SAE J3152_202005

This IR defines a general taxonomy (classification) of the most common fixture designs. This IR provides guidelines for design, fabrication, and installation to improve the way tests repeat, reproduce, and correlate to vehicle conditions. The different types of fixtures in this IR (including their preloading) apply to single-ended brake inertia dynamometer NVH testing, with a frequency range between 1.25 kHz and 16 kHz (per SAE J2521). This IR applies to passenger car and light trucks with a gross vehicle weight rating of 4536 kg or below. This IR does not address other sources of variability such as (a) test procedure itself, (b) environmental conditions, (c) dynamometer design, including its NVH test chamber, (d) data collection and data analysis methods, and (e) part-to-part, batch-to-batch, and design-level variation for brake and suspension hardware. Brake testing and measurements for noise, vibration, and harshness using inertia dynamometers are some of the most prevalent types of laboratory methods across the automotive industry. Decades of inertia dynamometer testing in multiple regions have led to multiple fixture design philosophies and methodologies, with substantial effects on the test results. Also, in the current landscape of the automotive manufacturing industry, vehicles are designed in one location, manufactured at another location(s), and sold all over the world with significant differences in environmental conditions during their life-cycles. Efforts to reproduce vehicle-level conditions in the laboratory setting (using a single brake corner assembly) need to aim at reducing redundancy, conflicting results, or high-variability in test outcomes during a given test program. This SAE Information Report (IR) provides the industry with a systematic overview of the main types of fixture designs as a function of (a) the level of hardware involved, (b) the preloading method, and (c) type of frame utilized to adapt the vehicle/brake assembly to the dynamometer. This IR also includes guidelines for best practices regarding fixture fabrication, verification, and installation in the inertia dynamometer test chamber.