共查询到20条相似文献,搜索用时 15 毫秒
1.
Experiments have been performed to examine the ductility of Zircaloy 4 cladding tubes under conditions of near plane-strain deformation in the hoop direction (transverse to the tube axis) at temperatures of 25 and 300°C and at strain rates of 10−3 and 102 s−1. To conduct these experiments, a specimen configuration was designed in which near plane-strain deformation is achieved, and a test methodology was established to determine two failure conditions: the limit strain at the onset of localized necking and the fracture strain. Experiments performed on cold-worked stress relieved material using the transverse plane-strain specimen geometry indicate major differences in failure behavior from that observed in uniaxial tension, although both test conditions result in failure by a localized necking process. The experimental results also indicate that while plane-strain fracture strains increase with temperature between 25 and 300°C, at a given temperature they are insensitive to strain rate. The limit strains at localized necking also increase with temperature but only at the high 102 s−1 strain rate. Finally, the failure data indicate a strong sensitivity to surface flaws, as predicted by localized necking theory. 相似文献
2.
《Journal of Nuclear Materials》1986,139(3):191-197
The effect of iodine on the mechanical properties of unirradiated recrystallized ZrNb 1 tubing at 350°C was studied by means of the ring tension test. At strain rates < 10−3/s iodine leads to a substantial decrease in the totale elongation and the reduction of area, but does neither change the 0.2% yield stress, the ultimate tensile stress nor the uniform elongation. The results indicate that iodine induced crack formation in unirradiated recrystallized ZrNb 1 occurs only in the necking region after marked plastic deformation. 相似文献
3.
《Journal of Nuclear Materials》2003,312(2-3):257-261
The influence of tensile specimen geometry on the deformation behavior of flat Zircaloy-4 tensile specimens has been examined for gauge length-to-width ratios that range from 1:1 to 4:1. Specimen geometry has only minor effects on the values of the yield stress, tensile strength, apparent uniform strain at maximum load, and strain-hardening exponent. However, in all geometries but the 4:1 configuration, diffuse necking occurs before maximum load. As a result, strain distributions at maximum load are uniform only in the 4:1 geometry. The elongation to failure is also affected by specimen geometry with the shorter gauge sections exhibiting much higher total elongation values, due in large part to the concomitant specimen necking behavior. 相似文献
4.
对不同厚度国产A508-3钢小尺寸拉伸样品进行了室温拉伸试验,分析了拉伸性能及颈缩段参数,并基于有限元逆运算构建了小尺寸拉伸样品拉伸过程的GTN(Gurson-Tvergaard-Needleman)细观损伤模型,研究了厚度对小尺寸拉伸样品拉伸颈缩行为的影响规律与机理。试验结果表明,小尺寸拉伸样品在变形过程中发生了弹性变形、均匀塑性变形和颈缩变形;随着样品厚度由0.75 mm降低至0.30 mm,屈服强度、抗拉强度和均匀延伸率无明显变化,非均匀延伸率及总延伸率逐渐降低,颈缩角逐渐增大,断裂角在厚度降低至0.50 mm后逐渐增大。GTN细观损伤模型中用于表征空洞形核和融合率的参数在0.30 mm样品中明显降低,此结果与小尺寸拉伸样品颈缩行为规律相互印证。 相似文献
5.
6.
7.
A. Haupt D. Munz W. Scheibe B. Schinke R. Schmitt V. Sklenicka 《Nuclear Engineering and Design》1996,162(1):13-20
Creep tests at constant stress and low cycle fatigue (LCF) tests were performed with a view to investigating and modelling the deformation behaviour of AISI 316 L(N) austenitic stainless steel at 700 °C. All experiments were done on samples taken from two different sheets of the same batch of material.The creep stresses were selected from the high stress range. The results obtained from creep tests on samples from different sheets are compared with each other. The differences between them and the results of a creep test carried out at constant load are indicated.The LCF experiments were strain controlled. The effects of strain rate and strain amplitude on the cyclic hardening behaviour were investigated.The parameters of a set of constitutive equations are determined from these data. The quality of the parameter fit is discussed. 相似文献
8.
