• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.12
• /
• pp.1132-1139
• /
• 2008

The aim of this study is to apply shape optimization technique for the repair of aging airframe components, which may extend fatigue life substantially. Free-form optimum shapes of a cracked part to be reworked or replaced are investigated with the objective to minimize the peak local stress concentration or fatigue-damage. Iterative non-gradient method, which is based on an analogy with biological growth, is employed by incorporating the robust optimization method to take account of the stochastic nature of the loading conditions. Numerical examples of optimal hole shape in a flat plate are presented to validate the proposed method. The method is then applied to determine the reworked or replacement shape for the repair of a cracked rib in the rear assembly wing body of aircraft.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.40 no.1
• /
• pp.114-130
• /
• 2016

This research provides practical data to develop UV protection masks and dust protection masks. It surveyed uncomfortable factors and significant characteristics for masks. It used 653 subjects 20-79 years old and performed the research from April to May in 2014. Wearing masks at outdoor activities is not widely popular yet, but golf players, mountaineers and old people were quite interested in masks. People mainly wore a basic shape mask, but main age group of each mask shape was different. People usually prioritized the protection function and comfort of wearing over design; however, women, young generation and people attending to outdoor activities longer than 1 hour considered design quite important. People going on picnic or camping consider mask characteristics most important. Therefore, various mask shapes and protective functions should be developed to reflect consumer needs. Meanwhile, the discomfort levels of masks were not too high, but old people felt more discomfort than young people. The most discomfort factors were 'other's eye', 'distracting face movement' and 'feeling of foreign object'. They also mentioned falling problem of C shape mask and short-rib shape mask, and asked for a 'tighter fit' at the ear.

• Composites Research
• /
• v.34 no.1
• /
• pp.35-46
• /
• 2021

This paper aims to reduce weight by replacing the reinforcements of the B-pillar used in vehicles with CFRP(Carbon Fiber Reinforced Plastics) and GFRP(Glass Fiber Reinforced Plastics) from the existing steel materials. For this, it is necessary to secure structural stability that can replace the existing B-pillar while reducing the weight. Existing B-pillar are composed of steel reinforcements of various shapes, including a steel outer. Among these steel reinforcements, two steel reinforcements are to be replaced with composite materials. Each steel reinforcement is manufactured separately and bonded to the B-pillar outer by welding. However, the composite reinforcements presented in this paper are manufactured at once through compression and injection processes using patch-type CFRP and rib-structured GFRP. CFRP is attached to the high-strength part of the B-pillar to resist side loads, and the GFRP ribs are designed to resist torsion and side loads through a topology optimization technique. Through structural analysis, the designed composite B-pillar was compared with the existing B-pillar, and the weight reduction ratio was calculated.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.14 no.2
• /
• pp.57-65
• /
• 2010

To determine the static buckling loads and evaluate the structural performance of slender steel pipe-arches such as for greenhouse structures, a series of modal tests using a fixed hammer and roving sensors was carried out, by providing no load, then a range of vertical loads, on an arch rib in several steps. More attention was given to an internal arch where vertical and horizontal auxiliary members are not placed, unlike an end arch. Modal parameters such as natural frequencies, mode shapes and damping ratios were extracted using more advanced system identification methods such as PolyMAX (Polyreference Least-Squares Complex Frequency Domain), and compared with those predicted by commercial FEA (Finite Element Analysis) software ANSYS for various conditions. A good correlation between them was achieved in an overall sense, however the reduction of natural frequencies due to the existence of preaxial loads was not apparent when the vertical load level was about up to 38% of its resistance. Some difficulties related to the field testing and parameter extraction for a very slender arch, as might arise from the influences of neighboring members, are carefully discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.1311-1320
• /
• 2000

In this study, shape memory alloy(SMA) wires and piezoceramic actuators(PZT's) are employed in order to generate higher modes on the beam deformations. Compressive force is generated and applied to the beam by the pre-strained SMA wires attached at both ends of the beam. PZT's apply concentrated moments to several locations on the beam. Combinations of the compressive force and concentrated moments are investigated in order to understand the higher-mode deformation of beams. The first desired mode shape is obtained by controlling the temperature of the SMA wires. The first and third mode shapes are performed experimentally by heating SMA wires up to phase transformation temperature. The adaptive wing is defined as a wing whose shape parameters such as the camber, wing twist and thickness can be varied in order to change the wing shape for various flight conditions. In this research, control of the camber has been studied. The wing model consists of three plates and many ribs. Two of the plates are placed parallel to each other and they are clamped at one edge. Third plate connects the other edges of the parallel plates together. Each rib is made of SMA wire and connected to the parallel plates. It generates concentrated force and applies to the plates in oblique directions. The PZT's are bonded onto the plates and exert concentrated moments upon the plate at several locations. The object of this research is to generate various shape of wing by combining the concentrated forces and moments.

