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Alain Molinari - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of Adiabatic Shear banding in orthogonal cutting of Ti alloy
    International Journal of Mechanical Sciences, 2013
    Co-Authors: María Henar Miguélez, Xavier Soldani, Alain Molinari
    Abstract:

    This work is focused on the numerical analysis of Adiabatic Shear banding in orthogonal cutting of Ti6Al4V alloy. Segmented chip results from Adiabatic Shear banding, depending on the competition of thermal softening and strain and strain rate hardening. The influence of cutting velocity and feed in the chip segmentation is studied. Also the role of friction at the tool-chip interface and the effect of rheological parameters of the constitutive equation are analyzed. Experimental tests obtained from previous work of the authors [Molinari A, Musquar C, Sutter G, Adiabatic Shear banding in high speed machining of Ti–6Al–4V experiments and modeling, Int J Plast, vol. 18, 2002, p. 443–459] and others were used as a reference to validate the models. Cutting forces and the mechanism of plastic flow localization are analyzed in terms of frequency of segmentation and Shear band width and compared to experimental data.

  • Analysis of the dynamic propagation of Adiabatic Shear bands
    International Journal of Solids and Structures, 2002
    Co-Authors: A.-s Bonnet-lebouvier, Alain Molinari, Paul Lipinski
    Abstract:

    The dynamic propagation of Adiabatic Shear bands is analysed. In the numerical simulations, a layer of finite length and finite thickness is subjected to Shear loading. After a transient, a steady state is attained in which Adiabatic Shear bands propagate with a constant velocity. The evolution of the Shear band speed is determined as a function of the applied velocity. A dimensional analysis allows to determine a general law describing the influence of each problem's parameter on the Shear band speed. The effects of heat conduction are discussed in details. Finally the concept of a process zone is introduced. The process zone is a region propagating with the Shear band tip, where an intense stress softening is produced by thermo-mechanical coupling. It is shown how the Shear band propagation is controlled by this stress softening.

  • COLLECTIVE BEHAVIOR AND SPACING OF Adiabatic Shear BANDS
    Journal of The Mechanics and Physics of Solids, 1997
    Co-Authors: Alain Molinari
    Abstract:

    The failure of metals subjected to high strain rates is frequently related to the collective development of Adiabatic Shear bands which results in a patterning depending on the material properties and the loading conditions. In this paper, the spacing between Adiabatic Shear bands is characterized by analytical means in a one-dimensional formulation. Using a perturbation analysis, a dominant instability mode can be characterized, whose wavelength is related to the Shear-band spacing. Explicit solutions are found for materials with no strain hardening. Asymptotic developments are used to obtain results that account for strain hardening. Comparisons are made with experimental results and other existing models.

D. Rittel - One of the best experts on this subject based on the ideXlab platform.

  • The genesis of Adiabatic Shear bands
    Scientific Reports, 2016
    Co-Authors: P. Landau, A. Venkert, S. Osovski, V. Gärtnerová, D. Rittel
    Abstract:

    Adiabatic Shear banding (ASB) is a unique dynamic failure mechanism that results in an unpredicted catastrophic failure due to a concentrated Shear deformation mode. It is universally considered as a material or structural instability and as such, ASB is hardly controllable or predictable to some extent. ASB is modeled on the premise of stability analyses. The leading paradigm is that a competition between strain (rate) hardening and thermal softening determines the onset of the failure. It was recently shown that microstructural softening transformations, such as dynamic recrystallization, are responsible for Adiabatic Shear failure. These are dictated by the stored energy of cold work, so that energy considerations can be used to macroscopically model the failure mechanism. The initial mechanisms that lead to final failure are still unknown, as well as the ASB formation mechanism(s). Most of all - is ASB an abrupt instability or rather a gradual transition as would be dictated by microstructural evolutions? This paper reports thorough microstructural characterizations that clearly show the gradual character of the phenomenon, best described as a nucleation and growth failure mechanism, and not as an abrupt instability as previously thought. These observations are coupled to a simple numerical model that illustrates them.

  • Microstructural Aspects of Adiabatic Shear Failure in Annealed Ti6Al4V
    Metallurgical and Materials Transactions A, 2009
    Co-Authors: P. Landau, A. Venkert, D. Rittel
    Abstract:

    This work reports a comprehensive examination of the microstructural evolution in Ti6Al4V subjected to high-strain-rate deformation. The sequence of microstructural rearrangements leading to Adiabatic Shear banding is presented. A detailed microstructural comparison between two types of specimens, one that failed by Adiabatic Shear and the other that was strained to half its failure strain, is carried out. The main observation is that for this material, the microstructure of the two types of specimens is qualitatively identical, indicating that from approximately half the failure strain until Adiabatic Shear failure, no additional micromechanism is observed to develop and operate. Overall, the microstructure undergoes a significant refinement with the increasing strain until the formation of dynamically recrystallized grains. It is therefore suggested that the evolution of the volume fraction of recrystallized grains should be characterized from its early onset until final failure by Adiabatic Shear banding.

