• 대한의용생체공학회:의공학회지
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• 제31권3호
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• pp.199-209
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• 2010

The locking compression plates-distal femur(LCP-DF) are being widely used for surgical management of the extra-articular complex fractures of the distal femur. They feature locking mechanism between the screws and the screw holes of the plate to provide stronger fixation force with less number of screws than conventional compression bone plate. However, their biomechanical efficacies are not fully understood, especially regarding the number of the screws inserted and their optimal configurations. In this study, we investigated effects of various screw configurations in the shaft and the condylar regions of the femur in relation to structural stability of LCP-DF system. For this purpose, a baseline 3-D finite element (FE) model of the femur was constructed from CT-scan images of a normal healthy male and was validated. The extra-articular complex fracture of the distal femur was made with a 4-cm defect. Surgical reduction with LCP-DF and bone screws were added laterally. To simulate various cases of post-op screw configurations, screws were inserted in the shaft (3~5 screws) and the condylar (4~6 screws) regions. Particular attention was paid at the shaft region where screws were inserted either in clustered or evenly-spaced fashion. Tied-contact conditions were assigned at the bone screws-plate whereas general contact condition was assumed at the interfaces between LCP-DF and bone screws. Axial compressive load of 1,610N(2.3 BW) was applied on the femoral head to reflect joint reaction force. An average of 5% increase in stiffness was found with increase in screw numbers (from 4 to 6) in the condylar region, as compared to negligible increase (less than 1%) at the shaft regardless of the number of screws inserted or its distribution, whether clustered or evenly-spaced. At the condylar region, screw insertion at the holes near the fracture interface and posterior locations contributed greater increase in stiffness (9~13%) than any other locations. Our results suggested that the screw insertion at the condylar region can be more effective than at the shaft during surgical treatment of fracture of the distal femur with LCP-DF. In addition, screw insertion at the holes close to the fracture interface should be accompanied to ensure better fracture healing.

• Steel and Composite Structures
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• 제10권1호
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• pp.69-85
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• 2010

The present paper presents a study on the behavior and design of corrugated web steel beams with and without web openings. In the literature, the web opening problem in steel beams was dealt with mostly for steel beams with plane web plates and research on the effect of an opening on a corrugated web was found out to be very limited. The present study deals mainly with the effect of web openings on the transverse load carrying capacity of steel beams with sinusoidally corrugated webs. A general purpose finite element program (ABAQUS) was used. Simply supported corrugated web beams of 2 m length and with circular web openings at quarter span points were considered. These points are generally considered to be the optimum locations of web openings for steel beams. Various cases were analyzed including the size of the openings and the corrugation density which is a function of the magnitude and length of the sine wave. Models without web holes were also analyzed and compared with other cases which were all together examined in terms of load-deformation characteristics and ultimate web shear resistance.

• 대한기계학회논문집A
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• 제33권4호
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• pp.360-365
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• 2009

In the manufacture of CFRP(Carbon Fiber Reinforced Polymer Composite) composite structures, various independent components join by bolts and pins. Holes for bolts and pins have an effect on the failure strength of such structures, because those act as notches in structures. The failure characteristic of such structures are different from those of plain plate subject to remote load. In this paper, tensile properties of woven CFRP composite plates with laminates of $0^{\circ}$, $30^{\circ}$ and $45^{\circ}$ were obtained according to ASTM D 3039. By using obtained tensile failure strength and Tan-Cheng failure criterion, tensile failure strength of CFRP laminate with arbitrary fiber angle were evaluated. Also, the degradation of tensile properties by center hole(${\phi}10mm$) with a remote load was evaluated and the failure strengths were applied to Tan's failure criterion, similarly.

