• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.53-58
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• 1996

This paper deals with the bending fatigue strength of sintering spur gears. The test specimens are used to sintering spur gear to be consisted of Fe-C-Ni-Mn and SCM415 spur gear. The fatigue test at a constant stress amplitude is performed by using an electrohydraulic servo-controlled pulsating tester. The S-N curves are obtained and the enhancement of fatigue strength due to carburized treatment is clarified, Accordingly, this study presents the fatigue strength of sintering spur gear, SCM415 spur gear and carburized gears of them. The strength enhancement due to the carburized treatment is discussed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.184-187
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• 2005

Forging process is one of the forming process and is used widely in automobile parts and manufacture industry. Especially the gears like spur gear, helical gear, bevel gear were produced by machine tool, but recently they have been manufactured by forging process. The goal of this study is to study forming process with data obtained by comparison between forward extrusion and upsetting simulation results and formability improvement by various heat treatment conditions. By analysis data of 3D FEM by upsetting and forward extrusion forming, the forming process of clutch gear develops using data based on 3D FEM analysis. Through tensile test using specimens by various heat treatment conditions, the optimal heat treatment condition is obtained by comparison the results of tensile test.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.8
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• pp.106-112
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• 1999

It is very important to have exact informations on the properties and characteristics of the sintered steel as a new material of machine elements. The bending fatigue tests are performed for the sintered steel bend specimens of various densities 6.6 to 7.0 g/$cm^3$ and the sintered spur gear to consisted of Fe-Cu-C. The fatigue test at a constant stress amplitude is performed by using an electrohydraulic servo-controlled pulsating tester. Consequently, the S-N curves are obtained. The fatigue strength S for fatigue life N of the specimen with the initial length of crack ai is simulated, and they are shown as N-S-A curves. This study investigate the crack growth characteristics by experiments and present crack growth simulation method for sintered gear

• Tribology and Lubricants
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• v.35 no.1
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• pp.1-8
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• 2019

Demand for plastic gears are increasing in many industries due to their low production cost, light weight, applicability without lubricant, corrosion resistance and high resilience. Despite these benefits, utilizing plastic gears is limited due to their poor material properties. In this work, DLC coating was applied to improve the tribological properties of polyamide66 gear. 0 V, 40 V, and 70 V of negative bias voltages were selected as a deposition parameter in DC magnetron sputtering system. Pin-on-disk experiment was performed in order to investigate the wear characteristics of the gears. The results of the pin-on-disk experiment showed that DLC coated polyamide66 with 40 V of negative bias voltage had the lowest friction coefficient value (0.134) and DLC coated PA66 with 0 V of negative bias voltage showed the best wear resistance ($9.83{\times}10^{-10}mm^3/N{\cdot}mm$) among all the specimens. Based on these results, durability tests were conducted for DLC coated polyamide66 gears with 0 V of negative bias voltage. The tests showed that the temperature of the uncoated polyamide66 gear increased to about $37^{\circ}C$ while the DLC coated gear saturated at about $25^{\circ}C$. Also, the power transmission efficiency of the DLC coated gear increased by about 6% compared to those without coating. Weight loss of the polyamide66 gears were reduced by about 73%.

• Transactions of Materials Processing
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• v.4 no.1
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• pp.9-16
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• 1995

Model material technique, which requires only the small space of experimental set-up and low cost for experiment, is used to estimate the deformed profile and the forging load in rotary forging. The materials and working conditions are determined to satisfy the similitude conditions between the model test and the prototype test. The model material of the so-called plasticine and the mild steel are chosen as specimens, and they represent almost the same value of strain gardening exponent in the stress-strain relationship. Lubricant in the model test is also carefully selected so that it gives the same frictional conditions at the tool-specimen interface. Experiments for two kinds of specimens are carried out in each testing equipment at room temperatue. From the experiments the deformed dimensions and the forging loads are measured and compared with each other by using the simulation coefficients. It is shown that there are good agreements between the model test and the prototype test. Finally, for verifying the availability of the model material technique this mathod is applied to forging of bevel gear product. the good result is obained which can demonstrate that the model material technique is very efficent for estimating or developing a new process.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.11
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• pp.92-97
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• 2010

The object of this study is to investigate the definite method for pitting damaged surfaces. Pitting is a sort of fatigue damages and it is made by a repetitive load. For a judgment between damages or not, sensing vibrations of test equipment is simple. However, it is not only difficult to observe a growth of pitting but also impossible to detect the juncture of initial pitting. Therefore, a method for the pitting damaged area measuring technique was effectively implemented by Two Roller Machine. The change of surface damaged area was measured by an optical microscope in regular time and calculated by the use of dark and bright ratio of test specimens' pictures taken by optical microscope. In conclusion, S - N Curves gained by Failure rate - Cycle graph was led and the curves are able to be chosen as occasion demands for a failure area percentage.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.1
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• pp.1-6
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• 2001

This study is concerned with the cold forging of sintered preform by rotary forging process and direct powder compacting process. An experiment has been carried out using the rotary powder forging press (500kN) which had been designed and equipped with the rotational conical die inclined to the central axis of the press at certain angle The effect of process variables was observed and measured by several mechanical test, such as hardness distribution density, and microstructure of the specimens. It is found that the highly densified P/M parts can be obtained and this process is very effective for improving quality of the powder products.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.381-382
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• 2006

A comparative study is made on root bending fatigue performance of spur gears and plane bending fatigue performance of notched test bars. R = 0 root bending fatigue tests are made on small spur gears with critical root radius 1.0 mm. The results are compared to plane bending fatigue tests of 0.9 mm radius notched specimens. Results are presented for tests on 4%Ni/2%Cu/1.5%Mo prealloyed PM steel with addition of about 0.6% graphite. Predicted values from the test bars coincide well with the results obtained from the gear root fatigue tests.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1593-1594
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• 2013

• Journal of the Korean Society of Industry Convergence
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• v.22 no.1
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• pp.47-54
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• 2019

An experimental study was conducted on the wear and friction responses in sliding tests of a micro-textured surface on laser pattern (LP) steel as reduction gear material in electric guided vehicle. In this research, the friction characteristics of laser pattern steel under different micro texture density conditions were investigated. The friction tests were carried out at sliding speeds of 0.06 m/s to 0.34 m/s and at normal loads of 2 to 10 N. Photolithography method was used to create the dimples for surface texturing purpose. Four different specimens having different dimple densities of 10%, 12.5%, 15%, and 20% were observed respectively. In this research, friction conditions as shown in Stribeck curve were investigated. Furthermore, the microscopic surface was observed using scanning electron microscope. It was found that the dimple density had a significant role on the friction characteristics of laser pattern steel conditioned as reduction gear material in an agricultural vehicle. The duty number showed that the friction condition was hydrodynamic regime. The best performance was obtained from 12.5% dimple density with lowest friction coefficient achieved at 0.018771 under the velocity of 0.34 m/s and 10N load.