基于Mooney-Rivlin模型的船用密封圈设计及试验验证

基于橡胶试样单轴拉伸试验得到的拉力和变形量等试验数据，利用最小二乘法拟合求得橡胶材料的Mooney-Rivlin模型及Yeoh模型常数。基于有限元方法，用得到的模型常数对试样变形量进行计算并与试验结果对比。结果表明，Mooney-Rivlin模型在小应变和中等应变时可以较好地描述材料的力学行为，Yeoh模型适合模拟大应变时材料的力学行为。利用得到的模型常数计算分析异形密封圈的静态性能，最大变形量计算值与试验值的相对误差为2.74%，表明了所选模型常数的准确性。     

基于Mooney-Rivlin模型和Yeoh模型的超弹性橡胶材料有限元分析

介绍橡胶材料两种常用的应变能密度函数模型--Mooney-Rivlin模型和Yeoh模型,并解析求得其材料常数.采用ANSYS有限元分析软件,分析比较两种模型的位移和应力云图,验证其适用性,即Mooney-Rivlin模型适合模拟中小变形行为;Yeoh模型适合模拟炭黑填充NR的大变形行为.     

油浸式电抗器用阻尼橡胶材料压缩阻尼特性与本构模型

通过对油浸式电抗器器身-油箱间阻尼橡胶材料进行轴向压缩滞回性能试验,研究了其阻尼特性;依据实验数据并结合ABAQUS数值模拟结果,校正了适用于油浸式电抗器器身-油箱间阻尼橡胶材料的Mooney-Rivlin和Yeoh本构模型参数。结果表明,相比普通抗振橡胶试件,丁腈橡胶试件的轴向压缩刚度更大,滞回曲线更饱满,耗能能力更强;Mooney-Rivlin模型和Yeoh模型均适用于NBR试件的小变形和大变形行为,其中Mooney-Rivlin模型参数和Yeoh模型参数计算结果最大误差分别为-11.31%和-12.21%。     

基于不同本构模型的弹性联轴器刚度特性分析

分别采用Mooney-Rivlin,Odgen和Yeoh橡胶材料本构模型对永磁同步直驱系统用弹性联轴器进行有限元建模和径向刚度仿真计算,并将仿真计算结果与试验结果进行对比。分析得出,采用Mooney-Rivlin和Odgen模型得到的弹性联轴器径向刚度与试验值偏差较大,采用能够模拟大变形的Yeoh模型得到的弹性联轴器径向刚度与试验值偏差较小,Yeoh模型适合用于弹性联轴器及同类产品进行力学性能分析。     

超弹性本构模型在轮胎有限元分析中的应用

对3种主要的超弹性本构模型进行对比,并基于非线性力学理论对轮胎用橡胶材料单轴拉伸力学行为进行测试;假设橡胶为完全不可压缩材料,给出Neo-Hookean,Mooney-Rivlin和Yeoh 3种超弹性本构模型常数的确定方法;在Ansys软件中采用不同的本构模型对轮胎充气状态的力学性能进行分析.结果表明,在轮胎小变形条件下,线弹性模型的模拟结果与实测值比较吻合.     

深冷环境下密封橡胶的力学性能研究

在深冷环境下密封橡胶易发生变脆、丧失高弹性等现象,从而导致密封性能降低。密封橡胶的力学性能是评估密封可靠性的重要参数。选择低苯基硅橡胶及以低苯基硅橡胶为基体分别添加全氟聚醚油和聚酰亚胺粉的改性橡胶为研究对象,考察3种橡胶在超低温下的力学性能,在常温(23℃)和超低温(-196℃)下进行单轴拉伸和压缩永久变形试验,并利用有限元软件Abaqus超弹性材料拟合板块对本构模型进行参数模拟,探讨Mooney-Rivlin模型、Ogden模型和Yeoh模型对超低温下密封橡胶的适用性。结果表明:在超低温下,聚酰亚胺粉改性低苯基硅橡胶的密封性能优于其他两种橡胶材料;在单轴拉伸试验拟合中,Yeoh模型拟合误差较小;在压缩试验拟合中,Mooney-Rivlin模型和Ogden模型能更准确地描述橡胶力学性能。     

Mooney-Rivlin模型对发泡橡胶力学行为的模拟

采用有限元分析软件常用的Mooney-Rivlin模型对NR和NBR闭孔发泡材料单轴拉伸力学行为进行了模拟。结果表明，用Mooney-Rivlin模型模拟所得的闭孔发泡橡胶力学行为与实测数据拟合较好，橡胶泡孔内的气体具有熵弹性及不可压缩且各向同性的特点。     

WH型橡胶隔振器静刚度仿真研究

以WH型橡胶隔振器为研究对象，基于超弹性本构理论，应用Abaqus软件建立橡胶隔振器的有限元模型，计算WH型橡胶隔振器的三向静刚度，并与测试结果进行对比。结果表明：对于WH型橡胶隔振器，横向静刚度的计算应选择单轴拉伸＋等双轴拉伸的应力-应变曲线组合，垂向、纵向静刚度的计算应选择单轴拉伸＋平面拉伸的应力-应变曲线组合；本研究探讨的5种超弹性本构模型中，Mooney-Rivlin模型的计算误差最小，Neo Hooke模型仅在描述剪切变形时精度较高，Ogden模型、Yeoh模型和Van Der Waals模型的计算误差较大。     

