Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Matthew Priddy

Committee Member

Yucheng Liu

Committee Member

Tonya Stone

Committee Member

Ben Campbell

Date of Degree

8-6-2021

Original embargo terms

Visible to MSU only for 2 years

Document Type

Dissertation - Campus Access Only

Major

Mechanical Engineering

Degree Name

Doctor of Philosophy

College

James Worth Bagley College of Engineering

Department

Department of Mechanical Engineering

Abstract

Thermoplastic welding utilizes a fiber laser to join samples that are clamped together. Laser energy is transferred through the natural sample to the interface with the opaque sample where heat energy creates a weld through conduction and radiation heat transfer modes. The overall goal of this research is to understand the effect of heat source loading on PA6 and PA66 thermoplastic materials from laser through transmission welding that is used to join natural and opaque materials. The welding process is studied through a combination of finite element simulation, experimentation, and design of experiment modeling. The results of temperature profile and melt properties of the material are compared with weld strength and quality to provide welds used in a range of applications from the automotive industry to hermetically sealed medical components. Research of heat source models is used to determine the best representation of the laser energy for laser through transmission welding of thermoplastic materials. The comprehensive objective is to find the best fit of laser parameters to PA6 and PA66 material samples to predict weld quality in the through transmission laser welding process. Results of the research include temperature profile behavior for surface exposure and single pass weld tests, and thermal conductivity verification of PA6 and PA66 through experimentation. Finite element simulations of the experiments provide analysis of temperature dependent properties and time dependent analysis of the laser heat source loading. The Gaussian surface model with penetration variable is determined to be the best representation of the laser through transmission welding of thermoplastic material after completing heat source literature review and analysis. Finally, surface response methods were used to find the most influential parameters in laser through transmission welding, which were the number of laser passes and laser power for PA6 and PA66 materials.

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