Welding Simulation Research Articles

Numerical simulation of crack in a residual stress field

Fracture mechanics analysis of metallic material is unequivocally one of the principal areas in the study of the failure of materials. The effect of residual stress on failure is often overlooked and usually not considered during the design stage. However, residual stress plays a crucial role in determining the failure of materials. This work studies the behaviour of a crack in a residual stress field. A residual stress field in a welded plate is obtained by finite element simulation of fusion welding. Subsequently, a stationary crack is introduced in the welded plate. J-integral is used to characterize the crack behaviour. The variation in J-integral values with the welding residual stress is studied. It is observed that crack behaviour and stress distribution in a residual stress field depend on the magnitude of primary stress in the material.

Numerical Simulation of Welding Temperature Field, Stress Field, and Strain Field of Fillet Joint in Different Welding Sequence

For welding temperature field, stress field, and strain field in fillet joints, using the double ellipsoid heat source, the ABAQUS software platform is used to simulate and analyze the welding process of fillet joints with four different application sequences. By setting up observation points, the study analyzed the distribution of the temperature field, stress field, and strain field of the simulated welding process for these four application cases. The results show that in the vertical weld direction, the welding sequence has a large effect on the transverse residual stress; the use of isotropic welding, butt weld first and then welded fillet weld program, the maximum total deformation and angular deformation produced are the smallest.

Experimental Investigations and Finite Element Simulation of Friction Stir Welding of Various Aluminium Alloys AA2024 and AA2519

Abstract: In friction stir welding (FSW), a rotating spherical leg tool is forced to plunge into the plates to be welded and moved along their contact line. The tool penetrates into the work pieces. During this operation, frictional heat that’s generated by contact friction between the tool and work piece. The plasticized material is stirred by the tool and forced to “flow’’ to the side and the reverse of the tool advantage as the temperature cools down, a solid nonstop joint between the two plates is than formed. In this project work, DEFORM -3D is used to perform the finite element analysis and experimental investigation on the FSW in order to predict residual stresses, temperatures, normal stresses and distortion of the welded structures, that are induced during FSW of the given airframe structures made up of AA 2024 and AA 2519. The weld quality characteristics like hardness, and tensile strength properties of the joints are analyzed

Supporting Imaging of Austenitic Welds with Finite Element Welding Simulation—Which Parameters Matter?

The basic principle of ultrasound is to relate the time of flight of a received echo to the location of a reflector, assuming a known and constant velocity of sound. This assumption breaks down in austenitic welds, in which a microstructure with large oriented austenitic grains induces local velocity differences resulting in deviations of the ultrasonic beam. The inspection problem is further complicated by scattering at grain boundaries, which introduces structural noise and attenuation. Embedding material information into imaging algorithms usually improves image quality and aids interpretation. Imaging algorithms can take the weld structure into account if it is known. The usual way to obtain such information is by metallurgical analysis of slices of a representative mock-up fabricated using the same materials and welding procedures as in the actual component. A non-destructive alternative to predict the weld structure is based on the record of the welding procedure, using either phenomenological models or the finite element method. The latter requires detailed modelling of the welding process to capture the weld pool and the microstructure formation. Several parameters are at play, and uncertainties intrinsically affect the process owing to the limited information available. This paper reports a case study aiming to determine the most critical parameters and levels of complexity of the weld formation models from the perspective of ultrasonic imaging. By combining state-of-the-art welding simulation with time-domain finite element prediction of ultrasound in complex welds, we assess the impact of the modelling choices on the offset and spatial spreading of defect signatures. The novelty of this work is in linking welding simulation with ultrasonic imaging and quantifying the effect of the common assumptions in solidification modelling from the non-destructive examination perspective. Both aspects have not been explored in the literature to date since solidification modelling has not been used to support ultrasonic inspection extensively. The results suggest that capturing electrode tilt, welding power, and weld path correctly is less significant. Bead shape was identified as having the greatest influence on delay laws used to compute ultrasonic images. Most importantly, we show that neglecting mechanical deformation in FE, allowing for simpler thermal simulation supplemented with a phenomenological grain growth loop, does not reduce the quality of the images considerably. Our results offer a pragmatic balance between the complexity of the model and the quality of ultrasonic images and suggest a perspective on how weld formation modelling may serve inspections and guide pragmatic implementation.

