Papers by Keyword: Brittleness

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Authors: Tsuyoshi Kubota, Hiroshi Yamagata
Abstract: The present requirements for the connecting rod are indicated and the fracture splitting (FS) technologies for constructing the big end boss are reviewed. Two possibilities of FS for a high strength Cr-Mo steel and Ti alloys were discussed. The carburized quench-temper FS connecting rod has a superior fatigue strength with a high dimensional accuracy at the big end boss. The possibility of using a titanium FS connecting rod was examined and proposed.
4850
Authors: Harald Harmuth
Abstract: The denomination ‘flexible’ is chosen in the professional jargon of refractories technology for materials able to bear relatively high strains without or with acceptable loss of strength. In many cases this term is equivalent to relatively low brittleness. Characterisation of brittleness based on fracture mechanical investigations may use figures of merit like brittleness numbers, a so called characteristic length or the R’’’’ parameter according to Hasselman. In many cases these figures show that brittleness reduction of refractories is achieved by decrease of strength with at the same time more or less unaffected specific fracture energy. Microscopic investigations of fracture paths aim to exhibit which peculiarities of crack microstructure enable this change of mechanical properties. A microscopical technique developed for this purpose separately evaluates the relative crack lengths along the grain/matrix interface, within the matrix and within the grain. Results obtained for several types of refractories show brittleness decrease is associated by an increase of the relative crack length along the grain/matrix interface and a decrease of transgranular fracture. Prefabricated microcracks and a relatively low grain/matrix bond strength may support this type of crack propagation.
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Authors: Mani Shugani, Mahendra Aynyas, Sankar P. Sanyal
Abstract: We have performed First-principles density functional calculation by using full potential linearized augmented plane wave (FP-LAPW) method within generalized gradient approximation (GGA) of B2- AlGd (Aluminum compound). The ground state properties along with electronic and elastic properties are studied. The energy ranges are given for bands which are crossing the Fermi level and explained whether the Fermi surface is formed by hole pocket or electron pocket. Bonding properties are analyzed by charge density plot. By B/GH ratio the brittleness of the material is determined.
71
Authors: Maria A. Muñoz-Morris, Santiago Suriñach, Maria Dolores Baró, David G. Morris
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Authors: Jing Ping Wei, Fan Chen, Zhi Hao Ding
Abstract: Through the floor specific pressure test, the floor specific pressure was obtained. The rock mass of mudstone, under the loading perpendicular to the weak plane, was in brittle-plastic failure state, and the bearing capacity of mudstone was equal to the Ⅲa grade floor. The brittle-plastic transition mechanism of the mudstone was revealed: Firstly, the more size, the more heterogeneity. The mudstone body was bigger than its rock samples, so there were more planes of weakness, which caused the macroscopic plastic deformation. Secondly, the directions of the load and the weak plane influenced the strength of the mudstone floor. During the plastic deformation, the compressive failure occurred layer by layer under the loading perpendicular to the weak planes, and the post peak load-bearing capacity of mudstone floor was decided by the layer’s strength.
175
Authors: Nasir Shafiq, Muhd Fadhil Nuruddin, Ali Elheber Ahmed Elshekh, Ahmed Fathi Mohamed Salih
Abstract: In order to improve the mechanical properties of high strength concrete, HSC, several studies have been conducted using fly ash, FA. Researchers have made it possible to achieve 100-150MPa high strength concrete. Despite the popularity of this FAHSC, there is a major shortcoming in that it becomes more brittle, resulting in less than 0.1% tensile strain. The main objective of this work was to evaluate the fresh and hardened properties of FAHSC utilizing chopped basalt fiber stands, CBFS, as an internal strengthening addition material. This was achieved through a series of experimental works using a 20% replacement of cement by FA together with various contents of CBFS. Test results of concrete mixes in the fresh state showed no segregation, homogeneousness during the mixing period and workability ranging from 60 to 110 mm. Early and long terms of compressive strength did not show any improvement by using CBFS; in fact, it decreased. This was partially substituted by the effect of FA. Whereas, the split and flexural strengths of FASHC were significantly improved with increasing the content of CBFS as well as the percentage of the split and flexural tensile strength to the compressive strength. Also, test results showed a progressive increase in the areas under the stress-strain curves of the FAHSC strains after the CBFS addition. Therefore, the brittleness and toughness of the FAHSC were enhanced and the pattern of failure moved from brittle failure to ductile collapse using CBFS. It can be considered that the CBFS is a suitable strengthening material to produce ductile FAHSC.
