John CodringtonAndrei KotousovStuart WildySook Ying Ho...
201-204页
查看更多>>摘要：A new theoretical approach is presented for investigating fatigue crack growth in plates of finite thickness. The developed approach utilizes a modified strip-yield analysis and the concept of plasticity-induced crack closure. A number of typical fatigue crack growth phenomena are investigated including the thickness effect on constant amplitude fatigue crack growth, retardation due to a tensile overload cycle, and short crack growth from sharp notches. Theoretical predictions are compared with experimental data and are found to be in very good correlation.
查看更多>>摘要：In order to investigate the effect of nitriding on the crack initiation and propagation behavior of Ni-base super alloy, Alloy 718, rotating bending fatigue tests were carried out until 10~8 cycles at room temperature. By nitriding at 500℃ for 12h, compound layer of about 5μm in thickness was formed and the initiation of a fatigue crack was strongly suppressed causing the increase in fatigue strength. A crack initiated in brittle manner at the compound layer in all of fractures. However the crack propagated in ductile manner controlled by the property of the base alloy. That is, there is no or little influence of nitriding on the crack growth rate of the alloy.
查看更多>>摘要：Ultrasonic and rotating bending fatigue tests were carried out for aged and nitrided Ni-base super alloys to investigate the effects of loading frequency and nitriding on fatigue strength. Loading frequencies were 19.5 kHz under ultrasonic and 50 Hz under rotating bending, respectively. Fatigue strength under ultrasonic was higher than that under rotating bending in both alloys. Moreover, in both tests, fatigue strength was improved by nitriding. The increase in fatigue strength by nitriding was large in ultrasonic fatigue. These results were discussed through the successive observation of fatigue process at specimen surface and fracture surface observation.
查看更多>>摘要：This paper deals with the ballistic properties of two kinds of hybrid composites: Kevlar/Carbon laminates and S-Glass/Carbon laminates. Twelve kinds of combinations of samples were made including various fibers; various fiber orientations and various target thickness. Air-gun tests were carried out to determine the response of these combinations of hybrid laminates subject to impact loading.Compared with the test, an explicit finite element (FE) model was built with Pam-crash Code to simulate the impact process. The bullet was considered as a deformable body in contact with the composite shells. The Ladeveze model was used to describe the unidirectional properties of Carbon plies and Ladeveze fabric model was used to describe the homogeneous properties of the S-glass and Kevlar laminates. The influence of different parameters on the impact behavior of the two kinds of hybrid laminates was considered analytically. Results show very good agreement with the experimental data. Suggestions are also presented for the better hybrid mode to improve the ballistic properties.
查看更多>>摘要：The paper deals with the buckling instability of long interface cracks subjected to shear and tensile (compressive) loading parallel to the interface. A simplified mathematical model is developed within the Kirchhoff's plate bending theory; and a general semi-analytical solution is obtained based on the classical strategy for solving for the Euler buckling load. Asymptotic solutions are derived for extreme cases of the applied shear to tensile (compressive) load ratios. The obtained results correlate well with previous numerical studies and can be used to analyze many traditional problems in composite as well as many others, for example, the problem of triggering snow avalanches.
查看更多>>摘要：In this paper the challenges associated with the determination of within section macrostresses in the non-metallic materials porous reactor core graphites, glasses and thermally grown oxides, will be considered, with respect to the length-scale over which such measurements are required. Examples are briefly presented to demonstrate the capability of the methods selected, which include deep hole drilling and photoluminescence and Raman spectroscopy. These techniques span the length-scale from micro-metres to tens of millimetres. The measured values will be discussed with respect to the confidence with which these techniques may be applied and hence benefits for life/integrity evaluation.
查看更多>>摘要：High cycle fatigue behavior of the representative cold forging die steel, YXR3 with Rockwell C scale hardness number of 60.0 is investigated. Axial fatigue strength of plane and notched bar specimens with stress concentration factor, Kt of 1.5, 2.0 and 2.5 is presented. The emphasis is placed upon the subsurface crack initiation observed on notched specimens failed at number of cycles over than 10~6 cycles. Crack initiation and propagation mode of cold forging die steel is discussed with respect to fracture surface morphology.
查看更多>>摘要：Shape memory alloy is a good candidate for realizing the passive control of structural vibration due to its excellent characteristic of energy dissipation. In this paper, the damping characteristic of shape memory alloy is quantitatively described based on Liang's phase transformation model and thermo-mechanical constitutive equation for shape memory alloy. The vibration performances of a beam structure with shape memory alloy damper are investigated based on basic knowledge of vibration theorem. Numerical calculations show that the vibration of beam structure is well reduced by using the shape memory alloy damper.
查看更多>>摘要：An implicit numerical algorithm for the integration of the primary/secondary creep constitutive law at the material point level is derived. For the presented constitutive model, the experimentally obtained material parameters for the medium density polyethylene (MDPE) are taken from literature. The derived algorithm in conjunction with the Jacobian matrix is implemented in the finite element (FE) code ABAQUS by using the user subroutine CREEP. The accuracy of the proposed algorithm is demonstrated.
Pietro BoccaGiuseppe LacidognaAlessandro GrazziniAmedeo Manuello...
237-240页
查看更多>>摘要：An experimental analysis on a set of strengthened masonry walls has been carried out by means of cyclic loading tests in order to simulate the creep effects. The damage evolution of specimens reinforced by traditional or innovative methods is evaluated by the Acoustic Emission (AH) technique. The AE time dependence during fracture propagation is analysed through a power law. In addition, the AE frequency analysis is used to obtain information on the criticality of the ongoing process.
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