In this study, STS316L powders prepared by gas atomization are used to manufacture bulk structures with dimensions of 10 × 10 × 10 mm3 using selective laser melting (SLM). The microstructures and hardness of the fabricated 316L stainless steel has been investigated with the laser beam overlap varied from 10% to 70%. The microstructures of the fabricated STS316L samples show a decrease in the balling and satellite of powders introducing defect in the bulk samples and the porosity caused by the gap between the molten metal pools disappearing as the overlap ratio increases, whereas a low overlap ratio results in significant balling and a large amount of isolated powders due to the increased gap between the melt pools. Furthermore, the highest value in Vickers hardness is obtained for the sample fabricated by 30% overlapped laser beams. These results show that the overlap ratio of laser beams in the SLM process should be considered as an important process parameter.

Strawberry jelly as a universal design food was developed using strawberry juice (SJ), sugar, xanthan gum (XG), and locust bean gum (LBG). Experimental variables included SJ concentration (30-40% (w/w)), sugar concentration (7.5-10.0% (w/w)), and the ratio of XG/LBG (0.3-4.0% (w/w)), and response variables were textural (hardness, gumminess, chewiness) and color properties. The formulation of strawberry jelly was optimized against hardness and the interactions among variables were predicted using the response surface methodology. Controlled storage test at 5 or 15°C was conducted to determine the values of the jelly at different temperatures. The optimal SJ and sugar concentrations and the ratio of XG/LBG against hardness were 40, 10, and 1.5%, respectively. The color did not change significantly during storage at 5 and 15°C (p>0.05). However, the textural characteristics during storage increased significantly at 5°C (p<0.05) and the hardness was appropriate to be used as a criterion for determining the shelf life of the jelly. The shelf life at 5°C generated from a zero-order kinetics (R²=0.96) was 40 d according to a criterial value, 1.8 N, of hardness. The Q10 value was calculated as 0.6, which allowed prediction of the shelf life values at different temperatures. The results from this study suggested a formulation of strawberry jelly as a universal design food and allowed determination of the shelf life of the food product.

Shelter that communication equipment and on-equipment material are mounted on is transported by airplane or vehicle, it has a function such as waterproof and shielding EMI. When the shelter is transported by car or helicopter, it is shocked by vibration and crash with the ground. So, three skids are attached to bottom of the shelter to reduce the shock. To confirm the durability of the structure of shelter, parallel drop and rotating drop test were done in accordance with KDS 0000-0000. However, the damage was discovered in the shelter. So, stiffening plate was added to skid and panel of partition wall to obtain durability and changed the shape of rubber buffer. In this paper, the cause of deformation and damage in the shelter was analyzed and improved shape through the structural analysis was verified.

Grains are nutritious foods that richly contain fiber, vitamins and minerals but it would be difficult to chew for some elderly people with weakened chewing ability. This study was aimed to find the appropriate conditions for reducing hardness of grains by enzyme treatment. To select appropriate enzyme, each grain (white rice, brown rice, barely, sorghum, and job’s tears) was soaked for one hour in enzyme solution at optimum activation temperature. Grains were soaked for one hour in selected enzyme solution at different concentration (0.1, 0.3, 0.5 and 0.7%) under warming condition of cooker at 70℃, steamed in electric rice pressure cooker, rapidly cooled at -18℃ for one hour, placed at 20℃ for another hour, and then hardness was measured by texture analyzer. The initial hardness of white rice, brown rice, barely, sorghum, and job’s tears were 6.5 × 104, 7.1 × 104, 7.0 × 104, 7.8 × 104 and 7.7 × 104 N/m 2 , respectively. The lowest hardness of grains, 4.0 × 104, 5.0 × 104, 4.6 × 104, 5.7 × 104 and 4.7 × 104 N/m 2 were obtained with 0.3% of enzyme D solution while the hardness was not changed significantly with higher concentration. These results suggest that some hard grains treated with enzyme would become softer than white rice, and thus these grains may be used to prepare a healthier meal for elderly people having mastication problem.

In this study, the effect of the friction stir welding (FSW) was compared with that of the gas tungsten arc welding (GTAW) on the microstructure and microhardness of Cu-Ni alloy weldment. The weldment of 10 mm thickness was fabricated by FSW and GTAW, respectively. Both weldments were compared with each other by optical microstructure, microhardness test and grain size measurement. Results of this study suggest that the microhardness decreased from the base metal (BM) to the heat affected zone (HAZ) and increased at fusion zone (FZ) of GTAW and stir zone (SZ) of FSW. the minimum Hv value of both weldment was obtained at HAZ, respectively, which represents the softening zone, whereas Hv value of FSW weldment was little higher than that of GTAW weldment. These phenomena can be explained by the grain size difference between HAZs of each weldment. Grain size was increased at the HAZ during FSW and GTAW. Because FSW is a solid-state joining process obtaining the lower heat-input generated by rotating shoulder than heat generated in the arc of GTAW.

