• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.47-55
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• 2011

The optimum mold design and the optimum process condition were constructed upon executing process simulation of rubber injection molding with the commercial CAE program of MOLDFLOW (Ver. 5.2) in order to solve the process-problems of K company relating to cracks, which occurs at the inner cavity wall of C. V. joint boots. As a result it was confirmed that the real cracks occurs at the exactly same position of the cavity as exhibits the defects of weld and meld line and unsatisfactory curing according to the result of simulation. In order to prevent the occurrence of weld and meld line at the defect-position, the location of gate was altered to the optimum position of the cavity. Consequently the filling pattern was established to minimize the degree of the melt-fronts confronting or the melt-flows melding to prevent the occurrence of weld and meld line at the defect-position. It was observed that both gate-positions to maximize the degree of the formation of weld and meld line and air traps are located, respectively, in opposite direction each other with reference to the optimum gate position. In addition, the temperature of mold was raised by $10^{\circ}C$ and maintained at $170^{\circ}C$ for satisfactory curing.

• Journal of Welding and Joining
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• v.24 no.1
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• pp.50-55
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• 2006

In an attempt to optimize friction spot joining process of Al alloys for automobiles, effects of joining parameters such as tool rotating speed, plunging depth, and joining time on the joints properties were investigated. A wide range of joining conditions could be applied to join Al alloys for automobile without defects in the weld zone except for certain welding conditions with a lower heat input. For sound joints without defects, tensile shear strength of joints was higher than acceptable criteria of tensile shear strength of resistance spot welded joints for aluminum.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.177-179
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• 2005

In an attempt to optimize friction spot joining Process of Al alloys for automobiles, joining parameters such as tool rotating seed, plunging depth, and joining time on the joints properties were investigated. A wide range of joining conditions could be applied to join Al alloys for automobile without defects in the weld zone except for certain welding conditions with a lower heat input. for sound joints without defects, tensile shear strength of joints was higher than acceptable criteria of tensile shear strength of resistance spot welded joints for aluminum.

• Journal of the Korean Society for Railway
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• v.5 no.2
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• pp.55-60
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• 2002

This study proposes the post-processor simulator construction of ultrasonic signal for integrity evaluation of railway truck. For these purposes, the ultrasonic signals for defects(crack) of weld zone in frames are acquired in the type of time series data and echo strength. The detection of the natural defects in railway truck is performed using the characteristics of echodynamic pattern in ultrasonic signal. The constructed post-processor simulator agree fairly well with the measured results of test block(defect location, beam propagation distance, echo strength, etc). Proposed post-processor simulator construction of ultrasonic in this study can be used for the integrity evaluation of railway truck.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.230-237
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• 2015

To improve productivity and improve the welding process, we have studied the automated system of the weld by applying a tandem welding. Then, the speed of the welding process is improved, production of industries is increasing. Productivity of the industrial sector has increased the application of tandem welding for automated system of welding. But quality assurance for the product take place welding defects in the welding process because the speed of the process is increased. Definitive research solutions an dit's actuality, however, there is insufficient. Accordingly, it is a situation that the performance of the weld to ensure quality of the weld is required urgently after the welding process. Comparing and analyzing the results of passing each experiment of the two-electrode welding and the welding electrode1, a study attempted to quality assurance of the welded joint portion.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2596-2601
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• 2009

Gouging is defined as the removal of weld metal and base metal from the opposite of a partially welded joint to facilitate complete joint penetration. Since the work by current method needs skillful welding and grinding, there is a limit on the increase of operation efficiency. Noise and dust from the weld gouging also deteriorate the work place and cause environmental problems. In this study, the gouging work by cutting method is proposed to overcome the defects from weld gouging such as low productivity, severe noise, dense dust, and so on. The developed cutting gouging system removes material as much as $13,565mm^3/min$, and enlarge the labor productivity as three times compared to that by weld gouging method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.2
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• pp.1-8
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• 2000

