1始終注意保持使用一致的單位制； 2求解前運(yùn)行allsel命令 求解前運(yùn)行allsel命令。要不然，某些已經(jīng)劃分網(wǎng)格的實(shí)體而沒(méi)有被選擇，那么加在實(shí)體模型上加的荷載可能會(huì)沒(méi)有傳到nodes or elements上去； 3網(wǎng)格劃分問(wèn)題 牢記《建模與分網(wǎng)指南》上有關(guān)建模的忠告。網(wǎng)格劃分影響模型是否可用，網(wǎng)格劃分影響計(jì)算結(jié)果的可接受程度； 自適應(yīng)網(wǎng)格劃分(ADAPT)前必須查自適應(yīng)網(wǎng)格劃分可用單元，在ansys中能夠自適應(yīng)網(wǎng)格劃分的單元是有限的。 網(wǎng)格劃分完成后，必須檢查網(wǎng)格質(zhì)量！權(quán)衡計(jì)算時(shí)間和計(jì)算精度的可接受程度，必要時(shí)應(yīng)該refine網(wǎng)格 4 實(shí)體建模布爾運(yùn)算 應(yīng)用實(shí)體建模以及布爾運(yùn)算（加、減、貼、交）的優(yōu)勢(shì)解決建立復(fù)雜模型時(shí)的困難；但是，沒(méi)有把握時(shí)布爾運(yùn)算將難以保證成功！ 5 計(jì)算結(jié)果的可信度 一般來(lái)說(shuō)，復(fù)雜有限元計(jì)算必須通過(guò)多人，多次，多種通用有限元軟件計(jì)算核對(duì)，互相檢驗(yàn)，相互一致時(shí)才有比較可靠的計(jì)算結(jié)果。協(xié)同工作時(shí)必須對(duì)自己輸入數(shù)據(jù)高度負(fù)責(zé)，并且小組成員之間保持良好的溝通；有限元分析不是搞什么“英雄主義”，而需要多方面的質(zhì)量保證措施。 6了解最終所需要的成果 建立模型之前，應(yīng)該充分了解最終要求提交什么樣式的成果，這樣能形成良好的網(wǎng)格，早期良好的建模規(guī)劃對(duì)于后期成果整理有很大的幫助； 7 撰寫(xiě)分析文檔 文檔與分析過(guò)程力求保持同步，有利于小組成員之間的溝通和模型的檢驗(yàn)和查證； 8 熟悉命令 對(duì)沒(méi)有把握的命令應(yīng)該先用簡(jiǎn)單模型熟悉之，千萬(wàn)不能抱有“撞大運(yùn)”的想法； 9 多種單元共節(jié)點(diǎn) 不同單元使用共同節(jié)點(diǎn)時(shí)注意不同單元節(jié)點(diǎn)自由度匹配問(wèn)題導(dǎo)致計(jì)算結(jié)果的正確與否(《建模與分網(wǎng)指南》P 8 ) 三維梁?jiǎn)卧蜌卧墓?jié)點(diǎn)自由度數(shù)一致，但是應(yīng)該注意到三維梁?jiǎn)卧霓D(zhuǎn)動(dòng)自由度和 殼單元的轉(zhuǎn)動(dòng)自由度的含義不一樣。殼的ROTZ不是真實(shí)的自由度,它與平面內(nèi)旋轉(zhuǎn)剛度相聯(lián)系，在局部坐標(biāo)中殼的單元?jiǎng)偠染仃嘡OTZ對(duì)應(yīng)的項(xiàng)為零，對(duì)此不能將梁與殼單元僅僅有一個(gè)節(jié)點(diǎn)相連，例外的是當(dāng)shell43 or shell63(兩者都有keyopt(3)=2)的Allman旋轉(zhuǎn)剛度被激活時(shí)。 Solid65 單元和 shell63 單元相連，相應(yīng)平動(dòng)自由度的節(jié)點(diǎn)力會(huì)傳到實(shí)體塊單元上，但是shell63單元的轉(zhuǎn)動(dòng)自由度的節(jié)點(diǎn)唯一則不會(huì)傳到相連的 solid65單元上。 10 查找文獻(xiàn)資料確定混凝土的材料參數(shù)輸入（ Tb, concr, , , ） 11 預(yù)測(cè)內(nèi)存和磁盤(pán)空間 大型復(fù)雜模型（例如10萬(wàn)個(gè)節(jié)點(diǎn)，非線性問(wèn)題，多工況問(wèn)題，1000步以上的瞬態(tài)分析等等）求解之前預(yù)測(cè)求解所需要的求解時(shí)間、內(nèi)存和磁盤(pán)空間，使分析盡在掌握之中； 12 收斂問(wèn)題 影響收斂（不收斂，或者收斂緩慢）的原因很多，《非線性分析指南》一書(shū)上有很多關(guān)于避免發(fā)生收斂問(wèn)題的建議； 對(duì)于以下參數(shù)，可以試一試這些參數(shù)對(duì)收斂速度以及結(jié)果精度的影響 neqit = 6～25? 加載荷載步大小 = ？ 接觸單元的實(shí)常數(shù) = ？ 例如接觸剛度的大小取值必須權(quán)衡計(jì)算結(jié)果精度（穿透大�。┖褪諗繂�(wèn)題（ 收斂時(shí)間 ）兩者的可接受程度，需要經(jīng)驗(yàn)值或者試算； 13 啟動(dòng)重分析 14 兩個(gè)相貫的薄壁圓筒建模，殼單元沒(méi)有公共節(jié)點(diǎn) Element Connectivity Error, 8-Node Curved Shell Elements In this image, the red stiffener was intended to be welded to the purple pipe. Note that the elements of the red stiffener do not match up with those on the pipe. There is no connection, and the meshing was done independently. This is due