Strength, Fracture and Complexity - Volume 7, issue 1

Authors: Kishi, Emeritus Teruo

Article Type: Other

DOI: 10.3233/SFC-2011-0117

Citation: Strength, Fracture and Complexity, vol. 7, no. 1, pp. vii-vii, 2011

Authors: Yokobori, Takeo

Article Type: Research Article

Abstract: To conduct the research of fracture, since it is interdisciplinary research field, its application to various phenomena of fracture is possible. Until now, the terminologies of “Interdisciplinary approach to fracture and strength of solid”, “Fractology” and “Combined micro and macro fracture mechanics” have been proposed, however, in this paper, the terminology of “Holistic” was proposed as the most suitable one to reflect the philosophy of this research field.

Keywords: Interdisciplinary approach to fracture, strength of solid, fractology, combined micro and macro fracture mechanics, holistic

DOI: 10.3233/SFC-2011-0118

Citation: Strength, Fracture and Complexity, vol. 7, no. 1, pp. 1-4, 2011

Authors: Kishi, Teruo | Takemura, Masahiro | Kadohira, Takuya

Article Type: Research Article

DOI: 10.3233/SFC-2011-0119

Citation: Strength, Fracture and Complexity, vol. 7, no. 1, pp. 5-12, 2011

Authors: Carpinteri, A. | Lacidogna, G. | Manuello, A. | Borla, O.

Article Type: Research Article

Abstract: Neutron emission measurements, by means of 3 He devices and neutron bubble detectors, were performed during three different kinds of compression tests on brittle rocks: (i) under displacement control, (ii) under cyclic loading and (iii) by ultrasonic vibration. The material used for the tests was Green Luserna Granite. Since the analyzed material contains iron, our conjecture is that piezonuclear fission reactions involving fission of iron into aluminum, or into magnesium and silicon, should have occurred during compression damage and failure. This hypothesis is confirmed by Energy Dispersive X-ray Spectroscopy (EDS) tests conducted on Luserna Granite specimens. It is also interesting …to emphasize that the present natural abundances of aluminum (≈8%), and silicon (28%) and scarcity of iron (≈4%) in the continental Earth's crust should be possibly due to the piezonuclear fission reactions considered above. Show more

Keywords: Neutron emission, piezonuclear reactions, rocks crushing failure, energy dispersive X-ray spectroscopy, plate tectonics, element evolution

DOI: 10.3233/SFC-2011-0120

Citation: Strength, Fracture and Complexity, vol. 7, no. 1, pp. 13-31, 2011

Authors: Yu, Shouwen | Yu, Li | Zhang, Liping

Article Type: Research Article

Abstract: Ferroelectric materials is one of important smart materials using as actuators and sensors. Electric fatigue and damage of radiation may induce pinched polarization hysteresis loops and asymmetric strain hysteresis loops of ferroelectric materials, respectively. The damage level can be reflected by the evolution of hysteresis loops. This paper formulates a novel constitutive model to characterize the hysteresis deformation behavior of ferroelectric ceramics by electric fatigue. The results show that the alignment of the defect dipoles acts as an internal bias field and increases the coercive field, while the domain-wall pinning can prohibit domain switching and causes degradation of remanent polarization. …Then the damage criterion of the ferroelectric materials due to electric fatigue is proposed. The temperature in the ferroelectric and ferromagnetic materials may rise due to energy dissipation under loading. Thermal effects on the mechanical behavior in ferroelectric/ferromagnetic materials are investigated. Using the magnetic saturation model, the temperature fields around the tip of a narrow elliptic hole are calculated under different conditions. It is found that the magnitude of temperature increment strongly depends upon the geometrical shape of the hole, the frequency and wave shape of the magnetic loading. Show more

Keywords: Cyclic-electric loading, thermal effect, domain switching, ferroelectric materials

DOI: 10.3233/SFC-2011-0121

Citation: Strength, Fracture and Complexity, vol. 7, no. 1, pp. 33-41, 2011

Authors: Kubo, Shiro | Sakagami, Takahide | Ioka, Seiji | Maeda, Takaharu

Article Type: Research Article

Abstract: The present authors proposed the passive electric potential CT method using an electric potential distribution appearing due to the direct piezoelectric effect on a piezoelectric film pasted on a structure subjected to mechanical load. By applying an electric pulse on the film for emitting pulse-echo due to the inverse piezoelectric effect, the active pulse-echo method was proposed. In this paper a simultaneous application of the passive and the active methods using the piezoelectric film with multi-electrodes was made for the quantitative identification of through-cracks. The electric potential was measured on the film of a cracked specimen subjected to a varying …load. The electric pulse was applied to an electrode on the piezoelectric film and reflection waves were received at several electrodes on the piezoelectric film. Inverse analysis was made to identify the cracks from the observed electric potential distributions and the reflected waves. It was found that the active/passive method was useful for the estimation of the crack depth, for which the passive method was not efficient. The effectiveness of the active/passive method was shown. Show more

