Power to the people or regulatory ratcheting? Explaining the success (or failure) of attempts to site commercial US nuclear power plants: 1954–1996

Between 1954 and 1996, more than 200 nuclear power projects were publicly announced in the USA. Barely half of these projects were completed and generated power commercially. Existing research has highlighted a number of potential explanations for the varying siting outcomes of these projects, including contentious political protests, socioeconomic and political conditions within potential host communities, regulatory changes (‘ratcheting’), and cost overruns. However, questions remain about which of these factors, if any, had an impact on these outcomes. This article uses a new data set of 228 host communities where siting was attempted to illuminate the factors that led projects towards either completion or cancelation. Controlling for factors highlighted by past studies, we find that regulatory, site‐ and reactor‐specific factors predict the outcomes of attempts to site nuclear reactors over this time period. These findings have important implications in the post‐Fukushima ‘nuclear renaissance’ era when many still hope to revitalize the nuclear industry in the USA. Copyright © 2016 John Wiley & Sons, Ltd.     

镭射BOPP基膜循环拉伸力学性能的试验研究

目的 为研究双向拉伸聚丙烯（Biaxially Oriented Polypropylene,BOPP）薄膜在重复拉伸使用后的弹性模量变化以及应变变化趋势。方法 以26μm BOPP薄膜为研究对象,以1、1.5、2、2.5、3、3.5、4N为最大加载力分别进行加载周期为15次的单轴循环拉伸试验,总结对比循环次数以及加载力对弹性模量及棘轮应变的影响,分析薄膜性能变化趋势。结果 通过对比同一加载应力不同循环下的弹性模量以及棘轮应变,发现在预设加载力下随着循环次数增加,薄膜弹性模量呈增大趋势,且增大幅度逐渐减小,其棘轮应变与弹性模量变化趋势一致;通过取均值对比不同加载力下的弹性模量以及棘轮应变变化,发现薄膜弹性模量随加载力增大而先增大后减小,最大应变以及最小应变均随加载力的增加而增大。结论 通过试验研究得出了BOPP薄膜在循环拉伸中弹性模量及棘轮应变随加载力、循环次数增大的变化趋势;对薄膜性能变化有了一定的预测,并为实际加工中的张力选择提供了指导性建议。     

轴向移动温差作用下焦炭塔筒体循环塑性分析

对焦炭塔材料15Cr Mo R在20℃、200℃、300℃及400℃下进行单轴拉伸试验与单轴棘轮效应试验,利用OW-II随动强化模型对材料的棘轮应变进行预测,模型能较好地预测材料稳定段的棘轮应变率。运用动态坐标系法对焦炭塔进油及进水两种工况进行瞬态温度场分析,确定轴向移动温差及其特征量,为焦炭塔循环塑性分析确定简化的温差特征载荷。对焦炭塔筒体进油生焦及进水冷焦两种工况进行循环塑性分析,发现进油及进水轴向温差渐变范围下对齐时结构具有更大的棘轮应变率,内压循环的同时作用会增大结构的棘轮应变。通过参数化计算,确定焦炭塔结构的棘轮边界,当进水轴向温差高度较小时棘轮边界受内压循环的影响较大。     

15CrMo钢的蠕变-疲劳试验及蠕变回复行为

试验测试了500℃时峰值保持时间分别为0,2,5,10和20 min条件下15CrMo钢的蠕变疲劳性能,重点分析了材料在蠕变疲劳载荷下的变形行为和蠕变回复行为。结果表明,随着峰值保持时间的延长,材料的蠕变-棘轮总变形显著增加;当疲劳-蠕变存在峰值保持时间时,前一个循环中峰值保持结束时的应变值大于再次加载达到峰值时的应变值,存在一定的蠕变回复行为;峰值保持时间越长,15CrMo钢蠕变应变回复量越大,且相同保持时间下的蠕变应变回复量总体上保持恒定。     

核电站管道棘轮特性的试验模拟研究

棘轮效应是工程实际中需要考虑的一个重要问题,棘轮变形问题给核电站管道的安全设计带来了严峻的挑战,它的危害性已经引起了国内外学者的广泛重视,已经成为研究的热点方向.文章利用电液伺服疲劳试验机配以自行设计的三点弯曲辅助设备,对核电站用管道进行三点弯曲的棘轮变形测试,进而研究内压管道的棘轮变形特性.     

