• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.393-399
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• 2017

In a reciprocating compressor, the piston and connecting rod are important parts. Excess mechanical stress on these parts may cause damage, and broken parts are expensive and difficult to replace. Therefore, it is necessary to analyze the mechanical stress affecting durability and longevity. The main purpose of this study was to identify locations of maximum stress on pistons and connecting rods. Based on dynamic calculation of the working process of a specific air compressor, an analysis of piston and connecting rod performance has been completed. A three-dimensional model for the air compressor's pistons and connecting rods was built separately, and FEM analysis of these components was carried out using a numerical method. The pistons were loaded by pressure which was changed according to crankshaft angle without thermal boundary conditions. The simulation results were used to predict and estimate stress concentration as well as the value of this stress on pistons and connecting rods. The maximum equivalent stress calculated are over 190 MPa on pistons and 123 MPa on connecting rods at crank angle $135^{\circ}$ and $225^{\circ}$ but these are under tensile yield strength. Besides, the calculated safety factors of connecting rods and pistons is higher than 1. Moreover, the results obtained can be used to provide manufacturers with references to optimize the design of pistons and connecting rods for reciprocating compressors.

• Restorative Dentistry and Endodontics
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• v.33 no.4
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• pp.323-331
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• 2008

Flexibility and fracture properties determine the performance of NiTi rotary instruments. The purpose of this study was to evaluate how geometrical differences between three NiTi instruments affect the deformation and stress distributions under bending and torsional conditions using finite element analysis. Three NiTi files (ProFile .06 / #30, F3 of ProTaper and ProTaper Universal) were scanned using a Micro-CT. The obtained structural geometries were meshed with linear, eight-noded hexahedral elements. The mechanical behavior (deformation and von Mises equivalent stress) of the three endodontic instruments were analyzed under four bending and rotational conditions using ABAQUS finite element analysis software. The nonlinear mechanical behavior of the NiTi was taken into account. The U-shaped cross sectional geometry of ProFile showed the highest flexibility of the three file models. The ProTaper, which has a convex triangular cross-section, was the most stiff file model. For the same deflection, the ProTaper required more force to reach the same deflection as the other models, and needed more torque than other models for the same amount of rotation. The highest von Mises stress value was found at the groove area in the cross-section of the ProTaper Universal. Under torsion, all files showed highest stresses at their groove area. The ProFile showed highest von Mises stress value under the same torsional moment while the ProTaper Universal showed the highest value under same rotational angle.

• Journal of the Korean GEO-environmental Society
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• v.23 no.2
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• pp.13-23
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• 2022

The ground-structure interaction of the bridge foundation has been pointed out as a major factor influencing the behavior of the bridge during earthquakes. In this study, the effect of characteristics of ground and bridge foundation on the earthquake vulnerability is investigated. From the pseudo-static analysis, it is confirmed that non-linearity becomes lesser and horizontal load becomes greater when surcharge is considered. It is also found that as the ground worsens and the size of foundation decreases, horizontal load reduces. To derive reasonable structural model for bridge foundation, fragility curve is obtained considering four conditions (fixed condition, equivalent linear condition, non-linear without surchage condition, non-linear with surcharge condition) and compared. Seismic analysis is performed on single pier with Opensees. From the earthquake vulnerability analysis, it is found that shallow foundation can be assumed as fixed condition. In conservative approach, stiffness of spring can be obtained based on Korean highway bridge design code for pile foundation which can consider the ground condition.