Ab s t r a c t High-power low-frequency ultrasound in the range 20-60 kHz has wide ranging clinical applications in surgical and medical instruments for biological tissue cutting, ablation or fragmentation, and removal. Despite widespread clinical application and common device operating characteristics, there is an incomplete understanding of the mechanism of tissue failure, removal and damage. The relative contribution of cavitation, direct mechanical impact and thermal effects to each process for specific tissue types remains unclear. Different and distinct mechanisms and rates of tissue removal are observed for interaction with soft and hard tissue types. Device operating parameters known to affect the interaction include frequency, peak-peak tip amplitude, suction and application time. To date, there has been little analysis of the effect of variations in, and interactions of, these parameters on tissue removal and damage for individual biological tissue types. Potential controllable damage mechanisms occurring in tissues include alteration in global biomechanical properties, histomorphological changes, protein denaturation and tissue necrosis. This paper presents a critical review of the literature on the clinical application, mechanism of tissue interaction, removal and residual tissue damage. It describes known mechanisms for distinct tissue types.
Abstract:This paper addresses the energy absorption responses and crashworthiness optimisation of thin-walled oblong tubes under quasi-static lateral loading. The oblong tubes were experimentally compressed using three various forms of indenters named as the flat plate, cylindrical and a point load indenter.The oblong tubes were subjected to inclined and vertical constraints to increase the energy absorption capacity of these structures. The variation in responses due to these indenters and external constraints were demonstrated. Various indicators which describe the effectiveness of energy absorbing systems were used as a marker to compare the various systems. It was found that unconstrained oblong tube (FIU) exhibited an almost ideal response when a flat plate indenter was used. The design information for such oblong tubes as energy absorbers can be generated through performing parametric study. To this end, the response surface methodology (RSM) for the design of experiments (DOE) was employed along with finite element modelling (FEM) to explore the effects of geometrical parameters on the responses of oblong tubes and to construct models for the specific energy absorption capacity (SEA) and collapse load (F) as functions of geometrical parameters . The FE model of the oblong tube was constructed and experimentally calibrated. In addition, based on the developed models of the SEA and F, multi-objective optimization design (MOD) of the oblong tube system is carried out by adopting a desirability approach to achieve maximum SEA capacity and minimum F. It is found that the optimal design of FIU can be achieved if the tube diameter and tube width are set at their minimum limits and the maximum tube thickness is chosen.
Abstract.The present work presents both numerically and experimentally the quasi-static lateral compression of nested systems with vertical and inclined side constraints. The force-deflection response of mild steel short tubes compressed using two types of indenter's is examined. The variation in response due to these indenters and external constraints are illustrated and how these can contribute to an increase the energy absorbing capacity of such systems. The implicit version of the Finite Element code via ANSYS is used to simulate these nested systems and comparison of results is made with those obtained in experiments and were found to be in good agreement.Keywords: tubes, energy absorption, finite element, plastic deformation, lateral compression, quasi-static, ANSYS.
Notation.
AArea under the force-deflection curve
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