• Document: Advanced bolt assessment through process automation
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Titelmasterformat durchANSYS Bolt Assessment inside Klicken bearbeiten Advanced bolt assessment through process automation © CADFEM 2014 Contents • Short presentation of VDI 2230 • Workflow with Bolt Assessment inside ANSYS (BAIA) • Demo • Comparison with reference examples • Additional informations © CADFEM 2014 Titelmasterformat VDI 2230 Part 1 durch Klicken bearbeiten © CADFEM 2014 Brief Overview of Guideline VDI 2230, Part 1: Calculation Steps • Nominal Diameter and • Assembly Stress R0 Limiting Size R7 • Tightening Factor • Working Stress R1 R8 • Minimum Clamping Force • Alternating Stress R2 R9 • Subdividing the working • Surface Pressure R3 load/load factor R10 • Changes in Preload • Length of Engagement R4 R11 • Min. Assembly Preload • Sliding, shearing R5 R12 • Max. Assembly Preload • Tightening Torque R6 R13 © CADFEM 2014 Limitations of VDI 2230 Part 1 • Nonlinear material behavior (e.g. plasticity, creeping) • Nonlinear status (i.e. load dependent contacts, sealings incl. fluid penetration) • Geometric nonlinearities (large deflections during upward movement) • The load introduction factor has to be estimated • Finding the length of lever arm a for an eccentric force transmission can be quite difficult, calculations are cumbersome… Source: User Manual KISSsoft Source: User Manual KISSsoft © CADFEM 2014 5 Titelmasterformat VDI 2230 Part 2 durch Klicken bearbeiten © CADFEM 2014 Assessment of bolted connections via FEM • VDI 2230 Part 2 1. Scope 2. Normative references 3. Terms and definitions 4. Symbols and abbreviations 5. Calculation method and approaches to solutions 6. Analytical calculations 7. FEM-Application 7.1 Fundamental Approach 7.2 Modeling 7.3 How to derive the solution quantities from the FE Analysis 7.4 Verification of loading capacity supported by guideline VDI 2230 Part 1 © CADFEM 2014 7 Model Class I • Objective of the Calculation Internal forces at the joint used as an input for calculations through VDI 2230 Part 1 • Equivalent Model Modeling the assembly contains resilience of the structure which means that load distribution on the full assembly is taken into account. In the vicinity of the interface parts will be bonded (no pretension applied) • Postprocessing At connection reaction forces will be post processed from FE Analysis. According to VDI 2230 Part 1 -> Dimensioning -> Verification © CADFEM 2014 8 Model Class II and III • Calculation Goal Internal forces of the screw calculated in the FE-analysis are used as input quantity for the calculation analogous to VDI 2230 Part 1 • Modeling Screw is considered as a dummy element analogous to VDI 2230 Part 1 Preload is considered The interface is represented by a contact The calculation considers max. respectively min. preload based on the type of bolt © CADFEM 2014 9 Model Class II • Modeling • Represent resilience of bolts and all preloaded parts • Bolt through beams -> dN shaft diameter -> d3 screw thread Depending on connectivity the resilience of thread, screw and head has to be taken into account • Include preload -> Fm_FE_min, Fm_FE_max 2 calculations • Consider the loss of preload © CADFEM 2014 10 Model Class III • Modeling • Reproduce resilience of bolts and all parts involved • Bolt represented as a solid -> dN diameter of the shaft -> d3 diameter of the thread Head and screw nut will not be modeled in detail, thread resilience will not be modeled, this will result from the local displacement • Preload is included -> Fm_FE_min, Fm_FE_max 2 calculations • Consider loss of preload • Multi-zone mesh © CADFEM 2014 11 Realization: verification of load capacity based on VDI 2230 Part 1 For a verification in dependence upon VDI 2230 the following loads must be below the acceptable threshold: • Working stress • Alternating stress • Surface pressure at the bolt head and nut bearing area • Safety factor against slipping In addition a sufficient length of

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