1、The SS Method Must Accommodate the Following Practical Considerations结构应力法必须适应下列实际因素Arbitrary mesh designs:任意网格设计 Distorted mesh变形的网格 Mismatched element不匹配的网格 Triangle elements三角形网格 Continuously curved weld line in 3D space三维连续曲焊缝Line force/moment formulation strategy:线载荷/弯矩公式 “Work-equivalent” with
2、 respect to an entire weld line整条焊缝上“能量守恒” Traction continuity requirements at nodes along a weld line 在焊缝各节点处拉力连续Generalized Procedures for Shell/Plate Element Models Open Weld Ends壳/平面单元模型的通用求解过程-非闭合焊缝1. Collect force/moments wrt x-y-z在全局坐标系下计算节点力及弯矩2. Definite local coordinate system along weld l
3、ine: x-y-z沿焊线定义局部坐标系：-3. Rotate nodal forces/moments转换节点力及弯矩4. Solving simultaneous equations求解方程Through-Thickness Traction Conditions Using Nodal Forces用节点力作为厚度方向上的拉伸条件对于闭合焊缝：Typical Weld Representation Schemes for Using Shell/Plate Element Models使用壳/平面单元模型的典型焊缝表达方式n Equivalent stiffness 等效刚度n Full
4、 penetration weld: two rows of plate elements with “triangle formation”全熔透：用两排三角形平面单元n Partial penetration: one row of inclined elements部分熔透：用一排倾斜的单元A Lap Fillet Weld搭接焊A Padding Plate Fillet Joint垫板焊接接头（？）“Continuous” Weld Line Definition for Curved Weld Lines曲焊缝的“连续”焊缝定义SS calculated long each wel
5、d line defined by average normal vectors at a node btw two adjacentelements在相邻单元处，结构应力方向计算采用法线向量平均值A sharp angle of more than 45o may not produce a good mesh insensitivity in linear element models如果两单元法线向量夹角大于45度，会导致线性单元网格不敏感的特性有所降低管接头封闭焊缝A Wrap-Around Weld End “Continuous”环绕焊缝末端“连续”Weld Line Defini
6、tion Example焊缝定义示例Continuous weld linesalways preferred优先选用连续的焊线定义Discontinuous weld linesmust be used in a model:非连续的焊线定义应用在： Treated as separate weld line definitions按分开的焊缝来处理的情况 May show mesh-sensitivity in some cases, depending on load transfer在某些网格敏感度较高的情况，这与载荷传递模式有关Continuous Weld Line around
7、Corner Structural Stress Results (Linear Elements)拐角处连续焊线结构应力结果（线性单元）Continuous Weld Line Corner StructuralStress Results (Parabolic Elements)拐角处连续焊线结构应力结果（二阶单元）Out-of-Plane versus In-Plane Notch Effects inStructural Stress Calculation结构应力计算中面内及面外的缺口效应对比Out-of-plane (through-thickness notch effects面
8、外（沿厚度方向的缺口效应） Equilibrium conditions enforced wrt to t平衡条件严格依赖于tIn-plane notch effects面内缺口效应 Open-ended weld line with weld ends subjected to high stress concentration regime末端承受高应力集中的非封闭焊缝 Using over-simplified weld representation 使用过简化的焊缝的表示 “Weld line definitions” for “Edge Detail” (in-plane crac
9、k) 为“边缘细节”定义的焊缝（面内裂纹） SS calculation using “virtual node method”“虚拟节点法”的结构应力计算Examples with Open-Ended Weld Line: Withand Without In-Plane Notch Effects非封闭焊缝示例：考虑及不考虑平面内缺口效应Small Edge Detail Test Specimens: In-PlaneNotch Effects in SS Calculation小边缘细节试验试样：结构应力计算中面内缺口效应n Small w 较小n Nominal stress w.
