共查询到18条相似文献,搜索用时 93 毫秒
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建立1种本构模型,用于研究形状记忆合金(SMA)结构和复合材料的力学响应。首先,该本构模型在单轴应力状态和多轴应力状态下得到考核;其次,给出了移植到ABAQUS的用户子程序umat的求解格式。利用有限元方法分析了SMA的CT(紧凑拉伸)和TPB(三点弯曲)试样以及SMA-纤维增强复合材料和常规金属合金增强SMA基复合材料的力学响应。在CT和TPB裂纹前端,有不同的相变规律,SMA复合材料的相变取决于应力状态和两相材料的材料性质等。 相似文献
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在铸造生产的造型方法中,压实过程作为最终紧实的主要手段之一,在射压、静压等许多主要的现代造型方法中都必须采用。作为最终紧实过程的主要手段之一,对压实过程进行数值模拟仍然是必要的。本文运用土力学中的侧限压缩试验方法测定了型砂的本构关系建立了力学分析的基础,在Ansys软件平台中采用APDL语言进行二次开发编程,对湿砂造型中的压实造型过程进行数值模拟,取得了较好的结果。 相似文献
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NiTi形状记忆合金超弹性的研究进展 总被引:14,自引:0,他引:14
近年来,有关NiTi形状记忆合金的研究取得了很多进展,本文主要介绍了NiTi形状记忆合金超弹性的基础研究、力学行为、在耐磨损性能方面的应用研究以及数学方面的某些进展和重要问题。 相似文献
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60NiTi合金具有强度高、耐磨性好等一系列优异的性能。但由于它难热成型,因此大大限制了在工业领域的广泛应用。为了确定60NiTi合金最优的热加工工艺,研究了铸态60NiTi合金在750~1 050℃,0.01~1 s-1变形速率下的热变形行为,并采用包含Arrhenius项的Z参数法构建了高温变形本构方程。结果显示:仅在1 000℃、1 s-1速率下高温变形时60NiTi合金发生了明显的动态再结晶,温度升高能提高60NiTi合金的热成型性能。在高温(1 050℃)大变形速率下(1 s-1)加工60NiTi合金的热成型性能最好。 相似文献
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NiTi形状记忆合金超弹性的研究进展 总被引:1,自引:0,他引:1
近年来 ,有关NiTi形状记忆合金的研究取得了很多进展 ,本文主要介绍了NiTi形状记忆合金超弹性的基础研究、力学行为、在耐磨损性能方面的应用研究以及数学方面的某些进展和重要问题 相似文献
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TC4钛合金神经网络本构模型及在有限元模拟中应用 总被引:1,自引:0,他引:1
利用Zwick/Roell Z100材料试验机,对TC4钛合金进行等温恒应变速率下的单向拉伸试验。基于获得的试验数据,采用BP神经网络技术建立了该合金的高温本构关系模型,并对其预测性能进行分析。基于ABAQUS/Explcit平台进行材料子程序二次开发,将神经网络本构模型嵌入到有限元计算中,实现了TC4钛合金高温变形的数值模拟。结果表明,神经网络本构模型预测精度很高,可以准确地描述TC4钛合金在热态下的动态力学性能。神经网络本构模型应用于有限元模拟可行且有效。 相似文献
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基于变温度场的镍钛形状记忆合金管滚珠旋压有限元模拟(英文) 总被引:1,自引:0,他引:1
作为一种新的尝试,在高温下应用滚珠旋压制造镍钛形状记忆合金管。将名义成分为Ni50.9Ti49.1(摩尔分数)的镍钛形状记忆合金棒料进行固溶处理,制成用于滚珠旋压的镍钛形状记忆合金管坯。以变温度场和本构方程为基础,用刚粘塑性有限元法来模拟镍钛形状记忆合金管的滚珠旋压,获得了温度场、应力场和应变场,并进行了旋压载荷预测。有限元模拟结果表明,在旋压件的主变形区有大约160℃的温升。从应力场和应变场可以看出,镍钛形状记忆合金管的外壁比内壁更容易满足塑性屈服准则,塑性变形区处于三向压应力状态。径向应变和切向应变为压缩应变,轴向应变为伸长应变。旋压载荷伴随滚珠旋压行程的变化对于预测旋压件的稳定流动具有重要的意义。 相似文献
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通过真空自耗电极熔炼法制备等原子比镍钛形状记忆合金。为了研究其断裂力学性能,进行铸态镍钛形状记忆合金的拉伸和压缩实验。为了更好地理解镍钛形状记忆合金的组织演变及断裂行为,分析铸态镍钛形状记忆合金及其断裂样品的显微组织。在拉伸加载下,镍钛形状记忆合金在750°C时具有较高的塑性,表现为韧性断裂,但在室温和-100°C时表现出较差的塑性,具有解理断裂和穿晶断裂的特征。在-100°C的压缩加载下,铸态镍钛形状记忆合金发生剪切断裂,剪切断裂面法线与压缩轴呈45°,具有解理断裂的特征,裂纹经由穿晶断裂而扩展。 相似文献
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As a new attempt, equal channel angular extrusion (ECAE) of nickel–titanium shape memory alloy (NiTi SMA) tube was investigated by means of process experiment, finite element method (FEM) and microscopy. NiTi SMA tube with the steel core in it was inserted into the steel can during ECAE of NiTi SMA tube. Based on rigid-viscoplastic FEM, multiple coupled boundary conditions and multiple constitutive models were used for finite element simulation of ECAE of NiTi SMA tube, where the effective stress field, the effective strain field and the velocity field were obtained. Finite element simulation results are in good accordance with the experimental ones. Finite element simulation results reveal that the velocity field shows the minimum value in the corner of NiTi SMA tube, where severe shear deformation occurs. Microstructural observation results reveal that severe plastic deformation leads to a certain grain orientation as well as occurrence of substructures in the grain interior and dynamic recovery occurs during ECAE of NiTi SMA tube. ECAE of NiTi SMA tube provides a new approach to manufacturing ultrafine-grained NiTi SMA tube. 相似文献
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Electrochemical behaviors of laser-welded Ti-50.6%Ni(mole fraction) shape memory alloy and the base metal in 0.9% NaCl solution were investigated by electrochemical techniques as corrosion potential measurement, linear and potentiodynamic polarization. The results indicate that the laser-welded NiTi alloy is less susceptible to pitting and crevice corrosion than the base metal, which is demonstrated by the increase in polarization resistance(Rp) and pitting potential(φpit) and decrease in corrosion current density(Jcorr) and mean difference between φpit and φprot values. It is confirmed by scanning electron microscope micrographs that pits could be observed on the surface of base metal but not on the surface of laser-welded alloy after potentiodynamic tests. An improvement of corrosion resistance of laser-welded NiTi alloy could be attributed to almost complete dissolution of inclusions upon laser welding. 相似文献
