Optimization assisted Designing Mechanical Elements for Direct Metal Laser Sintering

Doctoral thesis (2019)

The common question that many mechanical engineers have tried to answer is “how to maximize strength and working reliability of parts during designs while being able to minimize the parts’ weights?” The ... [more ▼]

The common question that many mechanical engineers have tried to answer is “how to maximize strength and working reliability of parts during designs while being able to minimize the parts’ weights?” The associated solutions attach the design methods, which need to be de-veloped to build up the parts. The better solutions are the more reliable and lighter parts could be built up. Hence, the fewer negative impacts on the environment could be yielded and the closer distance we could step towards the more sustainable future. Under the influences of the Fourth Industrial Revolution, many optimization methods have been being developed, aimed at supporting engineers on figuring out the above question. Despite having substantial developments in recent years, both the optimization methods and its applications in the mechanical design field are still far from being fully exploited. To evaluate the potential use of the methods, specific product developments are essentially considered and investigated. The Thesis work particularly dealt with the investigations of the optimization assisted design methods, employed to develop structures of some mechanical elements. These constructed elements were expected to have higher performance than those traditionally designed and were able to be practically produced. For gradually studying and evaluating the processes of design, it was proposed to divide the work into the five separating phases. Within the initial phase, the first scheme of the optimization assisted design was theoretically investigated. Such a scheme was relied on the combination of topology optimization and lattice optimization and was considered in association with the redesigning process of a motorcycle frame. The frame was selected for this starting phase due to the convenient definition of the design volume subjected to the optimizations. By handling the investigations in dealing with (i) the first resonance frequency, (ii) the mass, (iii) the buckling load factor, and (iv) the equivalent stress of the newly designed frame and those of the original one, the potential use of the design approach was revealed. In addition, the investigations pointed out that further studies are essentially taken place to search for more appropriate ways to apply this approach to design novel complex structures. During the next three consecutive phases, the more complicate optimization schemes were proposed and studied. The schemes were composed of three optimization steps, including free shape optimization, topology optimization, as well as lattice optimization. The studies were handled in conjunction with the processes of innovating the hydrogen valve structure, which holds the unexposed design space. Different novel configurations were developed for the valve within these phases, targeting the reduction of mass, the prolongation of fatigue life, as well as the structural compatibility of the designed valves with DMLS. In addition, the design of a test channel for the valve performed via the use of a fatigue based approach was also introduced in one of the three phases. It was aimed at providing a mean to detect multiple early valve’s damages. All of the built structures were then virtually evaluated to point out the effectiveness of the design works. Within the last phase, experimental tests were proposed to carry out. In this phase, the best possible valve structure was selected and was subjected to produce by DMLS along with post-machining afterwards. Upon completion of the fabrications, the in-house fatigue tests were tak-en place for the produced valves until damages or reaching 2E5 cycles. The obtained data of the tests provided further evidence to support the theoretical studies demonstrated in the first four phases. [less ▲]