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1.
高熵形状记忆合金是在等原子比NiTi合金的基础上,结合高熵合金的概念,逐渐发展起来的一种新型高温形状记忆合金。近年来,已开发出了综合性能优异的(TiZrHf)50(NiCoCu)50系和(TiZrHf)50(NiCuPd)50系高熵形状记忆合金,引起了广泛的关注和研究兴趣。本文从物相组成、微观组织、马氏体相变行为、形状记忆效应和超弹性等角度出发,综述了高熵形状记忆合金的研究进展,并对高熵形状记忆合金未来的研究重点进行了展望。  相似文献   
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To expand the measurement target from that containing simple cylindrical-shaped components to complex-shaped components that have several directional tilted surfaces, we determined an issue in measuring the rough surfaces with laser distance measurement. The issue is that laser speckle causes measurement error, which amount, we found, can be determined by the diameter and irradiation angle of the measurement laser beam. We then developed two error-reduction techniques that are based on the optical properties of a detected waveform and power. We conducted a basic experiment and a feasibility study with actual samples, to evaluate the distance measurement performance of targets with various surface roughness and irradiation angles. The roughness and angle range of the evaluation was determined considering actual measurement needs in parts manufacturing. We confirmed that the measurement error, whose maximum value was nearly 80 μm, decreased to less than 20 μm using our proposed local-maximum-power-based technique.  相似文献   
4.
《Advanced Powder Technology》2019,30(12):3088-3098
The purpose of this paper is to give process for preparing monodispersed silver particles with round shape having aspect ratio of 1, because the shape is suitable for preparing silver grids with fine pattern size. We found that the combination of gelatin and hydrazine gave the monodispersed silver particles with the aspect ratio of 1. Presence of the high molecular compounds is crucial probably because they are adsorbed on the surface of growing silver particles and control the uniform crystal growth. In addition, the relationship between these reaction conditions and the particle shape are discussed in detail.  相似文献   
5.
针对现有三维形状配准方法中存在左右翻转的错误匹配问题,提出了基于内蕴对称特征检测的高效形状配准算法。首先,通过热核与几何约束,构建模型的内蕴自对称点对;其次,基于谱嵌入特征空间分析,提取模型的内蕴对称平面,并依据模型表面法向量,有效识别模型的左右结构属性;进一步,根据内蕴对称点对,获得模型的一致性谱对称结构描述;最终,引入一致性点漂移算法(CPD),实现基于谱对称的非刚性模型的形状配准,有效避免了模型配准中的左右结构翻转问题。实验进一步论证了这种方法不仅有效提高模型匹配的效率,而且能有效识别同类模型的结构特征,对于非刚性模型的配准具有较强的鲁棒性。  相似文献   
6.
引入分形理论研究金属矿山采空区形状特征,采用计盒维数方法分别计算了四个不同矿山单个采空区一维边界线、二维区域、三维边界曲面以及三维空间体的分维数,研究探索得知单个采空区形状具有良好的分形特性,进而将单采空区分维值计算方法拓展至采空区群顶板分维值计算,研究证明采空区群顶板三维曲面形状也具有明显的分形特征。分维值是反映采空区复杂程度的定量参数,其为复杂采空区形状特征研究提供了一种新的方法,可供类似研究借鉴。  相似文献   
7.

噪声激励下形状记忆合金梁的概率响应

李玉婷,冯进钤,王迎宵

(西安工程大学 理学院,西安 710000)

摘要:

形状记忆合金是一种具有记忆效应和超弹性的材料,广泛应用于各个工程领域中。 基于弹性理论和Galerkin方法,本文提出了具有刚性约束的形状记忆合金梁的振动模型。应用随机平均法,得到该模型的概率响应。同时,通过数值模拟验证解析结果的正确性,从而证明了该随机平均法的有效性。 此外,讨论了随机分岔现象。 结果表明,一定的碰撞恢复力和阻尼力会引起P分岔。

关键词:形状记忆合金;随机平均;稳态概率密度;随机分岔

  相似文献   
8.
《能源学会志》2020,93(4):1460-1472
Chemical Looping Combustion (CLC) is one of the emerging technologies for carbon capture, with less energy penalty. The present way of using pulverized coals in a fluidized bed (FB)-CLC have limitations like loss of unconverted char and gaseous combustibles, which could be mitigated by use of coarser fuel particles. Devolatilization time is a critical input for the effective design of FB-CLC systems, primarily when large fuel particles are used. The present study investigates the devolatilization time and the char yield of three coals of two shapes, namely, two high ash Indian coals and a low ash Indonesian coal and a wood (Casuarina equisetifolia) in the size range of +8–25 mm, at different fuel reactor temperatures (800–950 °C) of a hematite based CLC unit. The devolatilization times of single fuel particles during CLC are determined using a visual method called ‘Color Indistinction Method’. Indonesian coal has the longest devolatilization time among the fuels, and biomass has the least. Increasing the bed temperature enhances the rate of volatile release, whereas this effect is less pronounced in larger particles. Devolatilization of Indonesian coal is found to be strongly influenced by the changes in operating conditions. With the decrease in sphericity, a maximum of 56% reduction in devolatilization time is observed for the +20–25 mm slender particles of Indonesian coals when compared to the near-round particles. The maximum average char yields at the end of the devolatilization phase for coal and biomass are about 55–76% and 16% respectively. Char yield in coal particles increases with an increase in particle size, whereas biomass particles show relatively consistent yield across all experimental conditions. Increase in bed temperature reduces the char yields of coal up to 12% and in biomass up to 30%. High volatile Indian coal is the most influenced fuel by the changes in fuels shape. A correlation for determining devolatilization time under CLC environment is presented, and it successfully fits most of the experimental values within ±20% deviation for coals (R2 = 0.95) and within ±15% deviation for biomass (R2 = 0.97).  相似文献   
9.
Ball screws are crucial for improving the reliability and interchangeability of transmission mechanical systems; however, existing contact measurement methods that utilise stylus contact are not efficient, which precludes their use for rapid in-situ geometry evaluation. This paper presents a vision-based two-stage method for rapid measurement of key parameters (raceway arc radii and centre distance) of ball screws. The edge contour information is extracted from the acquired image using the dual-tree complex wavelet transform and non-maximal suppression. In the matching stage, a shape-matching algorithm is used for detecting approximate geometrical centres of raceway arcs. The refinement stage, on the other hand, is implemented for acquiring precise dimensional results. Furthermore, the method of averaging multiple measurements is performed to suppress random noise. A comparative experiment is presented to validate the robustness of the proposed method. Based on experimental results, the calculated mean absolute errors in the measurement of the two raceway arc radii and the centre distance are found to be 0.0082 mm, 0.0079 mm and 0.0055 mm, respectively. This study therefore paves the way for key parameter measurement without removing ball screws.  相似文献   
10.
This paper presents a dynamic analysis of the free and forced vibration of a free-standing bridge of superelastic shape memory alloy TiNiCuCo film with ultra-low fatigue properties and evaluates its versatility for novel miniature scale damping applications. A thermodynamics-based finite element model is used to simulate the evolution of martensite phase fraction during load-induced martensitic phase transformation. The effects of pre-strain, strain rate and excitation load on the hysteresis of stress-strain characteristics are investigated in order to assess damping energies. The analysis is performed under non-isothermal conditions taking into account heat transfer and rate-dependence of release and absorption of latent heat. We show that damping energy can be maximized by applying an optimum pre-strain. A maximum damping capacity of 0.17 is determined for the case of complete stress-strain hysteresis loop during phase transformation.  相似文献   
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