• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.25 no.5
• /
• pp.329-337
• /
• 2016

The demand for the eco-friendly vehicles is skyrocketing because of the increasing $CO_2$ emissions and global warming. In the industrial field, the battery process, a core part of an eco-friendly vehicle, is drawing increased attention; its weight lightening as well as high energy density are becoming increasingly important. In this study, pure Ni plates that were used as the battery pole plate were welded using the laser. The lab joint welding was conducted on ten pure Ni plates at a laser power of 1900 W and a feed speed of 2.8-3.4 m/min. As observed in the experiment, a faster feed speed reduced the bead width, but the laser did not penetrate all ten specimen plates. In addition, pores were trapped when protective gas was used, but they were not trapped when the welding was conducted in atmospheric condition.

• Journal of Korean Society of Steel Construction
• /
• v.10 no.2 s.35
• /
• pp.291-301
• /
• 1998

This paper is a study on the structural behavior of CFCT(Concrete-Filled Circular Tubular) column to H-beam connections with longitudinal rib. The important parameters are being longitudinal rib or not. variable column thickness(5.8mm. 9.2mm. 12.0mm. 15.0mm) around the joint between CFCT and H-beam and the width of flange to diameter. Test results are summarized for the strength, initial stiffness, failure mode and energy absorption capacities of each specimen. These are compared with the theoretical results(Yield line theory, numerical analysis). Therefore, the purpose of this paper is to investigate the stiffness and the strength of connections to evaluate the structural behavior of the CFCT column to H-beam connections with longitudinal rib.

• Journal of Welding and Joining
• /
• v.30 no.5
• /
• pp.22-26
• /
• 2012

Butt-joints of A6061-T6 and AZ31 plates were successfully manufactured by using a friction stir welding method. Off-set free joints and off-set joints were fabricated to investigate the effect of the tool plunge position on the mechanical properties of the joints. Hardness test, tensile test and charpy impact test was performed to evaluate the mechanical properties of the joints. Off-set condition resulted in increase of mechanical properties of the joints. The variation of the hardness distribution in the SZ was also stabilized in the off-set condition. Tensile strength of the off-set joint was about 85% against to that of the AZ31 base metal. Impact absorption energy by Charpy-Impact-Test of the off-set joint also increased by almost 2 times against to that of the AZ31 base metal.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.2 no.2
• /
• pp.75-82
• /
• 1990

A Wave transformation including wave breaking in shallow water region is a non-linear and discontinuous Phenomenon. Therefore, a so-called individual wave analysis (or a wave by wave analysis) rather than spectral approach seems to be adequate to investigate the wave transformation in such regions. In this study, a theoretical joint distribution of wave height, period and wave direction of zero-down crossing waves, which is required in the individual wave analysis in the shallow water region, is derived based on the hypothesis that sea surface is a Gaussian stochastic process and that a band-width of energy spectra is sufficiently narrow. The derived i oint distribution is found to be an effective measure to investigate characteristics of three-dimensional random wave field in shallow water through field measurements.

• Journal of muscle and joint health
• /
• v.12 no.1
• /
• pp.48-56
• /
• 2005

Purpose: This study was measured to the bone mineral density(BMD) and biochemical bone markers in young women in order to identify the relationship between bone mineral density and biochemical bone markers. Methods: Forty two healthy young women were enrolled. BMD were checked Dual Energy X-ray Absorptiometry and biochemical bone markers were checked ELSA-OSTEO(CIS bio international, France)analyzed kit, Pyrilinks-D(Metra Biosystems Inc., U.S.A)analyzed kit. Data were analyzed with frequencies, percentages, means, and Pearson correlation coefficients. Results: 1) Young women forearm(radius & ulnar) BMD was $0.55g/cm^2$, lumbar($1{\sim}4$) BMD was $0.92g/cm^2$, neck of femur BMD was $0.75g/cm^2$, trochanter of femur BMD was $0.61g/cm^2$, ward's triangle of femur BMD was $0.68g/cm^2$. In biochemical bone marker, Osteocalcin was 21.94ng/ml, Deoxypyridinoline was 11.94nmol/nmolCr. 2) There was no significant correlation between BMD and biochemical bone markers. Conclusion: Results not indicated association between bone mineral density and biochemical markers. As seen in the small sample, future research on BMD and biochemical markers need to studies to the large sample.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.400-405
• /
• 2004

