Lessons learned from the test-to-test variability of different types of wear data

Area of Science:

• Tribology
• Materials Science
• Mechanical Engineering

Background:

• Many experimental tribology studies report single test results, neglecting data variability.
• Wear data, similar to other material properties, exhibit inherent repeatability and reproducibility (R/R) challenges.
• Lack of R/R data makes it difficult to validate material rankings and the significance of experimental variables.

Purpose of the Study:

• To characterize and analyze the repeatability and reproducibility (R/R) of wear data.
• To investigate sources of variability in wear testing, including material homogeneity and experimental parameters.
• To provide guidance on the number of replicate measurements needed for reliable wear behavior analysis and material ranking.

Main Methods:

• Analysis of R/R across various wear mechanisms and test methods, including ASTM standards.
• Case studies comparing R/R for different wear forms: cavitation erosion, three-body abrasion, solid particle erosion, dry sliding wear, and fuel lubricity (BOCLE test).
• Examination of factors influencing R/R, such as material properties, units of measure, and experimental variables.

Main Results:

• Wear data exhibit significant variability, impacting the reliability of single-test results.
• R/R differs across various wear types and testing methodologies.
• Wear transitions can influence the overall R/R of test results.

Conclusions:

• Establishing R/R is crucial for validating wear test results and material rankings.
• Understanding R/R helps determine the necessary number of replicate tests for robust conclusions.
• This analysis offers practical insights for improving the reliability and interpretability of wear testing in tribology.