Papers by Keyword: Ductile

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Authors: Mohammad M. Haque, Nur I. Syahriah, Ahmad Faris Ismail
Abstract: Aluminium-silicon alloys having different silicon contents (13, 20 and 27 percent) were used in the present study. The molten alloys were poured in to a mild steel die to cast tensile test bars. Then tensile and hardness tests were performed in order to analyze the properties and fracture surfaces of the cast specimens. Results show that as silicon content increases, the alloy becomes harder and less ductile. At the same time, the presence of alloying and impurity elements in the alloys forms complex compounds and intermetallic phases. They present deleterious effects on the strength of the alloys, causing a lowering of the energy required to fracture the test specimens with little permanent extension. However, heat treatment operations altered the structures and properties of the aluminium-silicon alloys. Heating to higher temperature, then quenching, ageing and tempering make the alloys stronger up to 13% silicon and beyond that limit the alloys become weaker, fracturing at lower load. The appearance of fracture surfaces after tensile testing showed these differences. This investigation also suggests that for the aluminium-silicon alloys containing 20% and 27% silicon do not require any expensive and time consuming thermal treatment operations, since properties do not improve with such treatments.
Authors: Shaiful Rizam Shamsudin, Mohd Harun, Mohd Noor Mazlee, Azmi Rahmat, Rohaya Abdul Malek
Abstract: A failure analysis of a broken multi strand wire rope from an offshore platform crane was performed. The wire rope was operated for less than 5 years. The wire consists of seven strands, one central strand and six strands around it. The diameter of the small wires was about 0.78-0.94 mm and the larger wires was a round of 1.52 - 1.78 mm. The large size wires were found fractured by cyclic torsional stresses as characterized by the presence of fatigue cracking originating from the outer surface of the wire. Meanwhile the smaller wires were fractured in a ductile manner under excessive load after the larger wire broken out due to the fatigue mechanism.
Authors: Shaiful Rizam Shamsudin, Mohd Harun, Mohd Arif Anuar Mohd Salleh, Hafizal Yazid, Mohd Noor Mazlee
Abstract: The wire material of filter mesh is made of 304 grade stainless steel. The failure to run properly was due to the impact of burst and torn. The client also expects that the failure was due to corrosion problems. A visual inspection on the strainer mesh was found covered by brownish rust layers and some scratches at the damaged area. The rusty wire mesh that was washed with pickling acid showed a clean and smooth surface. Energy dispersive spectroscopy (EDS) examination of the rusty wire mesh surface indicated that it was only normal oxide precipitates. Thus, it's proven that there were no signs of severe corrosion attack on the failed sample. SEM micrographs showed the unidirectional scratch effects exist in the damaged area. The fractography study was found there was a typical ductile structure on the fracture surface of the wire. It is proven that the wire mesh was actually still in good condition and has not experienced any embrittlement problems as if it exposed to any corrosive environment. The root cause of the failure is shown by the effect of scratches in which it is usually caused by a mechanical forceful push by a hard object or in other words, it is caused by human error factor.
Authors: Jun Wen Zhou, Dong Sheng Huang, Wen Hu Li, Ai Hua Liu, Wei Cheng Shi
Abstract: Bolted steel-wood-steel connection is an important fashion of connections in timber structure, the manners of failure loaded parallel-to-grain include bearing, row shear-out, group tear-out and splitting, and the brittle failure modes are predominant in some tested results of bolted connections specimens. End distance, bolt spacing, row spacing and the thickness of wood have important influence on the failure modes, and meanwhile, the bolt diameter can not be neglected. Based on the different failure fashion, the equations of strength were given.
Authors: Refat Ahmed Elshikhy
Abstract: New version of new proposed fracture theory called N-N was introduced as concepts and hypotheses. In this research analytical discussions and applications in addition to detailed explanation of physical meaning and conceptual formation of is introduced. The current theory depends mainly on energy approach in LEFM for isotropic brittle materials and can be applied for ductile materials and composites regarding their different properties. This theory represents an extension of the continued efforts to obtain a unified view for all ideas and proposals of the majority of the researchers in the field of development of the fracture theories to predict the mechanism and mechanical aspects of cracking process. Fundamental new concepts and analytical hypotheses are introduced.
