Design considerations for light weight mechanical parts

Student thesis: Doctoral Thesis

Abstract

Context and Background - Lightweight design is important for many engineering fields due to the increased energy efficiency and process performance that it can result in. Functionally graded materials (FGMs) give a key contribution to lightweight design when low mass along with a gradual change in a second primary constraint is required such as alleviation of a large temperature gradient. With the evolution of additive manufacturing (AM), FGM use for light weighting is rising in practicality. Therefore, research into combining FGMs with AM is required, and should include topics relevant to these, including form, material choice and structural design. The work is tested on robotic arm links due to the ever-increasing adoption of automation, and the practical accessibility of them for the researcher. Aim of Research - The aim of the research is to investigate the mass reduction of robotic arm links by merging second moment of area calculations, structured cells, topology optimisation, functionally graded materials and additive manufacture in various combinations. Key Work - The main output of this work is a set of design guidelines that have been written to assist engineers with combining FGMs, topology optimisation, structured cells and high-level AM restrictions. Within the field of lightweight design, the guidelines are use-case agnostic. The design guidelines have been trialled using test cases, each aimed at individual elements of the guidelines. The objective of the first test case is to discover if FGMs will reduce stresses in parts constructed of dissimilar materials when used in conjunction with high-level AM constraints. The second test case trails the various computational testing sections required in the guidelines, including part sectioning rules and material distribution techniques. The third test case incorporates heat ow simulation during AM deposition of the FGMs, including the three heat transfer mechanisms and interaction with the print bed of AM hardware. The final test case assesses the entirety of the design guidelines, re-examining the aspects tested in the second and third test cases, together with a technique to decide whether structured cells or topology optimisation should be used based on the use case of the part, and a first pass at inspecting the residual stresses in the additively manufactured part once it has cooled. Conclusions - Overall, the use of FGMs along with lightweight structural design techniques and high-level AM restrictions are computationally successful at reducing the mass in robotic arm links. While the design guidelines are use case agnostic, they make most sense used in fields of engineering that have a substantial requirement for light weight design, such as aerospace and space. Ideally, physical testing would have been used to increase validity of the design guidelines. Unfortunately, funds were not available, and thus physical testing is deemed the next step for this work in the future.
Date of Award23 Aug 2021
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council)
SupervisorXiu Yan (Supervisor) & William Ion (Supervisor)

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