基于修正Arrhenius模型和SVR-PSO模型的HNi55-7-4-2合金高温本构模型的对比

采用Gleeble-3500热模拟试验机对HNi55-7-4-2合金进行热压缩实验,研究其高温流变应力行为。通过等温热压缩实验和摩擦修正获得了HNi55-7-4-2合金在温度为600～800℃、应变速率为0.01～10 s~(-1)时的应力-应变曲线。结果表明:HNi55-7-4-2合金的流变应力值与温度、应变速率和变形量之间成非线性关系,流变应力值随着应变率增大而升高,随着变形温度的升高而降低。基于实验数据,分别建立修正Arrhenius本构模型和粒子群算法优化的支持向量机回归模型(SVR-PSO),引入统计学方法对模型的精度进行量化评估:修正Arrhenius模型的平均相对误差和均方根误差分别为6.30%和2.43 MPa,SVR-PSO模型的平均相对误差和均方根误差分别为0.61%和0.28 MPa,SVR-PSO模型预测精度和泛化能力均优于Arrhenius模型。     

热压缩7075铝合金流变应力特征

采用Gleeble-1500热模拟高温压缩变形试验,研究了7075铝合金高温塑性变形时的流变应力行为.结果表明,应变速率和变形温度的变化影响合金稳态流变应力的大小,在变形温度为350～500℃、应变速率为0.01～1 s^-1的条件下,随变形温度升高,流变应力降低;而随应变速率提高,流变应力增大;应变速率和流变应力之间满足指数关系,温度和流变应力之间满足Arrhenius关系,可用Zener-Hollomon参数描述7075铝合金高温塑性变形时的流变应力行为.     

热压缩7075铝合金流变应力特征

采用Gleeble-1500热模拟高温压缩变形试验,研究了7075铝合金高温塑性变形时的流变应力行为。结果表明,应变速率和变形温度的变化影响合金稳态流变应力的大小,在变形温度为350～500℃、应变速率为0.01～1s-1的条件下,随变形温度升高,流变应力降低;而随应变速率提高,流变应力增大;应变速率和流变应力之间满足指数关系,温度和流变应力之间满足Arrhenius关系,可用Zener-Hollomon参数描述7075铝合金高温塑性变形时的流变应力行为。     

5083铝合金的高温压缩变形行为

在Gleeble-3500热模拟实验机上采用高温压缩实验研究了5083铝合金在变形温度为300～500℃、应变速率为0.01～10 s~(-1)、真应变为0～0.9条件下的热变形行为。对高温压缩实验结果进行分析,修正了实验中由于摩擦和变形热效应引起的流变应力误差,得到5083铝合金修正后的真应力-真应变曲线。结果表明:在高温压缩实验过程中,摩擦和变形热效应产生的温升影响不能忽略,摩擦和温升引起应力变化的最大值分别为31.78、33.66 MPa;5083铝合金修正后的流变应力随变形温度的升高而降低,随应变速率提高而增大;应力峰值出现后,应力逐渐下降,且呈稳定的流变特性。     

AA7075高强铝合金热冲压流变行为本构模型对比研究

在热冲压过程中,AA7075高强铝合金板料经充分固溶后移入室温模具进行冲压成形并淬火。为表征AA7075铝合金在热冲压工艺中的变形行为,在温度200~480℃、应变速率0.01~10s-1范围内进行了高温拉伸试验。基于Arrhenius类型本构模型、Johnson-Cook模型以及Zerilli-Armstrong模型提出了多种修正本构模型,并应用实验所获流变曲线进行了拟合。提出的修正模型通过将模型参数表示为应变、应变速率及温度相关的多项式函数耦合了应变、应变速率及温度对流变应力的影响,并通过均方误差(MSE)以及相关系数R值对模型流变应力预测准确性进行了评价。结果表明,修正的Johnson-Cook模型能够更加准确的预测AA7075高温流变行为。     

