共查询到20条相似文献,搜索用时 15 毫秒
1.
This paper addresses quasi-static loading of the shear compression specimen (SCS), that has been especially developed to investigate the shear response of
materials at various strain rates. Previous work [4, 5] addressed bi-linear hardening materials, whereas the present work
concerns parabolic hardening materials. The investigation is done numerically using three-dimensional elastoplastic finite
element simulations. The analyses show that the averaged von Mises stress (
) and strain (
) on a mid-section of the gauge reflect accurately the prescribed parabolic hardening model. A method for finding the parabolic
hardening coefficients and reducing the measured load, P, and displacement, d, into equivalent stress
and strain
is introduced and tested. A very good agreement is observed, thus confirming the potential of the technique for large strain
testing of parabolic hardening materials. 相似文献
2.
K. Arakawa T. Mada H. Komatsu T. Shimizu M. Satou K. Takehara G. Etoh 《Experimental Mechanics》2006,46(6):691-697
The oblique impact between a golf ball and a rigid steel target was studied using a high-speed video camera. Video images
recorded before and after the impact were used to determine the inbound velocity v
i, rebound velocity v
r, inbound angle θi, rebound angle θr, and the coefficient of restitution e. The results showed that θr and e decreased as v
i increased. The maximum compression ratio ηc, contact time t
c, average angular velocity
, and tangential velocity
, along the target were determined from images obtained during the impact. The images demonstrated that ηc increased with v
i while t
c decreased. In addition,
and
increased almost linearly as v
i increased. A rigid body model was used to estimate the final angular velocity ω* and tangential velocity νt* at the end of the impact; these results were then compared with experimental data. 相似文献
3.
We consider the motion of a generalized Newtonian fluid, where the extra stress tensor is induced by a potential with p-structure (p = 2 corresponds to the Newtonian case). We focus on the three dimensional case with periodic boundary conditions and extend the existence result for strong solutions for small times from
\tfrac{5}{3}$$
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(see [16]) to
\tfrac{7}{5}.$$
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Moreover, for
we improve the regularity of the velocity field and show that
for all
0.$$
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Within this class of regularity, we prove uniqueness for all
\tfrac{7}{5}.$$
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We generalize these results to the case when p is space and time dependent and to the system governing the flow of electrorheological fluids as long as
相似文献
4.
Existence of Weak Solutions to the Equations of Non-Stationary Motion of Non-Newtonian Fluids with Shear Rate Dependent Viscosity 总被引:1,自引:0,他引:1
Jörg Wolf 《Journal of Mathematical Fluid Mechanics》2007,9(1):104-138
In the present paper we prove the existence of weak solutions
to the equations of non-stationary motion of an incompressible fluid with shear rate dependent viscosity in a cylinder Q = Ω × (0,T), where
denotes an open set. For the power-low model with
we are able to construct a weak solution
with ∇ · u = 0. 相似文献
5.
We show two examples of systems
in
with
such that |Zt| is strictly decreasing in time for any n but
as
. 相似文献
6.
In this paper, a digital photoelastic system was employed to observe the stress distribution generated by an ultrasonic wave
impinged at the edge of a strip. According to the classical photoelastic theory, gray level distribution of the photoelastic
fringe patterns was formulated and expressed in the form of
, where J0 is the zeroth-order Bessel function. This new technique is called the time-averaged photoelastic method. To verify the proposed
method, the distribution of
was superimposed onto the distribution of gray level of the experimentally obtained photoelastic fringe pattern caused by
standing wave only. Except regions near the center of fringes, well-matched results were found. 相似文献
7.
We investigate the dynamics of the semiflow φ induced on H01(Ω) by the Cauchy problem of the semilinear parabolic equation
on Ω. Here
is a bounded smooth domain, and
has subcritical growth in u and satisfies
. In particular we are interested in the case when f is definite superlinear in u. The set
of attraction of 0 contains a decreasing family of invariant sets
distinguished by the rate of convergence
. We prove that the Wk’s are global submanifolds of
, and we find equilibria in the boundaries
. We also obtain results on nodal and comparison properties of these equilibria. In addition the paper contains a detailed exposition of the semigroup approach for semilinear equations, improving earlier results on stable manifolds and asymptotic behavior near an equilibrium.Supported by DFG Grant BA 1009/15-1. 相似文献
8.
We consider the Cauchy problem for incompressible Navier–Stokes equations
with initial data in
, and study in some detail the smoothing effect of the equation. We prove that for T < ∞ and for any positive integers n and m we have
, as long as
stays finite. 相似文献
9.
