Corrosion/Corrosion Fatigue and Life-Cycle Management
Robert P. WEI
Review Paper (Vol.7 No.3)
Corrosion/Corrosion Fatigue and Life-Cycle Management |
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Robert P. WEI |
147 |
General Papers (Vol.7 No.3)
Higher Order Asymptotic Solution for an Interfacial Crack in Piezoelectric Bimaterial under Impact |
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Toshihisa NISHIOKA and Shengping SHEN |
157 |
Effect of Upset Burr on Torsional Fatigue Strength of Friction Welded Carbon Steel Joints |
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Yoshiaki YAMAMOTO, Takashi KISHIMOTO, Hiizu OCHI, Koichi OGAWA, Hiroshi YAMAGUCHI and Ryoji TSUJINO |
166 |
Effect of Isothermal Physical Aging on Creep Behavior of Stainless-Fiber/PPE Composites |
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Kishore Kanti BISWAS and Satoshi SOMIYA |
172 |
Influence of Stacking Sequence on the Damage Growth in Quasi-isotropic CFRP Laminates |
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Jianqiao CHEN, Shigeo TAKEZONO, Masamichi NAGATA, Zhenlin CHEN and Takeshi FUJITA |
178 |
Flexural Load-Carrying Capacity and Failure Mechanism of RC Beams with Low Effective Depth under Running Wheel-Load |
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Tadashi ABE, Tetsukazu KIDA, Toshiaki SAWANO, Masaaki HOSHINO and Kiyoshi KATO |
186 |
Evaluation of Cu-AlN Joint Brazed with In-Based Active Brazing Filler Metals -Brazing Temperature and Heat Resistance- |
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Hideki SASAOKA and Toshikatsu MIKI |
194 |
Observation of the Swelling Behavior of Coniferous Cells Using a Confocal Scanning Laser Microscope and a Digital Image Correlation Method |
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Koji MURATA and Minoru MASUDA |
200 |
Electromagnetic Shielding Capacity of Wood Char Loaded with Nickel |
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Tsutomu SUZUKI, Tetsuo YAMADA, Noriyasu OKAZAKI, Akio TADA, Mikio NAKANISHI, Masami FUTAMATA and Hsin-Tai CHEN |
206 |
Detection of Plastic Deformation and Fatigue Damage in Pressure Vessel Steel by Leakage Magnetic Flux Sensors |
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Masatoshi KURODA, Shinsuke YAMANAKA, Koji YAMADA and Yoshihiro ISOBE |
213 |
Vol.7 No.3 ABSTRACT
Corrosion/Corrosion Fatigue and Life-Cycle Management
Robert P. WEI
Abstract:Corrosion and corrosion fatigue are well recognized as principal causes for the aging of engineered systems and the attendant reduction in their reliability and safety. To meet the challenges of designing for a modern, competitive global market and for the life-cycle management of aging systems, it is essential to develop science-based methods for predicting the evolution of damage through corrosion and corrosion fatigue, and other time-dependent mechanisms, and incorporating them into a new paradigm for design. To this end, the use of a mechanistically based probability (versus statistically based parametric) approach is presented, and illustrated through considerations of corrosion and corrosion fatigue in airframe aluminum alloys. Its efficacy in predicting damage evolution and distribu-tion is demonstrated through a comparison with long-term service data from an aircraft that had been in commercial service for 24 years. Key Words:Corrosion, Corrosion fatigue, Life-cycle management, Mechanistic models, Probability models, Aluminum alloys
Higher Order Asymptotic Solution for an Interfacial Crack in Piezoelectric Bimaterial under Impact
Toshihisa NISHIOKA and Shengping SHEN
Abstract:This paper investigates the asymptotic transient structure of the near-tip field in an anisotropic piezoelectric bimaterial system under impact loading. By using an asymptotic methodology, the governing equation is reduced to a series of coupled partial differential equations. Using the extended version of Stroh's formulation and the method of analytical continuation, the problem is further recast into a Riemann-Hilbert problem of vector form. Upon solving the Riemann-Hilbert equation, the higher order near-tip transient asymptotic fields are obtained. For a bimaterial of PZT and PZT-4 piezoelectric ceramics, the direct and converse piezoelectric effects on the stress intensity factors and electric displacement intensity factors are clarified. Key Words:Piezoelectric Material, Interface Crack, Asymptotic Analysis, Dynamic Fracture Mechanics
Effect of Upset Burr on Torsional Fatigue Strength of Friction Welded Carbon Steel Joints
Yoshiaki YAMAMOTO, Takashi KISHIMOTO, Hiizu OCHI, Koichi OGAWA, Hiroshi YAMAGUCHI and Ryoji TSUJINO
