• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.310-313
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• 2007

In roll forming process, a sheet metal is continuously progressively formed into a product with required cross-section and longitudinal shape, such as a circular tube with required diameter, wall-thickness and straightness, by passing through a series of forming rolls in arranged in tandem. In this process, each pair of forming rolls installed in a forming machine play a particular role in making up the required cross-section and longitudinal shape of the product. In recent years, that process is often applied to the bumper rail in the automotive industries. In this study, a optimal roll flower model and proper roll-pass sequence can be suggested by analyzing courcenter strain and longitudinal strain according to the roll-pass with FEM simulation. And also effects of the process parameters on the final shape formed by roll forming defects a evaluated.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.5
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• pp.119-127
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• 2008

In this paper, the influence of the stamping effect is investigated in the performance analysis of a side structure. The analysis covers the performance evaluation such as the crashworthiness and NVH. Stamping analyses are carried out for the center pillar and the side sill made of high strength steels. Then, numerical simulations are carried out in order to identify the stamping effect on the crashworthiness, the natural frequency and the normal mode. The result shows that the analysis of the side structure considering the forming history leads to a different result from that without considering the forming effect. The variation of the system response fully reveals effects of thinning and hardening of members on the performance prediction of vehicle parts. The analysis results demonstrate that the design of auto-body members should be carried out considering the stamping history for accurate assessment of various performances.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.28-36
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• 1998

This investigation is the result of a structural analysis by the finite element method and static loading test for the optimal structural design of an electric railway vehicle made of stainless 301L materials. We analyzed the stress and displacement of the existing electric car-body structure for predicting the position of concentrated stress, the flow of stress, rigidity to be occurred in the car-body structure when it is subjected to the vertical load. It was exposed that the side sills and window corners around the bolsters are the weak parts of the electric car-body structure because the bolsters of the electric car-body structure were subjected to the vertical load and dynamic load to be occurred during running. The flow of stress and the cause of stress concentration in the weak zone were studied in order to prevent the concentration of stress and buckling. The rearrangement of the structure and the selection of the beam elements were also carried out for optimum design of the structure.

• Transactions of Materials Processing
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• v.23 no.6
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• pp.380-385
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• 2014

An analysis procedure is proposed to improve the prediction accuracy of springback as well as to evaluate the structural stability of the tooling used for fabricating a side sill part from UHSS. The analysis couples the stamping analysis and the subsequent analysis of the tool structural. The deformation and stress results for the tool structure are obtained from the proposed analysis procedure. The results show that the amount of deformation and stresses are so high that the tool structure must be reinforced and the tooling design must consider structural stability. Springback is predicted with CAE in order to compare the prediction accuracy between the given tool geometry and the geometry from the structural analysis. The simulation results with the deformed tool can predict the experimental springback tendency accurately.

• Korean Journal of Cleft Lip And Palate
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• v.10 no.2
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• pp.97-108
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• 2007

For many years a wide variety of surgical techniques for closure of cleft lip has been used. Still many surgeons prefer the Millard's rotation-advancement lip repair because the surgical scar is masked in the philtral crest and the nostril floor, and it improves the relationship of the alar base of the cleft side, producing harmonious symmetry of the nostril and the nostril sill. In addition, it uses and preserves the lip anatomy, returning lip tissue into its normal position, minimizing the amount of tissue that is discarded, and reconstructing the orbicular oris muscle. One of the major disadvantages of this procedure is the lack of accurate measurements. The object of this study is to help in the cleft lip surgery with investing its features and design.

• Journal of the Korean Society for Railway
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• v.9 no.3 s.34
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• pp.251-256
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• 2006

This paper explains manufacturing process, analysis and experimental studies on a hybrid composite carbody of Korean tilting train. The composite carbody with length of 23m was manufactured as a sandwich structure composed of a aluminium honeycomb core and woven fabric carbon/epoxy faces. In order to evaluate deformational behavior of the composite carbody, the static load test under vertical load has been conducted. From the test, the vertical deflection an겨 cross sectional deformation of the carbody were analysed and measured. The maximum deflection along the side sill was 9.25mm in the experiment and 8.28mm in the analysis. The maximum cross sectional deformation was measured 5.42mm at carbody center in lateral direction and 4.06mm at roof center in vertical direction.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.10
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• pp.1111-1117
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• 2013

In this paper, the shape accuracy of the stamped hat-type product is quantified and analyzed with ultra high strength steel (UHSS) sheets. The shape of the hat-type product is designed in order to simplify the geometry of the side sill and the stamping methodology is proposed in order to verify the effect of the stamping procedure on the springback amount. Experiments and finite element analyses are conducted with four kinds of the forming sequences. The springback amounts are measured and compared according to the forming procedure with the embossing shape. Experimental result in company with analysis one illustrate that the springback amount is reduced with embossing in the padding operation. They also fully demonstrates the proposed forming procedure and the analysis method can be effectively applied to the process design for producing parts with ultra high strength steel.

