Florent Mathieu

EikoSim

Identification of constitutive parameters relies mainly on their sensitivity to the measurands. In particular, the specific static and kinematic responses controlled by each parameter of interest has to be captured by full-field measurements. The development of modern constitutive models has led to many new and interesting sample geometries and loa...

The sensitivity fields required for identification methods such as Finite Element Method Updating (FEMU) or Integrated Digital Image Correlation (IDIC) are usually expensive to compute and require considerable amounts of memory storage. This research evaluates the application of Proper Orthogonal Decomposition (POD) to provide efficient means to re...

Full-field identification methods such as finite element model updating or integrated digital image correlation minimize the gap between an experiment and a simulation by iterative schemes. Within the algorithms residual fields and sensitivity fields are used to achieve identification. This paper discusses how these same fields can be used to asses...

Background:The goal of the present study is to illustrate the full integration of sensor and imaging data into numerical procedures for the purpose of identification of constitutive laws and their validation. The feasibility of such approaches is proven in the context of in situ tests monitored by tomography. The bridging tool consists of spatiotem...

To analyze the delamination behavior of a thermoset composite, the parameters of a mixed mode cohesive model are identified by combining experimental displacement fields measured via global digital image correlation and load data in a single cost function written within a Bayesian framework using Finite Element Model Updating. A sensitivity analysi...

The identification of the parameters of several constitutive laws is performed with the integrated digital image correlation (IDIC) technique in a biaxial experiment for a cruciform specimen made of stainless steel. The sought material parameters are assessed with the contribution of both reaction forces (from load sensors) and displacement fields...

This paper presents a coupled experimental/numerical procedure to evaluate triaxiality fields. Such a type of analysis is applied to a tensile test on a thin notched sample made of Ti 6-4 alloy. The experimental data consist of digital images and corresponding load levels, and a commercial code (abaqus) is used in an integrated approach to digital...

A method based upon the sensitivity fields is proposed to optimize biaxial experimental procedures. The objective is to improve the identifiability of elastic parameters related to an a priori chosen constitutive law. This is achieved by minimizing the covariance matrix of the material parameters. This approach unifies full field measurements via i...

A unified Digital Image Correlation (DIC) / eXtended Finite Element Method (X-FEM) framework based on the Williams’ series for fatigue crack growth identification and simulation is proposed. Williams’ series are used for post-processing the displacement measured by digital image correlation. It gives access to the change of stress intensity factors...

Several digital image correlation and extraction techniques exist for measuring stress intensity factors and locating crack tips during propagation experiments. Some of these techniques are based upon the analysis of local displacements in the vicinity of the crack tip and their decomposition onto a set of mechanically relevant fields, e.g. William...

DIC-based identification of the constitutive parameters of an elastoplastic law is addressed both from a general viewpoint, and applied to the particular case of dog-bone sample made of commercially pure titanium and subjected to tensile loading. A two-step procedure (Digital Image Correlation — DIC — followed by weighted Finite Element Method Upda...

The problem of identifying the (non-linear) mechanical properties of a solid from images taken in a mechanical testing machine is considered. The two classical steps of i) measuring the displacement field with digital image (and volume) correlation and ii) identifying the mechanical properties from the displacement field are combined into a single...

The paper is devoted to the identification of interlaminar properties by analyzing three tests with different mode mixities on a unidirectional thermoset composite material. It is shown that by coupling digital image correlation with finite element simulations, it is possible to locally extract energy release rates whose standard uncertainty is at...

A novel methodology to identify a fatigue crack propagation law is proposed. It is based on an optimization scheme that directly interrogates the images from the sought law rather than using a sequence of fitting schemes. Two procedures are presented and tested first on artificial data with a known law, and second on an actual image series obtained...

Field measurement techniques, and more particularly those based on Digital Image Correlation (DIC), are mature techniques for the determination of displacements of two or three-dimensional objects. The goal of this work is to develop test and associated identification DIC-based techniques to identify the mechanical behavior of a commercially-pure t...

It is proposed to use digital image correlation (DIC) to identify parameters governing crack propagation of commercially pure titanium. To achieve this goal, crack tip location, stress intensity factor, T-stress and plastic zone size are sought. Most of the DIC approaches are based upon local analyzes of displacements, and their subsequent projecti...

In this study, a crack in commercially-pure Titanium (CP-Ti) is observed with optical means during its propagation in fatigue. Digital image correlation is then used to extract directly, with no post-processing step, the crack tip location and the corresponding stress intensity factor amplitude to evaluate the parameters of Paris’ law, the T-stress...