Abstract
The first part of the paper presents a literature overview on the topic, followed by a side-by-side comparison of international standards (ISO 6310, SAE J2468, JIS D4413) (1, 2, 3) with other methods used by the industry. The second part presents new efforts among working groups and task forces to quantify and minimize variability; along with several proposals to enhance laboratory-testing practices. These proposals are based on recent (or ongoing) research work, on new needs stemming from new brake system development, new parking brake system techniques and technologies, and on the overall industry need to reduce the overall test-cycle cost and duration. These efforts include non-destructive testing while increasing the statistical validity of test results. The third, and final part, presents a series of recommendations regarding test preparation techniques to increase repeatability (test-to-test) and reproducibility (machine-to-machine or lab-to-lab), improvements on machine operation and verification during regular testing. The discussion also covers the use of statistical methods to validate/approve new testing systems, compare different results using critical differences, assess part-to-part variability, ensure continuous performance within acceptable limits, and compare different test methods.
KEYWORDS – compressibility, low-preload, specific compressibility, parking brake, viscous-elastic, high-energy braking, shims, validation