• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.8
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• pp.1907-1914
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• 1995

An on-line measurement of the workpiece hardened depth in laser surface hardening processes is very much difficult to achieve, since the hardening process occurs in depth wise direction. In this paper, the hardened depth is estimated using a multilayered neural network. Input data of the neural network are the surface temperatures at arbitrary chosen five surface points, laser power and traveling speed of laser beam torch. To simulate the actual hardening process, a finite difference method(FDM) is used to model the process. Since this model yields the calculation results of the temperature distribution around the workpiece volume in the vicinity of the laser torch, this model is used to obtain the network's training data and laser to evaluate the performance of the neural network estimator. The simulation results show that the proposed scheme can be used to estimate the hardened depth with reasonable accuracy.

• Tribology and Lubricants
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• v.32 no.1
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• pp.18-23
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• 2016

The effective case depth for case-hardened rolling bearing has been discussed. For this purpose, rolling contact fatigue tests for ball bearings built with inner race of various hardness values were conducted until L₁₀ calculating rating life using a bearing life test machine under radial loading. Then, the distribution of residual stress below the inner raceway, which depended on the hardness value, was measured by X-ray diffraction. As a result, the linear relationship was established between the hardness value of the inner race and the theoretical shear stress evaluated at the depth where the residual stress disappeared below the inner raceway. Based on the relationship, it could be found that the factor of safety in bearing manufacturer’s rules for the effective case depth of case hardened rolling bearings was set higher. However, it could be also found that the hardness values at the depth where the maximum shearing stress acted below the raceway surface in a tapered roller bearing hardened by the carburizing process, were not sufficient for preventing plastic deformation under the basic dynamic load rating. Consequently, further efforts were still required to reduce or to disperse the contact load on the material design of a rolling bearing in order to prolong its life.

• Journal of the Korean Society of Safety
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• v.23 no.1
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• pp.18-23
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• 2008

The abnormal wears such as unfair-wear and early-wear happen in the earn shaft surface of automobiles. These abnormal wears make efficiency of engines decrease and threaten safety of automobiles. The wear characteristics of the cam shaft is very important for the automobile safety. The cam shaft is surface-hardened by the high frequency induction. In this study, we investigated the wear characteristics of the hardened surface with a SM53C steel. The wear characteristics is examined according to the hardened depth and the amount of load.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.134-142
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• 1998

The effects of small hole defect size and effective case depth(ECD) on the four point bending fatigue limit of induction surface hardened S45C steel were investigated the fatigue limit evaluation of hardened materials is very difficult because of relations of the hardness gradient and residual stress. In this study, it was possible to characterize fatigue limit and fatigue life of induction surface hardened S45C steel in terms of the hole defect size and effective case depth(ECD) and quantitative evaluation of the fatigue limit with hole defects use Murakami's evaluation method and the range of evaluated values is a good accuracy compared with results.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.12
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• pp.1048-1054
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• 2003

In laser surface hardening processes, the geometrical parameters such as the depth and the width of a hardened layer can be utilized to assess the hardened layer quality. However, accurate monitoring of the geometrical parameters for on-line process control as well as for on-line quality evaluation is very difficult because the hardened layer is formed beneath a material surface and is not visible. Therefore, temperature monitoring of a point of specimen surface has most frequently been used as a process monitoring method. But, a hardened layer depends on the temperature distribution and the thermal history of a specimen during laser surface hardening processing. So, this paper describes the estimation results of the geometric parameters using multi-point surface temperature monitoring. A series of hardening experiments were performed to find the relationships between the geometric parameters and the measured temperature. Estimation results using a neural network show the enhanced effectiveness of multi-point surface temperature monitoring compared to one-point monitoring.