2219铝合金高温本构模型及热加工图研究

为研究2219铝合金的高温流变行为及最佳热加工工艺窗口，采用Gleeble-3500热模拟试验机在变形温度为573～773 K和应变速率为0.01～10 s^-1条件下对2219铝合金进行了等温压缩实验，得到了不同应变速率和温度下的真实应力-真实应变曲线。根据2219铝合金流变数据的特性，提出了一种新的本构模型，并将其与经典模型的预测精度进行了对比。此外，利用构建的新本构模型推导出了2219铝合金的热加工图解析计算公式，并绘制了其热加工图。结果表明，2219铝合金是一种温度和应变速率高度敏感材料，其高温本构关系必须考虑温度和应变速率的影响。在低温下，Arrhenius模型和Hensel-Spittle模型的预测精度较低，尤其在573和623 K温度下，其预测结果与实验数据存在较大误差。相比之下，新模型在不同温度和应变速率下的预测精度误差较小，并且明显优于Arrhenius模型和Hensel-Spittle模型。这是因为新模型在lnσ和■之间采用了3阶精度逼近，而Arrhenius模型和Hensel-Spittle模型只采用了1阶精度逼近。通过采用更高阶的逼近方法，新...     

轻轨用55Q钢的高温流变应力本构模型

通过Gleeble-3800热模拟实验机,在应变速率为0.1～20 s^-1、变形温度为900～1200℃的条件下对轻轨用55Q钢进行轴向单道次压缩实验,得到55Q钢的真应力-真应变曲线,并分析研究了不同热加工条件对55Q钢高温流变应力的影响。实验结果表明：在相同变形温度下,低应变速率时的流变应力较低,在相同应变速率下,高温时的流变应力较低,说明低应变速率和高温有利于动态软化。对流变应力、应变速率和变形温度之间的关系进行线性拟合,建立了55Q钢的修正Johnson-Cook本构模型和基于应变补偿的Arrhenius本构模型,对比两种模型发现,基于应变补偿的Arrhenius本构模型的预测精度更高,能够较好地揭示55Q钢的热变形特性。     

选区激光熔化GH3536高温合金高温本构模型北大核心CSCD

为研究选区激光熔化高温合金在高温下的塑性变形行为,对选区激光熔化制备的热等静压态GH3536高温合金进行热模拟压缩试验,获得了不同变形条件(变形温度为900、950、1000和1050℃;应变速率为0.01、0.1、1和10 s^(-1))下的高温真应力-真应变曲线,研究了该材料在高温条件下的载荷响应规律,并建立了基于Arrhenius方程的材料高温本构模型。研究发现,峰值应力随着应变速率的升高而升高,随着变形温度的升高而降低,最大峰值应力为592.8 MPa。基于Arrhenius方程建立了HIP状态下GH3536高温合金的高温本构方程,其预测精度的平均相对误差(AARE)为9.42%。通过组织观察发现,在高温变形过程中合金的组织被拉长,材料中有明显发生动态再结晶的迹象。     

铸态GH4169合金热变形行为及三种本构模型对比

在Gleeble-1500热力模拟机上对铸态GH4169合金进行热压缩试验,变形参数为:温度(1193～1373K)、应变速率(0.01～10s~(-1))、变形量50%。通过分析真应力真应变曲线,研究铸态GH4169合金的热变形行为;对比分析了Johnson-Cook(JC)、修正的Johnson-Cook(MJC)和应变补偿Arrhenius3种本构模型的相关系数(R)和平均相对误差(AARE)。结果表明:铸态GH4169合金的流变应力随变形温度的升高和应变速率的降低而减小。JC模型、MJC模型和应变补偿的Arrhenius本构模型的相关系数(R)分别为0.891、0.956和0.961,AARE依次为29.02%、11.16%和9.31%。因此,应变补偿的Arrhenius模型能够更为精确地描述铸态GH4169的热变形行为。     

A356铝合金的高温流变行为及本构模型研究

A356铝合金的高温流变特性和本构模型对其应力状态起着重要的作用，为铝合金流变成形过程的有限元模拟奠定了重要的基础。从A356铝合金轮毂铸造坯料上制取拉伸试样，利用Instron 3369型实验机进行等温拉伸实验，实验温度为300～375℃,应变速率为0.001～0.1 s^-1。由此得到的真应力-真应变曲线表明，温度和应变速率等热力学条件对材料的流变应力的影响显著。基于真应力-真应变曲线，建立了基于位错密度理论的物理模型来表征不同热力学条件下的流变应力。将模型预测值与实验值进行对比，并进行误差分析。结果表明，所建立的物理模型能够较准确地预测A356铝合金的高温拉伸流变行为。     