An attempt was made to develop commercially pure titanium frames of glasses with a high-precision laser beam welding machine, in which a resonator with 12kw of the peak power and 200 W of maximum mean power has the capacity of variable in the range of 0.08~10 ms pulse width. In addition the optical fiber beam transmission with 400 ${\mu}{\textrm}{m}$ of the core diameter and a weld chamber to contain specimens in the inert gas atmosphere were also designed and used. In the present study. titanium frames of glasses parts such as temple plus spring hinge. bridge and top bar were experimentally manufactured by utilizing the optimum welding parameters with the optical fiber of GI 400 ${\mu}{\textrm}{m}$, 2.9J energy per pulse, and focussing position for Tee and butt joints. The titanium welded joints with laser beam welding did not reveal any severe weld defects or weld bead appearance except some pores in the weld section.

• Journal of Welding and Joining
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• v.28 no.5
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• pp.45-50
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• 2010

The fatigue crack growth characteristics of base metal and weld joint of 9% Ni steel for LNG storage tank was carried out using CT specimen at room temperature and $-162^{\circ}C$. Fatigue crack growth rate of base and weld metals at RT and $-162^{\circ}C$ was coincided with a single line independent of the change of stress ratio and temperature. In the region of lower stress intensity factor range, fatigue crack growth rate at $-162^{\circ}C$ was slower than that at RT, and the slop of fatigue crack growth rate at $-162^{\circ}C$ increased sharply with propagating of fatigue crack, fatigue crack growth rate at RT and $-162^{\circ}C$ was intersected near the region of $2{\times}10-4\;mm$/cycle, and after the intersection region, fatigue crack growth rate at $-162^{\circ}C$ was faster than that at RT. The micro-fracture mechanism using SEM shows the ductile striation in the stable crack growth region. Also the defects of weld specimen after fatigue testing were detected using the A scan of ultrasonic apparatus.

• Journal of Welding and Joining
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• v.2 no.1
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• pp.30-40
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• 1984

Moisture content in the coating of an electrode is known to cause defects such as porosities, fish eyes and cracks in the weld metal, however, quantitative relationship between them is not clearly understood. In this study widely consumed and the most common type of arc welding rods such as ilmenite and low hydrogen type were chosen for the investigation, and attempts were made to correlate the relationship between the mechanical properties and gas contents when welding was carried out with electrodes of various moisture contents. As the relative humidity changed from 70% to 92%, it was determined that moisture content to reach saturation was in the range of 0.6~6.8%. As the moisture content in the electrode coating was increased, the amount of gaseous components (H, O, N) in the weld metal was accordingly increased, especially diffusible hydrogen showed prominent effect, i.e. it increased proportionally to the increase of the moisture content. The mechanical properties of the weld metal was observed to become more inferior as the diffusible hydrogen was greater. It was determined for ilmenite type of electrode that the increase of hydrogen content was approximately 1.8ml per unit weight percent increase of moisture and also tensile strength resulted lowering from $45.3kg/\textrm{mm}^2$ to $42.7kg/\textrm{mm}^2$ as moisture content increased from 0.7% to 6.8%. For low hydrogen type the increase of the hyrogen was about 2.4ml per unit percent of moisture and tensile strength decreased from $63.0kg/\textrm{mm}^2$ to $53.8kg/\textrm{mm}^2$ particularly in the region of moisture content 0.1~4.2%.

• Structural Engineering and Mechanics
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• v.38 no.4
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• pp.443-457
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• 2011

The loss of strength in a structure as a result of cyclic loads over a period of life time is an important phenomenon for the life-cycle analysis. Service loads are accentuated at the areas of stress concentration, mainly at the connection of components. Structural components unavoidably are affected by defects such as surface scratches, surface roughness and weld defects of random sizes, which usually occur during the manufacturing and handling process. These defects are shown to have an important effect on the fatigue life of the structural components by promoting crack initiation sites. The value of equivalent initial flaw size (EIFS) is calculated by using the back extrapolation technique and the Paris law of fatigue crack growth from results of fatigue tests. We try to analyze the effect of EIFS distribution in a multiple site damage (MSD) specimen by using the extended finite element method (XFEM). For the analysis, fatigue tests were conducted on the centrally-cracked specimens and MSD specimens.