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基于固化反应动力学、热传导和复合材料层合理论, 采用了有限元分析方法, 对具有金属内衬的复合材料纤维缠绕压力容器在固化工艺过程中的温度和热应力分布及其变化规律进行了数值模拟。通过一典型容器数值分析, 表明在固化工艺过程中, 中容器内部的所有应力分量具有同时达到峰值的特征, 其中应力分量的峰值出现在固化降温阶段的初期。提出了数值模拟的方法和分析结论对复合材料结构设计师和工艺师合理制订金属内衬复合材料纤维缠绕容器的工艺标准具有一定的参考价值。 相似文献
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针对含薄壁钢内衬碳纤维增强聚合物基复合材料(CFRP)多角度交替缠绕复合圆筒的剩余应力计算问题,基于正交各向异性材料的厚壁圆筒理论和弹性叠加理论,提出了考虑卸去芯模影响的多角度交替缠绕下CFRP各层和钢内衬剩余应力的逐层叠加算法,研究了恒缠绕张力下,芯模厚度和螺旋层缠绕角对CFRP各层和钢内衬剩余应力的影响。计算表明:芯模厚度越大则CFRP层剩余应力越低,但芯模厚度过大将减弱缠绕张力对钢内衬的强化效应;螺旋层缠绕角约65°时,环向层剩余应力出现极小值,螺旋层剩余应力和内衬剩余应力均出现极大值。针对缠绕张力对钢内衬的强化效应,通过水压试验加载过程中钢内衬声发射特征与复合圆筒外壁应变测试,测得的钢内衬屈服载荷与理论预测值一致,基本证实了算法的有效性。为提高CFRP层缠绕质量,基于等剩余应力假设,提出了多角度交替缠绕张力制度优化设计思路,适用于内压管的张力制度优化。 相似文献
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复合材料缠绕压力容器缠绕过程模拟 总被引:1,自引:0,他引:1
为了提高复合材料缠绕压力容器缠绕工艺效率及优化缠绕过程,研究并设计了复合材料缠绕压力容器缠绕过程的模拟软件.模拟软件主要包括两个模块:缠绕设计模块和模拟模块.模拟模块中,通过在几何空间和色彩空间,描述纤维缠绕压力容器成型工艺的芯模、落纱点、悬纱、丝头的运动规律和运动轨迹,形成动态画面,直观地反映出缠绕过程中落纱、纱线排布、悬纱、芯模和丝头运动以及线形变化,显示出纤维缠绕成型的全部过程.该模拟软件的建立,有利于加深对复合材料缠绕压力容器缠绕工艺过程的理解. 相似文献
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纤维缠绕厚壁柱形管道或容器在缠绕张力作用下会使缠绕纤维层的应力状态不断变化,形成沿壁厚力学性能非均匀的结构。依据缠绕过程中的纤维束应力状态分析和纤维束本构关系,获得了纤维体积含量与所受应力状态的关系。基于正交各向异性本构关系和双层筒模型的离散叠加法,建立了给定缠绕张力确定纤维缠绕厚壁柱形结构剩余张力的计算方法,并计算了等张力缠绕纤维层的纤维体积含量沿壁厚的分布。利用Tsai-Wu失效准则研究了纤维体积含量非均匀的厚壁柱形结构的纤维层强度。研究表明:缠绕工艺使内层纤维体积含量和强度均略高于外层,纤维缠绕厚壁柱形结构的强度分析和设计时应考虑这种影响;利用变化的缠绕张力设计可以实现强度比沿壁厚的均匀分布。 相似文献
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缠绕张力作为缠绕工艺中的关键因素,其合理设计直接影响制品性能。针对缠绕张力的设计,提出缠绕张力算法。基于各向异性缠绕层弹性变形及各向同性内衬厚壁筒理论,给出外压作用下缠绕层的径向应力及环向应力;在弹性范围内采用应力叠加原理建立剩余张力与缠绕张力之间的解析算法。结合三种典型的张力缠绕模型,给出剩余张力具体关系式;分析等剩余张力,得到不同特例下的剩余张力解析公式。依据该解析算法研究芯模内、外径比及张力锥度系数对各向同性材料缠绕层剩余张力分布的影响,表明芯模内、外径比与锥度系数变化对缠绕层剩余张力分布有显著影响,且该文算法简单、合理、可靠;对各向异性复合材料缠绕层等剩余张力分析,其结果与现有网格理论结果一致,且该文缠绕张力上下层变化平缓,易于张力控制的实现。 相似文献
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开展纤维缠绕结构缠绕与固化后残余应力评估是开展缠绕工艺优化设计、实现服役前预应力设计的重要前提。本文采用干法缠绕工艺,基于钢芯模和尼龙6(PA6)芯模分别制备了恒定张力(40 N)、内松外紧(20 N-40 N-60 N)和内紧外松(60 N-40 N-20 N)3种不同张力制度的复合材料缠绕圆筒,通过测试切割过程应变释放量与回弹变形对内部残余应力进行对比分析。借助生死单元法,建立了复合材料圆筒的逐层缠绕过程分析模型,模拟缠绕后残余应力分布;并基于CHILE(Tg)本构模型,开展了复合材料圆筒固化过程模拟,预测固化后残余应力及切割后回弹变形。研究表明:固化应力与缠绕张力均对总残余应力产生贡献,但由于固化过程剩余缠绕张力进一步放松,固化后总残余应力水平低于缠绕残余应力与固化应力之和。固化过程不会改变缠绕张力对最终残余应力分布的影响;缠绕张力对总残余应力的影响程度与芯模材质相关,芯模热变形越大,缠绕张力的影响越弱。当采用相同芯模时,内松外紧(20 N-40 N-60 N)张力制度产生的切割回弹角最小,内紧外松(60 N-40 N-20 N)张力制度产生的回弹角最大;当采用相同张力制度时,P... 相似文献
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针对可展开天线这一大跨度索梁组合结构体系,提出了一种可以考虑体系中梁单元影响的天线索网结构形态设计方法。该方法将可展开天线中的索网结构划分为具有确定形状要求的内部索网及与刚性外框相连的边界索网两部分。对于内部索网采用平衡矩阵分析法优化计算出索网中各索段的合理预张力值;对于边界索网则通过跟踪其与天线梁单元连接节点在预张力作用下的位置变化来计入天线刚性外框对索网的影响,并通过对形状变化后的索网进行迭代计算来得到各索段的预张力分布值。依据该文方法编制了相应的迭代计算程序,并通过算例分析验证了上述方法的正确性。 相似文献
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本文以 Poisson 方程为例,在不对节点进行重新排列的前提下,通过求解较低维数的矩阵方程,对交替方向隐式迭代格式进行了改进,降低了程序实现难度.以 Gauss 消去法为例,对改进的交替方向隐式迭代格式的计算量进行估计,发现改进的交替方向隐式迭代格式大大减少了计算量,并进一步证明了改进的交替方向隐式迭代格式与经典的交替方向隐式迭代格式的等价性.数值算例验证了改进的交替方向隐式迭代格式与经典的交替方向隐式迭代格式的等价性和改进的交替方向隐式迭代格式在计算量等方面的优越性. 相似文献
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本文采用有限元和边界元技术分析了重载径向轴承的三维弹性流体润滑(EHL)问题,并提出了一种精度高、收敛快的加权迭代计算模式,用该计算模式成功地求解了由二阶Reynolds方程、粘压方程和三维弹性方程组成的非线性方程组,得到了在各种大偏心率下轴承材料分别为钢、铜和巴氏合金的径向轴承的弹流静特性参数。 相似文献
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An iterative reconstruction method that was proposed for clipping noise cancellation in orthogonal frequency domain multiplexing (OFDM) systems is applied to multilevel quadrature amplitude modulation-based multi-carrier (MC) code division multiple access signals in downlink. The iterative method uses a known distortion function, maybe a nonlinear one such as a successive clipping and filtering process, in the iterations to give an approximation of inverse of the distortion process and then the iterative