to a geometric modeling error by the user (me). There are superimposed curved lines where the interface is located. There should have been a shared line for the connection to have worked. I found this only because of careful examination of the model -- I had already run a stress analysis. What to do about these error concerns? Read and think. Share and listen to ideas and concerns with others. Review your own work, and the work of your co-workers. (Recently an experienced co-worker who does not even do FEA work asked me if I had eliminated the added mass of water in pipes when evaluating shipping loads on a product. I hadn't. Eliminating the added mass got rid of a high-stress problem. These errors are very easy to make.) Be friendly. Communicate with other departments. Have a check list and design reviews. Never use FEA blindly, or believe the results of an analysis without some critical review. Accept a critical review without taking it personally. Develop a good understanding of the intent of the design codes that regulate your work. Consult an expert when it is appropriate. Pay attention to the ethics and standards of your professional association. Choose your employer wisely. (Some of these things you were supposed to have learned in Kindergarten, but life isn't always that simple.) 解決方法：通過(guò)volumn建模形成相貫線，該方法建模使面相交處共線，xmesh后有公共nodes 15 選擇集的應(yīng)用 為了利用選擇集cm / xsel的強(qiáng)大功能，可以合理定義線，面的實(shí)常數(shù)real屬性，為了選擇操作方便而賦予更多的單元實(shí)常數(shù)號(hào)，材料號(hào) 18 UPGEOM 和 MPCHG 的應(yīng)用 ! UPGEOM更新幾何形狀 !a.rst為計(jì)算結(jié)果文件名，最后一個(gè)為目錄 !這兩個(gè)參數(shù)應(yīng)根據(jù)你的計(jì)算情況定 UPGEOM,1,LAST,LAST,NEW,rst,F:\729\ ! MPCHG彈性模量恢復(fù)為真值 esel,s,mat,,3 mpchg,4,all • You might be tempted to try to deactivate or reactivate elements by changing their material properties [ MPCHG ] ( Main Menu>Preprocessor>Material Props>Change Mat Num ). However, you must proceed cautiously if you attempt such a procedure. The safeguards and restrictions that affect "killed" elements will not apply to elements that have their material properties changed in SOLUTION. (Element forces will not be automatically zeroed out;nor will strains, mass, specific heat, etc.) Many problems could result from careless use of MPCHG . For instance, if you reduce an element's stiffness to almost zero, but retain its mass, it could result in a singularity if subjected to acceleration or inertial effects. One application of MPCHG would be in modeling construction sequences in which the strain history of a "born" element is