Papers by Keyword: Fracture Surface

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Authors: Khalil Farhangdoost, S. Rahnama
Abstract: A comparison between crack growth rate (da/dN) vs. effective stress intensity range factor (ΔKeff) curve behavior and microscopic and macroscopic fracture surface of commercial Ti-6Al-4V alloy are presented. Three different regimes are correlated with characteristics measured on the fracture surfaces. Three regions can be observed in which part I is rough and darker than others parts known as pre-transition, part II is smooth and light known as transition region and part III is a little darker than part II known as post-transition region. In the present investigation the correlation of fatigue crack growth rate for Ti-6Al-4V and microstructure of fracture surface has been presented.
Authors: Qing Hua Yuan, Shun Yao Jin, Zhong Guo Huang, Xue Ping Ren, He Song, Jian Wei
Abstract: To understand the effects and mechanism of heat treatment to the high-pressure vessel performance, a series of different closed-shaped cavity heat treatment tests were conducted. Through tensile test, impact test, hardness test, OM and SEM test and so on, the heat treatment effects and micro mechanism of high-pressure vessel with different closed-shaped cavity were studied along the wall thickness direction. The results indicate that: with increase of volume of the closed-shaped cavity, the strength of container middle cross-section increases in the beginning and decreases afterward, the toughness falls first and then rises, and the plasticity changes little. The strength, plasticity and hardness increase gradually from inside to outside along the wall thickness direction. The hardness increases a little in the beginning, but then rises quickly when it comes close to the outer wall. After being quenched at 930°C and tempered at 580°C, the microstructure of the vessel material is mainly tempered sorbite. The structure grain boundary becomes more and more blur from inside to outside of the wall. Inner wall contains a small amount of residual austenite and tempered martensite. The fracture surface is toughness one.
Authors: Eskil Andreasson, Nasir Mehmood, Tan Mao, Sharon Kao-Walter
Abstract: Observations and analysis of samples from scanning electron microscopic (SEM) micrographs has been concerned in this work. The samples originate from fractured mechanical mode I tensile testing of a thin polymer film made of polypropylene used in the packaging industry. Three different shapes of the crack; elliptical, circular and flat, were used to investigate the decrease in load carrying capacity. The fracture surfaces looked similar in all studied cases. Brittle-like material fracture process was observed both by SEM micrographs and the experimental mechanical results. A finite element model was created in Abaqus as a complementary tool to increase the understanding of the mechanical behaviour of the material. The numerical material models were calibrated and the results from the simulations were comparable to the experimental results.
Authors: Akihiro Takiyama, Kazuaki Nakane, Katsuyuki Kida
Abstract: From early 20th, the homology have been studied as a branch of mathematics. It has been one of a major topic in mathematics and applied in many scientific fields. The homology can be regarded as a mathematical concept of quantifying the contact degree. Because it belongs to modern mathematics, advanced knowledge of mathematics are required to understand this concept. Fortunately, since the definition of the homology is very simple in two-dimensional case, we can easily apply this to image analyzing methods. Fracture surface is composed of a process that cracks grow. If these cracks contact one another, rupture occurs. Progress of the fracture would vary due to the effect of external force. We identify the rapid and the fatigue fracture surface by a homology method. By analyzing the state of fracture via a homology method, it is believed that the cause of fracture can be estimated.
Authors: Mária Mihaliková, Petra Lacková, Anna Lišková
Abstract: The effect of microstructure on the mechanical properties of cord steel wires was investigated. Material properties and damage behaviours were identified. Metal cord, for reinforcing articles of an elastomeric material, such as tires, conveyor belts and so on of the single strand type, in particular made up of a plurality of 3, 4 or 6 wires, where in the said wires are twisted together loosely. The metal cord characterized by the fact that the diameter of the individual constituent wires varies between 0.12 and 0.30 mm. Rm tested cord wire was max. 2 946 MPa. Fracture surfaces cords steels were observed.