method removes distortion under a convergence condition. The authors show that MC signal with properly chosen clipping threshold satisfies convergence conditions of the iterative method. In contrast to some of the other reconstruction-based techniques, this method requires no extra bandwidth and side information and it can be implemented with reasonable complexity. Furthermore, the authors show that the proposed iterative scheme can be enhanced by using an extra frequency bandwidth. Exploiting extra bandwidth improves the performance of the reconstruction-based methods in case of using successive clipping and filtering. Simulation results will be used to demonstrate achievable bit-error-rate improvement by the proposed enhanced iterative scheme. 相似文献
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Some widely used methodologies for simulation of non-Gaussian processes rely on translation process theory which imposes certain compatibility conditions between the non-Gaussian power spectral density function (PSDF) and the non-Gaussian probability density function (PDF) of the process. In many practical applications, the non-Gaussian PSDF and PDF are assigned arbitrarily; therefore, in general they can be incompatible. Several techniques to approximate such incompatible non-Gaussian PSDF/PDF pairs with a compatible pair have been proposed that involve either some iterative scheme on simulated sample functions or some general optimization approach. Although some of these techniques produce satisfactory results, they can be time consuming because of their nature. In this paper, a new iterative methodology is developed that estimates a non-Gaussian PSDF that: (a) is compatible with the prescribed non-Gaussian PDF, and (b) closely approximates the prescribed incompatible non-Gaussian PSDF. The corresponding underlying Gaussian PSDF is also determined. The basic idea is to iteratively upgrade the underlying Gaussian PSDF using the directly computed (through translation process theory) non-Gaussian PSDF at each iteration, rather than through expensive ensemble averaging of PSDFs computed from generated non-Gaussian sample functions. The proposed iterative scheme possesses two major advantages: it is conceptually very simple and it converges extremely fast with minimal computational effort. Once the underlying Gaussian PSDF is determined, generation of non-Gaussian sample functions is straightforward without any need for iterations. Numerical examples are provided demonstrating the capabilities of the methodology. 相似文献
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Zhang J Zhang Q He G 《Journal of the Optical Society of America. A, Optics, image science, and vision》2008,25(3):710-717
A novel scheme for blind deconvolution is presented. Adapted from our previous multiplicative iterative algorithm, a more general scheme--the asymmetric multiplicative iterative algorithm--is derived. Additionally, in order to obtain a meaningful estimate, a penalized asymmetric multiplicative iterative algorithm is used to further improve the performance of this scheme. Results of a numerical experiment with the asymmetric multiplicative iterative algorithm are presented. 相似文献
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为了高效求解正定或半正定的大型稀疏线性方程组,在第一阶段采用经典矩阵分裂的基础上,广义非定常多分裂二阶段迭代方法的第二阶段分裂融合了多分裂和矩阵预处理技术,对非定常多分裂二阶段迭代方法进行了推广。为了研究收敛性,将该迭代方法的算法形式和逻辑语言表达形式改写为紧凑的迭代格式。由此得到,广义非定常多分裂二阶段迭代算法在一个充分条件下收敛。最后,具有五对角系数矩阵的大型稀疏线性系统的数值算例验证了广义非定常多分裂二阶段迭代算法的普适性,并且从迭代次数和\,CPU\,时间上体现了算法的高效性。 相似文献
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Lahmer T Kaltenbacher M Kaltenbacher B Lerch R Leder E 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2008,55(2):465-475
