• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.648-661
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• 2019

Thin fabric-based yacht sails have a cambered shape to generate lift force; however, their shape can be easily deformed by wind pressure and also affected by the deformation of the mast. These deformations can change the airflow characteristics over the sail. Therefore, Fluid-Structure Interaction (FSI) analysis is needed to evaluate the sail force precisely. In this study, airflow over the deformed sail and rig was studied using FSI. Elastic deformation of the sail and rig was obtained by an aerodynamic calculation under dynamic pressure loading on the sail surface. The effects of rig deformation on the aerodynamic performance of the sail were examined according to the rig type and mast flexibilities. As a result, the changes of lift force for a fractional type rig with a thin mast section were more significant than with a masthead rig.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.5
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• pp.69-77
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• 2004

FRP rebar has low bond performance than steel rebar. Usually, FRP rebar has about 60% of bond strength of steel rebar. Without adequate bond to concrete, the full composite action between reinforcement and concrete matrix can not be achieved. Therefore, FRP rebars must also have surface deformations that provide good bond to concrete. The purpose of this research was decided an optimum surface deformation patterns through bond test of FRP rebar. Eighteen surface deformation patterns of FRP rebar with widely different geometries were investigated. Based on the test results, we established optimum surfale deformation pattern. Bond tests were performed for three types of surface deformation patterns of FRP rebar including sand coated rebar, ribbed rebar, and wrapped and sand coated rebar that commercially available, and two types of FRP rebar including CFRP, GFRP rebars that optimum surface deformation pattern is applied. According to bond test results, FRP rebars that optimum surface deformation pattern is applied were found to have better bond strength with concrete than currently using FRP rebar.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.171-180
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• 2001

Collision accident reconstruction algorithm are developed based on the deformation shape and severity of a car body. At first, the body stiffness equation representing the force-deformation relationship is derived using finite element analysis for head on collision of two cars. The database of deformation shapes and energies is constructed for five different collision configurations; each configuration contains three velocity conditions. Deformation shapes are obtained using a curve fitting method and result in cubic polynomials. Deformation energies are calculated using a stiffness equation and deformation data. Three algorithms are developed to reconstruct collision configuration compared with constructed database. The developed algorithms show reasonably good performance to find collisions conditions for some test problems.

• International Journal of Highway Engineering
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• v.14 no.4
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• pp.29-36
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• 2012

PURPOSES : Plastic deformation is frequently made in intersection asphalt pavement at its early age due to deceleration and stoppage of vehicles. This study has been performed to provide a mechanistic basis for reasonable selection of paving method to minimize the plastic deformation at intersection. METHODS : Pavement layer, temperature, traffic volume of the intersections managed by the Daejeon Regional Construction and Management Administration were collected to calculate asphalt dynamic modulus with pavement depth by using a prediction equation suggested by the Korean pavement design guide. Performance of ordinary dense-graded asphalt pavement, polymer modified asphalt pavement, and fiber reinforced asphalt pavement was analyzed by finite element method and the results were used in a performance model to predict the plastic deformation. RESULTS : In aspect of performance, the three paving methods were usable under low traffic while the fiber reinforced asphalt pavement was the most suitable under heavy traffic. CONCLUSIONS : Reasonable paving method suitable for traffic characteristics in the intersection might be decided by considering economic feasibility.

• Steel and Composite Structures
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• v.16 no.4
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• pp.357-374
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• 2014

The design basis is being shifted from strength to deformation in modern performance-based design codes. This paper presents a practical method for optimization of eccentrically braced steel frames, based on the concept of uniform deformation theory (UDT). This is done by gradually shifting inefficient material from strong parts of the structure to the weak areas until a state of uniform deformation is achieved. In the first part of this paper, UDT is implemented on 3, 5 and 10 story eccentrically braced frames (EBF) subjected to 12 earthquake records representing the design spectrum of ASCE/SEI 7-10. Subsequently, the optimum strength-distribution patterns corresponding to these excitations are determined, and compared with four other loading patterns. Since the optimized frames have uniform distribution of deformation, they undergo less damage in comparison with code-based designed structures while having minimum structural weight. For further investigation, the 10 story EBF is redesigned using four different loading patterns and subjected to 12 earthquake excitations. Then a comparison is made between link rotations of each model and those belonging to the optimized one which revealed that the optimized EBF behaves generally better than those designed by other loading patterns. Finally, efficiency of each loading pattern is evaluated and the best one is determined.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.8
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• pp.597-609
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• 2020

These days, the coaxial rotor system is used for various purposes like UAVs, Mars exploration helicopters, and the next-generation high-speed rotorcraft. A number of research projects on aerodynamic performance of rotor systems, including the coaxial configuration have been made previously. On the contrary, research on rotor blade deformation has been mainly carried out regarding the single rotor system, where such effort has not been enough on the coaxial system. Nonetheless, in case of the coaxial system, blade deformation analysis is much more important because of the complex air flow around the rotors, and that the distance between the two rotors is a key factor affects aerodynamic performance of the entire system. For these reasons, an experimental study on rotor blade deformation of the coaxial system was conducted using the Stereo Pattern Recognition(SPR) technique, one of the state-of-the-art of photogrammetry method. In this research, a small-scale coaxial rotor test stand designed by Korea Aerospace Research Institute(KARI) was used. With the same test stand, performance of the coaxial configuration had been studied before the experimental study on blade deformation, in order to find the relation between performance and blade deformation of the rotor system. Results of the performance test and the deformation study are presented in this article.

