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Deformation behaviour of body centered cubic Fe nanowires under tensile and compressive loading  [PDF]
G. Sainath,B. K. Choudhary,T. Jayakumar
Physics , 2014,
Abstract: Molecular Dynamics (MD) simulations have been carried out to investigate the deformation behaviour of <110>/{111} body centered cubic (BCC) Fe nanowires under tensile and compressive loading. An embedded atom method (EAM) potential was used to describe the interatomic interactions. The simulations were carried out at 10 K with a constant strain rate of $1\times10^{8}$ $s^{-1}$. The results indicate a significant differences in deformation mechanisms under tensile and compressive loading. Under tensile loading, the deformation occurs by the slip of full dislocations, While under compressive loading twinning was observed as the dominant mode of deformation. The tension-compression asymmetry in deformation mechanisms of BCC Fe nanowires is attributed to twinning-antitwinning asymmetry of 1/6<111> partial dislocation on {112} planes. We further explain the mechanism of dislocation pile up in tensile loading and twin growth in compressive loading.
Effect of Pre-loading on Short Fatigue Crack Growth at a Notch
XU Kewei HE Jiawen ZHOU Huijiu Research Institute for Strength of Metals,Xi''an Jiaotong University,Xi''an,China To whom correspondence should be addressed,

材料科学技术学报 , 1992,
Abstract: Results indicate that under cyclic tension the growth rate of short fatigue crack from notch root will be lowered greatly by tensile pre-loading,but only a little change by compressive pre-loading. The effect of tensile pre-loading will decrease with the increase of stress ratio.The variation of short fatigue crack growth rate is related to the residual stress distribution around notch root.
Structure and Stability of BCC Crystals Fe, V, Nb and Ta under Hydrostatic Loading  [cached]
Jingzhou Wang,Yongjie Dai
Applied Physics Research , 2012, DOI: 10.5539/apr.v4n3p8
Abstract: The structural stability and theoretical strength of BCC crystals Fe, V, Nb and Ta under hydrostatic loading have been investigated by using the modified analytical embedded atom method (MAEAM). For all the calculated BCC crystals, the failures occur while the relation m >0 is violated in compression and k >0 is violated in tension. It found that the stable regions are 0.9269~1.1495, 0.9270~1.1545, 0.9268~1.1449 and 0.9268 ~ 1.1427 in the lattice stretch l or the corresponding -408.89 ~ 123.54, -186.96 ~ 131.43, -259.07 ~ 152.53 and -283.92 ~137.04eV/nm3 in the theoretical strength for Fe, V, Nb and Ta, respectively. The calculated maximum tensile stresses smax of Fe, V, Nb and Ta are 123.57, 131.74, 154.45 and 137.85eV/nm3 and the corresponding lattice stretch lmax ??are 1.1527, 1.1617, 1.1661 and 1.1545. The calculated maximum tensile stress smax and the corresponding lattice stretch lmax ??of Fe are consistent well with the results of Ab initio calculation.
Compressive Strength and Crack Propagation of Cement Composites Reinforced Coconut Fibre
Alida Abdullah,Shamsul Baharin Jamaludin,Mazlee Mohd Noor,Kamarudin Hussin
Journal of Engineering and Applied Sciences , 2012, DOI: 10.3923/jeasci.2012.108.112
Abstract: This study presents the compressive strength and crack propagation of cement composites reinforced coconut fibre. The development of cement composites in this research were done by substituting coconut fibre to the portion of sand based on the ratio of cement to sand. Cement composites were mixed with 3, 6, 9, 12, 15 wt. % of coconut fibre and amount of water per cement ratio was fixed at 0.55. They were then cured in water for 7, 14 and 28 days of curing. The result obtained that the cement composite with 9 wt. % of coconut fibre gives highest compressive strength and the crack propagation is controlled by coconut fibre addition.
Finite Element Model of Crack Growth under Mixed Mode Loading
International Journal of Materials Engineering , 2012, DOI: 10.5923/j.ijme.20120205.02
Abstract: In this paper, in order to predict the crack growth trajectory and to evaluate the SIF under mixed modes (I & II), one proposes a new finite element program for crack growth using the source code written in FORTRAN. The finite element mesh is generated using an advancing front method, where the generation of the background mesh and the construction of singular elements are also added to this developed programme to facilitate the crack process and the fracture analysis. Displacement Extrapolation Technique (DET) was employed to evaluate the SIFs under mixed mode loading conditions. Therefore, the accuracy of both SIF`s values and the crack path predictions results are compared and validated with other relevant published research work. However, the assessment indicated that this developed finite element programme is reliable and robust to evaluate the SIFs and predicts the crack trajectories successfully based on the applied loading conditions.

