Key Engineering Materials Vol. 820

Abstract: Hydroxyapatite-Alumina composite powders, HAP-Al₂O₃, for biomedical applications were synthesized by neutralization method. Composites with different alumina content were prepared and calcined over the temperature range of 900-1300°C for 3 h. Effects of alumina content and calcination on the structural properties of powders were studied. The as-received powders and ceramics were characterized by various techniques (XRD, IR, SEM, TEM). Compressive strength of ceramics was determined using direct compressing. Results indicate that both crystallinity of the HAp-Al₂O₃ powders and the compressive strength increased with the temperature of calcination, but depending of the alumina content where the formation of β-TCP phase as secondary phase is detected after heat treatment. We notice that HAp-10Al₂O₃ offers the best mechanical strengths that can be improved by a high calcination temperature.

Abstract: The cables are widely used in mechanical, electrical and civil engineering applications, as they are flexible and highly resistant. In this paper, the behavior of the elastic limit of straight central core strands is studied. In this study, we focus on the elastic limit’s behavior of straight central core strands. That is, we investigate 27 cores with different configurations. They generally consist of 7 wires (1+6) belonging to wire ropes of type 19x7 subjected to static axial loads. The numerical study is performed using finite element method (FEM). The main results are compared with experimental data. Finally, to determinate the impact of three parameters: the basic material constituting the strands, the winding angle of wires and the diameter of strands on the yield strength of the core strands, we apply a design of experiments (DOE) analysis by YATES’ method.

Abstract: The present work deals with the analytical resolution of the problem of viscoelastic coated inclusion embedded in a viscoelastic matrix.In a first step, we will study the problem of a linear viscoelastic inclusion, without coating, embedded in a linear viscoelastic matrix.Then, the problem of coated viscoelastic inclusion considering the coating as a thin layer whose viscoelastic properties are different from those of the inclusion and the matrix is performed.The resolution of this problem will be based simultaneously on the Green function technique as well as the interface operator. The analytical expression of the solution is obtained by assuming the isotropy of the matrix as well as the spherical shape of the coatedinclusion.These results are used to determine the effective properties of a heterogeneous medium from a self-consistent approach taking into accountthe interactions between coated inclusions and the equivalent homogeneous medium.

Abstract: In this article, the effect of particle shape is examined from the comparison of results of numerically simulated constant volume compression tests carried out on planes assemblies of disks and ellipses with equal porosity and similar gradation and test conditions. The results show that particle shape is a decisive fabric component that contributes directly and indirectly to the strength of assemblies of particles to resist shearing deformation. The results confirm previously established facts that elongated particle shapes favour particle interlocking and create, more easily than ideal spheres, stable clusters of particles through which external loads can be transferred hence resisting higher shearing stresses.

Abstract: In this paper we are studying the effects of temperatures ranging from-10 to 70°C of behavior on chlorinated PVC (CPVC), whose direct consequences are the strong modifications of the mechanical and physical characteristics of this polymer [1]. The purpose of this paper is to predict the damage of non-weld CPVC, based on simple tensile tests on non weld specimens. Thereafter and with the establishment of the relation Damage-Reliability, the critical life fraction βc is identified that predicts the time at which the damage becomes sudden and it is necessary to calculate the reliability and predictive maintenance of the system.

Abstract: In this paper, we are dealing with the study of the mechanical behavior of an amorphous polymer, acrylonitrile butadiene styrene "ABS". In fact, uniaxial tensile tests on rectangular specimens containing a combined defect, with simple and double notches, has been done. The proposed approach develop a method, based on energy parameter, to calculate the evolution of damage over the materials’ life. This method can be used to predict quantitatively the risk of sudden rupture in a structure. Therefore, the damage evaluation based on the residual energy method was compared to the unified theory one for different loading levels. The prediction of damage by experimental models has led to the determination of the three stages of damage evolution, which are the initiation, propagation and complete deterioration of the material. Thus, the concept of reliability is used to specify the critical life fraction, which is similar to the notch depth (βc) of a modeled defect as a combined defect on an ABS sample. In addition, the unified theory was used in this work, to define on the one hand, the parameter of damage which is the internal variable which describes the failure level of the structure in function of life fraction, on the other hand, for the theoretical evaluation of the level of damage. Finally, we have proved that the theoretical and experimental results show a good agreement.

Abstract: In this work, we study the influence of temperature on the mechanical behavior of an amorphous polymer, acrylonitrile butadiene styrene "ABS", based on a series of uniaxial tensile tests on smooth specimens at different temperatures.The results obtained show that the failure of the studied material (ABS) depends strongly on the temperature. Indeed, two zones have been identified: industrial zone T<Tg and thermoforming zone T>Tg (Tg is the glass transition temperature of ABS material).In the industrial zone, we conducted a study of the experimental and theoretical damage via the model of the unified theory. The comparison showed a good agreement concerning the acceleration of the damage process as the temperature increases. In the thermoforming zone, we adopted the same methods to follow the process of flow as a function of the temperature increase. Likewise, we compared theoretical and experimental values which in turn showed a good match. Different stages have been determined in each separate zone, that allows to predict the moment of the critical damage or flow and therefore to intervene in time for a predictive maintenance.

Abstract: This paper deals with the analyzing and comparing the thermal performance of heat dissipation system and other components in the design of E3D liquefier using Finite Element Modeling (FEM) for three different filaments namely Polycaprolactone (PCL), polylactic acid (PLA) and Acrylonitrile Butadiene Styrene(ABS). This work evaluates the influence of airflow generated by means of a fan coupled to the extruder. The printable materials are also taken as variable in this investigation. The heating process should ensure the balance between proper heating of the material and controlling the temperature along the extruding body, so it reaches above 140 degrees in function of raw material on the tip of the nozzle and must be lower at the top of the liquefier for the correct perseveration of the 3D printer and its durability.

Abstract: The Chlorinated Polyvinyl Chloride pipes used for the supply of cold and hot water are designed and manufactured for a 50 years predictive life, but defects and harmfulness may occur during the transport process, storage and operation of tubes that significantly affect these forecasts. This work deals with the study of the mechanical behavior of Chlorinated Polyvinyl Chloride (CVPC) specimens subjected to tensile tests under the effect of temperature. Moreover, a study of damage evolution by the ultimate energy makes it possible to determine the three stages of the lifetime of the test pieces studied. On the basis of the stress-strain variation curves plotted from the experimental results, the critical value of the fraction of life corresponding to the acceleration of the damage was determined.

Abstract: Evaluating the integrity of a structure consists in proving its ability to realize its mechanical functions for all modes of loading, normal or accidental, and throughout its lifetime. In the context of nuclear safety, the most important structures consider the presence of a degradation grouping several aspects, such as cracks. In this context, the fracture mechanics provide the tools needed to analyze cracked components. Its purpose is to establish break criteria for judging loading margins in normal or accidental operating conditions. The seismic load is one of the dominant loads for the failure assessment of the pipes. Its probabilistic dispersion, however, was not taken into account in the past probabilistic fracture mechanics analysis. The objective of this paper is to simulate and analyze the effect of abnormal stress on the reliability of tow pipe sizes. As result the seismic stress has more effect on the break probability, but not for the leak probability. In the case without a seismic load, the break probability is mainly dominated by an initial crack size. The earthquake has much effect on the break probability for the large diameter pipe, not for the small diameter pipe. In the large diameter pipe, the break probability increases gradually with the time. The leak probability of both pipe sizes is not affected by the seismic curve.