The purpose of this study is to introduce a new approach of high speed cutting numerical modelling. A Lagrangian smoothed particle hydrodynamics (SPH)-based model is carried out using the Ls-Dyna software. SPH is a meshless method, thus large material distortions that occur in the cutting problem are easily managed and SPH contact control permits a ''natural'' workpiece/chip separation. The developed approach is compared to machining dedicated code results and experimental data. The SPH cutting model has proved is ability to account for continuous to shear localized chip formation and also correctly estimates the cutting forces, as illustrated in some orthogonal cutting examples. Thus, comparable results to machining dedicated codes are obtained without introducing any adjusting numerical parameters (friction coefficient, fracture control parameter).

Transforming growth factor–β (TGF-β) functions to suppress tumorigenesis in normal mammary tissues and early-stage breast cancers and, paradoxically, acts to promote the metastasis and chemoresistance in late-stage breast cancers, particularly triple-negative breast cancers (TNBCs). Precisely how TGF-β acquires oncogenic characteristics in late-stage breast cancers remains unknown, as does the role of the endogenous mammalian target of rapamycin (mTOR) inhibitor, Dep domain–containing mTOR-interacting protein (Deptor), in coupling TGF-β to TNBC development and metastatic progression. Here we demonstrate that Deptor expression was downregulated in basal-like/TNBCs relative to their luminal counterparts. Additionally, Deptor expression was 1) inversely correlated with the metastatic ability of human (MCF10A) and mouse (4T1) TNBC progression series and 2) robustly repressed by several inducers of epithelial-mesenchymal transition programs. Functional disruption of Deptor expression in 4T07 cells significantly inhibited their proliferation and organoid growth in vitro, as well as prevented their colonization and tumor formation in the lungs of mice. In stark contrast, elevated Deptor expression was significantly associated with poorer overall survival of patients harboring estrogen receptor α–negative breast cancers. Accordingly, enforced Deptor expression in MDA-MB-231 cells dramatically enhanced their 1) organoid growth in vitro, 2) pulmonary outgrowth in mice, and 3) resistance to chemotherapies, an event dependent on the coupling of Deptor to survivin expression. Collectively, our findings highlight the dichotomous functions of Deptor in modulating the proliferation and survival of TNBCs during metastasis; they also implicate Deptor and its stimulation of survivin as essential components of TNBC resistance to chemotherapies and apoptotic stimuli.

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. The aim of this study is to improve the general understanding of tungsten carbide (WC-Co) tool wear under dry machining of the hard-to-cut titanium alloy Ti6Al4V. The chosen approach includes experimental and numerical tests. The experimental part is designed to identify wear mechanisms using cutting force measurements, scanning electron microscope observations and optical profilometer analysis. Machining tests were conducted in the orthogonal cutting framework and showed a strong evolution of the cutting forces and the chip profiles with tool wear. Then, a numerical method has been used in order to model the machining process with both new and worn tools. The use of smoothed particle hydrodynamics model (SPH model) as a numerical tool for a better understanding of the chip formation with worn tools is a key aspect of this work. The predicted chip morphology and the cutting force evolution with respect to the tool wear are qualitatively compared with experimental trends. The chip formation mechanisms during dry cutting process are shown to be quite dependent from the worn tool geometry. These mechanisms explain the high variation of the experimental and numerical feed force between new and worn tools.

The meteoroids and debris environment play an important role in the reduction of spacecraft life time. Ejecta or secondary debris, are produced when a debris or a meteoroid impact a spacecraft surface. These ejecta can contribute to a modification of the debris environment: either locally by the occurrence of secondary impacts on the component of complex and large space structures, or at long distance by formation of small orbital debris. This double characteristic underlines the necessity to model the damages caused by an HVI as well as the material ejection caused by the impact. Brittle materials are particularly sensitive to hypervelocity impacts because they produce features larger than those observed on ductile targets and the ejected fragments total mass including ejectas and spalls is in the order of 100 times bigger than the impacting mass. The French atomic energy commission (CEA) faces to the same problem in the Laser MégaJoule project (LMJ). The various instruments used in the experiment chamber will undergo many aggressions resulting from target disassembly. Thus the lasers optics will be bombarded as hypervelocity debris and shrapnel. In this study, the authors only focus on potential impacts of debris and shrapnel on fused silica optical debris shields. These Main Debris Shields called MDS are 20mm thick fused silica plates placed in front of each lasers way out. 2 mm thick Disposable Debris Shields, DDS, located in front of the MDS might be used to stop vapour, particulate, droplets and substantially reduce very small shrapnel cratering on the main debris shields. But ejecta from the rear surface of the DDS and penetration through the DDS are likely to damage the MDS and seed new laser damage sites. The MDS lifetime is limited by the laser damage growth of those damage sites.The main aim of this paper is to study the damaging and ejection processes that occur during hypervelocity impacts on thin brittle targets (d p = 500 microns for velocities ranging from 1 to 5 km/s). The two stage light gas gun "MICA" available at CEA-CESTA has been used to impact thin fused silica debris shields and the impacted samples have been analysed with environmental SEM microscopy and perthometer. Experimental characterization of ejected matter has also been performed on the MICA facility: lightweight paperboards coated with adhesive and silica aerogel have been used to collect and characterize the ejected fragments including ejectas and spalls. The severe deformations occurring in any hypervelocity impact event are best described by meshless methods since they offer clear advantages for modeling large deformations and failure of solids as compared to mesh-based methods. Numerical simulation using the SPH method of Ls-Dyna and the Johnson Holmquist material model adapted for fused silica were performed at ENSICA. The results of these calculations are compared to experimental data obtained with MICA. Experimental data include the damage features in the targets (front and back spalled zone, perforation hole and ...