Authors: C.A. Silva, R.C.R. Nascimento, M.S. Martins, M.C.S. Freitas
Abstract: The article to be presented will cover the whole process done in a fracture test for impact, taking into account the thermal treatment of the sample to be studied. The main objective of this article is to observe, verify, analyze and understand how the temperature difference of several samples influences the type and appearance of the fracture. The impact test have a great importance in industry, is through this that you can verify that the material is ideal for application in the production of equipment and vehicles that operate in high or low temperatures. The evaluation criteria of this trial are the energy absorbed by the sample, and the percentage of its characteristic lateral extension, and the percentage of fracture, ductile or fragile, and corresponding to a ductile fracture mode, in which the test at higher temperatures, the impact energy is relatively large, and fragile fracture mode, being one that as the temperature decreased, the impact energy will suffer decline. The most important result of the impact test is the measure of the energy absorbed by the test body to deform and break, measured by the variance of the gravitational potential energy of the hammer (machine component of the impact test) before and after impact. Therefore, providing the conclusion that the smaller the energy absorbed by the sample, more fragile it is depending on the temperature applied.
Authors: Gennady A. Salishchev, Sergey V. Zherebtsov, Svetlana Malysheva, A. Smyslov, E. Saphin, N. Izmaylova
Abstract: A comparative investigation of mechanical properties of Ti–6Al–4V titanium alloy with coarse-grained (400 m), microcrystalline (10 µm) and submicrocrystalline (0.4 µm) structures in the temperature range 20–500°C has been carried out. The submicrocrystalline structure was obtained by multiaxial isothermal forging. The alloys with the coarse-grained and microcrystalline structures were used in a heat-strengthened condition. The microstructure refinement increases both the strength and fatigue limit of the alloy at room temperature by about 20%. The strength of the submicrocrystalline alloy is higher than that of the microcrystalline alloy in the range 20 - 400°C. Long-term strength of the submicrocrystalline specimens below 300°C is also considerably higher than that of the other conditions. However, the creep strength of the submicrocrystalline alloy is slightly lower than that of the heat-strengthened microcrystalline alloy already at 250°C. The impact toughness in submicrocrystalline state is lower especially in the samples with introduced cracks. Additional surface modification of submicrocrystalline alloy by ion implantation gives a considerable increase in the fatigue limit. Advantages of practical application of submicrocrystalline titanium alloys produced by multiaxial isothermal forging have been evaluated.
Authors: Rong Bian, Eleonora Ferraris, Jun Qian, Dominiek Reynaerts, Liang Li, Ning He
Abstract: This work presents an experimental investigation on micro-milling of fully sintered Zirconia (ZrO2) with CVD diamond coated end mills. The experiments were conducted on a Kern MMP 2522 micro-milling centre. Diamond coated WC micro end mills with stiff geometry, are employed. Effects of cutting parameters on surface quality were investigated by means of a mixed full factorial experimental design. Surface roughness was measured by a Talysurf 120L profilometer. Surface topography was examined using a scanning electron microscope. The results show that a smaller feed rate was apt to result lower surface roughness. With the increase of cutting length, brittle damages were observed in some tests.
Authors: Xin Zhao, Xiao Ling Yang, Tian Fu Jing
Abstract: Specimens of medium carbon steel were quenched and warm-compressed on a Gleeble 3500 Machine. The microstructure of the specimens was studied by using an optical microscope and a transmission electron microscopy. And the properties were investigated by using tensile tests and hardness tests. Results show that the starting microstructure is lath martensite with a small amount of flake martensite. After 50% compression at 550-650°C, ultrafine grains can be observed in the specimens. The microstructure of the specimens compressed at 600°C is equiaxed ultrafine ferrite grains + nano-carbides and a good combination of strength and ductility is obtained. The tensile strength and total elongation are 861MPa and 19.1%, respectively. The hardness is 233.81Hv.
Authors: Y. Hasuda, Y. Suzuki, T. Kato, R. Meguriya, T. Furusawa, T. Ohashi
Abstract: High density and isotropic poreless structure of Glass-like-carbon makes it practically used for fuel cells of space-shuttles and hard disk substrate etc. Glass-like-carbon is one of the new materials which attract attention, but it is so hard and brittle that precise machining of this material is difficult. Surface grinding and slicing were performed to collect the fundamental data of precise machining. The main results obtained in this study are as follows. (1) The transition from brittle mode to ductile mode in surface grinding occurs at a grain mesh size between #5000 and #3000. (2) The maximum grain depth of cut ‘dg’ necessary for ductile mode grinding is 0.021-0.006 mm or less. (3) When it is being sliced, the kerf width of the #1000 grinding wheel becomes wider than that of the #2000 grinding wheel because of the fact that the material removal capability of the #1000 grinding wheel is bigger than that of the #2000 grinding wheel. (4) It is extremely effective to use the fine grinding wheel, since the Young's modulus of glass-like-carbon is considerably low and eventually causes compression transformation,.
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