• Journal of the Korean Society for Heat Treatment
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• v.6 no.4
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• pp.230-236
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• 1993

The laser beam hardening has been experimentally tried to find the hardened characteristics of STD11. Experiment was performed on the optimum hardening condition with 2kW $CO_2$ laser. The microstructure of the hardened layers was observed using the microscope. The hardened zones exhibits very high Vickers microhardness of 720 Hv, however, the deoxidation was observed under the surface of hardened area. The case depth of hardened zones is about 0.6mrn and case width is 4mm. FEM-simulation on laser surface hardening of STD11 steel are described. With the proper assumption of the absorbed energy density, the calculated case depth and width in 2 kW $CO_2$ laser hardening were in good agreement with the experimental result. It was found that there is optimum absorbed energy density of STD11.

• Korean Journal of Materials Research
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• v.3 no.5
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• pp.538-545
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• 1993

By using propagation characteristics of ultrasonic surface wave, the depth of the surface hardened layer of SCM440 steel with different high frequency induction heat treatments was measured and the same was done on the carburized SCM415 steel. The propagation velocity of surface wave was constant and independent of frequency in t.he specimens with identical microstructure, it was, however, decreased by 59m/s in the hardened layers compared to the unhardened part. From t.he relationship between the effective case depth and the wave length of surface wave, the depth of the hardened layer could be measured and evaluated nondestructively for both induction hardened and carburized steels.

• Journal of Ocean Engineering and Technology
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• v.5 no.1
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• pp.71-80
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• 1991

This paper reveals the effect of the effective case depth(ECD) on the fatigue behavior of a high-frequency induction hardened SM45C in rotated bending fatigue test. In addition, the effects of fracture modes(surface origin type, inner origin type) on it are discussed. The fatigue limit of the induction hardened steel is remarkably increased compared with that of base metal. In addition, the fatigue limit is linearly increased as the effective casedepth grows deep in the region of this experiment (ECD/R;0.23-0.49). The S-N curve and fracture mode in the induction case hardened steel are classified into two kinds, as a result : N$_{f}$<10$^{5}$ ;surface origin type fracture(at high stress), N$_{f}$>10$^{5}$ ; in ner origin type fracture(at low stress). In case of inner origin type fracture; as the effective case depth(ECD) gets deep, the fatigue limit is increased by the reason that the fracture origin moves toward center; in reverse, is decreased by reason that the compressive residual stress gets low. As a result, the increasing effect of the former is much bigger than the decreasing effect of the latter, and the fatigue limit is increased as the ECD gets deep.eep.

• Advances in Computational Design
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• v.7 no.1
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• pp.57-68
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• 2022

A simulation study of the distribution of magnetic flux induced by a U-shaped electromagnet into a two-layer massive object with variations in the depth and properties of the surface layer has been carried out. It has been established that the hardened surface layer "pushes" the magnetic flux into the bulk of the magnetized object and the magnetic flux penetration depth monotonically increases with increasing thickness of the hardened layer. A change in the thickness and magnetic properties of the surface layer leads to a redistribution of magnetic fluxes passing between the poles of the electromagnet along with the layer and the bulk of the steel object. In this case, the change in the layer thickness significantly affects the magnitude of the tangential component of the field on the surface of the object in the interpolar space, and the change in the properties of the layer affects the magnitude of the magnetic flux in the magnetic "transducer-object" circuit. This difference in magnetic parameters can be used for selective testing of the surface hardening quality. It has been shown that the hardened layer pushes the magnetic flux into the depth of the magnetized object. The nominal depth of penetration of the flow monotonically increases with an increase in the thickness of the hardened layer.

• Laser Solutions
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• v.18 no.2
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• pp.1-4
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• 2015

This study is related to the surface hardening treatment to spheroidal graphite cast iron for die by using high power diode laser. Laser device used in this experiment is capable of real-time laser power control. This is because the infrared temperature sensor (two color pyrometer) attached to the optical system measures the surface temperature of specimen and adjusts the laser power in real time. The surface treatment was carried out with the change of heat treatment temperature at the beam travel speed 3 mm/sec. Hardened width and depth was measured and hardened zone was analyzed by micro vickers hardness test in order to research the optimum condition of heat treatment. The changes in microstructure of the hardened zone also was examined. As a result of hardness measurement and observations on microstructure of hardened zone, hardness increased over three times as compared with base metal because the martensite was formed on the matrix structure.