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1.
A modified version of the Kolsky thin-wafer technique is described. The method permits one to obtain the dynamic plastic properties of materials at strain rates as high as 105 sec?1. Data obtained from compression tests on high-purity aluminum are presented for strain rates ranging from 4000 to 120,000 sec?1 at room temperature. Specimen-size effects and the effect of lateral inertia are taken into account in analyzing the data. The results plotted as stress vs. strain rate at constant strains (5 to 20 percent) show that, at the highest strain rates, the stress rises very rapidly with strain rate suggesting that a limiting strain rate is being reached. At the lower strain rates (103 to 104 sec?1), the stress is linearly proportional to the strain rate indicating that the material is deforming in a viscous manner. 相似文献
2.
Measurement results for the shock wave compression profiles of 12Cr19Ni10Ti steel and its dynamic strength in the strain rate range 105–106 s?1 are presented. The protracted viscous character of the spall fracture is revealed. With the previously obtained data taken into account, the measurement results are described by a polynomial relation, which can be used to construct the fracture kinetics. On the lower boundary of the range, the resistance to spall fracture is close to the value of the true strength of the material under standard low-rate strain conditions; on the upper boundary, the spall strength is more than twice greater than this quantity. An increase in the temperature results in a decrease in both the dynamic limit of elasticity and the spall fracture strength of steel. The most interesting result is the anomaly in the dependence of the spall fracture strength on the duration of the shock wave compression pulse, which is related to the formation of deformation martensite near the growing discontinuities. 相似文献
3.
Frank E. Hauser 《Experimental Mechanics》1966,6(8):395-402
The qualitative dependence of the mechanical behavior of some materials on strain rate is now well known. But the quantitative relation between stress, strain and strain rate has been established for only a few materials and for only a limited range. This relation, the so-called constitutive equation, must be known before plasticity or plastic-wave-propagation theory can be used to predict the stress or strain distribution in parts subjected to impact stresses above the yield strength. In this paper, a brief review of some of the experimental techniques for measuring the stress, strain, strain-rate relationship is given, and some of the difficulties and shortcomings pointed out. Ordinary creep or tensile tests can be used at plastic-strain rates from 10?8 to about 10?1/sec. Special quasi-static tests, in which the stress- and strain-measuring devices as well as the specimen geometry and support have been optimized, are capable of giving accurate results to strain rates of about 102/sec. At higher strain rates, it is shown that wave-propagation effects must be included in the design and analysis of the experiments. Special testing machines for measuring stress, strain and strain-rate relationships in compression, tension and shear at strain rates up to 105/sec are described, and some of the results presented. With this type of testing machine, the analysis of the data requires certain assumptions whose validity depends upon proper design of the equipment. A critical evaluation of the accuracy of these types of tests is presented. 相似文献
4.
In order to predict the high-temperature deformation behavior of Al-Zn-Mg-Cu alloy, the hot compression tests were conducted
in the strain rate range of (0.001–0.1)s−1 and the forming temperature range of (573–723) K. Based on the experimental results, Johnson-Cook model was found inadequate
to describe the high-temperature deformation behavior of Al-Zn-Mg-Cu alloy. Therefore, a new phenomenological constitutive
model is proposed, considering the coupled effects of strain, strain rate and forming temperature on the material flow behavior
of Al-Zn-Mg-Cu alloy. In the proposed model, the material constants are presented as functions of strain rate. The proposed
constitutive model correlates well with the experimental results confirming that the proposed model can give an accurate and
precise estimate of flow stress for the Al-Zn-Mg-Cu alloy investigated in this study. 相似文献
5.