《Journal of Nuclear Science and Technology》2013,50(11):848-856
Both transverse and longitudinal Zircaloy-2 specimens irradiated up to 1.2 × 1020 n/cm2 (E> 1 MeV) were tested in tension with strain rates ranging 1.1 × 10-4~1.1 × 10-2 s-1 in the temperature range 200~400°C. Detailed observations of the specimen wall surface and microstructure were also made on samples deformed to various amounts of plastic strain, with a projector and an optical microscope. It was found that localized plastic deformation bands occurred in the temperature range approximately 280~330°C during straining to the ultimate tensile stress. Results also showed that the strain rate dependence of tensile properties, particularly the strain to the ultimate tensile stress, was associated with changes in the number and width of the localized deformation band with strain rates at a temperature of 300°C at which localized bands occurred. From a break of the straight line tracing the true stress-true plastic strain relationship, it was established that the onset stress and strain of the localized deformation band could be estimated. The effect of specimen orientation on localized deformation band was also discussed on the basis of differences in the onset stress and strain between the transverse and longitudinal specimens. 相似文献
9.
Localized deformation has emerged as a potential factor in irradiation-assisted stress corrosion cracking of austenitic stainless steels in LWR environments and the irradiated microstructure may be a critical factor in controlling the degree of localized deformation. Seven austenitic alloys with various compositions were irradiated using 2-3 MeV protons to doses of 1 and 5 dpa at 360 °C. The irradiated microstructure consisting of dislocation loops and voids was characterized using transmission electron microscopy. The degree of localized deformation was characterized using atomic force microscopy on the deformed samples after conducting constant extension rate tension tests to 1% and 3% strain in argon. Localized deformation was found to be dependent on the irradiated microstructure and to correlate with hardening originating from dislocation loops. Dislocation loops enhance the formation of dislocation channels and localize deformation into existing channels. On the contrast, voids mitigate the degree of localized deformation. The degree of localized deformation decreases with SFE with the exception of alloy B. Localized deformation was found to have similar dependence on SFE as loop density suggesting that SFE affects localized deformation by altering irradiated microstructure. 相似文献
10.
It is well known and has been shown qualitatively and quantitatively that the necking phenomenon in uniaxial tensile ductile metal specimens is caused by the presence of non-uniformities in the initial geometry and initial strength. It is shown in this paper that a uniaxial true stress-true strain curve for an idealized perfect specimen could be constructed from experimental data which is available for uniaxial tensile tests on ductile metal specimens having a known initial non-uniformity. 相似文献
11.
《Journal of Nuclear Science and Technology》2013,50(5):359-369
The effect of neutron irradiation on the tensile deformation behavior of zirconium was examined at room temperature at various strain rates ranging of 2.2×10?4~2.2× 10?2 sec?1. The microstructure of the deformed specimens was observed by transmission electron microscopy. It was established that neutron irradiation diminishes the uniform elongation and the strain hardening rate, and hastens the onset of plastic instability. These phenomena are attributed to inhomogeneous deformation in the dislocation channels in the irradiated and deformed zirconium. From the relation between strain rate and tensile properties (yield stress, ultimate tensile stress, uniform elongation and strain hardening rate), it was established that in unirradiated zirconium deformation is controlled by slip at strain rates below 6×10?3 sec?1, while above this threshold, twinning as well as slip contribute to deformation. Neutron irradiation markedly inhibits deformation twinning in zirconium at room temperature. At 77 K, on the other hand, deformation by twinning is more prominent in irradiated specimens. The mechanism of twinning inhibition due to neutron irradiation is discussed. 相似文献
12.
