The Mechanical Behavior of Materials X

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Authors: Sung Choong Woo, Nam Seo Goo
Abstract: In this article, the flexural displacement of plate-type piezoelectric composite actuators (PCA) with various lay-up configurations has been evaluated considering the thermal deformations induced by a temperature drop using a three-dimensional finite element simulation. The results reveal that the flexural displacement of PCA subjected to electrical loadings is significantly affected by their lay-up configurations, the thickness of constituent PZT ceramic and applied boundary conditions, which is associated with the location of the neutral plane by moment equilibrium and the bending stiffness of PCA. For the displacement performance of PCA, an adequate choice of layup configuration together with the proper thickness of PZT ceramic is required.
Authors: Si Ying Chen, Chen Guang Huang, Tian Lan, Guo Qiang Ni
Abstract: In this paper, the real-time deformations and failures of LY12 samples loaded by an SHTB are investigated by an optical system, which consists of a high-speed camera, a flash lamp, a frame grabber and a synchronization device with the controlling accuracy of 1 microsecond. The deformation history of LY12 is obtained with a time interval of 10μs and the result is compared with that acquired by classic Hopkinson method at the same time. Besides, two different failure modes and the crack propagation velocity of LY12 specimen are detected in impact tensile process. The fracture textures after working are also surveyed by SEM and it shows that the dynamic fracture mode is affected by the microstructure of materials.
Authors: Choul Jun Choi, Jae Yeol Kim, Seung Hyun Choi
Abstract: The Infrared Camera usually detects only Infrared waves emitted from the light in order to illustrate the temperature distribution. An Infrared diagnosis system can be applied to various fields. But the defect discrimination can be automatic or mechanized in the shoes total inspection system. The thermal images of the specimens were analyzed. In shoes, weak bonding due to the separation of the bonded parts delamination causes defects. The most serious defect occurs in the bonding between the outer covering of the shoe and the sole, and to up now, this defect has been detected only by inspection with the naked eye. This study introduces a method for special shoes nondestructive total inspection. Performance of the proposed method is shown through thermo-Image. In search of superior inspection methods, we evaluated an applicable non-destructive inspection method and also carried out basic research for developing an innovative nondestructive inspection system for shoes. The total inspection system using infrared thermal camera for special shoes, its applicability, and system configuration are introduced.
Authors: Masakazu Kobayashi, Hiroyuki Toda, Tomomi Ohgaki, Kentaro Uesugi, David S. Wilkinson, Toshiro Kobayashi, Yoshimitsu Aoki
Abstract: The local elastic and plastic strain during deformation are very complicated and different form the macroscopic strain, because most materials have inhomogeneous microstructure. In this study, local strain distribution in three dimensions has been measured using the new developed method based on image analysis in high-resolution synchrotron radiation computed tomography (SR-CT). Model and practical specimens, which made of cupper alloy and aluminum alloy, respectively, were prepared for a development procedure and application of local strain measurements. Gauging intervals of microstructural features before and after deformation gave us information of inhomogeneous local strain distribution in three dimensions. High strain was observed in a necking region appeared after tensile deformation in the model sample. A combination of non-destructive measurements by SR-CT and three-dimensional analysis revealed inhomogeneous strain distributions in practical aluminum samples.
Authors: Jung Hwa Hong, Young Hwan Park
Abstract: Experimental measurement of pore pressure generation in lacunocanalicular network of trabeculae is never measured, although the characteristics could be important for bone remodeling. In this study, the pore pressure generation in micro-trabecular specimens within the elastic range was measured in vitro using a specially designed micro-experimental setup and a MEMS based micro-pressure transducer. Then, a quasi-static loading (9㎛/min) was applied up to the strain of 0.4 % with measuring pore pressure generations in the undrained and drained conditions. 49.2 ± 4.45 KPa of pore pressure generation at the 0.4% strain was found in the undrained condition. In contrast, no pore pressure generation was measured in the drained condition. The result could let us know the amount of a possible maximum pore pressure generation in lacunocanalicular network of trabeculae within the elastic range.
