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Chobin MAKABE, Muhammed SOHEI, Takashi FUNAKOSHI, Genkichi FUJIWARA
Article type: Article
Session ID: 1052
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Rivet joint has been used to connect plates or frames. Specially, countersunk head rivets have been used in airplane. Failure of a riveted plates in service occurred due to crack initiation from rivetting holes. The stress concentration at hole edge is one of main causes of shortening crcak initiation life of rivetted plate when cyclic stress was applied. In the present study, to make longer the fatigue life of rivetted plate which is used countersunk head rivet, shape of the countersink and the rivet head were improved. The corner of root of the countersink was rounded, and stress concentration at that point was reduced. The experimental results showed that the fatigue life of the rivetted plate was improved where improved rivet was used.
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Hiroshi MATSUNO
Article type: Article
Session ID: 1053
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Fatigue strength of heat- and surface-treated steels is investigated by using equivalent stress ratios (R_<EQ>-ratios) which have been proposed as parameters for correspondence between fatigue test conditions of notched and unnotched specimens. Diagrams are exhibited by relations between R_<EQ>-ratios and notch-root-concentrated stress ranges Δσ_<NR> and characterized by two type of fatigue strength σ_<w1> a nd σ_<w2>. In usually annealed, normalized and tempered steels, fatigue strength transfers smoothly from σ_<w1>, to σ_<w2> lowering R_<EQ>-ratio. In severely heat- and surface-treated steels, the transition from σ_<w1> to σ_<w2> brings about a sharp decrease in fatigue strength. So, mechanisms of fatigue strength σ_<w1> and σ_<w2> are reconsidered in the present paper. As a result, it is concluded that fatigue strength σ_<w1> a nd σ_<w2> do not correspond to fatigue processes of stage I and II, but depends upon single-slip and double-slip mechanism related with morphology of fatigue slip bands, respectively.
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Katsuaki FURUKAWA, [in Japanese]
Article type: Article
Session ID: 1054
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Although extrusion and intrusion has been investigated in many researches, the stress field in the first stage has not been clarified. Therefore, in this study, the stress field in initial crack occurrence at notch was investigated with notched specimen The stress field at notch was measured by strain gauge pasted on the notch. Also the mechanism of crack occurrence was investigated by measuring the change of stress field at notch.
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Ken-ichi OHGUCHI, Katsuhiko SASAKI, Setsuo ASO
Article type: Article
Session ID: 1055
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Solder joints in electronic package must employ lead-free solder alloys for environmental concerns. Since the solder joints are often subjected to cyclic loadings, the lead-free solder alloys must have enough fatigue strength. Therefore, the fatigue characteristics of the lead-free solder alloys must be investigated by conducting fatigue tests. Especially, the tests should be conducted considering the strain rate effect on the fatigue life because the deformation of solder alloys always shows remarkable time dependency due to creep deformation under ordinary circumstances. In this study, the fatigue tests using Sn-3.0Ag-0.5Cu lead-free solder were conducted by the cyclic tension-compression loadings whose strain rates were different in each loading direction. The creep strains in the hysteresis loop caused by the cyclic loading were estimated by conducting the cyclic stepped ramp loading test. Also the relationship between the estimated creep strain and the fatigue life was discussed.
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Akiyoshi ONUKI, Hiroaki KOHAMA
Article type: Article
Session ID: 1056
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The spheroidal cast iron is widely used in many purposes, especially for high stressed parts. It is very difficult to detect the internal defect of such cast iron products, by means of NDT equipment. In the case of overloading or low cycle fatigue, the stress-strain behavior is observed in loading state but the life is determined for the failure, while outer cracks could be found easily. The MDK sensor is a kind of elector-magnetic detector using the inductive coils, like the Eddy-current sensor. In this research, a MDK Magnetic Sensor is used to inspect the microscopic plastic deformation or cracks around graphite nodules, and the relations between the loading or deformation and the MDK value. The availability of the MDK Sensor for the nondestructive determining of low cycle fatigue of the SGCI is discussed.
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Shigeaki So, Yoshihito Kuroshima
Article type: Article
Session ID: 1057
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Pure mode II propagation was realized under cyclic torsion load in acrylic round bar bonded low carbon steel, and anomalous behavior occurred in the film. In this study, behavior of the film was discussed. As a result, crack occurred in ferrite grain sandwiched in pearlite grains. The propagation behavior of fatigue crack depended on crack length occurring between pearlite grains. Definite deformation was observed in a round bar. But deformation was hardly observed in the film.
