Varied approaches to loading assessment in fatigue studies.

Area of Science:

• Mechanical Engineering
• Materials Science
• Reliability Engineering

Background:

• Estimating fatigue life is critical for extending the service life of machine parts.
• Traditional methods include time-domain (Rainflow) and frequency-domain (Dirlik) approaches.
• The choice between these methods impacts the accuracy and efficiency of longevity assessments.

Purpose of the Study:

• To compare the effectiveness of the Rainflow and Dirlik methods for fatigue life estimation.
• To provide evidence supporting the preferable use of the Rainflow method in specific engineering contexts.
• To discuss the necessity and application scope of spectral methods in fatigue analysis.

Main Methods:

• Experimental fatigue testing of aluminum specimens under regular and irregular loading.
• Building a fatigue life curve (Gassner curve) from experimental data.
• Comparing longevity estimations from Rainflow and Dirlik methods.

Main Results:

• The Rainflow method demonstrated stable and reliable fatigue life estimations.
• Experimental results provided evidence favoring the Rainflow method over frequency domain approaches.
• The Dirlik method showed some issues with parameter selection during longevity assessment.
• For narrow-band processes, both methods yielded comparable results.

Conclusions:

• The Rainflow method is recommended for general fatigue life estimation, especially for recorded time-history data.
• Spectral methods should be restricted to specialized situations where they offer distinct advantages.
• Further research should focus on refining the application of existing methods rather than developing complex, overlapping algorithms.