An investigation into tapping of Al6061/SiC metal matrix composite with straight flute HSS machine tap

The present study deals with tapping of Al6061/SiC metal matrix composite. Stir casting technique was used for the fabrication of composite. Castings were produced by varying weight percentages of SiC (5%, 7.5% and 10%) of 23μm size in Al6061. The tapping experiments were conducted for the machinability study of Al6061/SiC metal matrix composite using M8 x 1.25 HSS machine taps. The tapping operation was performed under dry condition with different cutting speeds. Torque required for tapping was measured using piezoelectric based 4-component drill tool dynamometer. Surface morphology and profile of thread surfaces were analysed using Scanning Electron Microscope (SEM) and metallurgical microscope. Estimation of progressive flank wear of machine taps was undertaken using profile projector. The performance of HSS machine tap was evaluated in terms of tapping torque, tool flank wear, and surface characteristics of thread surfaces. The flank wear of uncoated HSS machine tap increased with the increase in weight percentage of SiC in Al/SiC composite for a particular cutting speed. Further, when the matrix materials were reinforced by the same kind and the same weight percentage of SiC particles, the flank wear of the tool was found to increase with cutting speed. In addition, the damage caused to thread profiles increased with the increase in cutting speed and weight percentage of SiC

Machinability and surface integrity investigation during helical hole milling in AZ31 magnesium alloy

Conventional drilling has been widely used for making holes in structural materials. However, drawbacks like high cutting forces, poor surface finish, high cutting temperatures, excessive tool wear, and undesirable burr formation while drilling magnesium alloys have necessitated the development of alternative hole-making methods. Lately, the helical milling process has attracted interest in facilitating hole-making for assembly applications. However, the machinability of magnesium alloys using the helical milling process needs more investigation. Therefore, the presented work analyzed the influence of axial pitch, tangential feed, and spindle speed on cutting forces and surface integrity while milling AZ31 magnesium alloy. Axial feed was the most crucial factor contributing to the thrust force (71.8%), followed by tangential feed (13.2%). All three process variables impacted the radial force. Spindle speed was the most influential variable affecting the surface roughness (48.7%), followed by axial pitch (31.4%) and tangential feed (12.5%). Microhardness closer to the free surface of the hole was higher than the subsurface hardness. Moreover, microhardness showed an upward trend with the rise in axial pitch and tangential feed; however, it reduced with increased spindle speed

In-silico model development and validation of the L5-S1 spinal unit

AbstractThe L5-S1 segment of the spine is highly susceptible to injury, frequently causing low back pain. The segment has gained a lot of scientific interest, leading to many experimental works that can be found describing its biomechanical characteristics. But, there is a lack of work focusing on its computational studies, which can significantly aid its further studies. In the current study, a subject-specific single-segment finite element model of the L5-S1 unit was developed from a T2-mapped MRI scan. This study is mainly intended to probe the requirements for modelling the annulus of the disc and also attempts to understand the role of ligaments exclusive to the L5-S1 spinal unit to establish its validated finite element model. The annulus was represented by two different forms of hyperelastic material models (isotropic and anisotropic) for which the constants were determined from experimental data found in the literature. Their ability to impart the required characteristic was tested for the finite element model to mimic the experimental responses during sagittal and lateral moment loads. A comparison of results with the two material models is also discussed for other valuable parameters like contact pressure at the facets, maximum von-Mises stresses in the vertebrae, ligament strains, and midplane Tresca shear stresses of the annulus. The anisotropic Gasser-Ogden-Holzapfel (GOH) model was observed to deliver a response that consistently showed good compliance with the experimental response and hence, it is recommended for the computational studies of this segment