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71.
平面坡体渐进破坏模型及其应用 总被引:5,自引:0,他引:5
平面坡体渐进破坏模型旨在通过在坡体稳定性分析中引进渐进坡坏的概念,来较合理地考虑岩土材料的峰值强度和残余强度在稳定性分析中的不同作用。通过与其它稳定性分析方法进行比较以及实例应用研究,证明该计算模型可用于初步判断坡体稳定状态并估算其破坏变形范围。这一研究也说明了水对边坡破坏的重要作用。 相似文献
72.
D.A. Hall B. Cherdhirunkorn P.J. Withers T. Mori 《Journal of the mechanics and physics of solids》2005,53(2):249-260
This paper presents micromechanics based analysis of elastic strain and changes in the texture of poled polycrystalline ferroelectric PZT ceramics for direct comparison with synchrotron X-ray measurements. The grains are modelled as spherical inclusions, to which transformation strains are assigned depending on the fractions of different ferroelectric domains. Eshelby's inclusion problem with the classical self-consistent method is applied to evaluate the elastic state of the grains. In particular, the elongation due to lattice elastic strain is calculated as a function of inclination Ψ relative to the polar axis. The ratio of diffraction peak intensities, corresponding to the domain fractions, is also expressed as a function of Ψ. This analysis identifies the special character of the reflection, for which the lattice strain along in the stress free state is independent of ferroelectric domain population and hence unaffected by poling. The elongation due to the lattice strain parallel to and peak intensity ratio are expressed in terms of the overall macroscopic strain of a poled specimen, each having a dependence. 相似文献
73.
Based on von Mises’ yield criterion, deformation theory of plasticity and Swift’s hardening law, elasto-plastic deformation of variable thickness annular disks subjected to external pressure is studied. A nonlinear shooting method using Newton’s iterations with numerically approximated tangent is designed for the solution of the problem. Considering a thickness profile in the form of a general parabolic function, the condition of occurrence of plastic deformation at the inner and outer edges of the annular disk is investigated. A critical disk profile is determined and the corresponding elastic–plastic stresses as well as the residual stress distribution upon removal of the applied pressure are computed and discussed. 相似文献
74.
In recent years, the hole drilling method for determining residual stresses has been implemented with optical methods such
as holographic interferometry and ESPI to overcome certain limitations of the strain rosette version of hole drilling. Although
offering advantages, the interferometric methods require vibration isolation, a significant drawback to their use outside
of the laboratory. In this study, a 3D image correlation approach was used to measure micron-sized surface displacements caused
by the localized stress relief associated with hole drilling. Residual stresses were then found from the displacements using
non-dimensional relations previously derived by finite element analysis. A major advantage of image correlation is that it
does not require interferometric vibration isolation. Experiments were performed to check the ability of this new approach
for uniaxial and equi-biaxial states of stress. Stresses determined by the approach were in good agreement with computed values
and those determined by hole drilling using holographic interferometry. 相似文献
75.
76.
An experimental study has been undertaken to investigate the shrinkage characteristics of acrylic-based and epoxy-based stereolithography
(SL) photopolymer resin systems after they have been laser cured and post-cured under ultraviolet (UV), and thermal exposure.
The induced residual stresses and strains were determined by the shadow moiré and the hole-drilling strain-gage methods. Out-of-plane
displacements (warpage) of acrylic-based post-cured resin plates were recorded by means of the shadow moiré method and correlated
to the shrinkage strains by theoretical analysis. The induced residual stresses in the epoxy-based cylindrical resin specimens
were determined from strains of three-element strain-gage rosettes of the blind-hole drilling method. Results are presented
for the shrinkage stresses and strains for both material systems as a function of the post-curing process (UV, thermal). It
was found that the shrinkage strains in the acrylic-based photopolymer resin were of considerable magnitude, while thermal
post-curing resulted in higher shrinkage stresses for both material systems. The values of the shrinkage stresses compare
well with those of the existing literature. 相似文献
77.
A non-linear algorithm of photoelastic tomography for the measurement of axisymmetric stress fields has been elaborated. It
is free of any assumptions concerning the value of the birefringence or rotation of the principal stress axes along the light
rays. The algorithm is based on the measurement of characteristic directions and phase retardation in two parallel sections
of the test object. Stress components are presented in the form of power series along the radial coordinate. A differential
evolution algorithm has been used for finding the stress field parameters, which fit the measurement data best. Application
of the method is illustrated by residual stress measurement in a drinking glass. 相似文献
78.
79.
Lars Erik Schmidt Daniel Schmäh Yves Leterrier Jan-Anders E. Månson 《Rheologica Acta》2007,46(5):693-701
The photocuring of three different highly functional acrylates—Di-pentaerythritol penta/hexaacrylate (DPHA) and two hyperbranched
molecules (HBP), one with a stiff polyester and one with a more flexible polyether structure—was investigated by means of
photorheology, photo differential scanning calorimetry, and beam bending. Special attention was paid to the influence of the
composition of DPHA/HBP reactive blends and UV intensity on gelation and vitrification and the resulting dynamics of the internal
stress. It was found that adding HBPs to DPHA did not influence gelation significantly, but shifted the onset of vitrification
to higher conversions and thus caused lower internal stresses in the material. Increasing UV intensity increased both the
conversion at vitrification, thus retarding the build-up of internal stresses, and the ultimate conversion, thus increasing
the final stress level. The obtained conversion, gelation, and vitrification data were assembled into time-intensity transformation
diagrams, thus providing a useful tool for optimizing photocuring.
This paper was presented at Annual European Rheology Conference (AERC) held in Hersonisos, Crete, Greece, April 27–29, 2006. 相似文献
80.
L. Nicola K.-S. Kim E. Van der Giessen 《Journal of the mechanics and physics of solids》2007,55(6):1120-1144
The indentation of single crystals by a periodic array of flat rigid contacts is analyzed using discrete dislocation plasticity. Plane strain analyses are carried out with the dislocations all of edge character and modeled as line singularities in a linear elastic solid. The limiting cases of frictionless and perfectly sticking contacts are considered. The effects of contact size, dislocation source density, and dislocation obstacle density and strength on the evolution of the mean indentation pressure are explored, but the main focus is on contrasting the response of crystals having dislocation sources on the surface with that of crystals having dislocation sources in the bulk. When there are only bulk sources, the mean contact pressure for sufficiently large contacts is independent of the friction condition, whereas for sufficiently small contact sizes, there is a significant dependence on the friction condition. When there are only surface dislocation sources the mean contact pressure increases much more rapidly with indentation depth than when bulk sources are present and the mean contact pressure is very sensitive to the strength of the obstacles to dislocation glide. Also, on unloading a layer of tensile residual stress develops when surface dislocation sources dominate. 相似文献