橡胶类超弹性本构模型中材料参数的确定

采用单轴拉伸、等双轴拉伸及平面剪切下橡胶材料试验数据的4种不同组合方式分别对主要用于表述橡胶超弹性的Yeoh模型和Ogden三阶模型进行拟合,并得出两种模型的材料参数。建立单轴拉伸、等双轴拉伸及平面剪切试验的有限元模型,探究1种仅仅借助单轴拉伸试验数据并结合其他2种试验有限元模型预测结果,进行橡胶类本构模型参数拟合的新方法。结果表明:选用Yeoh模型时,利用单轴拉伸和等双轴拉伸组合方式可获得较理想的材料参数;在只具备单轴拉伸试验数据的条件下,利用单轴试验数据和等双轴有限元模型预测数据的组合方式在低应变区用Yeoh模型拟合得到的材料参数较可靠;Ogden三阶模型较Yeoh模型精度高,但计算效率低且不易收敛。     

橡胶Mooney-Rivlin模型中材料常数的确定

介绍了在用非线性有限元对橡胶制品进行分析时，橡胶类材料常用Mooney-Rivlin模型中材料常数确定的几种方法。     

Kinetic models analysis

This paper introduces a freeware program for models analysis, which implements a robust method for parameter estimation of nonlinear models, able to detect outliers. A new class of criteria is proposed in order to achieve an optimal experimental design. Finally a strategy for model discrimination is presented. Since this is a critical point, the correct meaning of statistical tests and regions of confidence is proposed. At last, it is explained why it is better to avoid any approach that makes use of probability to discriminate among models.     

On threshold moving-average models

In this paper the class of discrete self-exciting threshold moving-average (SETMA) models is studied in some detail. In particular, we consider various problems associated with the identification, estimation and testing of these models. A simple method for distinguishing between low order moving average (MA) and low order SETMA models is presented. Some simulation results illustrate the performance of the proposed method. We also derive a Lagrange multiplier (LM) test statistic for testing a linear MA model against a SETMA model. The small sample performance of the LM test is evaluated in a Monte Carlo study. A real example is used to illustrate the results.     

Experimental hydrocyclone roping models

Hydrocyclone roping has not been studied and modeled in true grinding circuits. The paper discusses experiments made with a pilot size closed grinding circuit treating 0.5–1.0 t/h crystalline limestone. The equations found in the literature did not all describe roping very well. The best results were obtained by predicting the underflow solids volume flow. Equations based on underflow particle size did not give good results. Roping had mixed effects on the performance of the grinding circuit depending upon how it was obtained. Experiments were made by initiating roping through increasing mill feed rate or decreasing cyclone apex diameter. Varying responses are discussed in the paper. The estimation given in literature, that a circuit has the optimal operational point close to roping, was also confirmed for this set-up.     

Threshold quantile autoregressive models

This article studies estimation and asymptotic properties of Threshold Quantile Autoregressive processes. In particular, we show the consistency of the threshold and slope parameter estimators for each quantile and regime, and derive the asymptotic normality of the slope parameter estimators. A Monte Carlo experiment shows that the standard ordinary least squares estimation method is not able to detect important nonlinearities produced in the quantile process. The empirical study concentrates on modelling the dynamics of the conditional distribution of unemployment growth after the second world war. The results show evidence of important heterogeneity associated with unemployment and strong asymmetric persistence of unemployment growth in the higher quantiles.     

Comparison of color-appearance models

The color-appearance models developed by R. W. G. Hunt (model H) and Y. Nayatoni and his collaborators (model N) are compared. The following color perceptions are analyzed: (1) colorfulness under illuminant C for NCS samples, (2) colorfulness change by changing illuminant C to illuminant A, (3) colorfulness change by changing adaptign illuminance, (4) Helson-Judd effect on achromatic colors under saturated chromatic illuminants, and (5) brightness and lightness. Special features of each model are made clear. In addition, a deatailed discussion is given on the mechanism introbucing the Helson-Judd effect and on the model formulations, especially in model H.     

Empirical colorant mixture models

The color behavior of unconventional colorant systems and certain other mixtures cannot be described adequately by available theory. In such cases alternative approaches to formulation and shading need to be developed. In this article we investigate empirical models using Scheffé polynomials to describe color response surfaces for three- and four-component olorant mixtures. We describe experimental designs that allow the efficient estimation of the coefficients of high-order polynomial models over the full mixture-design space and that also allow estimation of lower-order models over subspace mixture regions. The experimental designs are applied to real colorant systems, and the accuracy of color response prediction from linear, quadratic, cubic, and quartic polynomial models is compared to that of theoretical models. The color response surfaces are visualized by preparing contour plots that depict color variation over a compositional region. These maps allow one to observe the relationship between color and composition, to assess the color gamut available with a given colorant set, and to estimate the formula or adjustments required to match a given color position. The effective use of model predictions to perform a sensitivity analysis on the compositional variables is also demonstrated in the context of manufacturing process control.     

Nonlinear error correction models

The relationship between cointegration and error correction (EC) models is well characterized in a linear context, but the extension to the nonlinear context is still a challenge. Few extensions of the linear framework have been done in the context of nonlinear error correction (NEC) or asymmetric and time varying error correction models. In this paper, we propose a theoretical framework based on the concept of near epoch dependence (NED) that allows us to formally address these issues. In particular, we partially extend the Granger Representation Theorem to the nonlinear case.