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Direct stiffness method
About: Direct stiffness method is a research topic. Over the lifetime, 2584 publications have been published within this topic receiving 53131 citations.
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TL;DR: Three main computing aspects encountered in the stress and strain analysis of the intact heart using the finite element technique, namely, the automatic partitioning of the myocardium of the heart into finite elements, the assemblage of the structural stiffness matrix of theMyocardium, and the storage and retrieval of its nonzero coefficients are described.
28 citations
TL;DR: In this paper, an efficient preconditioned conjugate gradient (PCG) technique and a computational procedure are presented for the analysis of symmetric anisotropic structures, which is based on selecting the pre-conditioning matrix as the orthotropic part of the global stiffness matrix of the structure, with all the nonorthotropic terms set equal to zero.
Abstract: An efficient preconditioned conjugate gradient (PCG) technique and a computational procedure are presented for the analysis of symmetric anisotropic structures. The technique is based on selecting the preconditioning matrix as the orthotropic part of the global stiffness matrix of the structure, with all the nonorthotropic terms set equal to zero. This particular choice of the preconditioning matrix results in reducing the size of the analysis model of the anisotropic structure to that of the corresponding orthotropic structure. The similarities between the proposed PCG technique and a reduction technique previously presented by the authors are identified and exploited to generate from the PCG technique direct measures for the sensitivity of the different response quantities to the nonorthotropic (anisotropic) material coefficients of the structure. The effectiveness of the PCG technique is demonstrated by means of a numerical example of an anisotropic cylindrical panel.
27 citations
TL;DR: In this article, a dynamic stiffness matrix is formed by frequency-dependent shape functions which are exact solutions of the governing differential equations of a non-uniform column and the natural frequencies of the nonuniform beams under axial force can be found by equating to zero the determinant of the dynamic stiffness matrices of the system.
27 citations
TL;DR: In this article, a 2.5D combined finite element-boundary element (FEM-BEM) model is proposed to predict free-field vibration levels in accordance with the most common international standards.
27 citations
TL;DR: In this paper, a joint stiffness configuration method is developed to optimize the dynamic characteristics of a whole vertical machining center, in which the premise is considering the joint characteristics to create the accurate finite element model (FEM) of the whole machine tool.
Abstract: Joint stiffness often has a significant effect on the dynamic characteristics of the whole machine tool. In this paper, a joint stiffness configuration method is developed to optimize the dynamic characteristics of a whole vertical machining center, in which the premise is considering the joint characteristics to create the accurate finite element model (FEM) of the whole machine tool. Identifying the joints parameters including the contact stiffness and damping of the linear guides, bolts, ball screws, and bearings is conducted. Vibration test and finite element simulation are implemented to verify the accuracy of the FEM which is created based on the identified joints parameters by comparing the tested and simulated frequency-response functions (FRFs). With these tested and simulated results, taking the dynamic flexibility at the spindle nose to measure the dynamic characteristics of the whole machine tool, vibration modes, and joints related to a higher modal flexibility and elastic energy distribution ratio can be determined to be the weak modes and joints respectively. Optimization aiming to decrease the modal flexibility is conducted by adopting the orthogonal experiment method to instruct the simulations to predict how stiffness of the weak joints affected the dynamic characteristics of the whole vertical machining center. Thus, an optimal joint stiffness configuration can be obtained by using the range analysis and fuzzy similar preference ratio method to analyze the simulated results. Redoing the simulation with the optimal configuration, results indicate that modal flexibility of each weak mode is decreased obviously. The decreased modal flexibilities and dynamic responses verify that the optimal configuration method is feasible to provide a way for improving the dynamic characteristics of the whole machine tool.
27 citations