A connection between the symmetries of manifolds and differential equations is sought through the geodesic equations of maximally symmetric spaces, which have zero, constant positive or constant negative curvature. It is proved that for a space admitting so(n+1) or so(n,1) as the maximal isometry algebra, the symmetry of the geodesic equations of the space is given by so( or (where d
2 is the two-dimensional dilation algebra), while for those admitting (where represents semidirect sum) the algebra is sl(n+2). A corresponding result holds on replacing so(n) by so(p,q) with p+q = n. It is conjectured that if the isometry algebra of any underlying space of non-zero curvature is h, then the Lie symmetry algebra of the geodesic equations is given by , provided that there is no cross-section of zero curvature at the point under consideration. If there is a flat subspace of dimension m, then the symmetry group becomes ). 相似文献
10.
Takayuki Kobayashi Takashi Suzuki Kazuo Watanabe 《Journal of Mathematical Fluid Mechanics》2006,8(3):382-397
This paper is concerned with the component-wise regularity of the solution to the stationary Maxwell or Stokes systems. We
assume that there is a surface
in R3, regarded as an interface, and the solution u to one of the systems is smooth except for this
. Then, under these assumptions, we can show that some components of u are smooth across
. In the Maxwell system, the normal component of u is always regular across
. On the other hand, in the Stokes system, the singularity of u across
can only arise to the normal derivatives of its tangential components. Furthermore, these results are shown to be optimal. 相似文献
11.
We use the method of multiple scales (MMS) to study small perturbations, governed by a parameter , of a harmonic oscillator by a small term with a large delay. These systems differ significantly from others where small terms have
delays; or an
term has
delay in a system near a Hopf bifurcation. Here, the slow flow in time t depends strongly on even at lowest order, and itself has an
delay. The MMS has already been applied elsewhere for such systems, but only to first order and with attention restricted to periodic and quasiperiodic solutions. Here, we address transients as well as proceed to second order. The second order analysis holds unless a special resonance occurs (we assume it does not). Several numerical examples are presented. In each case, the slow flows are infinite-dimensional, show strong -dependence, require significantly less computation time than the full solutions, yet agree well with the same. 相似文献
12.
This paper presents an analytical and numerical study of transient free convection from a horizontal surface that is embedded in a fluid-saturated porous medium. It is assumed that for time
steady state velocity and temperature fields are obtained in the boundary-layer which occurs due to a uniform flux dissipation rate q
1 on the surface. Then, at
the heat flux on the surface is suddenly changed to q
2 and maintained at this value for
. Firstly, solutions which are valid for small and large
are obtained. The full boundary-layer equations are then integrated step-by-step for the transient regime from the initial unsteady state (
) until such times at which this forward marching approach is no longer well posed. Beyond this time no valid solutions could be obtained which matched the final solution from the forward integration to the steady state profiles at large times
. 相似文献
13.
Some Results on the <Emphasis Type="BoldItalic">m</Emphasis>-Laplace Equations with Two Growth Terms
We prove the existence of positive radial solutions of the following equation:
and give sufficient conditions on the positive functions K1(r) and K2 (r) for the existence and nonexistence of ground states (G.S.) and Singular ground states (S.G.S.), when
or
. We also give sufficient conditions for the existence of radial S.G.S. and G.S. of equation
when
and
, respectively. We are also able to classify all the S.G.S. of this equation. The proofs use a new Emden–Fowler transform which allow us to use techniques taken from dynamical system theory, in particular the ones developed in Johnson et al. (Nonlinear Anal, T.M.A. 20, 1279–1302 (1993)) for the problems obtained by substituting the ordinary Laplacian Δ for the m-Laplacian Δm in the preceding equations.MSC: 37B55, 35H30, 35J70 相似文献
14.
Stefano Leonardi Paolo Orlandi Lyazid Djenidi Robert A. Antonia 《Flow, Turbulence and Combustion》2006,77(1-4):41-57
The effects of 2-D roughness elements on the Reynolds stress anisotropy tensor, and of the energy dissipation rate anisotropy tensor of a turbulent channel flow are investigated using data obtained from direct numerical simulations (DNSs). The roughness elements consist of transverse square rods of size , placed on one wall of the channel only. While is kept constant (, is the half-width of the channel), the spacing between the rods is varied from to . The results show that the variation in can dramatically change the structure of the wall region flow. The modeling of the near-wall region needs to reflect the structural changes caused by the variation in . On the basis of the Reynolds stress budgets, attention needs to be given to the turbulent energy and pressure diffusion terms while local isotropy may be a reasonable approximation for the energy dissipation rate, especially over a range of for which the drag is near its maximum. 相似文献
15.
