A Novel Framework of Developing a Predictive Model for Powder Bed Fusion Process.

The powder bed fusion (PBF) process is a metal additive manufacturing process, which can build parts with any complexity from a wide range of metallic materials. PBF process research has predominantly focused on the impact of only a few parameters on product properties due to the lack of a systematic approach for predictive modeling of a large set of process parameters simultaneously. The pivotal challenges regarding this process require a quantitative approach for mapping the material properties and process parameters onto the ultimate quality; this will then enable the optimization of those parameters. In this study, we propose a two-phase framework for studying the process parameters and developing a predictive model for 316L stainless steel material. We also discuss the correlation between process parameters that is, laser specifications and mechanical properties, and how to obtain an optimum range of volumetric energy density for producing parts with high density (>99%), as well as better ultimate mechanical properties. In this article, we introduce and test an innovative approach for developing AM predictive models, with a relatively low error percentage (i.e., around 10%), which are used for process parameter selection in accordance with user or manufacturer part performance requirements. These models are based on techniques such as support vector regression, random forest regression, and neural network. It is shown that the intelligent selection of process parameters using these models can achieve a high density of up to 99.31% with uniform microstructure, which improves hardness, impact strength, and other mechanical properties.

Effect of high-power ultrasonic vibration on the flexible bending process of thin-walled circular tubes: Numerical and experimental research.

Thin-walled bent tubes are a significant component utilized in the aerospace, shipbuilding, and chemical industries, as well as considering that they are employed as fluid and gas transporters, the quality of their manufacturing and production is critical. In recent years, new technologies for the manufacture of these structures have been developed, the most promising of which is the flexible bending process. Nevertheless, during tube bending, defects like an increase in contact stress and friction force in the bending area, thinning of the bent tube in the extrados zone, ovalization, and spring-back are some of the issues that arise. So, based on the softening and surface effects induced by ultrasonic energy in metal forming, this paper is suggested a novel method to fabricate the bent components by adding ultrasonic vibrations into the static motion of the tube. Therefore, experimental tests and finite element (FE) simulations are employed to assess the impact of ultrasonic vibrations on the forming quality of the bent tubes. Initially, an experimental setup was designed and built to guarantee the transmission of ultrasonic vibrations with a frequency of 20 kHz to the bending area. Afterward, based on the experimental test and its geometrical parameters, a 3D finite element model of the ultrasonic-assisted flexible bending (UAFB) process was developed and validated. According to the findings, forming forces were significantly reduced when the ultrasonic energy was superimposed, and thickness distribution in the extrados zone was significantly enhanced as a result of the acoustoplastic effect. In the meantime, the UV field's application effectively diminishes the contact stress between the bending die and tube, as well as greatly reduces the material flow stress. In the end, it was found that applying UV at the appropriate vibration amplitude can effectively improve ovalization and spring-back. The current study will assist researchers in better understanding the role of ultrasonic vibrations in performing the flexible bending process and achieving improved tube formability.

Observation on the behavior of ultrasonic micro-hammer and its effects on the deep drawing process: Numerical simulation and experimental study.

Combining ultrasonic vibration (UV) with metal forming processes is investigated as a novel technology that has been able to reduce the forming force and enhance this process. This paper attempts to elucidate the effect of Ultrasonically Assisted Deep Drawing (UADD) process on the forming force and thickness distribution of the formed sample. Therefore, a Finite Element (FE) model is developed to simulate this process and further investigate the ultrasonic micro-hammer mechanism in UADD process. Experimental tests were conducted to validate the established numerical model. Accordingly, a robust technological equipment was designed and fabricated, so that by application of ultrasonic vibration, the drawing die will be stimulated in longitudinal mode at the frequency of 20 kHz and thus, remain in the resonant condition. A reasonable congruence was observed when the forming force results and cup configurations from experimental tests and numerical solutions were compared. Therefore, the numerical model was used to evaluate the deformation behavior of the sheet at different amplitudes and frequencies. The results confirmed continuous vibration and ultrasonic micro-hammer conditions exhibit different behavior during the UADD process, and the latter occurs when the ultrasonic die separates from the workpiece surface. Although the UV application under micro-hammer condition significantly reduces the forming force, it has a destructive effect on the thickness distribution of the sheet and causes severe thinning. The current study provides a better understanding of the ultrasonic micro-hammer and its effects on the sheet metal forming process, which is the fundamental step in exploring this process.