• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.429-436
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• 2013

This study considers how the fatigue behavior and probabilistic properties of SAE1055 steel are related to its hardness level. SAE1055 steel was heat-treated using induction hardening. Five types of specimens were prepared (A: base material, B: through hardened material with HV390, C: through hardened material with HV510, D: through hardened material with HV700, and E: surface hardened material with HV700). Fatigue tests were performed under a stress ratio of R = -1 using a 4-point rotary bending fatigue tester. The fatigue behaviors were greatly influenced by the hardness, but the fatigue limit did not increase over a hardness of HV510. In addition, the effect of the hardness level on the failure mechanism was evaluated using a scanning electron microscope. The probabilistic properties of the fatigue life were investigated using a probabilistic S-N approach, and the effect of the hardness level on these properties was evaluated using a residue analysis.

• Korean Journal of Food Science and Technology
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• v.29 no.5
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• pp.987-991
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• 1997

Effect of morphology and granule size of crystalline D-sorbitol on texture of sugar-free chewing gum was investigated with different morphology of sorbitol such as a compact shaped P-type and a loose shaped S-type, and with different granule size such as 50 mesh, 80 mesh, and 100 mesh. The chewing gum including S-type sorbitol exhibited an increased flexibility and a decreased hardness as compared with that including P-type sorbitol. S-type sorbitol was chosen as a solid phase of sugar-free chewing gum because the consumer preferred a chewing gum with high flexibility and low hardness. The flexibility and hardness of chewing gum including S-type sorbitol were determined to be optimum at 80 mesh of the sorbitol size. The flexibility of the chewing gum including 80 mesh S-type sorbitol increased but the hardness decreased with increasing temperature.

• Korean Journal of Environmental Agriculture
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• v.30 no.4
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• pp.402-408
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• 2011

BACKGROUND: Effect of various light wavelength and plant defense molecules were evaluated on the hardness and the contents of free amino acid including ${\gamma}$-aminobutyric acid (GABA) in soybean sprouts. METHODS AND RESULTS: Germinating soybean seeds were treated with various single wavelength of light (380, 440, 470, and 660 nm) or without light at $25^{\circ}C$ for six days. Soybean seeds were also treated with stress-signaling molecule ethephon or $H_2O_2$ at the same time. Soybean sprouts treated with 470 nm substantially raised the hardness almost two times than the control. The free amino acid contents were higher in 470 nm and $H_2O_2$ treated soybean seeds than the control. Nutritionally beneficial GABA contents were increased by the treatments of 470 nm, 440 nm, ethephon, and $H_2O_2$. CONCLUSION: These results suggest that the hardness and the contents of amino acids can be regulated by stimuli, which stimuli could be composed of various wavelength and plant defense molecules. Especially, single wavelength 470 nm illumination has the effect of increasing GABA contents with increased hardness.

• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.895-900
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• 2018

In this study, the electroless deposition of Co-B and Co-W-B alloy thin films was developed and the effect of B and W contents on the hardness of the alloy thin films were investigated. An amorphous Co alloy film was successfully formed by electroless deposition and the contents of B and W in the film were controlled by varying the concentrations of dimethylamine borane and sodium tungstate dihydrate, which were used as a reducing agent and W source, respectively. The hardness of the thin films increased as the contents of B and W were increased because B and W act as impurities suppressing the propagation of dislocation in a film. In addition, it was found that the content of B and W in the Co alloy films can be increased significantly when aeration is not performed. Finally, the hardness of Co-W-B alloy thin film was improved up to 8.9 (${\pm}0.3$) GPa.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.282-287
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• 2023

The effect of stress relief heat treatment temperature and duration time on the microstructure, residual stress and Vickers hardness of additively manufactured Ti-6Al-4V alloy using laser powder bed fusion process was clarified. As a result of stress relief heat treatment for 240 minutes at 823 K and 60 minutes or more at 873 K, residual stress was decreased less than 30 MPa without grain growth and phase transformation which causes dimensional distortion and deterioration of mechanical properties. In addition, hardness was increased with increasing heat treatment temperature and duration time. It was deduced that the refinement of acicular martensitic α' phase due to the increasing duration time of isothermal heat treatment at 773~873 K, which was not detected by XRD and phase map analysis using SEM-EBSD, probably increases the hardness.

