• Journal of the Korean Society for Precision Engineering
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• v.25 no.6
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• pp.47-54
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• 2008

Fitting process carried out in the automobile transmission assembly line is classified into three classes; heat fitting, press fitting, and their combined fitting. Heat fitting is a method that heats gear to a suitable range under the tempering temperature and squeezes it toward the outer diameter of shaft. Its stress depends on the yield strength of gear. Press fitting is a method that generally squeezes gear toward that of shaft at room temperature by a press. Another method heats warmly gear and safely squeezes it toward that of shaft. Warm shrink fitting process for the automobile transmission part is now gradually increased, but the parts (shaft/gear) assembled by this process produced dimensional changes in both the outer diameter and profile of the gear. So that it may cause noise and vibration between gears. In order to solve these problems, we need an analysis of warm shrink fitting process, in which design parameters are involved; contact pressure according to fitting interference between outer diameter of shaft and inner diameter of gear, fitting temperature, and profile tolerance of gear. In this study, an closed form equation to predict contact pressure and fitting load was proposed in order to develop an optimization technique of the warm shrink fitting process and verified its reliability through the experimental results measured in the field and FEM, that is, thermal-structural coupled field analysis. Actual loads measured in the field was in good agreements with the results obtained by the theoretical and finite element analysis.

• Journal of the Korean Wood Science and Technology
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• v.21 no.4
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• pp.64-72
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• 1993

Mechanical properties of 15 mm thick, three-layer particleboard were studied by varying resin content, specific gravity, mat moisture content, pressing time and pressing temperature. Based on the results of the study, Multiple regression models were developed to estimate the mechanical properties of three-layer particleboard. The results of this study showed the mechanical properties of particleboard were highly related with resin content. specific gravity and mat moisture content in decending order. The mechanical properties were able to estimated as the linear function of resin content and specific gravity. However, the effects of change in mat moisture content on the mechanical properties showed a non-linear pattern. The mechanical properties curves over mat moisture content reached peaks at 15 %, and then decreased at 18 % and 21 % of mat moisture contents. On the other hand, the effects of pressing time and pressing temperature on the mechanical properties of particleboard were not significant.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.1
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• pp.37-44
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• 2011

High temperature wear of AlCrN coated tool steels sliding against the ultra-high strength boron steels used for hot press forming has been studied. The sliding wear tests have been carried out using a pin-on-disc of configuration under applied normal load of 50 N for 20 min with heating the ultra-high strength boron steels up to $800^{\circ}C$. Characterizations of tribolayers formed on the contacting surfaces between the tribopairs of the AlCrN coated tool steels and the ultra-high strength boron steels have been studied. It was found on the tribolayers of the AlCrN coated tool steels that microcracking and oxides containing Fe and Cr to increase friction coefficient were formed at the early stage of sliding wear, followed by the generation of the smeared oxide layers containing Fe transferred from the tribopair to decrease friction coefficient. This may mainly contribute to very low specific wear rate of the AlCrN coated tool steels sliding against the ultra-high strength boron steels, resulting from oxideoxide contact between the tribopair.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.6
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• pp.339-344
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• 2009

Recently, Laser surface treatment technologies have been used to improve wear charactenitics and fatigue resistance of metal molding. When the laser beam is irradiated on the surface and laser speed is appropriate, the laser focal position is rapidly heated and the thermal energy of surface penetrates the material after irradiation, finally imbuing it with a new mechanical characteristic by the process of self-quenching. This research estimates the material characteristic after efficient and functional surface treatment using HPDL, which is more efficient than the existing CW Nd:YAG laser heat source. To estimate this, microstructural changes and hardness characteristics of three parts (the surface treatment part, heat affect zone, and parental material) are observed with the change of laser beam speed and surface temperature. Moreover, the depth of the hardened area is observed with the change of the laser beam speed and temperature. From the results of the experiments, it has been shown that the maximum hardness is approximately 788Hv when the heat treatment temperature and the travel speed are $1150^{\circ}$ and 2 mm/sec, respectively.

• Korean Journal of Metals and Materials
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• v.47 no.10
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• pp.667-674
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• 2009

High temperature wear of STD 61 tool steels sliding against the Al-9%Si coated steels used for hot press forming has been studied in comparison with that of the tool steels sliding against the uncoated steels. Wear tests have been performed using a pin-on-disc configuration under an applied normal load of 50N for 20 min with heating the coated and uncoated steels up to 800$^{\circ}C$. It was found on the worn surface of the STD 61 tool steels sliding against the Al-9%Si coated steels that the formation of the glazed layers containing Al transferred from the coated tribopair may contribute to a reduction of the coefficient of friction, and detachment in part occur due to delamination wear, resulting in higher specific wear rate. On the other hand the Fe-oxide wear debris entrapped on the softer surface of the uncoated steels can act as a tribosurface, leading to decreased adhesive wear of the STD 61 tool steels, resulting in a lower specific wear rate.

