Welding Simulation

Plasma Arc Welding (PAW) is one of the important arc welding processes used in electronics, medical, automotive and aerospace industries due its high accuracy and ability of welding any hard materials. Though PAW is more complex and requires more expensive equipment compared to other commercial arc welding processes, it finds application in automotive sectors. In automotive applications, titanium metal is used particularly in motorcycle racing, where weight reduction is critical while maintaining high strength and rigidity.  Titanium is in the group of reactive metals, which means that they have a good affinity for oxygen and readily forms an oxide layer leads to oxygen embrittlement.  Therefore, the welding of titanium sheets is still an emerging technology in automotive sectors. The present investigation deals with the numerical simulation of plasma arc welding of 2 mm thick Ti-6Al-4V alloy using Finite Element code COMSOL. A Modified Three Dimensional Conical (MTDC) heat source model and a newly developed heat source model are considered for performing the numerical simulation to predict the temperature distribution on thin sheets of titanium alloy. The temperature dependent material properties of Ti-6Al-4V such as thermal conductivity, specific heat and density are used for performing the numerical analysis.  Based on the results, it is observed that the predicted weld bead geometry from the temperature distribution plots using newly developed heat source model is in good agreement with the corresponding experimental result.

In automobile industry, automobile welding fixture is a component which is important to auxiliary welding. The automobile body is welded by multiple complex sheet metal parts and other auxiliary work pieces. In this process, supporting role of welding fixture is an important role. In manufacturing of car, Truck, welding fixture was designed and analyzed briefly. The design of fixture demands extensive use of heuristic knowledge, which is also coupled. For instance, when define the machining operations of manufacturing parts in assembling of fixture solution should be kept in mind and vice versa. Fixture designers have a skill and experience for several years, in achieving proper fixture designs. In the Automobile Industry, BIW (Body In White) is the common terminology used to mention the car sheet metal welded structure (body shell). Sub-assemblies like Floor body, Body side, Left Hand Side/ Right Hand Side, Front End, Roof etc. gets welded together by various metal joining process e.g. resistance spot welding. The welding fixtures are holding devices of assemblies of Car body they have different operations (reverting, welding, and stud) of geometric of car body structure. Keyword: Welding Fixture; Welding Technique; Uses of software in design of fixture Catia; Fides; Unigraphics; I. INTRODUCTION The fixture is a special tool for holding a work piece in proper position during manufacturing operation. For supporting and clamping the work piece, device is provided. Frequent checking, positioning, individual marking and non-uniform quality in manufacturing process are eliminated by fixture. This increase productivity and reduce operation time. Fixture is widely used in the industry practical production because of feature and advantages. To locate and immobilize workpieces for machining, inspection, assembly and other operations fixtures are used. A fixture consists of a set of locators and clamps. Locators are used to determine the position and orientation of a workpiece, whereas clamps exert clamping forces so that the workpiece is pressed firmly against locators. Clamping has to be appropriately planned at the stage of machining fixture design. The design of a fixture is a highly complex and intuitive process, which require knowledge. Fixture design plays an important role at the setup planning phase. Proper fixture design is crucial for developing product quality in different terms of accuracy, surface finish and precision of the machined parts in existing design the fixture set up is done manually, so the aim of this project is to replace with hydraulic fixture to save time for loading and unloading of component. Hydraulic fixture provides the manufacturer for flexibility in holding forces and to optimize design for machine Operation as well as process function ability.

This article shows the impact of welding transformer and electrode tip on weld nugget formation in resistance spot welding (RSW). The impact is shown in weldability lobe, a graphical presentation of the acceptable welding parameters set that may results in acceptable weld quality. Understanding of welding equipment and its system is the key for welding parameters optimization process in selecting the best welding parameters that meeting design specification at minimum cost.

Welding is a widely used process in industry because welding techniques have some striking features which are included in this project. In other way of saying, welding techniques will be so important in human life in the future because of their unique specialties. For this reason, researches and studies on welding are increasing day by day.
Welding is used in different areas in industry and it has various features. Welding is especially used in the manifacturing area, as a connector between materials in the existence of heat and pressure (with or without additional materials). The main targets in this process are; lowest cost, highest satisfaction in performance and longest life.
In this project, the importance of choosing a suitable production regarding to the intended features and how to improve the mechanical features, tried to be explained. Therefore, the welding process which is going to be applied to the materials which has different metal content, are virtually modelled by using Ansys Workbench software.
Parameters as, used materials and chosen welding techniques within this project are widely explained.  Experimental studies were done in order to help the project to enlighten the future studies and to make the project based on numerical data (simplifies prooving). In the other parts of the experimental studies, welding process is applied to the materials which have different metal contents by using Ansys Workbench software. Modelling a material using different welding techniques before production gives  more practical and more proactive vision.

