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1.
在Thermecmastor-Z型热模拟试验机上对BT20钛合金进行了变形温度800~1 100℃及应变速率0.001~70 s-1的热模拟压缩实验。以实验数据为基础,运用BP神经网络算法原理,建立了BT20钛合金在高温变形条件下的应力与应变、应变速率和变形温度关系的预测模型,并对模型的泛化能力进行了误差评价。结果表明:通过BP神经网络建立的合金本构关系模型具有较高的预测精度,预测结果的相对误差均在3%以内,能很好地满足实际应用的需求。此外,该模型能够客观、真实地描述BT20钛合金的高温动态变形行为,为材料高温本构关系模型的建立提供了快捷、有效的工具。  相似文献   

2.
一种新型亚稳β钛合金的热变形本构模型   总被引:1,自引:0,他引:1  
基于新型亚稳β钛合金Ti2448在温度范围为1023~1123 K,应变速率范围为63.000~0.001 s-1的等温热压缩流动应力曲线特征,采用经典的应力-位错密度关系式和动态再结晶动力学模型构建了完整描述亚稳β钛合金热变形流动应力与应变、应变速率和变形温度关系的本构模型.位错密度变化方程和Avrami方程被用来分别描述合金在高(≥1s-1)低(<1 s-1)应变速率下呈现的动态回复(DRV)和动态再结晶(DRX)两种不同的变形机制.最终通过应用全局优化求解非线性方程的新方法确定本构模型中的相关参数.根据本文所建模型得到的预测曲线和实验曲线吻合较好,能够有效预测Ti2448在热变形过程中的流动应力,为构建亚稳β钛合金热变形本构模型提供一种有效方法.  相似文献   

3.
为研究风扇/压气机叶片在外来物体冲击载荷下的动态响应,需要建立叶片材料的动态本构模型。风扇/压气机叶片广泛采用TC4钛合金制造,研究建立TC4钛合金的动态本构模型具有重要的工程意义。南京航空航天大学胡绪腾等人基于TC4钛合金的应变率和温度相关单轴应力-应变曲线试验数据,优  相似文献   

4.
利用MATLAB软件建立了反映材料热变形本构关系的神经网络模型,该模型中采用遗传算法优化其权值和阈值提高了网络收敛的稳定性。并采用Themecmastor-Z型热加工模拟试验机上进行的TC11钛合金等温恒应变速率压缩试验获得的试验数据进行训练,建立了TC11钛合金热变形本构关系的BP神经网络模型,并进行了预测,预测误差小于10%。  相似文献   

5.
基于摩擦修正的TB6合金流变应力行为研究及本构模型建立   总被引:1,自引:0,他引:1  
TB6合金是一种高强高韧近β钛合金。采用Gleeble-3500热模拟试验机对铸态TB6钛合金进行了等温热压缩变形试验,变形温度范围为700~900℃,应变速率范围为0.001~1.000 s-1,研究了铸态TB6合金热变形流变应力行为,分析了热压缩后的金相显微组织,基于摩擦修正后的流变应力曲线采用双曲正弦形式的修正Arrhenius关系对TB6钛合金的本构模型进行回归。结果表明:铸态TB6合金的热变形行为对变形温度和应变速率较为敏感,随着变形温度的降低和应变速率的增加流变应力显著增大;其热变形机制以动态回复和动态再结晶为主;得到铸态TB6钛合金热变形本构方程,比较回归模型计算的应力值与实测值其平均相对误差仅为1.48%,因此采用Z参数的双曲正弦函数形式能够较为精确地预测铸态TB6合金高温变形时的流变应力。以上研究为TB6钛合金塑性加工过程的模拟和控制提供了理论基础。  相似文献   