Abstract:Carbon steel was friction welded and torsion fatigue tests were conducted on weld joints having an upset burr in order to reveal the effect of an upset burr on fatigue strength. It was found that the fatigue strength of joints having a constant toe radius decreased with a decrease in hardness ratio (hardness of toe/hardness of base material). Softened joints (hardness ratio 1)and hardened joints (hardness ratio > 1)fractured at the toe of the upset burr and in the base material,respectively. On the other hand, the fatigue strength of joints having constant hardness ratio increased with toe radius.Using correlation analysis, a reasonable multiple regression equation was obtained between torsional fatigue strength and the fatigue factors, that is, the hardness ratio and toe radius of the upset burr.Thus, using this regression equation, torsional fatigue strength of friction welded joints having an upset burr could be estimated. Key Words:Friction Welding, Torsional Fatigue Strength, Carbon Steel Joint, Upset Burr, Toe radius, Hardness Ratio
Effect of Isothermal Physical Aging on Creep Behavior of Stainless-Fiber/PPE Composites
Kishore Kanti BISWAS and Satoshi SOMIYA
Abstract:In this research, the effect of isothermal physical aging on creep behavior of stainless-fiber/poly-phenylene ether (PPE) composites was investigated. Metal-fiber/PPE composites are non-crystalline thermoplastics and often used in engineering plastics, which have been developed for Electro-Magnetic-Interference (EMI) shielding. The results showed creep compliance curves to shift towards both the longer physical time and lower compliance sides with an increase in pre-aging treatment time, and it was established that creep deformation is arrested due to the progression of physical aging. Thus it was clarified that pre-aged composites can withstand higher temperature and longer time. The time-aging time superposition was established in creep of stainless-fiber/PPE composite. It was also observed that within the aging-time range, the shift rate is constant at all temperatures. The results showed that the shift rate is smaller at lower temperature and greater at higher temperature, and it reaches its maximum value at a wide range of temperature. Key Words:Metal-fiber/PPE composites, EMI shielding, Viscoelastic behavior, Creep compliance master curve, Physical aging, Shift rate
Influence of Stacking Sequence on the Damage Growth in Quasi-isotropic CFRP Laminates
Jianqiao CHEN, Shigeo TAKEZONO, Masamichi NAGATA, Zhenlin CHEN and Takeshi FUJITA
Abstract:Tensile tests are conducted for six types of quasi-isotropic carbon fiber reinforced plastics (CFRP) laminates, to investigate the influence of stacking sequence on the damage pattern and final failure. Stresses in the specimens are analyzed based on the FEM code - ANSYS, and the correlation between the numerical results and the practical observations is discussed. Both the non-damaged model and the cracked laminate model are analyzed. The FEM analysis results qualitatively agree well with the experimental observations. Key Words:CFRP laminate, Stacking sequence, Damage pattern, FEM analysis, Tensile strength
Tadashi ABE, Tetsukazu KIDA, Toshiaki SAWANO, Masaaki HOSHINO and Kiyoshi KATO
Abstract:Cracking damage occurs in the reinforced concrete (RC) slabs of highway bridges due to the passage of heavy vehicles. Tests were conducted to determine the ultimate flexural capacity and failure mechanism of two types of RC beam with different effective depths (Type A: d = 17.2 cm / Type B: d = 21.2 cm) modeled on RC slabs and subjected to running wheel-loads. The flexural load-carrying capacity for beams subjected to running wheel-loads decreased 16% for both Type A and Type B, as compared to beams subjected to static loads. The failure configuration for static loads and following running wheel-loads was a diagonal tension failure with a spread of approximately 50 - 55 deg. Starting from directly beneath the wheels. For running wheel-loads of a constant strength and running wheel-loads that included vibrations, the crack that occurred at the lower edge progressed to the compression bars due to increased load strength and repeated running and became flexural tension failure. In the case of running vibration-loads, it was learned that the frequency greatly affected the cracking interval and the reduction in bending rigidity. Key Words:RC beam, Running wheel-load, Running vibration-load, Flexural load-carrying capacity, Failure
Hideki SASAOKA and Toshikatsu MIKI
Abstract:The In-Ti active fillers were examined for joining metallic copper (Cu) to aluminum nitride (AlN) ceramics. Brazing was carried out with In-Ti active fillers with various compositions, and the microscopic structure and mechanical strength of the Cu-filler-AlN-filler-Cu joint at various temperatures were investigated. When brazed with an In-rich filler of In-1wt%Ti, most of In atoms in the filler were diffused into the Cu plate leaving a Ti-rich reaction layer of 2-4mm thick at the Cu-AlN joint interface. The 4-point bend strength at 500 increases linearly with the brazing temperature, whereas the strength at room temperature saturates at 40 Mpa. The specimen brazed at 820 has the strength of 58 Mpa and 33 Mpa at 500 and 600, respectively. On the other hand, when using Ti-rich fillers, e.g., In-7.7wt%Ti, In-15wt%Ti and In-23.8wt%Ti (same as Ti3In4 composition), granular Ti-rich phases was formed at the interface, and the microcracks were observed in the AlN. Key Words:AlN, Cu, Brazing, Active filler, Four-point bend strength, Ti-rich layer
