Ultrafine-grained pure titanium is characterized by its exceptional mechanical properties, among which high ultimate strength and high yield value are of utmost importance. Equal channel angular pressing (ECAP) and ECAP+cold extrusion (CE) have been used to process ultrafine-grained pure titanium.

Though many aspect studies on the mechanical deformation behavior of ultrafine-grained (UFG) pure titanium have been carried out, there is little study on systematic qualitative and quantitative characterizations on the temperature-dependent deformation and fracture features of pure titanium processed by ECAP and CE.

The study on the temperature-dependent deformation and fracture features of ultrafine-grained materials is of great interest because of their limited application temperature.

Yun Jong Guk, a section head at the Faculty of Mechanical Science and Technology, investigated the tensile deformation and damage behavior and microstructures of ultrafine-grained (UFG) pure titanium processed by ECAP and ECAP+CE at different temperatures, and carried out quantitative fractal analyses of deformation and damage morphologies by the yard-stick method based on Mathematica.

The results show that as the temperature increases, the diameter and depth of dimples on the fracture surfaces of ultrafine-grained pure titanium increase significantly with corresponding increase in the fractal dimensions. The microstructure observation results of the tensile deformation show that the dislocation density decreases significantly with increasing temperature and the grain boundaries become clear.

For more information, please refer to his paper “Temperature-Dependent Tensile Deformation and Fracture Features of Commercially Pure Ti Processed by ECAP and Cold Extrusion” in “Proceedings of KUTIC-2025”.

Coal processing is the most effective method for removing unwanted minerals and pollutants from coal, and there are several techniques for it including physical, chemical and physicochemical separation.

Among various physical separation methods, the selective crushing separation is a promising method for reducing specific energy consumption during the early stages of classification and for treating low-grade ores and tailings disposal.

Currently, toothed roll crushers are commonly used in various stages of mineral processing. The toothed roll crushers can be designed to be with either a single toothed roll or a double toothed roll.

The selective crushing device with hanging rings and a toothed roll is a kind of a single toothed roll crusher in which many hanging rings are supported by the supporting structure including a beam and a supporting rod. The supporting structure for hanging rings not only stands the weight of the rings and the dynamic loads during crushing processes but also constricts the freedom degree of the rings. The supporting structure may have a great influence on the crushing performance of this selective crushing device.

Jon Chol Min, a researcher at the Faculty of Mining Engineering, has proposed a new type of toothed roll based selective crushing device, and investigated the effect of the supporting structure to improve the crushing performance of the device.

The analytical result of the interaction of hanging rings and feed particles shows that the placement of the supporting rod has the greatest influence on the interaction force, and that the placement angle of the supporting rod for hanging rings is a critical design parameter for the improvement of crushing performance of the selective crushing device.

Capacitive pressure sensors have been widely studied and applied for their advantages such as high measurement sensitivity, wide pressure measurement range, low power consumption, robust structure, high overload characteristics, low fabrication cost, etc. The research on capacitive pressure sensors mainly focuses on improving the linearity of output characteristics and sensitivity. With this increasing research, touch mode capacitive pressure sensors (TMCPS) have been developed with better sensitivity and linearity than conventional planar electrodes.

The existing TMCPSs have constant touch point pressure (TPP) of different values. These TMCPSs operate in normal mode between zero pressure and TPP when external pressure is applied. The TPP of TMCPS has a direct effect on the effective operating pressure range, sensitivity and linearity of the device.

Rim Chang Sik, a researcher at the Institute of Semiconductor, has proposed a new structure of TMCPS with a spherical substrate electrode with TPP near zero, and investigated its characteristics.

The proposed TMCPS consists of an elastic diaphragm-top moving electrode that causes deformation under external pressure, and a curved bottom fixed electrode. The two electrodes are in touch before the external pressure is applied, and when the external pressure is applied, the upper moving diaphragm acts as a touch type, wrapping the bottom surface electrode from the beginning.

As the TTP of this device is near zero, it has a wider range of effective operating pressure, and its curved bottom surface provides better sensitivity and linearity than a planar CPS.