共查询到20条相似文献,搜索用时 10 毫秒
1.
The shear compression specimen (SCS), which is used for large strain testing, is thoroughly investigated numerically using
three-dimensional elastoplastic finite element simulations. In this first part of the study we address quasi-static loading.
A bi-linear material model is assumed. We investigate the effect of geometrical parameters, such as gage height and root radius,
on the stress and strain distribution and concentration. The analyses show that the stresses and strains are reasonably uniform
on a typical gage mid-section, and their average values reflect accurately the prescribed material model. We derive accurate
correlations between the averaged von Mises stress and strain and the applied experimental load and displacement. These relations
depend on the specimen geometry and the material properties. Numerical results are compared to experimental data, and an excellent
agreement is observed. This study confirms the potential of the SCS for large strain testing of material. 相似文献
2.
Part I of this work addressed quasi-static loading of the shear compression specimen (SCS), which has been especially developed
to investigate the shear dominant response of materials at various strain rates. The stress and strain states were characterized
numerically. Approximations were presented to reduce the measured load,P, and displacement,d, into equivalent stress
and strain
. This paper addresses dynamic loading of the SCS. Several simulations were made for representative materials, whose stress-strain
behavior is assumed to be rate-independent. The results show that stress wave loading induces strong oscillations in theP-d curve. However, the
curve remains smooth in the gage section. The oscillations are about the quasistatic load values, so that with suitable filtering
of the dynamicP-d curves, the quasi-static ones are readily recovered. Consequently, the approach that was developed for quasi-static loading
of the SCS is now extended to dynamic loading situations. The average strain rate is rather constant and scales linearly with
the prescribed velocity. As the plastic modulus becomes smaller, the strain rate reaches higher values. Friction at the end
pieces of the specimen is also investigated, and shown to have a small overall influence on the determined mechanical characteristics.
This paper thereby confirms the potential of the SCS for large strain testing of materials, using a unified approach, over
a large range of strain rates in a seamless fashion. 相似文献
3.
In this paper we describe the design and manufacture of an axial-torsion test specimen, and provide relationships needed when
conducting stress-strain characterization experiments with the specimen. The specimen is a short hollow cylinder of rubber
bonded between two steel mounting rings, in which simultaneous axial and shear strains are produced via independently controlled
axial and twist displacements. We present calculations for the strain-displacement and stress-load relationships, and strain
energy density. These relationships have been established and validated via a combination of analytical and experimental techniques,
and finite element analysis. We have investigated the extent and effects of strain and stress field non-uniformity in the
test specimen. The specimen design is sufficiently simple that a closed-form expression for the strain-displacement relationship
has been successfully developed. 相似文献
4.
Introduction Thedeformationofsaturatedsoftclayisoneofimportantquestionsingeotechnical engineering.Thenotablecharacteristicisthatthedegreeofitsstrainisgenerallylargerthan10percent.Oneofthecauses[1],Whichleadtoaquantitativedifferencebetweenthe numericalsimu… 相似文献
5.
In this study, slow strain rate tensile testing at elevated temperature is used to evaluate the influence of temperature and strain rate on deformation behaviour in two different austenitic alloys. One austenitic stainless steel (AISI 316L) and one nickel-base alloy (Alloy 617) have been investigated. Scanning electron microscopy related techniques as electron channelling contrast imaging and electron backscattering diffraction have been used to study the damage and fracture micromechanisms. For both alloys the dominante damage micromechanisms are slip bands and planar slip interacting with grain bounderies or precipitates causing strain concentrations. The dominante fracture micromechanism when using a slow strain rate at elevated temperature, is microcracks at grain bounderies due to grain boundery embrittlement caused by precipitates. The decrease in strain rate seems to have a small influence on dynamic strain ageing at 650°C. 相似文献
6.