《Journal of Nuclear Science and Technology》2013,50(3):229-238
In-pile experiments of fresh fuel rods under reactivity initiated accident (RIA) conditions have been performed in the Nuclear Safety Research Reactor at the Japan Atomic Energy Research Institute in order to understand the basic pellet cladding mechanical interaction (PCMI) behavior. Rapid fuel pellet expansion due to a power excursion would cause radial and longitudinal deformation of the cladding. This PCMI could be one of the possible incipient failure modes of an embrittled cladding of a high burnup fuel under the RIA conditions. Basic PCMI behavior was studied by measuring cladding deformation of a fresh fuel rod without complicated irradiation effects. The transient elongation measurements of the fuel with two kinds of gap width indicated not only PCMI-induced cladding elongation, but also reduction of the pellet stack displacement by the cladding constraint. In the tests under a high-pressure and high-temperature condition simulating an operation condition of BWRs, additional ridge-type cladding deformation was generated due to the axial collapse of the cladding. A preliminary analysis for interpretation of the tests was made using a computer code for the transient analysis of fuel rods, FRAP-T6. 相似文献
13.
Jin Weon Kim 《Journal of Nuclear Materials》2010,396(1):1-19
This paper describes the temperature dependence of deformation and failure behaviors in the austenitic stainless steels (annealed 304, 316, 316LN, and 20% cold-worked 316LN) in terms of equivalent true stress-true strain curves. The true stress-true strain curves up to the final fracture were calculated from tensile test data obtained at −150 to 450 °C using an iterative finite element method. Analysis was largely focused on the necking and fracture: key parameters such as the strain hardening rate, equivalent fracture stress, fracture strain, and tensile fracture energy were evaluated, and their temperature dependencies were investigated. It was shown that a significantly high strain hardening rate was retained during unstable deformation although overall strain hardening rate beyond the onset of necking was lower than that of the uniform deformation. The fracture stress and energy decreased with temperature up to 200 °C and were nearly saturated as the temperature came close to the maximum test temperature 450 °C. The fracture strain had a maximum at −50 to 20 °C before decreasing with temperature. It was explained that these temperature dependencies of fracture properties were associated with a change in the dominant strain hardening mechanism with test temperature. Also, it was seen that the pre-straining of material has little effect on the strain hardening rate during necking deformation and on fracture properties. 相似文献
14.
《Journal of Nuclear Science and Technology》2013,50(9):660-670
With a view to determining the effects brought by differences in strain rate on the iodine stress corrosion cracking (SCC) of Zircaloy-2 subjected to plane strain tension, constant extension rate tests were conducted at iodine partial pressures of 1–50 Torr and at a temperature of 350°C. The test specimens were machined from actual fuel cladding tube. Lowering the strain rate had the effect of reducing the fracture stress and strain in iodine environment for the tangentially directed specimen. The critical strain rate—below which the severity of SCC rises significantly—was found to be 7×10?3 min?1, about 3.5 times the value of 2×10?3min?1 obtained previously in uniaxial tension tests. The fracture ductility in gaseous iodine varied substantially with the stress condition: A stress ratio a (axial/tangential stress) lying between 0.5 and 0.7 was found to give maximum iodine embrittlement. The fracture stresses obtained at strain rates below critical were found quite close to the threshold stresses for causing SCC obtained in conventional pressurized tube tests. 相似文献
15.
C. Liu 《Journal of Nuclear Materials》2004,335(1):77-82
About 380 μm thick specimens of low-activation martensitic stainless steel EUROFER97 were homogeneously implanted with protons below about 70 °C to concentrations up to about 1200 appm. Tensile tests were performed at 25 and 200 °C. The tests at 25 °C showed an increase of yield stress and ultimate tensile strength and a decrease of uniform elongation and elongation to fracture, while effects at 200 °C were strongly reduced. Scanning electron microscopy showed virtually no change of the ductile, transgranular fracture mode by the implanted H. A slight decrease of necking was observed only at the highest concentrations. The results are compared to previous measurements on F82H-mod and to literature results on tensile tests after He implantation and neutron irradiation. F82H-mod specimens were also implanted under applied tensile stress to concentrations up to 1900 appm. Straining was ascribed to accumulation of atomic defects, but no fracturing occurred. Thermal desorption measurements are included on H-implanted and tensile tested F82H-mod specimens. The results show significant data scatter, even within one specimen, with the highest measured values being in accordance with the implanted amount. In general, the H content is decreased after testing at higher temperatures, but even after testing at 350 °C, some specimens contain significant amounts. 相似文献
16.
