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1. chinaXiv:202203.00067 [pdf]

Study on laser shocking of melt pool in Laser Additive Manufacturing of FeCoCrNi High-Entropy Alloys

Heng Lu; Xiaohan Zhang; Jian Liu ; Shusen Zhao; Xuechun Lin; Hui Li; Yaowu Hu
Subjects: Mechanical Engineering >> Mechanical Manufacture and Automation

With growing interest in Laser Additive Manufacturing (LAM) of High-entropy alloys (HEAs) during most recent years, the design of compositional elements and process strategies are primary methods to overcome undesirable microstructures and defects. Here we propose a new approach, a novel real-time Laser Shocking of Melt Pool (LSMP), to obtain melt pool modifications for yielding HEAs with desired characteristics. LSMP utilizes a pulsed laser shocking a liquid melt pool caused by a continuous wave laser, enabling non-destructive and real-time modulations for high-performance HEAs. The numerical simulation reveals the convection mechanism of the melt pool in the LSMP process, and the intervention of the pulsed laser promotes melt pool flow type to convert the Marangoni effect into a multi-convective ring, which accelerates melt pool flow and inhibits columnar crystal growth. Experimental results show the evolution law of the microstructure in the LSMP process. The microstructure of CrFeCoNi HEAs undergoes a Columnar-Equiaxed Transition (CET), and higher hardness is obtained. Laser shock is demonstrated to be an effective in-situ modulative tool for controlled additive manufacturing.

submitted time 2022-05-31 Hits1318Downloads446 Comment 0

2. chinaXiv:202205.00164 [pdf]

基于纳米压痕法的富Sn相应力-应变关系的研究

刘志高; 侯斌; 刘天寒; 秦红波
Subjects: Mechanical Engineering >> Machinofacture Technique and Equipment

在电子封装领域中,所用的无铅钎料主要是二元或者三元Sn基共晶或近共晶合金,其基体相为富Sn相。为得到富Sn相的力学性能及应力-应变关系,由纳米压痕试验测试获得了富Sn相的弹性模量与硬度,并得到载荷-位移曲线。采用有限元反演分析的方法确定了富Sn相的特征应力和特征应变,并由量纲函数确定应变强化指数。将特征应力和特征应变强化指数等参数代入幂强化模型中,计算得到富Sn相的屈服强度为31.51 MPa,并最终确定富Sn相的应力-应变关系函数表达式。

submitted time 2022-05-25 Cooperative journals:《桂林电子科技大学学报》 Hits420Downloads196 Comment 0

3. chinaXiv:202202.00044 [pdf]

From simple digital twin to complex digital twin Part I: A novel modeling method for multi-scale and multi-scenario digital twin

贾文杰; 王伟; 张振族
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering
Subjects: Computer Science >> Computer Software

近年来,数字孪生受到了广泛关注,数字孪生也正在变得越来越复杂。目前的数字孪生案例大多集中在一个特定的场景上,面对多层次多场景的工作环境,甚至模型的交互与耦合,仍缺乏构建复杂数字孪生的方法。本文提出了一种标准化的基于模型分割和组装的复杂数字孪生模型的建模方法。首先,将数字孪生的复杂模型按照4C架构中的层次(Composition)、场景(Context) 、组件(Component)和代码(Code)划分为若干简单模型。层次和场景使数字孪生专注于特定尺度和场景中的有效元素。组件和代码用于开发简单数字孪生模型。其次,通过信息融合、多尺度关联、多场景交互,将数字孪生的简单模型组装成复杂模型。本体模型构建了不同数字孪生中实体的完整信息库。知识图谱在不同尺度的数字孪生之间架起了关系的桥梁。场景迭代实现行为交互和计算结果精度的提高。本文提供了一种可实现的方法来构建复杂的数字孪生模型,并支持组件和代码的复用促进数字孪生的快速开发。

submitted time 2022-02-16 Hits2629Downloads508 Comment 0

4. chinaXiv:202202.00011 [pdf]

Exact Decomposition of Multifrequency Discrete Real and Complex Signals

刘保国
Subjects: Electronics and Communication Technology >> Information Processing
Subjects: Engineering and technical science >> Engineering General Technology
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering

‘The spectral leakage (SL) from windowing and the picket fence effect (PEF) from discretization’ have been among the standard contents in textbooks for many decades. The SL and PEF would cause the distortions in amplitude, frequency, and phase of signals, which have always been of concern, and attempts have been made to solve them. This paper proposes two novel decomposition theorems that can totally eliminate the SL and PEF, they could broaden the knowledge of signal processing. First, two generalized eigenvalue equations are constructed for multifrequency discrete real signals and complex signals. The two decomposition theorems are then proved. On these bases, exact decomposition methods for real and complex signals are proposed. For a noise-free multifrequency real signal with m sinusoidal components, the frequency, amplitude, and phase of each component can be exactly calculated by using just 4m–1 discrete values and its second-order derivatives. For a multifrequency complex signal, only 2m–1 discrete values and its first-order derivatives are needed. The numerical experiments show that the proposed methods have very high resolution, and the sampling rate does not necessarily obey the Nyquist sampling theorem. With noisy signals, the proposed methods have extraordinary accuracy.

submitted time 2022-02-08 Hits3601Downloads611 Comment 0

5. chinaXiv:202111.00026 [pdf]