N, den Uijl: Thermal and electrical resistance in resistance spot welding. Proceedings of the 17th International Conference Computer Technology in Welding and Manufacturing; 18 – 19 June 2008; Cranfield University, Cranfield, UK. ISBN 13-978-1-903761-07-6.

In Resistance Spot Welding (RSW) heat generated by a current passing through a series of thermal
and electrical resistances of metal sheets is used to melt material and form a weld. This paper reports
on research work conducted at Corus RD&T on mechanisms involving thermal and electrical
resistance in RSW and how they interact.
The goal of the work is twofold:
• To get a better understanding of how various material properties influence the weldability of
steels in RSW. These results can be used to support the development of new spot weldable
steel grades .
• To investigate the impact of various material properties on the simulation results. Material
properties can be very cumbersome and expensive to determine. Therefore, better
understanding of material properties from simulations saves money by cutting unnecessary
work.
First an overview is given of the physics underlying the thermal and electrical resistances in resistance
spot welding. The actual investigation is done using a verified RSW model. Experimental results are
used to support the simulation results. Additionally, these results are used to establish the level of
accuracy needed for material data used in RSW simulations.
The results can be used to increase the accuracy of weld modelling simulations. The results will also
enable manufacturers to use simulation more efficiently in the set up of their production process.
Finally the results can save costs by cutting unnecessary determinations of material properties

The aim of this study is to realize a simulation of arc welding using Finite Elements Analysis (FEA). In general, thin steel metals are used in the automotive and machine industries and the distortion after arc welding is more evident, because of the lack of quality in the product this creates problems. It is important to predetermine these problems before welding process. One way of the prediction of welding process is "try and see". But this may need high cost and time. Therefore, Finite Element Method is very often used today to monitor and predict the welding process. In order to do this, MSC.Marc-Mentat program was used to simulate the arc welding process by 3-D modeling in terms of temperature distribution and distortions. Then, the results of experiments were compared to that of obtained in the simulation. The comparison of the results revealed familiarity between the presented FE model and experiments

Due to the increasing use of thin plates in lightweight welded structure, welding induced buckling may occur in such thin plate welded structure. In this study, welding induced buckling of thin plate welded structure is investigated using the eigenvalue analysis and elastic Finite Element (FE) analysis based on inherent deformation theory, and the mechanism of welding induced buckling is clarified.

Uijl, NJ den, Smith, S, Nishibata, H, Okada, T, Uchihara, M & Fukui, K (2008). Prediction of post weld hardness of advanced high strength steels for automotive application using a dedicated carbon equivalent number. IIW-1873-07. Welding in the world, 52(11/12), 18-29.

Weldability of advanced high strength steels in automotive manufacturing is a key issue. There are two important aspects to weldability: producing the welds and the quality of the welds. Producing the welds concerns the process to be used, possible addition of filler materials, the electrodes to be used, et cetera. Weld quality concerns the performance of the welds in a construction (e.g. strength and crash). With advanced high strength steels issues arise with increasing strength levels concerning the weld-quality. Traditionally carbon equivalent numbers are used to predict weldability. These traditional carbon equivalent numbers are not sufficient to predict post weld hardness of advanced high strength steels. Sumitomo Metal Industries and Corus cooperate to research weldability of advanced high strength steels. This paper concentrates on the influence of the chemical composition on weldability, as a first step to assess weldability of advanced high strength steels. This is done in two steps. First the traditional use of carbon equivalent numbers to predict weldability is explored. Literature is reviewed and possible issues with welding of advanced high strength steels are identified. Next the application of carbon equivalent numbers to predict post weld hardness for various welding processes (e.g. laser beam welding and resistance spot welding) is discussed. A wide range of steels was evaluated experimentally to determine the relationship between chemical composition and post weld hardness. The influence of welding processes expressed in terms of the cooling rates. The results are combined into simple models to predict post weld hardness of advanced high strength steel joints.

Uijl, NJ den (2006). Modelling the influence of resistance spot welding on material properties. In W. Lucas & V.I. Makhnenko (Eds.), Proc. Joint Int. Conf. "16th Int. Conf. Computer Technology in Welding and Manufacturing" and "3rd Int. Conf. Mathematical Modelling and Information Technologies in Welding and Related Processes" (pp. 306-313). Kiev, Ukraine: E.O. Paton Electric Welding Institute of the NAS.

Uijl, NJ den & Anwar, MA (2006). Mathematical modelling of weld phenomena 7. In H. Crejak, H.K.D.H. Bhadeshia & E. Kozeschnik (Eds.), Laser weld induced microstructural changes in automotive bodysheet (pp. 309-326). Graz: Verlag der Technischen Universitat Graz.

