Thermal management is a critical issue for the development of high-performance electronic devices. In this paper, thermal conductivity values of mild steel and stainless steel(STS) are measured by light flash analysis(LFA) and dynamic thermal interface material(DynTIM) Tester. The shapes of samples for thermal property measurement are disc type with a diameter of 12.6 mm. For samples with different thickness, the thermal diffusivity and thermal conductivity are measured by LFA. For identical samples, the thermal resistance(Rth) and thermal conductivity are measured using a DynTIM Tester. The thermal conductivity of samples with different thicknesses, measured by LFA, show similar values in a range of 5 %. However, the thermal conductivity of samples measured by DynTIM Tester show widely scattered values according to the application of thermal grease. When we use the thermal grease to remove air gaps, the thermal conductivity of samples measured by DynTIM Tester is larger than that measured by LFA. But, when we did not use thermal grease, the thermal conductivity of samples measured by DynTIM Tester is smaller than that measured by LFA. For the DynTIM Tester results, we also find that the slope of the graph of thermal resistance vs. thickness is affected by the usage of thermal grease. From this, we are able to conclude that the wide scattering of thermal conductivity for samples measured with the DynTIM Tester is caused by the change of slope in the graph of thermal resistance-thickness.

For heat exchanger applications, 2-ply clad materials were fabricated by rolling of aluminum (Al) and mild steel sheets. Effects of annealing temperature on interface properties, especially on inter-layer formation and softening of strain hardened mild-steel, for Al/mild steel clad materials, were investigated. To obtain optimum annealing conditions for the Al/mild steel clad materials, annealing temperature was varied from room temperature to 600˚C. At the annealing temperature about 450˚C, an inter-layer was formed in an island-shape at the interface of the Al/mild steel clad materials; this island expanded along the interface at higher temperature. By analyzing the X-ray diffraction (XRD) peaks and the energy dispersive X-ray spectroscopy (EDX) results, it was determined that the exact chemical stoichiometry for the inter-layer was that of Fe2Al5. In some samples, an X-layer was formed between the Al and the inter-layer of Fe2Al5 at high annealing temperature of around 550˚C. The existence of an X-layer enhanced the growth of the inter-layer, which resulted in the delamination of the Al/mild-steel clad materials. Hardness tests were also performed to examine the influence of the annealing temperature on the cold deformability, which is a very important property for the deep drawing process of clad materials. The hardness value of mild steel gradually decreased with increasing annealing temperature. Especially, the value of hardness sharply decreased in the temperature range between 525˚C and 550˚C. From these results, we can conclude that the optimum annealing temperature is around 550˚C under condition of there being no X-layer creation.

The component materials threatened by cavitation include ship propellers as well as turbine runners, pump impellers, pipe lines and radiators. Today it is known that cavitation damage takes place on many other components including on the coding water side of the cylinder liners of diesel engines. Cavitation erosion - corrosion implies damage to materials due to the shock pressure or shock wave that results when bubbles form and collapse at a metal surface within a liquid. To suppress cavitation erosion as well as cavitation erosion - corrosion to hydraulic equipment, innovations such as the improvement in the geometric design of the equipment or the selection of suitably resistant construction materials are necessary. In this study, we investigated that the cavitation erosion - corrosion damage under vibratory cavitation can be reduced by adding of side now velocity to the cavitation bubble group in order to eliminate bubbles formed in sea water environment.

Cavitation erosion-corrosion implies damage to materials due to the shock pressure or shock wave that results when bubbles form and collapse at a metal surface within a liquid. If the liquids corrosive to the material, a condition typically encountered in industry, the component materials may suffer serious damage by a combination of mechanical and electrochemical attack. To suppress cavitation erosion as well as cavitation erosion-corrosion to hydraulic equipments, innovations such as the improvement in the geometric design of the equipment or the selection of suitably resistant construction materials are necessary. This study was tested by using the piezoelectric vibrator with 20kHz, 24μm for cavitation generation. And also, the vibratory cavitation erosion-corrosion tests on commercial mild steel SS41were carried out. We carefully observed the erosion pattern and surface photography. The geometrical mechanism of pit growth, which is to be likely these processing; shallow typelongrightarrowundercut typelongrightarrowwide shallow type.

각종 환경 조건에서 진동 캐비테이션 침식-부식 시험 장치에 의해 연강(SS41)의 캐비테이션 침식-부식 손상 거동에 관한 연구를 한 결과 다음과 같은 결론을 얻었다. 1) 해수 중에서 캐비테이션 침식-부식 손상 거동은 중앙부와 테두리 부에서 거의 비슷한 정도로 발생하여 성장되지만, 증류수 중에서는 테두리부에서 손상이 먼저 발생한 다음 중앙부에도 손상이 점차 일어난다. 2) 비저항이 낮은 수도수 중의 캐비테이션 침식-부식 손상은 초기에는 비저항이 높은 증류수중에서의 것보다 증가하지만 시간이 경과하면서 CaCO 하(3)의 피막 형성에 의해 둔화된다. 3) 케비테이션 침식-부식 손상 특성은 잠복기, 증가기, 감소기 및 안정기의 4단계로 구분된다.

Background : Corrosion is one of the most devastating problems faced by most industries. Mild steel has played a vital role in various fields due to the excellent mechanical properties of mild steel such as low density, high strength-to-weight ratios, good environmental stability, high thermal conductivity, and corrosion resistance. Methods and Results : The total phenolic contents (TPC) and total flavonoid contents (TFC) of the methanolic extract of C. grandiflora and R. verniciflua leaf have been examined, and its corrosion inhibition performance was investigated by weight loss and electrochemical impedance spectroscopy (EIS) and polarization measurements. The surface morphology of mild steel was analyzed by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDX) and by atomic force microscopy (AFM). The percentage composition of polyphenolic compounds was found to be higher in C. grandiflora and R. verniciflua plant extracts, and it was proved to be a superior, eco-friendly, and anti-corrosive inhibitor for mild steel in 1M of H2SO4. The Tafel polarization studies indicate that the plant extract is a mixed-type inhibitor. Scanning electron microscopy/energy -dispersive X-ray spectroscopy (SEM-EDS), and atomic force microscopy (AFM) studies confirmed the formation of a protective film on the metal surface. The corrosion inhibition of the C. grandiflora and R. verniciflua plant extracts was characterized by Fourier transform infrared (FT-IR), UV-visible spectra, and wide-angle X-ray diffraction (XRD) studies; these show the strong interaction between the metal surface and the inhibitor. Conclusion : The methanolic extract was prepared the two different plants like C. grandiflora, and R. verniciflua was studied the corrosion inhibition on the mild steel specimen in acidic medium through various methods involving weight loss measurements, EIS, and potentiodynamic polarization. The results shows that the C. grandiflora, and R. verniciflua plant extracts illustrate an effective corrosion inhibitor for mild steel with good anticorrosion properties in acidic environmen