6.
程亮  常辉  樊江昆  唐斌  寇宏超  李金山 《钢铁钒钛》2013,34(1):22-25,40
对新型近β钛合金Ti-7333进行等温压缩试验,并对合金的流变行为进行研究.研究结果表明:Ti-7333的流变应力对变形参数的变化十分敏感,随着温度的升高和应变速率的下降,流变应力显著减小;合金的变形以动态回复为主,动态再结晶为辅.基于Mecking和Bergstrom提出的合金热变形过程中的位错密度演变模型建立了Ti-7333合金的本构模型,准确地描述了合金热变形过程中的流变应力,并且模型中参数数量较少,便于应用.  相似文献   

7.
康荻娜  庞玉华  罗远  孙琦  林鹏程  刘东 《钢铁》2020,55(9):104-110
 为了建立可以满足计算精度的F45MnVS钢高温塑性变形本构关系模型,利用Gleeble-3500试验机完成了热模拟等温压缩试验,获得了变形温度为800~1 000 ℃、应变速率为0.01~10 s-1、变形量为0~70%时的金属流变行为。结果表明,应力随应变的变化具有明显动态再结晶特征,应力随变形温度的降低、应变速率的增加而增大;基于对Arrhenius方程和Zener-Hollomon参数的解析,获得了热变形激活能Q,建立了峰值应力本构模型;基于应力-位错关系和动态再结晶动力学,建立了加工硬化-动态回复和动态再结晶两个阶段的机理型本构模型,用于描述不同变形温度和应变速率时应力与应变之间的关系;采用所建模型完成了不同变形条件的应力应变预测,与试验结果的对比分析表明,相关系数为0.997,吻合度高。  相似文献   

8.
罗远  庞玉华  孙琦  刘峰  王海  刘东 《钢铁研究学报》2020,32(11):977-983
摘要:利用 Gleeble-3500 热模拟实验机完成了07MnNiMoDR钢热等温平面应变压缩实验,获得了温度 900~1100℃、应变速率 0.01~1s-1、变形率45%等条件的高温流变行为,其中温度和应变速率对流变应力的影响明显。基于对Arrhenius 方程和 Zener Hollomon 参数的解析,获得了热变形激活能Q,确定了峰值应力本构模型;通过分析应力应变与位错的关系,获得了硬化率及Z参数等与应力之间的内在关联性,建立了加工硬化 动态回复过程的流变应力模型;基于动态再结晶理论,采用Avrami模型计算了动态再结晶体积分数,获得Z参数计算方法,建立了动态再结晶过程的流变应力模型。利用所建立的本构模型完成了预测及对比分析,相关系数r为0.99,所建立的本构关系模型精度很高。  相似文献   

9.
采用Gleeble-1500D热模拟试验机进行等温压缩实验,研究了ATI 718Plus镍基高温合金在变形温度980~1140℃,应变速率0.001~1.000 s~(-1)条件下的高温流变行为。结果表明:ATI 718Plus高温合金的流变应力随应变速率的降低或变形温度的升高显著降低,其热变形激活能为517.5 kJ·mol~(-1)。同时,该合金的应力应变曲线具有明显的动态再结晶(DRX)特征,变形量、变形温度以及应变速率对动态再结晶体积分数均具有显著影响。此外,以η-Ni_3Al_(0.5)Nb_(0.5)相溶解温度为临界条件构建了718Plus高温合金3个变形阶段的本构模型:以弹性模量为内变量建立了弹性变形阶段的本构模型,基于位错密度演化构建了加工硬化-动态回复阶段本构模型,以再结晶动力学为基础建立了动态再结晶阶段本构模型。建立的本构模型精度较高,相关系数R=0.998,平均相对误差AARE=2.26%,能够较为精确地表征合金的高温变形行为。  相似文献   

