Ansys Workbench Study1. SpaceClaimSource->Make Independent;Component, Analysis, Share Topology, Share: for meshing;Create a coordinate system at the centre of selected objects;Use ‘Prepare’ & ‘Repair’, especially ’Imprint’ for splitting surfaces and ‘Split Body’ for simplification;No need to deal with contacts;Do not remove duplicate faces using ‘Duplicates’, which may cause body converted to surface;Table 1 Processes for modification in Ansys SpaceClaim2. Mechanical：Steady-State ThermalEngineering Data:Change the *.xml file version to Ansys versionFor creep model, it’s one period of time that counts not transient state.Units: µmksGeometry:Material assignment;Named Selection: for name selection when setting boundary conditions and postReference temperature: for zero thermal strain reference temperature, use welding temperaturesSymmetry:Model->Symmetry, Num Repeat 2, Method Half, ΔX = 1e-14m, Workbench Tools Appearance Beta check;Table 2 Processes for symmetry boundary conditions in Ansys MechanicalMeshing:Number of Divisions 3; Geometry, select one edge and Size, select all entities with the same size; Bias Type and Bias Factor;Meshing method: MultiZome/Sweep; hexagonal mesh is better; If use tetrahedral mesh, do not use degraded tetrahedral elementsTable 3 Processes for modification in Ansys MechanicalBoundary conditions:For convection surfaces, select the surfaces layer by layer, cross use ‘Single Select’ and ‘Box select’, make full use of ‘Hide Boday' and ‘Hide All Other Bodies’, and alternating ‘Face’ and ‘Body’;No need deal with contacts;Table 4 Processes for thermal initial and boundary conditions in Ansys MechanicalInternal Heat GenerationAnalysis Settings:Radiosity Controls for convergenceSolution:Solution Information: Solution Output to choose convergence curves;3. Mechanical: Static StructuralA quasi-static process is a process that happens slowly enough for the system to remain in internal equilibrium. The thermal stress process can be seen as quasi-static process, which means: when the temperature changes, the stress and strain changes immediately. Therefore, it doesn’t matter to use ‘Static Structural’ or ‘Transient Structural’ as they give the same result. Ansys Workbench:From ‘Steady-State Thermal’ right click ‘Solution’ select ‘Transfer Data to New’ ‘Static Structural’;Imported Load: Imported Body Temperature, Source Time: AllThermal Conditions:At the high temperature dwell time, relaxation will be fast compared to the low temperature range; thus, a stress-free state much closer to the high temperature setpoint will settle in, with an overlay of thermal and mechanical excursions. Stresses will of course be higher in the low temperature range. (Poech & Eisele, 2000)Boundary Conditions:Restrict the 6 DOF, Frictionless Support for two symmetrical surfaces, Displacement z=0 for one point;Or follow Figure 1 for any object.Figure 1 Restriction of the 6 DOFTable 5 Processes for structural boundary conditions in Ansys MechanicalElement Birth and Death:To activate/deactivate elements in a step.Analysis Settings:Set multi-step for changing loading to capture specific time points.Initial time step: 1e-2s, Minimum time step, 1e-30s; Maximum time step: around 100s for long thermal cycles;Step Controls can be defined by Time/Substeps for convergence; Nonliear Controls Force Tolerance can be increased to 5%;Large Deflection: On, for large deflection convergence;Restart Controls: add load separately, can be used for substep save in case the program exit by accident, but it will enlarge the file size dramatically!Output controls: Specified Recurrence Rate, 2 to reduce the output file size by half.Solution:Neglect the warning about the CTE reference temperature.User defined result: NLPLWK (non-linear plastic work)APDL:To output specific times:! Commands inserted into this file will be executed just prior to the ANSYS SOLVE command.! These commands may supersede command settings set by Workbench./NERR,,1000000OUTRES,erase*dim,t_out,,17! RESULTS OUTPUT TIME ARRAYt_out(1) = 1800, 3600, 10800, 10801, 14400, 14401, 18000, 18001, 21600, 21601, 25200, 25201, 28800, 28801, 32400, 32401, 39600OUTRES,all,%t_out% ! OUTPUT RESULTS AT TIME SPECIFIED BY THE ARRAY! Active UNIT system in Workbench when this object was created: Metric (m, kg, N, s, V, A)! NOTE: Any data that requires units (such as mass) is assumed to be in the consistent solver unit system.! See Solving Units in the help system for more information.Note: the output result will also be these specified time points! How to solve this problem? Miscellaneous：Tools, Options, Mechanical, Miscellaneous, Save Options: for auto save4. Mechanical：Transient-State ThermalAnsys Workbench:Analysis Settings: loads can change against time in one step; Set the end time for one step; Loads