• Tribology and Lubricants
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• v.40 no.4
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• pp.133-138
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• 2024

This study evaluates the structural safety of wind turbine blades, analyzes the behavior of composite laminate structures with and without defects, and assesses surface erosion wear. The NREL 5 MW standard is applied to assign accurate composite material properties to each blade section. Modeling and analysis of the wind turbine blades reveal stable behavior under individual load conditions (gravity, motor speed, wind speed), with the web bearing most of the load. Surface erosion wear analysis in which microparticle impacts are simulated on the blade coating shows a maximum stress and maximum displacement of 14 MPa and 0.02 mm, respectively, indicating good initial durability, but suggest potential long-term performance issues due to cumulative effects. The study examines defect effects on composite laminate structures to compare the stress distribution, strain, and stiffness characteristics between normal and cracked states. Although normal conditions exhibit stable behavior, crack defects lead to fiber breakage, high-stress concentration in the vulnerable resin layer, and decreased rigidity. This demonstrates that local defects can compromise the safety of the entire structure. The study utilizes finite element analysis to simulate various load scenarios and defect conditions. Results show that even minor defects can significantly alter stress distributions and potentially lead to catastrophic failure if left unaddressed. These findings provide valuable insights for wind turbine blade safety evaluations, surface protection strategies, and composite structure health management. The methodology and results can inform the design improvements, maintenance strategies, and defect detection techniques of the wind energy industry.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.254-258
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• 2003

Electronic Speckle Pattern for quantitative evaluation of a impact defect inside of composite material plate are described. The impact on composite material makes inside delamination which is difficult to detect visual inspection and ultrasonic testing due to non-homeogenous structure. This paper proposes the quantitative evaluation technique of defects under real impact. Artificial defects are designed inside of composite plate for development of inspection technique and real defects under impact are inspected and compared with results of visual inspection.

• Composites Research
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• v.32 no.5
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• pp.249-257
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• 2019

In this paper, the buckling behavior of triaxially braided circular arch with monosymmetric open section subjected to three-point bending was studied experimentally and numerically. First, test specimens were manufactured using vacuum assisted resin transfer molding (VARTM). Then the specimen was tested under three-point bending to determine the ultimate buckling strength. Before performing the numerical analysis, effective material properties of the braided composite were obtained through micro-meso scale analysis virtual testing validated with available test results. Then linear buckling analysis and geometrically non-linear post buckling analysis, established to simulate the test setup, were performed to study the buckling behavior of the composite frame. Analysis results were compared with experimentally obtained ones for verification. The effect of manufacturing defects of tow misalignment, irregular surface and resin rich region, and uncertainties during test setup were studied using numerical models. From the numerical analyses performed it was observed that both manufacturing defect and uncertainties had effect on the buckling behavior and strength.

• Archives of Reconstructive Microsurgery
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• v.10 no.1
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• pp.60-63
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• 2001

The reconstruction of the suborbital area followed by resection of skin cancer has been used many methods including skin graft, local flaps, free flaps, and skin expansion. The radial forearm free flap has become a workhorse flap in this area because of its lack of bulk, ease of dissection, malleability, and hairlessness. When the suborbital defect especially including full-thickness defect of lower lid was reconstructed with many free flaps, the ectropion and the deformity of medial and lateral canthal area were common problems encountered as late complication due to gravitational descent. To improve the final aesthetic result in patients with suborbital defect, the radial forearm free flap was elevated as a composite radial forearm - palmaris longus free flap, in which the vascularized palmaris longus london was included and anchored to the periorbital bone with $mitek^{(R)}$ as sling, to suspend the flap against gravity and inferior descent, and thereby creating a more natural cheek contour. Two clinical cases were presented as an example of this procedure. Postoperative results emphasize the importance of suspension sling with palmaris longus tendon using $mitek^{(R)}$ in reconstruction of the suborbital defect with radial forearm free flap.

• Journal of Applied Reliability
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• v.16 no.4
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• pp.338-346
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• 2016

Purpose: The purpose of this research is to improve the reliability of the composite material blades used for the wind power generator, by applying the phased array ultrasonic testing technique out of the many nondestructive test into the blades. Method: The wind power generation composite blades are used, as a case study, in order to evaluate the reliability of the phased array ultrasonic testing technique. Defects that are most likely occurred in the field are injected into the different locations of the three different types of artificial test pieces and then phased array ultrasonic testing technique are applied to evaluate the reliability of its effectiveness. Result: As a result of the analysis of the defect signals by applying the A scan and B scan simultaneously, depth and width of the defect could be obtained. An area of defect was proportional to the amount of energy by color in B scan image. The larger amount of energy, reflected amount of energy was appeared in the order of red, orange, yellow, blue color. Conclusion: The most reliable testing method to detect the defect in composite blades for wind power generation is considered to be the combination of the other destructive testing technique with the phased array ultrasonic testing since the PAUT alone could not detect all range of the defects in the blades.

