• Imaging Science in Dentistry
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• v.53 no.4
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• pp.355-363
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• 2023

Purpose: Sonographic elastography can be used to evaluate the hardness of muscle tissue through the application of compression. Strain elastography gauges hardness through the comparison of echo sets before and after compression. This study utilized ultrasonography to measure the thickness and hardness of the masseter muscle in individuals with temporomandibular joint(TMJ) osteoarthritis. Materials and Methods: This study included 40 patients who presented with joint pain and were diagnosed with TMJ osteoarthritis via diagnostic cone-beam computed tomography, along with 40 healthy individuals. The thickness and hardness of each individual's masseter muscle were evaluated both at rest and at maximum bite using ultrasonography. The Mann-Whitney U test and the chi-square test were employed for statistical analysis, with the significance level set at P<0.05. Results: The mean thickness of the resting masseter muscle was 0.91 cm in patients with osteoarthritis, versus 1.00 cm in healthy individuals. The mean thickness of the masseter muscle at maximum bite was 1.28 cm in osteoarthritis patients and 1.36 cm in healthy individuals. The mean masseter elasticity index ratio at maximum bite was 4.51 in patients with osteoarthritis and 3.16 in healthy controls. Significant differences were observed between patients with osteoarthritis and healthy controls in both the masseter muscle thickness and the masseter elasticity index ratio, at rest and at maximum bite (P<0.05). Conclusion: The thickness of the masseter muscle in patients with TMJ osteoarthritis was less than that in healthy controls. Additionally, the hardness of the masseter muscle was greater in patients with TMJ osteoarthritis.

• Transactions of Materials Processing
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• v.8 no.1
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• pp.57-64
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• 1999

The press formability analysis of welding parts was studied in the current work by the tailor welded blank. As the body panel is used in the press forming of welding parts by a weld method of the tailor welded blank, the following conditions are demanded: 1) The strength of welding parts must be the higher than base metals. 2) After the welding, severe welding deformatins must be avoided. 3) The press formability of welding parts is similar to that of many base metals. 4) The productibility of a welding has to be higher. There are many welding methods satisfying these conditions, but the purpose of this study is to inbestigate the upset weldability and formability of the material (SPCC). SPCC steel sheet showed good weldability and formability under some welding conditions. The experimental results were discussed by the evaluation of the results obtained from tensile tests, hardness tests, micro-structures and Erichsen cup test was a little lower than that of parent material.

• Laser Solutions
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• v.4 no.1
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• pp.29-38
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• 2001

This work was carried out to investigate the welding behavior of thin A3003 Al alloy sheets by Nd : YAG laser beam. Considering bead shape and mechanical properties, the laser pulse shapes selected were two kinds of 2-division and 3-division by varying power level and pulse duration. In order to obtain optimum conditions, the factorial design method and central composite design method were applied. Tensile test, optical microscopy, micro hardness test and TEM analysis were performed. Due to the annealing caused by thermal effect during laser welding, precipitates were coarsended. The HAZ was softened and failed during tensile test. The hardness of HAZ was lower than that of base metal, since the heat input relieved the work hardening effect and caused grain growth.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.46-49
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• 2003

Aluminum based metal matrix composites(MMCs) are well known for their high specific strength, stiffness and hardness. They are gaining further importance because of their high wear resistance. In this study, Al/Saffil-20%, Al/Saffil-5%/Al2O3(particle type)-15% and Al/Saffil-5%/SiC(particle type)-15% hybird MMCs' wear behavior were characterized by the pin-on-disk test under various normal load The superior wear resistance was exhibited at Al/Saffil-5%/SiC(particle type)-15% MMCs. And this MMCs' predominant wear mechanism is subsurface cracking in the low load wear regime. Others(Al/Saffil-20%, Al/Saffil-5%/Al2O3(particle type)-15%) showed the similar wear resistance with each other at the same test condition. In the low load & room temperature condition, the wear resistance was improved due to the high hardness of the ceramic reinforcements. As the test load increased, the wear properties were governed by the wear properties of matrix.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.4
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• pp.181-190
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• 2004

The interest of the fatigue life of rubber components such as engine mounts is increasing according to the extension of warranty period of the automotive components. Automotive engine mounts get damaged due to thermal and mechanical loadings. This paper discusses a fatigue life prediction of the 3-dimensional dumbbell specimens for natural rubber compound considering the effects of maximum strain and heat aging temperature. Displacement controlled fatigue life tests were performed using specimens with different levels of maximum strain and various hardness. The basic mechanical properties test and the fatigue test of aged rubber specimen under normal and elevated temperature were executed. A procedure to predicted the fatigue life of vulcanized natural rubber material based on the maximum strain method was proposed, and then this curve was in good agreement with fatigue test data less than 200% error range.