The composite materials are nowadays widely used in aeronautical domain. These materials are subjected to different types of loading that can damage a part of the structure. This diminishes the resistance of the structure to failure. In this paper, matrix cracking and delamination propagation in composite laminates are simulated as a part of damage. Two different computational strategies are developed: (i) a cohesive model (CM) based on the classical continuum mechanics and (ii) a continuous damage material model (CDM) coupling failure modes and damage. Another mixed methodology (MM) is proposed using the contin uous damage model for delamination initiation and the cohesive model for 3D crack propa gation and mesh openings. A good agreement was obtained when compared simple charac terization tests and corresponding simulations.

The French Ministry of Defence's procurement agency, the Direction Générale de l'Armement (DGA), is in charge of assessing and testing armament systems in order to equip the armed forces and prepare for the future. DGA Aeronautical Systems, the technical centre dedicated to evaluate and test aircraft, combines test and evaluation to clear, among others, parachute systems. The parachute evaluation is historically based on experimental data and so requires numerous flight tests which can prove expensive and time consuming. In order to have a greater understanding of the parachute dynamic behavior and to optimize the parachute systems flight tests, DGA Aeronautical Systems developed a modeling and simulation capability as a support to evaluation. For this purpose, DGA Aeronautical Systems, with the help of ISAE, developed Fluid Structure Interaction (FSI) simulations of parachutes using the LS-Dyna commercial Finite Element Analysis (FEA) tool. This tool is largely used for solving highly nonlinear transient problems and enables doing coupled multi-physics simulations such as FSI simulations. DGA Aeronautical Systems has been using the software since 2003. In the recent years, the parachute simulation has been much improved thanks to the implementation of a porosity algorithm in LS-Dyna at the common request of DGA and parachute industry. The paper presents recent improvements in Arbitrary Lagrangian Eulerian (ALE) techniques used to analyze the canopy inflation and the quasi-steady state descent phases characteristics. Up to now, only infinite mass type simulations were developed by constraining the parachute confluence point and applying a prescribed airflow to the fluid. The applied airflow velocity came from real in-flight measurements of paratrooper or load trajectory determinations. This simulation type is representative to wind tunnel tests. From now on, thanks to considerable computational resources, finite mass type simulations are also possible. It consists in applying the force of gravity to the parachute system. This allows simulating both the inflation phase (from vertical packed parachute geometry) and the quasi-steady state descent. Among others, the static line parachute of the new French Army troop parachute system called EPC (Ensemble de Parachutage du Combattant) was modeled at real scale. Modeling techniques are presented and results of the EPC static line parachute simulation are compared with real inflight measurements. The benefits of FSI simulations prior to parachute testing are presented. In a near future, incompressible and compressible Navier-Stokes solvers will be available in the next version of LS-Dyna. These code enhancements will be tested to simulate the parachute flight and hopefully will bring the ability to analyze more accurately the aerodynamics of the canopy and the structural behavior of the fabrics. These future capabilities are also discussed.

No abstract

Energy absorption during crushing is evaluated using a thermodynamic based continuum damage model inspired from the Matzenmiller-Lubliner-Taylors model. It was found that for crash-worthiness applications, it is necessary to couple the progressive ruin of the material to a representation of the matter openings and debris generation. Element kill technique (erosion) and/or cohesive elements are efficient but not predictive. A technique switching finite elements into discrete particles at rupture is used to create debris and accumulated mater during the crushing of the structure. Switching criteria are evaluated using the contribution of the different ruin modes in the damage evolution, energy absorption, and reaction force generation.