The high temperature flow behavior modeling of NiTi shape memory alloy employing phenomenological and physical based constitutive models: A comparative study

The present study was conducted to examine the constitutive behavior of a near equiatomic Nickel Titanium shape memory alloy through modified Zerilli–Armstrong and Arrhenius type models. The acquired flow stress data from isothermal hot compression tests in a temperature range of 700–1100 °C and under the strain rates of 0.001–0.1 s⁻¹ was employed to calculate the material constants thereby properly establishing the corresponding constitutive equations. Furthermore, a comparative study has been made on the capability of the aforementioned models to predict the high temperature flow behavior of the adapted shape memory alloy. This was performed by comparing the prediction relative errors, average absolute relative error and correlation coefficient. The results show that Arrhenius type equation predicts the flow behavior more accurately than the Zerilli–Armstrong one. However, the latter requires lesser material constants and running time to be established.     

Ti-48Al-2Nb-2Cr合金热变形行为及本构关系研究

采用Gleeble-1500热力模拟机对铸态Ti-48Al-2Nb-2Cr合金进行高温变形热压缩试验,变形温度范围为1050~1200℃,应变速率范围为0.001~0.1s^-1,压缩变形量为60%。研究该合金高温变形温度和应变速率与流变应力之间的关系,计算了合金激活能,并建立了Ti-48Al-2Nb-2Cr合金的Arrhenius本构模型和多元线性回归的本构模型。结果表明,该合金的激活能随温度升高和应变速率增大而增大;Arrhenius本构模型的相关系数为0.98228,平均相对误差为9.97%,相对误差在10%以内的点只占62.0%;而采用多元线性回归本构模型的相关系数为0.99566,平均相对误差为4.76%,相对误差在10%以内的点占92.6%,本构精度较高。     

Constitutive modeling of compression behavior of TC4 tube based on modified Arrhenius and artificial neural network models

Warm rotary draw bending provides a feasible method to form the large-diameter thin-walled(LDTW)TC4 bent tubes, which are widely used in the pneumatic system of aircrafts. An accurate prediction of flow behavior of TC4 tubes considering the couple effects of temperature,strain rate and strain is critical for understanding the deformation behavior of metals and optimizing the processing parameters in warm rotary draw bending of TC4 tubes. In this study, isothermal compression tests of TC4 tube alloy were performed from 573 to 873 K with an interval of 100 K and strain rates of 0.001, 0.010 and0.100 s~(-1). The prediction of flow behavior was done using two constitutive models, namely modified Arrhenius model and artificial neural network(ANN) model. The predictions of these constitutive models were compared using statistical measures like correlation coefficient(R), average absolute relative error(AARE) and its variation with the deformation parameters(temperature, strain rate and strain). Analysis of statistical measures reveals that the two models show high predicted accuracy in terms of R and AARE. Comparatively speaking, the ANN model presents higher predicted accuracy than the modified Arrhenius model. In addition, the predicted accuracy of ANN model presents high stability at the whole deformation parameter ranges, whereas the predictability of the modified Arrhenius model has some fluctuation at different deformation conditions. It presents higher predicted accuracy at temperatures of 573–773 K, strain rates of 0.010–0.100 s~(-1)and strain of 0.04–0.32, while low accuracy at temperature of 873 K, strain rates of 0.001 s~(-1)and strain of 0.36–0.48.Thus, the application of modified Arrhenius model is limited by its relatively low predicted accuracy at some deformation conditions, while the ANN model presents very high predicted accuracy at all deformation conditions,which can be used to study the compression behavior of TC4 tube at the temperature range of 573–873 K and the strain rate of 0.001–0.100 s~(-1). It can provide guideline for the design of processing parameters in warm rotary draw bending of LDTW TC4 tubes.     

