ABAQUS常見(jiàn)警告解決方案

2016-10-05 by:CAE仿真在線來(lái)源:互聯(lián)網(wǎng)

對(duì)于有限元計(jì)算經(jīng)常會(huì)遇到警告信息,通常都要通過(guò)dat文件、msg文件判斷這些警告信息是否需要關(guān)注,那么如何針對(duì)不同的警告信息,做出正確的判斷呢。這里列舉一些常見(jiàn)的警告信息,供各位CAE小蝦們學(xué)習(xí)交流。

1. 負(fù)特征值問(wèn)題

THESYSTEM MATRIX HAS 8 NEGATIVE EIGENVALUES.

負(fù)特征值是非線性分析的必然產(chǎn)物。所以不必大驚小怪,甚至久而久之,對(duì)于你熟悉的問(wèn)題,你都會(huì)視而不見(jiàn)了。若出了問(wèn)題,可先檢查下有沒(méi)有伴隨的numerical sigularity(數(shù)值奇異)和 Zero pivot(零主元)產(chǎn)生。如果沒(méi)有,可以參考這幾個(gè)方面:1).剛體位移;2).單元異常,過(guò)度變形、過(guò)度扭曲等;3).應(yīng)力應(yīng)變關(guān)系有負(fù)斜率;4)如果有流體的話,在容器發(fā)生形變的話,也可能出現(xiàn)negative eigenvalue的情況,不過(guò)不會(huì)出現(xiàn)警告,這是被允許的;5)失穩(wěn)發(fā)生

2. 單元變形速率過(guò)大

Theratio of deformation speed to wave speed exceeds 1.0000

這個(gè)警告是指單元形變速度V(單元最大形變率/特征尺寸)和膨脹波速C(通過(guò)材料本構(gòu)關(guān)系求得)的比例超過(guò)1。解決這個(gè)問(wèn)題的方案有以下幾種:1)檢查單位是否封閉(參數(shù)設(shè)置有數(shù)量級(jí)的錯(cuò)誤),此錯(cuò)誤新手常犯;2) 檢查網(wǎng)格質(zhì)量;(3) 檢查加載速度,如果條件允許的話就降低速度,該方法也很有效,但在很多情況下無(wú)法降低速度;4)調(diào)整STEP中的TIME SCALING FACTOR;調(diào)整STEP中的MASS SCALING FACTOR;5) 加*SECTION CONTROLS,NAME=SC,DISTORTION CONTROL,LENGTH RATION=0.1 或者YES也可以,加在MATERIAL 前面;或加* DIAGNOSTICS,DEFORMATION SPEEDCHECK=OFF;或者加*DIAGNOSTICS, CUTOFF RATIO=RATIO(具體數(shù)值),在其他方法修改后還有問(wèn)題的的情況下使用增加關(guān)鍵字的方法

3. zero force/ZERO MOMENT問(wèn)題

THERE IS ZERO MOMENTEVERYWHERE IN THE MODEL BASED ON THE DEFAULT CRITERION. PLEASE CHECK THE VALUEOF THE AVERAGE MOMENT DURING THE CURRENT ITERATION TO VERIFY THAT THE MOMENT ISSMALL ENOUGH TO BE TREATED AS ZERO. IF NOT, PLEASE USE THE SOLUTION CONTROLS TORESET THE CRITERION FOR ZERO MOMENT.

這些警告是告訴你模型中沒(méi)有彎矩,沒(méi)問(wèn)題的,可以繼續(xù)計(jì)算。如果提示中出現(xiàn)特征值奇異的時(shí)候才是計(jì)算有可能出現(xiàn)不收斂的問(wèn)題。

4. 自由度沒(méi)激活

Degreeof freedom 4 is not active in this model and can not be restrained

有限元軟件計(jì)算對(duì)于實(shí)體步考慮轉(zhuǎn)動(dòng)自由度,所以你在邊界條件中限制了456的自由度后,軟件會(huì)忽略的啊.

5. 位移加載問(wèn)題

The option *boundary,type=displacementhas been used; check status file between steps for warnings on any jumps prescribedacross the steps in displacement values of translational dof. For rotationaldof make sure that there are no such jumps.All jumps in displacements acrosssteps are ignored

你采用了位移邊界條件,但在平動(dòng)自由度上,可能在不同的分析步驟里面有突變(你可以從sta文件里面查看),并且應(yīng)保證轉(zhuǎn)動(dòng)自由度無(wú)突變。通知性質(zhì)的warning,一般是因?yàn)槟悴捎梦灰萍虞d方式,都出這個(gè)。

6. 塑性應(yīng)變過(guò)大

The strain increment hasexceeded fifty times the strain to cause first yield at 377 points

檢查下約束夠不夠,約束夠了就不用管了,這只是通知你,你的模型塑性應(yīng)變很大,一般沒(méi)多大問(wèn)題。

7. 過(guò)約束

123 nodes are used morethan once as a slave node in *TIE keyword.One of the *TIE constraints at eachof these nodes have been identified in node set WarNodeOverconTieSlave

定義接觸的時(shí)候,公共節(jié)點(diǎn)重復(fù)定義了好幾次,這樣可能會(huì)出現(xiàn)過(guò)約束問(wèn)題(只是可能影響)

8. 未連接區(qū)域

Thereare 2 unconnected regions in the model.