Jin Weon Kim 《Journal of Nuclear Materials》2010,396(1):10-19
Irradiation effects on the stable and unstable deformation and fracture behavior of austenitic stainless steels (SSs) have been studied in detail based on the equivalent true stress versus true strain curves. An iterative finite element simulation technique was used to obtain the equivalent true stress-true strain data from experimental tensile curves. The simulation result showed that the austenitic stainless steels retained high strain hardening rate during unstable deformation even after significant irradiation. The strain hardening rate was independent of irradiation dose up to the initiation of a localized necking. Similarly, the equivalent fracture stress was nearly independent of dose before the damage (embrittlement) mechanism changed. The fracture strain and tensile fracture energy decreased with dose mostly in the low dose range <∼2 dpa and reached nearly saturation values at higher doses. It was also found that the fracture properties for EC316LN SS were less sensitive to irradiation than those for 316 SS, although their uniform tensile properties showed almost the same dose dependencies. It was confirmed that the dose dependence of tensile fracture properties evaluated by the linear approximation model for nominal stress was accurate enough for practical use without elaborate calculations. 相似文献
17.
本工作试验研究20~700℃、不同应变加载速率下N18锆合金的单轴拉伸和应力松弛性能。结果表明,N18合金的单轴拉伸应力-应变曲线出现明显的屈服拐点,且温度低于500℃时呈现后继屈服强化,高于500℃后又呈后继屈服软化。除横向试样的断面收缩率高于轧向试样外,试样取向对N18合金的单轴性能影响不大。温度低于300℃时,N18合金的应变速率敏感性受温度的影响不大;350℃时,N18合金的敏感系数达到最小值,其后,对应变速率的敏感性随着温度的升高逐渐增强。N18合金在不同温度和应变水平下均产生明显的应力松弛。在300℃以内,最大应力松弛程度受温度影响较小,且随应变水平的增大明显降低;在350~550℃范围内,应变水平越高,对应的最大应力松弛程度越大;N18合金的最大松弛程度在350℃附近出现最小值。在350~450℃范围内,N18合金表现出明显的动态应变时效特性。 相似文献
18.
19.
An incremental stress-strain law for describing the nonlinear, compressible and asymmetric behavior of graphite under tension and compression as well as complex loadings is derived based on a dry friction model in the theory of plasticity. Stress-strain relations are defined by longitudinal-lateral strain measurements for specimens under uniaxial tension-compression. Agreements with experimentally determined curves from biaxial loading experiments are shown. Agreements in finite element computations using the present model with strain measurements for diametral compression and 4-point bend tests of graphite are also obtained. 相似文献
20.
《Packaging, Transport, Storage and Security of Radioactive Material》2013,24(2-3):109-119
AbstractAluminium honeycombs have been extensively used as impact limiters in nuclear waste transport casks. The mechanical behaviour of these shock absorbing materials was studied to develop an extensive experimental database. A series of tests were performed along various loading paths. Different densities of aluminium honeycombs were tested in different orientations. Static tests included uniaxial tension, uniaxial compression and torsion. Dynamic tests were conducted at different strain rates of up to 100 S?1, to generate experimental data relevant to accident situations. Dynamic studies included the effects of specimen size and confinement. The purpose of using different loading paths was to generate an extensive experimental database which may also be used to develop constitutive models for these materials. Design charts were constructed which can be accessed by various cask designers to optimise and economise on cask development. 相似文献