• Structural Engineering and Mechanics
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• 제43권3호
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• pp.395-410
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• 2012

The visualizing energy flow and control in vibrating stiffened plates with a cutout are studied using finite element method. The vibration intensity, vibration energy and strain energy distribution of stiffened plates with cutout at different excitation frequencies are calculated respectively and visualized for the various cases. The cases of different size and boundaries conditions of cutouts are also investigated. It is found that the cutout or opening completely changes the paths and distributions of the energy flow in stiffened plate. The magnitude of energy flow is significantly larger at the edges near the cutout boundary. The position of maximum strain energy distribution is not corresponding to the position of maximum vibrational energy. Furthermore, the energy-based control using constrained damping layer (CDL) for vibration suppression is also analyzed. According to the energy distribution maps, the CDL patches are applied to the locations that have higher energy distribution at the targeted mode of vibration. The energy-based CDL treatments have produced significant attenuation of the vibration energy and strain energy. The present energy visualization technique and energy-based CDL treatments can be extended to the vibration control of vehicles structures.

• 한국생산제조학회지
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• 제8권2호
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• pp.27-34
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• 1999

The growth-strain method was used for shape optimization, which carries out the optimization by distributing uniformly the distributed parameter such as von Mises stress and shear strain energy density. Shape optimization is carried out by iteration of stress analysis and growth strain analysis. In this study, the effect of growth ratio in the method was investigated and then the range of the adequate value of the growth ratio was determined. Also the growth-strain method was improved by applying the linear PID control theory in order to control volume required by a designer. Finally, an automatic shape optimization system was built up by the improved growth-strain method with a commercial software using finite element method. The effectiveness and practicability of the developed shape optimization system was verified by some examples.

• 대한기계학회논문집A
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• 제21권3호
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• pp.423-429
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• 1997

A simplified method for determining the mode components of the strain energy release rate of free-edge delaminations in laminated composite is proposed. The interlaminar stresses are evaluated as an interface moment and interface shear forces that are obtained from the equilibrium equations at the interface between the adjacent layers. Deformation of an edge-delaminated laminate is calculated by using a generalized quasi-three dimensional classical laminated plate theory developed by the authors. The analysis provides closed-form expression for the three components of the strain energy release rate. Comparison of results with a finite element solution using the virtual crack closure technique shows good agreement. In the present study, laminated composite with stacking sequences of [30/-30/90]$_{s}$ were examined. The simple nature of the method makes it suitable for primary design analysis for the delaminations of laminated composite.e.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.169-174
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• 2001

Low cycle fatigue tests are performed on high strength low alloy steels that be developed for submarine material. The relation between absorbed plastic strain energy and numbers of cycle to failure is examined in order to predict the low cycle fatigue life of structural steels by using plastic strain energy method. The cyclic properties are determined by a least square fit techniques. The life predicted by the plastic strain energy method is found to coincide with experiment data and results obtained from the Coffin-Manson method. Also the cyclic behavior of structural steels is characterized by cyclic softening with increasing number of cycle at room temperature. Especially, low cycle fatigue characteristics and microstructural changes of structural steels are investigated according to changing tempering temperatures. In the case of PFS steels, the $\varepsilon$-Cu is formed in 550C of tempering temperature and enhances the low cycle fatigue properties.

• Smart Structures and Systems
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• 제12권3_4호
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• pp.427-440
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• 2013

A growing need has developed in the United States to obtain more specific knowledge on the structural integrity of infrastructure due to aging service lives, heavier and more frequent loading conditions, and durability issues. This need has spurred extensive research in the area of structural health monitoring over the past few decades. Several structural health monitoring techniques have been developed that are capable of locating damage in structures using modal strain energy of mode shapes. Typically in the past, bending strain energy has been used in these methods since it is a dominant vibrational mode in many structures and is easily measured. Additionally, there may be cases, such as pipes, shafts, or certain bridges, where structures exhibit significant torsional behavior as well. In this research, torsional strain energy is used to locate damage. The damage index method is used on two numerical models; a cantilevered steel pipe and a simply-supported steel plate girder bridge. Torsion damage indices are compared to bending damage indices to assess their effectiveness at locating damage. The torsion strain energy method is capable of accurately locating damage and providing additional valuable information to both of the structures' behaviors.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1227-1234
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• 2006

