• Journal of the Korean institute of surface engineering
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• v.45 no.5
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• pp.181-187
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• 2012

The Friction Stir Welding (FSW) has mainly been used for making butt joints in Al alloys. The development of Friction Stir Lap Welding (FSLW) would expand the number of applications. In this study, microstructures and mechanical properties of FSLW in A5052 alloy were investigated under varying rotating speed and probe length. Investigating the characteristics as FSLWed conditions were as below ; Failure Maximum load by shear fracture was increased proportional to the width of joint area, which was increased by input heat, stirring intensity in the case of 2.3 mm probe length. Tensile fracture occurred, and maximum load was determined due to side worm hole of joint area and softening of microstructure in the case of 3.0 mm probe length. In the case of 3.7 mm probe length, material hook and bottom worm hole were appeared at the end interface of joint area. The most sound FSLW condition with no defects was 3.0 mm probe length and 1500 rpm-100 mm/min. No defects were showed in 1500 rpm-100 mm/min and 1800 rpm-100 mm/min, but Vickers microhardness distribution in TMAZ/HAZ which was fracture zone was lower in 1800 rpm-100 mm/min than in 1500 rpm-100 mm/min. In this condition highest tensile strength, 215 MPa (allowable rate 78% of joint efficient) was obtained.

• Steel and Composite Structures
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• v.45 no.6
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• pp.797-818
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• 2022

Steel-precast ultra-high-performance concrete (UHPC) composite beams with demountable high-strength friction-grip bolt (HSFGB) shear connectors can be used for accelerated bridge construction (ABC) and achieve excellent structural performance, which is expected to be dismantled and recycled at the end of the service life. However, no investigation focuses on the demountability and reusability of such composite beams, as well as the installation difficulties during construction. To address this issue, this study conducted twelve push-out tests to investigate the effects of assembly condition, bolt grade, bolt-hole clearance, infilling grout and pretension on the crack pattern, failure mode, load-slip/uplift relationship, and the structural performance in terms of ultimate shear strength, friction resistance, shear stiffness and slip capacity. The experimental results demonstrated that the presented composite beams exhibited favorable demountability and reusability, in which no significant reduction in strength (less than 3%) and stiffness (less than 5%), but a slight improvement in ductility was observed for the reassembled specimens. Employing oversized preformed holes could ease the fabrication and installation process, yet led to a considerable degradation in both strength and stiffness. With filling the oversized holes with grout, an effective enhancement of the strength and stiffness can be achieved, while causing a difficulty in the demounting of shear connectors. On the basis of the experimental results, more accurate formulations, which considered the effect of bolt-hole clearance, were proposed to predict the shear strength as well as the load-slip relationship of HSFGBs in steel-precast UHPC composite beams.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.10a
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• pp.197-202
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• 1997

• Textile Coloration and Finishing
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• v.22 no.1
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• pp.8-13
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• 2010

Needle contamination was investigated using a test rig simulated the knitting points in the knitting machine in relation with the characteristics of knitting yarn such as yarn type and moisture contents. When used open-end yarn compared with combed and carded ring-spun yarns, the needle contamination was significantly increased because of the higher friction between yarn and needle by the fly and other impurities. Also Lower moisture content of the yarns aggravated the needle contamination. In addition knitting yarn breakage was substantially influenced by the higher needle contamination.

• Journal of the Korean Society of Industry Convergence
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• v.9 no.1
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• pp.5-11
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• 2006

This study was performed to determine the effect of structural characteristics of selected wool fabrics on mechanical and thermal properties. 52 wool fabrics, including 18 plain woven fabrics and 34 twill and satin woven fabrics were used as samples woven with various weft density for the study. Several physical characteristics such as mechanical properties, keeping warmth ratio of wool fabrics were measured. Data analyses including 1) analysis of tactile and thermal comfort sensation were performed. the following were obtained from the results: The main factors affecting keeping warmth ratio were thickness and bulk density. The keeping warmth ratio of samples increased with increasing thickness and decreasing bulk density of samples. In addition, coefficient of friction of the samples increased with keeping warmth ratio of samples. The above results show that wearing sensation and comfort properties of fabrics are changed depending on the end-use, and thus, above results can be used to manufacture of fabrics for specific end-use with high comfort properties.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.04a
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• pp.65-68
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• 1991