• Archives of Plastic Surgery
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• v.44 no.3
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• pp.210-216
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• 2017

Background In treating minor-form or microform cleft lip, obtaining an optimal result is a challenge because of the visible scarring caused by traditional surgery. We present a refined method using muscle overlapping with a minimal skin incision in patients younger than 3 years, a group characterized by thin muscle. Methods The surgical technique involves restoration of the notched vermillion using Z-plasty, formation of the philtral column using overlapping of an orbicularis oris muscle flap through an intraoral incision, and correction of the cleft lip nasal deformity using a reverse-U incision and V-Y plasty. A single radiologist evaluated ultrasonographic images of the upper lip. Results Sixty patients were treated between September 2008 and June 2014. The age at the time of operation ranged from 6 to 36 months (mean, 26 months). The follow-up period ranged from 8 to 38 months (mean, 20 months) in minor-form cases and from 14 to 64 months (mean, 37 months) in microform cases. A notched cupid's bow was corrected in 10 minor-form cases and 50 microform cases. Ultrasonographic images were obtained from 3 patients with minor-form cleft lip and 9 patients with microform cleft lip 12 months after surgery. The average muscle thickness was 4.5 mm on the affected side and 4.1 mm on the unaffected side. Conclusions The advantages of the proposed procedure include the creation of an anatomically natural philtrum with minimal scarring. This method also preserves the continuity and function of the muscle and provides sufficient augmentation of the philtral column and nostril sill.

• Korean Journal of Cleft Lip And Palate
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• v.10 no.2
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• pp.67-74
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• 2007

After Tennison introduced a triangular flap method which, for the first time, preserved the Cupid's bow, Randall gave this method a sound mathematical basis. This method is also called as an inferior triangular cheiloplasty which is characterized by making a small triangular flap from the lateral border of cleft destined to be fitted into an incision on the medial side of cleft. He postulated that the height obtained was equal to the sum of the median of the two triangles used in the cheiloplasty. Using this technique, a 22 month-old male patient with incomplete unilateral cleft lip was corrected primarily. The deviation of the columella and flattening of the nostril on the cleft side were minimal. The operation was done under general anesthesia and patient was healed uneventfully. We tried to improve the symmetry and esthetic feature of philtrum, nostril sill, alar-facial groove, preventing the notch formation on the nostril floor, and to reconstruct the muscle sling in the upper part of lip. The shape of Cupid's bow was restored, and the symmetry of columella was regained as a result. In summary, the inferior triangular cheiloplasty is effective to correct the primary unilateral cleft lip, results in the restoration of favorable anatomy and function.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.34 no.2
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• pp.133-139
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• 2012

This is a review regarding Mulliken's Modification using the Millard rotation-advancement principle for the repair of unilateral complete cleft lip and nasal deformity. All patients underwent prior labionasal adhesion and dentofacial orthopedics with a pin-retained (Latham) appliance used for infants with a cleft of the lip and palate. Technical variations concerning the operation are described. A high rotation and releasing incision in the columella lengthens the medial labial element and produces a symmetric prolabium with minimal transgression of the upper philtral column through the advancement flap. The orbicularis oris muscle is everted, from caudad to cephalad, to form the philtral ridge. A minor variation of unilimb Z-plasty is used to level the cleft side of Cupid's bow handle, and cutaneous closure proceeds superiorly from this junction. The dislocated alar cartilage is visualized though a nostril rim incision and suspended to the ipsilateral upper lateral cartilage. Symmetry of the alar base is addressed in three dimensions, including maneuvers to position the deviated anterior-caudal septum, configure the sill, and efface the lateral vestibular web. The authors believe the technical refinements described herein contribute favorably to the outcome of repair regarding unilateral cleft lip and nasal distortion.