  • A different viewpoint on Adiabatic Shear localization
    Journal of Physics D: Applied Physics, 2009
    Co-Authors: D. Rittel
    Abstract:

    This short review addresses the Adiabatic Shear failure mechanism (Adiabatic Shear banding—ASB) in metals subjected to high strain-rate deformations. ASB is usually considered as an instability resulting from thermal softening effects. We present a different viewpoint, based on experimental observations in which we identify the stored energy of cold work as the driving force for microstructural rearrangement by dynamic recrystallization (DRX). DRX is an athermal phenomenon that is observed at the early stages of the dynamic deformation process, while thermal effects are insignificant, long before an ASB has formed in the specimen. We tentatively identify DRX as the softening mechanisms whose growth in a localized area will lead to final failure.

  • A new perspective on Adiabatic Shear failure
    DYMAT 2009 - 9th International Conferences on the Mechanical and Physical Behaviour of Materials under Dynamic Loading, 2009
    Co-Authors: D. Rittel
    Abstract:

    Adiabatic Shear failure is commonly considered to be induced by thermal softening, for which a critical strain describes the onset of failure. This paper revisits this concept on the basis of experimental evidence showing that the homogeneous temperature rise prior to localization often remains quite modest. Instead, we consider the dynamically stored energy of cold work as a key factor in the process, whose role is to trigger dynamic recrystallization (DRX) at an early deformation stage where thermal effects are negligible. DRX, which precedes the localization instead of being its result, causes local softening of the material. The dynamically recrystallized enclaves are believed to grow and coalesce into a fully developed Adiabatic Shear band

  • dynamic recrystallization as a potential cause for Adiabatic Shear failure
    Physical Review Letters, 2008
    Co-Authors: D. Rittel, P. Landau, A. Venkert
    Abstract:

    Dynamic recrystallization (DRX) is almost universally observed in the microstructure of Adiabatic Shear bands. It is usually admitted that DRX results from the large temperatures that develop in the band along with very high local strains. This paper reports the observation of dynamically recrystallized nanograins in Ti6A14V alloy specimens that were impact loaded to only half the failure strain at which the Adiabatic Shear band develops. This observation shows that DRX not only precedes Adiabatic Shear failure but it is also likely to be a dominant micromechanical factor in the very generation of the band. This result means that Adiabatic Shear failure is not only a mechanical instability but also the outcome of strong microstructural evolutions leading to localized material softening prior to any thermal softening.

Min Jie Wang - One of the best experts on this subject based on the ideXlab platform.

  • On Adiabatic Shear fracture in high-speed machining of martensitic precipitation-hardening stainless steel
    Journal of Materials Processing Technology, 2016
    Co-Authors: Guozheng Kang, Hui Chen, Min Jie Wang
    Abstract:

    Abstract The serrated chip produced in high-speed machining of martensitic precipitation-hardening stainless steel is inevitably tore up into isolated segments due to Adiabatic Shear fracture with the further increase of cutting speed. The induced mechanism of Adiabatic Shear fracture and the corresponding damage process in high-speed machining are investigated through quick-stop tests and chip morphology examinations. The isolated segments generated due to Adiabatic Shear fracture which is found in the rate-related process of Adiabatic Shear evolution is a cyclic process of energy convergence and release with ductile-brittle damage transition. The fracture energy of Adiabatic Shear band approaches a stable saturation limit with the increases of cutting speed and feed. On the basis of saturation limit model, the critical fracture energy is predicted by cutting conditions and compared with the experimental results.

  • component analysis of Adiabatic Shear band formed in high speed cutting of high strength alloy steel
    Applied Mechanics and Materials, 2011
    Co-Authors: Chun Zheng Duan, Min Jie Wang, Zhao Xi Wang, Wei Sen Kong
    Abstract:

    The component distribution of Adiabatic Shear banding during high speed cutting(HSC) is important to understand the phase transformation during formation of Adiabatic Shear band and mechanism of serrated chip formation. This paper analyzed element distribution inside and near the Adiabatic Shear bands formed during HSC of 30CrNi3MoV high strength steel using electronic probe. It was found that there is no obvious element segregation, but carbon element tends to gather towards Adiabatic Shear band’s boundaries. The density of carbon inside the Shear bands tends to increase with the increase of cutting speed. The results indicated that the diffusion and gather of carbon may occur during formation of Adiabatic Shear band. The diffusion mechanism may be short-range diffusion driven by high-speed deformation and high temperature rise.

  • Adiabatic Shear Localization in High Speed Cutting of Hardened Steel
    Applied Mechanics and Materials, 2011
    Co-Authors: Chun Zheng Duan, Wei Sen Kong, Zhao Xi Wang, Min Jie Wang
    Abstract:

    The formation and development of Adiabatic Shear localization in serrated chips have great significance to study of mechanism of high speed cutting. This paper investigates the theory prediction and experimental verification of the critical cutting speed of Adiabatic Shear localization, distribution of Adiabatic Shear band in serrated chip and the geometry of Adiabatic Shear band during high speed cutting of hardened steel. The results indicated that the theoretical prediction of critical cutting speed is consistent with the experimental results.With the increase of cutting speed, the width and spacing of Adiabatic Shear bands in the serrated chips decrease linearly. There are two types of Adiabatic Shear bands during the formation and development of Adiabatic Shear localization, i.e. the deformation Shear band and the transformed Shear band.