To increase the mechanical property of zirconia, we have investigated the phase change and the resulting hardness of zirconia ceramics by hydroxyapatite (HA) powder bed sintering. It was observed using X-ray diffraction that the cubic zirconia phase, which has a higher hardness value than that of the tetragonal phase, was obtained at the surface of 3 mol% Y2O3 doped tetragonal zirconia polycrystal (3Y-TZP) ceramics during the sintering process; in our experimental conditions, the phase change at the surface increased as the sintering time increased. We believe that the observed crystalline phase change originated from the decomposition of HA and the diffusion of CaO, as follows. CaO, which was derived from the decomposition of HA at high temperature (1400˚C), diffused into the surface of 3Y-TZP and acted as a stabilizer. As a result, the Vickers hardness value of the treated specimens was higher than that of the non-treated specimen due to the formation of the cubic phase on the surface of 3Y-TZP.

In this study, in order to increase surface ability of hardness and corrosion of magnesium alloy, anodizingand sealing with nano-diamond powder was conducted. A porous oxide layer on the magnesium alloy was successfullymade at 85℃ through anodizing. It was found to be significantly more difficult to make a porous oxide layer in themagnesium alloy compared to an aluminum alloy. The oxide layer made below 73℃ by anodizing had no porous layer.The electrolyte used in this study is DOW 17 solution. The surface morphology of the magnesium oxide layer wasinvestigated by a scanning electron microscope. The pores made by anodizing were sealed by water and aqueous nano-diamond powder respectively. The hardness and corrosion resistance of the magnesium alloy was increased by the anod-izing and sealing treatment with nano-diamond powder.

Rubber laminated bearings with lead core are highly affected by changes in temperature because key materials which are rubber and lead have temperature dependencies. In this study, two full scale LRB(D800, S=5) are manufactured and temperature dependency tests on shear properties are accomplished. The shear properties at the 3rd cycle are used at -10℃, 0℃, 10℃,20℃, 30℃, 40℃ respectively. The double shear configuration, simultaneously testing two pieces, is applied for compression shear test in order to minimize the friction effects due to the test machine, described in ISO 22762-1:2010. Characteristic strength, post-yield stiffness, effective stiffness, equivalent damping ratio are estimated and presented coefficient due to the temperature changes.

We evaluated the effect of water pH (6, 7, 8 and 9) and hardness (40mg/L and 160mg/L as CaCO3) on the growth of H. incongruens. Both water pH and hardness affected the growth parameter of H. incongruens such as head capsule width and maturity time. The head capsule width of the adults in the highest ph condition was 9.7% increased compared to the lowest ph condition. The maximum difference of the maturity time was 192 hours among the test conditions. Overall, as water ph level increase makes head capsule size of the test animal large, the inter-molt period and maturity time become shorter significantly. The effect of water hardness increasing showed a similar tendency with ph level. Especially, the difference of the growth parameter among the test conditions was increased by growing test animal. There are strong correlation between available amount of intake calcium and growth parameters of test animal. These results indicate that because of calcium demand for growth, water pH level and hardness are the important effect factor in life-cycle of the H. incongruens..

The Fe-based self-fluxing alloy powders and TiC particles were ball-milled and subsequently compacted and sintered at various temperatures, resulting in the TiC particle-reinforced Fe self-fluxing alloy hybrid composite, and the microstructure and micro-hardness were investigated. The initial Fe-based self-fluxing alloy powders and TiC particles showed the spherical shape with a mean size of approximately 80 and the irregular shape of less than 5 , respectively. After ball-milling at 800 rpm for 5 h, the powder mixture of Fe-based self-fluxing alloy powders and TiC particles formed into the agglomerated powders with the size of approximately 10 that was composed of the nanosized TiC particles and nano-sized alloy particles. The TiC particle-reinforced Fe-based self-fluxing alloy hybrid composite sintered at 1173 K revealed a much denser microstructure and higher micro-hardness than that sintered at 1073 K and 1273 K.

In the ALC(Autoclaved lightweight concrete) manufacturing process, if the pre-cured semi-cake is removed after proper time is passed, it will be hard to retain the moisture and be easily cracked. Therefore, in this research, we took the research by multiple regression analysis to find relationship between variables for the prediction the hardness that is the control standard of the removal time. We study the relationship between Independent variables such as the V/T(Vibration Time), V/T movement, expansion height, curing time, placing temperature, Rising and C/S ratio and the Dependent variables, the hardness by multiple regression analysis. In this study, first, we calculated regression equation by the regression analysis, then we tried phased regression analysis, best subset regression analysis and residual analysis. At last, we could verify curing time, placing temperature, Rising and C/S ratio influence to the hardness by the estimated regression equation.

