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FE Post Processing Plotting Campbell Diagram Goodman Diagram Fracture Yield Principal Stress

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POST PROCESSING PLOTS

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Deformed Shape Plot

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Contour Plots

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History Plot

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Invert Colors for Hard Copies

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CAMPBELL DIAGRAMS

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Campbell Diagram

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Probabilistic Campbell Diagram

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GOODMAN DIAGRAMS

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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,

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Load Inputs

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HCF Test Data Fit R=-1 data – For example: Pick number of cycles to failure: N f Solve for corresponding half-amplitude stress:

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Goodman Diagram Material Inputs

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My Choice

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FRACTURE MECHANICS

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Fracture Modes

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Stress Intensity Factor Mode I Stresses near crack tip are singular and vary as the inverse square root of distance from crack tip K I is the stress intensity factor

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Fracture – ¼ Points

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Modeling Cracks

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VON MISES STRESS & PLASTIC YIELDING

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

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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.

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Uniaxial Tension :yield stress

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

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PRINCIPAL STRESSES

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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 11 22 33 x y z

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STRESS CONTOURS

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Ansys Stress Contour Plots

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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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