The smoothed particle hydrodynamics sph method can avoid this class of problems and has been successfully applied to simulate fracture of solids. Ansys ls dyna is useful for the analysis of problems involving contact, large deformation, nonlinear materials, transient response, andor problems requiring explicit solutions. By focusing an artificial mass scaling on this domain, the critical time step may be increased substantially without significantly affecting the low. An alternative to conventional mass scaling is the selective mass scaling sms introduced by ls dyna.
Solvers like ls dyna have an automated approach of invoking mass scaling, wherein, the end user can define a certain time step value as input and the. Ansys lsdyna is useful for the analysis of problems involving contact, large deformation, nonlinear materials, transient response, andor problems requiring explicit solutions. Learning the ls dyna suite of preprocessors would probably not be a worthwhile investment of time. Usually, we use 1 2 meter per second as the tooling speed for the springback simulation while zero mass scaling or 1 to 2 times mass scaling is added. These models are often quite complex and difficult to calibrate. Technical support team at livermore software and technology corporation lstc. Selective mass scaling sms welcome to the lsdyna support. The scaling direction and factor can be specified using various methods for maximum flexibility to suit different user needs. If the pulse duration extended to 90 ms, it could take ansys lsdyna 15 to 20 hours to solve the simulation. So to summarize, ls dyna is one of the big codes alot of people use. Preprocessor software for calibration of lsdyna material. Selective mass scaling for explicit finite element analyses. These studies cover the use of selective mass scaling, increased element size and reduced number of integration points. A selective mass scaling technique, based on a linear transformation of the.
As mention in chapter one it has been shown that the thread has a significant effect on the bolt strength 2. Dynamic analysis takes mass into account general or selective mass scaling explicit analysis general time scaling explicit analysis result export for input in next simulation step full model or part of model including temperature, deformed geometry, residual stress, phase proportion and contact status springback stabilisation output settings. Fix bug in selective mass scaling when beam release conditions are used in mpp. Box 712 livermore, california 945510712 support addresses livermore software technology corporation 7374 las positas road livermore, california 94551 tel.
Study of correspondence between press hardened components and. Iterative solution technique in selective mass scaling. Excessively small stable timestep due to element small thickness. Ls dyna analysis for structural mechanics 2014 proprietary information to predictive engineering, please do not copy or distribute page 2 of 105 acknowledgements these notes were constructed from numerous sources but special thanks should be given to the following people. Study of correspondence between press hardened components.
The considered mass scaling preserves the element translational inertia, while. Due to the relatively small element size, selective mass scaling sms must be used on the bolts in full vehicle analyses for which the global timestep supersedes bolt element critical timestep. Thereby, a lot of artificial mass can be added to the system without adulterate the global solution. Effects of mass scaling hi all, im currently working using abaqus explicit to simulate a needle moving at 0. Lsdyna if problems in crashworthiness were to be properly solved. It concludes with the recent developments of sms and an overview of supported featues as well as with a short overview of some examples.
Feb 20, 2016 this is my second try to simulate incremental sheet forming in ls dyna. It is found that the user can use much large time step without affecting the springback prediction. Optionally the scaling can be performed on multiple copies of the selected elements. The finite element method fem has been extensively applied to model failure of ice but suffers from mesh distortion especially when fracture or fragmentation is involved. Recent developments in lsdyna ii john hallquist livermore software technology corporation, livermore, usa. Linear and highly non linear problems can be effectively solved. To reduce the cpu cost and improve the performance, mass scaling is often used to increase the time step size in each cycle. Automotive crashworthiness trends and challenges march. Consequently, longer run time for the simulation process is needed with explicit time integration.
Highlights explicit dynamics analysis with solidshell is of interest in many applications. When lsdyna terminates, all scratch files are destroyed. The tran option is only available when the copy element option is activated. Starting from ls dyna version 971 revision 3 and higher, users can now use a new form of mass scaling termed as selective mass scaling which is much more accurate than the default mass scaling since it does not scale the rigidbody mass. The mass of small or stiff elements is increased to prevent a very small timestep. Selective mass scaling for distorted solidshell elements in. Ls dyna calculates your solution by running over all the nodes in the model at each time step.
Lsdyna website lsdyna is a generalpurpose finite element program capable of simulating complex real. However, the associated computational cost is increased. Selective mass scaling and critical timestep estimate for. A springback compensation study on chrysler 300c stamping. The work material used in this study is aluminum 6061t6 alloy. One of the key objectives of this thesis is to document the use of ls dyna to model metal cutting, allowing other researchers to more quickly build on this work. Explicit methods are very fast as there is no matrix inversion and the mass matrix is lumped or diagonal. Rescaling the maf is a process of altering the programmed relationship between maf sensor voltage and the grams per second of air entering the engine. On the improvement of computational efficiency of smoothed. This course covers the use of ansys lsdyna inside workbench mechanical. Automotive crashworthiness trends and challenges march 28 ls. Several methods can be used with lsdyna to accomplish this.