Up to now, several mathematical theories based on strain energy functions have been developed for rubber materials. These theories, coupled with the finite element method, can be used very effectively by engineers to analyze and design rubber components. However, due to the complexities of the mathematical formulations and the lack of general guidelines available fur the analysis of rubber components, it is a formidable task for an engineer to analyze rubber components. In this paper a method for predicting strain energy functions - Neo-Hookean model and Mooney-Rivlin model - from the hardness using the empirical equation without any experiment is discussed. First based on the elasticity theories of rubber, the relation between stress and strain is defined. Then for the butyl rubbers, the model constants of Neo-Hookean model and Mooney-Rivlin model are calculated from uniaxial tension tests. From the results, the usefulness of the empirical equation to estimate elastic modulus from hardness is confirmed and, fur Mooney-Rivlin model, the predicted and the experimental model constants are compared and discussed.

• Geomechanics and Engineering
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• 제7권4호
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• pp.335-353
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• 2014

The softening hyperelastic model based on the strain energy limitation is of clear concepts and simple forms to describe the failure of materials. In this study, a linear and a nonlinear softening hyperelastic model are proposed to characterize the deformation and the failure in granular materials by introducing a softening function into the shear part of the strain energy. A method to determine material parameters introduced in the models is suggested. Based on the proposed models the numerical examples focus on bearing capacity and strain localization of granular materials. Compared with Volokh softening hyperelasticity and classical Mohr-Coulomb plasticity, our proposed models are able to capture the typical characters of granular materials such as the strain softening and the critical state. In addition, the issue of mesh dependency of the proposed models is investigated.

• 마이크로전자및패키징학회지
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• 제17권4호
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• pp.67-72
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• 2010

In this paper, a design optimization of ball grid array packaging geometry is studied based on the Taguchi method, which allowed robust design by considering the variance of the input parameters during the optimization process. Molding compound and substrate were modeled as viscoelastic, and finite element analyses were performed to calculate the strain energy densities of the eutectic solder balls. Six quality factors of the dimensions of the packaging geometry were chosen as control factors. After performing noise experiments to determine the dominant factors, main experiments were conducted to find the optimum packaging geometry. Then the strain energy densities between the original and optimized geometries were compared. It was found that the effects of the packaging geometry on the solder ball reliability were significant, and more than 40% of the strain energy density was reduced by the geometry optimization.

• Smart Structures and Systems
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• 제25권1호
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• pp.47-56
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• 2020

This paper proposes a model-based approach for structural damage identification and quantification. Using pseudo modal strain energy and mode shape vectors, a damage-sensitive objective function is introduced which is suitable for damage estimation and quantification in shear frames. Whale optimization algorithm (WOA) is used to solve the problem and report the optimal solution as damage detection results. To illustrate the capability of the proposed method, a numerical example of a shear frame under different damage patterns is studied in both ideal and noisy cases. Furthermore, the performance of the WOA is compared with particle swarm optimization algorithm, as one the widely-used optimization techniques. The applicability of the method is also experimentally investigated by studying a six-story shear frame tested on a shake table. Based on the obtained results, the proposed method is able to assess the health of the shear building structures with high level of accuracy.

• 한국방재학회 논문집
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• 제10권3호
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• pp.39-43
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• 2010

본 연구의 주목적은 아스팔트 혼합물의 피로균열에 대한 예측모델을 개발하는 것이다. 아스팔트 혼합물의 피로균열 시험을 위하여 응력제어 간접인장피로 시험이 수행되었다. 피로균열에 대한 예측모델 개발을 위하여 내적손상비 증가 개념이 도입되었다. 내적손상비증가 개념에서는 방출에너지 개념을 주로 사용하였으며 기준인장변형율 및 변형율 추이 요소 등이 추가로 사용되었다. 피로시험에서 나타난 방출에너지의 원인은 아스팔트 콘크리트 시료 내부의 손상증가와 재료 자체가 갖고 있는 고유의 점탄성 특성에 기인하는 것으로 판단된다. 방출에너지는 하중재하 횟수가 증가함에 따라 점차 증가함을 보였다.