共查询到18条相似文献,搜索用时 234 毫秒
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电磁成形有限元模拟涉及多场耦合作用,其中结构场与电磁场之间的不同耦合方法对模拟结果影响显著。与松散耦合方法相比,顺序耦合方法考虑了板料变形对电磁场的影响,从而能够更精确的描述电磁成形过程。以ANSYS仿真软件为平台,建立板料电磁成形的顺序耦合三维有限元模型。通过不同耦合方法的模拟结果与实验结果对比表明,采用顺序耦合模型得到的板料变形与实验接近,而采用松散耦合模型得到的板料变形明显大于实验值。由此可见,顺序耦合模型是适合于电磁成形模拟的可靠模型。采用顺序耦合模型研究发现,放电电流的加载时间对板料电磁成形中板料变形的影响显著。当取放电时间为电流曲线的1.5个周期时,模拟结果与实验数据吻合最好。综合考虑计算效率与精度,板料电磁成形中放电电流的加载时间取1.5个周期为宜。 相似文献
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对连铸过程中电磁流体力学的数值模拟的研究现状进行了综合评述。介绍了一种应用于连铸过程中的低频电磁流体力学数值模拟的新方法,并给出了其在圆坯旋转搅拌、CSP薄板坯电磁制动和板坯二冷辊式行波搅拌中的应用实例。该方法特点是分别建立电磁场模型和流场模型,并采用磁感应方程实现电磁场和流场模型之间的耦合。结果表明,目前的方法可较为准确地描述连铸过程中的电磁场分布和电磁流体力学特点,并能够对电磁搅拌参数和连铸工艺过程进行优化。最后,提出了连铸过程中电磁流体力学数值模拟技术的未来发展趋势。 相似文献
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电磁搅拌法制备半固态浆料过程电磁场、流场和温度场的数值模拟 总被引:5,自引:1,他引:4
建立了铝合金半固态浆料电磁搅拌过程宏观传输物理量耦合的数学模型,采用有限元和有限差分相结合的方法实现电磁搅拌条件下电磁场、流场和温度场的耦合模拟分析,研究电磁搅拌工艺参数对流场和温度场的影响规律,并进行实验验证。结果表明:水平旋转的电磁力场在铝合金熔体内均匀分布,其方向与交变电磁场的旋转方向一致,大小则因集肤效应从边部到中心递减;熔体内速度场分布与电磁力相似,但随着搅拌时间的延长,熔体温度降低,速度不断降低;电磁搅拌条件下熔体凝固速度加快,熔体心部和边部的温度梯度变小;搅拌电流强度和频率对电磁场、速度场和温度场分布的影响非常明显。 相似文献
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ASTM E816-96利用电磁声换能器(EMAT)技术进行超声检查的标准方法 总被引:1,自引:1,他引:1
1 范围1 .1 本标准规定了利用电磁声换能器 ( EMAT)进行特定的超声波检测的工艺规程和方法。推荐利用EMAT技术进行表面检测、整体检测和测厚的特定应用。1 .2 本标准方法为利用电磁声换能器能产生和接收超声波信息进行可靠的能再生的超声波整体检测和测厚提供了技术细节和指导方针。在这一点上 ,EMAT技术可以作为一种基础性技术为各种元件的适用性和生产的过程控制提供无损评估办法。1 .3 本标准方法包含了一些非接触性检测方法 ,这些方法是利用电磁场产生连续不断的超声波能量进入到样品中去的方法进行检测的。常用到的波形有表面… 相似文献
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In this paper, a hybrid nondestructive testing (NDT) method combining with the pulsed eddy current testing (PECT) method and the electromagnetic acoustic transducer (EMAT) method has been proposed and validated through numerical simulations and experiments. First, a numerical code is developed for the simulation of hybrid EMAT/PECT signals based on the developed EMAT and PECT code. Second, based on the numerical simulation, the influences of the eddy current induced by the excitation coil and the eddy current due to the velocity effect of the ultrasonic wave are compared and analyzed. In addition, the features of the EMAT and the PECT signals are analyzed respectively. Third, several signal separation and extraction methods are proposed on the basis of the spectral analysis and filtering strategies for extracting EMAT and PECT signals from the mixed signals of the hybrid EMAT/PECT method and their validity are evaluated through experiments. Finally, hybrid EMAT/PECT experiments are conducted and three types of defects (surface defects, bottom thinning defects, composite defects) in an aluminum plate and a SUS304 plate are successfully detected at the same time using the proposed hybrid NDT method and the signal feature parameters. Based on the numerical and experimental results, the proposed hybrid PECT/EMAT NDT method is demonstrated both high detectability and high efficiency for detecting surface and volumetric defects at the same time. 相似文献
