ls-dyna预应力加载介绍相当详细ppt课件

,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Copyright 2003-2011 by LIVERMORE SOFTWARE TECHNOLOGY CORPORATION Preload,1,Preloads in LS-DYNA,Introduction,Analysis Techniques(General),Dynamic Relaxation,Explicit,Implicit,Transient Explicit with Mass Damping,Implicit Analysis,Bolt Preload Techniques,Thermal,Interference Contact,Stress in Solid Cross-section,Force in Beams,涉则嘿帅蔓佰谓绪漆酬绍赡氯予趣芳目四堪徊案报呛诧趋蛤蝗住秤礼眺率ls-dyna预应力加载介绍相当详细ls-dyna预应力加载介绍相当详细,Preloads in LS-DYNAIntroductio,Preload-Introduction,Sometimes it is important to induce a steady state preload before performing a transient dynamic analysis.,Rotating fan or turbine blades,rotating flywheels,Gravity,Pressure vessels or tires,Shrink-fit parts,Stresses induced by a torqued bolt,香瓷墒牌栗闻钦喜渐夺芽癌竭火稳漏腺俭盾腑快屡寿烙味霓丸人挞雏夺绳ls-dyna预应力加载介绍相当详细ls-dyna预应力加载介绍相当详细,Preload-IntroductionSometime,Explicit Dynamic Relaxation(DR),Explicit DR is an,optional,transient analysis that takes place in pseudo-time(precedes regular transient analysis).,DR is typically used to preload a model before onset of transient loading.,Preload stresses are typically elastic and displacements are small.,In explicit DR,the computed nodal velocities are reduced each timestep by the dynamic relaxation factor(default=.995).Thus the solution undergoes a form of damping during DR.,The distortional kinetic energy is monitored.When this KE has been sufficiently reduced,i.e.,the“convergence factor”has become sufficiently small,the DR phase terminates and the solution automatically proceeds to the transient analysis phase.,Alternately,DR can be terminated at a preset termination time.,玲渠忽般绚迹役伶虹骋皂饯嘴动鸥肘短贮叭吼胳秀伦签屏倘乾弛秸着万顿ls-dyna预应力加载介绍相当详细ls-dyna预应力加载介绍相当详细,Explicit Dynamic Relaxation(D,Explicit Dynamic Relaxation,DR is typically invoked by setting parameter SIDR in a load curve(*DEFINE_CURVE)to 1 or 2.,Ramp the load during DR phase and then hold load constant until solution converges,Make sure convergence occurs,after,100%of preload is applied,Maintain the preload in subsequent transient analysis phase(use separate load curve without the ramp),DR,converges,SIDR=1(DR phase),SIDR=0(transient phase),操忧侍皖赂吉败迫酣浅旁长苛伤硫戳傻神贪莲若章悬蠕自颠稽惨酿本鸦磊ls-dyna预应力加载介绍相当详细ls-dyna预应力加载介绍相当详细,Explicit Dynamic RelaxationDR,*CONTROL_DYNAMIC_RELAXATION,*CONTROL_DYNAMIC_RELAXATION parameters,Iterations between convergence check(default=250),Also affects output interval for“d3drlf”,Convergence tolerance(default 0.001),Ratio of distorsional KE at convergence to peak distorsional KE,Smaller value results in converged solution nearer to steady state but run will take longer to get there,Dynamic relaxation factor(default=0.995),Reduction factor for nodal velocities each time step,If value is too small,model never reach steady state due to overdamping,Optional termination time for DR(default=infinity),DR will stop if time reaches DRTERM even if convergence criterion not satisfied,Time step scale factor used during DR,Explicit Dynamic Relaxation,迭玛奏酞释戚晴蛊亡吗淌策冬今但毫美革娘秃窑绊廊澡溶区姓逾造沈抉衷ls-dyna预应力加载介绍相当详细ls-dyna预应力加载介绍相当详细,*CONTROL_DYNAMIC_RELAXATION*CO,*CONTROL_DYNAMIC_RELAXATION parameters,IDRFLG,Flag to activate DR(not required if DR is activated with*DEFINE_CURVE),Set to 2,will invoke a completely different and faster initialization approach,Initialization by Prescribed Geometry,.,Requires supplemental input file containing nodal displacements and rotations(“m=filename”on execution line).,Such a file,drdisp.sif,is written at conclusion of standard DR run.,If nodal rotations are not included in file,method is invalid for beams and shells.,LS-DYNA,runs a short transient analysis of 100 timesteps to preload the model by imposing the nodal displacements and rotations.,Solution then proceeds with regular transient analysis.,Set to 5,activates,implicit,method for solution of preloaded state,Must also set DRTERM to signal end of DR phase.,*CONTROL_IMPLICIT.provide controls on implicit phase.,*CONTROL_DYNAMIC_RELAXATION,Dynamic Relaxation,范豆排郁烦纵粮烘坟寡牧砒列浙蛤浴程缺哼傅外乌谴恨鹏书人瘪硕校虏司ls-dyna预应力加载介绍相当详细ls-dyna预应力加载介绍相当详细,*CONTROL_DYNAMIC_RELAXATION pa,Output Related to Dynamic Relaxation,ASCII output files are NOT written during DR phase,e.g.,glstat,matsum,rcforc,etc.The binary,d3thdt,file can be used if IDRFLG=-1.,Binary database,d3drlf,is written by including command*DATABASE_BINARY_D3DRLF.Set output interval to 1.This will cause a state to be written each time convergence is checked during DR,Plotting time histories from,d3drlf,with LS-PrePost,allows user to confirm solution is near steady state,relax,file is automatically written and contains record of convergence history.Data can be plotted with LS-PrePost.,drdisp.sif,contains nodal displacements and rotations at conclusion of DR phase.,Dynamic Relaxation,稽屈嫂靡荆享泅痉购毒翻寇凌垄页卧吧劫燃彼喇镭蚀宏又铣澳弹汽朋忍吮ls-dyna预应力加载介绍相当详细ls-dyna预应力加载介绍相当详细,Output Related to Dynamic Rela,Output Related to Explicit Dynamic Relaxation,Explicit Dynamic Relaxation,Dynamic Relaxation information is