Papers by Keyword: Finite Element Model Updating

Abstract: This paper revisits the long-standing question of how to fully characterise the in-plane plastic anisotropy of sheet metals without assembling evidence from multiple standardised tests. The central idea is pragmatic: a single, well-designed heterogeneous biaxial experiment can replace the conventional combination of uniaxial and equibiaxial tests if the specimen and the inverse identification method are co-designed to (i) activate informative stress states and (ii) maintain low strain gradients for accurate digital image correlation measurements. The proposed cruciform specimen is deliberately conceived as a benchmark configuration for full-field inverse identification, with known locations and stress-strain states at which relevant material information is embedded. The approach is coupled with a Finite Element Model Updating framework, enabling all anisotropy parameters of the YLD2000-2d model to be identified from a single full-field dataset. Sensitivity and identifiability analyses demonstrate that a physically based parameter formulation significantly improves the conditioning of the inverse problem. Virtual experimentation confirms the robustness and accuracy of the proposed “one-test” identification strategy.

Abstract: Computer-aided engineering systems rely on constitutive models and their parameters to describe the material behaviour. The calibration of more elaborated material models with a larger number of parameters becomes very time and cost consuming. The development of image-based technology has enhanced the interest in inverse identification methods, which, when coupled with full-field measurements, have the potential to reduce the number of experimental tests required to accurately identify material properties. This work aims to identify the Swift hardening law parameters of a dual-phase steel using a tensile test on a heterogeneous dogbone specimen under uniaxial and quasi-static loading conditions using the finite element model updating (FEMU) technique. The numerical results were used to generate synthetic images, which were then processed by digital image correlation (DIC) and used as the reference in the identification procedure. Two different approaches were tested: (i) directly comparing the numerical results to the reference; (ii) using DIC-levelled numerical data by iteratively generating synthetic images and using the DIC filter with the same settings as were used on the reference (virtual experiment). The identification results obtained from both approaches are compared and discussed.

Abstract: In this paper, the short beam shear (SBS) test combined with digital image correlation (DIC) and finite element model updating (FEMU) method is conducted for identification the constitutive parameters of unidirectional composite laminates by minimizing the objective function which is established based on the variance of measured strain and numerical calculated strain. This method has the advantages of insensitive to initial value and high identification efficiency. By changing the test parameters, specimens with different principal planes were used in the SBS test and different failure modes achieved. The standard deviation of E_22C and E_33C was 8.47% and 3.58% respectively. The comparison of the identification results of the same batch of specimens, different principal planes, different failure modes and different ROI shows that the results of constitutive identification using the area directly under the indenter is reliable.

Abstract: Finite element model updating is a well-known technique to better characterize the real behaviour of civil engineering structures. The updated numerical model can be used to perform a more accurate structural assessment. Herein, its effectiveness is validated through the fatigue assessment of a lively footbridge considering two different numerical models: (i) a preliminary finite element (FE) model and (ii) an updated version of the preliminary model based on the modal parameters of the footbridge identified experimentally. For this purpose, the Malecon footbridge (Murcia, Spain) has been considered. This footbridge, a cable-stayed structure, is prone to vibrate in vertical direction under continuous walking pedestrian flows so fatigue damage might be expected on its supporting cables. A detailed FE model of the footbridge has been performed and subsequently updated based on the experimental modal parameters of the structure. The behaviour of the pedestrian flows was characterized by field observations. Finally, a comparison is performed between the fatigue damage of some cables of the footbridge considering the two mentioned FE models. The safe life method was used to assess such damage. As result, a maximum relative difference around 52 % was obtained between the two numerical models.

Abstract: In this paper the initial finite element model (IFEM) of the Jing Yue Yangtze River Highway Bridge was established and achieved the reasonable finished state of the bridge, which was the large-span, unequal height pylons and mixed beam cable-stayed bridge. The three-dimensional IFEM of the bridge accurately reflected its mechanical behavior under the static loading, and the structure physical parameters and stiffness of the IFEM didn’t need updating through the static loading test. The boundary condition parameters of the IFEM were updated through comparing the measured modal results of the dynamic loading test with the modal analysis results of the IFEM. The updated finite element model can truly reflect the dynamic characteristics of the bridge structure, and the model can be used as the benchmark finite element model, which can provide reliable calculation benchmark of the long term status assessment during the service stage.

Abstract: This paper proposes a simplified finite element model to represent a riveted lap joint in structural dynamic analysis field. The rivet is modeled by spring-damper elements. Several numerical models are studied with different quantities of rivets (1, 3 and 5) and spring-damper elements (4, 6, 8, 12, 16 and 20) per rivet. In parallel, samples of two aluminum material plates connected by different quantities of rivets (1, 3 and 5) are built and tested in order to be known its modal characteristics – natural frequencies and mode shapes. The purpose of the different settings is to get the best numerical riveted lap joint representation relatively to the experimental one. For this purpose a finite element model updating methodology is used. An evaluation of the best numerical riveted lap joint is carried out based on comparisons between the numerical model after updating and the experimental one. It is shown that the riveted lap joints composed by eight and twelve spring-damper elements per rivet have the best representation. A stiffness constant value k is obtained for the riveted lap joints in study.

Abstract: This article briefly reviews the two methods of finite element model (FEM) updating, such as direct matrix methods and the sensitivity-based model updating methods. In addition, the problem in bridge structure model updating often needs to solve large-scale ill-posed linear systems. Therefore, two regularization methods of Tikhonov and TSVD were introduced. Meanwhile, for these systems, it is proposed that the application of the two kinds of regularization method to solve the problem which the test data contaminated by noise may rarely lead to a physically meaningful updated model.

Abstract: With the increasing complexity of the products, engineers face a higher level of uncertainty in both simulation and test. Correlation between numerical and experimental analysis using model updating techniques helps engineers to asses uncertainty. Present research efforts focus to combine finite element analysis and testing in one common framework. Experimental and operational modal analysis and simulation make benefit from common databases. Some applications presented emphasize the advantages of these techniques.

Abstract: Elastic modulus is an important parameter in structural analysis. This paper identifys the structural elastic modulus with measured displacements, which is an inverse problem. The improved genetic algorithm combined with multi-cases measurement is applied in the solution. Numerical examples have proved that the method is available.

Abstract: In this paper, two experimental techniques, Electronic Speckle Pattern Interferometry and Stroboscopic Interferometry, and two different finite element analysis packages are used to measure or to analyze the frequencies and mode shapes of a micromachined, cross-shaped torsion structure. Four sets of modal data are compared and shown having a significant discrepancy in their frequency values, although their mode shapes are quite consistent. Inconsistency in the frequency results due to erroneous inputs of geometrical and material parameters to the finite element analysis can be salvaged by applying the finite element model updating procedure. Two updating cases show that the optimization sequences converge quickly and significant improvements in frequency prediction are achieved. With the inclusion of the thickness parameter, the second case yields a maximum of under 0.4% in frequency difference, and all parameters attain more reliable updated values.