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Tatsuo Sakai, Yuki Nakamura, Hideo Hirano
Article type: Article
Session ID: 1058
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Alumite treatment is one of typical surface treatments for aluminum alloy and it provides oxide layer (alumite) on the surface. The method has been widely used for aluminum alloy, because the alumite has some excellent characteristics such as wear resistance, electric resistance and so on. Thus, fatigue tests were carried out for specimens having two different alumite treatments and without the treatment by means of a dual-spindle rotating bending fatigue testing machine. Fracture surfaces of all the failed specimens were observed by using SEM, and the fatigue fracture mechanisms were discussed from a viewpoint of the fractography paying an attention to the effect of the alumite treatments.
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Shintaro IKEDA, Takashi NAKAMURA, Hiroyuki OGUMA, Kensuke NAKAMURA
Article type: Article
Session ID: 1059
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Uniaxial tension-compression fatigue tests of Ni-Cr-Mo steel "SNCM439" tempered at different temperatures were conducted in air environment. Effects of tempering temperature on fatigue properties were investigated. As a result, the following conclusions were obtained; (1) Fatigue limit of surface fracture was proportional to Vickers hardness, and the relation was in good agreement with the expression σ≈ 1.6HV. (2) In very high cycle region, the fatigue strength of the material tempered at 433K was lower than that tempered at 573K. In other words, the harder material showed lower fatigue strength. (3)The kinds of inclusions, which can be interior fracture origins, probably change between different tempering temperature.
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Takayoshi TANAKA, Seiji IOKA, Shiro KUBO
Article type: Article
Session ID: 1060
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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We call it governing equation inverse problem to estimate governing equation. So far, the domain-type inverse analysis method to estimate governing equation was proposed. In the meantime, we propose the boundary-type inverse analysis method newly. It has some advantages compared to the domain-type. For example, it makes analysis easier, it need less data, etc. Therefore we consider the establishment of boundary integral-type inverse analysis method. In this study, we consider 2-dimentional potential problem and propose the method to estimate modulus of governing differential equation by the boundary integration. As a result, not only the case that coordinate axis and orthotropic anisotropy axis are corresponding but also the case not corresponding, we got quite good estimation result. Moreover, the case of boundary observed values include observed noise, we got relatively good estimation result.
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Takahiko Kurahashi
Article type: Article
Session ID: 1061
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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This paper describes numerical experiments for an inverse problem using the spectral and the adjoint variable methods. If the inverse problem is solved based on the adjoint variable method, the state equation which is introduced as the governing equation for the numerical model and the adjoint equation is computed by applying numerical methods. In this study, the spectral method is employed as the computational scheme for the state and the adjoint equations. In case that the spectral method is employed for the computation of the partial differential equation, the accuracy of the solution depends on the wave number. I therefore investigate the dependency of the solution for the wave number by numerical experiments. A waveform inversion problem is employed as the inverse problem.
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Seiji IOKA, Kazushi TAKAHASHI, Shiro KUBO
Article type: Article
Session ID: 1062
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Inverse boundary value problem involves incompletely-prescribed boundary. The problem has an ill-posedness. Alternating boundary element inverse scheme can be one of the regularization methods. In this study, contact stress distribution on the incompletely-prescribed boundary is estimated by applying the alternating boundary element inverse scheme with the quadratic elements. Estimated distributions are compared with these obtained by using the linear elements.
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Arata MASUDA, Muneaki NAKAMURA, Daisuke IBA, Akira SONE
Article type: Article
Session ID: 1063
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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In this paper, a method to identify the geometrical shape and the location of the defect embedded in a concrete structure by processing the thermal image of the structural surface acquired by infrared thermography is presented. In the proposed method, the structure is modeled as a homogeneous infinite plate whose boundary condition on the observed surface is known. A layer-by-layer inverse analysis using a regularized interlayer transfer matrix based on 2D Fourier transform is carried out to obtain the sharper image of the defect as well as the depth of the damaged layer. The estimated depth information mapped on the image plane has resulted in a depth image which can display the shape of the defects as well as their depth simultaneously. An improved method introducing equivalent virtual heat sources that prevent the "boundary artifact" caused by the heat flux across the image boundary is presented.
