1、雙擊Interactions，出現接觸形式定義。分為通用接觸（General contact）、面面接觸（Surface-to-Surface contact）和自接觸（Self-contact）。1. 通用接觸 General contact通用接觸用于為多組件，并具有復雜拓撲關系的模型建模。General contact algorithm The contact domain spansmultiple bodies (both rigid anddeformable) Default domain is definedautomatically via anall-inclusive

2、element-basedsurface The method is geared towardmodels with multiplecomponents and complextopology。 Greater ease in definingcontact model2. Surface-to-Surface contact Contact pair algorithm Requires user-specified pairing of individual surfaces Often results in more efficient analyses since contact

3、surfaces arelimited in scope3. 自接觸（Self-contact）自接觸應用于當部件發生變形時，可能導致自己的某兩個或多個面發生接觸的情況。如彈簧的壓縮變形，橡膠條的壓縮。 容易使用“自動接觸” 節省生成模型的時間 通用接觸算法一般比雙面接觸算法快機械約束形式運動依從Kinematic contact method（只有接觸對形式可用,General contact不可用）默認的運動接觸公式達到的計算精度與接觸條件相一致。在多數情況下，它工作得很好。但是在某些情況下，如抖動接觸，使用罰函數接觸會更容易得到收斂的解。不能為剛體-剛體接觸建模。罰函數（通用接觸和接觸對

4、均可使用） Penalty contact method罰函數接觸算法中接觸約束的嚴格性低于運動學算法。罰函數算法可以處理更一般類型的接觸；比如，剛體之間的接觸。因為罰函數算法在模型中引入附加剛度，該附加剛度將影響穩定時間增量。Abaqus/Explicit自動計算由與接觸力相關的侵徹距離引入的“彈簧”剛度或“罰”剛度。但是必須考慮相關的影響：應該盡量減少對穩定時間增量的影響。在所有的分析中，允許的侵徹不可以太大。 對于接觸對算法：通過在*CONTACT CONTROLS選項指定SCALE PENALTY參數，用戶可以縮放默認的罰剛度。 對于通用接觸算法：可以使用*CONTACT CONTRO

5、LS ASSIGNMENT, TYPE=SCALE PENALTY 選項縮放罰剛度。綜上，多數情況下，運動依從算法和罰函數算法將得到幾乎一致的結果。然而，在某些情況下，一種方法可能比另一種方法更可取。如果需要知道kinematic algorithms和  penalty algorithms之間的區別，那就需要啃理論教材了(當然看abaqus 幫助文件也可以).  簡略的說：1） penalty algorithms（罰函數法）在被abaqus檢測到接觸距離以內的節點之間定義罰剛度，進而來迭代出接觸力。在每一個時間步先檢查各從節點是否穿透主面。如沒有穿

6、透則進入下一個時間步；如果穿透，則在該從節點與被穿透主面間定義罰剛度，引入一個較大的界面接觸力，其大小與穿透深度、主面的剛度成正比。2）kinematic algorithms 先在一定時間內檢查所有未與主面(master surface)接觸的從節點(slave node)，看是否在此時間內穿透了主面。如果存在穿透則縮小時間步，使那些穿透主面的從節點都不貫穿主面，而使其正好到達主面。在計算下一時間步之前，對所有已經與主面接觸的從節點都施加約束條件，以保持從節點與主面接觸而不貫穿。此外還應檢查那些和主面接觸的從節點所屬單元是否受到拉應力作用。如受到拉應力，則施加釋放條件，使從節點脫離主面。就a

7、baqus接觸計算的初級使用來說，如果接觸對中有剛體，一般用penalty algorithms；如果接觸對是彈性體，有限選Kinematic algorithms. 無剛體的接觸，建議直接用Kinematic algorithms試算。總結：1）接觸面存在剛體，用penalty算法2）接觸面之間的相對運動方向平行于接觸面，用penalty算法3）彈性碰撞分析不可用hard-kinematic 算法。碰撞之中塑性變形控制的接觸分析4）penalty算法一般會減小穩定時間增量5）接觸計算與以下情況耦合時推薦penalty算法： constraint equation, multi-point c

8、onstraint, tie constraint, embedded element constraint, or kinematic constraint6）breakable bond model 模擬，必須用hard kinematic contact 。碰撞應該用罰函數法吧，要是用運動學算法時需要劃分較細的網格以避免能量的丟失。kinematic contact要求更嚴格，不允許出現穿透，而penalty contact允許。默認的Penalty stiffness為彈性剛度的10%，所以如果是解決塑性變形問題的話，二者算出來的結果相差不大。penalty對切向的相對位移的接觸比較有

9、效。3. 初始運動學依從關系 Abaqus/Explicit不允許接觸表面的初始過盈。 接觸表面的節點將被調整，刪除分析之前的初始過盈： 只移動接觸表面的節點。 對于分析過程第一個分析步定義的接觸對，由于調整表面引起的位移不產生初始應變或應力。 在隨后的分析步中： 對于接觸對算法，調整將產生應變。 對于通用接觸算法，忽略初始過盈。Contact Formulations接觸程式，包括1. Contact discretization接觸離散化Where is the constraint applied? 接觸約束應用在哪？ Node-to-surface Surface-to-surface

10、2. Constraint enforcement 執行接觸How is the constraint enforced? 接觸約束怎么執行？ Default （Explicit） Direct (Lagrange multipliers)Standard Penalty method Standard Augmented Lagrange(Lagrange multipliers combinedwith penalty method)Standard3. Contact tracking (relative sliding) 跟蹤接觸How does the constraint evol

11、ve? 接觸約束怎么發展？ Finite sliding Small slidingContact DiscretizationNode-to-surface technique: 節點和面接觸 Default method for contact pairs。接觸對的默認接觸定義方法。 Not available forgeneral contact。不適用于General contact。 Nodes on one surface(the slave surface) contact thesegments on the other surface(the master surface).