Incoloy825合金热变形过程中的本构模型和特殊晶界演变

采用原始JC模型、修正JC模型和应变补偿Arrhenius方程，描述了Incoloy825合金在不同温度（950～1150 °C）和应变速率（1~10 s^-1）下经摩擦和温升修正后的应力-应变曲线。结果表明，修正后曲线具有明显的动态再结晶特征。与原始JC模型和修正的JC模型相比，Arrhenius应变补偿模型更适合于描述Incoloy825合金热变形过程中的应力应变行为。温度和应变速率对特殊晶界的演变有显著影响。特殊晶界长度分数与动态再结晶分数呈正相关。与冷轧后退火处理工艺相比，热变形工艺调控的特殊晶界长度分数较低，热变形工艺不适合用来调整特殊晶界分数，其原因是在热变形过程中动态再结晶的大量形核造成较小的晶粒团簇。     

Flow behavior of Al–6.2Zn–0.70Mg–0.30Mn–0.17Zr alloy during hot compressive deformation based on Arrhenius and ANN models

The hot deformation behavior of Al–6.2Zn–0.70Mg–0.30Mn–0.17Zr alloy was investigated by isothermal compression test on a Gleeble–3500 machine in the deformation temperature range between 623 and 773 K and the strain rate range between 0.01 and 20 s^?1. The results show that the flow stress decreases with decreasing strain rate and increasing deformation temperature. Based on the experimental results, Arrhenius constitutive equations and artificial neural network (ANN) model were established to investigate the flow behavior of the alloy. The calculated results show that the influence of strain on material constants can be represented by a 6th-order polynomial function. The ANN model with 16 neurons in hidden layer possesses perfect performance prediction of the flow stress. The predictabilities of the two established models are different. The errors of results calculated by ANN model were more centralized and the mean absolute error corresponding to Arrhenius constitutive equations and ANN model are 3.49% and 1.03%, respectively. In predicting the flow stress of experimental aluminum alloy, the ANN model has a better predictability and greater efficiency than Arrhenius constitutive equations.     

Constitutive modeling of flow behavior of precipitation-hardened AA7022-T6 aluminum alloy at elevated temperature

The thermomechanical behavior of precipitation-hardened aluminum alloy AA7022-T6 was studied using isothermal compression at temperatures of 623−773 K and strain rates of 0.01−1 s⁻¹. The experimental results indicated that dynamic recrystallization (DRX) is a predominant hot deformation mechanism, especially at elevated temperatures and low strain rates. The modified Johnson−Cook (J−C) and the strain compensated Arrhenius-type models were developed to predict the hot flow behavior under different deformation conditions. The correlation coefficients of modified J−C model and the strain compensated Arrhenius-type models were 0.9914 and 0.9972, respectively, their average relative errors (ARE) were 6.074% and 4.465%, respectively, and their root mean square errors (RMSE) were 10.611 and 1.665 MPa, respectively, indicating that the strain compensated Arrhenius-type model can predict the hot flow stress of AA7022-T6 aluminum alloy with an appropriate accuracy.     

基于应变补偿TC4-DT钛合金高温变形本构模型

通过TC4-DT钛合金在1181~1341 K,0.01~10 s~(-1)条件下热模拟压缩试验,得到其在不同条件下高温变形真应力-真应变曲线。采用回归分析和多项式拟合建立了应变补偿高温变形本构方程。结果表明:各变形条件下的流变应力曲线均呈现应变硬化和流动软化,低温高应变速率特征更明显。当应变速率低于1 s~(-1)时,预测值与实验值吻合程度较高,相关系数和平均相对误差绝对值分别为0.9952和5.78%,此修正模型可作为TC4-DT钛合金高温变形本构方程。     

变形态Ti40合金的高温流变应力模型研究

利用变形态Ti40合金在变形温度范围为1223～1323K和应变速率范围为0.001～1.0s-1的不同应变下的热压缩实验数据研究了该材料的高温流变应力模型。利用实验数据分析了Arrhenius型方程对变形态Ti40合金的适用性,结果表明,采用双曲正弦型Arrhenius方程建立该材料的高温流变应力模型是适宜的,并通过对双曲正弦方程进行温度补偿及引入路径变量因子改进了模型。通过计算复相关系数和平均相对误差绝对值对该模型进行误差分析,经过改进的变形态Ti40合金的高温流变应力模型具有良好的精度。