• Journal of Trauma and Injury
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• v.33 no.1
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• pp.48-52
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• 2020

Composite skull defects in patients with severe head injuries are very challenging to manage. The dilemma when deciding whether to perform a definitive reconstruction is how long to wait for physiological recovery before an intervention complicates the situation. The inability of such patients to tolerate prolonged anesthetic exposure is a driving factor for performing the minimal intervention necessary to facilitate recovery. Herein, we present a case involving the successful immediate reconstructive treatment of a severely head-injured adolescent with a composite scalp defect secondary to trauma. A 14-year-old boy sustained a severe head injury from a motor vehicle accident with a composite scalp defect in the right fronto-parietal region. The frontal lobe was exposed, and the right eye was crushed and devitalized. The patient was deeply unconscious for 3 days, without any significant improvements before reconstructive surgery was proposed due to fear of possible meningitis resulting from the exposure of brain structures. We successfully managed the patient with a fronto-parieto-occipital flap, after which the patient promptly recovered consciousness.

• Smart Structures and Systems
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• v.24 no.6
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• pp.803-812
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• 2019

Triplex composite is an epoxy-bonded joint structure, which constitutes the secondary barrier in a liquefied natural gas (LNG) carrier. Defects in the triplex composite weaken its shear strength and may cause leakage of the LNG, thus compromising the structural integrity of the LNG carrier. This paper proposes an autonomous triplex composite inspection (ATCI) system for visualizing and classifying hidden defects in the triplex composite installed inside an LNG carrier. First, heat energy is generated on the surface of the triplex composite using halogen lamps, and the corresponding heat response is measured by an infrared (IR) camera. Next, the region of interest (ROI) is traced and noise components are removed to minimize false indications of defects. After a defect is identified, it is classified as internal void or uncured adhesive and its size and shape are quantified and visualized, respectively. The proposed ATCI system allows the fully automated and contactless detection, classification, and quantification of hidden defects inside the triplex composite. The effectiveness of the proposed ATCI system is validated using the data obtained from actual triplex composite installed in an LNG carrier membrane system.

• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.304-311
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• 2014

In this paper, we propose a ultra sound inspection technique for automatic defect detection and classification in aircraft composite materials. Using local maximum values of ultra sound wave, we choose peak values for defect detection. Distance data among peak values are used to construct histogram and to determine surface and back-wall echo from the floor of composite materials. C-scan image is then composed through this method. A threshold value is determined by average and variance of the peak values, and defects are detected by the values. PCA(principal component analysis) and QDA(quadratic discriminant analysis) are carried out to classify the types of defects. In PCA, 512 dimensional data are converted into 30 PCs(Principal Components), which is 99% of total variances. Computational cost and misclassification rate are reduced by limiting the number of PCs. A decision boundary equation is obtained by QDA, and defects are classified by the equation. Experimental result shows that our proposed method is able to detect and classify the defects automatically.

• Journal of Periodontal and Implant Science
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• v.32 no.4
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• pp.753-767
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• 2002

The purpose of this study was to evaluate histologically the effect of LiF-maleic acid added calcium aluminate(LM-CA) bone cement & CA-PMMA composite bone cement on the healing of calvarial defect in Sprague-Dawley rats. The critical size defects were surgically produced in the calvarial bone using the 8mm trephine bur. The rats were divided in three groups : In the control group, nothing was applied into the defect of each rat. LM-CA bone cement was implanted in the experimental group 1 and CA-PMMA composite bone cement was implanted in the experimental group 2. Rats were sacrificed at 2, 8 weeks after surgical procedure. The specimens were examined by histologic analysis, especially about the bone-cement interface and the response of surrounding tissue. The results are as follows; 1. In the control group, inflammatory infiltration was observed at 2 weeks. At 8 weeks, periosteum and duramater were continuously joined together in the defect area. But the center of defect area was filled up with the loose connective tissue. 2. In the experimental group 1, the bonding between implanted bone cement and the existing bone was seen, which more increased in 8 weeks than 2 weeks. Inflammatory infiltration and the dispersion of implanted bone cement particles were seen in both 2 weeks and 8 weeks. 3. In the experimental group 2, implanted bone itself had a dimensional stability and no bonding between implanted bone cement and the existing bone was seen in both 2 weeks and 8 weeks. Implanted bone cement was encapsulated by fibrous connective tissue. In addition, inflammatory infiltration was seen around implanted bone cement. On the basis of these results, when LM-CA bone cement or CA-PMMA composite bone cement was implanted in rat calvarial defect, LM-CA bone cement can be used as a bioactive bone graft material due to ability of bonding to the existing bone and CA-PMMA can be used as a graft material for augmentation of bone-volume due to dimensional stability.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.3
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• pp.69-76
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• 2015

The purpose of this paper is to find an limitation to detect the defect of damaged asphalt pavement structures for infrared thermography. We use heat source of a natural light to detect the defect efficiently. The heat source was applied to the asphalt specimens. Four asphalt specimens were used: one was the asphalt containing depth of 1cm internal timber, two was the asphalt containing depth of 2cm internal void, Three was the asphalt containing depth of 3cm internal timber and four was not the asphalt containing internal timber. It was found that the depth of 3cm internal timber could be detected by this method. In addition, we used the image processing to make the damage zone displayed clear in the image obtained from the thermographic operation.