10.
《钛工业进展》2018,35(5):24-28
采用电子万能试验机对TC18钛合金进行常温准静态压缩实验,得到该合金在准静态下的实验数据,根据实验数据,选用分离式Hopkinson压杆对TC18钛合金在温度分别为298、523、773、1 023 K,应变率分别为500、1 000、1 500 s~(-1)下进行动态力学性能实验,从而获得TC18钛合金在高温动态压缩条件下的应力-应变曲线,并利用J-C模型对合金在高应变率下的动态塑性本构关系进行拟合,最终建立该合金在高温下的动态塑性本构方程。通过对模型的计算结果分析表明,该模型可以较好地预测TC18钛合金在高温与冲击载荷共同作用下的塑性流变应力。  相似文献   

11.
The dynamic deformation, damage evolution, and cracking in four cast gamma titanium aluminide alloys have been investigated experimentally and theoretically. In this study, the dynamic compressive constitutive properties of several cast TiAl alloys were measured at quasi-static and dynamic rates. Using the measured high-strain-rate constitutive properties, the deformation, damage evolution, and postmortem specimen geometries observed in Taylor cylinder experiments were predicted using the mechanical threshold stress (MTS) constitutive model. The utility of the Taylor impact test for validation of high-rate constitutive models for intermetallics is discussed. This article is based on a presentation given in the symposium “Dynamic Deformation: Constitutive Modeling, Grain Size, and Other Effects: In Honor of Prof. Ronald W. Armstrong,” March 2–6, 2003, at the 2003 TMS/ASM Annual Meeting, San Diego, California, under the auspices of the TMS/ASM Joint Mechanical Behavior of Materials Committe.  相似文献   

12.
Constitutive behavior of tantalum and tantalum-tungsten alloys   总被引:1,自引:0,他引:1  
The effects of strain rate, temperature, and tungsten alloying on the yield stress and the strainhardening behavior of tantalum were investigated. The yield and flow stresses of unalloyed Ta and tantalum-tungsten alloys were found to exhibit very high rate sensitivities, while the hardening rates in Ta and Ta-W alloys were found to be insensitive to strain rate and temperature at lower temperatures or at higher strain rates. This behavior is consistent with the observation that overcoming the intrinsic Peierls stress is shown to be the rate-controlling mechanism in these materials at low temperatures. The dependence of yield stress on temperature and strain rate was found to decrease, while the strain-hardening rate increased with tungsten alloying content. The mechanical threshold stress (MTS) model was adopted to model the stress-strain behavior of unalloyed Ta and the Ta-W alloys. Parameters for the constitutive relations for Ta and the Ta-W alloys were derived for the MTS model, the Johnson—Cook (JC), and the Zerilli-Armstrong (ZA) models. The results of this study substantiate the applicability of these models for describing the high strain-rate deformation of Ta and Ta-W alloys. The JC and ZA models, however, due to their use of a power strain-hardening law, were found to yield constitutive relations for Ta and Ta-W alloys that are strongly dependent on the range of strains for which the models were optimized.  相似文献   

13.
钛合金热变形行为研究   总被引:1,自引:0,他引:1  
综述了国内外钛合金热变形行为的研究进展,分析了几种典型的α钛合金、近α钛合金、α+β钛合金及β钛合金的在不同的热变形条件下的流变应力的行为特征,软化机制,表观激活能及组织演变规律。介绍了氧、氢元素和不同的组织状态对钛合金热变形的影响。  相似文献   

14.
High-temperature mechanical behavior and processing performance of 705X aluminum alloys is examined, employing a combination of mechanical testing, microscopy, and computational modeling. We perform hot uniaxial compression tests over a range of temperatures and strain rates and fit the data to power-law constitutive models. These models are supported and expanded by microscopy and calorimetry, which help to elucidate the operating deformation mechanisms and examine damage evolution. The mechanical behavior constitutive relations are implemented in a finite-element code to simulate the hot rolling process. The results of the rolling simulation are used to predict final product crystallographic texture, which is compared with experimental electron backscattered diffraction measurements for model validation. Finally, we propose a parameter to characterize the development of damage during processing. This work provides a solid foundation for the design of thermomechanical processing of these alloys to maximize yield and optimize process performance.  相似文献   

