengthy computing time to predict the structure deformation due to a lot of spot welds, (ii) temperature-dependent physical properties, and (iii) accurate modeling of the contact between welding electrodes and the welded materials to transfer the electric current.
There are two main steps in the RSW process, the electrode pressure step and the welding step. It is necessary to classify the inherent deformation modes induced by the electrode pressure step and welding step so that spot weld deformation induced by complicated phenomena can be expressed using a simple methodology as opposed to the conventionally inherent strain method [30].
where, {D*} and {Dm} are inherent deformation vectors of (Sri*, Szi*,Rri*) and measured visible welding deformation vectors of (Srim, Szim,Rrim), respectively. [H*] is the elastic response matrix. The jth column of [H*] is obtained from the results of the elastic analysis with the jth component of {D*} as 1 and the others as zero [28]. The magnitude of the three inherent deformation modes of the single spot-weld specimen was identified using the changes of the measured distance and angle between the measuring points located on the top and bottom surfaces as shown in Figure 8.
Abstract:In recent years, increasing automotive safety by improving crashworthiness has been a focal point in the automotive industry, employing high-strength steel such as press hardenable steel (PHS). In addition to the improved strength of individual parts in the body of the vehicle, the strength of the resistance-spot-welded joints of these parts is highly important to obtain a safe structure. In general, dimensions of weld nuggets are regarded as one of the criteria for the quality of spot-welded joints. In the presented research, a three-dimensional axisymmetric finite element model is developed to predict the nugget formation in resistance spot welding (RSW) of two types of PHS: the uncoated and AlSi-coated 1.8 mm boron steel after hot stamping. A fully coupled electro-thermo-mechanical analysis was conducted using the commercial software package Abaqus. The FE predicted weld nugget development is compared with experimental results. The computed weld nugget sizes show good agreement with experimental values.Keywords: hot stamping; resistance spot welding; AlSi coating; nugget size; coupled electro-thermo-mechanical analysis
A novel clinch-resistance spot welding method of dissimilar materials was presented. A group of punch-die electrodes was used to weld 1-mm 5083 Al alloy and 1-mm galvanized steel sheets. Microstructure and mechanical properties of the welded joints obtained with punch-die electrodes were studied. Stress is analyzed by numerical simulation, and the tensile shear strength distribution under different welding parameters is analyzed using artificial neural network. A cup section is formed after welding, which results in 3D connection of the bonding interface. Stress concentration on the steel/Al contact surface locates on the connection between the punch tip and die tip. The melt zone is mainly formed at the nugget edge, and a relatively small melting area is generated at the central area on the Al side. The maximum failure load can be increased to 4.5 kN. The range of parameters for obtaining high strength is relatively wide in clinch-resistance spot welding, and the interaction of current and time has a significant effect on the strength.
1. N. Zeleznik et al., Modeling the Pseudoelastic Design Space of NiTi Fabricated by Laser Powder Bed Fusion, Additive Manufacturing, 103472 (2023) , free access through April 23, 2023 courtesy of Elsvier2. J.K. Semple et al., Temperature-Dependent Material Property Databases for Marine Steels - Part 3: HSLA-80. Integr Mater Manuf Innov (2022). -022-00288-x3. U. Shah et al., Computational analysis of the ultrasonic effects on resistance spot welding process, Journal of Manufacturing Processes, Volume 81, 2022, Pages 191-201. 4. X.K., Zhu et al., Data-driven models of dynamic strength of resistance spot welds in high strength steels by regression and machine learning. Multiscale and Multidisciplinary Modeling, Experiments and Design. (2022). -022-00123-y5. J.K. Semple et al., Temperature-Dependent Material Property Databases for Marine Steels - Part 2: HSLA-65. Integrating Materials and Manufacturing Innovation, Vol. 11, pp. 13-40 (2022). -021-00246-z
The aim of this work is the modeling of coupled electric and heat processes in a system for spot resistance welding of cross-wire reinforced steel bars. The real system geometry, dependences of material properties on the temperature, and changes of contact resistance and released power during the welding process have been taken into account in the study.
Spot resistance welding (SRW) has been known for a long time as very widely applicable in a variety of industrial areas where it is possible to automate the production process. The great technological advantages: high efficiency, precision and simplicity [1,2,3,4,5] of SRW makes it very attractive and especially widespread in the automobile manufacturing industry, in robotic assembly lines, in some orthodontist clinics, in battery production, etc. The considerable and sustained interest in this type of welding is due to the exclusive feature of the method to inject a large amount of energy exactly into the zone specified for welding in a very short time interval (milliseconds), without excessive heating of the rest of the workpieces. The proper control of the processes, however, is particularly important and obligatory for its use in automated, high-tech production lines [6].
The aim of the work is precise analysis of the processes taking part in a system for contact resistance welding of cross-wire reinforced steel bars. As a starting point and a base for the studies, previous experimental [12] and theoretical [13, 14] investigations of the same system have been considered. The detailed 3D computer modeling of the coupled AC electric and transient thermal field distribution is carried out using the finite element method (FEM) and COMSOL Multiphysics 5.2 software package [15]. The novelty of the study is that the electric and thermal field distributions in the welding region are modeled for several successive time stages of the welding process, corresponding to the change of contact spot area, related contact resistance and reduction of the released power.
The welding principle of the studied system is illustrated in Figure 1. The system consists of two electrodes and two cross-wire steel bars. The two electrodes hold together with additional force the steel bars that are to be welded, while at the same time an alternating current is applied in the system for a short time. The large welding current concentrated into a small spot region causes release of a large amount of thermal power, proportional to the resistance between the electrodes. The contact area is heated by the released energy, which causes softening, melting, and bonding of the metals. Of specific importance is the fact that, because of the material softening, followed by melting and enlarging of the contact zone, the contact resistance and released power are significantly changed during the welding.
The processes taking part in the considered system are a complex of interrelated electric, thermal, mechanical and physicochemical phenomena. The present investigation is based on the analysis of coupled electric and thermal field distributions, studied for several successive time stages, corresponding to the change of contact spot area, related contact resistance, and reduction of the released power, occurring simultaneously with the creation of contact between the welded workpieces.
The mathematical formulation of the problem includes determination of the governing equations, boundary conditions, and the field sources corresponding to changes of the contact area dimensions, contact resistance, and released power, depending on the welding time.
In order to take into account the specific changes in the contact spot area during the welding process, resulting in changes of the material state and properties, overlapping dimensions, and released power, a corresponding contact resistance has been introduced in the numerical modeling. The layer impedance and relevant overlapping are specified on the basis of preliminary experimental investigations [12], and boundary conditions have been introduced accordingly in the model with the given equations below [15]:
Determination of the field sources, corresponding to the contact area, contact resistance, and released power is based on the previous experimental [12] and theoretical [13] investigations. Although the theoretical approach (based on electrical analogy of heat transfer) was quite different from that used in the present work, the main assumptions about the dimensions of the affected contact region, corresponding contact resistance, and power change during the welding stages are accepted in the present study.
The FEM modeling of the electric and thermal field distribution during the welding process is carried out for the three stages, taking into account the real 3D geometry of the studied region and dependences of material properties on the temperature. The contact resistance determined on the basis of experimental and theoretical investigation of the system was has also been introduced in the FEM model.
The electric field modeling is presented in the study by a map of electric potential distribution for three different RMS values of the applied in the modeling curr