The purpose of the present paper is to investigate the effect of the second invariant of the deformation tensor on the axial and azimuthal shear deformation of an incompressible hyperelastic solid with various strain energy functions. To this end, the axial shear deformation of an incompressible cylinder with the modified Gent-Thomas, Gent-Thomas, Gent-Gent, and Carroll strain energies subjected to an axial shear traction is considered, where the displacement field is determined analytically for the first three models and numerically for the fourth model. The phenomenon of strain hardening at large elastic deformations, predicted either by the limiting chain extensibility condition for the modified Gent-Thomas and Gent-Gent models or phenomenologically by the Carroll model, is observed and it is shown that the second invariant of deformation increases the strain hardening experienced by such materials. Next, the azimuthal shear deformation of an incompressible annular wedge with the modified Gent-Thomas, Gent-Thomas, Gent-Gent, and Carroll models is considered, where the annular wedge is subjected to a controllable azimuthal shear deformation and the angular displacement is determined analytically for all the above models. Again, the second invariant of the deformation tensor is shown to have a significant effect on the azimuthal shear deformation as reflected in the increase of the strain hardening of the material in such deformation. In addition, the annular wedge with the modified Gent-Thomas and Carroll models is shown to have a higher resistance in azimuthal shear deformation than the other models mentioned above. پرونده مقاله

The design and manufacturing cubic porous scaffolds are a considerable notion in tissue engineering (TE). From Additive manufacturing (AM) perspective, it has attained high appeal in the string of TE during the past decade. In the view of TE, the feasibility of manufacturing intricate porous scaffolds with high accuracy contrast to prominent producing methods has caused AM the outstanding option for manufacturing scaffold. From design perspective, porous scaffold structures play a crucial task in TE as scaffold design with an adequate geometries provide a route to required strength and porosity. The target of this paper is achieve of best geometry to become an optimum mechanical strength and porosity of TE scaffolds. Hence, the cubic geometry has been chosen for scaffold and Cube, Cylinder and Hexagonal prism geometries have been selected for pore of structures. In addition, for noticing the porosity effects, pore size has been chosen in three size, and a whole of nine scaffolds have been designed. Designed scaffolds were generated using Fused Deposition Modeling (FDM) 3D Printer and dimensional specifications of scaffolds were evaluated by comparing the designed scaffolds with Scanning Electron Microscope (SEM). The samples were subjected to mechanical compression test and the results were verified with the Finite Element Analysis (FEA). The results showed that firstly, as the porosity increases, the compressive strength and modulus of elasticity obviously decreased in all geometry pore scaffolds. Secondly, as the geometry changes in similar porosity, cubic pore scaffold achieved higher compressive strength and modulus of elasticity than cylinder and hexagonal prime. Experimental and FEM validated results proposed a privileged feasible pore geometry of cubic scaffold to be used in design and manufacturing of TE scaffolds. پرونده مقاله

Parallel Tubular Channel Angular Pressing (PTCAP), as a process of Severe Plastic Deformation (SPD), was employed for improving the strength of commercially pure Titanium (Grade 2). In the present research, the tubular samples of pure titanium were severely deformed by one and two passes of PTCAP at the temperature of 450°C. It was found by the results of tensile tests that the yield and ultimate strengths increased by 24% and 29% after applying the second pass of PTCAP, respectively. It was also showed that the Vickers microhardness increased by 46%. Moreover, the micrographs illustrated that the average grain size decreased from ∼21 μm in the unprocessed condition to ∼143 nm after applying two PTCAP passes. Therefore, applying the technique of PTCAP was successful to produce the nano-structured titanium. پرونده مقاله

The neck fractures and the femurs intertrochanteric are common complications that are recovered by a multicomponent implant called dynamic hip screw (DHS). In the present study, a standard four-hole DHS with Ti6Al4V (Ti6) and SS316l (SS) alloys for static mode (slow walking) and fatigue mode like normal walking (NW), descending stairs (DS), and falling (FA) by finite elements analysis (FEA) have been evaluated (ANSYS software). The results have been confirmed by similar studies in static mode and maximum Von Mises stress and strain are obtained for Ti6 about 145MPa and 0.191%, and SS about 196 MPa and 0.121%. Most critical stress points occur in cortical screws, plate holes, compression screws, and lag screws, respectively. DHS components with Ti6 alloy have infinite life in NW and DS, also in FA, they have a finite life (107-108 cycle) with alternating Von Mises stress () ~ 425 MPa, while for SS they have finite life in all activities, which NW ~107 cycle, DS~106 cycle,and even in FA cortical screw life of failure reaches to 98 cycles and . The critical regions are the same as the failure regions common in biomechanical and clinical studies. These regions are mainly concentration stress points that lead to DHS failure as the crack grows. پرونده مقاله

The increase in materials with high mechanical capabilities has increased the number of advanced production methods. One of these methods is the merging of ultrasonic vibrations with conventional machining methods. The milling process is flexible in making different geometric shapes of the workpiece. In this paper, the longitudinal vibrations assisted milling process is studied. The main problem with this process is the transmission of ultrasonic vibrations to the cutting area. Therefore, different transfer methods were studied and analyzed and the most efficient method was presented. Longitudinal vibration equations for the horn were analyzed and different types of horns were designed. The best horn was identified and fabricated in terms of increased vibration amplitude and less stress. It was shown that the 5-element horn is the best option for vibration transmission. In order to transfer electrical energy to the rotary ultrasonic converter, a new tool was designed and manufactured. By machining thin-walled parts, it was shown that the fabricated tool can create appropriate dimensional accuracy in the workpiece. پرونده مقاله