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Takahide Sakagami, Shiro Kubo, Naoki Yamaguchi
Article type: Article
Session ID: 1064
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Plastic zone identification was conducted by 2f lock-in technique, in which temperature change due to plastic heat generation was separately identified from thermoelastic temperature change under variable loading. Accuracy improvement was performed using motion compensation based on modified digital image correlation, inverse thermal conduction analysis and noise reduction based on mollification method.
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Takeharu HAYASHI, Yoshinori EBIHARA, Hirohiko WATABABE, Tastuhiko ASAI
Article type: Article
Session ID: 1107
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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When we estimate the fatigue life of solder joints, we have to conduct FE analysis with a constitutive model which can exhibit dynamic property of Pb free solder. We proposed a creep-plasticity unified viscoplastic constitutive model with Armstrong-Frederick type nonlinear kinematic hardening rule which can describe temperature and rate dependent cyclic stress-strain relations. Then, we implemented the proposed model into finite element code MARC and analyzed tension tests and the tension-compression tests of Sn3.5Ag0.5Cu0.07Ni0.01Ge solder. We compared test data with analytical FE results of the proposed model, anand model and classical creep-prasticity decoupled model. It was confirmed that analytical results using the proposed model were in good agreements with the experimental results.
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Yasuhiro EJIRI, Hiroyuki NAKANO, Takao MORI, Toshihiko SAYAMA, Takeshi ...
Article type: Article
Session ID: 1108
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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In Sn-3.0Ag-0.5Cu lead-free solder joints of chip type resisters, a prediction of thermal fatigue crack initiation lifetime was carried out and its accuracy was also discussed. The authors have been focused on the phase growth phenomena in solder joints due to thermal cyclic loading. The prediction was based on the experimental relation between the increase in the phase growth parameter S and the crack initiation lifetime N_1. The predicted lifetime was compared with experimentally determined lifetime by SEM observations. Consequently, the accuracy is that the measured lifetime exists in the range of 90% confidence limits of the predicted lifetime.
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Akihiko TOSAKA, Qiang YU, Tadahiro Shibutani, Masaki Shiratori
Article type: Article
Session ID: 1109
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Solder joints in the advanced electronic packaging such as 3D packaging are subjected to multi-load consisting of thermal cycling and other mechanical constraints. Since multi-loads may produce ratchet influencing thermal fatigue reliability, a method evaluating thermal fatigue life under multi-loadings should be developed. In this paper, three-point bending tests of the ball grid array (BGA) package were carried out. Experiments were performed with several average stress levels. Number of cycles to failure in experiments decreases as a function of the average stress. FEA qualification was carried out to estimate the fatigue life in three-point bending tests. Error of computational estimated life to the experimental result is big when the average stress is high. It implies that modified Manson-Coffin's law should be used for thermal fatigue life of solder joints under multi-loadings.
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Toshiaki MARUOKA, Qiang YU, Tadahiro SHIBUTANI, Akifumi TANAKA, Masaki ...
Article type: Article
Session ID: 1110
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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This paper presents mining the worst thermal fatigue life of solder joints on chip components used in vehicle electronics. Typical 36 cases with various solder shapes were examined. Thermal fatigue life to not only crack initiation but also crack propagation was evaluated by using the finite element method. When a crack propagates along the side of the component, the failure life in lead-free solder joints varies within 20 %. On the other side, when the crack propagates into a fillet of solder, the fatigue life drops. Since there is an interaction between two solder joints on the chip component, asymmetrical structure also affects the fatigue life. The worst fatigue life show the 80 % decrease compared with a standard model. It means that the shape of solder joints should be designed to control the failure mode.
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Kento KIMURA, Takao IWAMOTO, Shozo NAKAMURA
Article type: Article
Session ID: 1111
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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BGA type LSI package is composed by different materials in thermal mechanical properties. Therefore, destruction of a solder ball may arise with various thermal loads in a manufacture process and the environment. In this report, the thermal stress was analyzed by Finite Element Method from the viewpoint from which the optimization design indicator of BGA type LSI package was requested. Concretely, the thickness of the adhesive film included in the package was changed, and the amount of the maximum warp deformation, the maximum principal stress and the maximum shearing stress in the solder ball was examined in each cooling process of assuming the manufacturing process. It was clarified that the adhesive film thickness from 0.3 mm to 0.4 mm was preferable from the point of the maximum warp deformation, the maximum shearing stress and the maximum principal stress in the range of this examination.
