• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.1041-1050
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• 2001

Control of bone cement volume (PMMA) may be critical for preventing complications in vertebroplasty, the percutaneous injection of PMMA into vertebra. The purpose of this study was to predict the optimal volume of PMMA injection based on CT images. For this, correlation between PMMA volume and textural features of CT images was examined before and after surgery to evaluate the appropriate PMMA amount. The gray level run length analysis was used to determine the textural features of the trabecular bone. Extimation of PMMA volume was done using 3D visualization with semi-automatic segmentation on postoperative CT images. Then, finite element (FE) models were constructed based on the CT image data of patients and PMMA volume. Appropriate material properties for the trabecular bone were assigned by converting BMD to elastic modulus. Structural reinforcement due to the changes in PMMA volume and BMD was assessed in terms of axial displacement of the superior endplate. A strong correlation was found between the injected PMMA volume and the area of the intertrabecular space and that of trabecular bone calculated from the CT images (r=0.90 and -0.90, respectively). FE results suggested that vertebroplasty could effectively reinforce the osteoporotic vertebra regardless of BMD or PMMA volume. Effectiveness of additional PMMA injection tended to decrease. For patients with BMD well lower than 50mg/ml, injection of up to 30% volume of the vertebral body is recommended. However, less than 30% is recommended otherwise to avoid any complications from excessive PMMA because the strength has already reached the normal level.

• 대한기계학회논문집A
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• 제31권7호
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• pp.792-799
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• 2007

A newly developed cellular metal based on kagome lattice is an ideal candidate for multifunctional materials achieving various optimal properties. Intensive efforts have been devoted to develop efficient techniques for mass production due to its wide potential applications. Since a variety of imperfections would be inevitably included in the realistic fabrication processes, it is highly important to examine the correlation between the imperfections and material strengths. Previous performance tests were mostly done by numerical simulations such as finite element method (FEM), but only for perfect structures without any imperfection. In this paper, we developed an efficient numerical framework using nonlinear random network analysis (RNA) to verify how the statistical imperfections (geometrical and material property) contribute to the performance of general truss structures. The numerical results for kagome truss structures are compared with experimental measurements on 3-layerd WBK (wire-woven bulk kagome). The mechanical strength of the kagome structures is shown relatively stable with the Gaussian types of imperfections.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.870-874
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• 2007

Golf ball spin rate after impact with club is created by the contact force, which is greatly influenced by ball and club mass, material, impact speed, and club loft angle. Previous studies showed that the contact force is determined as the resultant force of the reaction forces normal and tangential to the club face at the contact point. The normal force causes the compression and restitution of the ball, and the tangential force creates the spin. Especially, the tangential force takes either positive or negative values as the ball rolls and slides along the club face during impact. Although the positive and negative tangential forces are known to create and reduce the back spin rate, respectively, the mechanism of ball spin creation has not yet been discussed in detail. It is shown in this work that the linear impulse of the tangential force is directly related to generation of back spin rate of golf ball. The linear impulse can be calculated from the tangential force, which depends upon many factors such as ball and club mass, material, impact speed, and club loft angle. In this research, the influence of the contact force between golf club and ball is investigated to analyze the mechanism of impact. For this purpose, the contact force and the contact time at impact between golf club head and ball are computed using FEM.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.82-88
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• 2006

The objective of this paper is to get excitation forces of the engine. A powertrain geometry model is produced by CATIA and its FE model is made by MSC/Patran. A vibration mode analysis which makes us know the natural frequency and mode shape and a running mode analysis which measures the mode shape as a relative displacement about one reference point by measuring the acceleration of each bracket to take a place at the running vehicle are experimentally implemented. After getting a satisfied MAC value by doing a correlation about a measured mode analysis value and analyzed value through MSC/Nastran software, all components are assembled through MSC/ADAMS software which is a dynamic analysis tool. We can predict the vibration of brackets which is the last points to occur the force of the engine combustion by analyzing the combustion force produced by engine mechanism.

• 한국소음진동공학회논문집
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• 제18권9호
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• pp.972-981
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• 2008

The blower which is installed in a FCEV(fuel cell electric vehicle) may cause noise due to misalignment and unbalance of mechanical components that rotate at high speed. One of the key points in efforts to minimize the noise radiation from a blower is the knowledge of the main radiating component and the relation between the surface vibration of a blower and the sound pressure. In this research, the blower model is developed based on FEM(finite element method). FE(finite element) model is reliable by correlation of frequencies and MAC(modal assurance criterion) values between EMA(experimental modal analysis) and FEA(finite element analysis). This model is applied to predict the vibration of a blower by using inverse force identification method and predict the radiating noise by using BEM(boundary element method). Comparing the frequencies of resonance and those mode shapes between EMA and FEA, a structural modification of the FE model is evaluated for reducing the parameters of the blower noise.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.78-83
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• 2007

