Porous structures made of metal or biopolymers with a structure similar in shape and mechanical properties to human bone can easily be produced by stereolithographic techniques, e.g. selective laser melting (SLM). Numerical methods, like Finite Element Method (FEM) have great potential in testing new scaffold designs, according to their mechanical properties before manufacturing, i.e. strength or stiffness. An example of such designs are scaffolds used in biomedical applications, like in orthopedics' and mechanical properties of these structures should meet specific requirements. This paper shows how mechanical properties of proposed scaffolds can be estimated with regard to total porosity and pore shape.
Selective laser melting is widely used for custom-designed elements. Successful manufacturing depends on laser treatment parameters and material features. This research aimed to determine the effects of laser power, scan time and hatch distance on surface quality, relative density and dimensional precision for cuboids made of the Ti-13Zr-13Nb alloy. The influence of energy density, energy flux and pre-heating was seen to be decisive to different degrees for the quality of the final specimen. The results obtained were used to produce prosthetic crowns and bridges. The thermal stresses that appeared resulted in a deflection of the bridges and consequently in a change in design approach.
The key requirement for the modern endoprosthesis is high durability of the friction components, which results in long and trouble-free operation in the human body. The durability of currently used endoprosthesis is often limited by tribological wear processes of friction components (e.g. between the head and the acetabular component in a hip joint endoprosthesis) [8,19,23,24]. In order to compare the tribological wear, tribological tests were carried out by means of tribometer on friction pairs of the following composition: implantation steel 316 LVM/PE-UHMW and titanium alloy Ti13Nb13Zr/PE-UHMW. Determining of the friction coefficient, measured profiles of surface roughness and microscopic observation allowed to evaluate the abrasive wear of the tested biomaterials.
The fabrication of the prosthetic foundations and bridges from the Ti-13Zr-13Nb alloy is described. The process was started from CAD/CAM design of 3D models of the foundations based on scanning of patient`s mouth. Next, 3D models were transformed into *.stl files for the manufacturing stage and then the manufacturing process by means of the selective laser melting with the SLM Realizer 100 equipment was made. The intrinsic structure of the obtained parts was investigated with X-ray microtomography. The observed imperfections in the foundation's internal structure can be eliminated by a proper setting of the laser melting process. The thermal stresses, which resulted of the temperature change during melting and caused the bending of titanium made bridges, were eliminated at a design stage.
The elimination of mineral oil-based lubricants from machines has multiple beneficial effects on the naturalenvironment. Firstly these lubricants are a direct threat to the environment in the event of leaks; secondly their elimination reduces the demand for crude oil from which they are obtained. In addition, in many cases,e.g. when replacing traditional lubricants with water, friction losses in the bearings can also be reduced due tothe lower viscosity of the water, which reduces the energy dissipation in machines.On the other hand, the introduction of self-lubricating materials or water-lubricated bearings causes problemsrelated to the need to adapt the design of machines and materials used to new operating conditions and changedproperties of the lubricants. In the paper, selected examples of problems related to the use of ecologicallubricants are discussed. The high cost of PEEK based polymers resulted in the emergence of cheapersubstitutes on the market; however, in the conducted research, the substitutes presented worse properties thanthose declared by their manufacturers.
Metal – polymer sliding contacts are a typical combination in industry and medicine. For decades such a set of materials has been the primary choice in human joints endoprosthetic technology. In this paper tribological issues of are presented from a research on the potential for practical use of Ti-13Nb-13Zr/UHMW-PE couple for orthopedic endoprosthesis. In tests on simplified models it is critically important to carefully select geometry of contact, load and velocity magnitudes and profiles to the later interpretation of results. In case of organic polymers interacting with metallic components the problem is even more prominent, than in the case of all metal systems because of great differences in the modulus of elasticity between the specimens in contact. High local loading can cause excessive heat generation and accelerated loss in polymer’s strength induced by thermal plastification. The process may not be manifested in the course of the experiment in any way detectable and might compromise the accuracy of wear measurement. In the case of the presented research an analysis has been performed to evaluate the observed wear profile of UHMW-PE with respect to non-uniform distribution of contact stress. A simulation was run with the use of FEM to evaluate the contact conditions between the titanium alloy and UHMW-PE specimens and the results were confronted with the wear profiles. Interesting similarities were discovered yielding useful information on the fundamentals of the wear in and for future research on similar systems.
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