• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.9
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• pp.100-106
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• 2020

This study analyzes the residual stress of AISI 1536V for an engine shaft of the shipbuilding industry and AISI A387 for a reactor shell of the chemical refining industry by the hole drilling method with a strain gauge rosette, which transforms fine mechanical changes into electrical signals. Tensile residual stress is generated in the forging and heat treatment process because specimens are affected by thermal stress and metal transformation stress. In the heat treatment process, the residual stress of AISI A387 is almost 170% the yield strength at 402 MPa. Since during the machining process, variable physical loads are applied to the material, compressive residual stress is generated. Under the same condition, the mechanical properties greatly affect the residual stress during the machining process. After the stress-relieving heat treatment process, the residual stress of AISI A387 is reduced below the yield strength at 182 MPa. Therefore, it is necessary to control the temperature, avoid rapid heat change, and select machining conditions depending on the mechanical properties of materials during manufacturing processes. In addition, to sufficiently reduce the residual stress, it is necessary to study the optimum condition of the stress-relieving heat treatment process for each material.

• Corrosion Science and Technology
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• v.11 no.6
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• pp.280-285
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• 2012

Aluminum is on active metal, but it is well known that its oxide film plays a role as protective barrier which is comparatively stable in air and neutral aqueous solution. Thus, aluminum alloys have been widely applied in architectural trim, cold & hot-water storage vessels and piping etc., furthermore, the aluminum alloy of AC8A have been widely used in mold casting material of engine piston because of its properties of temperature and wear resistance. In recent years, the oil price is getting higher and higher, thus the using of low quality oil has been significantly increased in engines of ship and vehicle. Therefore it is considered that evaluation of corrosion resistance as well as wear resistance of AC8A material is also important to improve its property and prolong its lifetime. In this study, the effect of solution and tempering heat treatment to corrosion and wear resistance is investigated with electrochemical method and measurement of hardness. The hardness decreased with solution heat treatment compared to mold casting condition, but its value increased with tempering heat treatment and exhibited the highest value of hardness with tempering heat treatment temperature at $190^{\circ}C$ for 24hrs. Furthermore, corrosion resistance increased with decreasing of the hardness, and decreased with increasing of the hardness reversely. As a result, it is suggested that the optimum heat treatment to improve both corrosion and wear resistance is tempering heat treatment temperature at $190^{\circ}C$ for 16hrs.

• Transactions of Materials Processing
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• v.6 no.5
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• pp.435-445
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• 1997

In order to study the manufacturing possibility of connecting rod by direct quenching method, the difference between connecting rod by direct quenching and that by general heat treatment were investigated by observing microstructure, by measuring mechanical properties, by conducting fatigue testing, and by measuring the amount of tool wear in actual cutting. Connecting rod manufactured by direct quenching had better fatigue life than that by general heat treatment, which was due to homogeneous microstructure, and higher strength. The amount of cutting tool wear of connecting rod by direct quenching was higher than that by general heat treatment, which was due to low machinability and high toughness of tempered martensite microstructure. Therefore it will be added the study of heat treatment and cutting condition for manufacturing by direct quenching.

• Journal of the Korean institute of surface engineering
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• v.47 no.3
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• pp.116-120
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• 2014

The addition of cyclo propane carbonyl (cpc) to chromium electroplating bath resulted in a chromium deposit which had greatly improved mechanical properties compared to conventional chromium deposits in condition of heat treatment at high temperature. The as-deposited layers had a Vicker's hardness of about 1170, which is comparable to that of conventional chromium plating deposits. With annealing, the hardness goes through a maximum of 1650 at $600^{\circ}C$. Generally speaking, the hardness of conventional plating decreases monotonically with heat treatment. X-ray diffraction show that annealing up to above $400^{\circ}C$ causes formation and growth of chromium crystallites and that chromium carbides form at above $500^{\circ}C$ temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.102-106
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• 2009

Thermal energy control is a important factor in a large size casting and forging. Good control of thermal energy makes characteristics and defect of large cast-forged part, such as large sized forged shell. We have studied about not only large size ring forging process and after heat treatment by FEM simulation. Also, changes of temperature and microstructure for forged shell were predicted. Therefore, we can choose the proper heat treatment condition by FEA. The sectional properties confirmed by practical experiment and evaluation have presented possibilities of process design by computational analysis.

