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FE Post Processing

FE Post Processing. Plotting Campbell Diagram Goodman Diagram Fracture Yield Principal Stress. Post Processing plots. Deformed Shape Plot. Contour Plots. History Plot. Invert Colors for Hard Copies. Campbell Diagrams. Campbell Diagram. Probabilistic Campbell Diagram.

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FE Post Processing

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  1. FE Post Processing • Plotting • Campbell Diagram • Goodman Diagram • Fracture • Yield • Principal Stress

  2. Post Processing plots

  3. Deformed Shape Plot

  4. Contour Plots

  5. History Plot

  6. Invert Colors for Hard Copies

  7. Campbell Diagrams

  8. Campbell Diagram

  9. Probabilistic Campbell Diagram

  10. Goodman Diagrams

  11. Inputs Include • Material: • Ultimate tensile strength, • Yield stress – 0.2%, • High cycle fatigue strength, • Loads • Steady stress, • Vibratory, • Half amplitude, zero-peak, • Full amplitude, peak-peak,

  12. Load Inputs

  13. HCF Test Data • Fit R=-1 data • For example: • Pick number of cycles to failure: Nf • Solve for corresponding half-amplitude stress:

  14. Goodman DiagramMaterial Inputs

  15. My Choice

  16. Fracture Mechanics

  17. Fracture Modes

  18. Stress Intensity FactorMode I Stresses near crack tip are singular and vary as the inverse square root of distance from crack tip KI is the stress intensity factor

  19. Fracture – ¼ Points

  20. Modeling Cracks

  21. Von Mises stress&Plastic Yielding

  22. Von Mises Stress is the stress tensor is the equivalent hydrostatic pressure is the deviatoric stress

  23. Invariants of Stress • Invariants do not change values when coordinate system is rotated. • The first invariant of the stress is • The second invariant of the deviatoric stress is • The third invariant of the deviatoric stress is the determinant.

  24. Uniaxial Tension :yield stress

  25. Equivalent Mises Stress • Yielding occurs when • Or when equivalent stress • When yielding occurs • Stress ratio is

  26. Principal Stresses

  27. Principal Stresses • Eigenvalues of stress tensor (matrix) are principal stresses • All values are real • Order is 1:maximum, 2: intermediate, 3:minimum • Associated eigenvectors are normal to face • Use maximum principal stress for fracture s2 y x z s1 s3

  28. Stress Contours

  29. Ansys Stress Contour Plots

  30. FE Post Processing • Plotting • Includes displaced, contour, and scatter plots • Campbell Diagram • Finds important resonances • Goodman Diagram • Predicts high cycle fatigue life • Fracture • Indicates failure due to crack propagation • Yield • Establishes yield through the use of equivalent (Mises) stress • Principal Stress • Aids in determining failure due to presence of flaws

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