【正文】 m of the work is zero. On the other hand, if the force system in the virtual displacement (strain) and virtual and is equal to zero for the work, they must balance equation. Virtual displacement principle formulated the system of force balance, therefore, necessary and sufficient conditions. In general, the virtual displacement principle can not only suitable for linear elastic problems, and can be used in the nonlinear elastic and elasticplastic nonlinear problem. Virtual mechanical meaning of stress principle: if the displacement is coordinated, the virtual stress and virtual boundary constraint counterforce in which they are the sum of the work is zero. On the other hand, if the virtual force system in which they are and is zero for the work, they must be meet the coordination. Virtual stress in principle, therefore, necessary and sufficient condition for the expression of displacement coordination. Virtual stress principle can be applied to different linear elastic and nonlinear elastic mechanics problem. But it must be pointed out that both principle of virtual displacement and virtual stress principle, rely on their geometric equation and equilibrium equation is based on the theory of small deformation, they cannot be directly applied to mechanical problems based on large deformation theory. 3, the minimum total potential energy method of minimum total potential energy method, the minimum strain energy method of minimum total potential energy method, the potential energy function in the object on the external load will cause deformation, the deformation force during the work done in the form of elastic energy stored in the object, is the strain energy. The convergence of the finite element method, the convergence of the finite element method refers to when the grid gradually encryption, the finite element solution sequence converges to the exact solution。s law。t change the shape and volume of the object, namely the rigid body displacement is not deformation displacement. Spatial displacement of an object includes three translational and three rotational displacement, a total of six rigid body displacements. Due to a unit involved in the other unit, other units do rigid body displacement deformation occurs will drive unit, thus, to simulate real displacement of a unit, assume that the element displacement function must include the rigid body displacement. 4) the displacement function must be coordinated in public boundary of the adjacent cell. For general unit of coordination is refers to the adjacent cell in public node have the same displacement, but also have the same displacement along the edge of the unit, that is to say, to ensure that the unit does not occur from cracking and invade the overlap each other. To do this requires the function on the mon boundary can be determined by the public node function value only. For general unit and coordination to ensure the continuity of the displacement of adjacent cell boundaries. However, between the plate and shell of the adjacent cell, also requires a displacement of the first derivative continuous, only in this way, to guarantee the strain energy of the structure is bounded. On the whole, coordination refers to the public on the border between neighboring units satisfy the continuity conditions. The first three, also called pleteness conditions, meet the conditions of plete unit is plete unit。線彈性有限元法是一種理想的彈性體為研究對(duì)象，考慮到基于小變形假設(shè)。2）幾何非線性幾何非線性問(wèn)題是由位移非線性關(guān)系引起的。有限元理論基礎(chǔ)有限元方法是基于變分原理和加權(quán)余量法，及其解決的基本思想是將計(jì)算域劃分為有限個(gè)互不重疊的單元，在每個(gè)單元，選擇一些合適的節(jié)點(diǎn)作為解決插值函數(shù)，在改寫(xiě)的變量或其導(dǎo)數(shù)插值節(jié)點(diǎn)選擇的價(jià)值和功能線性表達(dá)變量的微分方程，用變分原理和加權(quán)殘值法的幫助下，微分方程的離散解。無(wú)論采用何種方法，設(shè)置試功能時(shí)應(yīng)注意以下幾點(diǎn)：（1）試驗(yàn)函數(shù)應(yīng)由完備函數(shù)集的子集組成。虛功原理：平衡方程和幾何方程的等效積分形式的“弱”的虛擬工作原則包括虛擬位移和有效應(yīng)力原理的總稱，是原則的虛擬位移和虛擬應(yīng)力理論。應(yīng)力原理虛擬力學(xué)意義：如果位移協(xié)調(diào)，虛擬應(yīng)力和虛擬邊界約束反力在他們的工作和為零。多項(xiàng)式是單值連續(xù)函數(shù)，所以選擇多項(xiàng)式作為位移函數(shù)，保證單元內(nèi)的連續(xù)性.。對(duì)象的空間位移包括三平移和三個(gè)旋轉(zhuǎn)位移，共有六個(gè)剛體位移。第三條，也叫完整條件，滿足條件的是完整的單位是完整的單位；第4條是協(xié)調(diào)要求，滿足協(xié)調(diào)單位協(xié)調(diào)單位；否則稱為協(xié)調(diào)單位。單元（2）面積細(xì)分，根據(jù)解面積的形狀和物理特性的實(shí)際問(wèn)題，將截面積劃分為若干個(gè)相互連接、重疊的單元。對(duì)于本質(zhì)邊界條件和混合邊界條件，應(yīng)采用一定的方法來(lái)修正一般有限元方程的滿足。（4）單位將分析：針對(duì)每個(gè)單元與單元基函數(shù)的函數(shù)近似表達(dá)的線性組合；然后近似函數(shù)代入積分方程和單位面積積分，可以得到與待定系數(shù)（即細(xì)胞參數(shù)值）的代數(shù)方程組中的每個(gè)節(jié)點(diǎn)，被稱為有限元方程。每個(gè)單元的剛度矩陣和單元?jiǎng)偠染仃嚭蛦卧獎(jiǎng)偠染仃嚭蛦卧獎(jiǎng)偠染仃嚕?）集成總剛度矩陣集成總剛度矩陣集成整體剛度矩陣集成總剛度矩陣和寫(xiě)出一般平衡方程并寫(xiě)出總體平衡方程并寫(xiě)出總體平衡方程和編寫(xiě)一個(gè)通用公式4。要做到這一點(diǎn)就要求公共邊界函數(shù)只能由公共節(jié)點(diǎn)函數(shù)值確定.。為了反映應(yīng)變單元的狀態(tài)，單元必須包括位移函數(shù)往往應(yīng)變。但必須指出的是，虛位移原理和虛應(yīng)力原理，依賴于它們的幾何方程和平衡方程是基于小變形理論，它們不能直接應(yīng)用于基于大變形理論的力學(xué)問(wèn)題。虛位移原理的力學(xué)意義：如果力系是平衡的，則虛位移和虛應(yīng)變由功之和為零。如果計(jì)算問(wèn)題具有對(duì)稱性，應(yīng)充分利用它。是一類直接從微分方程和邊界條件的解出發(fā)，尋求數(shù)學(xué)方法邊值問(wèn)題的近似解。如結(jié)構(gòu)的彈性屈曲問(wèn)題屬于大位移小應(yīng)變，橡膠件的大應(yīng)變成形過(guò)