TC4 titanium alloy has poor plasticity at room temperature and is a typical difficult-to-form material, so it is limited in its application. The electroplastic effect provides a new idea for the processing of difficult-to-form metals, studying on the electroplastic effect of TC4 titanium alloy under the deforming process is important. This paper explores the influence law of current parameters on the electroplastic effect and mechanical properties of TC4 titanium alloy through room temperature uniaxial tensile test, non-electric heating tension test, and electric heating tension test. Moreover, the constitutive equation of the electroplastic effect of TC4 titanium alloy with coupled temperature and pulse current density was established and verified based on the Johnson–Cook model and Arrhenius equation. The results show that the current duty ratio mainly affects the heating temperature, and the electroplasticity of materials is primarily related to the current density in the range of experimental studies. The tensile strength of TC4 titanium alloy material under the action of pulsed current decreases significantly, and the plasticity increases. High accuracy of the constitutive equation for the electroplasticity of TC4 titanium alloy based on the Johnson–Cook model and the Arrhenius equation.
随着复杂弯曲构件在航空航天等领域的广泛应用,传统弯曲技术无法满足复杂弯管的加工需求,自由弯曲技术因而得到广泛关注.相较于传统弯曲成形技术,自由弯曲技术具有灵活性高、自由程度高、效率高以及可加工复杂弯曲构件的特点.首先从三维自由弯曲技术的基本原理入手,分析了平面弯曲和空间弯曲的工艺阶段;介绍了目前国内外对于自由弯曲阶段的数值解析方程;并对工装模具的结构尺寸和加工工艺参数对成形精度和成形质量的影响进行了分析综述;介绍了对于三维自由弯曲回弹的研究和预测,最后总结了自由弯曲技术目前仍存在的问题和对以后的展望.
To improve the high cycle fatigue performance of metal matrix composites, the laser shock peened surface modification of SiC particles reinforced 2009 aluminum matrix composites（SiCp/2009Al） was used to investigate the high cycle fatigue life of three-point bending, and the evolution laws of residual stress, microhardness, surface morphology and microstructure during laser shock process were revealed. The results show that the high cycle fatigue life of laser shock peened SiCp/2009Al with laser energy of 10,20 and 30 J is significantly improved by 131%, 259% and 182%, respectively, and the corresponding surface residual stress is-127.3,-156.0 and-168.3 MPa, respectively. Laser shock induces deformation pits with depth of about 30 μm on the surface of SiCp/2009Al, the surface microhardness increases from 160 HV of the base metal to 180 HV, and a large number of high density dislocation structures appear. The residual compressive stress and microhardness of metal matrix composite surface are increased obviously, and the increase of fatigue life extension is considerable.
基于超声振动辅助微挤压成形过程摩擦特性表征需求,将超声振动辅助双杯挤压实验拆分为超声振动辅助正杯挤压和反杯挤压两个部分.通过超声振动辅助T2紫铜正杯挤压和反杯挤压的对比成形实验研究了不同超声振动模式辅助微挤压成形过程中试样-模具型腔间的界面摩擦特性,并提出一种量化评价新方法来评估超声振动辅助微挤压成形试样-模具型腔间摩擦应力及摩擦因数的变化规律.结果表明,微挤压成形应力降低值和试样-模具型腔间的摩擦应力降低值都随着超声振幅的增大而增大,且随着工具超声振动、工具-工件复合超声振动和工件超声振动的不同超声振动模式顺序依次增大.
建立了薄板V形自由折弯的有限元模型,利用拉丁超立方抽样法确定了影响折弯回弹的主要因素组合方案,利用有限元模拟的回弹角度作为样本数据,对用于预测折弯回弹角度的BP 神经网络模型进行了训练,采用平均影响值法对影响回弹角度的因素进行了敏感性分析,并利用蒙特卡罗法对折弯过程中的不可控因素进行了模拟,研究了折弯回弹角度的分布规律与变化区间.结果表明,建立的BP神经网络模型精度较高,可以准确预测V形自由折弯回弹角度;受不可控因素影响,折弯回弹角度基本符合正态分布,在置信系数为 99.73%时,角度的波动达 19.87%,表明不可控因素的波动对折弯回弹角度具有显著影响.