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Keita SAJI, Qiang YU, Tadahiro SHIBUTANI, Masaki SHIRATORI
Article type: Article
Session ID: 1112
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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This paper presents a design support methods to evaluate thermal fatigue life of solder balls on Ball Grid Array (BGA) package. Authors have investigated relations between the design factors and the reliability of soldered joints in BGA model by using clustering analysis. Based on relations between design factors and characteristic value, a function estimating inelastic strain range, which is the characteristic value for thermal fatigue life, was developed. The function can estimate the value to a set of design factors within 20% error.
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Takuya Sasaki, Nobuki Ueta, Hideo Miura
Article type: Article
Session ID: 1101
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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In flip-chip structures, the difference in material properties such as Young's modulus and the coefficient of thermal expansion among a metallic bump, underfill, a silicon chip and a substrate causes the local distribution of residual stress on the chip surface. This stress distribution may cause serious degradation of electronic devices. In this study, we have developed piezoresistive strain sensor chips that consist of single-crystalline silicon for the measurement of residual stress in 3-D stacked structures. The local distribution of residual stress in a two-chip stacked structure was measured by the sensor chips. As a result, the amplitude of the distribution of the residual stress in an upper chip was almost constant of about 200 MPa regardless of the bottom bump alignment. When the two chips were stacked by same bump alignment, the amplitude in the bottom chip decreased to about one third.
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Nobuki Ueta, Takuya Sasaki, Hideo Miura
Article type: Article
Session ID: 1102
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Effect of residual stress in a silicon chip stacked three-dimensionally for high performance applications on the electronic characteristics of transistors formed in the chip was analyzed by using a finite element method. A periodic distribution appeared in each stacked chip due to the periodic small bump alignment. Since the electronic band structure of silicon distorted by strain, it was found that the electronic performance of NMOS transistors changed by about 10%/100-MPa. Therefore, it is very important to optimize the structure design of each product.
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Yuki Sato, Hideo Miura
Article type: Article
Session ID: 1103
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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When the thickness of a Si chip is thinned to less than 100 μm, large local thermal deformation of the thinned Si chip appears easily due to the CTE mismatch between bump and underfill materials in an area-arrayed flip chip bonding structure. And the amplitude of this local deformation is strongly depending on the structural and material factors of flip chip bonding structures. The authors have measured the change of the local deformation of a Si chip assembled by area-arrayed flip chip technology. It was confirmed that the local deformation changes from 0.1 μm to 2.5 μm depending on the bump pitch and the mechanical properties of underfill material.
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Yasuhisa FUJIMOTO, Mitsuru SATO, Hiroo SAKAMOTO, Shinichi TAKAGI, Hiro ...
Article type: Article
Session ID: 1104
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Copper base have been used for many semiconductor package to satisfy thermal radiation performance. However, copper base easily curvature deformed and deformation increases during thermal cycle. In this research, the increase mechanism of copper base deformation during heat cycle is clarified using experimental approach and fmite element analyses. As a result, this phenomenon occurs as a interaction with plastic deformation of copper base at low temperature and a stress relaxation due to solder creep at high temperature. The results of fmite element analysis that considers plasticity of copper and creep deformation of solder joint agree well with experimental result under same thermal cyclic conditions.
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Masaki KAJITANI, Tashiyuki TORII, Kenichi SHIMIZU, Akira MATSUBA
Article type: Article
Session ID: 1105
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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This study was discussed on the influence of film width and thickness on the relationship between fatigue damage and electric resistance using copper film bonded with resin. As an experimental result, there was a tendency for the electric resistance to increase during fatigue on the film, where the increase was small for the smaller width of the film in accordance with the rare occurrence of fatigue cracks.
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Takao MIKAMI, Masaki FUJIKAWA, Takaya KOBAYASHI
Article type: Article
Session ID: 1113
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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In this paper, deflection of a multilayered viscoelastic plate subject to thermal load is analyzed using plate theory for estimation of deflection of printed circuit board. Curvature in multilayerd plate and membrane forces in each layer are obtained using the condition of strain at adhesive faces, balancing of membrane forces and bending moments at each layer. The results calculated by proposed technique are compared with the FEM solution, and a good agreement was obtained.
