Welding simulation
The welding simulation is a tool for the clarification of welding- related questions, which is based on the numerical solution of a mathematical model . The aim is, on the one hand, by replacing numerous practical attempts, to reduce costs in the company and, on the other hand, to gain information that could not be obtained via measurements or only with a very high level of effort.
introduction
For many decades, the design of welded constructions was based on empirical values and empirically determined formulas. With increasingly powerful computers and software solutions, the optimization of the welding process and properties of a welded component can also be carried out using numerical solutions. In the specialist literature, three sub-areas of welding simulation are described, which differ in their models and target values: the structure, the process and the material simulation.
Structure simulation
With the help of the structure simulation, the effect of welding on the construction is to be predicted. The determination of the distortion and the residual welding stresses are of the greatest importance, as these lead to a high reworking effort. In addition, these residual welding stresses can lead to cracks and thus a reduced service life. By comparing variants, an optimized procedure can be found, which then does justice to the diverse requirements that are placed on a design. A parameterized substitute heat source can be used to model the heat input, which is characterized by the welding process, the welding parameters and other influences. If the highest accuracy requirements are required, these parameters can be calibrated by an experimental analysis using temperature measurements. For many practice-relevant cases, however, an estimate based on empirical values from the literature is sufficient. The aim is to determine these parameters through process simulations in the future.
Process simulation
The welding process is modeled in the process simulation. When simulating fusion welding processes, a frequent goal is to determine the weld pool geometry depending on various parameters such as the shielding gas cover. Further goals are the determination of the process efficiency or the process stability. Current research fields include the modeling of the droplet transfer during MIG / MAG welding and a more realistic representation of the drop areas on the electrodes. Falling areas are the voltage jump between the electrode and the arc, as well as the arc and the workpiece.
Attempts to mathematically model the complex resistance spot welding process began as early as the 1960s. The interrelationships between electrical, mechanical and material-related influencing variables on the formation of the weld point are simulated by computer-aided models in order to make a theoretical prediction and optimization of the weld point size and the welding parameters under given conditions. A. Nied describes an axially symmetrical FEM model for the simulation of the process during the lead, welding and hold time. In this model, such effects as:
- Changes in resistance
- Thermal conductivity
- local deformation
- Transition effects between electrode and workpiece
- Water cooling
- Heat conduction and radiation into the environment
considered. With increasing computing power and refined modeling - such as the inclusion of surface properties - simulation software has been developed for a wide variety of welding process variants. Today different software systems are available for practical use.
- SimWeld (process simulation)
- ANSYS (general FEM system)
- SORPAS (simulation of resistance spot welding)
- DynaWeld (structure simulation)
- Simufact (structure simulation, process simulation)
Further research fields exist in the area of process simulation of solid-state welding processes, such as friction stir welding and rotational friction welding.
Material simulation
The aim of the material simulation is to investigate the microscopic and macroscopic influences on the material in the melting zone and the heat-affected zone (HAZ) through the thermal effects of welding. The tendency towards hot and cold cracking is of particular importance in practice .
Textbooks
- D. Radaj: Welding process simulation . DVS Verlag, 1999, ISBN 3-87155-188-0 .
- D. Radaj: Residual stress and distortion in welding: calculation and measurement methods. DVS Media, 2001, ISBN 3-87155-194-5 .
- CV Nielsen: Modeling of thermo-electro-mechanical manufacturing processes. Springer, London / New York 2013, ISBN 978-1-4471-4642-1 .
Web links
- bam.de : Federal Institute for Materials Testing and Research, Working Group on Welding Simulation and Arc Welding
- isf.rwth-aachen.de : Institute for Welding Technology and Joining Technology at RWTH Aachen University, working group
- uni-weimar.de/Bauing/stahlbau/SimEx : Bauhaus University Weimar, junior professorship for simulation and experiment
- MA Ninshu and MURAKAWA Hidekazu : Numerical and Experimental Study on Nugget Formation in Resistance Spot Welding for High Strength Steel Sheets in Automobile Bodies , Transactions of JWRI, 38 (2009), 2
Individual evidence
- ↑ ISF-Direkt Nr.27, RWTH Aachen University (PDF; 352 kB): Diagram of areas of fall between electrode and workpiece using the example of an aluminum weld
- ^ HA Nied: The Finite Element Modeling of the Resistance Spot Welding Process. In: Welding Research Supplement. April 1984, pp. 123s-132s.