Search results

This study aims to enhance hygiene and structural performance in additively manufactured (AM) below-knee prosthetic sockets by optimizing ventilation and structural integrity through advanced design methodologies, including topology optimization (TO) and design for additive manufacturing (DfAM).

A transtibial prosthetic socket was digitally modeled from image data of the residual limb of an amputee and fabricated using acrylonitrile butadiene styrene (ABS) material using fused deposition modeling. TO and DfAM rules were applied to achieve the multi-objective design of ventilation, weight reduction and structural integrity by introducing geometric discontinuities. The level of this achievement was evaluated through finite element analysis (FEA) and mechanical testing using a novel lobe bending test.

This study found that TO significantly reduced stress concentrations and improved the strength-to-weight ratio of the socket. Mechanical testing revealed a critical failure load of 918.5 N, validated by FEA, which indicated peak stresses of 37.91 MPa. A 5 mm thick socket with circular discontinuities demonstrated enhanced ventilation and mechanical resilience.

The focus on ABS material and specific socket designs may limit the generalizability of findings to other materials and designs.

The optimized socket design provides a cost-effective, high-performance solution for improving comfort and durability in below-knee prosthetic sockets within AM applications.

This research introduces innovative testing methods, including the lobe bending test and uses advanced optimization techniques, addressing challenges in ventilation and mechanical performance. The insights gained are valuable for future prosthetic socket design advancements.

To study the nature of scuffing in boundary lubricated sliding contacts with subsurface plastic deformation, as it occurs in plastic deformation processing.

Low speed oblique plastic impact testing (LOSOPIT) has been conducted on copper specimen with a hard En31 ball in a test rig that has facility to measure the coefficient of friction. Based on the findings of friction coefficient in these experiments, friction power has been estimated and was found to be in the typical range. Scuffing studies were undertaken both by observation of the slid surface of En31 sphere in a ferrographic microscope with camera facility as well as by calculation of the friction power.

The boundary lubricant was found to have profound role in safeguarding the surface from severe deformation and micro‐cracks. Scanning electron microscope (SEM) examination of the craters produced by LOSOPIT has given evidence that using the boundary lubricant resulted in smooth transfer of shear stress from the sphere to the specimen surface through the boundary lubricant layer. Owing to this, the asperities have been found flattened in a smooth manner instead of metal at the surface being scuffed. A limited amount of reduction was found in the coefficient of friction due to the use of boundary lubricant from that in the dry testing.

The model used to estimate the friction power is predominantly governed by the friction coefficient itself rather than either the normal load or the sliding speed. Friction coefficient itself may be contributed by various mechanisms all of which may not equally contribute to scuffing. Study is underway to carefully glean out those components of friction that exactly result in scuffing, and to use more effective criteria for scuffing.

The knowledge and data developed in the paper give a clear explanation of conditions under which scuffing can take place in sliding contacts operating under boundary regime. The most important applications are metalforming and metal cutting. It is relevant to mechanical engineering machinery in which intense contact pressures are expected.

This paper fills the gap of lack of scuffing studies in plastic deformation processing. All earlier studies focused on elastic conditions prevailing at the contact. Since, industry has been witnessing a need to tackle the severe problems related to formed product quality and certain defects hitherto unexplained, this paper gives a new direction to explain the defects in products from scuffing point of view. In this paper, it has been shown that friction power can be a good criterion to represent scuffing intensity in boundary lubrication.

The aim of this paper is to predict the optimum settings of the process parameters for selective laser sintering process.

A simulation model is prepared using author written subroutines in ANSYS^® Parametric Design Language (APDL™) environment. The simulation model is then run at the experimentally designed points using central composite design approach. Based on the observations, a response surface is generated for the density of a sintered part as a function of various process parameters.

The results indicate the optimum settings of the process variables to achieve a desired value of the density.

The developed simulation model can be used to predict the density of the final part with limited part geometries and may not be applicable for the complex shapes or with irregular features.

The parameter settings as predicted by the simulation model may not be reproduced exactly by the experimental readings.

The results of the simulation study concur with previous investigation by other researchers. Hence, the model can be suitably modified according to available data for different materials (amorphous and crystalline) taking the due considerations.

The purpose of this paper is to investigate the transient three‐dimensional temperature distribution for a laser sintered duraform fine polyamide part by a moving Gaussian laser beam. The primary objective of the present paper is to develop computationally efficient numerical simulation technique with the commercially available finite element software domain for the accurate prediction of the temperature history and heat‐affected zones of the laser sintered parts so as to finally obtain the density of the sintered sample.

The paper proposes a mathematical model of scanning by moving laser beam and sintering sub‐model. Based on the mathematical models, a simulation model was developed by using author written subroutines in ANSYS® 11.0, a general purpose finite element software. The simulation model was then run at experimental designed points using two‐level factorial design of experiments (DOE) approach. The data thus generated were used to predict the equation for the density of sintered part in terms of process parameters using Design Expert software in order to analyse the designed experiments.

Laser power and scan spacing were found to be significant parameters affecting the part density. Amongst the interaction terms, significant effect of laser power was found on the part density at the lower settings of the scan velocity. Temperature‐time plots were generated to study the transient temperature distribution for the sintering process and with further applicability to study the thermal stresses.

The simulation model hence developed can be used for only simple part geometries and cannot be generalised for any complex geometry.

The paper presents a simulation model which is integrated with a DOE approach so as to develop a robust as well as simple and fast approach for the optimization of quality objective.