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Kazumitsu WATANABE, Masaru ISHIZUKA, Shinji NAKAGAWA
Article type: Article
Session ID: 1114
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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For the printed circuit boards for the power electronics, whether the simulation of the temperatures of parts was possible by the commercial CFD analysis was compared with the experiment and I examined it. Moreover, the influence of the heat sink thickness was examined. As a result, If you set the thermal conductivity of the boards and the heaters to an appropriate mean value by CFD analysis, an experiment value and an analytical value were able to be brought close. When the heat sink was not installed, it was about ± 5.0℃. On the other hand, when the heat sink was installed, it was about ± 7.0℃. In addition, it was predictable that the effect of the heat sink was not ruined even if the thickness of the heat sink was thinned.
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Yasuyuki Yokono, Katsumi HISANO, Kenji HIROHATA, Takashi KAWAKAMI
Article type: Article
Session ID: 1115
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The present trend of power device packages indicates that there is strong customer demand for utilization of several driving circuits and compact packaging with sufficiently high reliability. The mechanical reliability is highly dependent on mechanical packaging technology, which includes cooling techniques and material strength characteristics. The use of cooling systems for a power device package is not only to keep the device temperature below a critical value, but also to control the solder strain caused by thermal expansion. In the present study, the design of a power device package that had a robust thermal property against the manufacturing error was completed. The material selection and the component dimension of the package were determined by examining the solder strain as the result of the thermal expansion difference, the thermal resistance and the variance of these design objects.
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Katsuhiro KOIZUMI, Masaru ISHIZUKA, Shinji NAKAGAWA
Article type: Article
Session ID: 1116
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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In the design process of electronic equipment, the early estimation of component temperature is of great importance. In order to predict the lifetime of equipments, the electrolytic capacitor is one of the most important components in thermal analysis of electronic equipment. To predict the component and system temperature, the thermal flow simulation technique has been applying to thermal design in the development phase of electronic equipment. In this study, we investigate the compact thermal modeling method of electrolytic capacitors. This paper describes the result of experiment of the confirmation of the main thermal path of the electrolytic capacitor on the printed circuit board as the basic data for the investigation of modeling method. In addition, based on the result of the experiment, we considered the benchmark experiment procedure.
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Masao Fujii
Article type: Article
Session ID: 1117
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Two rectangular block-like elements as an electronic module are positioned in a parallel-walled channel and cooled by forced convection airflow. A metal plate with holes as a barrier protrudes above the plane of the modules, which is intended to function as a cover for protecting them from mechanical or electromagnetic damage. Per-module heat transfer coefficients were measured by varying the row numbers of holes of the barrier, and compared to those of the barrier without holes. The row number of the holes of the barrier influences the heat transfer performance to classify into enhancement and reduction zones.
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Shinji NAKAGAWA, Katsuhiro Koizumi, Tukasa TAKAMA, Masaru ISHIZUKA
Article type: Article
Session ID: 1118
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Flow soldering process with a simple model has been studied experimentally and numerically. Open-source software, OpenFOAM, is used to simulate flow of molten solder and air. Free surface of molten solder is captured with VOF method. It is confirmed that increasing lifting velocity increases the volume of a solder joint. An experimentally observed bridge between joints has not reproduced with present numerical simulation.
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Yasushi NISHINO, Ryoji IMAI, Masaru ISHIZUKA, Shinji NAKAGAWA
Article type: Article
Session ID: 1119
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The natural cooling capability and flow field in relatively small electronic equipment were studied. A vertical channel model was used as an experimental model of electronic equipment. The channel model has two vertical copper walls modeling the printed circuit boards and two transparent walls modeling the casing walls. The clearance between the copper walls is varied from 5 mm to 15 mm. The natural cooling capability was obtained as functions of the wall clearance. The velocity profiles in the channel were quantitatively measured using a particle image velocimetry (PIV). When the channel clearance was 5 mm, the cooling capability of the natural convection was dropped and the velocity in the channel model was reduced.
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Tomoki NISHIDE, Yuichi FUNAWATASHI
Article type: Article
Session ID: 1120
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Effects of an obstacle placed over a heat source at the bottom surface of an enclosure on natural convection have been studied numerically. Computations were conducted for various widths of an obstacle with an aspect ratio of the enclosure of 1 and for various aspect ratios with a constant value of width of an obstacle. The results show that flow patterns can be roughly divided into three types: (1) fluid flows mainly over the obstacle, (2) fluid flows both over and through under the obstacle, and (3) flow is limited under the obstacle. When the flow is limited in the region over the obstacle, heat transfer is hindered. When the fluid flows through under the obstacle, however, heat transfer reduction is diminished.