W. W. Wood 《Experimental Mechanics》1967,7(10):441-446
The early experimental work of Clark and Wood with regard to von Kármán's theory on the effect of material flow and fracture at high strain rates has led to many controversial issues on these effects. Interest has been greatly revived in recent years because of the increased emphasis on such high-velocity forming processes as explosive and capacitor discharge. Considerable new work has been performed by Ling-Temco-Vought, Inc., for the Air Force, the results of which are presented in this paper. Data have been accumulated on tensile and compression specimens, spherical bulging and cylindrical bulging for a wide variety of materials. This high-speed information has been generated with the use of a special projectile impact machine and special presses utilizing various combinations of explosive and capacitor-discharge energy, with strain rates to 101/sec. The effect of velocity on ductility is discussed for total strain distribution, uniform strain, double necking and critical impact velocity. The modes of failure for various part shapes are presented and related to the forming velocity. 相似文献
6.
《International Journal of Plasticity》2003,19(4):383-401
Ductile metals containing initially negligible micro-void density are treated. Such materials are popularly used in metal forming processes. Variation of material density due to plastic deformation is investigated experimentally using very severe plane strain compression, and uni- and equi-biaxial tension. No volume or density change is measured even after very severe plane-strain compression, in contrast with its change after tensile deformation. With reference to the experimental results, the existing plasticity theory with compressibility is examined thoroughly, and a new proposition is presented. The decomposition of the void evolution rate into growth and nucleation terms is absolutely improved, in addition to other faults in the existing theory such as an unrealistically sharp rise in density decrease at early deformation. Several examples of the relationship between density change and the given equivalent strain are illustrated regarding tensile loadings to confirm the significance of the new proposition. Apart from density change, it is found in plane strain compression that, surprisingly enough, pure copper can deform stably up to about 34 in the logarithmic strain measure, which is equivalent to an elongation of about 4.3×1014 times its initial length in uniaxial tension. 相似文献
7.
《International Journal of Plasticity》2006,22(8):1506-1529
A comprehensive study of the thermo-mechanical response of a thermoplastic polymer, nylon 101 is presented. Quasi-static and dynamic compression uniaxial and multi-axial experiments (stress states) were performed at a wide range of strain rates (10−5 to 5000 s−1) and temperatures (−60 to 177 °C or −76 to 350 °F). The material is found to be non-linearly dependent on strain rate and temperature. The change in volume after plastic deformation is investigated and is found to be negligibly small. The relaxation and creep responses at room temperature are found to be dependent on strain rate and the stress–strain level at which these phenomena are initiated. Total deformation is decomposed into visco-elastic and visco-plastic components; these components have been determined at different levels of deformation. Results from non-proportional uniaxial to biaxial compression, and torsion experiments, are also reported for three different strain rates at room temperature. It is shown that nylon 101 has a response dependent on the hydrostatic pressure. 相似文献
8.
以泡沫陶瓷复合材料在防护工程中的应用为背景,利用MTS(Material Test System,材料试验机)对该型材料进行了准静态压缩实验。得到了应变率在10-5~10-3s-1范围内的应力应变曲线,并对实验结果进行了理论分析和数值模拟。研究表明,泡沫陶瓷复合材料的力学性能在准静态一维应力压缩条件下显示出明显的应变率效应,同时其应力应变曲线可用一种经验的脆性材料本构模型进行较好地拟合。而在一维应变压缩条件下,材料的应力应变曲线则显示出明显的三段式特征:弹性段、平台段和密实段,同时材料的吸能幅值随着应变率的增大而增加。 相似文献
9.
Experimental analysis of dynamic mechanical properties for artificially frozen clay by the split Hopkinson pressure bar 总被引:2,自引:0,他引:2
Qin-Yong Ma 《Journal of Applied Mechanics and Technical Physics》2010,51(3):448-452
A device for impact compression experiments is the split Hopkinson pressure bar with a refrigerating attemperator. Data for
incident and reflected waves are obtained by the measuring technique with strain gauges, and data for transmitted waves are
obtained by the measuring technique with semiconductor gauges. Static compression tests of frozen clay are conducted at an
identical temperature and different strain rates of 0.001 and 0.01 sec
−1
. Dynamic stress-strain curves are obtained at strain rates of 360–1470 sec
−1
. The low and high temperatures correspond to high and low strain rates, respectively. It is shown that both the temperature
and strain rate affect the frozen soil deformation process. Different dynamic stress-strain curves obtained at the same temperature
but different strain rates are found to converge. The test results indicate that frozen soil has both temperature-brittleness
and impact-brittleness. 相似文献
10.
