A cleaned up Version of these notes is available at www.lstc.com/sdb/393 _________________________________________________________________________________ A seminar on this topic is periodically offered. See https://www.dynamore.de/en/training/seminars/metal-forming/introduction-to-welding-simulation Introduction to Welding Simulation (Thomas Kloppel, thomas.kloeppel@dynamore.se) Due to recent developments in LS-DYNA, the complete welding process can be captured. In this regard, the numerical simulation can be performed in several stages where, for instance, the cooling process as well as the associated warping of the structural components can be computed after each welding stage. Moreover, the choice of a suitable material law also allows considering microstructural transform- ations in the welding zone itself or in the heat-affected zone. The resulting residual stress states and any remaining plastic strains can then be taken into account both in the next welding stage as well as in a subsequent usability simulation. With these features at hand, it is possible to virtually represent the entire process chain. The aim of this seminar is to give the participants a brief introduction to the thermo- mechanical coupled simulation with LS-DYNA. Herein, the required forms of heat sources and transfer for a successful welding simulation will be discussed and their definition in LS-DYNA is shown. ___________________________________________________________________________________ More References: http://www.dynalook.com/14th-international-ls-dyna-conference/connections/recent-developments-for-welding-simulations-in-ls-dyna-r-and-ls-prepost-r "Recent Developments for Welding Simulations in LS-DYNA and LS-PrePost", 14th International LS-DYNA Users Conference, 2016. Loose, T., "DynaWeld - Welding and Heat-Treatment with LS-DYNA: Distortion - Residual Stress - Microstructures", Information Day Welding, DYNAmore Gmbh, Stuttgart, Germany, April, 2015. http://www.dynamore.de/en/downloads/infodays/dokumente/download-informationstag-schweissen2015/2015-infoday-welding-07-dynaweld.pdf Ticket#2017112110000096 _________________________________________________________________________________________ RE: Modeling of weld effects. Weld effects may include degradation of surrounding material as well as deformation and residual stress induced by welding. Three approaches are described. The approach you use depends on the objective of your weld analysis. ------------------------------------------------------- I. Degradation of surrounding material only. If you happen to know (or can estimate) the variation of material properties as a function of distance from a weld, you only need to do a mechanical analysis that includes the HAZ (Heat Affected Zone) feature. See the following 2 commands: 1. *DEFINE_HAZ_PROPERTIES: Blank properties (yield stress and failure strain) are modified based on proximity to various types of spot welds (solid spotweld, beam spotweld, or *constrained_spotweld) or a line weld. Examples: http://ftp.lstc.com/anonymous/outgoing/support/EXAMPLES/define_haz_properties.k http://ftp.lstc.com/anonymous/outgoing/support/EXAMPLES/define_haz_properties2_pset.k Use a negative curve ID in *DEFINE_HAZ_PROPERTIES to normalize ordinate by the spotweld diameter. Example: http://ftp.lstc.com/anonymous/outgoing/jday/haz_properties_negcurve.k 2. *DEFINE_HAZ_TAYLOR_WELDED_BLANK: Defines the location of a line weld as referred by *DEFINE_HAZ_PROPERTIES. Example: http://ftp.lstc.com/anonymous/outgoing/jday/coupon_mat24.haz_tailor_welded_blank.finer.k.gz The HAZ capability only works with materials defined using the STOCHASTIC option. ------------------------------------------------------- II. Effects including deformation due to heating caused by welding. RE: *BOUNDARY_THERMAL_WELD(_TRAJECTORY) An example of a coupled thermal/mechanical analysis featuring *BOUNDARY_THERMAL_WELD to model a moving heat source is here... http://ftp.lstc.com/anonymous/outgoing/support/EXAMPLES/weld_2_nodes_skew.k.gz . When you postprocess the results, scale up displacements by 100 to better see the deformation pattern from the heating. A newer command, *BOUNDARY_THERMAL_WELD_TRAJECTORY, is more flexible and easier to use than regular *boundary_thermal_weld. For a description of this command and an example, download http://ftp.lstc.com/anonymous/outgoing/support/EXAMPLES/ShellWelding.zip and http://ftp.lstc.com/anonymous/outgoing/support/PRESENTATIONS/BoundaryThermalWeldTraj.pdf http://ftp.lstc.com/anonymous/outgoing/support/EXAMPLES/thermal_weld_trajectory.2welds.k.gz has 2 welds. The 2nd weld lags behind the 1st weld by 0.5 seconds. If you're unfamiliar with thermal analysis in LS-DYNA, some very basic information about thermal analysis and coupled thermal/mechanical analysis is provided in the "LS-DYNA Thermal Guide" at www.lstc.com/download/manuals. RE: *BOUNDARY_TEMPERATURE_RSW Purpose: Define temperature boundary conditions within an ellipsoidal region of the solid or shell