• Composites Research
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• v.27 no.2
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• pp.59-65
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• 2014

Most of energy are obtained from oil, coal, and natural gas, most likely, fossil fuel which is limited throughout the world. Recently, high crude oil price, climate change, oil depletion, etc. are main reason to get attention to non-fossil energy including renewable energy in the world. In this study, we studied analysis and design of structure system composed of pultruded fiber reinforced polymer composite (PFRP) which has many advantages such as high specific strength and stiffness, high corrosion resistance and chemical resistance. For the design and construction of floating-type structure, PFRP structural members may be the first choice. Design of tracking-type floating PV generation structure was performed by using the results of the finite element analysis. The structure is fabricated and installed on the water surface. Before the installation of the structure, safety related problems associated with installation and operation are investigated using the finite element simulation and it was found that the structure is safe enough to resist externally applied loads.

• Journal of the Korean Society of Safety
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• v.20 no.2 s.70
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• pp.26-31
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• 2005

The strong continuous fiber reinforced metal matrix composites (MMCs) are recently used in aerospace and transportation applications as an advanced material due to its high strength and light weight. Unidirectional fiber-metal matrix composites have superior mechanical properties along the longitudinal direction. However, the applicability of continuous fiber reinforced MMCs is somewhat limited due to their relatively poor transverse properties. Therefore, the transverse properties of MMCs are significantly influenced by the properties of the fiber/matrix interface. In order to be able to utilize these MMCs effectively and with safety, it must be determined their elastic plastic behaviors at the interface. In this study, the interfacial stress states of transversely loaded unidirectional fiber reinforced metal matrix composites investigated by using elastic-plastic finite element analysis. Different fiber volume fractions $(5-60\%)$ were studied numerically. The interlace was treated as three thin layer (with different properties) with a finite thickness between the fiber and the matrix. The fiber is modeled as transversely isotropic linear-elastic, and the matrix as isotropic elastic-plastic material. Using proposed model, the effects of the interface region and fiber arrangement in MMCs on the distributions of stress and strain are evaluated. The stress distributions of a thin multi layer interface have much less changes compared with conventional perfect interface. The analyses were based on a two-dimensional generalized plane strain model of a cross-section of an unidirectional composite by the ANSYS finite element analysis code.

• The Journal of the Acoustical Society of Korea
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• v.16 no.3
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• pp.13-17
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• 1997

This paper investigates the influence of material properties of the acoustic damping layer in the low noise hydrophone designed in the previous paper. For increase of the insensitivity of the hydrophone to external noises, acoustic impedance and damping coefficients are selected and the effects of the selected material property on the hydrophone response to the external noises are simulated with finite element method (FEM). The results show that the damping coefficients are not influential to the structural vibration decoupling from the sensing element. On the other hand, the optimum acoustic impedance of compliant layer is estimated which is smaller than 1 Mrayl or larger than 4 Mrayl. However polymer materials, which are in general use for acoustic window and damping layers, is not appropriate for the compliant materials of this hydrophone. Therefore development of new composite materials, i.e. ceramic-polymer composite or metal-ceramic composites etc., is required for the development of effective self noise suppressing underwater hydrophones.

• The Journal of Advanced Prosthodontics
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• v.10 no.3
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• pp.184-190
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• 2018

PURPOSE. To analyze stress distribution in premolars restored with inlays or onlays using various materials. MATERIALS AND METHODS. Three-dimensional maxillary premolar models of abutments were designed to include the following: 1) inlay with O cavity (O group), 2) inlay with MO cavity (MO group), 3) inlay with MOD cavity (MOD group), and 4) onlay (ONLAY group). A restoration of each inlay or onlay cavity was simulated using gold alloy, e.max ceramic, or composite resin for restoration. To simulate masticatory forces, a total of 140 N static axial force was applied onto the tooth at the occlusal contact areas. A finite element analysis was performed to predict the magnitude and pattern of stresses generated by occlusal loading. RESULTS. Maximum von Mises stress values generated in the abutment teeth of the ONLAY group were ranged from 26.1 to 26.8 MPa, which were significantly lower than those of inlay groups (O group: 260.3-260.7 MPa; MO group: 252.1-262.4 MPa; MOD group: 281.4-298.8 MPa). Maximum von Mises stresses generated with ceramic, gold, and composite restorations were 280.1, 269.9, and 286.6 MPa, respectively, in the MOD group. They were 252.2, 248.0, 255.1 MPa, respectively, in the ONLAY group. CONCLUSION. The onlay design (ONLAY group) protected tooth structures more effectively than inlay designs (O, MO, and MOD groups). However, stress magnitudes in restorations with various dental materials exhibited no significant difference among groups (O, MO, MOD, ONLAY).

