Thermoelastic investigations for fatigue life assessment

An investigation is presented on the suitability and accuracy of a thermoelastic technique for the analysis of fatigue cracks. The stress intensity factor ranges ΔKI and ΔKII are determined from thermoelastic data recorded from around the tip of a sharp slot in a steel specimen under biaxial load, in order to assess the accuracy of the technique. ΔKI and ΔK II are determined to within 4% and 9% of a theoretical prediction, respectively. The results from a similar test on a fatigue crack under biaxial load are also presented. These show that thermoelastic stress analysis is a rapid and accurate way of analyzing mixed-mode fatigue cracks. A discussion is given on the potential of thermoelastic stress analysis of propagating cracks

Asymptotic stress field at the tip of an inclined crack terminating to an interface

This paper presents the numerical results for the asymptotic stress field and the fracture parameters at the tip of an inclined cracks terminating to a bi-material ceramic interface. The numerical analysis was carried out using FRANC2D/L fracture analysis code. A biaxial specimen was modeled for producing different mixed mode loads and two materials combinations of Al2O3 and ZrO2 were considered. The influence of the material combination and applied mixed mode load on the singularity orders, stress distributions and stress intensity factors is highlighted.This paper presents the numerical results for the asymptotic stress field and the fracture parameters at the tip of an inclined cracks terminating to a bi-material ceramic interface. The numerical analysis was carried out using FRANC2D/L fracture analysis code. A biaxial specimen was modeled for producing different mixed mode loads and two materials combinations of Al2O3 and ZrO2 were considered. The influence of the material combination and applied mixed mode load on the singularity orders, stress distributions and stress intensity factors is highlighted

A review of using thermoelasticity for structural integrity assessment

The advances in the use of thermoelastic stress analysis (TSA) for fracture mechanics assessment are reviewed. The development of techniques to determine stress intensity factor is presented followed by the application of these techniques to fatigue crack growth, crack closure and the study of mixed mode cracks

A review of using thermoelasticity for structural integrity assessment

The advances in the use of thermoelastic stress analysis (TSA) for fracture mechanics assessmentare reviewed. The development of techniques to determine stress intensity factor is presented followed by theapplication of these techniques to fatigue crack growth, crack closure and the study of mixed mode cracks

Analysis of Printed Circuit Boards strains using finite element analysis and digital image correlation

This paper investigates the use of digital image correlation (DIC) and finite element analysis for strain measurement on Printed Board Circuits (PCBs). Circuit boards (PCBs) are designed to mechanically support and electrically connect an electronic component assembly. Due to screw assemblies, the surface level differences on which the PCB is placed, the process of assembling the electronic components induces a certain state of stress and deformation in the PCB. The main components affected are microprocessors due to the way they are glued to PCBs with BGA - Ball grid arrays (BGA). Digital Image Correlation (DIC) is a full-field contactless optical method for measuring displacements and strain in experimental testing, based on the correlation of images taken during test. The experimental setup is realized with Dantec Q-400 system used for image capture and Istra 4D software for image correlations and data analyses. The maximum level of the obtained strain is compared with the allowable limit. Finite element analysis (FEA) is a numerical method of analysis for stresses and strain in structures of any given geometry

Experimental and numerical investigations of the influence of real cracks on chloride ingress in concrete

oproti online verzi posunuté stránkováníExperimental and numerical results of a chloride ingress study conducted on samples drilled from different locations of a reinforced concrete slab, previously loaded until failure, are presented. The experimental part was carried on following the NT Build 492 standard for the non-steady state migration test, then a 3D model was developed using the Abaqus/Standard software based on the FEM in order to simulate chloride ingress in both uncracked and cracked concrete

Fracture parameters determination of polyurethane materials for application of SED criteria to notched components

AbstractLocal Strain Energy Density represents an engineering approach for assessing the brittle fracture of cracked and notched components. Experimental determination of fracture parameters (critical value of deformation energy Wc in a local finite volume around the notch tip and the radius of the control volume Rc) represents a key issue. The paper presents a methodology to determine these parameters using a notched tensile specimen. The obtained values will be used to predict the fracture for different types of notches and cracked specimens under mode I; for cracked specimens under mixed mode and mode II has proposed a new approach which confirms that PUR foams can be treated as brittle materials. The considered specimens are made of rigid polyurethane foams having different densities from 100 to 651 kg/m3

Finite Fracture Mechanics and Cohesive Crack Model: Size effects through a unified formulation

Finite Fracture Mechanics and Cohesive Crack Model can effectively predict the strength of plain, cracked or notched structural components, overcoming the classical drawbacks of Linear Elastic Fracture Mechanics. Aim of the present work is to investigate size effects by expressing each model as a unified system of two equations, describing a stress requirement and the energy balance, respectively. Brittle crack onset in two different structural configurations is considered: (i) a circular hole in a tensile slab; (ii) an un-notched beam under pure bending. The study is performed through a semi-analytical parametric approach. Finally, theoretical strength predictions are validated with experimental results available in the literature for both geometries, and with estimations by the point criterion in the framework of Theory of Critical Distances