maintained. Using MPCHG in such cases will enable you to capture the initial strain experienced by elements as they are fitted into the displaced nodal configuration 19 Ansys 中的坐標(biāo)系統(tǒng)，使用各種坐標(biāo)系時(shí)應(yīng)該明白在各處理器中輸入輸出會(huì)受到那些坐標(biāo)系的影響 整體和局部坐標(biāo)系CSYS---用于定位幾何形狀參數(shù)的空間位置 顯示坐標(biāo)系DSYS---用于幾何形狀參數(shù)的列表和顯示 節(jié)點(diǎn)坐標(biāo)系---定義節(jié)點(diǎn)自由度方向和節(jié)點(diǎn)結(jié)果數(shù)據(jù)的方法。輸入數(shù)據(jù)時(shí)受到節(jié)點(diǎn)坐標(biāo)系影響的有：約束自由度（方程），力，主(從)自由度；在/POST26中在節(jié)點(diǎn)坐標(biāo)系下輸出文件和顯示的數(shù)據(jù)結(jié)果有：自由度解，節(jié)點(diǎn)荷載，反作用荷載； Forces are defined in the nodal coordinate system. The positive directions of structural forces and moments are along and about the positive nodal axis directions. The node and the degree of freedom label corresponding to the force must be selected [ NSEL , DOFSEL ]. 單元坐標(biāo)系---每個(gè)單元都有自己的坐標(biāo)系，單元坐標(biāo)系用于確定材料特性主軸，加面壓力和和單元結(jié)果數(shù)據(jù)（如應(yīng)力和應(yīng)變）的輸出方向；ANSYS規(guī)定了單元坐標(biāo)系的缺省方向；許多單元都有keyopts可用于修改單元坐標(biāo)系的缺省方向；對(duì)于面和體單元而言，可以用ESYS命令將單元坐標(biāo)系的方向調(diào)整到已定義的局部坐標(biāo)系； 結(jié)果坐標(biāo)系RSYS---用來(lái)列表、顯示或者在/POST1中將節(jié)點(diǎn)和單元結(jié)果轉(zhuǎn)換到特定的坐標(biāo)系中。在/POST1中結(jié)果數(shù)據(jù)換算到結(jié)果坐標(biāo)系(RSYS)下記錄。定義路徑時(shí)，可以用系列命令*GET, ACTSYS, ACTIVE,CSYS $ RSYS, ACTSYS使結(jié)果坐標(biāo)系與激活的坐標(biāo)系（用于定義路徑）相匹配 求解坐標(biāo)系---大多數(shù)模型疊加技術(shù)（PSD,CQC,SRSS）是在求解坐標(biāo)系中進(jìn)行的，使用RSYS,SOLU命令來(lái)避免在結(jié)果坐標(biāo)系中發(fā)生變換，使結(jié)果數(shù)據(jù)保持在求解坐標(biāo)系中。 20 Ansys 5.7通過(guò)函數(shù)定義邊界條件 利用函數(shù)可以很簡(jiǎn)單方便地定義復(fù)雜邊界條件和載荷（將邊界條件當(dāng)作函數(shù)處理（即方程））。該特性是5.6 中介紹的表格化邊界條件的擴(kuò)展功能。用戶可以創(chuàng)建大量函數(shù)并存儲(chǔ)起來(lái)，以便于將來(lái)使用。 5.6的表格化邊界條件(Tabular boundary conditions) Tabular boundary conditions ( VALUE = % tabname %) are available only for structural (UX, UY, UZ, ROTX, ROTY, ROTZ) and temperature degree of freedom (TEMP) labels and are valid only in static ( ANTYPE ,STATIC) and full transient ( ANTYPE ,TRANS) analyses. 滯回曲線——位移加載 *DIM,dis,TABLE,9,1,,TIME, , DIS(1,0) = 0,1,2,3,4,5,6,7,8 DIS(1,1) = 0,3,0,-3,0,4,0,-4,0 D,22, , %DIS% , , , ,UZ, , , , , ansys 5.6 help files------- 2.6.3. Applying Loads Using TABLE Type Array Parameters 優(yōu)點(diǎn)： 將復(fù)雜載荷和邊界條件定義成基本變量和因變量的連續(xù)或非連續(xù)方程。 提供創(chuàng)建和運(yùn)用函數(shù)的極易操作的GUI 界面。 應(yīng)用 ： 該特性適用于所有ANSYS家族產(chǎn)品。 該特性適用于ANSYS程序的所有過(guò)程，支持TIME, TEMP, X, Y, Z, VELOCITY和PRESSURE等基本變量。 21 automatic time stepping For nonlinear problems, automatic time stepping determines the amount of load increment between substeps
RAR