• Structural Engineering and Mechanics
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• 제89권1호
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• pp.93-102
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• 2024

Using negative Poisson's ratio materials, an innovative metallic-yielding damper is introduced for the first time in this study. Through the use of ABAQUS commercial software, a nonlinear finite element analysis is conducted to determine the performance of the proposed system. Mild steel plates with elliptical holes are used for these types of dampers, which dissipate energy through an inelastic deformation of the constitutive material. To assess the capability of the proposed damper, nonlinear quasi-static finite element analyses have been conducted on the damper with a variety of geometric parameters. According to the results, the proposed system is ductile and has a high capacity to dissipate energy. The proposed auxetic damper has a specific energy absorption of 910.8 J/kg and a ductility of 33.6. Therefore, this damper can dissipate a large amount of earthquake input energy without buckling by increasing the buckling load of the brace with its ductile behavior. In addition, it was found that by incorporating auxetic dampers in the steel frame, the frame was made harder, stronger, and ductile and its energy absorption increased by 300%.

• 대한족부족관절학회지
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• 제17권2호
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• pp.143-149
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• 2013

Purpose: Open reduction and internal fixation of calcaneal fracture using plate has been used. While numerous plates have been manufactured, most of the conventional plates are designed for westerners, realistically the size is larger for Korean. The domestic products, on the other hand, often have the undesirable screw holes and path. Therefore, we measured the radiologic parameter of Korean calcaneus for providing the plate and screw hole placements. Materials and Methods: We measured the outer lines and angles with over the 20 years old 291 females and 322 males. A: Length of inferior plane of calcaneus, B: Length of anterior plane of calcaneus, C: Length from line A to sinus tarsi, D: Length from line A to posterior point of posterior facet, E: Length from line A to calcaneal tuberosity, F: Length of posterior facet, G: Length from anterior point of line A to C, H: Length from line C to line D, a: Angle between A and B, b: Gissane angle, c: Bohler angle, d: Calcaneal pitch angle using Marosis m-view$^{(R)}$. Results: Mean A, B, C, D, E, F, G, H were 63.6, 26.4, 23.2, 43.7, 40.5, 26.9, 12.8, 18.1 mm. Mean a, b, c, d angle were 105.8, 122.4, 32.4, $20.5^{\circ}$. Male's calcaneus is significantly bigger than female's (p<0.001). Conclusion: AP calcaneus length 63.6 mm, maximal height 43.7 mm is considered to be helpful in making the Korean calcaneal plate.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권1호
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• pp.64-69
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• 2000

This paper investigates the equeeze film damping of a perforated planar micromechanical structure that oscillates in the normal direction to the substrate. Special focus has been places on the effect of holes and edges of the perforated planar microstructures on the squeeze film damping of oscillatory motions. Theoretical models and test structures of the squeeze film damping have been developed for the transversely oscillating perforated plates. A set of nine different test structures, having three different sized with three different numbers of perforations, has been fabricated and tested. The experimental Q-factors, measured from the fabricated test structures, are compared with the theoretical values, estimated from finite element analysis. It is found that the finite element analysis overestimates the Q-factors up to 150% of the experimental values. Major discrepancy comes from the inaccuracy of the zero pressure condition, placed by the finite element analysis along the perforated edges.

• 한국정밀공학회지
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• 제27권2호
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• pp.109-116
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• 2010

It is important to make a mechanical structure precisely and reasonably in predicting the dynamic characteristics, controlling the vibration, and designing the structure dynamics. In finite element analysis model updating is appropriate as the design parameter is used to analyze the dynamic system. The errors can be contained from the physical parameters and the element modeling. From the dynamic test, more precise dynamic characteristics can be obtained. In this paper, model updating algorithm is developed using frequency difference between experiment and calculation. Modal frequencies are obtained by experiment and finite element analysis for beams with various cross section and shapes which have added masses and holes in the middle. For plates with and without groove, experiment and analyses are carried out by applying free boundary conditions as well. Mass and stiffness matrices are updated by comparing test and analytical modal frequencies. The result shows that the updated frequencies become closer to the test frequencies in case that both matrices are updated. An improved analytical model is obtained by changing model parameters such that the discrepancy between test and finite element frequencies is minimized. For beam and plate models updating of mass and stiffness matrices can improve the dynamical behavior of the model by acting on the physical parameters such as masses and stiffness.