381
Authors: Liang Huo, Xi Qiang Lin, Guo You Li, Tao Zhang
Abstract: It used conventional techniques and materials prepared high strength fiber reinforced concrete whose strength class is above C100 and it studied the effect of fiber content on the mechanical properties and elastic modulus. It also studied the fire resistance of fiber reinforced concrete. Results suggest that the strength of 28d concrete is above 100MPa and the highest strength is 126.4MPa. Under the same ratio conditions, the greater the volume content of steel fiber concrete flexural strength, the splitting tensile strength is higher. The steel fiber volume only affect elastic modulus of concrete little. When it heats to 300 °C, the no fiber concrete comminuted burst while the fiber concrete does not damaged at elevated temperatures up to 300 °C and continue to heat up, the crushing damage occurs at about 460 °C. Has not been damaged concrete specimens at 300 °C, the quality have emerged about 3% decline, while the compressive strength increased by 35%-52%, the highest strength reached 180.3MPa.
245
Authors: Bin Xu, Shu Hua Wang, Yu Peng Lu, Jianjun Cui, Mu Sen Li
Abstract: Application of powder boronizing to mechanical industry has been restricted because of the brittleness of boronized layer, which inevitably leads to decrease of service life of boronized parts. Therefore, attention should be paid to reducing the brittleness of boronized layer without decreasing its high hardness. In the present paper, a study on the effect of micro-addition rare earth and chrome on friction and wear behavior of boronized layer was carried out using an MM-200 wear test machine. Compared with that of pure single Fe2B phase, the brittleness of the boronized layer containing minim rare earth and chrome elements, obtained by powder RE-chrome-boronizing, is reduced, which results in increasing the bearing capacity and wear resistance of the boronized layer. The friction and wear mechanism is also briefly analyzed.
1401
Authors: Bin Xu, Le Yang, Shi Bo Xing, Li Li
Abstract: In order to increase boronizing speed without decreasing the hardness of boride layer, the effect of plastic deformation at room temperature on powder RE-chrome-boronizing for a medium carbon steel (steel 45), in which boronizing plays a main role, was studied in this paper. The cold plastic deformation (CPD), whether compressing or shot-peening, can increase boronizing speed. Meanwhile, the boride layer can also retain its high microhardness (1 300―1 900HV0.1) with low brittleness. The layer depth achieved for a given heating time increases with increasing CPD degree on the steel. The analyses show that boronizing kinetics in the RE-chrome-boronizing (RE-Cr-B) samples with CPD can be enhanced.
575
Authors: Ji Liang Wang, Kai Min Niu, Zhi Feng Yang, Ming Kai Zhou, Li Qun Sun, Guo Ju Ke
Abstract: Effects of fly ash and ground granulated blast-furnace slag (GGBFS) on workability, strength, volume stability and durability of HSC are investigated. Results show that fly ash and GGBFS can improve the workability, increase the later strength of high strength concrete (HSC) remarkably, and reduce the brittleness. In addition, the ameliorative effect of GGBFS on HSC brittleness is more remarkable. With the increase of fly ash and GGBFS, the early elastic modulus of HSC reduces. The elastic modulus is similar to the controlled sample when the load is applied after 60d curing. The fly ash and GGBFS can improve HSC’s resistance to chloride ion penetration significantly. However, the effects of fly ash and GGBFS on freezing-hawing resistance of HSC are not obvious. Besides, the fly ash will reduce freezing-hawing resistance of HSC only when the content of mineral powder is up to 36%.
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