최근 비만의 증가로 식품 산업계에서는 열량이 없거나 적은 원료로 고열량의 원료를 대체하려는 시도를 하고 있다. 본 연구에서는 젤라틴과 한천을 원료로 동일한 경도의 젤을 만들고 이들의 이화학적 특성을 비교하였다. 동일한 경도를 갖는 젤의 제조를 위하여 물 150 g에 정백당 60 g과 각각 젤라틴 12 g, 한천 2 g을 첨가하여 물 50 g 이 증발할 때까지 중탕하여 성형, 냉각한 후 젤을 제조하였다. 경도는 젤라틴과 한천 젤 각각 22.36, 22.80으로 동등하게 제조하였으며, 이 때 응집성, 부착성, 씹힘성 등은 젤라틴 젤이 더 높았다. 제조된 한천 젤과 젤라틴 젤의 pH는 각각 8.17, 7.05였으며, 당도는 각각 12.97, 14.43oBx를 나타내었다. 응력완화를 측정한 결과 5초 후 한천과 젤라틴 젤의 응력은 각각 3.3, 9.5 N 이였으며 각각 5초, 1초 동안에 급격히 응력이 감소된 후 서서히 완화되었으며 응력완화시간은 한천 젤은 2.54초 였고 젤라틴 젤은 측정이 불가능 하였다. 보수력은 한천과 젤라틴 젤이 각각 98.83, 100%였으며 이는 사용된 한천의 농도가 낮기 때문인 것으로 생각된다. 본 연구 결과는 젤라틴 대체 시 경도를 동일하게 하였을 경우 질감을 비롯한 다른 요소들이 어떻게 영향을 주는지를 판단하는데 도움이 될 것으로 사료된다.

This study describes a hydrogen embrittlement evaluation of the subsurface zone in 590DP steel by micro-Vickers hardness measurement. The 590DP steel was designed to use in high-strength thin steel sheets as automotive materials. The test specimens were fabricated to 5 series varying the chemical composition through the process of casting and rolling. Electrochemical hydrogen charging was conducted on each specimen with varying current densities and charging times. The relationship between the embrittlement and hydrogen charging conditions was established by investigating the metallography. The micro-Vickers hardness was measured to evaluate the hydrogen embrittlement of the subsurface zone in addition to the microscopic investigation. The micro-Vickers hardness increased with the charging time at the surface. However, the changing ratio and maximum variation of hardness with depth were nearly the same value for each test specimen under the current density of 150 mA/cm2 and charging time of 50 hours. Consequently, it appears that hydrogen embrittlement in 590DP steel can be evaluated by micro-Vickers hardness measurement.

The indentation technique has been one of the most commonly used techniques for the measurement of the mechanical properties of materials due to its experimental ease and speed. Recently, the scope of indentation has been enlarged down to the nanometer range through the development of instrumentations capable of continuously measuring load and displacement. In addition to testing hardness, the elastic modulus of submicron area could be measured from an indentation load-displacement (P-h) curve. In this study, the hardness values of the constituent phases in Ti()-NbC-Ni cermets were evaluated by nanoindentation. SEM observation of the indented surface was indispensable in order to separate the hardness of each constituent phase since the Ti()-based cermets have relatively inhomogeneous microstructure. The measured values of hardness using nanoindentation were GPa for hard phase and GPa for binder phase. The effect of NbC addition on hardness was not obvious in this work.

본 연구에서는 저경도 고감쇠 고무받침 시험체의 다양한 특성실험을 통하여 저경도 고감쇠 고무받침의 특성을 파악하였다. 고무받침의 파악하고자 하는 특성은 압축강성, 전단강성, 등가감쇠비, 전단특성의 변형율 의존성, 전단특성의 면압 의존성, 전단특성의 주파수 의존성, 전단특성의 온도 의존성, 극한전단특성 등이다. 특성실험은 ISO 22762-1에 따라 수행하였으며, ISO 2276-3에 따라 평가하였다. 특성실험결과 전단강성은 전단변형율과 온도 의존성이 큰 것으로 나타났고, 등가감쇠비는 면압 의존성이 큰 것으로 나타났다. 전단특성의 주파수 의존성 실험결과 0.1Hz를 기준으로 경향이 나뉘는 것으로 나타났다. 0.1Hz 이상에서는 전단특성의 변화가 적었지만, 0.1Hz 이하에서는 전단강성과 등가감쇠비 모두 급격히 감소하는 것으로 나타났다. 추가적으로 크리프실험과 극한전단특성실험을 수행하였고, 실험결과는 ISO 22762-3의 요구사항을 만족하는 것으로 나타났다.