• Nuclear Engineering and Technology
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• v.53 no.11
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• pp.3723-3740
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• 2021

The harsh conditions in the reactor affect the thermal and mechanical performance of the fuel plate heavily. Some in-pile behaviors, like fission-induced swelling, can cause a large deformation of fuel plate at very high burnup, which may even disturb the flow of coolant. In this research, the emphasis is put on the thermal expansion, fission-induced swelling, interaction layer (IL) growth, creep of the fuel meat, and plasticity of the cladding for the U₃Si₂/Al dispersion fuel plate. A detailed model of the fuel meat swelling is developed. Taking these in-pile behaviors into consideration, the three-dimensional large deformation incremental constitutive relations and stress update algorithms have been developed to study its thermal-mechanical performance under normal conditions using Abaqus. Results have shown that IL can effectively decrease the thermal conductivity of fuel meat. The high Mises stress region mainly locates at the interface between fuel meat and cladding, especially around the side edge of the interface. With irradiation time increasing, the stress in the fuel plate gets larger resulting from the growth of fuel meat swelling but then decreases under the effect of creep deformation. For the cladding, plasticity deformation does not occur within the irradiation time.

• Structural Engineering and Mechanics
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• v.90 no.5
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• pp.447-458
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• 2024

This study investigated the influence of scale ratio and vertical load on the seismic performance of Puzuo joints in traditional Chinese timber structures. Three low-cyclic reversed loading tests were conducted on three scaled specimens of Bujian Puzuo in Yingxian Wooden Pagoda. This study focused on the deformation patterns and analyzed seismic performance under varying scale ratios and vertical loads. The results indicated that the slip and rotational deformations of Bujian Puzuo were the primary deformations. The scale of the specimen did not affect the layer where the maximum interlayer slip occurred, but it did decrease the proportion of slip deformation. Conversely, the reducing vertical load caused the layer with the maximum slippage and the position of the damaged Dou components to shift upward, and the proportion of slip deformation increased. When the vertical load was decreased by 3.7 times, the maximum horizontal bearing capacity under positive and negative loadings, initial stiffness, and energy dissipation of the specimen decreased by approximately 60%, 58.79%, 69.62%, and 57.93%, respectively. The horizontal bearing capacity under positive loading and energy dissipation of the specimen increased by 35.63% and 131.54%, when the specimen scale was doubled and the vertical load was increased by 15 times.

• Structural Engineering and Mechanics
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• v.52 no.1
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• pp.75-87
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• 2014

To analyze the tension performance of laminated rubber bearings under tensile loading, a theoretical tension model for analyzing the rubber bearings is proposed based on the theory of elasticity. Applying the boundary restraint condition and the assumption of incompressibility of the rubber (Poisson's ratio of the rubber material is about 0.5 according the existing research results), the stress and deformation expressions for the tensile rubber layer are derived. Based on the derived expressions, the stress distribution and deformation pattern especially for the deformation shapers of the free edges of the rubber layer are analyzed and validated with the numerical results, and the theory of cracking energy is applied to analyze the distributions of prediction cracking energy density and gradient direction. The prediction of crack initiation and crack propagation direction of the rubber layers is investigated. The analysis results show that the stress and deformation expressions can be used to simulate the stress distribution and deformation pattern of the rubber layer for laminated rubber bearings in the elastic range, and the crack energy method of predicting failure mechanism are feasible according to the experimental phenomenon.

• Journal of Magnetics
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• v.16 no.3
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• pp.294-299
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• 2011

Nd-Fe-B high performance magnets were prepared by die-upset forging. The effects of the deformation parameters on magnetic properties and flow stress were studied. Deformation temperatures in the range of $600{\sim}900^{\circ}C$ enable to achieve an effective anisotropy and temperature $800^{\circ}C$ proves to be suitable for deformation of Nd-Fe-B magnets. The amount of c-axis alignment along the press direction seems to depend on the amount of deformation and a saturation behavior is shown at deformation ratio of 75%. Magnetic properties are also related to strain rate, and maximum energy product is attained at an optimum strain rate of ${\varphi}=1{\times}10^{-2}s^{-1}$. By analyzing the relationship of stress and strain at different deformation temperature during die-upset forging process, deformation behavior of Nd-Fe-B magnets was studied and parameters for describing plastic deformation were obtained. Nd-rich boundary liquid phase, which is additionally decreasing the flow stress during deformation, is supposed to play the role of diffusion path and enhance the diffusion rate.