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.90-100
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• 1993

A finite element formulation of vibration control of a laminated plate with piezoelectric sensor/ actuators is presented. Classical lamination theory with the induced strain actuation and Hamilton's principle are used to formulate the equations of motion of the system. The total charge developed on the sensor layer is calculated from the direct piezoelectric equation. The equations of motion and the total charge are discretized with 4 node, 12 degrees of freedom quadrilateral plate bending elements with one electrical degree of freedom. The mass and stiffness of the piezoelectric layer are introduced by treating them as another layer in laminated plate. Piezoelectric sensor/actuators are distributed, but discrete due to the geometry of electrodes. By defining an i.d. number of electrode for each element, modelling of electrodes with variable geometry can be achieved. The static response of a piezoelectric bimorph beam to electrical loading and sensor voltage to given displacement are calculated. For a laminated plate under the negative velocity feedback control, the direct time response by the Newmark-.betha. method and damped frequencies and modal damping ratios by modal state space analysis are derived.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.3
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• pp.18-24
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• 2011

In this paper, we present the load-deflection behavior of GRP pipes. GRP buried pipes are widely used in construction in the advantage of their superior mechanical and physical characteristics such as high chemical resistance, high corrosion resistance, right weight, smooth surface of the pipe, and cost effectiveness from soil-structure interaction. To design flexible pipes to be buried underground, it should be based on the ASTM D2412(2010). When applying ASTM D 2412(2010) to the design, pipe stiffness(PS) must be predetermined by the parallel-plate test which requires tedious and laborious working process. To overcome such problems, the finite element simulations for finding the load-deflection behavior of the GRP flexible pipes is installed at UTM testing machine. In the finite element simulations, basic data, such as the modulus of elasticity of the material and cross-sectional dimension, is used. From the investigation, we found that the difference between experimental result and analytical prediction is less than 15% when the pipe deflected 3% and 5% of its vertical diameter although the pipe material is not uniform across the cross-section.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.1
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• pp.25-33
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• 2003

The failure load and mode of the unidirectional and fabric hybrid composite laminate joints are studied by test and finite element analysis. Test is conducted for the specimens with nine various geometries under pin loading. Finite element analysis is performed considering the contact and friction effects between the pin and laminate by MSC/NASTRAN. Failure is estimated by Tsai-Wu and Yamada-Sun criteria on the characteristic curve. While the failure of the specimens with the small width and edge length are much affected by the joint geometry, the geometry effects are negligible in the specimens with large width and edge length. Finite element analysis based on the characteristic length method reasonably predicts the failure load and mode of the joints.

• Tribology and Lubricants
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• v.37 no.4
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• pp.144-150
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• 2021

The most cost-effective method of reducing abrasive wear in mechanical parts is increasing their hardness with thin hard coatings. In practice, the composite hardness of the coated substrate is more important than that of the substrate or coating. After full unloading of the load applied to an indenter, its indentation hardness evaluated based on the dent created on the test piece was almost dependent on plastic deformation of the substrate. Following the first part of this study, which proposes a new Brinell hardness test method for a coated surface, the remainder of the study is focused on practical application of the method. Indentation analyses of a rigid sphere and elastic-perfect plastic materials were performed using finite element analysis software. The maximum principal stress and plastic strain distributions as well as the dent shapes according to the substrate yield stress and coating thickness were compared. The substrate yield stress had a significant effect on the dent size, which in turn determines the Brinell hardness. In particular, plastic deformation of the substrate produced dents regardless of the state of the coating layer. The hardness increase by coating behaved differently depending on the substrate yield stress, coating thickness, and indentation load. These results are expected to be useful when evaluating the composite hardness values of various coated friction surfaces.

• Composites Research
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• v.34 no.1
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• pp.70-75
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• 2021

This paper presents a novel algorithm to reconstruct meso-scale representative volume elements (RVE), referring to experimentally observed features of Sheet Molding Compound (SMC) composites. Predicting anisotropic mechanical properties of SMC composites is challenging in the multiscale virtual test using finite element (FE) models. To this end, an SMC RVE modeler consisting of a series of image processing techniques, the novel reconstruction algorithm, and a FE mesh generator for the SMC composites are developed. First, micro-CT image processing is conducted to estimate probabilistic distributions of two critical features, such as fiber chip orientation and distribution that are highly related to mechanical performance. Second, a reconstruction algorithm for 3D fiber chip packing is developed in consideration of the overlapping effect between fiber chips. Third, the macro-scale behavior of the SMC is predicted by the multiscale analysis.

• Computers and Concrete
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• v.32 no.1
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• pp.15-26
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• 2023

In order to study the anti-seismic performance of full light-weight concrete utility tunnel, EL Centro seismic waves were input, and the seismic simulation shaking table test was carried out on the four utility tunnel models. The dynamic characteristics and acceleration response of the system consisting of the utility tunnel structure and the soil, and the interlayer displacement response of the structure were analyzed. The influence law of different construction methods, haunch heights and concrete types on the dynamic response of the utility tunnel structure was studied. And the experimental results were compared with the finite element calculation results. The results indicated that with the increase of seismic wave intensity, the natural frequency of the utility tunnel structure system decreased and the damping ratio increased. The assembling composite construction method could be equivalent to replace the integral cast-in-place construction method. The haunch height of the assembling composite full light-weight concrete utility tunnel was increased from 30 mm to 50 mm to enhance the anti-seismic performance during large earthquakes. The anti-seismic performance of the full light-weight concrete utility tunnel was better than that of the ordinary concrete utility tunnel. The peak acceleration of the structure was reduced by 21.8% and the interlayer displacement was reduced by 45.8% by using full light-weight concrete. The finite element simulation results were in good agreement with the experimental results, which could provide reference for practical engineering design and application.