Evaluation method of allowable variance for results of tribological measurement on the basis of their the coherence trends and of the covariance trends

• Main Authors: Zboiński Marek, Lindstedt Paweł, Deliś Maciej
• Format: Article
• Language: English
• Published: Sciendo 2015-12-01
• Series: Journal of KONBiN
• Subjects: ball bearing; the diagnostic signals; diagnostic level; the variance of data; covariance; coherence
• Online Access: https://doi.org/10.1515/jok-2015-0052

This article discusses the possibility of assessing the technical condition of rolling bearings based on tribological tests of oil samples. The problem is to define diagnostic levels, especially when has a relatively small number of measurements (3, 4, 5 etc.). Rating variance of measurements can be performed using the dimensionless factor covariance ρ(τ) and the dimensionless coherence function γ2(ω). The set is compact enough when ρ (τ) and γ 2(ω) will be close enough to oscillate around the value of 1 [1, 3]. In summary, it is concluded that the thresholds δ, 2δ, 3δ are reliable when ρ (τ) and γ 2(ω) are greater than 0.7 [6].