共查询到20条相似文献,搜索用时 15 毫秒
1.
Clamped circular plates are impulsively loaded with sheet explosive, and the resulting large-defection response is monitored using a high-speed streak camera, and dynamic-strain measurements. Dynamic and final-plate deflections as well as strain-time histories of various locations on the plates are compared to deflections and strains obtained with the elastic-plastic structural computer program DEPROSS. It is shown that DEPROSS adequately computes the dynamic response of this highly nonlinear biaxial-stress problem. 相似文献
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If metal plates are subjected to impulsive loadings a conical shape of the inelastic deformed plates can occur. In the contrary quasi-statically loaded structures, show a more spherical shape of their inelastic deflections. In the present study, an explanation for the development of conical shapes in the case of shock wave loaded plates is proposed based on wave propagation phenomena. The effect of shape forming is studied experimentally with a shock tube and numerically with finite element simulations. 相似文献
3.
The application of the mode approximation technique to a fully clamped circular plate is here described. Mode solutions for finite deflections are obtained from a sequence of instantaneous modes. Master solutions for chosen initial velocity amplitudes are constructed in nondimensional form. These depend weakly on a parameter of viscoplastic material behavior and size of structure, and so can be applied to a variety of loadings and structures. Finding each instantaneous mode shape and acceleration constitutes an eigenproblem, solved by finite elements with iterations. Comparisons with recent tests on steel and titanium plates are discussed in some detail. 相似文献
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Optimal design of a rigid-plastic stepped beam is discussed assuming the mode form of motion. Such beam dimensions are sought for which a minimum of local or mean deflection is attained within designs of constant volume. It is assumed that the prescribed kinetic energy is imparted to the structure at the initial instant with free motion occurring afterwards. It is shown that besides three symmetric modes of motion, also the asymmetric modes may exist. An optimal design for asymmetric modes is determined and compared with a respective design for symmetric modes, obtained previously in [1]. 相似文献
6.
Bounds for finite deflections of impulsively loaded structures with time-dependent plastic behaviort
The paper shows that upper bounds on deflections of an impulsively loaded structure whose behavior in the plastic range is strain rate dependent may be obtained by an application of the theorem of minimum potential energy, with results valid for finite deflections and strains. The concepts of extremal path behavior in strain-time space, due to Ponter, are used in order to provide unique definitions of strain energy and complementary energy for the path dependent material. The theorems are illustrated by examples of fully constrained beams in which deflections of the order of the beam thickness lead to large forces of membrane type. 相似文献
7.
Summary The evaluation of material parameters for viscoplastic Chaboche and Bodner-Partom formulations is carried out using tensile tests only. The determination of the Bodner-Partom law is quite easy. The parameter study for the Chaboche law usually requires carrying out strain-controlled cyclic tests. In this work, we propose supporting this type of experiments by numerical simulations. A set of parameters for each formulation is identified for steel, and is used to calculate the dynamic behaviour of circular plates. The results are compared with the experimental data on steel plates. Received 27 April 1999; accepted for publication 7 October 1999 相似文献
8.
Using a strain-energy approach and the Rayleigh-Ritz procedure, a nonlinear compressible theory was developed to predict the creep deflections of circular plates laterally loaded by a point force acting at the center of the plates. Both clamped and simply supported boundary conditions were considered. The theory applies to transient as well as to steady-state creep. The stress-strain-time relations for the material were represented by a family of isochronous stress-strain curves. For analytical purpose, each curve was approximated by an arc hyperbolic sine function. Experimental data were obtained from eight plates made of high-density polyethylene tested in a controlled-atmosphere room. Material properties were obtained from tension and compression specimens. All test members were subjected to the same load history. An initial load was held constant for a specified time and then increased by 10 percent of its initial value at four equal intervals of time. Good agreement was found between theory and experiment. 相似文献
9.
N. A. Abrosimov N. A. Kulikova 《Journal of Applied Mechanics and Technical Physics》2011,52(1):132-140
A method for identifying the material parameters of the constitutive relations of viscoelastic and elastoplastic deformation
for isotropic and homogeneous composite materials is developed based on minimizing the mismatch between the results of numerical
and experimental modeling of unsteady deformation of structural elements made of the materials studied. The method is tested
and shown to be effective in determining the viscoelastic and elastoplastic characteristics of models for the nonlinear deformation
of impulsively loaded isotropic and composite circular plates. 相似文献
10.
