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Current research uses a finite element analysis to characterize the effect of the materials mechanical and tribological properties on the interaction between the biological tissues of a transfemoral amputation and the combined prosthesis. Considering that both friction and mechanical properties influence the stress distribution between different interfaces, these were analyzed on the contacts of the prosthesis and the liner, the liner and the soft tissues and, finally, the soft tissues and the cortical bone. This is of significant importance, as it has been acknowledged that the shear stress distribution at these interfaces significantly impacts the patients’ comfort. These shear stresses have also been reported as one of the leading causes of pressure ulcers in osteotomized patients. Finally, this research discusses the influence of the soft tissues and the liner constitutive law in the stress field generated at the biological tissues. In particular, for the liner, the results using a linear elastic model are compared with those using the Mooney-Rivlin hyperelastic model. The results using a linear elastic model are compared with the Neo-Hookean and Ogden models’ results for the soft tissues.

The use of numerical modelling tools allows optimizing the development of complex anatomical artefacts, such as customized prostheses for lower limb amputees. These numerical tools make it possible to characterize the interfacial interactions taking place between different parts of the prosthesis and the residual limb. This allows for understanding which rectifications and fittings having to be made on the custom design of the artificial body part without the need for manufacturing and donning prostheses. To such end, current research focused on the development of a preliminary Finite Element Model to assess the effects of friction on the residual limb of a transfemoral amputee, as the friction on the contact between the soft tissues, the liner and the prosthesis of the amputee is of major importance for his/her health and comfort.

Neste artigo é avaliado o efeito das propriedades mecânicas e tribológicas dos materiais na interação entre os diversos componentes da prótese numa amputação transfemoral, através de uma análise por elementos finitos. O modelo numérico é desenvolvido sobre o software MSC.marc. O atrito vai influenciar a distribuição de tensões entre as diversas interfaces – prótese/liner, liner/tecidos moles e tecidos moles/osso cortical. A distribuição das tensões de corte junto às interfaces, influencia o conforto do paciente, sendo uma das principais causas da geração de úlceras de pressão nos pacientes amputados que usam este tipo de próteses. É analisada a influência dos modelos constitutivos utilizados na modelação dos tecidos moles e do liner, na distribuição de tensão. Em concreto são comparados os resultados obtidos com a utilização de um modelo linear elástico com os obtidos com modelos hiperelásticos.

Within a pulp industry production process, a drop in the performance of a wood log rotary debarker was identified. Such loss of performance was due to the occurrence of excessive wear of the device’s cutting blades, requiring their regular and premature replacement. The material used to manufacture the cutting blades, Hardox 500, has characteristics considered adequate for the required use. However, it was concluded that the blade manufacturing process degraded its mechanical properties, leading to its premature wear when placed in service. The present study intends to propose, characterize, and validate an alternative cutting process to manufacture the debarker’s cutting blades. Abrasive waterjet cutting technology was proposed to produce the cutting blades. The suitability of this manufacturing process is discussed considering the specified geometry and the material characteristics of the resulting cutting blades.