Microstructural evolutions and impact toughness in simulated welding heat affected zones for a high-strength carbide-free bainitic rail steel

Systematic experimental investigations were conducted to study the microstructures and impact toughness of each heat affected zone (HAZ) formed during rail flash-butt welding. A high-strength carbide-free bainitic rail steel was subjected to different thermal simulation cycles to separately reproduce each HAZ subzone by tailoring the peak temperature (PT) with respect to 700, 850, 920, 1000 and 1350 °C, and hence to generate the corresponding microstructures by using Gleeble-3500 simulator. Results show that the HAZ subzones exhibit complicated microstructures depending on the PTs, and with increasing PT the dominant bainitic microstructure type evolves from polygonal bainitic ferrite (700 °C) to a mixture of fine bainitic ferrite and granular bainite (850–1000 °C), and finally to coarse bainitic ferrite and granular bainite (1350 °C). Impact tests demonstrate that the impact toughness initially increases significantly as the PT reaches 920 °C (i.e., fine-grained HAZ), beyond which the impact toughness starts to decrease. The fine-grained HAZ displays optimal impact toughness in HAZs, yet which is lower than the base metal. Moreover, the morphology and distribution of martensite-austenite (M-A) constituents is strongly dependent on the welding PT, and the high fraction blocky and coarse slender M-A constituents is considered to be detrimental for the impact toughness.

Finite element simulation prediction of repeated bending failure zone of roll-welded bellows based on an equivalent welding model

In this paper, an equivalent welding model is proposed that takes the tensile stress and strain parameters of the axial weld area of the roll-welded bellows as the material properties to replace welding simulation. The integrated finite element method is used to simulate the following two model forming processes for the roll-welded bellows: (i) welding-bulging-repeated bending model, and (ii) equivalent welding-bulging-repeated bending model. The stress and strain distributions of the two models are compared and analyzed, and the main failure areas of the roll-welded bellows in the repeated bending process are predicted. At the same time, the accuracy of the model prediction is verified by the limited repeated bending test of the roll-welded bellows, and the failure mechanism of the roll-welded bellows is revealed. The results indicate that the stress and strain distributions of the two models are essentially the same, thus verifying the feasibility of the equivalent welding model. When the cyclic deformation reaches the limit, the predicted stress failure risk zone is located at the base metal position of the first wave-like trough of the bellows near the heat affected zone at the fixed end, which is consistent with the experimental results. This indicates that the equivalent welding-bulging-repeated bending model can accurately predict the position of the repeated bending fatigue failure of the bellows, thus laying a foundation for the optimization of the roll-welded bellows.

Investigation on Corrosion Behavior of Simulated Welding HAZ for 22 pct Cr Lean Duplex Stainless Steel With Different Mn/N Ratio Addition

Investigation on Corrosion Behavior of Simulated Welding HAZ for 22 pct Cr Lean Duplex Stainless Steel With Different Mn/N Ratio Addition

Enhancing welding strength of thermoplastic vulcanizate/aluminum alloy via adding zinc methacrylate

Welding of metals and polymer materials has always been one of the difficult problems. In this work, we incorporated zinc methacrylate (ZDMA) to polypropylene/ethylene propylene diene rubber thermoplastic vulcanizate (PP/EPDM TPV) to improve the welding performance of the TPV and A6061-t6 aluminum alloy (6061). We firstly processed a welding simulation experiment on a flat vulcanizer. In the experiment of simulating heat source, ZDMA effectively improved the strength of TPV/6061 joints, and the strength of the joints with 30 phr (parts per hundreds of rubber) ZDMA increased tenfold compared to that with 5 phr ZDMA. The increase of joint strength was the result of the combined effect of TPV's polarity, dimensional stability, and interfacial chemical bonds. The results of X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) showed that: during the welding process, the carboxylate ions (-COO-) of ZDMA in TPV migrated to the interface of TPV/6061 joints and constructed chemical bonds (C–O–Al) with 6061. Then, we welded the TPV and 6061 using a Friction Stir Spot Welding (FSSW) machine, the strong interface strength (tension-shear load = 1.2 kN) between TPV and 6061 verified our simulation experiment. Furthermore, the knowledge in this work will benefit the research in welding of TPV and lightweight metals to improve the strength of the interface between plastics and metals.

Physical Simulation and Numerical Simulation of Flash Butt Welding for Innovative Dual Phase Steel DP590: A Comparative Study.

