• 터널과지하공간
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• 제2권2호
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• pp.237-250
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• 1992

The cavities formed by the excavation of coal seam cause unstable within rock body, leading to large displacement around adjacent roadway. This displacement brings the closure of roadway and deformation of support. Therefore, it is necessary to understand and predict the deformation characteristics of roadway while coal seam is under excavation. In this study, the observed displacements are compared with the calculated ones through the analysis using Linear Boundary Element Mothod under the elastostatic conditions, in order to determine the virgin stress state and deformation modulus which affect the deformation characteristices.

• Structural Monitoring and Maintenance
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• 제7권1호
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• pp.1-12
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• 2020

Railway tracks are the direct supporting structures of the trains, which are vulnerable to produce large deformation under the temperature stress or subgrade settlement. The health status of track is critical, and the track should be routinely monitored to improve safety, lower the risk of excess deformation and provide reliable maintenance strategy. In this paper, the distributed optical fiber sensor was proposed to monitor the continuous deformation of the track. In order to validate the feasibility of the monitoring method, two deformation monitoring tests on one steel rail model in laboratory and on one real railway tack in outdoor were conducted respectively. In the model test, the working conditions of simply supported beam and continuous beam in the rail model under several concentrated loads were set to simulate different stress conditions of the real rail, respectively. In order to evaluate the monitoring accuracy, one distributed optical fiber sensor and one fiber Bragg grating (FBG) sensor were installed on the lower surface of the rail model, the strain measured by FBG sensor and the strain calculated from FEA were taken as measurement references. The model test results show that the strain measured by distributed optical fiber sensor has a good agreement with those measured by FBG sensor and FEA. In the outdoor test, the real track suffered from displacement and temperature loads. The distributed optical fiber sensor installed on the rail can monitor the corresponding strain and temperature with a good accuracy.

• Journal of Mechanical Science and Technology
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• 제19권7호
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• pp.1432-1440
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• 2005

High-temperature rupture behavior of 5083-Al alloy was tested for failure at 548K under multiaxial stress conditions: uniaxial tension using smooth bar specimens, biaxial shearing using double shear bar specimens, and triaxial tension using notched bar specimens. Rupture times were compared for uniaxial, biaxial, and triaxial stress conditions with respect to the maximum principal stress, the von Mises effective stress, and the principal facet stress. The results indicate that the von Mises effective and principal facet stresses give good correlation for the material investigated, and these parameters can predict creep life data under the multiaxial stress states with the rupture data obtained from specimens under the uniaxial stress. The results suggest that the creep rupture of this alloy under the testing condition is controlled by cavitation coupled with highly localized deformation process, such as grain boundary sliding. It is also conceivable that strain softening controls the highly localized deformation modes which result in cavitation damage in controlling rupture time of this alloy.

• Steel and Composite Structures
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• 제25권1호
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• pp.67-78
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• 2017

In this study, free vibration of functionally graded (FG) micro/nanobeams based on nonlocal third-order shear deformation theory and under different boundary conditions is investigated by applying the differential quadrature method. Third-order shear deformation theory can consider the both small-scale effects and quadratic variation of shear strain and hence shear stress along the FG nanobeam thickness. The governing equations are obtained by using the Hamilton's principle, based on third-order shear deformation beam theory. The differential quadrature (DQ) method is used to discretize the model and attain the natural frequencies and mode shapes. The properties of FG micro/nanobeam are assumed to be chanfged along the thickness direction based on the simple power law distribution. The effects of various parameters such as the nonlocal parameter, gradient index, boundary conditions and mode number on the vibration characteristics of FG micro/nanobeams are discussed in detail.

• 한국정밀공학회지
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• 제20권11호
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• pp.158-165
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• 2003

A specific experimental method, the Split Hopkinson pressure bar (SHPB) technique has been widely used to determine the dynamic material properties under the impact compressive loading conditions with strain rate of the order of 10$^3$/s∼l0$^4$/s. In this paper, dynamic deformation behaviors of rubber materials widely used for the isolation of vibration from structure under varying dynamic loading are determined by using plastic SHPB technique. A transition point to scope with the dynamic deformation behavior of rubber-like material is defined in this paper and used to characterize the specifics of the dynamic deformation of rubber materials.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1251-1252
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• 2006

In order to investigate 95% retained critical current of Bi-2223/Ag tapes under various stress-strain conditions, load cell attached tension and bending apparatus was used. The critical current of stress-strained tape was degraded below 95% retained critical current when tension and bending was simultaneously applied together. But only one of this tension or bending did not degrade the tape below 95% retained critical current. Deformation temperature was important to maintain the 95% retained Ic of Bi-2223/Ag tapes after bending or tension deformation because mechanical strength of tapes can be changed drastically between room temperature and 77 K.

