Purpose Selective laser melting (SLM) enables the fabrication of lightweight and complex metallic structures. Support structures are required in the SLM process to successfully produce parts. Supports are typically lattice structures, which cost much time and material to manufacture. Besides, the manufacturability of these supports is undesirable, which may impact the quality of parts or even fail the process. The purpose of this paper is to investigate the efficiency and mechanical properties of advanced internal branch support structures for SLM. Design/methodology/approach The theoretic weight of a branch support and a lattice support of the same plane were calculated and compared. A group of standard candidates of branch support structures were manufactured by SLM. The weight and scanning time of specimens with different design parameters were compared. Then, these samples were tested using an MTS Insight 30 compression testing machine to study the influence of different support parameters on mechanical strength of the support structures. Findings The results show that branch type supports can save material, energy and time used needed for their construction. The yield strength of the branch increases with the branch diameter and inclined branch angle in general. Furthermore, branch supports have a higher strength than traditional lattice supports. Originality/value To the best of the authors’ knowledge, this is the first work investigating production efficiency and mechanical properties of branch support structures for SLM. The findings in this work are valuable for development of advanced optimal designs of efficient support structures for SLM process.
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This paper proposes a microstructure, the flexible unit, employing the leaf spring working principle in machinery. The flexible unit has elasticity and damping capability. Parts using flexible units produce greater elastic deformation than rigid parts under great impact external loads, thus absorbing and consuming large energy amounts during deformation. First, the flexible unit’s structural form and layout designs are presented. Second, the constraint conditions for the flexible unit’s structural parameters are given according to selective laser melting process characteristics. Third, flexible units with different parameters are selected and produced using selective laser melting. The influences of the flexible unit’s structural parameters on the mechanical properties and energy absorption are then analyzed from compression test results. Finally, the strength and energy absorption of the common Kagome structure and the flexible unit are compared. The results show that the flexible unit’s yield strength is ~36% higher than a Kagome structure with the same mass. The flexible unit’s absorbed energy is ~27% higher when damaged and ~39% higher during elastic deformation than for the Kagome structure. Thus, flexible units have demonstrably excellent performance, so their design and application provide an alternative for the lightweight and miniaturized design of parts with large impact loads.
Abstract:The structural optimization of the internal structure of parts based on three-dimensional (3D) printing has been recognized as being important in the field of mechanical design. The purpose of this paper is to present a creation of a unit structure-performance database based on the selective laser melting (SLM), which contains various structural units with different functions and records their structure and performance characteristics so that we can optimize the internal structure of parts directly, according to the database. The method of creating the unit structure-performance database was introduced in this paper and several structural units of the unit structure-performance database were introduced. The bow structure unit was used to show how to create the structure-performance database of the unit as an example. Some samples of the bow structure unit were designed and manufactured by SLM. These samples were tested in the WDW-100 compression testing machine to obtain their performance characteristics. After this, the paper collected all data regarding unit structure parameters, weight, performance characteristics, and other data; and, established a complete set of data from the bow structure unit for the unit structure-performance database. Furthermore, an aircraft part was reconstructed conveniently to be more lightweight according to the unit structure-performance database. Its weight was reduced by 36.8% when compared with the original structure, while the strength far exceeded the requirements.
Reviews and experimental verification have found that existing solution methods can be used to solve UAV path planning problems, but each approximate solution has its own advantages and disadvantages. For example, ant colony algorithm easily falls into the local optimum in the process of realizing path planning. In order to prevent too low pheromones on the longer path and too high pheromones in the shorter path, the upper and lower limits of pheromones as well as their volatile factors are set to avoid falling into the local optimum. Secondly, multi-heuristic factors are introduced, and the overall length of the path serves as an adaptive heuristic function factor that determines the probability of state transition, which affects the probability of ants choosing the corresponding path. The experimental results show that the path length planned by the improved algorithm is 93.6% of the original algorithm, and the optimal path length variance is only 14.22% of the original algorithm. The improved ant colony algorithm shortens the optimal path length and solves the UAV path planning problem in terms of local optima. At the same time, multiple enlightening factors are introduced to increase the suitability of UAV for complex environments and improve the performance of UAV.
By conducting static strength analysis, fatigue life prediction, strain history acquisition and time correlated damage analysis under the FE simulation circumstance, the deducted load spectrum for accelerated fatigue bench test of a special construction vehicle driving axle housing was acquired.The result of bench test shows that the deducted load spectrum can significantly reduce the test period when accurately preserve damage that the part suffering.
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