SOLIDWORKS Simulation - “Durability Analysis for Random Vibration”

What is Random Vibration Fatigue?

• Structures or Mechanical components are subjected to random form of loading.
• Wind Loads, Wave Loads, Car engine operating on different moving roads are such examples.
• Random loading changes over time.
• Random vibration involves dynamic loading conditions.

Random Vibration Fatigue

• Three methods to compute the expected damage ratio due to random loading Fatigue.

•   Narrow Band Method
•   Steinberg Method
•   Wirsching Method
• Loading and response are random processes
• Frequency based fatigue is required for such loading conditions.
• They use statistical measures for solutions.
• Requires a Dynamic random vibration study run for Fatigue calculation.
• New Fatigue study involves stress PSD(Power Spectral Density)

What are Dynamic Loads ?

• Dynamic loads are classified to deterministic or non deterministic.
• Deterministic loads defined are functions of time and predicted precisely.
• They are harmonic, periodic or non periodic.
• Non deterministic loads cannot be defined as functions of time.

X Axis -  Frequency(Hertz)

Y Axis -  PSD (Amplitude²/ Frequency)

Benefits for Fatigue Analysis

• Calculates the Fatigue Strength Reduction Factor(Kf).
• The calculation takes place when the corrected alternating stress is less than the endurance limit.

Advantages

• Life will provide the Time for Fatigue Failure
• Damage will provide the percentage of Life during the Random Vibration Loading conditions.