Technical support team at livermore software and technology corporation lstc. 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. Learning the ls dyna suite of preprocessors would probably not be a worthwhile investment of time. Ove arup and partners limited june 16 june 2014 page 64 ls dyna software 6 release notes version 971 r7. Preprocessor software for calibration of lsdyna material. This program includes kfiles into the waiting list.
It concludes with the recent developments of sms and an overview of supported featues as well as with a short overview of some examples. So to summarize, ls dyna is one of the big codes alot of people use. Here only highfrequency modes are affected by the extra bulk and these only have a minor. By focusing an artificial mass scaling on this domain, the critical time step may be increased substantially without significantly affecting the low. Numerical solution explicit among many explicit methods, the centraldifference technique is the most popular and is used in lsdyna time. 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. Using selective mass scaling only the high frequencies are affected, whereas the low frequencies rigid body modes are not influenced. Selective mass scaling for explicit finite element analyses. Selective mass scaling technique is proposed not affecting low order modes. Thereby, a lot of artificial mass can be added to the system without adulterate the global solution. Nonlinear numerical simulation for reinforced concrete.
Linear and highly non linear problems can be effectively solved. 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. Excessively small stable timestep due to element small thickness. To reduce the cpu cost and improve the performance, mass scaling is often used to increase the time step size in each cycle. Explicit method for dynamic and static nonlinear finite. The original kfile designed for calculation in lsdyna is uploaded to kklient. Lsdyna periodically looks for this file and if found, the sense switch contained therein is invoked and the d3kil file is deleted. 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. 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. The tran option is only available when the copy element option is activated. Technical support team at livermore software technology orporation lst. 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. Automotive crashworthiness trends and challenges march.
Selective mass scaling for distorted solidshell elements in. A springback compensation study on chrysler 300c stamping. Optionally the scaling can be performed on multiple copies of the selected elements. Fix bug in selective mass scaling when beam release conditions are used in mpp. Automotive crashworthiness trends and challenges march 28 ls. Specialized features developed specifically for the automotive, aerospace, government, manufacturing industries. Pdf selective mass scaling and critical timestep estimate for. Ansys ls dyna is useful for the analysis of problems involving contact, large deformation, nonlinear materials, transient response, andor problems requiring explicit solutions. Lsdyna iinf lsdyna rrtf default names for the output file, binary plot files, and the dump file are d3hsp, d3plot, d3thdt, and d3dump, respectively. The smoothed particle hydrodynamics sph method can avoid this class of problems and has been successfully applied to simulate fracture of solids.
Ove arup and partners limited june 16 june 2014 page 64 lsdyna software 6 release notes version 971 r7. Selective mass scaling and critical timestep estimate for. An alternative to conventional mass scaling is the selective mass scaling sms introduced by ls dyna. If the pulse duration extended to 90 ms, it could take ansys lsdyna 15 to 20 hours to solve the simulation. Preprocessor software for calibration of lsdyna material models. 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. Numerical solution explicit among many explicit methods, the centraldifference technique is the most popular and is used in ls dyna time. 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. 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. Bug was a matter of local vs global variables mismatch.
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. These studies cover the use of selective mass scaling, increased element size and reduced number of integration points. 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. When it receives the command to send the file for calculation, kklient sends the kfile to the server. Highlights explicit dynamics analysis with solidshell is of interest in many applications. The simplest method is to use a large mass density for the blank. Recently, selective mass scaling method was implemented in lsdyna. For an analysis using interface segments the execution line in the first analysis is given by. Lsdyna calculates your solution by running over all the nodes in the model at each time step. Study of correspondence between press hardened components and.
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. 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. Box 712 livermore, california 945510712 support addresses livermore software technology corporation 7374 las positas road livermore, california 94551 tel. The work material used in this study is aluminum 6061t6 alloy. A selective mass scaling technique, based on a linear transformation of the. Analytical estimate of stable timestep size for scaled elements is provided. The simulation result from the optimized forming simulations showed a much improved correlation with the press hardened product. Several methods can be used with lsdyna to accomplish this. Have the same time step size for all elements by adjusting density.
On the improvement of computational efficiency of smoothed. Mass scaling for minimum time step size adjusting density to user defined time step size. 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. Recent developments in lsdyna ii john hallquist livermore software technology corporation, livermore, usa. Feb 20, 2016 this is my second try to simulate incremental sheet forming in ls dyna. 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. Ls dyna periodically looks for this file and if found, the sense switch contained therein is invoked and the d3kil file is deleted. Ansys lsdyna is useful for the analysis of problems involving contact, large deformation, nonlinear materials, transient response, andor problems requiring explicit solutions. It cuts some corners, so there are more accurate ways to do it, but this method returns good results. This course covers the use of ansys ls dyna inside workbench mechanical. The mass of small or stiff elements is increased to prevent a very small timestep. When ls dyna terminates, all scratch files are destroyed. Lsdyna website lsdyna is a generalpurpose finite element program capable of simulating complex real. These models are often quite complex and difficult to calibrate.
Single point incremental forming simulation in lsdyna youtube. Ls dyna if problems in crashworthiness were to be properly solved. Effects of mass scaling hi all, im currently working using abaqus explicit to simulate a needle moving at 0. Selective mass scaling in ls dyna to reduce nonphysical inertia effects. I used the mass scaling option to help increase the computational efficiency because without mass scaling, my simulation is taking days to run. 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. 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. 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. One can employ mass scaling in a selective manner by artificially increasing material density of the parts you want to massscale. As mention in chapter one it has been shown that the thread has a significant effect on the bolt strength 2. Study of correspondence between press hardened components. In developers forum, dynamore, stuttgart, germany, 2011, 2011. 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.
If both parameters are included, the mass is first scaled by the value assigned to the factor parameter and then possibly scaled again, depending on the values assigned to the dt and type parameters. Ls dyna calculates your solution by running over all the nodes in the model at each time step. Ls dyna website ls dyna is a generalpurpose finite element program capable of simulating complex real. Ansys lsdyna could solve a model in five to seven hours. The considered mass scaling preserves the element translational inertia, while. Im going to show one way of doing using software everyone has access to spreadsheet. This course covers the use of ansys lsdyna inside workbench mechanical. Iterative solution technique in selective mass scaling. Applications of variationally consistent selective mass. Explicit methods are very fast as there is no matrix inversion and the mass matrix is lumped or diagonal. Lsdyna if problems in crashworthiness were to be properly solved.
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. It is found that the user can use much large time step without affecting the springback prediction. 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. The tool material is tool steel, which is modeled as a rigid body. The scaling direction and factor can be specified using various methods for maximum flexibility to suit different user needs. Finite element simulation of orthogonal metal cutting using. However, small step size prevents this method from being useful for routine analysis work. When lsdyna terminates, all scratch files are destroyed. Ls dyna software package is with unlimited elements and capabilities. However, the associated computational cost is increased.
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