External surface cracks in shells under cyclic internal pressure

The stress analysis and fatigue crack growth behaviour of a part‐through‐cracked double‐curvature thin‐walled shell is examined. An external surface crack is assumed to lie in one of the principal curvature planes of the shell, and to present a semi‐elliptical shape. The stress intensity factors (SIFs) along the crack front for different elementary opening stresses acting on the crack faces are determined through a three‐dimensional finite element analysis. Then approximate values of SIF in the case of a cracked pressure vessel are computed by employing the above results together with the superposition principle and the power series expansion of the actual opening stress. Finally, a numerical simulation procedure is carried out to predict the crack growth under cyclic internal pressure. Some results are compared with those of other authors.     

Dietary intakes in infertile women a pilot study

Background  

The reproductive axis is closely linked to nutritional status. The purpose of this study was to compare the nutritional status in two groups of young infertile women, without clinically overt eating disorders: hypothalamic amenorrhea (HA) and polycystic ovary syndrome (PCOS).     

Notched shells with surface cracks under complex loading

In the present paper, a double-curvature thin-walled shell with a circular-arc notch is considered. For different notch configurations, the stress-intensity factor (SIF) along the front of an elliptical-arc surface crack at the notch root is computed through a three-dimensional finite element analysis, for seven elementary stress distributions perpendicular to the crack faces. Then, by employing such results, an approximate expression of SIF in the case of a generic complex loading is determined by means of the power series expansion of the actual stress field and the superposition principle. Finally, as an example of how to apply the above numerical procedure, the effect of the stress concentration on the SIF values is examined for both cylindrical and spherical notched shells under an internal pressure.     

Climbing the city. Inhabiting verticality outside of comfort bubbles

Over the last couple of decades, urban sports have been studied – as well as, in many cases, celebrated – as critical forms of using urban space. Urban climbing, a practice also known as “street bouldering,” “buildering,” “structuring,” and “stegophilia,” has been much explored in this vein. While we acknowledge the importance of bringing to light the political and playful dimensions of the urban spatial experience, in this piece we would like to focus on a slightly different question. We approach it as a powerful means to probe and understand the finest constitution of urban environments and, more amply, urban morphology. By doing so, we wish, on the one hand, to zoom in as closely as possible onto the actual bodily practice of climbing, and, on the other, to attend its methodological implications in terms of a reflection on bodily techniques in the context of a natural history of the city. We describe urban climbing as a peculiar corporeal operation carried out at and, more precisely, on the limits of environmental control. In conclusion, the article suggests that, by highlighting the meaning of inhabiting a vertical open space of a peculiar kind, a close-up study of urban climbing might help to develop contemporary urban theory.     

Size effect in beams with rounded-tip V-notch

Stresses and strains in a beam with a single-edge rounded-tip V-notch subjected to bending were analyzed by the method of finite elements by using nonconforming quadrilateral elements under the assumption that the material is linearly elastic. We studied the influence of the depth of the notcha, its radius of curvature ρ, the angle of the notch ω, and the height of the beamh on the stress intensity factorK _t . It is established that the relative depth of the notch ζ=a/h causes practically no influence if the notch angle ω lies within the range 0°–135°. The influence of the notch rapidly weakens as the relative radius of curvature ρ _d =ρ/h increases from 0.01 to 1.0 and becomes insignificant for ρ _d ≤ 1. For small ρ _d (ρ _d ≤ 1), the quantityK _t attains its maximum value provided that ζ lies within the range 0.1–0.3. As the height of the beam increases, the quantityK _t first remains practically constant, then increases, and finally, ash infinitely increases, approaches a certain constant value. Dipartimento di Ingegneria Civile, Universita di Parma Viale delle Scienze, 43100 Parma, Italy. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No. 3, pp. 73–79, May–June, 1996.     

Dual predetection SC diversity reception of TCM-MPSK signals overNakagami fading channels

Space diversity reception and forward error correction coding are powerful techniques for combatting multipath fading encountered in mobile radio communications. The authors analyse the performance of a dual predetection selection combining (SC) diversity system using trellis coded modulation-multiple phase shift keying (TCM-MPSK) on slow, nonselective correlated Nakagami fading channels. An alternative exact derivation for the pairwise error probability, used in calculating average bit error rate analytical upper bounds, is introduced     

Influence of a central straight crack on the buckling behaviour of thin plates under tension,compression or shear loading

Thin-walled structural components, such as plates and shells, are used in several aerospace, naval, nuclear power plant, pressure vessels, mechanical and civil structures. Due to their high slenderness, the safety assessment of such structural components requires to carefully assess the buckling collapse which can strongly limit their bearing capacity. For very thin plate, buckling collapse can occur under shear, compression or even under tension. In the latter case, fracture or plastic failure can also take place instead of elastic instability. In the present paper, the effects of a central straight crack on the buckling collapse of rectangular elastic thin-plates—characterized by different boundary conditions, crack length and orientation—under compression, tension or shear loading are analysed. Accurate FE numerical parametric analyses have been performed to get the critical load multipliers in such loading cases. Moreover the effect of crack faces contact is examined and discussed. Some useful conclusions related to the sensitivity to cracks of the buckling loads for thin plates, especially in the case of shear stresses, are drawn. Cracked plates under tension are finally considered in order to determine the most probable collapse mechanism among fracture, plastic flow or buckling and some failure-type maps are determined.