Degree Type

Dissertation

Date of Award

2016

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

Major

Mechanical Engineering

First Advisor

Christian J. Schwartz

Abstract

Science, Technology, Engineering and Mathematics (STEM) disciplines are challenging to blind and visually impaired (BVI) individuals. One of the possible reasons is the complexity in representing and understanding scientific content. Introducing tactile elements such as textures into existing Braille characters can potentially increase the information content of Braille and could likely simplify the complex notations. However, such a task requires a thorough understanding of the discrimination of textures through touch. The current dissertation focuses on: 1) Investigating the psychophysical factors involved in texture discrimination and, 2) Developing a testing system to assess friction induced skin damage from repetitive motion over textured surfaces.

The tactile discrimination sensitivity for six fine textured non-patterned surfaces (fine-grit abrasive papers) was evaluated using a two-alternative forced choice technique. The surface roughness parameters and the coefficient of friction of the abrasive papers interacting with human skin were measured. Scanning electron microscopy images were used to observe the surface microstructure. The results suggest that differences in the mean spacing and the friction coefficients could be indicative of differentiability of fine textured samples. Three clearly differentiable textures identified from this study were used to investigate the effect of texture area on tactile discrimination sensitivity. A perception measurement experiment in combination with a friction measurement experiment was performed to understand the possible role of friction in touch-based texture discrimination. There was decrease in the discrimination ability with the decrease in the texture area.

An elastomeric skin simulant with layered structure similar to that of human skin was constructed to replicate skin friction blisters. The relationship between applied normal load and number of cycles of reciprocating motion required for blistering was studied. Additionally, a crack-growth model was developed treating the skin simulant as an adhesive-bonded laminar composite. This study made it evident that complete profile of the tribological system is required to develop a skin simulant that can accurately predict skin friction damage. Based on the current literature, the role of surface topography and elastic properties of the human skin on friction was uncertain. Coefficient of friction of four probing surfaces, human index finger pad, silicone replicas of the finger with and without fingerprints, and a smooth silicone sphere, when sliding against fine grit abrasive papers were compared to identify these roles.

Copyright Owner

Geetha Pravallika Chimata

Language

en

File Format

application/pdf

File Size

114 pages

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