• Nuclear Engineering and Technology
• /
• 제54권5호
• /
• pp.1549-1559
• /
• 2022

As an accident tolerant fuel (ATF) concept, oxide dispersion strengthened Zircaloy-4 (ODS Zry-4) cladding has been developed to enhance the mechanical properties of cladding using laser processing technology. In this study, a simulation technique was established to investigate the mechanical properties and effects of Y₂O₃ particles for the ODS Zry-4. A 3D representative volume element (RVE) model was developed considering the parameters of the size, shape, distribution and volume fraction (VF) of the Y₂O₃ particles. From the 3D RVE model, the Young's modulus, coefficient of thermal expansion (CTE) and creep strain rate of the ODS Zry-4 were effectively calculated. It was observed that the VF of Y₂O₃ particles had a significant effect on the aforementioned mechanical properties. In addition, the predicted properties of ODS Zry-4 were applied to a simulation model to investigate cladding deformation under a transient condition. The ODS Zry-4 cladding showed better performance, such as a delay in large deformation compared to Zry-4 cladding, which was also found experimentally. Accordingly, it is expected that the simulation approach developed here can be efficiently employed to predict more properties and to provide useful information with which to improve ODS Zry-4.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1998년도 가을 학술발표회 논문집
• /
• pp.201-207
• /
• 1998

In this study, a geometric nonlinear analysis formulation for spatial frames is developed using the 3D stability functions. For the formulation, the relationships of local and global coordinate systems in force, deformation, and the initial and current configurations of a frame are derived. The force-deformation relationship in global coordinate system is derived as well. The developed formulation is verified in each derivation by reducing the derived equations into 2D equations. The gradual plastification of connections and critical sections can be implemented effectively to this formulation for the complete second order inelastic advanced analysis of spatial frames.

• 한국생활과학회지
• /
• 제21권3호
• /
• pp.551-565
• /
• 2012

The primary goal of this study was to provide a systematic methodology of utilizing 3D technology for tight-fit performance sportswear using information of skin deformation in various posture. Technical tools used in this study are Cyberware whole body scanner, RapidForm2004, 2C-AN 3D pattern development program, and YukaCAD. Analysis of the 3D skin deformation while knee joint was bent from $0^{\circ}$ to $60^{\circ}$ revealed that the length of dermatomes L4 was remained consistent during knee bending. Therefore, L4 was chosen as a major cutting line. To develop a highly ergonomic pattern, replicas of static and dynamic postures were developed and integrated using two methods, one is morphing method (Sqirlz Morph), and the other is AutoCAD. Experimental tight-fit garments called 'Derm-Mov Pattern' was designed using dematomes L4, L2, and inner line under knee and compared with four other patterns. As results, AutoCAD was appropriate as a integrating method of various postures. In wear test, 'Derm-Mov Pattern' was rated high (p < .001), in terms of pressure comfort especially around front crotch area. However, wear sensation was not signipicantly different in other area due to highly extensible property of materials. Pressure distribution was relatively even in these experimental garments.

• 대한기계학회논문집A
• /
• 제33권5호
• /
• pp.489-495
• /
• 2009

A novel technique to measuret of viscoelastic properties of polymers is proposed to investigate complex Poisson's ratio as a function of frequency. The forced vibration responses for the samples under the normal and the shear deformation are to be measured with varying load masses. The measured data were used to obtain the viscoelastic properties of the material based on an accurate 2D numerical deformation model of the sample. The 2D model enabled us to exclude data correction by the empirical form factor used in 1D model. Comprehensive measurements of viscoelastic properties of two slightly varied silicone RTV rubber ($Silastic^{(R)}$ S2) compositions were performed. Standard composition (90% PDMS polymer + 10% catalyst) and modified composition (92.5% polymer + 7.5% catalyst) were tested in temperature range from $30^{\circ}C$ to $70^{\circ}C$. Shear modulus, modulus of elasticity, loss factor, and both the real and the imaginary parts of the Poisson's ratio were determined for frequencies from 50 to 400Hz in the linear deformation regime (at relative deformations $10^{-4}{\sim}10^{-3}$).

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2006년도 춘계학술대회 논문집
• /
• pp.168-171
• /
• 2006

Hot deformation behavior of A350 LF2 alloy was characterized by compression tests in the temperature range of 800-$1250^{\circ}C$ and the strain rate range of $0.001-10s^{-1}$. The microstructural evolution during hot compression was investigated and deformation mechanisms were analyzed by constructing processing map. Processing maps were generated using the dynamic material model (DMM). The combination of dynamic material model and Ziegler's instability criterion was applied to predict an optimum condition and unstable regions for hot forming.

• 동력기계공학회지
• /
• 제7권2호
• /
• pp.56-60
• /
• 2003

Recently the plastic fuel tube is usually used to reduce production cost and weight in automobiles. These days, material used to plastic fuel tube is the polyamide12. The fuel tube is made of the PA12. Post deformation of the tube has been changed by environmental temperature. So, it is important to prevent post deformation. The experiment is performed to investigate post deformation of the tube produced by each bending process. In this study, the results we obtained are used to bending process system for post deformation as the environmental temperature of the tube. It turned out that the method of steam heating and air cooling was shown less deformation than other methods.

