Behzad V. Farahani

The Axisymmetric Analysis of Circular Plates Using the Radial Point Interpolation Method

This work extends the radial point interpolation method (RPIM) to the elasto-static analysis of circular plates. Instead using a plate bending theory, the 2D axisymmetric deformation theory is assumed. The RPIM enforces the nodal connectivity with the influence-domain concept and integrates numerically the integro-differential equations governing the studied phenomenon using a background integration mesh. Thus, both concepts are revised and more adequate parameters are found for the axisymmetric RPIM approach. Several benchmark circular plate examples are solved and the results are compared with other numerical approaches, showing that the RPIM is capable to obtain accurate and smooth variable fields.

A radial point interpolation meshless method extended with an elastic rate-independent continuum damage model for concrete materials

ABSTRACT An advanced discretization meshless technique, the radial point interpolation method (RPIM), is applied to analyze concrete structures using an elastic continuum damage constitutive model. Here, the theoretical basis of the material model and the computational procedure are fully presented. The plane stress meshless formulation is extended to a rate-independent damage criterion, where both compressive and tensile damage evolutions are established based on a Helmholtz free energy function. Within the return-mapping damage algorithm, the required variable fields, such as the damage variables and the displacement field, are obtained. This study uses the Newton–Raphson nonlinear solution algorithm to achieve the nonlinear damage solution. The verification, where the performance is assessed, of the proposed model is demonstrated by relevant numerical examples available in the literature.

Compact tension fracture specimen: Experimental and computational implementations on stress intensity factor

This work concentrates on the characterization of the stress intensity factor range for a compact tension specimen tested under a uniaxial tensile fatigue loading condition. The experimental solution is obtained using a three-dimensional full-field optical technique, digital image correlation. The deformation field is measured and documented for distinct crack lengths. As a relevant fracture parameter, stress intensity factor is thus experimentally measured combined with a computational overdeterministic algorithm for different crack lengths. Moreover, to verify the performance of the proposed fracture model, the cracked compact tension specimen is elasto-statically resolved using advanced discretization techniques, such as the finite element method, the meshless radial point interpolation method and the meshless natural neighbour radial point interpolation method. The finite element method model is thereby analysed with ABAQUS© to enable computation of mode I stress intensity factor results based on strain energy release rate criterion for different crack measurements in addition to strain contours. Likewise, the resolution pattern is repeated for meshless methods, and analogous numerical solutions are thus obtained. Overall, the experimental and numerical stress intensity factor results are compared with an available solution (ASTM E647) exhibiting a reasonable agreement. The novelty of this investigation is the amalgamation of an experimental digital image correlation procedure with a computational overdeterministic algorithm and, most importantly, the meshless formulation performance in the linear elastic fracture mechanics.

Advanced image based methods for structural integrity monitoring: Review and prospects

There is a growing trend in engineering to develop methods for structural integrity monitoring and characterization of in-service mechanical behaviour of components. The fast growth in recent years of image processing techniques and image-based sensing for experimental mechanics, brought about a paradigm change in phenomena sensing. Hence, several widely applicable optical approaches are playing a significant role in support of experiment. The current review manuscript describes advanced image based methods for structural integrity monitoring, and focuses on methods such as Digital Image Correlation (DIC), Thermoelastic Stress Analysis (TSA), Electronic Speckle Pattern Interferometry (ESPI) and Speckle Pattern Shearing Interferometry (Shearography). These non-contact full-field techniques rely on intensive image processing methods to measure mechanical behaviour, and evolve even as reviews such as this are being written, which justifies a special effort to keep abreast of this progress.There is a growing trend in engineering to develop methods for structural integrity monitoring and characterization of in-service mechanical behaviour of components. The fast growth in recent years of image processing techniques and image-based sensing for experimental mechanics, brought about a paradigm change in phenomena sensing. Hence, several widely applicable optical approaches are playing a significant role in support of experiment. The current review manuscript describes advanced image based methods for structural integrity monitoring, and focuses on methods such as Digital Image Correlation (DIC), Thermoelastic Stress Analysis (TSA), Electronic Speckle Pattern Interferometry (ESPI) and Speckle Pattern Shearing Interferometry (Shearography). These non-contact full-field techniques rely on intensive image processing methods to measure mechanical behaviour, and evolve even as reviews such as this are being written, which justifies a special effort to keep abreast of this progress.

A nonlinear simulation of a bi-failure specimen through improved discretisation methods: A validation study

A robust and efficient scheme is rendered to elastoplastically study the material nonlinearity of structural components. In this investigation, a specimen manufactured from the aluminium alloy AA6061-T6 is considered. It is mechanically loaded under a uniaxial tensile state and the experimental strain datum is analysed by three-dimensional digital image correlation. Due to specific specimen geometry, complex stress states will occur. However, the specimen yields due to an approximated uniaxial stress state. The obtained remote stress/strain from experimental data is used to validate the computational solutions using advanced discretisation approaches. Therefore, as a preliminary numerical study, the model is simulated through the finite element method formulation. Afterwards, another numerical strategy is adopted – the radial point interpolation method. The Newton–Raphson initial stiffness method is thereby adapted to complete the nonlinear solutions algorithm. Furthermore, the elastoplastic demeanour of aluminium alloys is determined with the von Mises yield criterion, an isotropic hardening rule and an associative flow rule. Obtained computational results fit the experimental digital image correlation solution, which allow to conclude that the proposed meshless methodology is efficient and reliable.