In this study, the microstructure and performance of newly designed dual-phase steel (DP590) after joining by flash butt welding (FBW) for vehicle wheel rims was analysed and compared by two simulations, i.e., physical simulation and numerical simulation, due to the high acceptance of these two methodologies. Physical simulation is regarded as a thermal-mechanical solution conducted by the Gleeble 3500 simulator and which can distribute the heat-affected zone (HAZ) of the obtained weld joint into four typical HAZs. These are coarse-grained HAZ, fine-grained HAZ, inter-critical HAZ and sub-critical HAZ. A combination of ferrite and tempered martensite leads to the softening behaviour at the sub-critical HAZ of DP590, which is verified to be the weakest area, and influences the final performance due to ~9% reduction of hardness and tensile strength. The numerical simulation, relying on finite element method (FEM) analysis, can distinguish the temperature distribution, which helps us to understand the relationship between the temperature distribution and real microstructure/performance. Based on this study, the combination of physical and numerical simulations can be used to optimise the flash butt welding parameters (flash and butt processes) from the points of temperature distribution (varied areas), microstructure and performance, which are guidelines for the investigation of flash butt welding for innovative materials.

Resistance insert spot welding: a new joining method for thermoplastic FRP–steel component

Recently, multi-material designs consisting of metal and FRP components are being increasingly used in vehicle body structures to reduce weight and thus energy consumption and emission. Because the most commonly used resistance spot welding (RSW) technology for body assembly cannot be applied to join sheet metals and FRPs, the usage of FRPs is strongly limited. Therefore, a new resistance insert spot welding (RISW) method was developed. During the manufacturing process of FRPs, here compression molding of PA6 GF40 materials, specially designed steel inserts are directly integrated into the FRP part. Later, via the steel inserts, the FRP part can be spot welded to other steel parts in the structure. In this work, the design and development process of RISW is presented. Starting with the design concept of inserts, welding tests were conducted, and the parameters for the welding simulation were calibrated. After that, the detailed insert design was performed using welding simulation and tests with several restrictions, such as insert dimensions, the temperature in FRPs, the weldability range, and joining strength. In the end, an appropriate insert geometry was found, which met all requirements. The mechanical properties of RISW joining are better than or equal to those of SPRs. The new RISW technology was also demonstrated on a real vehicle component. A seat cross member was designed using FRP with 42% weight reduction and produced by compression molding with 30 simultaneously integrated inserts. The cross member was finally successfully welded to a steel closing plate using RISW.

Numerical Simulation of Laser Transmission Welding-A Review on Temperature Field, Stress Field, Melt Flow Field, and Thermal Degradation.

Laser transmission welding (LTW) is an excellent process for joining plastics and is widely used in industry. Numerical simulation is an important method and area for studying LTW. It can effectively shorten the experimental time and reduce research costs, aid in understanding the welding mechanism, and enable the acquisition of ideal process parameters. To enhance understanding of numerical simulation studies on LTW and facilitate research in this area, this paper presents a comprehensive overview of the progress made in numerical simulation of LTW, covering the following aspects: (a) characteristics of the three heat source models for LTW temperature field simulation, including surface heat source model, volumetric heat source model, and hybrid heat source model, along with the methods, results, and applications of temperature field simulation based on these models and experimental validation; (b) numerical simulation of thermal and residual stresses based on the temperature field; (c) numerical simulation of the melt flow field; and (d) predictive simulation of material degradation. The conclusion of the review and the prospects for further research work are eventually addressed.

Profiling hardness and microstructural evolution in the soft zone of 1.25Cr-0.5Mo heat-resistant steel subjected to varied creep durations

Simulated welding has been employed to precisely locate and track the soft zone of 1.25Cr-0.5Mo heat resistant steel. Hardness and microstructural variations in the soft zone subjected to designed creep durations have been systematically explored. It has been demonstrated that, as the creep duration increases, the hardness of the soft zone gradually increases, which is primarily driven by the grain size reduction of equiaxed ferrites. In addition, population of carbide precipitates and accumulation of geometrically necessary dislocations also contribute synergistically to hardness dip.

