Key Engineering Materials Vol. 820

Abstract: Composite materials offer potential avenues for tailoring materials with desired properties intended to innovative applications. To speed up this scheme, trial and error practice is evolving to a more rational and organized material design process. This trend depends on our ability to bridge the micro-scale to the system level. An important brick of this process is constituted of micromechanical models that bridge the gap between micro and macro scales in materials. Unfortunately, to forecast the behavior of complex composite materials microstructures, these models remain rudimentary, particularly for the nonlinear regime. Accordingly, our ambition is to highlight the limitations of existing micromechanical models and examine their respective capabilities to predict elastoplastic behavior of composite materials. The assessment reveals that in order to reduce the disparity between micromechanical models predictions and corresponding numerical or experimental results, new robust and efficient micromechanical models are needed. These models have to accurately describe different interactions in the composite and deal with multiphase and two-phase composites with high volume fractions under different loading paths.

Abstract: This chapter describes the cracking of stainless steel piping under Inter-granular Stress Corrosion Cracking (IGSCC) conditions using probabilistic fracture mechanics that predict the impact of in-service inspection (ISI) programs on the reliability of specific nuclear piping systems that have failed in service. The IGSCC is characterized by a single damage parameter, which depends on residual stresses, environmental conditions, and the degree of sensitization. The Probability of Detection (POD) curves and the benefits of in-service inspection in order to reduce the probability of the leak for nuclear piping systems subjected to IGSCC were discussed. The results show that an effective ISI requires a suitable combination of crack detection and inspection schedule. An augmented inspection schedule is recurred for piping with fast-growing crack to ensure that the inspection is done before the cracks reach critical sizes and that the use of a better inspection procedure can be more effective than a tenfold increase in the number of inspections of inferior quality.

Abstract: Given the share of buildings in energy demand, improving the energy efficiency of buildings in Morocco is an important source of energy savings. In order to finally get surplus energy balance buildings to maintain a stable indoor temperature, this work investigated the influence of orientation and local building materials with and without insulation on energy needs of a building in the city of Errachidia using the ECOTECT ANALYSIS 2011 software dedicated to the Thermal Simulation of Buildings.

Abstract: During the dry machining operation, the cutting tool is constantly subjected to extreme conditions in terms of thermal and mechanical stresses at the tool-chip interface. Indeed, the high temperature and the large plastic deformation affect and particularly accelerate the degradation of the state of the coating of the cutting tool. Thus, it becomes essential to predict the initiation and propagation of a crack in a coated tool. This makes it possible to optimize the cutting and loading conditions in order to improve the efficiency of the coating used and consequently the service life of the cutting tools.In this work, a finite element calculation code "ABAQUS / STANDARD" was used to study and analyze the cracking of a diamond-coated cutting tool. In this sense, we proposed to combine two methods often used to study the discontinuity at the tool-chip and coating-substrate interface. These are respectively the extended finite element method (XFEM) method and the cohesive element method. In addition, a parametric study on the impact of beak radius on cracking was performed to optimize this parameter.

Abstract: Plastics is very important in our lives; they used in all sectors from the high-performance industry to the mass-market industry. In this article, we will interest on the thermoplastic Acrylonitrile Butadiene Styrene (ABS) polymer; this choice is justified by the compatibility of ABS with a wide range of materials. The aim of this work is to evaluate the damage and the reliability of ABS for predict its residual lifetime.To do this, we used notched specimens of ABS prepared according to the ASTM standard, these last one are subject to tensile test at different ray of notch, The experimental results obtained have allowed us to follow the evolution the ultimate stress and then to calculate the damage. Thereafter, it was possible to identify three stages of damage that can predict at first initiation of the damage and the critical damage. Therefore, be able to intervene in time for predictive maintenance. This study also includes a correlation between two methods of calculating the damage namely static damage and damage by unified theory and this by analogy to cyclical behavior. The comparison showed good agreement.

Abstract: The main objective of this work is to study the grain shape effect (aspect ratio α = a / b) and the viscoplastic parameter γ on the evolution of the kinematic and isotropic hardening of FCC type metallic materials, under uniaxial cyclic Tension-Compression ‘‘TC’ and to interpret these results. These parameters of shape and viscoplastic were developed and introduced by Abdul-Latif and Radi, indeed in this study we use their model. Expressed within the framework of a self-consistent approach, the rate-dependent inelastic strain is examined at the crystallographic slip system level describing a constitutive model for FCC metallic polycrystals, whereas the elastic strain is determined at the granular level. Based on the Eshelby’s tensor, the elastic behavior is assumed to be compressible. For a polycrystalline structure, the grains deform plastically by crystallographic slip located at the most favorably oriented systems supporting a high resolved shear stress . The approach considers that the inclusion (grain) form is ellipsoidal of half axes defining by a, b and c such as a ≠b= c. Several numerical tests are carried out highlighting the role of shape and viscoplastic parameter on the evolution of kinematic and isotropic hardening. A general comparison between the and effect on the overall hardening of the polycrystal shows that this work hardening is more sensitive to the parameter (for given ) compared to (for given). Keywords: Grain shape effect, Ellipsoidal inclusion, Viscoplastic parameter effect, Kinematic and isotropic hardening, Uniaxial cyclic ‘‘TC‘‘, Self-consistent model.

Abstract: In this paper, the work is based on the application of probabilistic fracture mechanics models (PFM) to predict the reliability of nuclear reactors pipes under pressure. Cracking simulation of a stainless steel piping under the conditions of intergranular stress corrosion cracking (IG-SCC) is based on the general methodology recommended in the modified software M-PRAISE. IG-SCC is characterized by a unique damage parameter depending on residual stresses, environmental conditions, and sensitization degree. This parameter can be used to evaluate the structural reliability and identify the majority of efficient approaches to improve the piping reliability: effect of a corrosive medium on the reliability, which is analyzed in this present work.

Abstract: The main objective of this work is to apply the Principal Component Analysis (PCA) to the key parameters of a micromechanical model, namely the shape parameter of inclusion (grain) (ratio =a/b) and γ viscoplastic parameter in view of a better simulation. In this work, the sensitivity of the model to parameters and γ is evaluated on the stabilized global stress during cyclic Tension-Compression (TC) loadings and out-of-phase Tension–Torsion, with a sinusoidal waveform and a phase lag of 90 between the two sinusoidal signals TT90 loadings. Indeed several values ​​of and γ are pulled thanks to these loading, we use later the PCA in order to choose the couple (, γ) adequate to launch our simulation. The model used is expressed as part of the self-consistent approach and time-dependent plasticity. Based on the Eshelby tensor, this model considers that the elastic behavior is compressible. For a polycrystalline structure, the grains are deformed by crystallographic sliding located in the most favorably oriented systems and which support a strong constrained stress.

Abstract: The wire rope 19 × 7 is a complex component, it consists of 18 strands in helical from around a central core strand, each strand consist of a 7 wires laid in helical. The friction in wire rope between wire and wire decrease its lifetime. For that, this study is an attempt to present a simplified approach to predict the lifetime of cable in three scale (wire, strand, cable) using unified theory and the Basquin's law, at the level of the strand scale we have estimated its fatigue behavior in the initiation phase and also within the number of the cycle to failure as well as the ratio of the number of cycles to crack initiation N_i to the number of cycles to failure, we based on the tensile test.