In this study, thin-shell surface observation, storage capability test, and micro-compressive test were performed for self-healing microcapsules using a field emission scanning electron microscope (FE-SEM) and a micro-compressive testing machine. A microcapsule having a melamine-urea-formaldehyde thin-shell and a microcapsule having a melamine-urea-formaldehyde thin-shell reinforced with carbon nanotubes were used. Two carbon nanotube contents were considered: 0.17 wt% and 0.50 wt%. Thin-wall shell state was relatively smooth when microcapsules were not reinforced with carbon nanotubes. It was uneven when microcapsules were reinforced with carbon nanotubes. Prepared microcapsules showed little decreases of weights even when the exposure time was increased regardless of whether they were reinforced with carbon nanotubes. Thus, their storage capability was good. When carbon nanotube content was the same, the fracture load was almost constant without being affected by the diameter of the microcapsule. However, fracture displacement increased with increasing diameter of the microcapsule. When diameters of microcapsules were similar, fracture load and fracture displacement increased when carbon nanotube content increased. It was found that self-healing microcapsules had good storage capability and mechanical properties. Thus, they could be applied to repair damage to composite materials if thin-shell formation mechanism for adding carbon nanotubes is supplemented.

Gerotor oil pumps are widely used for the lubrication oil of an engine and the hydraulic source of an automatic transmission. Recently, improvements for the purposes of fuel efficiency and noise reduction have come to the forefront of the automobile industry, and it has become necessary to study the design of gerotors and ports. In this study, an expanded cardioid curve was developed, and an equation for a tooth profile with an expanded cardioid lobe shape has been suggested to reduce pump noise. The design was created using an automatic program; the program generated inner and outer rotor profiles and calculated performance parameters. Also, in order to decrease irregularity, CFD analyses were performed according to groove shapes in the exhaust port. Results showed the noise of the improved oil pump (the suggested gerotor [expanded cardioid] + the proposed port) was 5.44% lower than the existing oil pump (the existing gerotor [2-ellipse] + basic port).

In this paper, we compared the performance of the mechanical inertia and electronic inertia used in the friction coefficient measurement process, as this is the main function of the braking performance tester. The comparative test was carried out 36 times under mechanical inertia and electronic inertia. Stop braking was performed at various braking speeds (120, 160, 200, 220 ㎞/h), and at various contact force conditions (8, 18, 25 kN). We compared the instantaneous coefficient of the friction, the average coefficient of the friction, the braking force, and the braking distance with the mechanical inertia and the electronic inertia, by taking the average of the three tests we performed each for braking velocity and contact force. In addition, the friction coefficient ratio and the energy ratio were calculated. As a result, it was confirmed that the test using the electronic inertia compared to the test using the mechanical inertia appropriately reflects the bearing frictional force and the rotational resistance loss of the tester, and the kinetic energy is consumed as the braking energy without loss.