{'fraction_non_alphanumeric': 0.015353805073431242, 'fraction_numerical': 0.0, 'mean_word_length': 5.461206896551724, '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}}
Holography as a quantitative modal testing technique applied to a brake drum in view of correlation with FE data

Classical Modal Testing techniques, using accelerometers, are faced with problems of mass loading and spatial resolution if lightweight structures and/or high frequency modes have to be measured. Until today, holographic techniques, such as Electronic Speckle Pattern Interferometry (ESPI) are mainly used as a qualitative rather than quantitative measurement technique and usually lack the capability to measure phases of the vibration. An approach, using ESPI, has been developed which allows to measure the response displacement of the complete structure in amplitude and phase format. If referenced to the measurement of input force, it allows to obtain the complete frequency response functions, which can then be processed by classical modal parameter identification techniques in order to extract the frequency and mode shape information. The approach has the advantage to give very high density spatial information (several thousands points measured simultaneously without mass-loading) in a numerical format directly usable for further numeric analysis. This paper explain the approach and shows how it has been used to perform a modal analysis of a brake drum, in view of a correlation analysis with the FE model of this drum. It will discuss practical aspects involved in the measurements, present obtained results and highlight possible further development and automation.