RESULTS OF MATHEMATICAL MODELING OF TENSION-DEFORMED CONDITION OF COMPONENTS OF KNEE JOINT ENDOPROSTHESIS IN CONDITIONS OF PRESENCE OF DEFECT EFFECTS

Summary. Gonarthrosis is reported in 50.6–54.5% of cases among patients with the lower extremities large joints’ dystrophic diseases. In 86% of cases, it affects people of working age, and in 6.5–14.6% - leads to disability. That is why, gonarthrosis is an acute medical and social problem. However, despite the large number of surgeries, the matter of choosing a method (bone plastic, metal insertion) to cover a bone bed’s defects for total knee arthroplasty (KJ) is still ambiguous. Objective: to conduct a computer simulation of strains occurring upon a regular and extended tibial stem of a knee prosthesis, depending on different tibial condylar defects. Materials and methods: the laboratory of biomechanics of the SI “ITO NAMS of Ukraine” created a computer model to study stress-deformed conditions of a KJ endoprosthesis upon a varus deformity of an extremity and knee arthroplasty with a regular and an extended tibial stem, if a bone defect has been replaced with a bone autograft of 5 and 10 mm. Results. It was determined that if a knee arthroplasty occurs upon conditions of a varus deformity, with an internal tibial condyle’s defect, the defect can be filled with an autograft insert up to 5 mm high, and a regular (short) prosthetic stem is suitable. If such a lesion is from 5 mm to 13.5 mm, an extended prosthetic stem is biomechanically justified. If a height of the defect exceeds 13.5 mm, it must be replaced with a massive metal insert. Practical essence: the study will be helpful to elaborate a differentiated approach to various tibial condyles’ defects treatment in the course of the total knee arthroplasty. Conclusions. The implementation of recommendations resulting from this study will increase the efficiency of treatment to this severe category of patients.

Metal-insert technique for polypropylene composite bipolar plate manufacturing

A single cell of direct methanol fuel cell (DMFC) typically delivers an electrical potential between 0.5 and 1 V; thus DMFCs are assembled in parallel to meet power demands (1–5 kW). Bipolar plates (BPs) are the primary components connecting a single cell to the adjacent cells so that they provide optimum electrical conductivity. The objective of this research is to reduce the volume resistance of BPs made from a polypropylene/carbon composite by utilizing a metal insert technique. A major obstacle when it comes to molding composite plates inserted by a thin metal sheet is the delamination of material layers after the cooling process. The delamination issue is due to different surface polarities between metal and polypropylene-composite surfaces. One of the strategies to solve this issue is to modify the surface of one layer for creating similarity of the surface polarity. A metal sheet surface was coated with graphene using a cold spraying technique to enhance adhesion ability. The suitable spraying conditions were determined by experimenting with varying temperature, pressure, graphene quantity and graphene types. The effectiveness of surface modification by the graphene spraying technique was assessed by a surface morphology observation, an electrical conductivity measurement and DMFC performance tests. Results were interesting, they indicated that when DMFC was assembled with silver sheet, inserted BPs provided 25.13 mW/cm2 of power density, 3,350.7 mWh of generated energy and 67% of efficiency. This highlights that the performance of a BP prototype is superior to the performance of a commercial composite bipolar plate.

Research on the Performance of Metal Connectors of Injection-Molded Long-Glass-Fiber Reinforced Thermoplastic Composite Wheel

In order to ensure stiffness and wear resistance of joint surface, injection-molded long-glass-fiber reinforced thermoplastic (IMLGFT) composite wheel is installed on hub or metal table of wheel test bench by fastening bolts through metal connectors. Firstly, the structure of composite wheels with metal connectors is simplified. Then the strength analysis is carried out to test the two kinds of simplified models by using superposed beams theory and ABAQUS finite element software respectively based on the wheel bending fatigue test. In addition, the stress conditions of the wheel using the metal insert or the metal clamp plate are compared. The results show that two structural forms of metal connectors have protective effect on the composite parts of the wheel, and the protective effect of metal clamp plate connector on composite parts is better than that of metal insert connector. The research results provide guidance for the metal connector design of IMLGFT composite wheel.