Xie Daji Feng Shengbo Zhao Rufa Hu Degui Gu Shouren Wang Zengmei 《Acta Mechanica Solida Sinica》1998,11(2):159-171
Experiments on specimens of mild steel and cast iron have been performed under various loading conditions. A modified formula
is pur forward to analyze the cruciform specimen which is often used in magnetic methods for calibration. We assume that the
relationship between the magnetic output and strain is linear and a new four-coefficient method is deduced. Finally, the results
of practical applications are given. 相似文献
7.
R.K. Boger R.H. Wagoner F. Barlat M.G. Lee K. Chung 《International Journal of Plasticity》2005,21(12):2319-2343
Modeling sheet metal forming operations requires understanding of the plastic behavior of sheet alloys along non-proportional strain paths. Measurement of hardening under reversed uniaxial loading is of particular interest because of its simplicity of interpretation and its application to material elements drawn over a die radius. However, the compressive strain range attainable with conventional tests of this type is severely limited by buckling. A new method has been developed and optimized employing a simple device, a special specimen geometry, and corrections for friction and off-axis loading. Continuous strain reversal tests have been carried out to compressive strains greater than 0.20 following the guidelines provided for optimizing the test. The breadth of application of the technique has been demonstrated by preliminary tests to reveal the nature of the Bauschinger effect, room-temperature creep, and anelasticity after strain reversals in commercial sheet alloys. 相似文献
8.
9.
10.
A constitutive model for diffusionless phase transitions in elastoplastic materials undergoing large deformations is developed. The model takes basic thermodynamic relations as its starting point and the phase transition is treated through an internal variable (the phase fractions) approach. The usual yield potential is used together with a transformation potential to describe the evolution of the new phase. A numerical implementation of the model is presented, along with the derivation of a consistent algorithmic tangent modulus. Simulations based on the presented model are shown to agree well with experimental findings. The proposed model provides a robust tool suitable for large-scale simulations of phase transformations in austenitic steels undergoing extensive deformations, as is demonstrated in simulations of the necking of a bar under tensile loading and also in simulations of a cup deep-drawing process. 相似文献
11.
During recent years, the investigation of the strain-rate-dependent properties of materials has become more and more important.
The experimental techniques used to establish the specific dynamic behavior of materials all have in common that the acquisition
of information concerning the deformation of the specimen is cumbersone and often questionable. Mostly, only limited information
on the spatial distribution and time evolution of the deformation in specimen can be obtained. In this paper, a non-contact,
optical technique is presented, providing the time evolution and spatial distribution of the axial deformation in specimens
during a high strain rate test. The deformation of a line grid attached to the specimen is recorded during an experiment by
means of a rotating drum camera. The time history of the axial displacements is subsequently derived by an advanced technique
based on digital geometric moiré combined with a phase-shift method, specially developed to this purpose. The technique can
be applied to a wide range of materials and high strain rate tests, and is illustrated by means of a split Hopkinson tensile
bar experiment on a steel sheet specimen. 相似文献
12.
On the application of the additive decomposition of generalized strain measures in large strain plasticity 总被引:2,自引:0,他引:2
In the present paper two thermodynamically consistent large strain plasticity models are examined and compared in finite simple shear. The first model (A) is based on the multiplicative decomposition of the deformation gradient, while the second one (B) on the additive decomposition of generalized strain measures. Both models are applied to a rigid-plastic material described by the von Mises-type yield criterion. Since both models include neither hardening nor softening law, a constant shear stress response even for large amounts of shear is expected. Indeed, the model A exhibits the true constant shear stress behavior independent of the elastic material law. In contrast, the model B leads to a spurious shear stress increase or drop such that its applicability under finite shear deformations may be questioned. 相似文献
13.
14.