• Elastomers and Composites
• /
• v.44 no.4
• /
• pp.373-377
• /
• 2009

Most of the plastics products are being manufactured by injection molding. Warpage in injection molded affects the product dimension and it causes assembling problem. In this study, warpages in the injection molded part been studied. Specimens are rectangular flat shapes with and without ribs. Amorphous polymers (PC and ABS) and crystalline polymers (PP and PA66) were used for material. Flat shape with ribs showed higher warpage than flat shape without ribs by 6 to 9%. The specimens with ribs that are located parallel to the flow direction has higher warpage than specimens with ribs that are located perpendicular to the flow direction by 25 to 39%. Crystalline polymers have higher warpage than amorphous polymers by 23 to 67%. Warpage decreases as packing time increases and it increases as injection temperature increases.

• Archives of Plastic Surgery
• /
• v.36 no.5
• /
• pp.597-604
• /
• 2009

Purpose: Compound tissue defects remain a challenge to reconstructive surgeons. The objective of this study was to introduce examples of successful reconstruction of compound defects of the head and neck and upper and lower limbs, using chimeric flaps based on the subscapular vascular system. Methods: We report 19 reconstruction cases using chimeric flaps based on the subscapular vascular system. The scapular flap, scapular fascia, scapular bone, parascapular flap, latissimus dorsi, latissimus dorsi perforator flap, latissimus dorsi myocutaneous perforator flap, serratus anterior, serratus anterior fascia, and rib bone were used as components for chimeric flaps. 12 cases had defects of the upper limb, three in the lower limb, three in the head and neck area, and one case had a defect of the thoracoabdominal wall. Results: Defect sizes ranged from $6{\times}8cm$ to $20{\times}22cm$. The component used most often for skin coverage was the latissimus dorsi perforator flap; for soft tissue bulk, the latissimus dorsi; for fascia coverage, the serratus anterior fascia flap; and for bone reconstruction, the scapular bone flap respectively. All cases were successfully reconstructed without additional operative procedures or flap necrosis. Conclusion: Because it is fairly easy to employ vascular pedicles of sufficient length and diameter, enabling the use of diverse types of tissue with various shapes and sizes, the use of chimeric flaps based on the subscapular vascular system allows one - stage reconstruction tailored to the characteristics of the defect area.

• Design & Manufacturing
• /
• v.13 no.1
• /
• pp.5-12
• /
• 2019

In this paper, we studied the micro tool deflection, micro cutting with low temperature, and deformation of micro ribs caused by cutting forces. First, we performed an integrated machining error compensation method based on captured images of tool deflection shapes in micro cutting process. In micro cutting process, micro tool deflection generates very serious problems in contrast to macro tool deflection. To get the real images of micro tool deflection, it is possible to estimate tool deflection in cutting conditions modeled and to compensate for machining errors using an iterative algorithm correcting tool path. Second, in macro cutting fields, the cryogenic cutting process has been applied to cut the refractory metal but, the serious problem may be generated in micro cutting fields by the cryogenic environment. However, if the proper low temperature is applied to micro cutting area, the cooling effect of cutting heat is expected. Such effect can make the reduction of tool wear and burr formation. For verifying this passibility, the micro cutting experiment at low temperature was performed and SEM images were analyzed. Third, the micro pattern was deformed by the cutting forces and the shape error occurred in the sidewall multi-step cutting process were minimized. As the results, the relationship between the cutting conditions and the deformation of micro-structure during micro cutting process was investigated.

• Tuberculosis and Respiratory Diseases
• /
• v.44 no.1
• /
• pp.59-68
• /
• 1997

Background : Tuberculous chest wall abscess is a rare complication of tuberculosis. However, there have been few reports about the variable extents and shapes of tuberculous chest wall abscesses. We analyzed the extent and shape of tuberculous chest wall abscess-es and grouped them according to combined pleuroparenchymal lesions by CT scans. Materials and Methods : CT findings were evaluated in 20 patients of tuberculous chest wall abscesses. We classified 29 abscesses in 20 patients into three types according to pleuroparnechymal lesions. Type 1 was defined when there was no active pleuroparenchymal lesion, Type 2, when intrathoracic tuberculosis was contacted with chest wall abscess, Type 3, when ipsilateral subpleural nodules were not contacted with chest wall abscess. Results : The type 1 included 6 abcesses in 6 patients. They showed rib and/or costal cartilage destruction in their center. They were relatively large and round. The type 2 included 13 abscesses in 10 patients. The abscesses in contact with pleural lesion or mediastinal lesion were mainly located in the outer muscle layer, and they were relatively large in size. However, the abscesses in contact with parenchymal lesion were mainly located in extrapleural space. They were relatively small and they were longest along the long axis of ribs. The type 3 included 10 abscesses in 6 patients. They were located mainly in the extrapleural space. Conclusion : Tuberculous chest wall abscess-es showed variable extents and shapes according 10 pleuroparenchymal lesions. CT is a good diagnostic modality to visualize the extent of tuberculous chest wall abscess and combined pleuroparenchymal lesion.