10、r.t. w is wellDefined依据的名义应力容易确定n Failure criterion: full ligament(w) separation 破坏准则：剩余宽度(w)全部断开n In-plane notch effects are captured by 面内缺口效应的确定，通过： te=w in structural stress calculations结构应力计算中：te=w For symmetric edge detail te=w/2对于对称结构： te=w/2Virtual Node Method (VNM) for StructuralStress Calc
11、ulations in Structural Components结构构件中计算结构应力的虚拟节点法n Large w or not well-defined 较大或不容易确定n “Weld line” defined along w or an anticipated failure path 沿或预期的断裂路径定义“焊线”n Failure criterion: l1 w 失效准则： l1 wn Stresses along “weld line” are not statically determined Load: Virtual Node Method 沿着“焊线”的应力不由静态的载
12、荷决定： 虚拟节点法Equilibrium conditions enforced within a reference distance l (Position 2) 平衡条件限定在参考距离l内（号点位置）l1: final in-plane crack length at failure within l l1: 在l范围内面内最终裂纹失效长度Good mesh-insensitivity for l1 l/2如果l1 l/2会获得较好的网格不敏感特性Single Element Based SS Calculation UsingVNM - An Over-Simplified Plat
13、e Element Model基于单个单元的使用虚拟节点法的结构应力计算过简化的平面单元模型Comparison of VNM and Results Using Refined Weld Representation Schemes虚拟节点法与细化网格方法对比A Box Fillet Weld Example Weld Toe on Attachment Plate方角焊缝例子附加板上的焊趾W/O Weld Representation没有添加焊缝单元A Box Fillet Weld Example Weld Toe on Attachment Plate方角焊缝例子附加板上的焊趾n W/
14、 Weld Representation添加焊缝单元Intermittent Welds间断焊缝Shell versus 3D Solid Models壳单元与3D单元模型对比SS Results versusSoftware Packages结构应力结果与商用软件结果对比An Independent Evaluation of The SS and HSS Method at Rat Hole End (B. Healy, 04)结构应力法与热点应力法评估鼠洞结构（B. Healy, 04 ）的结果ISSC Longitudinal Frame/Connection Tests Analyz
15、ed by ABS (Wang et al, 2004)ISSC纵向架构连接试验（ Wang et al, 2004）ISSC Bilge Knuckle Test Analyzed by ABS (Wanget al, 2004) ISSC舱底关节连接试验（ Wang et al, 2004）Structural Stress Calculation Results结构应力法计算结果Applications of the Structural Stress Method in Multi-Axial Fatigue结构应力法在多轴疲劳中的应用Quality data are scarce缺乏
16、良好的数据Some well-known multi-axial fatigue data: EPRI, LBF,TWI, UIUC一些著名的多轴疲劳数据： EPRI, LBF,TWI, UIUC Observations: 总结： Crack tends to propagates along weld toe into plate at least for the most part of life time至少在大部分使用期限内，裂纹倾向沿焊趾向板内扩展 Based “nominal stress range”:基于名义应力幅值 Torsion is more damaging than
17、 bending扭转的破坏强于弯曲的破坏 Out-of-phase is more damagingthan in-phase loading异步载荷破坏强于同步载荷 Transverse shear often negligiblefrom these tests测试中横向剪切常常忽略Through-Thickness Normal Structural Stress厚度截面法线方向的结构应力Through-Thickness In-Plane Shear Structural Stress厚度截面的面内剪切结构应力Transverse shear (Fz) is negligible in
18、 shell/plate structures壳/板结构中横向剪切力(Fz)忽略Multi-Axial Fatigue Specimens Used by Sonsino & Kuepper (2001)多轴疲劳试样（Sonsino & Kuepper 2001）Specimen Geometry Stress calculations Using very fine mesh通过精细的网格来计算试样几何应力Structural Stress Calculations for A Plate toTube Fillet (Sonsino and Kuepper, 01)板管接头的结构应力计算(
19、Sonsino and Kuepper, 01)SAE FD&E “Weld Challenge” Tests A RHS Joint Loading in Bending and Torsion SAE FD&E 焊接挑战实验-承受弯扭的接头Fatigue Behavior of Resistance Spot Welds电阻点焊的疲劳行为The same structural stress procedure applies结构应力法同样适用 Specifically: 特殊之处： Two dominant failure modes: 两种失效模式： Sheet failure at n