Authors: Xing Jian Gao, Deng Fu Chen, Li Wei Song, Hui Hu, Xing Lei Yang, Guan Wang, Zhen Yu Zhou
Abstract: The embrittlement of particular weather resistant steel has been investigated by thermal tensile tests using a Gleeble-1500D system at temperatures range from 600 to 1300°C and at a strain rate of 10-3/s. The specimen was reheated and cooled to the test temperature before the tensile deformation in order to get the mechanical properties subject to the continuous casting process. To make clear the plastic flow behavior in Austenite and γ-Ferrite temperature range of the weather resistant steel, the tensile tests were performed and the results indicate that the stress-strain curves as a function of temperature and with the temperature increased the stress became less, while the hot ductility changed significantly due to the work hardening and recrystallization. All of the strength indices (including yield strength, tensile strength and fracture strength) of the steel increased gradually with decreasing temperature, except for small fluctuations during the γ→α transformation occurred. Special emphases were placed on the hot ductility to clarify the sensitivity of surface cracking during unbending operation and the embrittlement zone occurred in the temperature range between 750 and 1050°C, in which the minimum %R of A was around 22% at 850°C. In the embrittlement zone, the specimens were fractured with little plastic deformation by either grain boundary sliding or by localization of strain in the film proeutectoid ferrite produced by the γ→α transformation. Keywords: Weather Resistant Steel, Embrittlement Zone, Stress-Strain Analysis, Hot Ductility, Fracture Surface.
Authors: Jong Guk Yun, Xin Ming Cao, Yue Wang, Yan Kang, Xiao Wu Li
Abstract: Fatigue deformation behavior of the commercially pure iron containing micro-voids at grain boundaries (GBs) were investigated under total strain amplitude control, and fatigue fractures were quantitatively characterized by fractal analyses. The cyclic response curves of the CP iron show an initial softening stage within early several cycles followed by a continuous cyclic hardening. No stress saturation phenomenon was found. Pre-existence of micro-voids at GBs spurs intergranular cracking to become a common damage mode besides transgranular cracking along slip bands. Quantitative analyses of fracture surface demonstrate that the value of fractal dimension D of the scanning profile in the crack growth zone is the largest as compared to those in the crack source zone and final rapid fracture area, almost regardless of the applied strain amplitude. This phenomenon was discussed in terms of the tortuosity of crack propagation path.
Authors: Gyula Nagy, János Lukács
Abstract: The material quality, the deformation rate, the temperature and the stress state influence mechanical behaviour and properties of different materials. Due to this great variety of the influencing factors we do not have one model of general validity describing the behaviour of materials, but we have to use a great number of material constants in order to characterize the properties. The exponents of the Manson-Coffin, the Basquin and the Paris-Erdogan laws were applied for the verification of the connection among the fatigue fracture types. Own measured values and test results can be found in the literature were used for the illustration of the connections. “Fracture surface”-s were determined for characterizing of different steel grades and their welded joints. It can be concluded that “fracture surface”-s are suitable for the describing of the fracture behaviour and the conversion of different fracture parameters of steels.
Authors: Tatsuo Sakai, Koushu Hanaki, Akiyoshi Sakaida, Kenji Okada, Yuki Nakamura, Kazutaka Mukoyama, Noriyasu Oguma, Takashi Matsumura, Yoshinobu Shimamura, Akira Ueno
Abstract: As a joint project of Committees on Fatigue and Reliability Engineering in the Society of Materials Science, Japan (JSMS), an electronic database on fatigue strength of metallic materials fabricated in Japan had been constructed and published in 1996. Book style of the same data compilation had been published at the same time by the JSMS and Elsevier. About twenty years have passed since the above publications of database and databook. Thus, a lot of new fatigue test data have been obtained during such a long period including many data on the very high cycle fatigue such as gigacycle regime. Based on such a circumstance, the JSMS has organized a new project to construct an electronic database on very high cycle fatigue. A lot of numerical data obtained by fatigue tests would be compiled together with many photographs of fracture surfaces. In this paper, fundamental view and compilation concept of the database are briefly introduced by showing a typical example of proto-type database constructed from domestic data in Japan.
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