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Takashi FUKUE, Takafumi YOSHIMOTO, Masaru ISHIZUKA, Shinji NAKAGAWA
Article type: Article
Session ID: 1121
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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This paper describes the effects of frame and inlet sizes of an electronic casing on the cooling fan performance. The performance of air-cooling fans is defined by their P-Q (Static pressure-Flow rate) characteristics. Recent studies report that P-Q characteristics of cooling fans depend considerably on their operational environments. In previous study, we evaluated P-Q characteristics including effects of frame by defining static pressure as pressure difference between chamber and air pressure. But usually, static pressure means pressure difference between backward and forward of fan. So in this study, we measured flow rate and pressure difference between the front and the rear and explored effects of frame, especially effects from area of inlet sizes. From experimental results, it was found that the fan P-Q characteristics were changed by frame, and flow rate were affected strongly by inlet sizes.
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Nobuyuki ISOSHIMA, Masatoshi WATANABE, Ken Tsukamoto, Mikio Shiraishi
Article type: Article
Session ID: 1122
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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A simple and high performance cooling structure for PDP-sets, "multi-flow structure" was developed using Computational Fluid Dynamics with heat transfer based on Cartesian grid system. In the conventional cooling structure, upward flow induced by natural convection and fans mainly contributes the cooling for PDP-panel and other PCBs. But simulation results indicated that bypass flow between bottom inlet and fans was formed along the back-cover and the bypass flow reduced the mean exit temperature. For the multi-flow structure, bottom and back inlets were reduced, and top and side inlets were added to induce the flow to high temperature regions. Simulation and experiment results showed that cooling performance of multi-flow structure was superior to the conventional structure. The multi-flow structure was applied to 60V-size PDP-sets.
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Takeshi IWAKI, Kenji KANEKO, Kazuki ENOMOTO
Article type: Article
Session ID: 1123
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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In this paper, mechanical ratcheting of 6-4 brass under steady axial stress and cyclic shear load is investigated experimentally. In the experiments, the strain rate is controlled to be 200 × 10^<-6>[1/s] and the number of cycles is 0〜100cycles. The amount of the increasing ratchet ratcheting strain is formulated precisely as the function of the steady stress, the cyclic strain amplitude and number of cycle for less than 100 number of cycles. The calculation method is suggested for estimating the amount of the ratchet strain that finally converges by normalizing the relationships between ratcheting strain and the direction of plastic strain increment vectors.
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Saya TAKEUCHI, Kenji KANEKO, Kazuki ENOMOTO
Article type: Article
Session ID: 1124
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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In this study, effects of viscosity and aging on plastic behavior of A7475 aluminum alloy under biaxial loading and in stress relaxation at several temperatures, are investigated experimentally, and are analyzed theoretically based on the Two-Factors constitutive concept, which means the overstress concept including aging effect. As much as temperature become higher, viscosity stress increases, on the other hand, aging stress decreases. Both viscosity and aging in axial loading are larger than those in torsional loading. The model based on Two-Factors constitutive concept gives systematic predictions on both plastic flow behavior and relaxation behavior for each loading direction.
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Jyuhachi ODA, Sinobu SAKAI, Ryota NOBE, Kouji YAMADA, Susumu MIYAKAWA
Article type: Article
Session ID: 1125
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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In this paper, the mechanical properties of sintered materials is estimated by using the finite element method. The FEM model of the sintered material based on frequency distribution of air hole size is decided. The models have similar characteristics to real sintered materials. Experimental Young's modulus is in coincide with the corresponding analytical value. From the results, that FEM models are available for evaluation.
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Kensuke NOZAKI, Hidetoshi KOBAYASHI, Keitaro HORIKAWA, Keiko WATANABE
Article type: Article
Session ID: 1126
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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The influence of strain rate on the compressive strength and the absorbed energy of polystyrene foam used for vehicles was experimentally studied by conducting compression tests at strain rates from 10^<-3> to 830 s^<-1>. In the tests, we used a special load cell which can measure the load applied to specimens for long time without any disturbance due to the reflected stress waves. It was found that the flow stress of polystyrene foam during deformation and the absorbed energy up to the strain of 0.6 increased with the increase of strain rates.
