Yabin Yang

Wireless millirobots engineered to infiltrate intricate vascular networks within living organisms, particularly within constricted and confined spaces, hol

Residual stresses and deformations are one of the challenges needs to solve for metal additive manufacturing part. Finite element method plays an important role in predicting the residual stresses and deformations to reduce the experimental costs, and provides a powerful tool for the optimization of process parameters and scanning strategies of heat source. However, the key problem in simulation is the mismatch between the melt pool and the built part in both spatial and temporal scale. This would result in large discretization in both spatial and temporal domains in the simulation, which gives rise to huge computational cost. Therefore, it is necessary to develop a computationally efficient and accurate model in predicting the residual stresses and deformations of the metal additive manufacturing part. A thermosmechanical model based on a superposition law in the thermal calculation is proposed in the present study. The proposed model enables to solve the mismatch of spatial scale in metal additive manufacturing. The proposed model is employed to predict the residual stresses and deformations in many metal additive manufacturing process, such as the selective laser melting and wire and arc additive manufacturing. The proposed model shows attractively high computational efficiency, and the accuracy of the proposed model is also validated by the experiment.

The electrochemical additive manufacturing technique based on the meniscus-confined approach has been proved to be a powerful tool for fabricating nanoscale and microscale metal components. The stability of the meniscus is the key in this meniscus-confined approach to achieve high resolution and reliable product quality. In the present study, a double-nozzles design, which consists of a feed nozzle and a suction nozzle, is proposed for the meniscus confined electrochemical additive manufacturing technique. It was demonstrated that the proposed design possessed robust control of the stability of the meniscus by manipulating the feed and suction rates of the two nozzles in a quite large range. Various sizes of menisci can be easily obtained by utilising nozzles with different sizes. Compared with the pressure-controlled single-nozzle approach, the results showed that dense structures without dendrites can be fabricated by the double-nozzles design with larger current density due to the feed-and-suction process at the tip of the nozzles. The proposed flow-rate-controlled double-nozzles design was finally employed to fabricate some copper circuits and a Cu/CuNi thin film thermocouple to demonstrate its potential in fabricating electronic devices.

In additive manufacturing of metallic materials, an accurate description of the thermal histories of the built part is important for further analysis of the distortions and residual stresses, which is a big issue for additively manufactured metal products. In the present paper, a computationally volumetric heat source model based on a semianalytical thermal modeling approach is proposed. The proposed model is applied to model the thermal response during a selective laser melting (SLM) process. The interaction between the laser and the material is described using a moving volumetric heat source. High computational efficiency can be achieved with considerable accuracy. Several case studies are conducted to examine the accuracy of the proposed model. By comparing with the experimentally measured melt-pool dimensions, it is found that the error between the predictions obtained by the proposed model and the experimental results can be controlled to less than 10%. High computational efficiency can also be achieved for the proposed model. It is shown that for simulating the thermal process of scanning a single layer with the dimension of 2 mm × 2 mm, the calculation can be finished in around 110 s.