• Journal of Pharmaceutical Investigation
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• v.4 no.1_2
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• pp.39-45
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• 1974

According to previous paper, the hardness of semi-solid as ointments and suppositories causes the tough or skin, the pain and connected with absorption, the state of spread or the efficiency of drug. When the hardening agent or the softening agent is added to ointment whid, is registered on the pharmacopeia of the republic of Korea, the experimertal data by apparent logarithmic hardness are shown is Table 1. The results are as the folloring. 1) In case of the softening agent which is added to ointment base, each has shown two different equation with differnented slope as $K_1$ and $K_2$ value determined (Fig. 1,2). 2) When the hardening agent is added to same ointment base, these studies indicated that there is a direct correlation between $K_1$ and $K_2$. However, in case of softening agent $K_1$ and $K_1$ are not correlated as indicated in Fig. $3{\sim}8$. 3) On condition of same ointment base, the critical poit is proportional to $K_1$ 4) The second effect is at least $3{\sim}17$ times more. sensitive than the first effect or in average 8.3 times more sensitive, Therefore, the results presented in this paper. Suggest that, when the drug is added to a certain ointment base, it should be added within this first effect before the critical point is reached.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.3
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• pp.77-81
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• 2017

Pulse electroplating of Ni-P alloy was studied to fulfill the material requirement to the advanced vertical probe tip in wafer probe card. The major concerns are for the electrical conductivity and yield strength. Plating parameters such as current density, duty cycle and solution components were examined to obtain the nanocrystal structure and proper percentage of phosphorus, leading to how to control the nanocrystal grain growth and precipitation of $Ni_3P$ after heat treatment. Among the parameters, the amount of phosphorus acid was the main factor affecting on the grain size and sheet resistance, and the amount of 0.1 gram was appropriate. Since hardness in Ni-P alloy is increased by as-plated nanocrystal structure plus precipitation of $Ni_3P$, the concentration of P less than 15 at% was better choice for the grain coarsening without minus in hardness value. The following heat treatment made grain growth and dispersion of precipitates adjustable to meet the target limit of resistance of $100m{\Omega}$ and hardness number of over 1000Hv. The Ni-P alloy will be a candidate for the substitute of the conventional probe tip material.

• Elastomers and Composites
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• v.43 no.4
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• pp.213-220
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• 2008

In this study, the effects of curing system on the hardness of rubber materials at various temperature were investigated. NR and SBR were compounded with various sulfur or peroxide content, in order to obtain various crosslink densities. The changes of hardness and crosslink density were measured as a function of temperature and the relationship was examined. The thermal stresses were also measured in order to investigate the effect of entropy as a function of temperature. The hardness of NR and SBR compounds increased with increasing temperature above room temperature, and the measured thermal stress increased as temperature increased. However, the crosslink densities were not changed by temperature change.

• Journal of Power System Engineering
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• v.5 no.3
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• pp.88-94
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• 2001

Stellite 12 alloy-powders were overlaid on 410 stainless steel valve seat using plasma transferred arc(PTA) process. Variation of the microstructure, hardness, wear and corrosion of overlaid deposit with current change was investigated. The deposit showed hypoeutectic microstructure, which was consisted of primary cobalt dendrite and networked $M_7C_3$ type eutectic carbides. As current increased, the amount of eutectic carbide decreased and its dendritic secondary arm spacing increased. Hardness of the deposit was decreased with increase of current. Stress relief heat treatment at $600^{\circ}C$ for two hours resulted in slight increase of hardness in the deposit and showed uniform hardness distribution in base metal without any hardened layer in HAZ. Specific wear decreased with increase of sliding distance. The deposit of high hardness with a lot of eutectic carbide showed relatively low specific wear. Initial corrosion current density of the deposit in 0.1N sulfuric acid was lower than those of 410 stainless steel, and showed a little variation with PTA current.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.2
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• pp.168-176
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• 2004

Interrupted creep tests were carried out on the Mod.9Cr-1Mo steel in order to investigate the structural degradation during creep. The ranges of creep stress and temperature were from 71 to 167MPa and 873 to 923k, respectively. The change of hardness and tempered martensitic lath width were measured in the grip and gauge parts of interrupted specimens. The lath structure was thermally stable in static conditions, but was not stable during creep, and the structural evolution was enhanced by creep strain. The relation between the change in lath width and strain was described in the from, $\delta$W= a ($W_s-W_o$)$cdot;varepsilon$, where $\varepsilon$ is the strain, $W_o$is the initial lath width, $W_s$ is the final lath width depending solely on stress, and a is the constant of the magnitude of 0.67 $\mu$m /strain. The change in Victors hardness was expressed by a one-valued function of creep life consumption ratio. Based on the empirical relation between strain and lath width, a model was proposed to explain the relation between change in hardness and creep life consumption ratio. The model revealed that about 65$%$ of dislocations in lath structures were eliminated by the migration of subboundaries.