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The aim of this paper is to study the residual stresses in an UIC-60 rail and their reduction by means of roller straightening. Both experimental and numerical investigations have been carried out in the past to reveal the formation of dominant longitudinal residual stresses. However, the agreement between both investigations was not particularly good. The finite element method (FEM) has also been used to simulate one, two and three-dimensional analyses of a rail during roller straightening processes. The present model considers the longitudinal movement of a rail through the straightening machine, contact conditions between rail and rollers and kinematic hardening so as to take into account the plastic behaviour of the rail material (steel). These results were compared with the experimental investigations and good agreement was observed. In this respect, this paper presents a novel, more realistic numerical simulation by FEM for the roller straightening process. Finally, an improvement of the straightening process in order to obtain smaller residual stress in the rail section is proposed.  相似文献   
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Two separate theoretical models are developed to predict the number of heat applications necessary to repair specified bends in damaged steel plates. One model is an application of the theory of reliability; this idealization is subsequently further simplified for practical engineering applications. The second is an application of the theory of stochastic processes: envisioning the record of plastic rotations obtained from the actual heat-straightening of a subject plate as a finite portion of a member of the infinite ensemble of possible records for the repair, and assuming this process to be stationary and ergodic in the heat-number domain, the theory of discrete spectral analysis is used to construct the power spectral density function of the process, and simulate artificial records. Then, simple statistical analysis allows the prediction with any desired degree of confidence. These independent probability-based estimates successfully verify each other. As expected, the required number of repair heats for each test in the ensuing experimental program, under carefully controlled laboratory conditions, was consistently smaller than the corresponding theoretical prediction.  相似文献   
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We describe a straightening algorithm for the action of S n on a certain graded ring . The ring appears in the work of C. de Concini and C. Procesi [2] and T. Tanisaki [8], and more recently in the work of A. Garsia and C. Procesi [4]. This ring is a graded version of the permutation representation resulting from the action of S n on the left cosets of a Young subgroup. As a corollary of our straightening algorithm we obtain a combinatorial proof of the fact that the top degree component of affords the irreducible representation of S n indexed by .  相似文献   
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薄壁管材在连续矫直过程中,各矫直辊组的压弯量作为核心工艺参数直接决定了薄壁管材的矫直精度。而目前现场仍沿用经验图表结合人工经验和反复试矫对其进行估定,亟待建立针对性的压弯量数学模型以指导生产。为此从薄壁管材的结构特点和矫直辊系组成出发,构建了针对压弯量计算的简化悬臂结构模型,基于相关假设和弹塑性相关理论,分别确定了平面应力状态下弹性区和弹塑性区管材横截面的弯矩模型,运用虚功原理建立了矫直辊压弯量力学模型,并给出了数值计算方法,完成了程序开发。经有限元动态仿真试验证明了模型的正确性和适用性,通过对典型管材数据的计算绘制了一系列工艺参数曲线,得到管材轴线弯曲半径和压弯量随管材直径、壁厚和屈服极限的变化关系,为现场压弯量的调整提供理论依据。  相似文献   
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Let a piece of the boundary of a Lipschitz domain be parameterized conventionally and let the traces of functions in the Sobolev space W p 2 be written out through this parameter. In this space, we propose a discrete (diadic) norm generalizing A. Kamont’s norm in the plane case. We study the conditions when the space of traces coincides with the corresponding space for the plane boundary.  相似文献   
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In this paper we study the dependence of the local geometry of real-analytic hypersuffaces in ℂ n on the dimension of the group of biholomorphic automorphisms of this surface. We also classify the hypersurfaces in terms of this group. We present some examples showing that the classes of the given construction are not empty. We find a new formulation of the Freeman theorem on the so-called straightening of a real-analytic CR-submanifold in ℂ n with degenerate Levi form of constant rank. Translated fromMatematicheskie Zametki, Vol. 61, No. 3, pp. 349–358, March, 1997. Translated by E. G. Anisova  相似文献   
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We use elements in the quantum hyperalgebra to define a quantum version of the Désarménien matrix. We prove that our matrix is upper triangular with ones on the diagonal and that, as in the classical case, it gives a quantum straightening algorithm for quantum bideterminants. We use our matrix to give a new proof of the standard basis theorem for the q-Weyl module. As well, we show that the standard basis for the q-Weyl module and the basis dual to the standard basis for the q-Schur module are related by the quantum Désarménien matrix.  相似文献   
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