In this study, the optimal welding condition of the input power was selected experimentally through the ERW simulator, which is equal to welding status of ERW part in pipe. This condition is the input power 250kW in the heat treatment of the $900^{\circ}C$ normalizing derived from the nondestructive technique and impact energy. In order to evaluate the variation of the fatigue life in the pipe, fatigue surface crack growth test of base and optimal welded metal were performed statistically. As stress intensity factor range (${\Delta}K_s$) increases, the fatigue crack propagation rate (da/aN) of the base metal is faster than that of the welded joint. The variation of the fatigue life in the ERW pipe was estimated statistically using Monte-Carlo simulation with the standard deviation of material constants (C and m) of the paris law in the specimen.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.6 s.261
• /
• pp.694-700
• /
• 2007

Recently, a new cellular metal, WBK(Wire woven Bulk Kagome) has been introduced. WBK is fabricated by assembling metal wires in six directions into a Kagome-like truss structure and by brazing it at all the crossings. Wires as the raw material are easy to handle and to attain high strength with minimum defect. And the strength and energy absorption are superior to previous cellular metals. Therefore, WBK seems to be promising once the fabrication process for mass production is developed. In this paper, an upper bound solution for the mechanical properties of the bulk WBK under compression is presented. In order to simulate uniform behavior of WBK consisted of perfectly uniform cells, a unit cell of WBK with periodic boundary conditions is analyzed by the finite element method. In comparison with experimental test results, it is found that the solution provides a good approximation of the mechanical properties of bulk WBK cellular metals except for Young's modulus. And also, the brazing joint size does not have any significant effect on the properties with an exception of an idealized thin joint.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.1
• /
• pp.56-63
• /
• 2007

In case of bus rollover, the body structure of the bus should be designed to ensure the survival space for passengers. So, this study focuses on evaluating rollover strength through a computer simulation using the commercial code, LS-DYNA3D at the initial stage of vehicle development. For this study, section structure was modeled using a simple beam element, and impact boundary conditions required by ECE(Economic Commission for Europe) regulation No.66 were applied. In order to confirm the validity of the beam element bus model, the results compared with the test results and shell element bus model. The analysis errors from beam element bus model are due to the difference in strain energy of joint area between beam and shell model. In this study, a method for the joint modeling was suggested by using nonlinear springs to which the collapse mechanisms were applied.

• Journal of the Korea Institute of Building Construction
• /
• v.14 no.2
• /
• pp.163-169
• /
• 2014

Engineers in the construction field have been using bonded waterproofing sheets in an attempt to resolve the imbalance in the quality, the risk of fire, safety of workers, and environmental pollution, as well as to eliminate separate use of organic adhesives on the surface of concrete. Recently, self-laminated waterproofing sheets have been developed. The purpose of this research is to find an appropriate processing speed according to the changes in physical properties, and visual observation of the waterproofing sheets laminated by the aluminum thin-film and viscosity layer that can be attached through self-adhesiveness on the surface of concrete and waterproofing sheets. Therefore, this research is conducted using a physical performance test. Based on the result of the test, when the high-frequency inductive heating apparatus was used, an improved adhesion and bonding stability effect were confirmed after the anti-hydrostatic pressure and bond strength in the temperature condition, and the surface observation in the processing speed condition.

• Journal of muscle and joint health
• /
• v.19 no.3
• /
• pp.350-361
• /
• 2012

Purpose: The purpose of this study is to explore the level of bone mineral densities of the femur neck and to identify factors affecting bone mineral density of the femur in Parkinson's disease (PD) patients. Methods: Participants were 121 PD patients visiting the outpatient clinic of D University Hospital in B City. Bone mineral density was measured at the femur neck by using a dual-energy x-ray absorptiometry. The serum vitamin D level, the amounts of milk intake, caffeine intake, cigaret smoking, and alcohol consumption, and the number of steps taken daily were measured. Past and present disease history, the medication history, and duration of the disease were also collected. The level of disability was obtained by neurologists using the Hoehn and Yahr stage and the Unified Parkinson's Disease Rating Scale. Results: Among PD patients, 57% had osteopenia and 15.7% had osteoporosis. The bone mineral density of the femur was associated with weight, serum vitamin D level, age, and working status. Conclusion: The identification of weight and serum vitamin D level as important predictive factors emphasizes the importance of balanced nutrition for PD patients.