Nick den Uijl: “Resistance spot welding of a complicated joint in new advanced high strength steel” in Proceedings of the 6th International Seminar on Advances in Resistance Welding (Hamburg, Germany); Wenqi Zhang, Kim Pedersen, Ralf Bothfeld & Jörg Eggers (ed.); pp. 40-54. 2010.

Due to the increasing use of thin plates in lightweight welded structure, welding induced buckling may occur in such thin plate welded structure. In this study, welding induced buckling of thin plate welded structure is investigated using the eigenvalue analysis and elastic Finite Element (FE) analysis based on inherent deformation theory, and the mechanism of welding induced buckling is clarified. Bead-on-plate welding is first examined. Measured out-of-plane welding distortion indicates that saddle type buckling is produced after cooling. Eigenvalue analysis shows the computed lowest buckling mode is the saddle type and the corresponding critical force is less than the applied tendon force evaluated by Thermal-Elastic-Plastic (TEP) Finite Element (FE) analysis beforehand. Using elastic Finite Element (FE) analysis in which all components of inherent deformation are used and also considering initial deflection, out-of-plane welding distortion is predicted with high accuracy compared with measurement. It is also concluded that tendon force (longitudinal inherent shrinkage) is the dominant reason of buckling and it determines the buckling mode, and initial deflection and inherent bending are considered to be disturbances which trigger buckling. Later, a thin plate stiffened welded structure with fillet welded joints is examined. Although welding did not induce buckling of plate fields in bending modes in the considered thin plate stiffened welded structure, the whole stiffened welded structure buckles in a twisting mode, while plate panels remain unbuckled. Eigenvalue analysis gives the twisting buckling mode as the lowest buckling mode. However, in stiffened welded structures, not only tendon force (longitudinal inherent shrinkage) but also transverse inherent shrinkage is responsible for buckling. The good agreement between computed and measured out-of-plane welding distortion shows that the elastic Finite Element (FE) analysis using inherent deformation theory is an advantage of the computational approach to predict welding distortion in large-scale and complex welded structure with enough computational accuracy.

Superconducting (SC) Radio frequency cavity plays a vital role in High intensity SC proton linac. At RRCAT work is ongoing to develop technology for fabrication of 650MHz five-cell SCRF cavities. These cavities are fabricated using high RRR Niobium material and joined by electron beam welding. Weld shrinkages and deformation during Electron beam (EB) welding, specially at iris and stiffing ring locations, affects the RF frequency. Proper weld parameter development and their optimization is one of the key factor in successful cavity fabrication to control and predict these deformations. Efforts have been made to simulate and analyse the weld parameters using Simufact weld software. As a case study simulation of beam tube linear butt joint of five-cell SCRF cavity has been carried out. Studied the maximum temperature of the fusion zone and cool-down time cycle (thermal cycle plot) of the weld joint estimated. The results of simulation, weld fusion zone cross section has been co-related with the micrograph of EB welded test coupon sample. This paper presents the weld parameter optimization, simulation results and their experimental verification.

In spot welding process, process parameters optimization means improve spot welding quality while reduce operational cost especially power consumption and welding consumables. Lobe curve generators (weldability lobe simulator) may assist welding engineers and technicians to select the best welding parameters according to their requirements.

In automotive applications welding is increasingly one of the first, as well as one of the last production steps. Where traditionally welding during assembly would prove to be important for the distortion it could cause in a finely designed structure, in modern car-manufacturing a weld produced in an early production stage (e.g. T.W.B.'s or tubes) is carried through a sequence of production steps. Therefore in these modern applications the changes induced in the material through welding could have a profound influence on subsequent production steps. Change in hardness may affect stamping tools. In additionally changes in microstructures may affect formability. A good example is hydroforming where tubes are formed from sheet material through roll bending after which the tubes are sealed with a weld. These tubes are subsequently hydroformed. They form important structural elements that have to be able to meet high demands on issues as fatigue and crash. Lacking information, the cu...

Uijl, NJ den, Smith, S, Moolevliet, T, Goos, C, Aa, EM van der & Veldt, T van der (2008). Failure modes of resistance spot welded advanced high strength steels. In W Zhang & N Scotchmer (Eds.), Proceedings 5th International Seminar on Advances in Resistance Welding, Toronto, Canada, 24-26 September 2008 (pp. 78-104). Denmark & Canada: Swantec Software and Engineering ApS & Huys Industries Ltd.

Sheet steels are typically made using an oxygen (BOF) or electric arc furnace (EAF). Due to differences between raw materials and process, EAF steels have higher N, Si, Cu, Cr, Mo, Ni, and Sn contents compared to similar grades of BOF steels. As well, steel chemistries will slightly vary when produced by different mills. Automotive companies are concerned that these natural variations impact weldability through increased susceptibility to hot cracking, hardenability, or changing thermal and electrical properties. So there has been resistance to accepting EAF made steels and full source approvals are often needed if there are changes to the steelmaking process. This study explores these concerns. SORPAS was used to calculate the effect chemistry variation has on material properties and weldability. As well, the affect of chemistry variation due to steelmaking technique was tested by comparing the weld morphology and hardness of EAF and BOF made materials.