• Smart Structures and Systems
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• v.15 no.4
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• pp.1159-1175
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• 2015

In this study, the effect of temperature variation on the wireless impedance monitoring is analyzed for the tendon-anchorage connection of the prestressed concrete girder. Firstly, three impedance features, which are peak frequency, root mean square deviation (RMSD) index, and correlation coefficient (CC) index, are selected to estimate the effects of temperature variation and prestress-loss on impedance signatures. Secondly, wireless impedance tests are performed on the tendon-anchorage connection for which a series of temperature variation and prestress-loss events are simulated. Thirdly, the effect of temperature variation on impedance signatures measured from the tendon-anchorage connection is estimated by the three impedance features. Finally, the effect of prestress-loss on impedance signatures is also estimated by the three impedance features. The relative effects of temperature variation and prestress-loss are comparatively examined.

• Structural Engineering and Mechanics
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• v.67 no.4
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• pp.337-346
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• 2018

The purpose of this study is to investigate thermal post-buckling analysis of a laminated composite beam subjected under uniform temperature rising with temperature dependent physical properties. The beam is pinned at both ends and immovable ends. Under temperature rising, thermal buckling and post-buckling phenomena occurs with immovable ends of the beam. In the nonlinear kinematic model of the post-buckling problem, total Lagrangian approach is used in conjunction with the Timoshenko beam theory. Also, material properties of the laminated composite beam are temperature dependent: that is the coefficients of the governing equations are not constant. In the solution of the nonlinear problem, incremental displacement-based finite element method is used with Newton-Raphson iteration method. The effects of the fibber orientation angles, the stacking sequence of laminates and temperature rising on the post-buckling deflections, configurations and critical buckling temperatures of the composite laminated beam are illustrated and discussed in the numerical results. Also, the differences between temperature dependent and independent physical properties are investigated for post-buckling responses of laminated composite beams.

• Smart Structures and Systems
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• v.17 no.6
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• pp.881-901
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• 2016

In this study, a method to compensate the effect of temperature variation on impedance responses which are used for prestress-loss monitoring in prestressed concrete (PSC) girders is presented. Firstly, an impedance-based technique using a mountable lead-zirconate-titanate (PZT) interface is presented for prestress-loss monitoring in the local tendon-anchorage member. Secondly, a cross-correlation-based algorithm to compensate the effect of temperature variation in the impedance signatures is outlined. Thirdly, lab-scale experiments are performed on a PSC girder instrumented with a mountable PZT interface at the tendon-anchorage. A series of temperature variation and prestress-loss events are simulated for the lab-scale PSC girder. Finally, the feasibility of the proposed method is experimentally verified for prestress-loss monitoring in the PSC girder under temperature-varying conditions and prestress-loss events.

• Computers and Concrete
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• v.27 no.1
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• pp.13-20
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• 2021

In this paper, the elevated temperature on a concrete-galvalume composite beam's flexural strength based on the numerical and experimental methods is investigated. The strategy is to perform modeling and simulation of the flexural test based on finite element method (FEM) at room temperature and validate its results to experimental data at the same temperature. When the numerical model was proven valid, the model was utilized to simulate the effect of elevated temperatures on the composite element. The study concludes that the flexural strength of the beam decreases at higher temperature. Additionally, it was shown that cracking moments is susceptible to temperature fluctuation and the failure modes are sensitive concerning the elevated temperature.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.6
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• pp.802-806
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• 2005

The objective of this study was to determine the effects of processing method and rapeseed variety on ruminal and intestinal protein digestibility of rapeseed meal in steers. Intestinal amino acid digestibility was assessed with an in situ ruminal incubation and precision-fed rooster bioassay. In this experiment one traditional rapeseed meal sample (sample A, prepress extraction) and three double low rapeseed meal samples (sample B, prepress extraction, sample C, screw press and sample D, low temperature press) were placed in polyester bags(8 cm${\times}$12 cm) and suspended in the ventral rumen of steers for 16 h. The residues of in situ incubations were intubated to roosters. Total excreta were collected for 48 h after incubation and then desiccated and amino acid concentrations were determined. Results showed that in ruminal incubation the degradation rate of amino acid and crude protein was higher for traditional rapeseed meal sample A than for double low rapeseed meal sample B, but was much lower than for double low sample C and D. In the group of double low rapeseed meal samples, sample D processed by low temperature press had the highest degradation rate of amino acids in the rumen. For all amino acids, the digestibility of the residual protein as measured by the precision-fed rooster bioassay tended to be lower for sample B than for sample A, which had the same processing method with sample B, and in the group of double low rapeseed meals, sample B had similar digestibility of amino acid in residual protein to sample D and higher than that of sample C. However, although the total amino acid availability involving the digestibility of amino acids in the rumen and rooster bioassay of double low rapeseed meal sample D (low temperature press) was higher than those of the other three samples by 7 to 9 percent, there were no significant differences. Results indicated that processing method markedly affected ruminal and post ruminal amino acid digestibility of rapeseed meal when the temperature exceeded 110$^{\circ}C$. Rapeseed meal that had a high content of fiber was not suitable for dry heat treatment at higher temperatures or the amino acids digestibility in rumen and total availability of amino acids could be reduced. Results also suggested the variety of rapeseed meal had no significant effect on the digestibility and availability of amino acids.