• Structural Engineering and Mechanics
• /
• 제56권2호
• /
• pp.223-240
• /
• 2015

In this work, a nonlocal quasi-3D trigonometric plate theory for micro/nanoscale plates is proposed. In order to introduce the size influences, the Eringen's nonlocal elasticity theory is utilized. In addition, the theory considers both shear deformation and thickness stretching effects by a trigonometric variation of all displacements within the thickness, and respects the stress-free boundary conditions on the top and bottom surfaces of the plate without considering the shear correction factor. The advantage of this theory is that, in addition to considering the small scale and thickness stretching effects (${\varepsilon}_z{\neq}0$), the displacement field is modelled with only 5 unknowns as the first order shear deformation theory (FSDT). Analytical solutions for vibration of simply supported micro/nanoscale plates are illustrated, and the computed results are compared with the available solutions in the literature and finite element model using ABAQUS software package. The influences of the nonlocal parameter, shear deformation and thickness stretching on the vibration behaviors of the micro/nanoscale plates are examined.

• Steel and Composite Structures
• /
• 제25권1호
• /
• pp.19-34
• /
• 2017

The widespread damage to steel Moment Resisting Frames (MRFs) in past major earthquakes have underscored the need to understand the nonlinear inelastic behaviour of such systems. To assess the seismic performance of steel MRF, it is essential to model the nonlinear force-deformation behaviour of beam to column joints. To determine the extent of inelasticity in a beam to column joint, nonlinear finite element analysis is generally carried out, which is computationally involved and demanding. In order to obviate the need of such elaborate analyses, a simplistic method to predict the force-deformation behaviour is required. In this study, a simple, mechanics driven, hand calculation method is proposed to obtain the forcedeformation behaviour of strong axis beam to column moment joints. The force-deformation behaviour for twenty-five interior and exterior beam to column joints, having column to beam strength ratios ranging from 1.2 to 10.99 and 2.4 to 22, respectively, have been obtained. The force-deformation behaviour predicted using the proposed method is compared with the results of finite element analyses. The results show that the proposed method predicts the force-deformation behaviour fairly accurately, with much lesser computational effort. Further the proposed method has been used to conduct Nonlinear Dynamic Time History Analyses of two benchmark frames; close correspondence of results obtained with published results establishes the usefulness and computational accuracy of the method.

• 소성∙가공
• /
• 제32권4호
• /
• pp.221-227
• /
• 2023

While tube bending is a conventional forming technique, it is still used to make curved products for load-bearing members or aesthetically pleasing parts in various manufacturing industries such as automotive, aerospace, and others. Whole or local deformation of the final product such as springback, distortion, or local buckling are of interest in metal forming or precision manufacturing. In this paper, the factors affecting the cross-sectional deformation are explored. A 5-axis stretch bending machine was used for two-dimensional bending with extruded AA6082-T4 rectangular tubes. Three different bending sequences were employed: stretch before bending, stretch after bending, simultaneous bending and stretch. Furthermore, by considering both the stretch and bending angle, cross-sectional deformation was also analyzed. It was observed that employing stretch bending techniques can effectively reduce cross-sectional deformation and contribute to overall quality enhancement. Through this study, it was revealed that these factors have an impact on the cross-sectional deformation of the tubes.

• 한국도로학회논문집
• /
• 제9권4호
• /
• pp.193-204
• /
• 2007

변형강도($S_D$)는 고온에서 아스팔트 혼합물의 소성변형특성과 상관관계가 높은 특성이며, APA 시험기는 아스팔트 혼합물의 소성변형저항성 평가에 널리 이용된다. 따라서 $S_D$를 이용한 아스팔트 혼합물의 소성변형저항성 추정에 상응하는 값으로 APA 시험 결과가 사용되었으며 $S_D$와 APA의 상관관계를 설정하기 위하여 많은 데이터가 수집되었다. 아스팔트 공시체를 $60^{\circ}C$에 30분간 수침한 후 50mm/min의 하중을 가하여 최대하중 P와 그때의 수직변형 y로 부터 $S_D$를 계산하였다. 같은 혼합물에 대하여 APA 시험도 수행되었다. APA 침하깊이와 $S_D$간의 회귀분석을 수행하여 $R^2=0.76$이 얻어졌다. 이는 변형강도 시험이 아스팔트 혼합물의 고온변형 저항성을 추정 가능한 시험법임을 암시하는 것이다. 또한 회귀분석 모델을 이용하여 특정 등급도로의 표층 및 기층 혼합물 $S_D$의 임계값을 설정할 수 있음을 보였다. 이를 더 정교하게 연구하면 이 임계치는 특정층 포장혼합물의 하한치로 이용될 수 있을 것이다.