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Yan-qiu ZHANG Shu-yong JIANG Xiao-ming ZHU Ya-nan ZHAO Yu-long LIANG Dong SUN 《中国有色金属学会会刊》2017,27(7):1580-1587
Three different NiTi-based alloys, whose nominal compositions were Ni50Ti50, Ni49Ti49Fe2, Ni45Ti51.8Fe3.2 (mole fraction, %), respectively, were used in the current research to understand the influence of Fe addition on phase transformation behavior in NiTi shape memory alloy (SMA). The microstructure and phase transformation behavior of the alloys were investigated by optical microscopy (OM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analysis. The results show that the matrix of the Ni50Ti50 alloy consists of both B19′ (martensite) phase and B2 (austenite) phase. Moreover, the substructures of twins could be observed in the B19′ phase. However, the ternary alloys of NiTiFe exhibit B2 phase in the microstructures. Such microstructures were also characterized by large presence of Ti2Ni precipitates dispersed homogenously in the matrix of the two kinds of alloys. The addition of Fe to the NiTi SMA results in the decrease in phase transformation temperatures in the ternary alloys. Based on mechanism analysis, it can be concluded that this phenomenon is primarily attributed to atom relaxation of the distorted lattice induced by Ni-antisite defects and Fe substitutions during phase transformation, which enables stabilization of B2 phase during phase transformation. 相似文献
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Laser surface alloying technique was applied to fabricate a metallic porous coating on a solid NiTi shape memory alloy. By laser surface alloying a 40%TiH2-60%NiTi powder mixture on the surface of NiTi alloy using optimized laser process parameters, a porous but crack-free NiTi layer can be fabricated on the NiTi substrate. The porous coating is metallurgically bonded to the substrate NiTi alloy. The pores are uniformly distributed and are interconnected with each other in the coating. An average pore size of less than 10μm is achieved. The Ni content of the porous layer is much less than that of the original NiTi surface. The existence of the porous coating on the NiTi alloy causes a 37% reduction of the tensile strength and 55% reduction of the strain as compared with the NiTi alloy. Possible biomedical or other applications for this porous surface with good mechanical strength provided by the substrate are prospective. 相似文献
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作为一种崭新的尝试,局部包套压缩被应用于实现镍钛形状记忆合金在室温下的大塑性变形。基于主应力法和塑性屈服准则,分析了镍钛形状记忆合金局部包套的压缩塑性力学。采用透射电镜、高分辨透射电镜和扫描电镜研究镍钛形状记忆合金在局部包套压缩下的显微组织演变和变形行为。静水压力随着包套外径的增加而增加,有效地抑制了显微裂纹的萌生和扩展,有助于提高镍钛形状记忆合金的塑性,避免了脆性断裂的发生。在0.15~0.50的真实应变范围内,镍钛形状记忆合金在三向压应力状态下的塑性变形满足密席斯塑性屈服准则。在更大的塑性应变下,由于非晶相的出现,镍钛合金不能满足密席斯塑性屈服准则。 相似文献
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Shu-yong JIANG Ming TANG Ya-nan ZHAO Li HU Yan-qiu ZHANG Yu-long LIANG 《中国有色金属学会会刊》2014,24(6):1758-1765
Based on the local canning compression, severe plastic deformation (SPD) is able to lead to the almost complete amorphous nickel-titanium shape memory alloy (NiTi SMA), in which a small amount of retained nanocrystalline phase is embedded in the amorphous matrix. Crystallization of amorphous NiTi alloy annealed at 573, 723 and 873 K was investigated, respectively. The crystallization kinetics of the amorphous NiTi alloy can be mathematically described by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. NiTi SMA with a complete nanocrystalline phase is obtained in the case of annealing at 573 K and 723 K, where martensite phase transformation is suppressed due to the constraint of the grain boundaries. Crystallization of amorphous NiTi alloy at 873 K leads to the coarse-grained NiTi sample, where (001) martensite compound twin is observed at room temperature. It can be found that the martensitic twins preferentially nucleate at the grain boundary and they grow up towards the two different grains. SPD based on the local canning compression and subsequent annealing provides a new approach to obtain the nanocrystalline NiTi SMA. 相似文献