可能是接觸面由空隙,最好在接觸屬性中定義一個(gè)容差范圍。一般各個(gè)parts之間定義接觸,aba都會(huì)這樣通知用戶(hù)的,只要接觸設(shè)置對(duì)了,一般沒(méi)事。

9. 邊界條件定義問(wèn)題

Boundaryconditions are specified on inactive dof of 124 nodes. The nodes have beenidentified in node set WarnNodeBCIactiveDof

邊界條件定義的有問(wèn)題:在124個(gè)節(jié)點(diǎn)的非自由度上有邊界加載

10. 塑性應(yīng)變過(guò)大

Theplasticity/creep/connector friction algorithm did not converg

一般是塑性應(yīng)變太大,單元扭曲導(dǎo)致的?？梢韵雀臑閺椥阅Ｐ涂纯词欠袷諗?

11. 增量調(diào)整過(guò)大

The ratio of the maximumincremental adjustment to the average characteristic length is 1.82846e-02 atnode 10868 instance jiti1 on the surface pair (assembly_jq22,assembly_q22).

可以通過(guò)調(diào)大預(yù)設(shè)值消除該提示and檢查網(wǎng)格質(zhì)量。

12. 單元質(zhì)量問(wèn)題

ELEMENT42 INSTANCE SOIL3-1 IS DISTORTING SO MUCH THAT IT TURNS

應(yīng)改進(jìn)單元質(zhì)量

13. 節(jié)點(diǎn)不對(duì)

650 nodes are eithermissing intersection with their respective master surface or outside the adjustzone

改改tie里的tolarance試試

14. 非獨(dú)立部件問(wèn)題

Dependentpart instances cannot be edited or assigned mesh attributes

模型樹(shù)--assembly-單擊part 右鍵--make independent。也可以到模型樹(shù)part步展開(kāi)點(diǎn)mesh。

15. 長(zhǎng)寬比太大

Theaspet ratio for nnn elements exceeds 100 to 1.

單元?jiǎng)澐志W(wǎng)格長(zhǎng)寬比不合適。如果這些單元在不重要的區(qū)域(對(duì)結(jié)果肯定有些影響,影響大小取決于這三個(gè)單元的位置,在模型中的作用等),而且能計(jì)算,那就沒(méi)問(wèn)題了

16. 單元扭曲

123elements are distorted

存在單元扭曲,如果這些單元在不重要的區(qū)域(對(duì)結(jié)果肯定有些影響,影響大小取決于這三個(gè)單元的位置,在模型中的作用等),而且能計(jì)算,那就沒(méi)問(wèn)題了

17. 約束沒(méi)有的自由度

***WARNING: DEGREE OFFREEDOM 1 IS NOT ACTIVE ON NODE 6 - THIS BOUNDARY CONDITION IS IGNORED

約束了單元沒(méi)有得自由度對(duì)求解沒(méi)有影響,可以查看下

18. 熱流問(wèn)題

熱分析時(shí)出現(xiàn)了這樣的警告

There is zero HEAT FLUXeverywhere in the model based on the default criterion. please check the valueof the average HEAT FLUX during thecurrent iteration to verify that the HEAT FLUX is small enough to be treated aszero. if not, please use the solution controls to reset the criterion for zeroHEAT FLUX.

檢查(1)是不是熱源定義的問(wèn)題,錯(cuò)誤信息是說(shuō)熱源量幾乎為零。

(2)定義熱源的子程序調(diào)用命令流應(yīng)該為*HEAT GENERATION,在材料模塊中定義,子程序?yàn)镠ETVAL。

19. 單元或面重復(fù)

The elements in theelement set WarnElemSurfaceIntersect-Step1 are involved surface intersections.Refer to the status and message file for further details

檢查一下你單元集合的定義以及面的定義,看是否出現(xiàn)了相交或重復(fù)定義的情況。

20. 輸出不正確

Integration and sectionpoint output variables will not be output for deformable elements that aredeclared as rigid using the *rigid body option

這個(gè)僅是通知性質(zhì)的(在interaction步設(shè)置為rigid body,不輸出應(yīng)力應(yīng)變),你在interaction步定義了剛體約束的話,都會(huì)出這個(gè)警告。

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