Zhilun Lu Qinglin Pan Xiaoyan Liu Yinjiang Qin Yunbin He Sufang Cao 《Mechanics Research Communications》2011,38(3):192-197
The behavior of the flow stress of Al-Cu-Mg-Ag heat-resistant aluminum alloys during hot compression deformation was studied by thermal simulation test. The temperature and the strain rate during hot compression were 340-500 °C, 0.001 s−1 to 10 s−1, respectively. Constitutive equations and an artificial neural network (ANN) model were developed for the analysis and simulation of the flow behavior of the Al-Cu-Mg-Ag alloys. The inputs of the model are temperature, strain rate and strain. The output of the model is the flow stress. Comparison between constitutive equations and ANN results shows that ANN model has a better prediction power than the constitutive equations. 相似文献
11.
Theodore Nicholas 《Experimental Mechanics》1981,21(5):177-185
A tension version of the split Hopkinson bar or Kolsky apparatus is developed for conducting tests in tension at high rates of strain up to 103 s?1. A number of aluminum, titanium, and steel alloys tested in tension show increasing degrees of rate sensitivity above 10 to 102 s?1. Tests on 6061-T651 and 7075-T6 aluminum show measurable strain-rate sensitivity in tension at the highest strain rates, although similar tests in compression in the literature show essentially no strain-rate sensitivity. Details of the apparatus and instrumentation and guidelines for its use are presented. 相似文献
12.
《International Journal of Plasticity》1996,12(3):273-294
The thermomechanical behavior of casting sands is discussed from an experimental and a theoretical point of view. Uniaxial compression tests at temperatures ranging from 20°C to 950°C and at different values of strain rate (ϵ = 10−2 s−1, ϵ = 10−3 s−1 and ϵ = 10−4 s−1) have been performed. They show that casting sands exhibit no strain rate effect in the temperature range 20–600°C, and that an elastoplastic model is well suited to describe the experimental results. Three thermoelastoplastic models, derived from Cam Clay and Hujeux models have been developed. These new models take into account the cohesion of the material. The physical parameters needed for these models have been obtained in the temperature range 20–300°C by using triaxial tests, uniaxial compression tests, isotropic compression tests and die pressing tests. An original triaxial apparatus has been built allowing a temperature of 800°C and a pressure of 4 MPa to be reached. In the temperature at which the parameters have been obtained (20–300°C), two additional triaxial compression tests at different confining pressures are used to check the validity of the thermoelastoplastic models used. The best quantitative results are obtained with the revised modified Cam Clay model. 相似文献
13.
We modify the split Hopkinson pressure bar and propose a compression–shear experimental method to investigate the dynamic
behavior of polymer-bonded explosives (PBXs). The main apparatuses used include an incident bar with a wedge-shaped end and
two transmission bars. We employ Y-cut quartzes with a rotation angle of 17.7° to measure the shear force and an optical system
for shear strain measurement. A PBX with a density of 1.7 g/cm3 is investigated using the proposed method. Experimental results show that the specimen endures both compression and shear
failure. Compression failure stress rises, and shear failure stress decreases as the strain rate increases. The sequences
of shear and compression failure times are various at different strain rates. Based on the maximum shear failure criterion,
we conclude that these phenomena are related to the experimental loading path. 相似文献
14.
Mei yan Zhan Zhenhua Chen Hui Zhang Weijun Xia 《Mechanics Research Communications》2006,33(4):508-514
The hot deformation behavior of porous FVS0812 aluminum alloy prepared by spray deposition was studied by means of compression tests on a Gleeble 1500 machine. The samples were hot compressed at temperatures ranging from 573 K to 773 K under various true strain rates of 10−4–100 s−1. The deformation behaviors are characterized by a significant strain hardening during hot-compression due to the progressive compaction of the pores with increasing compressive strain. A revised formula describing the relationships of the flow stress, strain rate and temperature of the porous alloy at elevated temperatures is proposed by compensation of strain. The theoretical predictions are compared with experimental results, which show good agreement. 相似文献
15.
