Finite element models of spot welds in structural dynamics: review and updating

This paper gives an overview of the finite element modelling of spot welds for the analysis of the dynamic response of structures. In particular models for dynamic analysis that use coarse meshes and equivalent parameters are considered. A major requirement for these models is their accuracy in predicting the dynamic behaviour of spot welded structures despite the low number of degrees of freedom. Three different models of spot welds are investigated [1–3] and for each model physical parameters have to be assigned based on engineering insight. The aim of the present paper is to improve the accuracy of these three models by searching for the optimum values of the parameters characterising the spot weld models using experimental data. For this purpose a benchmark structure has been analysed, consisting of a thin walled hat section beam made of two plates welded together by twenty spot welds. The predicted natural frequencies and modes of the benchmark structure have been compared to the experimental modes. Updating of the finite element models has been performed and the accuracy of the three models has been significantly improved.

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Validating and Updating Finite Element Models Using Experimental Measurements of Dynamics

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1243/pime_proc_1990_204_208_02 ◽

1990 ◽

Vol 204 (1) ◽

pp. 45-50

Author(s):

C F McCulloch ◽

P Vanhonacker ◽

E Dascotte

Keyword(s):

Finite Element ◽

Structural Dynamics ◽

Model Updating ◽

Measured Data ◽

Physical Parameters ◽

Experimental Measurements ◽

Finite Element Models ◽

Data Sets ◽

Modal Data ◽

Modelling Assumptions

A method is proposed for updating finite element models of structural dynamics using the results of experimental modal analysis, based on the sensitivities to changes in physical parameters. The method avoids many of the problems of incompatibility and inconsistency between the experimental and analytical modal data sets and enables the user to express confidence in measured data and modelling assumptions, allowing flexible but automated model updating.

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Correction of Joint Stiffnesses and Constraints for Finite Element Models in Structural Dynamics

Journal of Applied Mechanics ◽

10.1115/1.2900733 ◽

1993 ◽

Vol 60 (1) ◽

pp. 117-122 ◽

Cited By ~ 13

Author(s):

John E. Mottershead ◽

Shao Weixun

Keyword(s):

Finite Element ◽

Structural Dynamics ◽

Physical System ◽

Discrete System ◽

Shape Function ◽

Least Squares Method ◽

Finite Element Models ◽

Reduction Scheme ◽

Boundary Constraints ◽

Framework Model

Finite element models are based upon known physical characteristics. But there are two main sources of error, namely (i) ill-defined joints and boundary constraints, and (ii) overstiffening due to the application of shape function discretization. It is difficult to correct an ill-defined constraint without simultaneously compensating (to some unknown degree) for discretization overstiffening. A general approach is proposed whereby the measured eigendata from a physical system are altered to resemble the eigendata of a discrete system with identical (but unknown) constraints. With the effects of discretization overstiffening present in both the adjusted measurements and the model it is straightforward to obtain progressively improved estimates of the constraint stiffnesses by using the least-squares method. The proposed approach may be considered to be equivalent to a model reduction scheme. Specific methods are applied to the correction of a stiffness in the joint of a finite element framework model.

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