1,721,005 research outputs found
Branch points, Fourier integrals and Pompeiu problem
No full textLet h be the square root of a polynomial and assume thath is univalent on the unitary disk of the complex plane. Then the set Ω=h(D) has the Pompeiu property
The Stress Intensity Factor of convex embedded polygonal cracks
No full textIn the present work, a simple formula for the evaluation of the stress intensity factor (SIF) of convex embedded polygonal cracks has been proposed. This formula is structured as a correction factor of the Oore-Burns’ equation and is based on accurate three-dimensional FE analysis. Furthermore, a precise formula for a regular polygonal crack has been given
A closed form for the stress intensity factor of a small embedded square-like flaw
No full textIn the present work, the stress intensity factor (SIF) of a small embedded square-like flaw is calculated by means of a procedure based on the Oore-Burns integral. An explicit equation is given to evaluate the SIF along the two axes of symmetry that correspond to the points where the SIF takes its maximum and minimum value on the contour crack. The SIF is calculated in accordance with FE numerical results
Stress intensity factors of elliptical cracks at the weld toe
No full textThe paper takes into account the assessment of the stress intensity factor (SIF) of defects similar to elliptical cracks located at the weld toe. By assuming a second order approximation of the Oore-Burns equations the SIF has been evaluated with simplified equations. The analytical results are compared with those evaluated by means of the finite elements method. As an example, the SIF is calculated for a defect located in the neighborhood of the weld toe of full penetration cruciform joints under mode I loadin
Stress intensity factor for small embedded cracks in weldments
No full textIn the present work, the stress intensity factor (SIF) of embedded small cracks placed at the weld toe is calculated by means of two procedures based on the Oore-Burns integral. In the first approach, the defect is considered as a circular disk and the SIF is evaluated by means of the Oore- Burns weight function. By taking advantage of a suitable change of variable, the singularity of the weight function on the crack border can be removed. In this way, the numerical evaluation of the SIF is possible without the use of specific integration algorithms, although the nominal stress field becomes singular when the crack approaches a V-sharpe notch. As an example, the obtained equations are applied to a defect located in the neighbourhood of a weld toe with an opening angle of 135 degrees under mode I loading. Subsequently, for a crack similar to a star domain with a border expressed by means of the Fourier series, the SIF is given by means of an explicit equation based on the Oore-Burns weight function
Asymptotic behaviour of the Oore-Burns integral for cracks with a corner and correction formulae for embedded convex defects
No full textIn this paper, the asymptotic behaviour of the stress intensity factor (SIF) near a corner of a crack is discussed. The weight function of Oore-Burns and FE analysis are used in order to explain the trend of the SIF. The analytical analysis shows that the SIF at the corner has a cusp behaviour as a function of the distance from the corner. This is a crucial mathematical property obtained from the Oore-Burns integral. Explicit formulae for the estimation of the SIF are obtained for square and equilateral triangular cracks. Then, the value of the SIF along the crack border is corrected (quantitative intervention) by means of a new simple formulation that is able to considerably increase the accuracy of the Oore-Burns integral. Finally, in the case of a crack with a rounded corner, a new simple correction formula is given and, in order to check the accuracy of the proposed equations, a comparison is carefully made with an FE analysis as well as with numerical results taken from the literature
Fatigue crack propagation of planar three-dimensional cracks
No full textIn this paper the Fourier series is used to evaluate mode I Stress Intensity Factors (SIF) in three-dimensional planar flaws based on a distortion transformation of a reference disc. Under the hypothesis of an isolated crack, the SIF at each point of the crack border is calculated to assess the crack shape after propagation according to the crack growth rate equation of Paris and Erdogan. The contour is moved along the outward normal to the crack shape. Many examples are proposed with the aim of predicting the final shape of different types of embedded planar flaws
How two management engineers and a simulation software can support the organization of a new surgical pre-admission unit
No full textWe report a practical experience in a working hospital. Every surgical operation is preceded by a pre-admission process, destined to analyze patients conditions, which involves many different departments beside the one executing the operation. We started from an organization which provided independent processes for every surgical department, which asked elsewhere for inspections and consulting. A transformation was effected, by designing a new unit which manages a centralized process, utilized by all surgical departments, where all other interested departments, services or units work together in synchrony. That permits to save time and movements of patients inside the hospital, and to reduce total pre-admission times, thus obtaining a better utilization of hospital resources. In order to rule a transformation which required the collaboration of many different groups independently operating before, an accurate design and management control was operated by simulation. After a quantitative analysis of process phases, a new model was built and coded in language Arena. The model evidenced critical aspects suggested useful modifications and adaptations which permitted to get a better working. We think the experience from a specific case may be easily extended to other similar ones
Analytic evaluation of the difference between Oore-Burns and Irwin stress intensity factor for elliptical cracks
No full textThe mode-I weight function proposed by Oore and Burns is an efficient and empirical mathematical relationship capable of estimating the Stress Intensity Factor in the presence of a generic planar flaw. In the case of penny shaped cracks or tunnel cracks the Oore-Burns equation provides the classic analytical expressions. In this paper, the authors prove analytically that the Oore-Burns equation is not the weight function for an ellipse in an infinite solid under traction loading. The absolute novelty is given by the analytic evaluation between the Oore-Burns integral and the Irwin solution in terms of an algebraic expression, which is independent from any numerical procedures for an ellipse close to a circle
An approximation in closed form for the integral of Oore-Burns for cracks similar to a star domain
No full textIn this paper, we give an explicit new formulation for the three-dimensional mode I weight function of Oore-Burns in the case where the crack border agrees with a star domain. Analysis in the complex field allows us to establish the asymptotic behaviour of the Riemann sums of the Oore-Burns integral in terms of the Fourier expansion of the crack border. The new approach gives remarkable accuracy in the computation of the Oore-Burns integral with the advantage of reducing the size of the mesh. Furthermore, the asymptotic behaviour of the stress intensity factor at the tip of an elliptical crack subjected to uniform tensile stress is carefully evaluated. The obtained analytical equation shows that the error of the Oore-Burns integral tends to zero when the ratio between the ellipse axes tends to zero as further confirmation of its goodness of fit
- …