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Masaaki ITABASHI
Article type: Article
Session ID: 1127
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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An international standard for high velocity tensile testing method is now constructing in ISO/TC164/SC1/WG7. One of the recommended testing methods is the one bar method, as well as the split Hopkinson pressure bar method. In 2002, Yoshida reported that output bar supporting methods for the one bar method are relatively sensitive to the accuracy in the initial peak behavior on steel stress-strain curves. With his testing machine, he found that the inordinately high initial peak could be suppressed by supporting the loading-end of the output bar moderately. On the other hand, in 2002, the present author succeeded to suppress the tremendous peak by changing the design of a specimen assembly. In this paper, two methods are compared and combined. Two kinds of the combinations may be recommended to suppress the tremendous peak.
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Osamu MATSUMOTO, Atsushi HOTTA
Article type: Article
Session ID: 1128
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Crystallization kinetics, thermal and mechanical properties of polyester(PCC) based poly(tetramethylene glycol) copolymer(PCCP) and blends(PCC/PTMG) were investigated by using differential scanning calorimetry(DSC), polarized optical microscopy(POM) and tensile tester. This study focused on the effect of soft segment on thermal and mechanical properties. The PCC showed significant cold crystallization at 115℃ and spherulite structure. Whereas no cold-crystallization peak appeared in the all PCCPs except PCCP5wt%. Moreover, tensile modulus and strength slightly decreased dependent on PTMG content. This can be explained by the existence of the interaction between PCC and PTMG molecular chains, which blocks the movement of the chain segments of PCC at this temperature. Compared to the PCC/PTMGs, PCCPs were largely affected by PTMG on thermal property, especially melting energy. In contrast, both tensile modulus values showed similar behaviors, indicating that the content of PTMG affects on rigidity regardless of molecular structure.
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Satomitsu IMAI, Kei SAITO, Keisuke Tsuchiya
Article type: Article
Session ID: 1214
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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About micro-tweezers consisting of two beams as a handling part, we examined handling characteristics by finite element analysis. Purpose is to clarify what shape of the handling part is good for handling stability. Examined factors are handling force, friction coefficient, and contact condition. The handling characteristics do not change on the handling force and the fiction coefficient so much substantially. It seems that the reason is small contact area. Therefore, it is important to make the contact area large by preventing the contact surface of the micro-tweezers from inclining in handling operation. It is one method to optimize length of the handling beam and handling force.
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Masahiro MIZUNO, Noboru EGAMI, Hirohisa KIMACHI, Tatsuhiro YASUDA
Article type: Article
Session ID: 1215
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Friction stir spot welding (FSSW) method is the solid state bonding at extremely low temperatures by friction heat. Therefore bonding strength by FSSW show superior tensile strength compared to the conventional melting welding, FSSW has been widely recognized at efficient and useful welding method. In this study was two copper thin plate was welded by the friction stir micro spot welding with sub-millimeter spot size. Then, the welding properties for various welding conditions, tool rotating speed and the pressing displacement, were evaluated the applicability of this new FSSW method to electronic devices.
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Yuka KOJIMA, Hidehiko KIMURA, Yoshiaki AKINIWA, Yang JU
Article type: Article
Session ID: 1216
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Ultrafine-grained Cu processed by ECAP (Equal Channel Angular Pressing) with the grain size of d = 300 nm was fatigued at low stress intensity factor to investigate the grain coarsening mechanism during fatigue. EBSD (Electron Backscatter Diffraction) and AFM (Atomic Force Microscopy) methods were employed for the nanometer-scale analysis. The results show that fatigue damage area around the crack is observed in coarsened grains. Slip damages with the primary and secondary slip system were activated during fatigue. The detailed observation before and after fatigue at the same region revealed that the grain boundary of the coarsened grain moves as a high angle boundary. The initial residual strain in ECAP-processed Cu is considered to be one of the driving factors of the high angle boundary.
