Because wrist rotation dynamics are dominated by stiffness (Charles SK, Hogan N. J Biomech 44: 614-621, 2011), understanding how humans plan and execute coordinated wrist rotations requires knowledge of the stiffness characteristics of the wrist joint. In the past, the passive stiffness of the wrist joint has been measured in 1 degree of freedom (DOF). Although these 1-DOF measurements inform u...

We propose a fast stiffness matrix calculation technique for nonlinear finite element method (FEM). Nonlinear stiffness matrices are constructed usingGreen-Lagrange strains, which are derived from infinitesimal strains by adding the nonlinear terms discarded from small deformations. We implemented a linear and a nonlinear finite element method with the same material properties to examine the di...

First, the equations for calculating the full mass, stiffness and damping matrices from modal data are derived. This deviation was first presented in [1]. However, these equations are difficult to solve because the first step of their solution requires matrix inversion of the flexibility matrix to obtain the stiffness matrix. Not only does matrix inversion amplify errors, but the number of line...

In this paper we consider two variants of a trace finite element method for solving elliptic partial differential equations on a stationary smooth manifold Γ. A discretization error analysis for both methods in one general framework is presented. Higher order finite elements are treated and rather general numerical approximations Γh of the manifold Γ are allowed. Optimal order discretization er...

A new numerical method for simultaneously updating mass and stiffness matrices based on incomplete modal measured data is presented. By using the Kronecker product, all the variables that are to be modified can be found out and then can be updated directly. The optimal approximation mass matrix and stiffness matrix which satisfy the required eigenvalue equation and orthogonality condition are f...

The theory of complex mode shapes for damped oscillatory mechanical systems is explained, using the matrix of transfer functions in the Laplace domain. These mode shapes are defined to be the solutions to the homogeneous system equation. It is shown that a complete transfer matrix can be constructed once one row or column of it has been measured, and hence that mass, stiffness, and damping matr...

We define the notion of effective stiffness and show that it can used to build sparsifiers, algorithms that sparsify linear systems arising from finite-element discretizations of PDEs. In particular, we show that sampling O(n log n) elements according to probabilities derived from effective stiffnesses yields an high quality preconditioner that can be used to solve the linear system in a small ...

We study the spectral properties of stiffness matrices that arise in the context of isogeometric analysis for the numerical solution of classical second order elliptic problems. Motivated by the applicative interest in the fast solution of the related linear systems, we are looking for a spectral characterization of the involved matrices. In particular, we investigate non-singularity, condition...