An experimental strain analysis of the losipescu shear test specimen was performed, utilizing a 20-ply AS4/3501-6 carbon/epoxy
unidirectional composite. Using three-element strain-gage rosettes, it was shown that the presence of loading-point-induced
transverse normal strains in the gage section do not affect the measured shear strain. Thus, the shear modulus determined
using the standard notch specimen is not affected. Likewise, modulus determination is not influenced by cracking at the notch
tips, since this occurs at strains beyond the range over which modulus is determined. To further evaluate the effect of notch-tip
cracking, material was removed adjacent to the standard V-notches where these cracks initiate. The measured shear strength
was unaffected by removing this material, although the shear modulus was reduced slightly (by as much as eight percent for
the more grossly exaggerated geometries).
E.Q. Lewis, former graduate student, is now Engineer, Lockheed Corporation. 相似文献
15.
Large strain fixed-end torsion of circular solid rubber bars is studied semi-analytically. The analyses are based on various
non-Gaussian network models for rubber elasticity, some of which were proposed very recently. Results are presented in terms
of predicted torque vs. twist curves and axial force vs. twist curves. In some cases, the predicted stress distributions are
also given. The sensitivity of the second-order axial force to the employed models is considered. The predicted results are
compared with experimental results found in the literature. 相似文献
16.
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
17.
Large strain field near a crack tip in a rubber sheet 总被引:1,自引:0,他引:1
The distribution of stress-strain near a crack tip in a rubber sheet is investigated by employing the constitutive relation given by Gao (1997). It is shown that the crack tip field is composed of two shrinking sectors and one expanding sector. The stress state near the crack tip is in uniaxial tension. The analytical solutions are obtained for both expanding and shrinking sectors. 相似文献
18.
19.
A new design of the shear compression specimen (SCS) for investigating the viscoelastic shear response of polymers is presented.
The specimen consists of a polymer gage section with two metal ends that remain essentially rigid during deformation. Two
closed-form analytic models are developed to predict the average stress and strain in the gage section from the deformation-load
histories. This new SCS design and its analytic models are thoroughly evaluated via laboratory measurements and numerical
simulations. These simulations show that the deformations in the gage section are more uniform than in the original design,
and the distribution of the average shear stress and strain are highly homogenous. The simulation results yield good agreement
with those of closed-form analytic results and the experiments demonstrate that the new SCS geometry and its analytic models
are as reliable as other commonly employed specimens. It can also generate higher strain rates under usual loading conditions
because of its smaller specimen gage length. The need for care in specimen preparation is also discussed in detail as illuminated
by the experimental and simulation results.
相似文献
W.G. Knauss (SEM Fellow)Email: |
20.
Surjani Uthayakumaran Marcus Newberry Nhan Phan-Thien Roger Tanner 《Rheologica Acta》2002,41(1-2):162-172
The rheological properties of wheat gluten were studied under both small and large deformation and compared with those of
the parent flours. The limiting strain of linear viscoelastic behaviour of gluten doughs, 3 × 10−2, was an order of magnitude larger than that of the flour doughs, 10−3. The role of starch in the lower limiting strain of flour doughs was indicated by the exponential decrease in the limiting
strain of gluten-starch mixtures with greater quantities of starch. Large strain measurements showed gluten doughs possessed
greater shear and elongational viscosities than flour doughs and these differences were greatest at lower shear and elongation
rates (0.01 and 0.1 s−1). The larger viscosities of flour and gluten doughs at the low strain rates help to stabilise and prevent the collapse of
gas bubbles during bread fermentation and baking. Increasing starch levels in gluten-starch mixtures, at either constant or
optimal water levels, lowered the elongational viscosity. Dynamic measurements were, however, more sensitive to the level
of water added to the gluten-starch mixtures. The storage modulus decreased with increasing starch levels when constant water
levels were used to prepare the mixtures, but when optimal water levels were used the storage modulus increased. Gluten and
starch are major contributors to the large and small strain rheological properties of flour doughs; however, gluten-starch
mixtures were unable to duplicate exactly the rheological properties of flour doughs, indicating that other flour components
such as pentosans, lipids and water soluble proteins also influence dough rheology.
Received: 20 March 2001 Accepted: 11 July 2001 相似文献