Similarity index: A procedure for comparing impact time histories validated with soft impact test

Abstract

This paper describes the procedure developed to compare the dynamic behavior of a structure due to an impact load. The comparison procedure is especially useful for controlling the impact level and repeatability during testing, but it can also be used for fine-tuning the process of simplified models or finite element models. Both features provide important engineering value and permit the assessment of transient impact histories, qualitatively and quantitatively. More than 240 soft impacts, from a human impact against glass test campaign, have been used to develop and validate the comparison method.Three indicators have been defined in order to control the most significant impact parameters: the impact level (impulse), duration of the impact (stiffness), and maximum acceleration (peak system response). Based on the knowledge of the impact phenomena, the procedure defines a Similarity Index (SIn) that entails the weighted addition of the indicators. The SIn procedure assigns a numerical value to the difference between two time histories over the duration of the contact, and it is used to compare a series of data from a database of soft human impacts tests versus standard glass curves and curves obtained from a simplified 2DOF model.

Método alternativo para registrar el nivel de excitación en ensayos de impacto humano

“…Durante el trabajo inicial se desarrolló un modelo simplificado de dos grados de libertad (2GDL) (Postigo Pozo 2010) (Alonso et al 2017)que permite contrastar los resultados experimentales. Otros autores también utilizan este tipo de modelo para estudiar este fenómeno (Fröling et al 2014) (Schneider & Schula 2016).…”

“…Como se menciona en el apartado 2.5, dentro del trabajo llevado a cabo por el grupo de investigación se desarrolla un criterio de comparación llamado Índice de Similitud (ISn) (Alonso et al 2019). Este se centra en la carga aplicada por el elemento impactador obtenida con la historia temporal de la aceleración multiplicada por la masa.…”