Training Manual Aug Contact and Bolt Pretension Three main areas of contact enhancements in ANSYS 5.7: A.Thermal Contact B.Node-to-Node Contact C.Bolt Pretension

Training Manual Aug Contact and Bolt Pretension A. Thermal Contact Coupled-field structural-thermal contact. –Supports general thermal contact analysis capability. –Typical applications: Metal forming Assembly contact Gas turbine Thermal Assembly Frictional Heating

Training Manual Aug Contact and Bolt Pretension...Thermal Contact Coupled-field solids (PLANE13, SOLID5) and surface-to-surface contact elements with KEYOPT(1) = 1 –Can also be used with pure thermal elements Fix all structural DOFs on contact elements Key features: –Heat conduction between contacting surfaces –Heat generation due to frictional dissipated energy –Heat convection and/or radiation Between surfaces with small gap From free surface to environment –Heat flux input at open gap

Training Manual Aug Contact and Bolt Pretension...Thermal Contact Heat conduction:q = TCC * (T T - T C ) –TCC is thermal contact conductance coefficient (real constant) Can be table parameter (function of pressure and temperature) –T T and T C are target and contact surface temperatures –Heat flows when contact status is closed –Model temperature discontinuity across contact interface No  T (continuous material)  T (contact interface)

Training Manual Aug Contact and Bolt Pretension...Thermal Contact Frictional heat generation: q = FHTG *  * v –FHTG is fraction of energy converted to heat (real constant) –  is the equivalent frictional stress –v is the sliding rate –Heat can be distributed unequally between contact and target: q c = FWGT * FHTG *  * v q t = (1-FWGT) * FHTG *  * v Brake Pad on Wheel

Training Manual Aug Contact and Bolt Pretension...Thermal Contact Convection:q = CONV * (T E - T C ) –CONV is convection coefficient (SFE table parameter load) –T E is target temperature, or bulk temp for free surface (SFE) –T C is contact temperature –Heat flows between contact and target when 0 < gap < pinball –Heat flows from contact to environment for free surface Free surface is recognized for any of these conditions: –Open far-field contact (gap > pinball) –Contact elements only (omit target elements) –If target elements are present, Keyopt(3)=1 for target elements

Training Manual Aug Contact and Bolt Pretension...Thermal Contact Radiation: q = RDVF * EMIS * SBCT * [(T E + TOFFST) 4 - (T C + TOFFST) 4 ] –RDVF is radiation view factor (real constant) RDVF can be table parameter (function of time, temp, gap distance) –EMIS is surface emissivity (material property) –SBCT is Stefan-Boltzman constant (real constant) –TOFFST is temperature offset from absolute zero (TOFFST command) –Heat flows between contact and target when 0 < gap < pinball –Heat flows from contact to environment for free surface Free surface recognized as for convection

Training Manual Aug Contact and Bolt Pretension...Thermal Contact External heat flux input –SFE applied to contact surface only (not target surface) Heat flux acts only if contact status is open For near-field contact, the flux acts on both contact and target For free surface flux acts only on contact element –Free surface recognized as for convection –Cannot be applied simultaneously with convection on a given element

Training Manual Aug Contact and Bolt Pretension...Thermal Contact Thermal contact tips –Conductance TCC Has units of heat / (time*degree*area) Typically less than the equivalent conductance of contacting solids –For frictional heating, TIME must have true chronological units However, if structural inertia and damping are unimportant, turn them off with TIMINT,STRUC,OFF for faster solution –Unsymmetric solver option may benefit frictional sliding NROPT,UNSYM

Training Manual Aug Contact and Bolt Pretension B. Node-to-Node Contact New node-to-node element: CONTA178 –Pure Lagrange, augmented Lagrange, or pure penalty algorithms Pure Lagrange permits tiny penetrations (best accuracy) –User-definable contact normal direction (several options) –Advanced surface behavior options (bonded, no- separation, ramped interference, etc.) –User-definable initial gap or interference –Element damper available (for closed gap status) –Semi-automatic real constants (factors) –Radial gap option –Weak spring option for open gap –Unsymmetric solver option (NROPT)

Training Manual Aug Contact and Bolt Pretension...Node-to-Node Contact Limitations: –Pure Lagrange can’t be used with PCG solver –Do not use with midside noded elements –Small deflection and small sliding only New node-to-node contact element generation tools –EINTF enhancements User-specified DX, DY, DZ offset values –Useful for either coincident or offset (noncoincident) nodes User control over node number ordering EINTF,,,REVE flips normal direction –NORA and NORL to help define contact directions normal to contact surface Rotate nodal coordinate systems to be normal to surface

Training Manual Aug Contact and Bolt Pretension C. Bolt Pretension New tools enhance bolt pretension modeling –Useful for creating, managing, and loading structures having multiple pretensioned bolts (no limit on the number of bolts)

Training Manual Aug Contact and Bolt Pretension...Bolt Pretension Pretension sections created as named “Sections” –Procedure is similar to 5.6 creation Preprocessor > Sections > Pretensn Mesh Managed similar to beam sections (list, modify, delete) Preprocessor > Sections > List Sections Assign a section number and name

Training Manual Aug Contact and Bolt Pretension...Bolt Pretension Easier pretension load management –Apply pretension loads to named sections –Easy control of pretension sequencing –Semi-automated “locking” of pretension displacements SECT NAME PT.NODE NORMAL KINIT KFD FDVALUE APPLY LOCK 1 bolt TINY F 0.100E bolt TINY F 0.100E bolt TINY F 0.100E