{'fraction_non_alphanumeric': 0.021751254880089235, 'fraction_numerical': 0.0016731734523145567, 'mean_word_length': 5.571428571428571, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Characterization of friction joints subjected to high levels of random vibration

When designing optical devices, the alignment of every element is integral to the proper functionality of the device. If any of these elements is secured by means of a friction joint, it is important to understand the limitations of the joint when vibrations (mainly during launch) occur; a phenomenon called "stick-slip" may happen and permanently displace joints relying on friction and cause optical misalignments. There is little to no data documenting the characteristics of the "stick-slip" phenomenon on friction joints under random vibratory motion. The test program was designed with the aim of gathering data that would broaden the understanding of the "stick-slip" phenomenon and among other things provide sufficient information to quantify the static coefficients of friction of several single-bolt friction joint material pairings. This paper describes the test program in detail including test sample description, test procedures, and vibration test results of multiple test samples. The material pairs used in the experiment were Aluminum-Aluminum, Aluminum- Dicronite coated Aluminum, and Aluminum-Plasmadize coated Aluminum. Levels of vibration for each set of twelve samples of each material pairing were gradually increased until all samples experienced substantial displacement. Data was collected on 1) acceleration in all three axes, 2) relative static displacement between vibration runs utilizing photogrammetry techniques, and 3) surface galling and contaminant generation. This data was used to estimate the values of static friction during random vibratory motion when "stick-slip" occurs and compare these to static friction coefficients measured before and after vibration testing.