Lsdyna iinf lsdyna rrtf default names for the output file, binary plot files, and the dump file are d3hsp, d3plot, d3thdt, and d3dump, respectively. Here only highfrequency modes are affected by the extra bulk and these only have a minor. I used the mass scaling option to help increase the computational efficiency because without mass scaling, my simulation is taking days to run. Search in access database datagridview bindingsource filter part 12 duration. When it receives the command to send the file for calculation, kklient sends the kfile to the server. Numerical solution explicit among many explicit methods, the centraldifference technique is the most popular and is used in ls dyna time. This course covers the use of ansys ls dyna inside workbench mechanical. Selective mass scaling starting from ls dyna version 971 revision 3 and higher, users can now use a new form of mass scaling termed as selective mass scaling which is much more accurate than the default mass scaling since it does not scale the rigidbody mass. Selective mass scaling sms can be used to control the required run time by increasing the model critical time step by adding artificial mass to a limited number of stiff elements like, the transverse reinforcements.
Lsdyna calculates your solution by running over all the nodes in the model at each time step. Ls dyna if problems in crashworthiness were to be properly solved. Preprocessor software for calibration of lsdyna material models. However, small step size prevents this method from being useful for routine analysis work. Selective mass scaling in ls dyna to reduce nonphysical inertia effects. Using selective mass scaling only the high frequencies are affected, whereas the low frequencies rigid body modes are not influenced. In a very simplified explanation, ls dyna will look at the total force on each node from the previous time step, use that to find the acceleration of th. One can employ mass scaling in a selective manner by artificially increasing material density of the parts you want to massscale.
This program includes kfiles into the waiting list. Ove arup and partners limited june 16 june 2014 page 64 ls dyna software 6 release notes version 971 r7. This work will give a short overview about the general possibilities of isogeometric shells in ls dyna and focus on the recent advances for the analysis of sheet metal forming applications. In developers forum, dynamore, stuttgart, germany, 2011, 2011. Bug was a matter of local vs global variables mismatch. Lsdyna periodically looks for this file and if found, the sense switch contained therein is invoked and the d3kil file is deleted. Selective mass scaling technique is proposed not affecting low order modes. The original kfile designed for calculation in lsdyna is uploaded to kklient.
Finite element simulation of orthogonal metal cutting using. Mass scaling for minimum time step size adjusting density to user defined time step size. It cuts some corners, so there are more accurate ways to do it, but this method returns good results. This work will give a short overview about the general possibilities of isogeometric shells in lsdyna and focus on the recent advances for the analysis of sheet metal forming applications. Ove arup and partners limited june 16 june 2014 page 64 lsdyna software 6 release notes version 971 r7. Ls dyna website ls dyna is a generalpurpose finite element program capable of simulating complex real. Have the same time step size for all elements by adjusting density. Selective mass scaling in explicit finite element analyses is a method to increase the critical time step by modifying the mass matrix while at the.
The simplest method is to use a large mass density for the blank. Personally, if i were to suggest something, i would push to learn msc nastran, or abaqus, since they are more broad and widely used, and would look nice in more industries. Applications of variationally consistent selective mass. Ls dyna periodically looks for this file and if found, the sense switch contained therein is invoked and the d3kil file is deleted. Starting from lsdyna version 971 revision 3 and higher, users can now use a new form of massscaling termed as selective massscaling which is much more accurate than the default massscaling since it does not scale the rigidbody mass. For an analysis using interface segments the execution line in the first analysis is given by. In a very simplified explanation, lsdyna will look at the total force on each node from the previous time step, use that to find the acceleration of th. Numerical solution explicit among many explicit methods, the centraldifference technique is the most popular and is used in lsdyna time. Single point incremental forming simulation in lsdyna youtube. The simulation result from the optimized forming simulations showed a much improved correlation with the press hardened product. Ls dyna iinf ls dyna rrtf default names for the output file, binary plot files, and the dump file are d3hsp, d3plot, d3thdt, and d3dump, respectively. Lsdyna software package is with unlimited elements and capabilities. Selective mass scaling sms this talk answers the question why sms is newsworthy and dicusses the theory and implementation behind it including the difference between cms and sms and when and how to usw sms.
Explicit method for dynamic and static nonlinear finite. Specialized features developed specifically for the automotive, aerospace, government, manufacturing industries. Neglect null beams attached to rigid bodies in the selective mass. If both the factor and dt parameters are omitted, a default mass scaling value of 1. Ansys lsdyna could solve a model in five to seven hours. Pdf selective mass scaling and critical timestep estimate for. Analytical estimate of stable timestep size for scaled elements is provided.
265 1458 1309 633 337 819 1037 1064 508 127 191 1541 552 1142 962 1408 989 1124 1571 411 1665 1384 977 450 119 1006 1260 1598 654 1574 406 658 1562 1490 451 787 731 1174 438 967 803 406 38