• Structural Engineering and Mechanics
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• 제31권4호
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• pp.439-451
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• 2009

The paper deals with the problem related to the modelling of riveted assemblies for crashworthiness analysis of full-scale complete aircraft structures. Comparisons between experiments and standard FE computations on high-energy accidental situations onto aluminium riveted panels show that macroscopic plastic strains are not sufficiently localised in the FE shells connected to rivet elements. The main reason is related to the structural embrittlement caused by holes, which are currently not modelled. Consequently, standard displacement FE models do not succeed in initialising and propagating the rupture in sheet metal plates and along rivet rows as observed in the experiments. However, the literature survey show that it is possible to formulate super-elements featuring defects that both give accurate singular strain fields and are compatible with standard displacement finite elements. These super-elements can be related to the displacement model of the hybrid-Trefftz principle of the finite element method, which is a kind of domain decomposition method. A feature of hybrid-Trefftz finite elements is that they are mainly used for elastic computations. It is thus proposed to investigate the possibility of formulating a hybrid displacement finite element, including the effects of a hole, dedicated to crashworthiness analysis of full-scale aeronautic structures.

• 한국의학물리학회지:의학물리
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• 제29권2호
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• pp.59-65
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• 2018

This paper describes the clinical use of the dose verification of multileaf collimator (MLC)-based CyberKnife plans by combining the Octavius 1000SRS detector and water-equivalent RW3 slab phantom. The slab phantom consists of 14 plates, each with a thickness of 10 mm. One plate was modified to support tracking by inserting 14 custom-made fiducials on surface holes positioned at the outer region of $10{\times}10cm^2$. The fiducial-inserted plate was placed on the 1000SRS detector and three plates were additionally stacked up to build the reference depth. Below the detector, 10 plates were placed to avoid longer delivery times caused by proximity detection program alerts. The cross-calibration factor prior to phantom delivery was obtained by performing with 200 monitor units (MU) on the field size of $95{\times}92.5mm^2$. After irradiation, the measured dose distribution of the coronal plane was compared with the dose distribution calculated by the MultiPlan treatment planning system. The results were assessed by comparing the absolute dose at the center point of 1000SRS and the 3-D Gamma (${\gamma}$) index using 220 patient-specific quality assurance (QA). The discrepancy between measured and calculated doses at the center point of 1000SRS detector ranged from -3.9% to 8.2%. In the dosimetric comparison using 3-D ${\gamma}$-function (3%/3 mm criteria), the mean passing rates with ${\gamma}$-parameter ${\leq}1$ were $97.4%{\pm}2.4%$. The combination of the 1000SRS detector and RW3 slab phantom can be utilized for dosimetry validation of patient-specific QA in the CyberKnife MLC system, which made it possible to measure absolute dose distributions regardless of tracking mode.

• Composites Research
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• 제26권1호
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• pp.42-47
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• 2013

본 연구에서는 공기역학적 또는 열 전달에 유리한 형상인 딤플을 복합재료 제품의 표면에 다수 형성하는 경제적이고도 효과적인 성형방법을 개발하였다. 금형을 이용하여 제품의 표면에 다수의 딤플을 형성시키려면 몰드의 표면에 볼록한 반구형상을 가공하여야 하는데 이렇게 하려면 높은 금형 제작비가 소요된다. 본 연구에서는 다수의 원형 구멍이 뚫린 판재를 이용하여, 이의 표면에 복합재료 스킨을 입히면서 외부에서 압력을 가하여 딤플 형상이 표면에 자연스럽게 형성되도록 하는 방법을 개발하였다. 표면에 다수의 딤플을 갖는 복합재료는 공기저항을 줄이거나 방열효과가 필요한 고속 경기용 자동차의 외장 등으로 널리 응용 될 수 있을 것으로 사료된다.