A reliability model for friction and wear experimental data

Tribology experimental research has been a considerable improvement during the last years, leading to a significant amount of results and consequently an increasing number of papers appear every month. Unfortunately, in spite of this development, the obtained results usually are characterized by big scatter and significant discrepancies can be founded for the same materials if tested by different research teams. The scatter found in the data has been frequently attributed to many variables involved in the experiments, namely: environment (especially humidity), contaminant layers, differences on test conditions, uncertainty on the results evaluation and rarely on the experimental equipment response. The control of the test variables, the atmosphere and also the test procedure can play an important role on the results reliability but accurate equipments and careful laboratory practices certainly could improve the quality of the results. However, the basic problem remains and even taking into account all that statements, the results could have significant scatter. This work aims to discuss several sources of imprecision which lead to scatter of the experimental tribology results. The usual experimental procedure used to calculate performance parameters, namely wear and friction coefficients will be compared to other solutions, including energy approaches. A reliability method will be proposed to characterize friction and wear data. Experimental results obtained by unidirectional sliding and by micro-abrasion will be used to support the discussion.