Finite element analysis is used to study the role of interfacial properties on the bond strength of reinforcing steel to concrete. Specifically, the role played by epoxy coatings on the failure of standard beam-end specimens is explored. Experimental results show that epoxy coatings reduce bond strength, but that the effect is dependent on the bar size and the deformation pattern. The finite element model for the beam-end specimen includes representations for the deformed steel bar, the concrete, and the interfacial material. The interface elements can be varied to match the stiffness and friction properties of the interfacial material. Cracking within the concrete is represented using Hillerborg's ficticious crack model. The model is used to study important aspects or behavior observed in the tests and to provide an explanation for the effect of the various test parameters.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.358-364
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• 1998

Lubricational characteristics at the interface between the piston ring and the cylinder liner are considered in this paper. To verify that surface shape and operating conditions of the engine can affect the state of lubrication, the changes of the minimum film thickness and friction force are calculated with various conditions. Oil starvation and open-end boundary condition are used to determine computational boundaries as reported on previous paper for lubrication analysis for the piston ring. From this analysis, it can be found that lubricational characteristics are seriously affected by degree of oil starvation, surface shape and operating conditions.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.6
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• pp.717-726
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• 2007

Fully-grown flocs in a mixing tank of membrane filtration with dead-end membrane are ruptured while passing through a pump and the ruptured flocs are aggregated again in a Membrane-Feed-Pipe (MFP). To look at more details, this study tries to relate the reaggregation to a parameter of mixing intensity in MFP, i.e., G-value. The G-value is a function of Reynolds number, pipe diameter, friction factor and average velocity in MFP. To deal with polydispersity condition, we develop a representative particle size called in this study EDPD (Effective Diameter for Polydispersity condition in Dead-end filtration). The experimental results show that as the G-value increases, the EDPD decreases and also the cake resistance increases. Through comparison between EDPD and cake resistance, these results show that cake resistances are controlled by reaggregation phenomenon in MFP. The effect of detention time in MFP, however, does not affect the reaggregation of the broken flocs as G-values are increased.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.4
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• pp.151-157
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• 2003

A new type of precision actuator is developed using piezoelectric bimorphs. This type of actuator is applicable for the flat surface or in-pipe system and can make forward and backward motion. Two bimorphs are linked serially and two different phased voltages are applied to each bimorph. Therefore, The end of the bimorph makes ellipsoidal motion. The device moves by the friction force between the rubber attached at the bimorph end and the inner surface of the pipe. As the results, the driving range of the device is about 0~18Hz and the device guarantees very high linearity at low frequency, 0~1 Hz. The maximum velocity of the device is about 6mm/s at 10Hz. The developed mechanism is very simple and use piezoelectric bimorph. So, it is possible to miniaturize and educe the power consumption.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.5
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• pp.491-497
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• 2009

Of all of pneumatic components utilized in the make up of pneumatic circuits on either automatic assembly machine or industrial equipment, the pneumatic cylinder is more oriented toward being a structural as well as a pneumatic member. The structural design must be based to a large degree on the end of application of the cylinder on the equipment it is operating. In this paper, design studies of a double-acting pneumatic cushion type cylinder with low-friction and high-speed driving have been developed. Of interest here is to investigate the stress and strain analysis of cylinder tube, piston rod, end cover, and to analyze the buckling of piston rod. A finite element analysis is carried out to compute the distribution of the displacement, stress and safety factors by using ANSYS. As a result, the structural safety factors of each parts in pneumatic cushion cylinder are evaluated and confirmed at the design specifications.