• 대한치과기공학회지
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• 제46권2호
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• pp.21-27
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• 2024

Purpose: This study aimed to analyze the stress distribution and deformation in implant abutments made from titanium (Ti-6Al-4V), zirconia, and polyetheretherketone (PEEK), including their screws and fixtures, under various loading conditions using finite element analysis (FEA). Methods: Three-dimensional models of the mandible with implant abutments were created using Siemens NX software (NX10.0.0.24, Siemens). FEA was conducted using Abaqus to simulate occlusal loads and assess stress distribution and deformation. Material properties such as Young's modulus and Poisson's ratio were assigned to each component based on literature and experimental data. Results: The FEA results revealed distinct stress distribution patterns among the materials. Titanium alloy abutments exhibited the highest stress resistance and the most uniform stress distribution, making them highly suitable for long-term stability. Zirconia abutments showed strong mechanical properties with higher stress concentration, indicating potential vulnerability to fracture despite their aesthetic advantages. PEEK abutments demonstrated the least stress resistance and higher deformation compared to other abutment materials, but offered superior shock absorption, though they posed a higher risk of mechanical failure under high load conditions. Conclusion: The study emphasizes the importance of selecting appropriate materials for dental implants. Titanium offers durability and uniform stress distribution, making it highly suitable for long-term stability. Zirconia provides aesthetic benefits but has a higher risk of fracture compared to titanium. PEEK excels in shock absorption but has a higher risk of mechanical failure compared to both titanium and zirconia. These insights can guide improved implant designs and material choices for various clinical needs.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 춘계학술대회논문집
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• pp.48-54
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• 1996

The continuous deformation , multistage deformation and stress relaxation were carried out to investigate the strain induced procipitation by torsion tests in the range of 1000∼800$^{\circ}C$, 0.05/sec∼5/sec for V-microalloyed steel. The starting temperature and time for the initiation of precipitation were determined by stress relaxation tests and the distribution of percipitates increased at higher strain rate and the mean size of precipitates was found to be about 50nm. The precipitation starting time decreased with increasing strain rate from 0.05/sec to 5 /sec and pre-strain. The effect of deformation conditions on the no-recrystallization temperature(Tnr) was determined in the multistage deformation with declining temerature. The Tnr decreased with increasing strain and strain rae. In the controlled rolling, grain refinement and precpitation hardening effects could be achieved by the alternative large pass strain at the latter half pass stage under the condition of low temperature and high strain rate.

• 한국CDE학회논문집
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• 제20권3호
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• pp.230-237
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• 2015

Soil deformation on the off-load ground is significantly affected by soil conditions, such as soil type, water content, and etc. Thus, the soil characteristics should be estimated for predicting vehicle movements on the off-load conditions. The plate-sinkage test, a widely-used experimental test for predicting the wheel-soil interaction, provides the soil characteristic parameters from the relationship between soil stress and plate sinkage. In this study, soil stress under the plate-sinkage situation is calculated by the DEM (Discrete Element Method) model. We developed a virtual soil bin with DEM to obtain the vertical reaction forces under the plate pressing the soil surface. Also parametric studies to investigate effects of DEM model parameters, such as, particle density, Young's modulus, dynamic friction, rolling friction, and adhesion, on the characteristic soil parameters were performed.

• 수산해양기술연구
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• 제26권4호
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• pp.380-386
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• 1990

The high stress, low cycle fatigue test were carried out on HT80 plates with artificial part-through notch. The LBB conditions by the net section stress approach was examined in detail. Finite element methods for the state of deformation were also applied and the results were compared with the results from experiments. From the test results, it was noted that the LBB condition in fatigue test was dependent upon the maximun load change before and after the crack penetration. The LBB criterion By the net section stress approach were slightly dependent on initial crack size. It was shown that the state of deformation can be used to predict whether the component is likely to show LBB condition or they will be broken rapidly.