20、ugget edge controlled bystress in sheet由板内应力引起的焊核边缘处板的失效 Nugget interfacial failure controlled bystresses across nugget由焊核内力引起的焊核破坏 Sheet failure mode is most important焊核边缘处板的失效更为突出 Nugget failure should be prevented byspecifying dmin焊核的失效可通过指定最小焊核直径解决Resistance Spot Welds Sheet Failure (Mode A)电阻点焊
21、-板材失效（模式）n Closed weld line around nugget periphery 封闭的焊线围绕焊核外围n Inside nugget periphery: 焊核内部区域 Either shell elements with MPC (plane remains plane)壳单元与MPC相连（平面仍保持平面） Or right beams (plane remains plane)或者合适的梁单元（平面仍保持平面）n SS calculation procedure is identical to fusion welds结构应力法计算过程与熔焊相同Mesh-Insen
22、sitivity Demonstration FE Models and Mesh Sizes Used网格不敏感的示例-有限元模型及所用的网格尺寸Comparison of Structural Stress Results with Three Models三种模式的结构应力计算结果对比Validation by Correlating S-N Data from Lap Corus Shear and Coach Peel Tests (Corus, 2001)使用相关的-曲线证明Weld Representations for Structural Stress Calculation
23、s Shell/Plate Models结构应力计算的焊缝模型-壳/板模型Laser Welded Couch-Peel Specimens激光焊模型Nominal Stress Range versus Cycles at Failure: L1 L4 specimens名义应力范围及失效循环次数：L1L4试样nFailure Mode: Sheet Failures, Aluminum Alloy Laser Welds失效模式：板材破坏，铝合金激光焊nL1-Lap Shear; L3: Coach Peel) Nominal Stress Range Structural Stress
24、Range名义应力变动范围 结构应力变动范围Courtesy Ford Motor CompanySummary Part II: Generalized Structural Stress Method总结-第二部分：通用结构应力法nConsistency and robustness 一致性和稳定性 Good mesh-insensitivity: 良好的网格不敏感 Mesh-sizes网格尺寸 Distorted elements扭曲单元 Element types/integration orders单元类型/积分阶数 Capable of handling both through
25、thickness and in-plane fatigue Failures能够处理厚度方向和面内的疲劳失效 Identical calculation procedure for:用相同的计算过程可计算 Resistance spot welds, plug welds,etc 电阻点焊，塞焊等 Laser welds, etc激光焊等 Directly applicable for characterization of multi-axial stress state可直接应用于多轴应力状态nEffectiveness in test data correlation与试验数据相关的有
26、效性 Effective over different joint types可用于不同接头类型 Effective in correlating S-N data for:用于如下S-N数据 Resistance spot welds电阻点焊 Laser welds, etc激光焊等Demo Version of SS Post-Processor and Working Session结构应力法的后处理及运行部分的演示版n Input requirements 输入要求n Demonstration on how to use the post-processor with selecte
27、d examples示范如何通过例子使用后处理n Working session: 运行部分 Lap fillet welds 搭接焊 Edge detail 边界细节 Spot and laser welds 点焊及激光焊 RHS joint SAE “WELD CHALLENGE” problem RHS接头-SAE“焊接挑战”Demo Version of Battelles Structural Stress Post-Processor Battelle结构应力法后处理的演示版nNumber of nodes describing a weld line is limited to1
28、8 nodes焊缝的节点数目不能多于18个nElement type: linear shell/plate elements单元类型：线性的壳/板单元nCommercial FE package: NASTRAN有限元软件包： NASTRANnRequires:要求 An input file describes weld line nodes and elements一个描述焊线节点及单元的输入文件 NASTRAN input file NASTRAN的输入文件 NASTRAN punch file containing GPFORCE output 包含GPFORCE 的NASTRAN
29、punch 文件Hands-On Session: Structural Stress Analysisof Welded Joints Using a SS Post-processorJK HongWeld definition file format demo version焊缝定义文件格式演示版本nWeld information input file: 焊缝信息输入文件： Nodal numbers describing a “weldline” from start to end (N1-Nn)描述焊线的节点号码从N1到Nn Node Sequence is required.要求
