In the present paper, a three-dimensional finite element model of the Charnley implant has been developed to analyze the stress–strain distribution and deformation over the stem prosthesis. Patient-specific dynamic forces have been considered for the analytical evaluation using commercial finite element code. The impact of each dynamic activity has been analyzed separately using six different biocompatible alloy materials made of titanium and cobalt-chromium. Mechanical parameters have been evaluated to envisage the longevity and functionality of the implant. The performance of different materials for each suitable gait pattern is analyzed using finite element code. Consequently, Cobalt chromium alloys (CoCrMo alloy) demonstrate better results, i.e., maximum stress, minimum deformation, and strain as compared with other materials. Every dynamic motion, viz., walking, standing up, sitting down, going upstairs, and going downstairs are found in good agreement with the safety factor for every biomaterial. Additionally, going downstairs and sitting down gait motion exhibits the maximum and minimum stress–strain level, respectively. Based on the outcome of the presurgical study, it is recommended that CoCrMo alloys should be preferred over other materials.
Abrasive flow machining (AFM) is one of the non-conventional finishing processes used to attain good surface quality and high material removal. However, limited attempts have been made to improve the performance of these processes. This paper presents a novel magnetic abrasive flow machining (MAFM) setup fabricated by adding a magnetization effect in which a nylon fixture and permanent magnets are replaced by a newly fabricated aluminium fixture and coil-type magnets, respectively. Inner cylindrical surfaces of hybrid Al/SiC/B4C metal matrix composites (MMCs) are finished by the MAFM process. One variable at a time (OVAT) approach is used for studying the effect of 6 input parameters, extrusion pressure (Ep), the number of cycles (N), abrasives concentration (C), workpiece material (Wp), abrasive mesh size (M), and magnetic flux density (Mf) upon response parameters, material removal rate (MRR) and change in surface roughness (ΔRa). The experimental results obtained for MRR and ΔRa show a significant improvement from 3.92 to 7.68 μg/s and 0.49 to 0.74 μm, respectively due to the increase of the extrusion pressure from 1 to 9 Mpa. The MRR and ΔRa was reduced from 6.89 to 6.78 μg/s and 0.46 to 0.22 μm, respectively with an increase in mesh number of abrasives from 80 to 400. The variation in concentration of abrasives from 40 to 60 % shows an improvement in MRR from 4.51 to 6.42 μg/s; whereas, there is a negligible effect on ΔRa which comes out from 3.82 to 3.86 μm. The MMCs, which are used for the experimentation shows a decline in MRR and ΔRa from 5.12 to 3.85 μg/s and 0.77 to 0.42 μm, respectively. This happened because there was a percentage change of reinforcement of SiC from 9 to 7 % and B4C from 1 to 3 % in Al-6063. An increase in the number of cycles from 50 to 250 shows a significant improvement in both MRR and ΔRa from 1.79 to 3.75 μg/s and 0.97 to 1.86 μm, respectively. Variation in magnetic effect also significantly improves MRR and ΔRa from 1.35 to 3.17 μg/s and 0.38 to 1.06 μm, respectively, when it is varied from 0.15 - 0.45 Tesla. The work carried out shows an overall significant improvement in MRR and ΔRa by using the MAFM process. The MAFM process finds a wide range of applications in finishing like surgical instruments, mechanical components, aerospace industry, electronics industry, etc. HIGHLIGHTS The hybrid MMCs (Al/SiC/B4C) are finished by novel MAFM setup An aluminium fixture and coil-type magnets play a significant role for finishing the workpiece surfaces An abrasive laden media acts as a cutting tool in the finishing process The OVAT approach is used for investigating the parametric effect The extrusion pressure, number of cycles and magnetic flux density are the significant parameters affecting the MRR and ΔRa GRAPHICAL ABSTRACT
Present work deals with the computation of static performance of partial journal bearing, operated with micropolar lubricant. The non-dimensional Reynolds equation governs the lubricant flow in clearance space and finite element method is used to solve it. Static characteristics including bearing load capacity, attitude angle, friction force, friction factor, and side flow are presented. Input parameters are chosen such as partial angles 120° and 180° and a width-diameter ratio (1.0), for a range of micropolar fluid parameters. The numerically simulated results show that the bearing geometry and lubricant micropolar parameters on higher side, provide an improved static performance of partial journal bearing system.
INTRODUCTIONMechanical seals are used in industrial pumps, compressors, and other applications, to provide a leak proof seal between the component parts. There are many different designs for mechanical seals, to meet specific applications. A mechanical seal [1] is a dynamic design with spring elements mounted in the dynamic (rotating) part of the seal system, or it can also be a stationary seal with spring elements mounted in the stationary part of the seal system, to compensate for misalignment of the shaft and seal.Mechanical face seals are used to seal a fluid at places where a rotating shaft enters an enclosure. A rotating seal is fixed to the shaft and rotates with it, whereas, a stationary seal is mounted on the housing. The secondary seals prevent leakage between the rotating shaft and the rotating seal, and also, between the housing and stationary seal, respectively. The rotating seal is flexibly mounted in order to accommodate angular misalignment and is pressed against the stationary seal by means of the fluid pressure and the spring. Primary sealing occurs at the sealing interface of both seal faces, where the rotating face slides relative to the stationary face. For proper functioning of a mechanical face seal, a fluid film is maintained between the faces. The sealed fluid may also act as a lubricant.The failure of the mechanical seals can be understood easily by identifying the various cause events that lead to their failure. Different cause events could initiate a general or specific failure mode. The reliability of mechanical seals can be increased by identifying failure occurrence and its propagation. A few cause events that are crucial can be minimized by appropriate actions at the design or fabrication stage. Structure [2] is the key to understand the failure of a system / components and its propagation. Structure or topology may be physical or abstract. Physical structure implies its components / assemblies and their connections, while an abstract structure involves failure contributing events or parameters and their interconnections or interdependences. A well-established approach, that is, the digraph model, suggested in graph theory [3,4], is used to represent structure (physical or abstract). A failure mode of mechanical seals can be conveniently represented in terms of a digraph model, which consists of nodes and directed edges. The digraph model for large systems is very complicated. To analyze the digraph model, a computer is used as a tool, and the analysis provides direction for the minimization of failure modes. The connection and reachability matrix approach is used to analyze the digraph model. Sehgal et al. [5,6] have applied this approach to analyze the failure of welded joints and the rolling element. This approach is extended to the failure mode analysis of mechanical seals, in this article.Mechanical seals are important to prevent leakage and entry of foreign particles into the system. Therefore, failure of mechanical seals can be hazardous to the system. Understanding the vari...
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