ansys仿真詭異錯(cuò)誤信息錦集——原因和解決方案

2021-12-21 by:CAE仿真在線來(lái)源:互聯(lián)網(wǎng)

如下是仿真在線的學(xué)員在Ansys workbench培訓(xùn)中碰到的一些比較難理解的問(wèn)題,為了方便起見(jiàn),本文講這些問(wèn)題集合起來(lái)。

1、分析類型為rigid dynamic剛體動(dòng)力學(xué)的【 Error creating joint condition】問(wèn)題:

Remote Displacement 3 Component 1 ( Load Step 2 ) Error creating joint condition. Check the syntax of the expression or the smoothness of the tabular data.

從字面意思看“遠(yuǎn)程位移3部件1(加載步驟2)錯(cuò)誤創(chuàng)建關(guān)節(jié)條件。檢查表達(dá)式的語(yǔ)法或表格數(shù)據(jù)的平滑度?！边@個(gè)英文基本無(wú)法理解是什么具體原因,太過(guò)隱晦了!

實(shí)際上,一般是你調(diào)整remote displacement的軌跡之后發(fā)生這種錯(cuò)誤。這個(gè)說(shuō)明什么問(wèn)題呢?說(shuō)明按照你的軌跡,運(yùn)動(dòng)沖突了,解決辦法就是調(diào)整到正常。

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2、分析類型為modal的【zero mass】問(wèn)題:

*** WARNING *** CP = 158.185 TIME= 11:49:40
The PCG Lanczos eigensolver has detected that element 977809 has zero
mass. Please check the density material property (or alternative mass
definition if appropriate) for this element. You should check the
solution carefully and if necessary you may want to either use a
Lev_Diff value equal to 5 on the PCGOPT command or switch to the Block
Lanczos eigensolver (MODOPT,LANB).

這個(gè)情況一般是因?yàn)槟B(tài)迭代求解器對(duì)模型不適應(yīng),可以選擇直接求解器解決。但是直接求解要求數(shù)倍的內(nèi)存空間,可能30萬(wàn)網(wǎng)格100萬(wàn)單元,就需要50G的內(nèi)存。

3、分析類型為static structure的【highly distorted】問(wèn)題:

*** ERROR *** CP = 3323.398 TIME= 10:10:20
Element 16671 (type = 7, SOLID187) (and maybe other elements) has
become highly distorted. Excessive distortion of elements is usually
a symptom indicating the need for corrective action elsewhere. Try
ramping the load up instead of step applying the load (KBC,1). You
may need to improve your mesh to obtain elements with better aspect
ratios. Also consider the behavior of materials, contact pairs,
and/or constraint equations. Please rule out other root causes of
this failure before attempting rezoning or nonlinear adaptive
solutions. If this message appears in the first iteration of first
substep, be sure to run shape checking of elements.
這個(gè)問(wèn)題是ansys軟件的通病,一旦變形過(guò)大或局部變形過(guò)大,ansys就受不了。這種情況你使用transient類型,仍然不會(huì)解決問(wèn)題。ansys的transient與static的求解器底層其實(shí)都是一樣的,對(duì)非線性問(wèn)題基本一樣。

那怎么解決呢?一個(gè)是從材料入手,一個(gè)是從網(wǎng)格入手,再者就是調(diào)整接觸,三個(gè)基本方向。比如可以使用Mooney材料。其次保持網(wǎng)格的均勻,使網(wǎng)格質(zhì)量更高。這兩個(gè)方向都需要依靠經(jīng)驗(yàn)非常豐富的cae工程師來(lái)調(diào)整。

最后如還不行,可以使用ls-dyna求解器,這個(gè)非線性變形很好,不足的是對(duì)接觸突破型的案例,其求解時(shí)間特別長(zhǎng),服務(wù)器動(dòng)輒需要1000小時(shí)以上,非逼不得已不要使用。

未完待續(xù)——

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