We propose an enhanced iterative scheme for the precise reconstruction of piezoelectric material parameters from electric impedance and mechanical displacement measurements. It is based on finite-element simulations of the full three-dimensional piezoelectric equations, combined with an inexact Newton or nonlinear Landweber iterative inversion scheme.We apply our method to two piezoelectric materials and test its performance. For the first material, the manufacturer provides a full data set; for the second one, no material data set is available. For both cases, our inverse scheme, using electric impedance measurements as input data, performs well. 相似文献
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Oleh Sobeyko 《国际生产研究杂志》2017,55(2):392-409
In this paper, we discuss an integrated process planning and scheduling problem in large-scale flexible job shops (FJSs). We assume that products can be manufactured in different ways, i.e. using different bills of materials (BOM) and routes for the same product. The total weighted tardiness is the performance measure of interest. A Mixed Integer Programming formulation is provided for the researched problem. Because of the NP-hardness of the investigated problem, an iterative scheme is designed that is based on variable neighbourhood search (VNS) on the process planning level. Appropriate neighbourhood structures for VNS are proposed. Because the evaluation of each move within VNS requires the solution of a large-scale FJS scheduling problem instance, efficient heuristics based on local search from previous research are considered on the scheduling level. Extensive computational experiments based on new randomly generated problem instances are conducted. In addition, a parallel version of the VNS is investigated within the computational experiments. The proposed iterative scheme is benchmarked against a genetic algorithm (GA) from the literature that simultaneously considers process planning and scheduling for the special case where a single BOM is available for each product. It turns out that the new iterative scheme outperforms the GA and a memetic algorithm based on the GA. It is able to solve even large-size problem instances in reasonable amount of time. 相似文献
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V. Monchiet G. Bonnet 《International journal for numerical methods in engineering》2012,89(11):1419-1436
It is recognized that the convergence of FFT‐based iterative schemes used for computing the effective properties of elastic composite materials drastically depends on the contrast between the phases. Particularly, the rate of convergence of the strain‐based iterative scheme strongly decreases when the composites contain very stiff inclusions and the method diverges in the case of rigid inclusions. Reversely, the stress‐based iterative scheme converges rapidly in the case of composites with very stiff or rigid inclusions but leads to low convergence rates when soft inclusions are considered and to divergence for composites containing voids. It follows that the computation of effective properties is costly when the heterogeneous medium contains simultaneously soft and stiff phases. Particularly, the problem of composites containing voids and rigid inclusions cannot be solved by the strain or the stress‐based approaches. In this paper, we propose a new polarization‐based iterative scheme for computing the macroscopic properties of elastic composites with an arbitrary contrast which is nearly as simple as the basic schemes (strain and stress‐based) but which has the ability to compute the overall properties of multiphase composites with arbitrary elastic moduli, as illustrated through several examples. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献