A newly developed cellular metal based on kagome lattice is an ideal candidate for multifunctional materials achieving various optimal properties. Intensive efforts have been devoted to develop efficient techniques for mass production due to its wide potential applications. Since a variety of imperfections would be inevitably included in the realistic fabrication processes, it is highly important to examine the correlation between the imperfections and material strengths. Previous performance tests were mostly done by numerical simulations such as finite element method (FEM), but only for perfect structures without any imperfection. In this paper, we developed an efficient numerical framework using nonlinear random network analysis (RNA) to verify how the statistical imperfections (geometrical and material property) contribute to the performance of general truss structures. The numerical results for kagome truss structures are compared with experimental measurements on 3-layerd WBK (wire-woven bulk kagome). The mechanical strength of the kagome structures is shown relatively stable with the Gaussian types of imperfections.

• 한국해안·해양공학회논문집
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• 제27권4호
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• pp.197-201
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• 2015

본 연구에서는 셀 구조물의 체적과 항복하중과의 상관관계를 규명하기 위하여 실내실험 및 수치해석을 수행하였다. 실험과 해석 결과 산출된 항복하중 값은 양호한 상관관계를 보였으며, 항복하중 값의 산출에 있어서 본 연구에서 수행한 유한요소 해석 기법은 타당한 것으로 검증되었다. 유한요소해석 결과, 셀 구조물의 체적 증가에 따라 항복하중은 증가되었으며 항복하중은 체적 증가비율만큼 증가하는 것으로 나타났다.

• 한국소음진동공학회논문집
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• 제17권11호
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• pp.1127-1132
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• 2007

Golf ball spin rate after impact with club is created by the contact force, which is greatly influenced by ball and club mass, material, impact speed, and club loft angle. Previous studies showed that the contact force is determined as the resultant force of the reaction forces normal and tangential to the club face at the contact point. The normal force causes the compression and restitution of the ball, and the tangential force creates the spin. Especially, the tangential force takes either positive or negative values as the ball rolls and slides along the club face during impact. Although the positive and negative tangential forces are known to create and reduce the back spin rate, respectively, the mechanism of ball spin creation has not yet been discussed in detail. It is shown in this work that the linear impulse of the tangential force is directly related to generation of back spin rate of golf ball. The linear impulse can be calculated from the tangential force, which depends upon many factors such as ball and club mass, material, impact speed, and club loft angle. In this research, the influence of the contact force between golf club and ball is investigated to analyze the mechanism of impact. For this purpose, the contact force and the contact time at impact between golf club head and ball are computed using FEM.

• Earthquakes and Structures
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• 제18권5호
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• pp.555-565
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• 2020

The main objective of seismic codes is to prevent structural collapse and ensure life safety. Collapse probability of a structure is usually assessed by making a series of analytical model assumptions. This paper investigates the effect of finite element modeling (FEM) assumptions on the estimated collapse capacity of a reinforced concrete (RC) frame building and points out the modeling limitations. Widely used element formulations and hysteresis models are considered in the analysis. A full-scale, three-story RC frame building was utilized as the experimental model. Alternative finite element models are established by adopting a range of different modeling strategies. Using each model, the collapse capacity of the structure is evaluated via Incremental Dynamic Analysis (IDA). Results indicate that the analytically estimated collapse capacities are significantly sensitive to the utilized modeling approaches. Furthermore, results also show that models that represent stiffness degradation lead to a better correlation between the actual and analytical responses. Results of this study are expected to be useful for in developing proper models for assessing the collapse probability of RC frame structures.

• Geomechanics and Engineering
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• 제14권1호
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• pp.91-98
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• 2018

Length of a vehicle is an important variation to generate different variants of an automotive platform. This parameter is usually adjusted by embedding dimensional flexibility into different components of the Body in White (BIW) including the floor pan. Due to future uncertainties, it is not necessarily possible to define certain values of wheelbase for the future products of a platform. This work is performed to add flexibility into the design process of a length-variable floor pan. By means of this analysis, the cost and time consuming process of optimization is not necessary to be performed for designing the different variants of a product family. Stiffness and mass of the floor pan are two important functional requirements of this component which directly affect the occupant comfort, dynamic characteristics, fuel economy and environmental protection of the vehicle. A combination of Genetic algorithm, GMDH-type of artificial neural networks and TOPSIS methods is used to optimally design the floor pan associated with arbitrary length of the variant in the defined system range. The correlation between the optimal results shows that for a constant mass of the floor pan, the first natural frequency decreases by increasing the length of this component.