structure. Temperatures are prescribed to nodes found in a region defined by this keyword. The boundary condition is tailored to represent the so-called weld nuggets evolving during resistive spot welding (RSW) processes. It is applicable for a thermal or coupled thermal/structural analysis. http://ftp.lstc.com/anonymous/outgoing/support/EXAMPLES/bnd_temp.k.gz is a test case for *BOUNDARY_TEMPERATURE_RSW. It is a thermal-only simulation with two spot welds. The first is in the contact zone of two solid blocks, the second in the contact zone of a solid block and a shell part. Naturally, the temperature distribution in and around the weld nuggets is of interest. The example runs with trunk double precision versions in SMP and MPP. tk, 1/25/19 ------------------------------------------------------- III. Laying down of weld material, including thermal effects. (a) Example featuring *boundary_thermal_weld, *mat_cwm (mat_270), and *mat_thermal_cwm: http://ftp.lstc.com/anonymous/outgoing/support/EXAMPLES/boundary_thermal_weld_mat_cwm.k.gz (b) Example featuring LSPP's Welding Simulation tool (Applications > Tools > Welding Simulation): The type of welding simulation the weld application in LSPP focuses on is the use of a moving heat source which activates the material when heated up to melting point. It simulates the solidification of the filler material when cooling, heat conductivity/radiation, structural deformation due to heat, residual stresses and remaining deformation after the weld has been made. It is almost necessary to have a special tool to set up the order of in which the welds are created, when doing multi-stage welding. It explains the motivation, reason and the purpose of the welding application in LSPP. The purpose for the welding interface is not to set up the entire model from scratch. LSPP has a fully flegded keyword editor, various ways to create meshes and so on and there is actually no need to include everything of that in to the welding application in LSPP. The welding application only focuses on setting up the properties and the motion of the weld heat source. It also gives a very good help in setting up and/or changing the order of which the welds are created. It will also give you quite a lot of recommended control cards for running the analysis. The recommended/suggested control cards are given in the LSPP installation_directory/templates/control_welding.k and control_cooling.k. (6/23/16, Ticket#2016062110000151) The documentation is a bit limited, but we are working on a tutorial and we will probably have it ready when the *BOUNDARY_THERMAL_WELD_TRAJECTORY keyword is officially released in version R10. In the meantime, I have prepared an archive for you that contains a small movie, LS-PREPOST weld setup file, a ppt presentation of CWM in LS-DYNA and the complete set of LS-DYNA input file that you can run in consecutive order. You can download the archive from: https://project.dynamore.se/public/5c2d27 (I put this zip file in http://ftp.lstc.com/anonymous/outgoing/support/EXAMPLES/tjoint.zip). Description of the files: t_joint_weld_gui.mp4 – Short movie about how to setup the Weld process using the GUI tjoint_setup.wld – Process input to the Weld GUI. Import by pressing Load in the sequence folder. tjoint.k – LS-DYNA input file (will not run without running it through the GUI) Weld_LS-DYNA_LSPREPOST.pdf – Description on CWM using LS-DYNA and LS-PrePost. control*.k – Control files written by LS-PrePost. Folders 1.1/1.2/2.1/2.2/3.1 are the tjoint model run through LS-PREPOST. Folders denoted *.1 are welding simulations. *.2 are cooling simulations. 3.1 is the springback simulation. The simulations need to be run in consecutive order. Thus, first run 1.1/run.k then 1.2/run.k and so on. mikael.schill@dynamore.se anders.jernberg@dynamore.se Ticket#2017042110000091 _______________________________________________________________________ Following is from Jim Kennedy in LS-PrePost User Group... See if these presentations can be of some help: Schill, M., and Jernberg, A., “Weld Simulation in LS-DYNA and LS-PrePost”, DYNAmore Nordic Offshore Workshop, Gotenberg, Sweden, November, 2015. http://ftp.lstc.com/anonymous/outgoing/support/PRESENTATIONS/LS-PREPOST_CWM_pre-processor.pdf Loose, T., and Mokrov, O., “SimWeld and DynaWeld Software Tools to Setup Simulation Models for the Analysis of Welded Structures with LS-DYNA”, 10th European LS-DYNA Users Conference, Wurzburg, Germany, May, 2015. https://www.dynamore.de/de/download/papers/2015-ls-dyna-europ/documents/sessions-e-5-8/simweld-and-dynaweld-software-tools-to-setup-simulation-models-for-the-analysis-of-welded-structures-with-ls-dyna Loose. T., “Basics of Welding Simulation and Heat Treatment Simulation: Applications and Benefits”, Infotag Schweissen und Warmebehandlung, DYNAmore GmbH, Stuttgart, Germany, April, 2016. https://www.dynamore.de/de/download/presentation/dokumente/download-informationstag-schweissen2016/02-2016-04-dynamore-informationstag-welding-basics.pdf July 20, 2017