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With the evolution of additive manufacturing, there is an increasing demand to produce high strength and stiffness polymers. Photopolymers are very commonly used in stereolithography and fused deposition modeling processes, but their application is limited due to their low strength and stiffness values. Nano-sized fibers or particles are generally embedded in the polymer matrix to enhance their properties. In this study, we have studied the effect of fumed nano-sized silica filler on the elastic and viscoelastic properties of the photopolymer. The uniaxial testing coupons with different concentrations of silica filler have been fabricated via casting. We observed improvement in mechanical properties by the addition of the nano-sized filler. As polymers exhibit time-dependent mechanical response, we have conducted tensile tests at different strain rates as it is one of the most common modes of deformation, and is commonly used to characterize the parameters of the rate-dependent material. We noticed significant dependence of the mechanical properties on the strain rate, quasi-linear viscoelastic (QLV) model, which combines hyperelastic and viscoelastic phenomena, has been employed to capture the response of the material at different strain rates. We found out that the QLV model with Yeoh strain energy density function adequately describes the rate-dependent behavior of the material and has reasonable agreement with the experimental results., INTRODUCTION Photopolymers are light-sensitive polymeric materials, which changes their chemical and physical properties when exposed to UV light. These photopolymers are very commonly used in additive manufacturing techniques such as [...]

This research aimed to study the efficacy of a novel implant for osteoarthritic knees. This implant is designed to eliminate excessive loads through the knee and to provide suitable conditions for possible tibiofemoral cartilage regeneration. The implant was designed for the medial side of the knee joint. Finite Element Analysis (FEA) was performed for an extended knee position of the knee joint. Contact pressure distributions on the medial and lateral compartments were investigated as well as stress distributions throughout the implant’s plates. Results with and without the implant were compared, and it was seen that the contact pressures on the surface of the distal femur were reduced by more than 90% after the introduction of the implant.

This study investigates the sliding wear resistance of the Co-28Cr-6Mo alloy manufactured by laser-based powder bed fusion through linear reciprocating sliding wear tests. Varied loads and sliding speeds, in both dry and lubricated contact scenarios, were examined using a hardened steel ball as a counter material. Microhardness profiles were obtained to understand the alloy's mechanical behavior, revealing consistent average microhardness values of 409.67 HV through the thickness and 404.05 HV along the wear track. The coefficient of friction (COF) indicated a decrease in COF with an increase in the applied normal load in both dry and lubricated contacts. On the other hand, the COF increased with higher sliding speeds, and remained stable under lubricated contact but fluctuated in dry conditions over time. Increased applied load and sliding speed correlated with escalated wear rates. Investigation of the impact of different lubricants on tribological properties highlighted synthetic gear oil as the most effective in reducing wear rate among tested lubricants. Wear mechanisms were elucidated through scanning electron microscopy and energy-dispersive X-ray spectroscopy. The presented results can serve as a guide for selecting suitable operating conditions and lubricants to reduce wear in Co-Cr-Mo alloy applications. [ABSTRACT FROM AUTHOR]

Alumina ceramic is being used extensively in various load-bearing applications. Several additive manufacturing processes have been introduced to produce alumina and other ceramic components featured with complex geometries and enhanced mechanical properties. However, the sliding wear resistance of alumina samples made by additive manufacturing processes has not been investigated in detail. In this paper, solvent-based slurry stereolithography process was employed to produce alumina components, and the tribological properties of the printed specimens were investigated by linear reciprocating sliding wear tests. The results showed that effective lubrication could significantly improve the wear resistance of the printed samples. In dry contact, the printed sample showed limited plastic flow and ductility at room temperature, and wear mechanism was dominated by fatigue induced brittle fracture. At elevated temperatures, the debris formed a protective oxidized layer, preventing excessive wear of the material. The results showed that the alumina samples manufactured by solvent-based slurry stereolithography are good candidates for load-bearing applications at extreme working conditions, such as high contact pressure, high sliding speeds, and high temperatures. [ABSTRACT FROM AUTHOR]