白车身模态分析流程、建模指导书及标准

白 车 身模 态 分析流程及建模 标 准Company Confidential概述1.几何模型修正2.几何模型读取3.单元尺寸的定义和模型划分 4.模型的合并 5.施加载荷和边界条件 6.分析计算 7.结果的后处理 8.修改设计Company Confidential分析流程 图几何模型修正几何模型读取单元尺寸的定义和模型划分模型的合并施加载荷和边界条件结果的后处理修改设计Company Confidential几何模型修正在建立几何模型的过程中 ,有可能发生几何特征缺失或者产生一些不必要的小碎面，这些几何错误都需要进行清理，否则会影响有限元模型的质量、计算的精度和速度，具体的方法是进行缝合、修补或合并。可以将 N个面合并成一个面（此种方法只限对模型质量要求不高的情况），但关键的特征线应该保留，如拐角、和孔等。Company Confidential几何模型修正Company ConfidentialSURFACE EDITparametric cubic mathematical representationComplex mathematical representation12314235611 221Can use simultaneously with all surfacesSurfaces have continuous slopeCompany ConfidentialPATRAN相关的几何模型修正Point 35Parametric Surface 6Trimmed surface with holeTrimmed surface 8 with holeParametric surface without holeTrimmed surface 4Remove VertexParametric surfacePoint 44Parametric Surface 2New VertexTrimmed surfaceCompany Confidential几何模型读取：一般公司的数学模型都按照层管理的模式进行，通常不同的层存储不同的信息，在模型读入后，可以将多余的层删除，将有用的面移入当前层中，如条件允许可以将当前层的名称改成零件名称。便于以后添加材料性质卡和辨别零件。 PATRAN可以较为方便的将整车的各个不同的零件进行分组并进行管理Company ConfidentialCAE模型的建立根据计算机的能力和要求的精度确定合适的网格大小，划分网格。如果机器的能力和时间允许，可以将单元尺寸划分的小一些（但不能太小），如可以按照碰撞的计算要求进行划分，这样同一个模型既能够计算模态分析，有可以模拟碰撞 .Company Confidential网格划分 Advanced Surface MesherBenefits Drastically reduce analysis modeling time the same part can now be meshed in less than a minute originally, it would take at least 30 minutes Reduce cost Increase productivity Build quality finite element models with minimal user interactionGapNon-CongruentSurface boundariesCompany ConfidentialUser Scenario 1Verify : Surface : BoundaryMany internal free edges GapNon-CongruentSurface boundariesCompany ConfidentialUser Scenario 1Verify : Surface : BoundaryMany internal free edgesOverlappedSurface boundariesGapCompany ConfidentialUser Scenario 1Create initial tri-meshPseudo surfacesInitial MeshCompany ConfidentialUser Scenario 1Create initial tri-meshPseudo surfacesCompany ConfidentialUser Scenario 1Pseudo surface cleanupVerify element free edgesCleanupVerify Free edgesCompany ConfidentialUser Scenario 1Pseudo surface cleanupCreate congruent meshes (based on user defined tolerance) Select initial tri-mesh Set tolerance to .1194 new elements created293 free edges have been stitchedVerify free edges againAll internal free edges and overlaps have been eliminated 2 gaps needs to be manually stitchedMake CongruentCompany ConfidentialUser Scenario 1Pseudo surface cleanupStitch free edges Select free edge Use “ Free Edge of 2D Element“ selection iconUse polygon pick to select the entire gapRepeat for all known gapsStitchingThis tool will close the gaps of areas defined by the selected edges. Also, This tool will close the gaps without any checking of tolerance values.Company ConfidentialUser Scenario 1Additional manual mesh simplificationMerge pseudo faces to eliminate skewed or sliver surfacesCreate higher quality final mesh SimplifyMerge 16 pseudo faces into 1 faceMerge FacesCompany ConfidentialUser Scenario 1Additional manual mesh simplification1 faceCompany ConfidentialUser Scenario 1Create Final MeshSelect all pseudo facesEnter desired final element sizeFinal MeshCompany ConfidentialCAE模型网格 质 量控制如果要得到精度 较 高的 计 算 结 果 ,网格的 质 量是是至关重要的 .相 对 于模 态 分析求解网格控制如下 单元翘曲角：不大于 20度 单元长度 ：通常按照 10mm划分，但最小单元长度不要小于5mm。 单元长宽比：小于 1： 5 雅各比 ：大于 0.5 最小四边形内角：大于 40度 最大四边形内角：小于 135度 最小三角形内角：大于 15度 最大三角形内角：小于 140度 三角形占全部单元比例：整个模型最好小于 10%，最多不多于15%，对单个零件的要求可以放松，最多可到 30%（小零件）。 Company ConfidentialIRREGULARITY CHECKSn General mesh/element checksu Boundary or “Crack” detectionu Elements Duplicationu Normalsu Nodal connectivityu Jacobiann Element specific distortion checksu Deviation form basic shaped elements, i.e. tapern Curvature and singularity tests for quadratic elementsn Color-coding based on node or element ID numbersCompany ConfidentialVERIFY ELEMENT BOUNDARYn Plots the boundary as free edges, or optionally free facesn Free edge/face of an element is the edge/face of the element not common (tied to) with othersn Cracks or free edges appear along geometric boundaries prior to equivalencingCompany ConfidentialVERIFY ELEMENT BOUNDARY FREE EDGESHex mesh example:Hex mesh Free edge display before equivalencingFree edge display* after equivalencingTet mesh Free edge display before equivalencingFree edge display after equivalencingTet mesh example: Dashed (blank) area indicates more than one tetSolid line indicates only one tetCompany ConfidentialDISTORTION CHECK OF HEX ELEMENTSn The Test Option gives an overview for the current groupObject:Company ConfidentialTYPICAL VERIFY FORMAspect Warp Skew TaperCompany Confidential模型的合并一个白车身由若干个零件组成，模型的合并是一个复杂的事情。一般情况下有两种办法：一种是先进行各大总成的合并，如侧围、地板等，各个总成合并完成后，再进行白车身的合并。此种办法比较简单，而且焊接顺序可以结合车间的焊接顺序进行，比较容易理解，建议初学者使用。另一种办法是将所有的模型全部读入，然后依次将各个零件进行焊接。按照此种办法，需要对车身结构和焊接非常了解，连接过程中经常会遗漏部分焊点，需要反复几次计算才能全部完成。但这种方法有助对白车身的透彻了解。建议熟练后采用。Company Confidential焊点的连接方式 在给出的焊点坐标附近，用两个 RBE2单元连接，或采用一个零件（厚度较大的零件）的节点做主点，相连零件的两个节点做从点的方法。三层板件焊接，中间点作为主点。一般不推荐一个焊点只采用一个 RBE2单元（只有两个节点连接）的方式。Company Confidential施