Edmund Morris

Plastic Response of Nested Systems under Static and Dynamic Loading Conditions Using FE and Experimental Techniques

This paper presents the study of nested rings crushed laterally between rigid platens at 2 different velocities. In this investigation two different types of nested ring configurations are analysed: (A) In-Plane; where three rings of varying diameter are placed within each other and their axes are parallel. (B) Out of-Plane; where the rings have a 90 degree orientation. Material used was cold finished, drawn over mandrel (DIN 2393 ST 37-2) and is referred throughout the paper as mild steel. The Cowper-Symonds relation was used to predict the dynamic yield stress of the rings and this was included in the FE material model. The results obtained from experiments were compared to that of finite element method using the software package Ansys. Discussion is made on the post – collapse behaviour of these systems. It was found that the Out of-Plane ring system exhibited a more desirable force-deflection response due to its 90 degree orientation.

High Power, Low Frequency Ultrasound: Meniscal Tissue Interaction and Ablation Characteristics

This study evaluates high power low frequency ultrasound transmitted via a flat vibrating probe tip as an alternative technology for meniscal debridement in the bovine knee. An experimental force controlled testing rig was constructed using a 20 kHz ultrasonic probe suspended vertically from a load cell. Effect of variation in amplitude of distal tip displacement (242-494 μm peak-peak) settings and force (2.5-4.5 N) on tissue removal rate (TRR) and penetration rate (PR) for 52 bovine meniscus samples was analyzed. Temperature elevation in residual meniscus was measured by embedded thermocouples and histologic analysis. As amplitude or force increases, there is a linear increase in TRR (Mean: 0.9 to 11.2 mg/s) and PR (Mean: 0.08 to 0.73 mm/s). Maximum mean temperatures of 84.6°C and 52.3°C were recorded in residual tissue at 2 mm and 4 mm from the ultrasound probe-tissue interface. There is an inverse relationship between both amplitude and force, and temperature elevation, with higher settings resulting in less thermal damage.

Experimental and Numerical Analysis of Circular Tube Systems Under Quasi-Static and Dynamic Loading

In the study of impact attenuation devices, rings/tubes have received a large amount of research due to their adaptability, i.e. they are low in cost and are readily available for selection in the design process. They also exhibit desirable force-deflection responses which is important in the design of energy absorbing devices. The function of such a device is to bring a moving mass to a controlled stop and ideally cause the occupant ride down deceleration to be within acceptable limits so as to avoid injuries or to protect delicate structures.

Experimental and numerical analysis of slotted tube systems under quasi-static loading

In this study of impact attenuation devices, rings/tubes have received a large amount of research due to their adaptability, that is, they are low in cost and are readily available for selection in the design process. They also exhibit desirable force deflection responses which is important in the design of energy absorbing devices. The function of such a device is to bring a moving mass to a controlled stop and ideally cause the occupant ride down deceleration to be within acceptable limits so as to avoid injuries or to protect delicate structures. In this work, the quasi-static analysis of nested circular tube energy absorbers is examined using experimental and numerical techniques. Although these devices are usually exposed to much higher velocities, it is common to analyse the quasi-static response first, since the same predominant geometrical effects will also occur under dynamic loading conditions. In this investigation two different types of nested tube configurations are analysed: (1) In-Plane; where three tubes of varying diameter are placed within each other and their axes being parallel. (2) Out of-Plane; where the tubes have a 90° orientation. Both of these systems contain slotted tubes. The purpose of the slots is to achieve a desirable force-deflection response. A numerical technique via the finite element method is used to simulate the loading and response of such devices and hence, comparison of numerical and experimental force-deflection response is presented.