Joints dynamic identification and modeling based on FRFs data

The problem of joints dynamic identification and modeling is discussed in this paper. The theoretical dynamic model of joints is established by FRFs (frequency response functions) data, and formulas for identifying the joints dynamic properties is deduced. The equivalent value of dynamic stiffness is extracted by solving the inconsistent equation using the least square method. The experimental example is provided to validate the feasibility and accuracy of the proposed method, the predicted result showing good fitting with experimental results.

Stress Field Gradient Analysis Technique Using Lower-OrderC0Elements

For evaluating the stress gradient, a mathematical technique based on the stress field of lower-orderC0elements is developed in this paper. With nodal stress results and location information, an overdetermined and inconsistent equation of stress gradient is established and the minimum norm least squares solution is obtained by the Moore-Penrose pseudoinverse. This technique can be applied to any element type in comparison with the superconvergent patch (SCP) recovery for the stress gradient, which requires the quadratic elements at least and has to invert the Jacobi and Hessian matrices. The accuracy and validity of the presented method are demonstrated by two examples, especially its merit of achieving high accuracy with lower-order linearC0elements. This method can be conveniently introduced into the general finite element analysis programs as a postprocessing module.