Authors: Jung Hwa Hong, Young Hwan Park
Abstract: The mechanical performance of cancellous bone is characterized using experimental measure of parameters (elastic moduli, permeability, etc.) which apply poroelasticity theory. Poroelastic investigations of bone are being extended to investigations of micro-mechanisms of remodeling processes and transport of metabolic product in bone. To understand physiological and pathological behavior of human skeletal system, the accurate measurement of biomechanical properties for bone is the one of important works. Particularly, the microscopic measurement is very important since the biomechanical behavior at the small scale of bone could be closely related to the remodeling of bone. But microscopic measurement of permeability coefficient which is one of important parameter of poroelasticity theory was never measured. In this study, a small scale permeability testing machine was developed to measure accurate coefficient of microscopic specimen permeability. Total of twenty one cylindrical cancellous specimens with a diameter of 500  from seven fresh male and female lumbar vertebrae (14, 39, 59, 61, 69, 75, and 77 years) were fabricated using a micro-milling machine having a resolution of 10 . To determine the directional permeability, bone coordinate was set to be x1 (longitudinal axis) and others were set as x2 (posteroanterior axis) and x3 (latero-medial axis). The measured mean permeability (± SD) values of each direction from x1 to x3 were 9 5.56 10− × (S.D. ± 10 7.10 10− × ), 9 6.66 10− × (S.D. ± 10 6.56 10− × ), and 9 7.04 10− × (S.D. ± 10 8.47 10− × ) m2/Pa/sec, respectively. Mean value in the x1 direction of specimens were the smallest (p<0.01) in comparison to x2 and x3 directions.
Authors: David Sunjaya, Tao Wei, Robert Harrison, Wing Yiu Yeung
Abstract: The small punch test (SPT) is a relatively new mechanical testing technique capable of utilising small disk-shaped specimens to determine the mechanical behaviour of the test materials. From the test data, fracture properties in particular the equivalent fracture strain (εqf) can be determined and the elastic-plastic fracture toughness of a material can be characterised. Finite element analyses (FEA) of the small punch tests have been performed for the 304H stainless steel in this study. 304H stainless steel was isothermally aged at 650, 700 and 750oC for durations up to 200 hours. Small punch tests were performed to assess the mechanical properties of the heat treated materials. Using the input of the true stress-strain curves of material constitutive behaviour, the theoretical load vs punch displacement curves calculated from the FEA models were found in good agreement with the experimental results. The fracture thickness of the small punch tested specimens and the equivalent fracture strain were also be determined for the test materials.
Authors: Kenichi Ohi, Jae Hyouk Choi
Abstract: An adaptive loading system is developed to examine a design point of multi-story steel test frames subjected to uncertain load pattern. Lateral loads are given as a random combination of basic load patterns, and the system drives a test frame to the most likely failure situation. Two-story steel moment resisting frames are tested considering a failure mechanism formation of plastic collapse as a tentative limit state. A random 2-dof lateral force is given by a random combination of two basic load patterns, which are arranged to represent elastic earthquake load effects. Hybrid design point search or adaptive loading tests on the 2-story frame are performed, and the detected likely failure mechanisms are compared with the results of pseudo-dynamic response tests to deterministic excitations.
Authors: Je Wook Chae, Eui Jung Choi
Abstract: In the conventional weapon system, such as gun and small arms, it is a general trend that for maximization of its performance and enhancement of its effectiveness, the fire control system; FCS is developed and applied with the guns and small arms in the world. The FCS of the small arms for infantry man is composed of a few of sensors for acquisition of input data of FCS, such as range measurement, position sensing of weapon, temperature, etc., computer, displayer and power pack, and also the air burst ammunition is developed in parallel for the maximization of effectiveness. Since setting fuse of the flight time for the air burst ammunition is adapted for next rifle, the measuring device of the muzzle velocity is needed to overcome the variation of muzzle velocity due to producing procedures and the differences of the using temperatures and so maintain the burst position accuracy. This paper contained the technical information on the development of the measuring device of muzzle velocity, which designed in compact & light weight configuration with reliability and accuracy.
Authors: K.S. Choi, Y. Choi, Bong Goo Kim, Y.W. Lee
Abstract: Small specimen with simple geometry has advantage for irradiation tests because the tests have limits for experiments and nuclear wastes after irradiation tests. In this study, a kinetic indentation technique is applied to evaluate mechanical properties of coated layers of a particle fuel of a high temperature gas cooled reactor. Hardness of buffer, IPyC and OPyC are 0.55, 0.874 and 2.726 GPa, respectively. The density, strength and friction coefficient estimated by kinetic indentation method are 1.08, 1.15 and 1.81 g/cm3, and 174, 291 and 606 MPa, and 0.51, 0.45 and 0.4, respectively.

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