Keywords: Inverse problems, nondestructive testing, electric potential method, passive method, active method

DOI: 10.3233/SFC-2011-0122

Citation: Strength, Fracture and Complexity, vol. 7, no. 1, pp. 43-51, 2011

Authors: Enoki, Manabu

Article Type: Research Article

Abstract: Acoustic emission (AE) is a powerful tool to monitor the damage and impact in materials and structures. Process control is also one of the applications of AE measurement. However, it was very difficult to detect and analyze AE signals during material processing because of severe environment. Recently new technique to record AE signals such as laser AE and continuous waveform recording have been developed to apply to material processing. Ceramic thermal barrier coatings (TBCs) by atmospheric plasma spraying (APS) process have been widely used to add good heat resistance to metal base materials. Shot peening is also one of the …surface treatment methods to improve the materials properties such as fatigue strength by shooting of balls on the surface of products in order to generate a compressive stress. However, there are a few researches on quantitative evaluation between shot conditions and mechanical properties of products, and the optimal process conditions are determined through a try and error process. AE signals were successfully detected and analyzed in surface treatment such atmospheric plasma spraying, high velocity oxy-fuel coating process and shot peening. Condition monitoring of material processing using AE will be promising to improve the reliability of materials and structures. Show more

Keywords: Acoustic emission, inverse analysis, process monitoring, surface treatment

DOI: 10.3233/SFC-2011-0123

Citation: Strength, Fracture and Complexity, vol. 7, no. 1, pp. 53-60, 2011

Authors: Ri, S. | Sugano, T. | Saka, M. | Yamashita, M. | Togoh, F.

Article Type: Research Article

Abstract: In modern industrial electronic devices, aluminum (Al) thin films experience repetitive ON/OFF currents and sharp temperature fluctuations during use, which is equivalent to thermal cycling caused by Joule heating. In this research, the thermal fatigues of high-purity Al thin films with a polycrystalline structure that were exposed to high-cycle thermal testing were studied. Two types of thermal cycle testing were performed in which the total holding times at the high temperature were the same. One was high-cycle testing, i.e., a 12-second thermal cycle moving from 70 to 220°C and repeated for 10,000 cycles. The other was ultra-low-cycle or creep testing, …i.e., holding the sample at 220°C for 20,000 s. The experimental results show that thermal fatigue is quite different than creep damage. The number of hillocks and voids formed by high-cycle testing was much larger than that formed by ultra-low-cycle testing, and the deterioration of the surface appears suddenly. Thermal cycling accelerated damage growth in Al thin films. The process of surface deterioration in our experiments can be divided into three stages: (I) incubation stage, (II) development stage and (III) equilibrium stage. Within 10,000 thermal testing cycles, the dominant deformation mechanism changed from dislocation glide to grain-boundary sliding and atomic diffusion. Show more

Keywords: Al thin films, hillock formation, atomic diffusion, thermal fatigue, dislocation motion, grain-boundary sliding

DOI: 10.3233/SFC-2011-0124

Citation: Strength, Fracture and Complexity, vol. 7, no. 1, pp. 61-70, 2011

Authors: Shiwa, Mitsuharu | Masuda, Hiroyuki | Yamawaki, Hisasi | Ito, Kaita | Enoki, Manabu

Article Type: Research Article

Abstract: A new method of acoustic emission (AE) monitoring was proposed to study the corrosion and stress corrosion cracking (SCC) by chloride ion. It is a combination of the small chloride droplet corrosion, SCC testing method and AE waveform measurement system with a high sensitivity AE sensor, all of which have been developed by our group. Three types of corrosion were observed in the corrosion testing, which were the open pitting, the covered pitting and snake-like corrosion, respectively. There were many AE events in the covered pitting and snake-like corrosion. On the contrary, there was no AE event in the open …pitting. Meanwhile, the cross section of the snake-like corrosion was analyzed by EBSD. It shows that under the corrosion surface, there were some cracks at the {111} interface of Σ3 coincidence boundary and annealing twins. Based on these experiment results, it indicated that the microstructure generated by the covered pitting and snake-like corrosion during corrosion is the initiation site of stress corrosion cracking. Besides, the micro cell corrosion and SCC testing in thin plate specimens of SUS304 stainless steel by the AE monitoring were effective for evaluation of the progression process of them. Show more

