Numerical analysis of stress intensity factor and t-stress in pipeline of steel p264gh submitted to loading conditions

Stress singularities occur at crack tips, corners and material interfaces. The stress intensi-ty factors and T-stresses are coefficients of structural components where the active stress singular and first regular stress terms, respectively, are denoted by William's eigen function expansion series. A finite element analysis by CASTEM 2000 have been undertaken in order to determine the evolution of the T-stress and stress intensity factor terms in mode I for an arc of pipeline specimens with an external surface crack. A stress difference method described by Moustabchir et al. (2012) are adapted and, in the following step, the volumetric method is then embedded to compute the SIFs and T-stress near the crack tip. Different crack geometries combined with different length-to-thickness ratios are examined for the T-stress and stress-intensity factor. The revisited stress difference method employed here shows to be an accurate and robust scheme for evaluating the T-stress/SIFs in an arc of the pipeline

Modeling and experimental analysis of polypropylene honeycomb multi-layer sandwich composites under four-point bending

The behavior of a simple and innovative multi-layer sandwich panels having a polypropylene honeycomb core has been investigated carefully, theoretically and experimentally. A four-point bending test was performed to detect the mechanical characteristics of the multi-layer core. The experimental results emphasize a better rigidity of the multi-layer structure compared to the weakness displayed by the single-layer configuration. In fact, a small increase in the final weight of the component leads to a significant increase of the mechanical properties. In the second part of this study, analytical and numerical homogenization approaches were developed to compute the effective properties of the single polypropylene honeycomb core. The numerical model complies with the experimental protocol, and the simulation conducted is aiming to reproduce a typical four-point bending test on a polypropylene honeycomb multi-layer sandwich panel. Both numerical and experimental results are presented in details and a good correlation between them is highlighted

Mean-Field Description of Fusion Barriers with Skyrme's Interaction

Fusion barriers are determined in the framework of the Skyrme energy-density functional together with the semi-classical approach known as the Extended Thomas-Fermi method. The barriers obtained in this way with the Skyrme interaction SkM* turn out to be close to those generated by phenomenological models like those using the proximity potentials. It is also shown that the location and the structure of the fusion barrier in the vicinity of its maximum and beyond can be quite accurately described by a simple analytical form depending only on the masses and the relative isospin of target and projectile nucleus.Comment: 7 pages, latex, 5 figure

Fission of actinides through quasimolecular shapes

International audienceThe potential energy of heavy nuclei has been calculated in the quasimolecular shape path from a generalized liquid drop model including the proximity energy, the charge and mass asymmetries and the microscopic corrections. The potential barriers are multiple-humped. The second maximum is the saddle-point. It corresponds to the transition from compact one-body shapes with a deep neck to two touching ellipsoids. The scission point lies at the end of an energy plateau well below the saddle-point and where the effects of the nuclear attractive forces between two separated fragments vanish. The energy on this plateau is the sum of the kinetic and excitation energies of the fragments. The shell and pairing corrections play an essential role to select the most probable fission path. The potential barrier heights agree with the experimental data and the theoretical half-lives follow the trend of the experimental values. A third peak and a shallow third minimum appear in asymmetric decay paths when one fragment is close to a double magic quasi-spherical nucleus, while the smaller one changes from oblate to prolate shapes

Numerical Study of the Bond Strength Evolution of Corroded Reinforcement in Concrete in Pull‐Out Tests

The corrosion of rebars in reinforced concrete structures impacts their geometry (diameter and ribs) and mass, damages the concrete at the interface between the two materials, deteriorates the bond strength, and causes the cracking of the concrete cover. In the following study, a 2D numerical model of the pull‐out test is presented in order to study the impact of corrosion on the bond strength. Several parameters are investigated: the embedment depth, the rebar’s diameter, and the width of the concrete cover. The model reproduces the slip of the rebar and the failure through the splitting of concrete. It integrates an interface between the two materials and a concrete damage model that simulate the deterioration of concrete in compression and tension. The results obtained are validated with experimental data from the literature. Moreover, a parametric study is carried out to determine the impact of the embedment depth, the diameter of the rebar, and the concrete cover on the bond strength. The present study confirms that a greater embedment depth increases the pulling load. The study also confirms that the rebar’s diameter impacts highly the loss of bond between the rebar and the concrete cover. Lastly, the final main result of this paper is that the width of the concrete cover slows the loss of bond strength between the two materials