In Hopkinson bar theory, stress, strain, and strain rate can be determined by analyzing the dimensions of the specimen. When conducting Split-Hopkinson Pressure Bar (SHPB) experiments, the stress-strain curve is obtained by considering the entire length and width of the specimen. However, in Split-Hopkinson Tensile Bar (SHTB) experiments, it is important to only consider the regions where deformation occurs in order to accurately determine the dynamic material properties. This study introduces a method for selecting the dimensions of the deformed region (LD and WD) in plate specimens for SHTB experiments using Finite Element Analysis (FEA). The analysis involved varying the length and width of a 1 mm thick SUS430 specimen, and the deformed region was determined using the proposed method. The stress-strain curves obtained from this region were then compared with the input Cowper-Symonds model. The validity of the proposed approach was confirmed, as the percentage error between them ranged from 2.54 to 6.62%.

In this study, we present the multilayered symmetrical droplet splitting microfluidic system for preparation of microspheres. The microfluidic device was fabricated by conventional photolithography and PDMS casting. Multiple layers of microfluidic channels for symmetrical droplet splitting were stacked and integrated into a device. Each layer was designed to obtain 16 microdroplets from one droplet by droplet splitting. The droplet size was controlled with flow rate of dispersed phase (DI-water) and continuous phase (Mineral Oil with 3 wt.% SPAN80) by using a syringe pump. The droplet splitting behavior and production rate were analyzed by high-speed camera and inverted microscope in one layer of the microfluidic device. Additionally, the droplet size and size distribution were observed in each layer of the microfluidic device. The droplet size could be controlled by flow control of two phase flows with high uniformity of droplet size less than 5% coefficient of variation.

Finite element analysis was performed for a split-type CFRP bicycle frame, which was designed to apply a compression molding process with carbon fiber prepreg for a conventional bicycle. An epoxy adhesive material for joining the frames was selected by the extent of stress at joint interfaces. The split-type bicycle frame was then formed and its weak parts examined by the boundary conditions according to reliability tests. The results verified the reliability of the bicycle frame after modification of these weak parts. The finished product was manufactured by using this developed split-type bicycle frame.