Ansys Mechanical Fatigue Life Predictionhalf-day course
This course covers the use of the Ansys Mechanical Fatigue module available with Ansys Mechanical Pro, Ansys Mechanical Premium, and Ansys Mechanical Enterprise licenses. Fatigue tools enabled by nCode design life are not covered in this course.
The course offers a high level introduction to fatigue theory including stress life and strain life approaches. Mean stress corrections are discussed including Goodman, Soderberg, and Gerber methods for stress life calculations and Smith Watson Topper and Morrow methods for strain life calculations. Stress life workshops include simple non-proportional loading using solution combination and non-uniform load history utilizing the Rainflow counting method. The strain life workshop emphasizes proper use of mean stress correction techniques when calculating equivalent stress values for tensile vs compressive cases.
The course also includes two appendix workshops from DRD’s Ansys Mechanical Structural Dynamics course covering life predictions for random vibration and harmonic response analysis.
Prerequisites for this course are DRD’s Introduction to Mechanical course and some practical experience using Ansys Mechanical.
Chapter 1 - Introduction to Fatigue Theory and the ANSYS Mechanical Fatigue Module
Workshop 1 - Stress Based Fatigue Life Prediction for a Shaft with Axial and Shear Loading using the ANSYS Fatigue Module
In this workshop we introduce the Mechanical Fatigue module to predict life on a stepped shaft using a stress based approach. Axial and bending load cases are calculated independently followed by solution combination for the simple non-proportional load case of fully reversed bending under constant axial tension. Goodman mean stress correction is implemented. Workbench parameterization is implemented to obtain fatigue life for various step radii values.
Workshop 2 - Fatigue Life Prediction for a Motorcycle Fender Bracket Using the Strain Life Method
In this workshop, users implement a strain based approach within the Mechanical Fatigue Module for fully reversed loading near or exceeding the material yield strength. Morrow mean stress correction is implemented with emphasis on using the correct stress output for compressive mean stress adjustment.
Workshop 3 -Fatigue Analysis of a Trailer Spindle Subjected to Time Series Load History
In this workshop, users learn how to import unidirectional time history load data from a test track into the Mechanical Fatigue Module. Stress life calculations are performed using Rainflow methodologies for various amplitude vs mean stress bin values with Goodman mean stress correction. Emphasis on the tradeoff between accuracy and solver time with respect to binning is given.
Dynamics Workshop 2 - Random Vibration Analysis of a PWB Assembly
In this workshop, students define a random vibration PSD spectrum and learn how to calculate 1 sigma, 2 sigma, and 3 sigma stresses. Fatigue life is calculated using the Steinberg Method. Students learn how to create a user defined result to calculate zero crossing frequency and validate the Mechanical Fatigue Module results using hand calculations.
Dynamics Workshop 8a -Harmonic Response Analysis of an Engine Alternator Bracket
In this workshop, students learn how to calculate maximum stresses and deflections on a motor bracket subject to harmonic loading. Students utilize the Mechanical Fatigue Module to calculate the expected time to failure of the bracket when the harmonic load frequency corresponds to the first natural frequency.