A. S. Yunoshev V. V. Sil'vestrov 《Journal of Applied Mechanics and Technical Physics》2001,42(3):558-564
A compression version of the split Hopkinson bar with pressure bars and a striker, which are made of Plexiglas (a material with low density and velocity of sound) is developed. The technique is designed to determine stress—strain diagrams under high strain rates of highly deformable materials with low density and strength, such as plastics, foams, and rubbers. Dynamic stress—strain curves in compression for spheroplastic, foam plastic, and rubber are presented, which were obtained using the technique developed. 相似文献
16.
17.
Electromagnetic Cam Driven Compression Testing Equipment 总被引:1,自引:0,他引:1
This paper presents innovative equipment for the compression testing of materials under high rates of loading (above 1,000 s−1). The equipment consists of an electromagnetic actuator, a fixed housing containing two flat compression platens, a translating cam and a follower. The electromagnetic actuator makes possible reaching high strain rates with a very precise control of the impact velocity and of the energy transmitted to the translating cam. The cam profile enables compression testing to be performed under the strain rate vs. strain loading paths that are commonly found in manufacturing in order to meet the machine-tool and process combined specifications. Special emphasis is placed on the adequacy of the proposed electromagnetic cam drive compression testing equipment to characterize material behaviour in orthogonal metal cutting because non-proportional loading paths during metal cutting are known to have significant influence on the material stress response. The flow curves obtained by means of the equipment are implemented in a finite element computer program and applied in the numerical simulation of orthogonal metal cutting under different cutting velocities. 相似文献
18.
A damage model for carbon–carbon orthotropic composite materials is introduced with a special attention to the thermo-mechanical effects. The internal variables of damage are identified from tension–compression tests according to each fiber direction and from shear tests in each orthotropy plane. The influence of the temperature is taken into account from typical experimental stress–strain curves given for different values of the temperature. The finite element model was implemented in ABAQUS® using an implicit time incremental scheme. Finally, a significant numerical simulation of a thermo-mechanical loading with damage is presented. 相似文献
19.
A new experimental technique has been developed for the performance of high temperature, high-strain-rate experiments in the compression Kolsky bar (split-Hopkinson pressure bar or SHPB). The new technique (referred to as the High-Temperature Compression Kolsky Bar or HTCKB) uses an infra-red spot-heater to rapidly heat the specimen to the desired temperature, a!nd an electropneumatic actuation system to minimize the development of temperature gradients in the sample. The technique is cheap and relatively easy to implement and yet provides accurate, repeatable results. As an illustration of the application of the technique, we have examined the high-temperature response of the BCC metal vanadium at high-strain rates. Stress–strain curves are obtained for the material at strain rates of 4 × 103 s−1 and at temperatures ranging from 300 to 1100 K (27–800°C). Quasistatic (10−3 s−1) experiments have also been performed on vanadium over a slightly smaller range of temperatures, and the results are compared with the new high-temperature, high-strain-rate data. It is observed that the rate of thermal softening is a function of the strain rate. These results illustrate the importance of including the coupling between temperature and strain r!ate in thermoviscoplastic constitutive models. 相似文献
20.
A. P. Bol'shakov A. S. Girin S. A. Novikov V. A. Pushkov V. A. Sinitsyn 《Journal of Applied Mechanics and Technical Physics》1999,40(6):1173-1179
Systematic results from studies of dynamic diagrams of uniaxial compression and tension of uranium-238 and its alloy with
molybdenum at various strain rates and temperatures are presented. The data allow one to plot stress curves versus strain,
strain rate, and temperature for uniaxial compression-tension and to develop mathematical models describing the behavior of
materials under various loading conditions most completely.
All-Russia Research Institute of Experimental Physics, Sarov 607190. Translated from Prikladnaya Mekhanika i Tekhnicheskaya
Fizika, Vol. 40, No. 6, pp. 197–203, November–December, 1999. 相似文献