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31.
32.
A system of linear electroelastic equations for small fields superposed on a bias is applied in the determination of the velocity of acoustic surface waves in piezoelectric substrates subject to flexural biasing stresses. The influence of the biasing stresses appears in the boundary conditions as well as the differential equations. Direct calculations performed for both quartz and lithium niobate when the spatial variation of the flexural biasing state is omitted indicate that the biasing stresses in the boundary conditions have an important influence of the surface wave velocity. In addition, perturbation calculations are performed which include the influence of the spatial variation of all flexural biasing terms and it is shown that, for substrate thickness-to-wavelength ratios well within the practical range, the spatial variation in the biasing state has an appreciable effect on the velocity of acoustic surface waves. 相似文献
33.
Dewey H. Hodges 《International Journal of Non》1977,12(5):293-296
The extensional equations of motion for a cantilever bar rotating about an axis fixed in space are derived. It is shown that the form of the non-linear strain-displacement relation is important in determining the nature of the relationship between the frequency of extensional oscillations and the rotational speed. In particular, the frequency may or may not increase monotonically with rotational speed, depending on the degree of hardening in the effective extensional spring. The determination whether an instability occurs as the rotational speed increases is beyond the limits of engineering beam theory. 相似文献
34.
James G. Simmonds 《International Journal of Solids and Structures》1975,11(9):1051-1056
Solutions of the two Reissner-Meissner linear equations for the torsionless, axisymetric deformation of elastically isotropic shells of revolution of constant thickness subject to edge conditions and variable normal pressure are compared with the solutions of a simplified version of these equations obtained by neglecting terms containing Poisson's ratio. The relative pointwise differences in the predicted values for the change in the meridional angle and a stress function are shown to be of the same order of magnitude as the inherent errors in classical, first-approximation shell theory. These results do not depend on physical arguments or asymptotic integration techniques, but rather follow from the structure of the Reissner-Meissner equations themselves. The advantage of the simplified equations is that they may be combined into a single comple-valued equation containing no conjugates of the dependent variable. 相似文献
35.
The theory derived in Part I is compared to data obtained from flyer-plate experiments on laminated composites. The composites were constructed of alternating layers of aluminum and polymethyl methacrylate. Impact occurred on a flat plane oriented perpendicular to the interface planes of the composite constituents. As opposed to the behavior of a fully bonded composite which allows only one longitudinal stress wave to propagate through its interior, two longitudinal stress waves were observed in the debonded composite.Reasonable agreement was achieved in the comparisons of theory to experiment after adjustment was made for the effect of residual bond strength at the constituent interfaces. 相似文献
36.
The problem of an anisotropic ellipsoidal inclusion which undergoes a stress-free transformation strain (in the sense of J.D. Eshelby) is considered, and the following theorem is proved: If an ellipsoidal region in an infinite anisotropic linear elastic medium undergoes, in the absence of its surroundings, a stress-free transformation strain which is a polynomial of degree M in the position coordinates xt, then the final stress and strain state in the transformed inclusion, when constrained by its surroundings, is also a polynomial of degree M in xt. 相似文献
37.
The creeping motion along their line of centers of two fluid spheres in contact is analyzed. An exact solution is presented. Corrections to the Hadamard—Rybezynski equation are tabulated for various particle radii ratios and particle fluid to external fluid viscosity ratios. In the limit of infinite particle viscosity, these corrections are shown to agree with previous calculations for rigid spheres. 相似文献
38.
A unified theory of thermoviscoplasticity of crystalline solids is presented. In particular it is shown that a thermodynamics for ‘viscoplastic’ materials can be accommodated within the framework of modern mechanics of materials with memory. The basic physical concepts are derived from the consideration of dislocation behaviour of crystalline solids. Relationships of the present approach to several of the existing theories of plasticity are examined. 相似文献
39.
This paper reports an experimental investigation to test the hypothesis that the critical resolved shear stress is independent of the resolved normal stress on the active slip system plane. The resolved normal stress is varied independently for crystals of constant orientation by applying a uniform biaxial tension stress through slitted rubber strips glued to a flat tension sample. It is found that the critical resolved shear stress is constant until the resolved normal stress on the active slip system becomes twice the resolved shear stress; and then, for further increases in the resolved normal stress, the critical resolved shear stress begins to decrease. 相似文献
40.
This paper investigates multiple modeling choices for analyzing the rich and complex dynamics of high-speed milling processes.
Various models are introduced to capture the effects of asymmetric structural modes and the influence of nonlinear regeneration
in a discontinuous cutting force model. Stability is determined from the development of a dynamic map for the resulting variational
system. The general case of asymmetric structural elements is investigated with a fixed frame and rotating frame model to
show differences in the predicted unstable regions due to parametric excitation. Analytical and numerical investigations are
confirmed through a series of experimental cutting tests. The principal results are additional unstable regions, hysteresis
in the bifurcation diagrams, and the presence of coexisting periodic and quasiperiodic attractors which is confirmed through
experimentation. 相似文献