Koji MURATA and Minoru MASUDA
Abstract:The transverse swelling behavior of coniferous wood cells was observed using a confocal scanning laser microscope and a digital image correlation method (DIC). Since the laser microscope has great depth of focus and high resolution, it was possible to observe the deformation of cells precisely. In order to observe the swelling behavior of specimens (Douglas-fir, Pseudotsuga menziessi) on the stage of the microscope, moisture was supplied using a humidifier. Digital image data of the cells taken by the laser microscope were used to measure the swelling behavior using DIC. The outside diameter of latewood tracheids swelled or changed almost isotropically with increasing moisture content, but the inside diameter (lumen) shrank greatly and nisotropically. Earlywood tracheids expanded a little but underwent great changes in shape. Thickness expansion of cell walls was less than circumferential expansion (perpendicular to the thickness direction), so that we concluded that the anisotropy of expansion was mainly based on thickness swelling. In latewood, circumferential expansion of radial cell walls (changes in length of the middle lamella) was great, but tangential cell walls expanded less than radial walls (in some cases the expansion was nearly zero). The angles between a radial wall and the adjacent tangential wall increased both in latewood and in earlywood by swelling. Key Words:Transverse swelling behavior, Coniferous wood, Confocal scanning laser microscope, Digital image correlation method
Electromagnetic Shielding Capacity of Wood Char Loaded with Nickel
Tsutomu SUZUKI, Tetsuo YAMADA, Noriyasu OKAZAKI, Akio TADA, Mikio NAKANISHI, Masami FUTAMATA and Hsin-Tai CHEN
Abstract:Nickel-loaded larch chars were prepared by various methods and then molded into disk specimens to measure their electromagnetic shielding (EMS) capacities in the range of 50-800 MHz. The capacity was dependent on carbonization temperature for char preparation, molding pressure, nickel loading, and the loading method. This is because the crystal structure of woody carbon and the density of a specimen were predominant factors in determining the EMS effect. The combination of carbonization at 900, molding at 5.9 Mpa, 4.5 wt% loading of nickel by wet impregnation before carbonization was adequate for affording char a highly efficacious EMS capacity. These results show the feasibility of an easy and inexpensive production of an EMS material from wood by carbonization. Key Words:Electromagnetic shielding capacity, Wood char, Carbonization, Nickel loading
Masatoshi KURODA, Shinsuke YAMANAKA, Koji YAMADA and Yoshihiro ISOBE
Abstract:In order to detect material degradations in pressure vessel steel of A533B employed as a component material in light water reactors (LWRs), the leakage magnetic flux distribution on plate-type A533B specimens has been examined using a magnetic sensor of 120mm square GaAs Hall element. As reference data, the residual stress distribution has also been obtained by X-ray diffraction method where an irradiation spot was 1mm in diameter. The data of the leakage magnetic flux normal to the specimen surface (Bz) measured by the Hall sensor were converted into the form of the first derivative dBz/dx by calculating the gradient of the Bz along the axial direction of the specimen (x-axis), and the data of the axial residual stress (Πx) obtained by the X-ray diffraction method were also transformed into the differential form dΠx/dx. It was found that there existed a correlation between the absolute value of the dBz/dx and the dΠx/dx for the tensile specimens (correlation coefficient r =0.282). Full width at half maximum (FWHM) for the frequency distribution profile of the dBz/dx was calculated. The FWHM of the tensile specimens increased remarkably at the beginning stage of the plastic deformation where the Luderfs band was generated; The FWHM of the fatigued specimens increased with stress cycling. It was suggested that the leakage magnetic flux measurement by the GaAs Hall sensor was a promising non-destructive evaluation (NDE) method to detect the amount of plastic deformation and fatigue damage. Key Words:Pressure vessel steel, Leakage magnetic flux, Magnetic sensor, X-ray diffraction, Residual stress, Plastic deformation, Fatigue damage, Non-destructive evaluation, Statistical processing