The local stress concentrations around the discontinuities and the weld defects are fairly common. In this study, the investigation of thickness and stress concentration effects on fatigue strength (FAT) have been studied. The fracture mechanics tools and fracture analysis code (Franc2D) were used to consider these effects. The FE simulation of welded joints will provide a tool to determine the regions of stress concentration which in turn determine the crack initiating and FAT. Unfortunately, these tools are unable to calculate FAT at higher thicknesses. Therefore, the crack length was corrected with a suitable scale. The determination of fracture toughness values without the need to undertake experiments have been presented.

In this work, the parameters stress intensity factor (SIF), initial and final crack lengths (a i and a f), crack growth parameters (C and m), and fatigue strength (FAT) are investigated. The determination of initial crack length seems to be the most serious factor in fatigue life and strength calculations for welded joints. A fracture mechanics approach was used in these calculations based on SIF which was calculated with the finite element method (FEM). The weld toe crack was determined to be equal to 0.1 mm, whereas the weld root crackÕs length was varied depending on the degree of the weld penetration. These initial crack length values are applicable for all types of joints which have the same crack phenomenon. As based on the above calculated parameters, the new limits of FAT for new geometries which are not listed yet in recommendations can be calculated according to the current approach.

This article shows the impact of welding transformer and electrode tip on weld nugget formation in resistance spot welding (RSW). The impact is shown in weldability lobe, a graphical presentation of the acceptable welding parameters set that may results in acceptable weld quality. Understanding of welding equipment and its system is the key for welding parameters optimization process in selecting the best welding parameters that meeting design specification at minimum cost.

Purpose-AA2014 is a copper-based alloy and is typically used for production of complex machined components, given its better machinability. The purpose of this paper was to study the effects of variation in weight percentage of ceramic Al 2 O 3 particulates during electrical discharge machining (EDM) of stir cast AA2014 composites. Scanning electron microscopy (SEM) examination was carried out to study characteristics of EDMed surface of Al 2 O 3 /AA2014 composites. Design/methodology/approach-The effect of machining parameters on performance measures during sinker EDM of stir cast Al 2 O 3 /AA2014 composites was examined by "one factor at a time" (OFAT) method. The stir cast samples were obtained by using three levels of weight percentage of Al 2 O 3 particulates, i.e. 0 Wt.%, 10 Wt.% and 20 Wt.% with density 1.87 g/cc, 2.35 g/cc and 2.98 g/cc respectively. Machining parameters varied were peak current (1-30 amp), discharge voltage (30-100 V), pulse on time (15-300 ms) and pulse off time (15-450 m s) to study their influence on material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR). Findings-MRR and SR decreased with an increase in weight percentage of ceramic Al 2 O 3 particulates at the expense of TWR. This was attributed to increased microhardness for reinforced stir cast composites. However, microhardness of EDMed samples at fixed values of machining parameters, i.e. 9 amp current, 60 V voltage, 90 m s pulse off time and 90 ms pulse on time reduced by 58.34, 52.25 and 46.85 per cent for stir cast AA2014, 10 Wt.% Al 2 O 3 /AA2014 and 20 Wt.% Al 2 O 3 /AA2014, respectively. SEM and quantitative energy dispersive spectroscopy (EDS) analysis revealed ceramic Al 2 O 3 particulate thermal spalling in 20 Wt.% Al 2 O 3 /AA2014 composite. This was because of increased particulate weight percentage leading to steep temperature gradients in between layers of base material and heat affected zone. Originality/value-This work was an essential step to assess the machinability for material design of Al 2 O 3 reinforced aluminium metal matrix composites (AMMCs). Experimental investigation on sinker EDM of high weight fraction of particulates in AA2014, i.e. 10 Wt.% Al 2 O 3 and 20 Wt.% Al 2 O 3 , has not been reported in archival literature. The AMMCs were EDMed at variable peak currents, voltages, pulse on and pulse off times. The effects of process parameters on MRR, TWR and SR were analysed with comparisons made to show the effect of Al 2 O 3 particulate contents.

N. den Uijl & S. Smith: The Influence of Electrode Geometry on Resistance Spot Welding of Advanced High Strength Steels for Automotive Applications. Proceedings of International Conference on Total Welding Management in Industrial Applications; J. Martikainen (ed.); Acta Universitatis Lappeenrantaensis 274. 3rd JOIN Conference, August 21-24, 2007, Lappeentanta, Finland. ISBN 978-952-214-413-3; ISSN 1456-4491.