Simulation of dissimilar friction stir welding of AA7075 and AA5083 aluminium alloys using Coupled Eulerian–Lagrangian approach

Temperature, strain and material flow during the friction stir welding (FSW) process are factors that determine the quality of the resulting joint. Examining these features by experimental methods is very difficult, so the numerical method is developed. This paper focuses on simulating the FSW of AA5083 to AA7075 aluminium alloys. At first, in order to investigate the materials mixing and also to study the microstructural properties and hardness of the samples, the samples were welded using a milling machine. Then, according to the used parameters, the process was modelled. For this reason, a Coupled Eulerian–Lagrangian (CEL) was employed to estimate thermal, strain and material mixing. Comparing the stir zone (SZ) of the joint produced and predicted by simulation revealed that the CEL approach has well-determined the material mixing in the SZ. The experimental results show that the highest hardness value is 112 HV in the thermo-mechanically affected zone of AA7075 alloy. The numerical results indicate an unequal strain distribution along the weld centre line due to the lower strength of AA5083 and a ‘positive’ interaction between the tool welding and rotational speed on the advancing side.

Numerical and Physical Simulation of MAG Welding of Large S235JRC+N Steel Industrial Furnace Wall Panel

This paper presents the results of a study on the development of a Metal active gas (MAG) welding technology for an industrial furnace component made of steel S235JRC+N with respect to the minimizationof welding deformation. A numerical simulation of the welding process was performed in the first phase of the research. The numerical simulation was carried out with the SYSWELD software. For the numerical simulation of the welding process, the FEM method was used. In the simulation, four variants of restraint of the industrial furnace wall panel elements during the execution of the welding process were investigated. They differed in the number of restraints (model 1-4). It was found that the difference between the maximum mean strain in model 1 and the lowest mean strain in model 4 was only 11%. A physical simulation of the welding process was then performed with a restraint variant according to model 1. The displacement results obtained from the physical simulation of the welding process were compared with the displacement results from the numerical simulation. Discrepancies between numerical and physical simulation displacement values were found. The quality of selected welded joints was also evaluated. Visual testing (VT) and measurements of weld geometries were performed for this purpose. Metallographic tests and hardness measurements were performed to determine of influence of the welding process on the microstructure of the welded joint area, especially the heat affected zone (HAZ). The results obtained confirm the correctness of the assumptions made regarding the technology of manufacturing the furnace wall panels.

Design of partial height web stiffeners in beam-to-column joints and influence of residual stresses induced by welding

Fixed beam-to-column joints in steel portal frames with bolted connections typically present stiffeners to ensure proper load bearing resistance and stiffness to the joint. Executing the same stiffeners with a reduced height (e.g. partial height web stiffener) allows for cost saving during manufacturing but must be paid off by considering its effects in the design verification of the joint. The usual gap size of the partial stiffener has a height of 10%–30% of the concerned element web depth. Based on the Astron product example, this study analyzes the effects of the partial stiffener on the concerned knee joint resistance components according EN1993-1-8. A numerical parametric study is performed based on an advanced 3D FEM model to determine and compare the structural behavior of the beam-to-column joints with full and partial stiffeners. Comparison of the calculation results prove, the partial stiffener influences only the shear panel resistance component, and it has no effect on other components of the joint. The failure mechanism of the shear panel using different slenderness ratios are analyzed in the paper and an enhanced design method is developed, which allow to consider the geometrical gap between the flange and stiffeners. The effect of residual stresses resulting from the manufacturing processes of the plated elements is also analyzed and introduced in the paper using advanced weld simulation technique.

Finite Element Simulation of Multi-Pass Welding of AA6061-T6 Plate-Sleeve: Effect of Different Yield Strengths of Weld and Base Metals

Finite Element Simulation of Multi-Pass Welding of AA6061-T6 Plate-Sleeve: Effect of Different Yield Strengths of Weld and Base Metals

Numerical study on local residual stresses induced by high frequency mechanical impact post-weld treatment using the optimized displacement-controlled simulation method

The High Frequency Mechanical Impact (HFMI) treatment is a reliable, effective, and user-friendly post-weld technique for fatigue life enhancement of welded structures. The working principle for HFMI can be characterized by impacts from cylindrical indenters with a high frequency which introduces the local work hardening and high compressive residual stresses (RS) and reduces the stress concentration at the weld toe. These beneficial effects are needed to be considered in the fatigue assessment and design of those HFMI-treated structures. This study proposes a multi-process numerical simulation model to estimate local RS and improved shape profiles induced by HFMI treatment in welded joints. Firstly, the welding simulation is performed by thermal-elastic-plastic finite element (TEPFE) analysis using a coarse finite element (FE) mesh model. The zooming technique is then applied to transfer simulated as-welded RS to the ultra-fine mesh used in HFMI analysis as initial stresses. Finally, the numerical analysis of HFMI-induced RS is carried out using the optimized displacement-controlled numerical simulation method. An HFMI-treated out-of-plate gusset welded joint specimen was fabricated using SM490 steel. The surface topography for the treated zone, RS before and after the HFMI process, and thermal cycles during the welding process were experimentally investigated to calibrate and validate the proposed simulation approach. Both simulated local deformed shape profiles and RS were in good agreement with the measurements. In this paper, the recommendations for FE modeling and the procedures for determining HFMI analysis parameters were discussed in detail.