An Assessment of Nonlinearly Viscoelastic Constitutive Models for Cyclic Loading: The Effect of a General Loading/Unloading Rule

Predicting the unloading and/or cyclic deformation behavior of polymers is a challenge for most nonlinear viscoelastic constitutive models. Experimental data of an epoxy polymer under uniaxial loading/unloading and two other types of cyclic loadings are used to assess the predictive capabilities of three types of nonlinear viscoelastic models. A general loading/unloading criterion and a switching rule, proposed recently by the authors, are further modified and incorporated into each of the three models. For each model, predictions by both the original formulations and that incorporating the proposed loading/unloading rule are compared with the test data. It is clearly shown that such a rule is essential to correctly simulate the unloading and cyclic loading behavior of polymers. By introducing such a rule to constitutive models, the quantitative predictions can be improved, to various degrees of success, with respect to cyclic deformation features such as ratcheting under cyclic loading with a mean stress and stress relaxation under cyclic straining with a mean strain.     

Particle swarm optimization procedure in determining parameters in Chaboche kinematic hardening model to assess ratcheting under uniaxial and biaxial loading cycles

As parameters in Chaboche model are difficult to be determined from experimental data, a single objective particle swarm optimization procedure was employed to obtain them. Hysteresis loop and uniaxial and biaxial ratcheting simulations were conducted to validate the determined models. Chaboche models determined by particle swarm optimization give more accurate simulation of ratcheting compared with the model determined by trial and error method. Chaboche models containing different backstress components were studied. Models determined considering uniaxial ratcheting can only predict uniaxial ratcheting precisely, while giving very bad simulation of biaxial ratcheting. The linear hardening rule in the N3L1 model clearly decreases the rate of the accumulation of ratcheting strain, and the N3L1 model gives the best simulations. For biaxial ratcheting, the fourth backstress component can decrease the rate of the accumulation apparently, while it has a little influence on prediction of uniaxial ratcheting.     

Numerical and experimental study of ratcheting in cold expanded plate of Al‐alloy 2024‐T3 in double shear lap joints

In this paper strain ratcheting in cold expanded flat plate of Al‐alloy 2024‐T3 in double shear lap joints was studied both experimentally and numerically. In the experimental part, two types of symmetric strain‐controlled and asymmetric stress‐controlled cyclic tests were performed. Also, the cold expanded double shear lap joints subjected to cyclic stress‐controlled tests. The required parameters for simulating the cyclic plastic behaviour of Al‐alloy 2024‐T3 were obtained on the basis of the experimental responses. In the numerical part, a combination of nonlinear isotropic and nonlinear kinematic hardening model (Chaboche) was implemented in the commercial finite element code of ABAQUS, using the subroutine UMAT written in FORTRAN. The results of simulations give an accurate prediction of ratcheting for all types of loading. The obtained results show that increasing the mean stress increases the strain ratcheting. It is clearly shown that the cold expansion process decreases the magnitude of strain ratcheting remarkably compared with “as drilled” specimens and the decrease is bigger for larger cold expansion sizes. Also, it is shown that the middle plane has the highest amount of ratcheting compared to the pin entrance plane and exit plane of the plate hole.     

Application of a semianalytical strain assessment and multiaxial fatigue analysis to compare rolling contact fatigue in twin-disk and full-scale wheel/rail contact conditions

A semianalytical model is introduced to assess rolling contact fatigue problems in railway applications. The constitutive law is based on the nonlinear kinematic and isotropic hardening model of Chaboche–Lemaitre, which allows the cyclic elastoplastic strain under the contact surface to be evaluated. The much higher computational effectiveness in comparison with finite element (FE) analyses is quantified. The Dang Van multiaxial fatigue criterion is implemented to evaluate the rolling contact fatigue in the subsurface elastic region where cracking is relatively rare but more dangerous than surface cracks. The influence of the presence of sulfides in the wheel matrix in decreasing fatigue strength is also assessed by means of Murakami's approach. The model is used to compare conditions under small-scale twin-disk experiments to full-scale wheel/rail contact conditions. It is found that, for the same Hertzian pressure, the small-scale contact is more conservative in that it causes a deeper plasticized layer as compared with the elliptical full-scale contact. In the investigated cases, crack initiation is also not expected according to Dang Van criterion in neither of the studied contact conditions.