The in-plane deformation fields near a stationary crack tip for thin, single edge-notched (SEN) specimens, made from Plexiglas, 3003 aluminum alloy and 304 stainless steel, have been successfully obtained by using computer vision. Results from the study indicate that (a) in-plane deformations ranging from elastic to fully plastic can be obtained accurately by the method, (b) for U,
and
, the size of the HRR dominant zone is much smaller than forV and
, respectively. Since these results are in agreement with recent analytical work, suggesting that higher order terms will be needed to accurately predict trends in the data, it is clear that the region where the first term in the asymptotic solution is dominant is dependent on the component of the deformation field being studied, (c) the HRR solution can be used to quantity
only in regions where theplastic strains strongly dominate the elastic strain components (i.e., when
); forV, the HRR zone appears to extend somewhat beyond this region, (d) the displacement componentU does not have the HRR singularity anywhere within the measurement region for either 3003 aluminum or 304 SS. However, the displacement componentV agrees with the HRR slope up to the plastic-zone boundary in 3003 aluminum (
) and over most of the region where measurements were obtained (
) in 304 SS and (e) the effects of end conditions must be included in any finite-element model of typical SEN specimen geometries to accurately calculate theJ integral and the crack-tip fields.Paper was presented at the 1992 SEM Spring Conference on Experimental Mechanics held in Las Vegas, NV on June 8–11. 相似文献
16.
17.
A nonlinear nonlocal model arising from synaptically coupled neuronal networks with two integral terms is considered. The existence and stability of several traveling wave solutions are established by using ideas in differential equations and functional analysis. Steady-state solutions of some inhomogeneous integral–differential equations are also investigated. We consider several types of kernel functions: (I) positive functions, such as
and
, where ρ>0 is a constant; (II) nonnegative kernels with compact supports, for examples, (i)
1$$" align="middle" border="0">
, and (ii)
{\pi\over 2}$$" align="middle" border="0">
; (III) Mexican hat type kernel functions, such as
and
, where A>B>0 and a>b>0 are constants.Dedicated to Professor Yulin Zhou and Professor Boling Guo on the Occassions of their birthdays. 相似文献
18.
Jürgen Saal 《Journal of Mathematical Fluid Mechanics》2006,8(2):211-241
We study the initial-boundary value problem for the Stokes equations with Robin boundary conditions in the half-space
It is proved that the associated Stokes operator is sectorial and admits a bounded H∞-calculus on
As an application we prove also a local existence result for the nonlinear initial value problem of the Navier–Stokes equations
with Robin boundary conditions. 相似文献
19.
R. Danchin 《Journal of Mathematical Fluid Mechanics》2006,8(3):333-381
This paper is devoted to the study of the initial value problem for density dependent incompressible viscous fluids in a bounded
domain of
with
boundary. Homogeneous Dirichlet boundary conditions are prescribed on the velocity. Initial data are almost critical in term
of regularity: the initial density is in W1,q for some q > N, and the initial velocity has
fractional derivatives in Lr for some r > N and
arbitrarily small. Assuming in addition that the initial density is bounded away from 0, we prove existence and uniqueness
on a short time interval. This result is shown to be global in dimension N = 2 regardless of the size of the data, or in dimension N ≥ 3 if the initial velocity is small.
Similar qualitative results were obtained earlier in dimension N = 2, 3 by O. Ladyzhenskaya and V. Solonnikov in [18] for initial densities in W1,∞ and initial velocities in
with q > N. 相似文献
20.
A detailed analytical and experimental investigation is presented to understand the dynamic fracture behavior of functionally
graded materials (FGMs) under mode I and mixed mode loading conditions. Crack-tip stress, strain and displacement fields for
a mixed mode crack propagating at an angle from the direction of property gradation were obtained through an asymptotic analysis
coupled with a displacement potential approach. This was followed by a comprehensive series of experiments to gain further
insight into the behavior of propagating cracks in FGMs. Dynamic photoelasticity coupled with high-speed photography was used
to obtain crack tip velocities and dynamic stress fields around the propagating cracks. Birefringent coatings were used to
conduct the photoelastic study due to the opaqueness of the FGMs. Dynamic fracture experiments were performed using different
specimen geometries to develop a dynamic constitutive fracture relationship between the mode I dynamic stress intensity factor
(K
ID
) and crack-tip velocity (
) for FGMs with the crack moving in the direction of increasing fracture toughness. A similar
-K
ID
relation was also obtained for matrix material (polyester) for comparison purposes. The results obtained show that crack
propagation velocities in FGMs were about 80% higher than the polyester matrix. Crack arrest toughness was found to be about
10% lower than the value of local fracture toughness in FGMs. 相似文献