Biological Knowledge-enabled BERT for Innovation in Biomimetic Design: A Case Study

Sun,Feng; Xu,He
Subjects: Mechanical Engineering >> Mechanical Design

The biomimetic design provides an adequate solution to achieve an excellent design. However, the prototype space for biomimetic design is relatively large, and it becomes more and more challenging to find the required biological prototypes quickly and efficiently. In order to improve the design efficiency and enrich the means of biomimetic innovation, this paper proposes a biological knowledge-enabled bidirectional encoder representation from transformers (BERT) model to assist biomimetic design, namely BioDesign. We extract the biological strategies, functions and extract dimensional information from the Asknature as the data source. The linguistic expression model-BERT was used to recommend biomimetic strategies or functions combined with the biological strategies data. Finally, we take the biomimetic erosion wear resistant design of the valve core as an example and use the proposed BioDesign model to recommend biomimetic inspired functions. According to the recommended content of the BioDesign model, we obtained the erosion wear resistance strategies and designed the biomimetic structure. The erosion wear experiment proved the feasibility and effectiveness of the proposed method.

submitted time 2021-11-17 Hits2902Downloads478 Comment 0

6. chinaXiv:201806.00198 [pdf]

经验模态分解在EAST超导线圈电压信号分析中的应用

陈远洋; 鲍晓华; 高格; 周洋
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering

超导托克马克聚变实验装置(EAST)的极向场超导线圈发生失超时,超导线圈电阻变化引起的微弱电压信号变化被强噪声淹没。针对该问题,运用快速傅里叶 变化分析线圈电压信号的时频特性。根据分析结果,提出运用经验模态分解(EMD)方法对超导线圈两端电压信号进行分析,得到若干固有模态分量和余项,并得知微弱 信号的能量主要分布在余项中。该方法能够消除环境影响,检测出电压信号的微弱变 化。

submitted time 2018-06-15 Cooperative journals:《电气工程学报》 Hits6360Downloads2531 Comment 0

7. chinaXiv:201806.00199 [pdf]

新能源配电网低碳高效运行的可拓层次评估方法

晏浩然; 吴杰康; 晏寒婷; 刘向东
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering

本文在传统配电网评估模型的基础上,建立了新能源配电网的综合评估指 标体系,该指标体系从设备运行状态、供电可靠性、电能质量、经济性以及环保性五 个方面较为全面地对新能源配电网进行综合评估,突出了新能源配电网区别于传统配 电网的特性,同时提出了基于可拓层次分析法的综合评估方法,该方法在传统层次分 析法的基础上考虑了人为判断的模糊性,并且较容易满足判断矩阵的一致性要求。最 后通过算例分析验证了指标体系的全面性和评估方法的适应性。

submitted time 2018-06-15 Cooperative journals:《电气工程学报》 Hits6193Downloads2488 Comment 0

8. chinaXiv:201806.00200 [pdf]

基于特征频带小波包分析的配电网故障选线的研究

叶宝柱; 薛超宇; 张惠娟; 韩叶; 刘伯颖
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering

通过对配电网单相接地故障暂态过程的分析,提出了对暂态接地电容电流 进行小波包分解,利用能量法提取出能量最大的频带,对各条线路的特征频带利用模 极大值和信号奇异性理论,从而判断出故障线路的新方法。对该方法的选线原理进行 了一定的介绍,仿真实验表明该方法具有精确、可靠、适应能力强等特点,具有重要 的实际应用价值。

submitted time 2018-06-15 Cooperative journals:《电气工程学报》 Hits6151Downloads2528 Comment 0

9. chinaXiv:201806.00201 [pdf]

基于固态变压器直流侧电压平衡控制的SVPWM算法

刘凯; 陈才学; 文军
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering

固态变压器作为能源互联网的核心设备具有电压等级转换和隔离的功能, 可以有效地整合分布式可再生能源,但模块级联 H 桥型固态变压器也存在各个 H 桥模 块之间的均压问题。本文首先研究了单相任意单元数级联 H 桥固态变压器的 SVPWM 及其电压平衡控制原理,提出一种固态变压器电压环控制一个 H 桥直流母线电压,然 后通过在 SVPWM 中增加一个新控制环控制其他 H 桥的矢量脉冲宽度,从而使其他 H 桥电压跟随的控制策略来实现各个 H 桥均压的目的。最后通过仿真验证了所提控制策略的正确性。

submitted time 2018-06-15 Cooperative journals:《电气工程学报》 Hits6417Downloads2768 Comment 0

10. chinaXiv:201806.00202 [pdf]

基于Edgeworth级数和多重线性化的 概率潮流算法

梁捷
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering

对含随机变量的大规模概率潮流问题,若使用 Gram-Charlier 级数展开式逼近随机变量的概率分布,计算量较大。建立考虑风电出力随机性和负荷波动性的概率 潮流模型,并采用 Edgeworth 通过的 Hermite 正交矩阵的递推性降低级数高阶展开的计算复杂度,针对级数变换法高次项被舍去影响逼近精度的问题,采用多重线性化的 方法通过对系统总有功功率的均匀划分,减小因潮流方程线性化时输入的随机变量的 变化范围较大而引起的截断误差。IEEE 39 节点系统的算例仿真结果验证了本方法的有效性。

submitted time 2018-06-15 Cooperative journals:《电气工程学报》 Hits6259Downloads2542 Comment 0

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