30、节点顺序 Element numbers along the weldline from start to end (E1-En-1)沿焊线的单元号码从E1到En-1 Element sequence does not matter. 单元顺序无所谓nElement normal directions must be consistent, pointing to local zdirection 单元法线方向必须一致，指向局部坐标ZnStructural stress calculated: with respect to y direction结构应力计算： 指向y 方向nIf N =N1
31、 a closed weldline is considered (e.g. pipe girth weld, spot weld) 如果Nn=N1 则为封闭焊缝（如：环焊、点焊）Post processor Demo Version演示版后处理Cover plate joint- straight fillet weld盖板接头-直线角焊缝Post processor output后处理输出Cover plate Straight weld (a refined mesh)盖板直线焊缝（精细网格）Curved weld-One side doubling plate曲线焊缝-单边双面n Ca
32、lculate SS along the weld toe.Detail - Weld End Effect细节-焊缝末端影响Crack propagation directionSAE FD&E Weld Challenge Problem SAE FD&E 的焊接挑战SAE FD&E Weld Challenge Problem SAE FD&E 的焊接挑战Calculate SS along the top weld toe on the 2”x6” tube.沿2”x6” 管的焊趾上面计算结构应力Current Format for Weld Definition File (for
33、bothJIP and VerityTM in fe-safeTM) Verity safe目前的焊接定义文件格式（ fe-safeTM）Hand Calculation Using Single-Element BasedVNM A Simplified Plate Element Model基于单个单元的虚拟节点法的手算简化的板单元模型Master S-N Curve Approach主SN曲线方法nHow to introduce thickness and loading mode effects? 如何引入厚度与载荷模式的影响?n Needs and challenges in in
34、troducing fracture mechanicsn引入断裂力学的必要性及问题n Generalized fracture mechanics K solutions using SS parameter通用的以结构应力为参数的断裂力学K值表达式 Elements of linear fracture mechanics 线性断裂力学单元 K solutions K值表达式 Crack growth rate and Paris law裂纹扩展速率及Paris 公式 Notch stress estimation scheme缺口应力评估方法 Generalized self-equil
35、ibrating notch stress estimation Mkn通用的自平衡缺口应力估值 MknnA two-stage crack growth law and its integration两阶段裂纹扩展规律及其合并nFormulation of an equivalent structural stress parameter等效结构应力参数公式n Validation tests: correlation of a massive amount S-N data验证试验：与大量S-N数据关联n Master S-N curve representation主S-N曲线的表示Is
36、 Structural Stress Parameter Effective in Consolidating Existing S-N Data?结构应力参数是否对加强已有的S-N数据有效果?S-N Data: Similar thickness Remote tensionHow about Considering a Wide Range of Thickness (2-100mm) and Loading Modes (Remote Tension to Bending)考虑较大变化范围的厚度 (2-100mm)及载荷模式（远端的拉力及弯矩）的情况The Results are not
37、 bad, but still not good enough结果不差但也不够好Further Consolidation Must Consider a Parameter Measuring the Following:进一步要考虑的参数：Remote Loading远端载荷模式影响？Mode effects? Thickness Effects?厚度影响Fracture Mechanics Based Considerations基于断裂力学的考虑n If crack propagation dominates fatigue life:是否裂纹的扩展决定疲劳寿命n Stress int
38、ensity factor (K) provides a unique one-parametercharacterization of the stress state at a crack tip应力强度因子(K) 提供单参数来描述裂纹尖端的应力状态n K is a function of crack size, stress state, and geometryK是裂纹尺寸、应力状态和几何形状的函数n Closed-form K solutions not available for most joint types 封闭形式的K值表达式不适合多数接头类型n Most of appli
39、cations in welded joints:焊接接头多应用于： Case-specific life predictions特殊工况寿命预测 Finite initial crack size有限的初始裂纹尺寸Needs for Developing a Single Fatigue Parameter for all Joint Types需要开发一种适合所有接头的疲劳参数n Generalized K solutions通用的K值求解算式n Generalized S-N expression of Paris-type crack growth law通用的符合Paris的裂纹扩展
40、公式的S-N表达式 “short” crack anomalous behavior?“短”裂纹不规则行为？ Long crack growth behavior长裂纹扩展行为 Is there a unified crack growth exponent m?有一致的裂纹扩展的指数m吗？n Validations of above 证实上述内容n The ultimate tests: the collapse of massive amount S-N data 最终试验：大量S-N数据的缩减Mechanics-Based Interpretation of the Structural