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Katsuei IMAI, Yu UJITA, Takashi MATSUMURA, Yasuo OCHI
Article type: Article
Session ID: 1217
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Nanoindentation is used for evaluating the mechanical properties of micro material. However, it is not examined whether nanoindentation can apply to thin sheet. Therefore, the establishment of the test method for the thin sheet is necessary. In this study, SUS304 thin sheets with thicknesses of 100, 50, 20 and 10μm were used. Specimens were glued to metal block with using 2 kind of adhesive, Young's modulus and indentation hardness were measured. As the results, Young's modulus was almost constant in the low indentation load region, but that was decreased when indentation load is increased than a certain value. Indentation hardness was almost constant despite surface polishing or adhesive. But, in the case of thicknesses of 20 and 10μm, the effect of the thickness appeared in the hardness when indentation load is very large.
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Takanobu MATSUMOTO, Atsushi SEKIKAWA, Futoshi NISHIMURA, Ikuo IHARA
Article type: Article
Session ID: 1218
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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There are growing demands for determining the stress-strain relationship at a local area of materials since such knowledge on mechanical properties are indispensable for making a precise CAE analysis of MEMS as well as industrial materials systems. In this work, a load-controlled nanoindentation technique with a spherical tip has been applied to the determinations of stress-strain curves and the Yield stress for a low carbon steel surface. A multiple continuous indentation method is used for measuring load-penetration depth curves. It has been found that the estimated stress-strain curves and the Yield stress are almost agree with those measured by tensile tests when the influence of the residual stress of the specimen surface is taken into account.
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Hirohisa KIMACHI, Shinji YAMAMOTO, Wataru OTA, Kaori SHIRAKIHARA, Yuic ...
Article type: Article
Session ID: 1219
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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It is very important to grasp stress and strain states in sub-micro scale area. In this study, stress and strain components in the single crystal sapphire and polycrystalline alumina were determined by the Raman microspectroscopy. First, the relationships of A_<1g> and E_g modes between the change of Raman shift and strain components were theoretically derived and 20 unknown parameters were experimentally determined. Second, stress measurements around the notch root in the single crystal sapphire was conducted. Then, components of strain were determined by Raman microspectroscopy and stresses were calculated by using Hook's law. The measured stresses were good agreement with FEM results. Last, mapping measurement of residual stresses and local stresses in polycrystalline alumina were conducted. The applicability of Raman micro-spectroscopy to stress/strain measurements in sub-micro scale area was confirmed.
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Yuta KAGOHASHI, Kenji KANEKO, Kazuki ENOMOTO
Article type: Article
Session ID: 1220
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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This paper deals with thermal conductivity of biomass plastic-boron nitride (BN) composite and BN-carbon fiber (CF) composite. The thermal conductivity of composites was measured by using laser flash method. The thermal conductivity of BN composite increased with increasing BN content. However the degree of orientation decreased with increasing BN content up 60 wt.%, and the increasing rate of thermal conductivity decreased at the case of 60wt.%. Kanari's equation was found to give good predictions of the thermal conductivity of BN composite for less than 50 wt.%. The thermal conductivity of BN-CF combined composite was higher than that of the BN or CF single composite.
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Kazuaki SANADA, Yuuki TADA, Yasuhide SHINDO
Article type: Article
Session ID: 1221
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Thermal conductivity of polymer composites with micro and nano fillers has been investigated numerically and experimentally. A periodic unit cell with a random close-packed structure was created using a packing algorithm that treat the micro filler as spheres. Finite element analyses were also performed to predict the potential of nano fillers to enhance thermal conductivity and to analyze the effect of microstructure of micro fillers. Results obtained from the proposed thermal models are compared with experimental results.
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Satoshi TOMITA, Hironori YAMASHITA, Shigetoshi ARAKI, Hiroyuki ONO
Article type: Article
Session ID: 1222
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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Micromechanical analysis is performed on the macroscopic thermal conductivity of a composite material with various misoriented elliptic reinforcements by using the equivalent inclusion method. The disturbance of heat flux occured in the material due to the reinforcement is estimated in its local-coodinate along the semi-axies of reinfocemant. By transforming the disturbance of heart flux into the global coodinate along the applied heat flux and by adopting the Mori-Tanaka theorem to the model, the volumetric average of the disturbance of heat flux can be estimated successfully. As a result, the macroscopic thermal conductivity of the composite can be expressed as a fuction of the direction cosine matrix of the orientaion of reinforcement.
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Toshihiro CHIBA, Yoshinobu SHIMAMURA, Keiichiro TOHGO, Hiroyasu ARAKI
Article type: Article
Session ID: 1223
Published: August 02, 2008
Released on J-STAGE: August 01, 2017
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