PARAM设置问题

jiangxiwu

HM+NASTRAN做静力分析，PARAM经常如下设置：
PARAM,AUTOSPC,YES     
PARAM,BAILOUT,-1      
PARAM,COUPMASS,2            
PARAM,K6ROT,100.0   
PARAM,POST,-2  

但在国外某汽车公司的网站上有如下notes:
PARAM,BAILOUT,-1
This card totally defeats all of Nastran built in checks and will prevents the job from reporting FATAL errors.
It will appear that your job has run correctly, but your answers will be erroneous.
You should never use this card unless specifically requested to by someone from MSC, or one of your local Technical Specialists.




PARAM,K6ROT,xxxEyyy
This card was originally invented to debug Nastran when the nonlinear analysis capabilities were being installed.
The original intent was to slow down the model and allow the nonlinear solution to converge.
In reality, there was an error in the original element formulation some 20 years earlier.
Eventually the element formulation error was found, but the card continues to be used.
Currently, users routinely place this card in their deck with no idea of where it came from or what it does.
They only know that if you have a model that will not run, this card will sometimes cause the model to produce answers. Please note, it will not necessarily cause the model to produce good answers, but it will sometimes produce answers.
The correct thing to do is to fix the model, and not to use cards like this to force printout.




请问大家一般怎么设置的？

liminglaile

PARAM,BAILOUT,-1  

这一条的使用要非常小心。盲目的使用这一条参数，计算出来的结果都是假的。

jiangxiwu

原帖由 liminglaile 于 2008-6-24 13:31 发表
PARAM,BAILOUT,-1  

这一条的使用要非常小心。盲目的使用这一条参数，计算出来的结果都是假的。

在什么情况下能用什么情况下不能用?

diane_wenjuan

PARAM,AUTOSPC,YES     
PARAM,BAILOUT,-1      
PARAM,GRDPNT,0
PARAM,POST,-1  
PARAM,PRGPST,NO
做静态分析时我一般是这样设置，BALOUT设成-1不知道有什么问题？

liminglaile

原帖由 jiangxiwu 于 2008-6-24 23:04 发表

在什么情况下能用什么情况下不能用?

PARAM,BAILOUT,-1
PARAM,K6ROT,100.0

注意：这两条的作用有些相同。都是“主动”的控制FEA模型中的某些参数和数据。K6ROT=100是用来人为约束第六个自由度的，100是一个系数，也就是在能量计算的泛函方程中人为的乘以100这个系数，刻意提高结构的刚度。Nastran的算法在计算的时候如果鉴定你的结构太“软”，那么便会调用这个参数刻意的进行修改。不到万不得已，不要使用这些参数。楼上有位朋友diane_wenjuan 说他每次静力分析都使用这几个参数，那是严重无知、严重错误的！！！这样盲目无知的FEA分析员留着还有啥用？！只会铸成大错，解雇了算了！！！