Tests are described of circular plates of mild steel and commercially pure titanium loaded impulsively by means of explosive sheet. Three loading geometries were used, with magnitudes such that final deflections in the range from one to about seven plate thicknesses were produced. Clamping against radial as well as transverse deflections at the edge was provided. Both materials exhibit strong plastic rate sensitivity. Parameters describing this behavior were obtained from stress-strain tests at low to intermediate rates together with published data for high strain rates. The measured final deflections and response times are compared with predictions of the mode approximation technique as extended to large deflections of viscoplastic structures. 相似文献
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The purpose of this investigation was to obtain experimental stress and deflection data for thick, circular, simply supported plates, containing circular transverse perforations in square motif, under uniform lateral loading. The stress-concentration factor and the deflection-multiplier factor, the ratio of the maximum principal stress and the maximum deflection of the perforated plate to that of the solid-plate specimen, respectively, were obtained for each perforated specimen. These factors can be conveniently used for the design of tube sheets, perforated heads, or other similar structural components. 相似文献
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《International Journal of Solids and Structures》2006,43(16):4648-4672
This paper presents an analytical method for the analysis of the dynamic behavior of damaged plates. The proposed approach allows the derivation of mode shapes and corresponding curvature modes for plates with various kinds of defects. Damage is modeled as a localized reduction in the plate thickness. Both point and line defects are considered to model notches or line cracks and delaminations in the plate. Small thickness reductions are considered so that the dynamic behavior of the damage plate can be analyzed through perturbations with respect to the undamaged modes. Results are presented to demonstrate the sensitivity of the curvature modes with respect to the considered low damage levels. Also, the curvature modes are used for the estimation of the strain energy of the plate and for the formulation of a damage index which can be used to provide damage location and extent information. 相似文献
16.
This paper concerns the quadratically-damped Mathieu equation:
17.
Photoelastic coatings were bonded to limestone and granite plates which were then struck on edge with a steel projectile. The resulting fracture zone growth was observed with a reflecting polariscope and recorded with an image converter camera. It is shown that the maximum velocity at which cracks propagate under these circumstances is very much higher than predicted by quasi-steady theories. ‘Apparent’ supervelocity cracks can be generated by shock reflection from bounding interfaces, producing tensile waves of sufficient amplitude to activate and join isolated flaw. Photoelastic coatings are also shown to very much enhance surface-crack visualization subsequent to impact. 相似文献
18.
I. A. Banshchikova A. F. Nikitenko 《Journal of Applied Mechanics and Technical Physics》2006,47(5):747-756
The Rabotnov kinetic creep theory was used to calculate the stress-strain state and damage accumulation in the material of
axisymmetrically loaded circular and ring plates at any time before the beginning of fracture. It is shown that the solution
of the problem can be reduced to solving the same problem under the assumption of steady-state creep of the material. The
unsteady creep problem is solved by multiplying the known solution of the steady-state creep problem by certain functions
of the coordinates and time, which are determined from a corresponding system of equations.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 5, pp. 157–168, September–October, 2006. 相似文献
19.
F. Yang 《Rheologica Acta》1998,37(1):68-72
Based on the perfect slip condition between rigid walls and fluids, the compressive flow of Herschel-Bulkley fluids and biviscous
fluids was studied. The explicit expressions of stresses and fluid velocity were given. To move the rigid walls for a Herschel-Bulkley
fluid with the yield stress (τ0), the mean pressure applied onto the rigid wall should be larger than 2τ0/. No yield surface exists in the interior of the fluids when flow occurs. For a biviscous fluid, a critical load was given.
The fluid behaves like the Bingham fluid when the external applied load onto the wall is larger than the critical load, otherwise
the fluid is Newtonian.
Received: 10 June 1997 Accepted: 22 September 1997 相似文献
20.
The problem of determining stress distributions and reducing stress concentrations around holes in plates occurs in numerous design situations. One method for reducing the stress concentration around a central circular hole in a uniaxially loaded plate was demonstrated by Heywood. With this approach, smaller holes are introduced on either side of the original hole to help smooth the flow of the tensile principal-stress trajectories past the original hole. For the one case reported by Heywood (which did not produce the greatest reduction possible), the maximum stress was reduced to 84 percent of that due to a single hole. In the present program, a systematic study was undertaken using two-dimensional photoelasticity method to determine the optimum sizes and locations for the auxiliary holes for a number of plates with different central-hole diameter-to-plate width ratios. Maximum stress reductions from 13 to 21 percent were demonstrated for plates with hole diameter-to-plate width ratios between 0.1 and 0.6. With such reductions in maximum stress level, the improvement in fatigue life of a part can be very significant. 相似文献