• Journal of Technologic Dentistry
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• v.21 no.1
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• pp.43-53
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• 1999

The mechannical properties and corrosion resistance of alloy added commercially pure titanium for dental implants have been investigated. Ti, To-65Zr, Ti-10.1Ta and Ti-17Sn alloys were melthed in arc furnace and the corrosion resistance of Ti alloys was evaluated by anodic polarization test. The microstructure and mechanical properties of Ti alloy were analysed by optical micrograph. hardness tester and instron. In isothermal test, Ti-10.1Ta and Ti-17Sn alloys exhibited the best oxidation resistance below $1100^{\circ}C$. Ti65Zr, Ti-10.1Ta and Ti-17Sn alloys showed better rockwell hardness compared with commercially pure. Ti As the result of the anodic polarization test in 5%HCl, it 5%HCl, it was known knows that Ti-65Zr, alloy showed a rapid decrease in current density at higher potenial in comparision with other Ti alloys.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.45-50
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• 2005

In this study, the casting/forging process was applied in manufacturing a low control arm, in order to prove that application of casting/forging process to Al6061 is likely to get the effect of light weight compared with existing steel products and to reduce the cost of materials. Firstly, In order to set up the optimum casting condition of the forging material, Al6061, casting experiments were carried out by controlling pouring temperature of the aluminum for casting, mold temperature, and pouring time. $700^{\circ}C$ pouring temperature, $300^{\circ}C$ mold temperature and 10-second pouring time were taken into account as the optimum casting conditions. With respect to a hot forging test, it is practiced on the basis of a temperature of materials, strain rate, and reduction rate so as to observe each microstructure and examine strain-stress curve simultaneously; examine tensile test and hardness test; eventually set up the optimum hot forging condition. A hot forging test, tensile test, hardness experiment, and microstructure observation were carried out on condition of $70\%$ reduction rate, $500^{\circ}C$ temperature of materials, and 1 strain rate. As a result of those experiments, 330MPa tensile strength, $16.4\%$ elongation, and 122.8Hv hardness were recorded. In oder to get a sound preform which has no unfitting cavity and less flash, two preforms were proposed on the basis of volume rate of the final product; the optimum volume rate of preform for the low control arm was $115\%$. In conclusion, it is confirmed that using the forging material rather than casting materials in casting/forging process is likely to get more superior mechanical properties. Compared with Al6061, performed by means of general forging, moreover, cast/forged Al6061 can not only stimulate productivity by reducing production processes, but cut down the cost of materials by reusing forging scraps.

• Journal of the Korean Society for Heat Treatment
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• v.21 no.1
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• pp.10-19
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• 2008

To investigate the effect of ultrasonic nano-crystalline surface modification (UNSM) treatment on rolling contact fatigue and residual stress properties of bearing steels, this paper carried out a rolling contact fatigue test, measured residual stress and retained austenite, performed a wear test, observed microstructure, measured micro hardness, and analyzed surface topology. After the UNSM treatment, it was found that the surface became minute by over $100{\mu}m$. The micro surface hardness was changed from Hv730~740 of base material to Hv850~880 with about 20% improvement, and hardening depth was about 1.3 mm. The compressive residual stress was measured as high as -700~-900 MPa, and the quantity of retained austenite was reduced to 27% from 34%. The polymet RCF-6 ball type rolling contact fatigue test showed over 4 times longer fatigue lifetime after the UNSM treatment under 551 kgf load and 8,000 rpm. In addition, this paper observed the samples, which went through the rolling contact fatigue test, with OM and SEM, and it was found that the samples had a spalling phenomenon (the race way is decentralized) after the UNSM treatment. However, before the treatment, the samples had excessive spalling and complete exploration. Comparison of the test samples before and after the UNSM treatment showed a big difference in the fatigue lifetime, which seems to result from the complicated effects of micro particles, compressive residual stress, retained austenite, and surface topology.

• Korean Journal of Food Science and Technology
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• v.16 no.3
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• pp.303-308
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• 1984

Instrumental and sensory characteristics of chewing gums were measured at each masticatory stage, and the correlations between the characteristics were analyzed. In instrumental characteristics, similarities were proved between initial puncture work and puncture force, intermediate hardness and penetration work, final hardness and penetration work, and adhesion work and adhesion force. Final hardness correlated highly with yield force and the slope of force-distance curve of penetration test, and the slope also correlated significantly with springiness and adhesion force. In sensory characteristics, the correlations of the same parameter between trained panel and consumer were extremely high. Initial stiffness correlated significantly with both intermediate and final firmness by consumer. Highly significant correlations were obtained between final firmness and stiffness and between lift and cohesion by trained panel, whereas firmness correlated with adhesion negatively.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.72-79
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• 2011

In this paper, the fatigue characteristics of shot peened A7075-T651 alloy were compared with those of the specimens without the shot peening. The multi-spindle and single-spindle rotating bending fatigue testing machines were employed for the evaluation. Shot peening (SP) with various pressure (5 psi, 10 psi, 15 psi, 25 psi and 35 psi) were used in this test. In order to investigate the effect of the applied pressure during the SP, we carried out the surface roughness test, compressive residual stress test, hardness test, tensile test, VHCF (Very high cycle fatigue) test and SEM observation. SP induced the formation of remarkable compressive residual stress from the surface to certain depth of sample by means of the plastic deformation. The surface hardness and the fatigue characteristics of the specimens were also modified by the SP. According to the S-N curves, fatigue lives of shot peended sample with 25 psi measures 50 times higher than that of the untreated sample. The fatigue lives of shot peened sample with 15 psi and 35 psi measure approximately 10 times higher than that of the untreated ones.