41、 Stress Parameter基于力学的结构应力参数解释n Through-thickness Based Weld separation in terms of membrane and bending that satisfy equilibrium conditions沿厚度方向将力分为膜力及弯矩且满足平衡条件n Statically-equivalent to the far-field stress in fracture mechanics:与断裂力学中远场应力静力等效：Structural Stress Based Single Edge Notch (SEN) K Solu
42、tion基于结构应力的单边缺口K值远端承受拉伸与弯曲载荷的单边缺口试样K值的表达式，这里拉伸与弯曲应力均为结构应力。Structural Stress Calculations can be Viewed as a Stress Transformation Process结构应力计算可认为是应力转换过程How About Contributions from the Self-Equilibrating Stress State or Notch Stress自平衡应力或缺口应力的作用Notch Stress Estimation缺口应力的估算Analytically Expressed K
43、 Solution with Notch Stress Effects考虑缺口应力影响的K值解析表达式Validations of The Structural Stress Based K Solutions基于结构应力的K值的确定Comparison of The Current and Handbook K Solutions CT Specimen with a Key Hole同手册K值对比带有中心孔的CT试样n CT Specimen with Key Hole (Ramulus, 1987)Center-Notched Specimen中心缺口试样Issues in Integr
44、ating Classical Paris Law to Relate Stress State to Life将应力状态与寿命相关联的经典Paris公式n m is assumed 3 in most Codesand Standards for steel 在多数钢结构规范及标准中同M指定为3n Examination of some reported crack growth data showed a da wide scatter band 查看一些裂纹扩展的报告显示da形成宽分布带n C varies more significantly thanm indicating spec
45、imen geometry dependenceC的变动比m更为显著说明其依赖试样的几何形状n “Short crack” phenomena maycontribute to some“短裂纹”现象可能贡献一些n Crack growth data in un-weldedspecimens should be applicable裂纹扩展数据在非焊接结构上也是适用的Crack Growth Data from Tanaka and Nakai, Y(1983) Center Notched Specimens Tanaka 等的裂纹扩展数据中心缺口试样 After Adding Addit
46、ional Data: Specimen Geometry Effects附加数据中试样几何形状的影响A Unified Approach for both Long and Short Crack Growth A Two Stage Growth Model长、短裂纹扩展的统一方法两阶段扩展模型How to Reliably Determine n and m from Highly Controlled Crack Growth Rate Testing?如何从裂纹扩展速率试验中可靠地确定n及mAluminum Alloys versus Steels and Short Cracks
47、versus Long Cracks铝合金同钢的对比及长、短裂纹的对比SS Based K Solutions and Crack Growth Rate Analysis基于结构应力的K值及裂纹扩展速率分析n K solutions have been further validated K值求解已经进一步验证n Two-stage growth law unified short and long crack growth data 两阶段扩展规律统一了长、短裂纹数据 Mkn dominated Mkn 控制 Kn dominated Kn控制n A unique slope exists
48、 (3.5 to 3.6) Similar between aluminum alloys and steels 一致的斜率(3.5 to 3.6) 铝合金与钢材相似n How to derive a simple SS based fatigue parameter? 如何得到简单的基于等效结构应力的疲劳参数？Two Classes of Mkn Curves两种Mkn 曲线A Unified Mkn(a/t) by Superposition (approximation)叠加的统一Mkn(a/t)值（近似） Formulation of Fracture Mechanics Based
49、Equivalent Structural Stress Parameter Ss基于断裂力学的等效结构应力参数Ss表达式Initial Crack Size (ai/t) and Mkn Effects on I(r) Integration初始裂纹尺寸(ai/t)及Mkn对I(r) 积分的影响Effectiveness of The Equivalent Structural Stress Parameter等效结构应力参数的有效性Some Comments on Edge Crack Based I (r)基于边裂纹的I(r)相关问题n Weak dependency on r 与r弱相
50、关n K based on load controlled conditions K值基于载荷控制条件n Some S-N data showed stronger bending effects 一些S-N数据显示较强 的弯曲效应n K based on displacement controlled conditions? K值基于位移控制条件？Approximate K Solution Displacement ControlledK值的近似求解位移控制I(r): Demonstration of Load Controlled versusDisplacement Controlle