본 연구에서는 경도 이온의 화학적 침전을 위하여 지하수에 과량의 Lime-Soda ash를 주입하여 플럭(floc)을 형성한 다음 침전과정을 십자흐름(Crossflow) 방식의 관형 세라믹 분리막을 이용한 한외여과(UF) 공정으로 대체하였다. 그 결과 두유 포장팩 세척수로 사용하고 있는 지하수의 총경도를 10 mg/L as CaCO3 이하로 감소시킬 수 있었다. 한편, TMP(Trans-membrane pressure) 및 유량 변화 실험에서 투과선속(Permeate flux, J) 및 무차원한 투과선속(J/JO) 변화를 조사하여, TMP 및 유량이 무기물로 형성된 응집 플럭에 의한 막오염에 미치는 영향을 알아보았다. 그 결과, 본 실험 범위에서 TMP 및 유량 변화가 막오염과 총경도 제거율에 미치는 영향은 거의 없었다.

The microstructure and hardness of (W,Ti)C cemented carbides with a different metallic binder composition of Ni and Co fabricated by powder technology were investigated. The densifications of the prepared materials were accomplished by using vacuum sintering at . Nearly full dense (W,Ti)C cemented carbides were obtained with a relative density of up to 99.7% with 30 wt.% Co and 99.9% with 30 wt.% Ni as a metallic binder. The average grain size of the (W,Ti)C-Co and the (W,Ti)C-Ni was decreased by increasing the metallic binder content. The hardness of the dense (W,Ti)C-15 wt%Co and (W,Ti)C-15 wt%Ni, was greater than that of the other related cemented carbides; in addition, the cobalt-based cemented carbides had greater hardness values than the nickel-based cemented carbides.

The aims 0 1' t his study we re to evaluate proliferative and apoptotic cell distribution pattern in condylar articu lar and pl'oliferative layer as two types of diet(soft and ha rd) we1'e supplied to growing 1'a ts, 30 male Sprague Dawley g1'owing l'ats(twenty-one c1ays fl'om bi l'th) were c1ivided into two group, Each 15 rats were supplied by soft and hal'd di et , After c1 iluted Bl'du solution(5mg/ Kg)was injected into pel'itoneum befol'c sacrificc. rats wel'e sacl'i f iced at 1. 2. 3 week llltel'vals St1'eptoavidin-Biotin method for Brdu was used to evaluate celluJar proliferative activity. ancl fluol'escent TUNEL method was used to estima te the apoptotic activity, The results about this expe riment wel'e recorded about ante1'io1' and posterior condyle separateJy, In anteriol' portion of condyle, soft diet group showed inc1'eased p1'olife1'ative celluJar activity tha n hal'd diet group dw'ing 1, 2 week but decl'eased than hal'd diet g1'oup at 3 weeks. while hal'd diet group showed constant p1'oliferative cellular activity during all experimenta l period , ln posterior pOl'tion of condyl e、soft diet group showed increased activity than hard diet group at 3 weeks, while ha rd di et gl'oup showed constant proliferative cellular activity during exper‘ imental period , In a nterior pOl'tion of condyle‘ soft c1 iet group showed increased apoptotic activity with time progress, but hard diet group showed continuous low level of activity during experimental period , In posterio1' porti on 0 1' condyle, hard diet group showed cons tant low level apoptotic activity, plthough showed the lowes t leveJ at 1 week, On the con trary soft diet g1'oup showed c1ecl'eased apoptotic activity wi th time progress, ConcJusively, in soft diet group an teroposterior direction was reduced in condyJar morphologic dimension because of decreased prol iferative cellular and increased apoptotic activity on anterior portion and vertical dimension 0 1' condyle was increased because of increased proliferative cellular and decreased apoptotic activity on posterior portion. but in hard di et group proli ferative cellular and apoptotic activity were comparatively constant. and thus harcl diet group s howed antet'opos teriorJy broad and flat condylar morphoJogy

To meet the demands for use in extremely abrasive and corrosive environments, a new material was developed. The VeKo25Cr distinguishes itself through specifically selected amounts of carbon and carbide forming elements such as Cr, Mo, V, W and Nb. The alloy is based on a Fe matrix. The strength after heat treatment and the wear and corrosion properties are compared to those of other materials. VeKo25Cr can be combined with easy-to-process materials such that the difficult handling is minimized to those places on the piece most subjected to operational wear.