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电磁超声检测技术由于无需媒介以及与被测物体非接触,不但可提高检测效率,而且可将超声检测技术的应用扩展到高温、高速和在线检测。根据电磁超声传感器的工作原理,建立了基于有限元的电磁超声无损检测数值分析方法,开发了相应的计算程序,验证了其有效性。应用开发的电磁超声数值模拟程序,研究了不同激励方式对电磁超声波的影响,得到了相应超声波在均匀各向同性金属介质中的传播过程。该计算方法和程序为实际电磁超声检测中缺陷的定量和探头优化提供了手段。 相似文献
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The amplitude of an ultrasonic signal generated by electromagnetic acoustic transducers (EMATs) is typically low when compared to those generated by contacting transducers, which restricts the application of EMATs in the fields of nondestructive testing and nondestructive evaluation. The transmission process of a surface wave EMAT is studied, based on a previously established 3-D model, with the aim of enhancing the amplitude of ultrasonic waves generated by the EMAT. The effect of changing various EMAT parameters on the surface wave is investigated, by utilizing the orthogonal test method. Results indicate that after optimization, the signal amplitude of the EMAT has increased by 25.2%. 相似文献
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板料冲压成形数值模拟中有限元方程求解算法的研究 总被引:1,自引:0,他引:1
在板料冲压成形的有限元数值模拟过程中,有限元方程的求解是有限元分析中的一个重要步骤。通过分析非线性方程组的常用求解方法发现,无论采用何种方法,最终都回归到线性方程组的求解方法上。提出采用迭代法取代自主开发系统SheetForm中的直接法,提高了计算效率。在提出的广义相邻节点以及节点的相邻关系的两个定义上,分析了整体刚度矩阵的形成原理,提出一种新的适合迭代法的二维变带宽存储方法,最大程度的节省了内存,而且避免了节点编号的优化难题。最后,通过实例验证了迭代算法在求解大型有限元模型时具有较高的计算效率。 相似文献
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The following paper introduces an approach, which allows the consideration of the kinematic as well as the dynamic properties of parallel kinematic machines. Based on the results of a preceding kinematic optimization, a FEM-model with arbitrary input parameters is designed. The full kinematic functionality of struts and joints used is ensured. By coupling the FEM-model to the GNU Octave numerical program system, a variety of movements including machining forces can be simulated. A Broyden-Fletcher-Goldfarb-Shanno optimization algorithm, using GNU Octave, was written and coupled to the FEM-system. Now, this algorithm is able to influence the model's arbitrary input parameters during the optimization process. Thus, the model is optimized automatically for a certain machining process and/or dynamic behavior. This procedure is demonstrated using the example of a delta robot structure originally designed by Raymond Clavel [7]. 相似文献
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基于自由燃烧的钨极氩弧焊电弧的传热和流体流动,建立了二维稳态的轴对称模型.在此基础上对电流参数改变所引起的电弧热物理过程进行了计算,得出了改变电流参数条件下电弧温度场和速度场的分布,并分析比较了计算结果.结果表明,电流的增加引起了电弧输入能量的增加,带来了电弧整体参数的提高,与经典电弧理论基本吻合.方程的求解采用的是以SAMPLE算法为基础编写的通用热流计算软件PHOE-NICS(parabolic hyperbolic or elliptic numerical integration code series). 相似文献