Robot-Assisted Immersive Kinematic Experience Transfer for Welding Training

Human motor skills are critical for executing a variety range of tasks in construction. Traditional hands-on training is resource and labor intensive, whereas virtual training, such as video demonstrations, cannot provide trainees with egocentric kinesthetic or proprioceptive experience such as muscular engagement. It is important to develop remote training methods that can provide rich sensory feedback and leverage the trainee’s proprioception. This paper proposes a novel remote motor skill training system that can transfer experts’ kinematic and kinesthetic experience, including both positional and force experience, to novice trainees by using virtual reality (VR) and a robot arm without the physical presence of the experts. The system uses VR to simulate virtual operation scenarios and interactions to provide an immersive operation experience. The robotic system records experts’ kinematic and kinesthetic patterns and trains novices with perceptual learning. The system design was demonstrated with a welding training task. A welding simulator was built with a Unity engine and a seven-degrees-of-freedom robot arm, which provided high-fidelity welding experience and could actively guide welding trainees. It was found that the welding simulator was resilient to external disturbance and provided accurate feedback and guidance. The proposed system contributes to the design of a more embodied remote motor skill training method.

Optimization and simulation of arc welding robot parameters based on offline programming

Automatic welding is most frequently utilized in engineering and manufacturing to improve efficiency. The importance of a robot in a current welding system takes full advantage of manual welding and regulates the burden of operator duties. The virtual process affects the operator's responsibilities, bead geometry, production quality, and shop floor platform. The goal of this study is to identify the simulation process parameter that has the greatest influence on variables such arc length, speed, and duration in arc welding. The Robot Studio ABB software has been utilized to make offline programming operations and to synchronize the route configuration of virtual arc welding robot and gun on imported solid geometry. Based on parameter data gathered from the robot studio, the simufact welding simulation configured the melting efficiency and bead geometry. The two simulation numerical variables data were used as input for the optimal solution validation in multi-objective optimization. The resulting emphasis of the experiment pursued on 0.001 m thickness of stainless-steel welding material: the melting efficiency is 0.42% and 467 Nm/s arc voltages during the arc travel of 0.0207 m/s and bead sensitivity are 2.68 VM/Nm/s. The MATLAB Pareto genetic algorithm is used to optimize the arc length, arc speed, and arc duration parameters adjusted in module language edit text format, which shows the preferred parameter of selected thickness. The results show that arc length and arc speed are practical as best solution dominators, while arc time is the non-dominating solution.

Effect of laser shock processing on residual stress evolution in martensitic stainless steel multi-pass butt-welded joints

Laser shock processing (LSP) is an innovative approach, which effectively improves the mechanical behavior of metallic structures by introducing compressive residual stress. To evaluate the residual stress evolution in low-carbon 13Cr4Ni martensitic stainless steel multi-pass butt-welded joints induced by LSP, a two-step numerical simulation including welding analysis, at first, followed by LSP calculation with the simulated welding stress results being taken into account, was performed based on ABAQUS software. Effects of LSP parameters such as power density, spot size, overlapping rate and numbers of laser shock on the residual stress variations, were systematically investigated. To validate the reliability and accuracy of the numerical simulation, experiments of welding and LSP were conducted in sequence. The residual stress after welding and LSP were investigated by x-ray diffraction method. Results demonstrate that the simulated results show a good agreement with the experimental datas. The welding residual stress distribution is uneven. Larger tensile stresses appear on the weld surface and its adjacent heat-affected zone, which could be converted into high-level compressive stress after LSP. Furthermore, an ideal residual stress field can be obtained after two successive laser shocks with an overlap rate of 75% when the power density, spot diameter, and pulse width are 7.6 GW cm−2, 4 mm, and 25 ns, respectively.