Keywords: Corrosion testing, droplet, acoustic emission

DOI: 10.3233/SFC-2011-0125

Citation: Strength, Fracture and Complexity, vol. 7, no. 1, pp. 71-78, 2011

Authors: Takakuwa, Osamu | Ohmi, Toshihito | Nishikawa, Masaaki | Yokobori Jr., A. Toshimitsu | Soyama, Hitoshi

Article Type: Research Article

Abstract: In the use of hydrogen energy, the hydrogen embrittlement should be investigated, and it is necessary to improve reliability and safety of machine components which are used in hydrogen environment. The hydrogen sensitivity of material depends on material structure, defect and stress distribution. There is a possibility that the hydrogen invasion into material and the fatigue crack propagation with hydrogen embrittlement can be suppressed by introducing compressive residual stress by using surface modification such as cavitation peening. The cavitation peening is a one of the peening technique, and enhancement of the fatigue strength of the mechanical components and structural materials …by cavitation peening have been revealed. In this study, the austenite stainless steel JIS SUS316L with precrack were charged by a cathodic hydrogen charging method, and the fatigue test with and without hydrogen charge were conducted by a plate bending fatigue test. The results demonstrated that the fatigue crack propagation with hydrogen embrittlement can be greatly suppressed by cavitation peening. Show more

Keywords: Hydrogen embrittlement, crack propagation, cavitation peening, stainless steel

DOI: 10.3233/SFC-2011-0126

Citation: Strength, Fracture and Complexity, vol. 7, no. 1, pp. 79-85, 2011

Authors: Takasawa, Koichi | Wada, Yoru | Ishigaki, Ryoji | Kayano, Rinzo

Article Type: Research Article

Abstract: The effect of grain size on the susceptibility of high-strength low alloy steels to hydrogen environment embrittlement in a 45 MPa gaseous hydrogen atmosphere was examined in term of the hydrogen content penetrating the specimen during the deformation. Notch tensile tests were performed in a 45 MPa hydrogen environment using specimens with different prior austenite grain size numbers varying from 2.5 to 5.4. The hydrogen content was measured by thermal desorption analysis with a quadrupole mass spectrometer before and after the tensile test. The fracture stress of the notch tensile test increased with decreasing grain size; this showed that grain …refinement was effective in reducing the susceptibility of the specimens to hydrogen environment embrittlement in a high-pressure hydrogen atmosphere. The addition of nickel did not affect the fracture stress. A remarkable increase in the content of diffusive hydrogen was observed after the notch tensile test. Assuming that part of the diffusive hydrogen desorbed from grain boundaries, it can be inferred that grain refinement can reduce the mass of hydrogen in the unit grain boundary area, and the susceptibility to high-pressure hydrogen environment embrittlement. Show more

Keywords: High-pressure hydrogen gas, hydrogen environment embrittlement, high-strength low alloy steel, prior austenite grain size, grain size number, notch tensile test, thermal desorption analysis, dislocation, hydrogen content, vacancy, nickel content

DOI: 10.3233/SFC-2011-0127

Citation: Strength, Fracture and Complexity, vol. 7, no. 1, pp. 87-98, 2011

Authors: Ueno, Hiromi | Tanaka, Keisuke | Kimachi, Hirohisa

Article Type: Research Article

Abstract: Tin thin films with various thicknesses were electrodeposited on Cu substrate with and without Ni undercoat. The changes of the internal stresses in tin films were measured by the X-ray diffractions. For the case of 2.2 μm thick film without Ni undercoat, the initial internal stress was tension and then gradually changed into compression. After 20 h, the internal compressive stress became around −30 MPa and was remained constant afterward. Filament-type whiskers were formed on the surface after the stress changed into compression. For the case of 2.2 μm thick film with Ni undercoat, the stress maintained in tension and …no whisker was observed. For the cases of thicker films with and without Ni undercoat, the stress was compression around −30 MPa just after deposition, and remained constant. Nodule-type and Mount-type whiskers were formed on the surface, but no Filament-type whiskers were observed. The compressive stress applied by bending on 2.2 μm thick film with Ni undercoat resulted in the formation of Mount-type whiskers. The postbake process induced the tensile stresses in 2.2 and 16.5 μm thick films. Whisker formation was prevented in thin film and only Mount-type whiskers were formed in thicker films. Show more

Keywords: Tin whisker, internal stress, electrodeposited tin film, X-ray stress measurement, Ni undercoat, postbake

DOI: 10.3233/SFC-2011-0128

Citation: Strength, Fracture and Complexity, vol. 7, no. 1, pp. 99-108, 2011