Stress intensity solutions for cracked plates by the dual boundary method

This paper presents the application o f the dual boundary element method for the determination o f stress intensity factors in plate bending problems. The loadings considered include internal pressure, and also combined bending and tension. Mixed mode stress intensity factors are evaluated by a crack surface displacement extrapolation technique and the J-integral technique. The boundary element results for the case studies considered in the paper have been compared with either analytical or finite element results and in all cases good agreement has been achieved.Описано застосування методу подвійних граничних елементів для визначення коефіцієнтів інтенсивності напружень у задачах, що пов’язані зі згином пластин. Умови навантаження включають внутрішній тиск та комбінацію згину з розтягом. Коефіцієнти інтенсивності напружень для змішаних мод оцінюються за допомогою методу екстраполяції переміщення поверхні тріщини та методу J-інтеграла. Результати розрахунків методом граничних елементів для досліджуваних випадків навантаження порівнюються із даними аналітичних чи скінченноелементних розрахунків. Отримано їх хорошу збіжність.Описано применение метода двойных граничных элементов для определения коэффициентов интенсивности напряжений в задачах, связанных с изгибом пластин. Исследуемые условия нагружения включают внутреннее давление и комбинацию изгиба с растяжением. Коэффициенты интенсивности напряжений для смешанных мод оцениваются с помощью метода экстраполяции перемещения поверхности трещины и метода J-интеграла. Результаты расчетов методом граничных элементов, полученные для рассматриваемых случаев нагружения, сравниваются с данными аналитических или конечноэлементных расчетов. Получено их хорошее соответствие

Stress intensity solutions for cracked orthotropic plates

In this paper, fracture mechanics in orthotropic plates, stress and displacement distributions around the crack tip in an anisotropic material are considered. Classical displacement based finite elements, elements with penalized equilibrium and elements with drilling degrees of freedom are employed. The path independent integrals J and I* are applied to orthotropic fracture mechanics problems to determine the stress intensity factor at the crack tip. Again, convergence studies are done, and the path independence of J and I* are investigated for orthotropic problems. Numerical results for typical fracture specimens are presented and discussed. The effect of the degree of anisotropy and fiber orientation on the stress intensity factor is also demonstrated

Effects of variation of material properties on the stress intensity factors of cracked anisotropic bodies

This paper presents a two-dimensional parametric study of the behavior of uniformly cooled homogeneous linear elastic anisotropic bodies containing cracks using the boundary element method (BEM). The present work investigates the effects of varying material properties, and varying orientation of these material properties, on the magnitude of the stress intensity factors (SIFs) of the cracked bodies. Three cracked plate geometries are considered in this study, namely: (1) a plate with an edge-crack; (2) a plate with a double edge-crack; (3) a plate with symmetric cracks emanating from a central hole. Where appropriate, finite element method (FEM) analyses are also performed in order to validate the results of the BEM analysis. The results of this study show that, for all crack geometries, the mode-I stress intensity factor, \hbox{$K_{{\rm I}}^{{\ast }}$} decreases as the anisotropy of the material properties is increased. Additionally, for all these cases, \hbox{$K_{{\rm I}}^{{\ast }}$} decreases as the angle of orientation of the material properties, θ, increases with respect to the horizontal axis. The results also show that BEM is an accurate and efficient method for two-dimensional thermoelastic fracture mechanics analysis of cracked anisotropic bodies

Mechanical characterization of an epoxy panel reinforced by date palm petiole particle

The past years were marked by an increase in the use of wood waste in civil and mechanical constructions. Date palm waste remains also one of the most solicited renewable and recyclable natural resources in the composition of composite materials. In Algeria, a great amount of this type of plant wastes accumulates every year. In order to make use of this waste, a new wood-epoxy composite material based on date palm petiole particleboard is developed. It makes use of date palm petiole particleboard as reinforcement and epoxy resin as matrix. The size of the particles reinforcement are between 1 similar to 3 mm and proportion of reinforcement used is 37%. In this work, experimental and numerical studies are conducted in order to characterize the wood fibre-epoxy plates. Firstly, experimental modal analysis test was carried out to determine Young's modulus of the elaborated material. Then, in order to validate the results, compression test was conducted. Furthermore, additional information about the shear modulus of this material is obtained by performing an experimental modal analysis to extract the first torsional mode. Moreover, a finite element model is developed using ANSYS software to simulate the vibration behaviour of the plates. The results show a good agreement with the experimental modal analysis, which confirms the values of Young's modulus and shear modulus

Improved ANN technique combined with Jaya algorithm for crack identification in plates using XIGA and experimental analysis

This paper presents an effective method for crack identification to improve the training of Artificial Neural Networks (ANN) parameters using Jaya algorithm. Dynamic and static datasets are introduced using eXtended IsoGeometric Analysis (XIGA) to improve the accuracy of the proposed application based on the frequency and strain measurements. Based on the concept used in our previous works, XIGA provided more accurate results for fracture mechanics applications than other modelling techniques. Therefore, XIGA datasets of cracked plate are used to improve ANN technique for static and dynamic analyses. Model updating of the cracked plate is considered by introducing the mass of accelerometers and identifying Young's modulus of the plate and stiffness of springs using Jaya algorithm. The difference between measured and calculated frequencies is used as an objective function to calibrate the XIGA model. The crack length is predicted using an adaptive approach without any previous knowledge based on the data provided from a numerical model. Jaya algorithm is used to optimize the most important parameters of ANN. Several numerical examples with different crack scenarios and different boundary conditions are studied in order to evaluate the proposed approach. The results show that the proposed application is able to predict all considered scenarios and accurately identify the crack length. Experimental data of cracked plates are used to validate the numerical predictions. Hence, this application is found to be robust and accurate for crack identification in plates

An efficient hybrid TLBO-PSO-ANN for fast damage identification in steel beam structures using IGA

The existence of damages in structures causes changes in the physical properties by reducing the modal parameters. In this paper, we develop a two-stages approach based on normalized Modal Strain Energy Damage Indicator (nMSEDI) for quick applications to predict the location of damage. A two-dimensional IsoGeometric Analysis (2D-IGA), Machine Learning Algorithm (MLA) and optimization techniques are combined to create a new tool. In the first stage, we introduce a modified damage identification technique based on frequencies using nMSEDI to locate the potential of damaged elements. In the second stage, after eliminating the healthy elements, the damage index values from nMSEDI are considered as input in the damage quantification algorithm. The hybrid of Teaching-Learning-Based Optimization (TLBO) with Artificial Neural Network (ANN) and Particle Swarm Optimization (PSO) are used along with nMSEDI. The objective of TLBO is to estimate the parameters of PSO-ANN to find a good training based on actual damage and estimated damage. The IGA model is updated using experimental results based on stiffness and mass matrix using the difference between calculated and measured frequencies as objective function. The feasibility and efficiency of nMSEDI-PSO-ANN after finding the best parameters by TLBO are demonstrated through the comparison with nMSEDI-IGA for different scenarios. The result of the analyses indicates that the proposed approach can be used to determine correctly the severity of damage in beam structures