• Bulletin of the Korean Chemical Society
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• v.14 no.6
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• pp.700-704
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• 1993

The photocatalytic alanine and hydrogen production reaction were studied by using CdS as a semiconductor photocatalysts. The rate of alanine and hydrogen production depends strongly on the temperature in heat treatment of CdS powder. In particular, the rate of alanine production, which was observed using Pt/CdS(A)-(CdS from Mitsuwa), was increased about six times than that of using Pt/CdS(B)-(CdS from Furruchi) under the same heat treatment condition at 500$^{\circ}$C. And the photocatalytic activity for alanine production using bare CdS(A) or Pt/CdS(A) was almost same with increasing temperature in heat treatment in the range of 100-600$^{\circ}$C. From X-ray diffraction data and photoluminescence spectrum, we conclude that the crystal structure changes of CdS(A) or strong interaction at interface of Pt and CdS contribute to increasing the rate of alanine and hydrogen production reaction.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.5
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• pp.824-829
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• 2012

The purpose of this study is to evaluate the proposed jig for turning process of large-scale aluminum tube of D500mm through Finite Element Analysis (FEA). Also, a machining evaluation is conducted with general heat-treated and cryogenic heat-treated tubes. Dimensions of the specimens are determined to be suitable for collet appearance. The characteristics of equivalent stress and strain according to the expansion of the collet are evaluated by FEA. The aluminum tubes which are heat-treated by T4/T6 condition and cryogenic condition are machined by using a large-scale lathe machine and the roundness of machined tube is evaluated by using a 3D measuring machine. Through the results of this study, effects of each heat treatment and residual stress on the roundness are established.

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.6
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• pp.1410-1415
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• 2008

Acupuncture and herbal treatment are based on diagnosis of cold and heat pattern in Traditional Korean Medicine. This diagnosis is accomplished through pulse, tongue and question examination, which are not objective. Quantification and objectification of this diagnosis process are required for efficacious treatment and traditional medicine development. In this study, we developed the cold-heat pattern questionnaire for this purpose. Seventy nine patients who visited oriental medical hospital were included in this study. The cold-heat pattern questionnaire was composed of many questions about patient's physical condition, which were derived from The Traditional Oriental Medical Literature with Delphi Technique. Patients filled out the cold-heat pattern questionnaire by themselves. Diagnosis of cold and heat pattern are conducted separately by oriental medical doctors with more than 5 years' clinical experience. Various physical condition factors were derived for the cold-heat pattern questionnaire. (Preference temperature, Body temperature, Pain type, Face color, Urine, Stool and secretion features) Each cold and heat symptoms group acquired internal consistency. (Cronbach's ${\alpha}$ : Cold - 0.605, Heat - 0.722) There were significant associations between doctor's diagnosis and cold symptoms in 'Aversion to cold', 'Desire for heat', 'Pale face', 'Loose stools'. (p-value < 0.05) There were significant associations between doctor's diagnosis and heat symptoms in 'Desire for cold', 'Body feverishness', 'Thirst'. (p-value < 0.05) The internal consistency results suggest that the cold-heat pattern questionnaire assured reliability. Besides, these results showed that cold-heat symptoms are apt to appear together with, and this can be indirect evidence that diagnosis of cold-heat pattern is valuable for comprehension about disease pattern. Moreover, respective symptoms of cold-heat pattern showed different significance with doctor's diagnosis. Consequently these significant symptoms can be more considered for comprehension of cold-heat pattern.

• Journal of the Korean Society for Heat Treatment
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• v.11 no.2
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• pp.131-139
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• 1998

The object of this research is to estimate the hardenability of quenched carbon steels AISI 1050. The equation of transient heat conduction was analyzed to derive cooling curve by finite element method. The effects of temperature on physical properties, metallic structures and the latent heat by phase transformation were considered. A good agreement was found between analytical and experimental results to show that the proposed numerical procedure was reliable. This procedure could be used as the detabase for optimal condition of heat treatment cycle.

• Journal of the Korean Society for Heat Treatment
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• v.11 no.1
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• pp.27-34
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• 1998

Effects of different heat treatments on microstructure and damping capacity of Cu-55%Mn alloy were investigated to find an optimum heat treatment condition for a maximum damping capacity. The alloy showed the high level of damping capacity in case of the aging at 375 and $400^{\circ}C$. This is ascribed to the FCC${\rightarrow}$FCT martensitic transformation and microstructural changes from mottled to tweed band type. The damping capacity had a maximum value of 0.33 in logarithmic decrement when the alloy was aged at $375^{\circ}C$ for 14 hours followed by 20 times of thermal cycling between room temperature and $250^{\circ}C$. The refinement of tweed structure by thermal cycling is thought to be responsible for the highest damping capacity.