Micro-oscillating indentation of viscoelastic solids: A combined numerical, analytical and experimental investigation

Abstract:

Viscoelastic materials exhibit complex time-dependent behaviors critical for applications in engineering and biomedical fields, necessitating accurate predictive models. This study combines experimental, numerical and theoretical approaches to characterize the normal indentation of viscoelastic behavior of nitrile butadiene rubber (NBR) under harmonic loading conditions. Indentation is fundamental either as it marks a variety of applications, including e.g. all the viscoelastic dampers, and, crucially, as it is commonly employed to characterize viscoelastic materials, especially in the biomedical case. Experimental tests were performed using custom-designed sinusoidal indenters, with results validated through numerical simulations based on the Boundary Element Method (BEM) and benchmarked against a simplified yet effective theoretical approach. Key findings include strong agreement between theory and experimental outcomes, with minor deviations observed in peak force and relaxation phases. These results confirm the reliability of integrating experimental and computational methodologies for characterizing viscoelastic materials and emphasize their significance in the design and optimization.

Keywords:

Indentation; Viscoelasticity; Dissipated work.