15.
利用Gleeble-3800热模拟实验机研究了工业纯钛TA2的热变形行为.变形温度为750~1000℃,步长50℃,应变速率分别为0.01、0.1、1和10 s-1.实验结果表明,TA2在热压缩变形过程中发生了加工硬化以及动态回复、动态再结晶.随着变形温度的降低和应变速率的增加,流变应力逐渐增加.为了准确预测TA2的高温流变行为,基于实验数据和双曲正弦Arrhenius模型构建了考虑应变影响的本构方程,本构方程中材料常数α、n、Q、lnA与应变之间存在6阶多项式关系.本文所提出考虑应变影响的本构方程可以用于研究工业纯钛TA2的高温流变行为.   相似文献   

16.
Two constitutive models,the modified Johnson-Cook model and the logarithm linear relation model based on empirical approach and data analysis,were presented to illustrate compressive deformation of magnesium alloys AZ80 under multiple loading directions and strain rates.The results of stress-strain curve analysis and sensitivity index analysis suggested that the stress held large fluctuations in loading direction of 90°.Model testing signified that the logarithm linear relation model was more proper than the modified Johnson-Cook model in view of relative mean square error and correlation coefficients.Moreover,numerical simulation building on established models also indicated that the logarithm linear model is more precise than the modified Johnson-Cook model.  相似文献   

17.
This work focuses on the effect of the second phase on the ambient temperature creep deformation mechanisms of titanium alloys, using Ti-6.0 wt pct Mn and Ti-8.1 wt pct V with Widmanstätten microstructures as the model systems. In Part I it was observed that the presence of a second phase can affect the tensile deformation behavior. Likewise, the creep deformation mechanisms of the two-phase alloys differ from the mechanisms of single-phase alloys. These α-β deformation mechanisms include twinning in fine grains of the α phase and stress-induced hexagonal martensite in the β phase of Ti-8.1 V. This is the first time that twinning in the α phase and stress-induced martensite in the β phase are reported as creep deformation mechanisms in an α-β titanium alloy. Several factors, including elastic interaction effects, shear stress due to deformation products in adjacent phases, and the stability of the β phase, affect the creep deformation mechanisms in these alloys. Models for the time-dependent growth of martensite are suggested. In addition, the difference between tensile and creep deformation in regard to accumulation of stresses to reach the critical stresses is described.  相似文献   

18.
A self-consistent model was applied to predict the plastic flow behavior during hot working of alpha/beta titanium alloys with wrought (equiaxed alpha) microstructures as a function of the flow behavior and volume fractions of the individual phases. For this purpose, constitutive relations that incorporated composition-dependent strength coefficients were determined for the alpha and beta phases. With these constitutive relations and measurements of the specific compositions and volume fractions of the two phases at hot-working temperatures, the flow stress dependence on temperature under nominally isothermal conditions and the (average) strain rates in the individual phases were predicted for Ti-6Al-4V. The effect of temperature transients during hot deformation on the flow stress under nonisothermal (conventional) forging conditions and under nominally isothermal, high strain-rate conditions was also established using the self-consistent modeling approach. In these instances, the effect of a rapid temperature drop or rise, respectively, on the retention of a metastable microstructure was quantified. The predicted flow behaviors showed good agreement with experimental measurements.  相似文献   

19.
钛棒线材短流程制备新技术   总被引:2,自引:0,他引:2  
从钛及钛合金的熔炼、铸造特性、等离子冷床炉的工作原理等方面分析了钛棒坯进行半连续铸造的可能性,从三辊行星轧机的工作原理、材料在变形时的受力状态、钛合金的塑性变形特性等方面对铸造钛棒坯三辊行星轧制可行性进行了分析。指出,真空等离子冷床炉半连续铸造棒坯——三辊行星轧机开坯轧制是一种钛棒线材的高效率、短流程加工新技术,是今后的研究发展方向。  相似文献   

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