Contact-coupled impact of slender rods: analysis and experimental validation

Area of Science:

• * Mechanics of Materials
• * Structural Dynamics
• * Computational Engineering

Background:

• * Understanding contact mechanics in low-speed structural impacts is crucial for predicting material behavior and structural integrity.
• * Existing analytical and finite element (FE) models require validation against experimental data for complex impact scenarios.
• * Accurate modeling of contact phenomena is essential for designing reliable mechanical systems and prosthetics.

Purpose of the Study:

• * To validate analytical and finite element (FE) models of contact mechanics in low-speed structural impact scenarios.
• * To compare experimental measurements of contact and vibration with predictions from established theoretical and computational models.
• * To establish confidence in using these validated models and diagnostic tools for analyzing more complex structures, including biomechanical applications.

Main Methods:

• * Experimental validation using a drop tower to impact slender rods, measuring contact area (thin-film transfer) and duration (electrical continuity).
• * Recording vibratory strain (strain gages) and speed (laser Doppler vibrometer) during impact.
• * Developing and comparing a 1D analytical model (quasi-static Hertzian contact, delay differential equations) and a 3D FE model (hexahedral elements, penalty contact, explicit integration) with experimental data.

Main Results:

• * Experimental measurements closely matched model predictions: contact areas within 6%, peak speeds within 2%, cyclic strains within 12 με (RMS), and contact durations within 2 μs.
• * The FE model identified small disturbances not predicted by the analytical model, attributed to stress wavefront interactions with rod ends.
• * High accuracy across multiple parameters validates the computational and analytical approaches.

Conclusions:

• * The experimental validation confirms the accuracy and reliability of both analytical and finite element models for low-speed structural impact.
• * The diagnostic tools and methodologies employed are versatile and suitable for studying contact mechanics in more complex structures.
• * The validated methods are recommended for biomechanical applications, such as analyzing edge-loading in prosthetic hip joints to prevent wear and failure.