12、 從面上的節點接觸主面的面。 Contact is enforced at discrete points (slave nodes)。在從面節點處執行接觸。從面需要劃分較細的單元來提高精度和消除應力振動即消除應力噪聲。Use of a “matched mesh” across the contact interface will eliminate thissolution noise。Surface-to-surface technique：面面接觸 Only method for general contact，Alternative method for contact pairs

13、The method considers the shape of both the master and slave surfaces. Contact is enforced in an average sense over the slave surface.當面面接觸用于接觸對時，contact pairs和general contact 區別不大，主要的區別在于使用方便性和性能表現erformance。可以看出Node-to-Surface參與接觸節點個數較少。而S-to-S較多。對于面面接觸，個別點小的穿透可能會出現，但是不會發生漏檢測到的主面穿透Contact Enforceme

14、ntHard contact:In Abaqus/Standard, the default contact behavior is “hard” contact.The behavior is described by acontact property known as the pressure-penetration curve(alternative behavior can be specified; discussed later).The desired behavior (no penetration) is achieved using anenforcement metho

15、d.理想的沒有穿透的接觸行為可以用三種強化方法來獲得。Three numerical methods are available in Abaqus/Standard to achieveor approximate “hard” contact conditions:Direct enforcement method:Strict enforcement of pressure-penetration relationship using theLagrange multiplier method.嚴格壓力-穿透關系，用拉格朗日乘法算法。Pros and cons of direct enf

16、orcement：優缺點Advantages:Accuracyconstraint is satisfied exactly. Disadvantages:Adds to equation solver cost. 求解代價高Additional variable per contact constraint, which enlarges thesystem of equations to be solved.Restricts elimination order for sparse solver, which can degradeperformance.Potential conver

17、gence difficulties. 潛在的收斂問題。Abrupt change from zero contact stiffness (while contact isinactive) to infinite contact stiffness (while contact is active). 從0剛度到無窮剛度變化的劇烈。Difficulties with overconstraints.Overlap between contact constraints and MPCs, etc.Penalty method: Approximate enforcement using p

18、enalty stiffness. 用罰剛度近似。The penalty method is a stiff approximation of hard contact。罰剛度可以是：Linear (default): 線性 Easier convergence. 容易收斂 Better suited for problemsinvolving firm contact. 較適用于硬面接觸。 Difficult to choose stiffnessappropriate for all regimes. 難以選擇剛度值適用于所有情況。Nonlinear: 非線性 The lower init

19、ial stiffnessmakes it better suited forproblems involving chattering. 初始的小剛度值適合于解決包括顫振的接觸。 The higher final stiffness helpsreduce penetrations. 高的最終剛度降低穿透 Convergence overall can bemore difficult. 收斂較困難。Default penalty stiffness：默認的剛度值 Abaqus 折中選擇剛度：剛度小，過度穿透。剛度大，收斂速度；Lagrange multiplier DOF are need

20、ed to avoid ill-conditioning. The default penalty stiffness is based on a representative stiffness of theunderlying elements.A scale factor is applied to this representative stiffness to set thedefault penalty stiffness; its magnitude is higher in Abaqus/Standardthan in Abaqus/Explicit.默認剛度不合適，可以設置比

21、例系數調節。 Order-of-magnitude changes are recommended. 推薦 If the scale factor > 100, Abaqus will automatically invoke avariant of the method that uses Lagrange multipliers to avoidill-conditioning issues. 如果比例系數大于100，自動采用Lagrange multipliers 來避免病態。罰剛度值： Stiff or blocky problems：硬的或短而結實的接觸。默認剛度值產生結果：比

22、的上direct method的精確度。Requires less memory and CPU time。 Bending-dominated problems：彎曲占主導地位的接觸：默認剛度值會被縮減但是不顯著影響精確度。Scale back two ordersof magnitude without any significant loss of accuracy.Scaling back the penalty stiffness for bending-dominated problemssometimes dramatically increases the convergenc

23、e rate。縮減剛度值還或許會提高收斂率。可以看出對于Hertz接觸，默認的罰剛度值和Direct Lagrange 結果最接近。Advantages:Significantly improved convergence ratesBetter equation solver performance. No Lagrange multiplier DOF unless contact stiffness is veryhigh. Good treatment of overlapping constraints. Disadvantages:Small amount of penetrati

24、on. Typically insignificantMay need to adjust the penalty stiffness in some cases使用Used by default for each of the following:General contact、Contact pairs with the finite-sliding, surface-to-surface formulation。Automatic contact pair detection capability in Abaqus/CAE。Augmented Lagrange method: Appr

25、oximate enforcement using penalty method with augmentationiterations; not discussed further here.Used by default for:3D self contact with node-to-surface discretizationContact tracking (relative sliding)Finite slidingKinematically, finite sliding of deformable bodies against each otherallows the mos

26、t general relative motion between the bodies: Arbitrarily large sliding is allowed.Arbitrarily large rotations and deformations of the surfaces areallowed. 任意大的滑動和轉動都允許。 接觸對和通用接觸中均可以使用。Small sliding Small sliding assumes that the relative motion per slavenode remains small compared to the local curvature of themaster surface.假設從面上每個節點的相對運動相對于主面的接觸段的曲率很小。Advantage: Simplifies the numerical method. Potential for reduced cost per iteration and finding aconverged solution in fewer iterations.優點：簡化數值求解過程。收斂性好。Disadvantage: Th