CHEN Youqing,

岩石力学与工程学报 , 2008,
Abstract: Microcrack development patterns in Westerly granite specimens stressed immediately before their ultimate failure by uniaxial compressive loading are observed using the fluorescent method proposed by Nishiyama and Kusuda(1994). Applying this method,the microscopic crack growth patterns,such as cleavage cracks within feldspar grains and intracrystalline cracks in quartz grains,and the wide-area distributions of these cracks are simultaneously confirmed with accuracy and ease. As a result of the observations,the elongated contiguous cracks estimated to have a direct impact on the final failure of granite are identified;and these cracks are roughly classified into three types. It is inferred that these three types of cracks do not develop at the same time;and each type has a different mechanism of generation. The mechanism of crack development under uniaxial compression is suggested to occur as follows. Firstly,many microcracks running parallel to the loading direction are induced by loading. Next,long cracks are induced by the elongation and coalescence of these microcracks located near the sides of the specimen. Then,the sides move outward due to further loading,generating the fault plane. The cracks within the relatively less damaged remaining parts are linked and propagated;and finally,these cracks induce the failure of specimen.

FENG Zhongxin,ZHANG Jianzhong,YANG Jianjun,CHEN Xinzeng Xi'an Jiaotong University,Xi'an Ningbo College,Ningbo,

金属学报 , 1996,
Abstract: Studies of the fatigue crack initiation and propagation show that there is the loading frequency effect for the quenched and tempered or normalized 40Cr steel, but no the loading frequency effect for the solution treated ICr18Ni9Ti. The essential reason that causes the loading frequency effect is due to decrease in the plastic deformation propagation speed with the inereasing loading frequency. The decrease in plastic strain amplitude and the increase in residual compressive stress play a main role for the delaying fatigue crack initiation and the retarding crack propagation. The study of the loading frequency effect on the fatigue behaviour of the metals with the lower plastic deformation propagation speed possesses important engineering signification.
Chloride Penetration into Fiber Reinforced Concrete under Static and Cyclic Compressive Loading  [cached]
Antoni Antoni
Civil Engineering Dimension , 2008,
Abstract: The effect of loading on the chloride penetration into plain concrete (PC) and fiber reinforced concrete (FRC) was studied experimentally by using modified NT Build 492 – Non-steady state chloride migration test that include the application of loading on the specimen during the test. Three types of polypropylene fibers with different lengths and shapes were used. The concretes were tested for chloride penetration at different stress ratios under static and cyclic loading. The results of the static loading showed that there was a slight reduction in the chloride penetration under low level of compressive stress while an increase in the chloride penetration was found at higher stress level. There are significance difference in chloride penetration behavior of the plain concrete, long fiber FRC and short fiber FRC. Chloride penetration increased even more at cyclic loading conditions showing difference behavior of FRC and PC at difference number of cycle and load level.
G.Y. Sha
,F.C. Jiang D. Wang,D.K. Liu,and R.T.

金属学报(英文版) , 2002,
Abstract: An experimental-numerical method for measuring dynamic crack propagating velocities under stress wave loading is established in this paper. The experiments of the three-point bend specimen are done on the improved Hopkinson bar. Deflection of loading point, dynamic load and instantaneous crack length are measured, then crack propagating velocities are calculated. Experiments on 40Cr steel show that the results given by this method have a good agreement with that obtained by the resistance fracture gage method. Therefore this method is feasible for measuring crack propagating velocities under high loading rate and will have wide application.

LIN Li,HU Naisai,HE Jiawen,

材料研究学报 , 1990,
Abstract: Fatigue crack propagation in a compressive residual stress field can be char-acterized with the closure effect.The closure force under cyclic loading as well as crackgrowth rate may be determined by experiments.Results show that the minimun crackgrowth ra
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