can be added directly in Tabular Data; Steps can be used for different processes with Element Birth and Death. Time steps can be controlled, APDL commands need to be added for specific times.Magnitude: Tabular Data/Function5. Mechanical：Transient StructuralNo need to use transient structrual solver for thermal stress, as this is for the term with time differential. For thermal stress it has the same result with ‘Static Structural’.For nonlinear stepped (not ramped) external force load, there would be dynamic effect and transient structural.6. Q3D ExtractorDefine Variables: Q3D Extractor>Design Properties;Q3D Extractor>Set Background Material: the default background material is “vacuum”;Define the Source/Sink: Right-click and then choose Select Face, right-click in the Modeler window, and then click Assign Excitation>Source/Sink from the shortcut menu.Identify the Nets: To automatically create nets: Right-click in the Modeler, and then click Auto Identify Nets from the shortcut menu.Parametric Sweep: Q3D Extractor>Optimetrics Analysis>Add Parametric.Mechanics and FEM1. Linear elasticityThe governing equations of linear elasticity are (Wikipedia):Equation of motion:σji,j+F i=ρðtt u iThese are 3 independent equations with 6 independent unknowns (stresses).Strain-displacement equations:εij=12(u j,i+u i,j)These are 6 independent equations relating strains and displacements with 9 independent unknowns (strains and displacements).Constitutive equations:σij=C ijklεklWhere C ijkl is the stiffness tensor. These are 6 independent equations relating stresses and strains.2. Viscoplastic models1) Anand model: Yield strength and creep are included; Anand model calculates the change rate of inelastic strain, including both plastic strain and creep strain, which means, the inelastic strain calculated is an accumulated quantity. The inelastic strain rate is a quasi-static quantity for Ansys Static Structural Analysis. The 9 constants: s 0,Q R ,A,ξ,m,ℎ0,ŝ,n,a . Flow equation:εin =Ae −Q RT [sinh (ξσs)]1m Evolution equations:s ={ℎ0(|B |a B |B |)}εinB =1−s s ∗ s ∗=ŝ[εin A e Q RT ]nwhere εinis the inelastic strain rate, A is the pre-exponential factor, Q is the activation energy, m is the strain rate sensitivity, ξ is the multiplier of stress, R is the gas constant, T is the absolute temperature, ℎ0is the hardening/softening constant, a is the strain rate sensitivity of hardening/softening. The quantity s ∗ represents a saturation value of s associated with a set of given temperature and strain rate. ŝ is a coefficient, and n is the strain rate sensitivity for the saturation value of deformation resistance (Wang, Cheng, Becker, & Wilde, 2001).For Anand model, make sure the plastic strain increment is enough small to capture the response.The yield strength increases while temperature drops down.Figure 2 Anand model stress-strain curvesThe plastic strain can drop down (Definition, 2010).Study Anand model deeply and consider making a GUI program to plot stress-strain curves again the Anand model constants.2) Stress relaxation is the observed decrease in stress in response to strain generated in thestructure. This is primarily due to keeping the structure in a strained condition for some finite interval of time and hence causing some amount of plastic strain. This should not be confused with creep, which is a constant state of stress with an increasing amount of strain.(Wikipedia)3) Creep (sometimes called cold flow) is the tendency of a solid material to move slowly ordeform permanently under the influence of persistent mechanical stresses. It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods and generally increases as they near their melting point. (Wikipedia)3. Thermal stress1) Factors: Temperature, CTE difference, Temperature gradient (simple simulation verified)2) If there is only thermal condition for one body component, no other load (6 DOF restricted),the equivalent stress is 0.IGBT and Electronics1. P-N junctionBias is the application of a voltage across a p–n junction; forward bias is in the direction of easy current flow, and reverse bias is in the direction of little or no current flow. The forward-bias and the reverse-bias properties of the p–n junction imply that it can be used as a diode. (Wikipedia)2. IGBTAn insulated-gate bipolar transistor (IGBT) consists of four alternating layers (P-N-P-N) that are controlled by a metal-oxide-semiconductor (MOS) gate structure without regenerative action. (Wikipedia)3. ElectromagneticsThe Maxwell Capacitance Matrix: A Maxwell capacitance matrix provides the relation between voltages on a set of conductors to charges on the conductors.Figure 3 Capacitances between four conductors (Lorenzo, 2011)Figure 4 Maxwell capacitance matrix (Lorenzo, 2011) Equivalent frequency in LC circuit:f0=12π√LC。