Yilong Bai - One of the best experts on this subject based on the ideXlab platform.

  • Adiabatic Shear Localization, Second Edition: Frontiers and Advances
    2012
    Co-Authors: Bradley Dodd, Yilong Bai
    Abstract:

    Adiabatic Shear localization is a mode of failure that occurs in dynamic loading. It is characterized by thermal softening occurring over a very narrow region of a material and is usually a precursor to ductile fracture and catastrophic failure. This reference source is the revised and updated version of the first detailed study of the mechanics and modes of Adiabatic Shear localization in solids. Building on the success of the first edition, the book provides a systematic description of a number of aspects of Adiabatic Shear banding. The concepts and techniques described in this work can usefully be applied to solve a multitude of problems encountered by those investigating fracture and damage in materials, impact dynamics, metal working and other areas. Specific chapters focus on energetic materials, polymers, bulk metal glasses, and the mathematics of Shear banding as well as the numerical modeling of them. With its detailed coverage of the subject, this book is of great interest to academics and researchers into materials performance as well as professionals.Up to date coverage of the subject and research that has occurred over the past 20 years.Each chapter is written on a different sub-field of Adiabatic Shear by an acknowledged expert in the field.Detailed and clear discussions of each aspect.

  • Adiabatic Shear localization frontiers and advances
    2012
    Co-Authors: Yilong Bai
    Abstract:

    Adiabatic Shear localization is a mode of failure that occurs in dynamic loading. It is characterized by thermal softening occurring over a very narrow region of a material and is usually a precursor to ductile fracture and catastrophic failure. This reference source is the revised and updated version of the first detailed study of the mechanics and modes of Adiabatic Shear localization in solids. Building on the success of the first edition, the book provides a systematic description of a number of aspects of Adiabatic Shear banding. The concepts and techniques described in this work can usefully be applied to solve a multitude of problems encountered by those investigating fracture and damage in materials, impact dynamics, metal working and other areas. Specific chapters focus on energetic materials, polymers, bulk metal glasses, and the mathematics of Shear banding as well as the numerical modeling of them. With its detailed coverage of the subject, this book is of great interest to academics and researchers into materials performance as well as professionals. Up to date coverage of the subject and research that has occurred over the past 20 years. Each chapter is written on a different sub-field of Adiabatic Shear by an acknowledged expert in the field. Detailed and clear discussions of each aspect.

  • Adiabatic Shear banding instability in bulk metallic glasses
    Applied Physics Letters, 2005
    Co-Authors: Lanhong Dai, L.f. Liu, M. Yan, Yilong Bai
    Abstract:

    In this letter, a linear instability analysis was performed to highlight the mechanism of formation of Adiabatic Shear banding instabilities in bulk metallic glasses (BMGs). It is found that this instability is determined by the free volume coalescence-diffusion Deborah number. The most important findings are that both free volume coalescence softening and Adiabatic heating softening exert an influence on the formation of Adiabatic Shear banding instability in BMGs, and higher strain rate promotes the growth of instability. These results are of particular significance in understanding the mechanism of formation of Shear bands in BMGs.

  • Formation of Adiabatic Shear band in metal matrix composites
    International Journal of Solids and Structures, 2004
    Co-Authors: Lanhong Dai, L.f. Liu, Yilong Bai
    Abstract:

    A modified single-pulse loading split Hopkinson torsion bar (SSHTB) is introduced to investigate Adiabatic Shear banding behavior in SiCp particle reinforced 2024 Al composites in this work. The experimental results showed that formation of Adiabatic Shear band in the composite with smaller particles is more readily observed than that in the composite with larger particles. To characterize this size-dependent deformation localization behavior of particle reinforced metal matrix composites (MMCp), a strain gradient dependent Shear instability analysis was performed. The result demonstrated that high strain gradient provides a deriving force for the formation of Adiabatic Shear banding in MMCp.

Li Shu-kui - One of the best experts on this subject based on the ideXlab platform.

  • Numerical Simulation of Adiabatic Shear and Temperature Field in Hat-shaped Specimens
    Journal of Materials Engineering, 2007
    Co-Authors: Li Shu-kui
    Abstract:

    Appropriate model and space discretization were chosen to simulate the loading process of specimens conducted on the Split Hopkinson Pressure Bar(SHPB) in two-dimension,and the Adiabatic Shear deformation course of the hat-shaped specimen under high strain rate was obtained.Based on the criterion of the formation of Adiabatic Shear to Stress Collage,the rule of Adiabatic Shear deformation was analyzed,the simulated stress-time curves and strain-time curves were employed to calculate the temperature field,the type of the Shear bands was determined,and the results of numerical simulation are consistent with the experimental results.

  • Study on Adiabatic Shear failure of W-Ni-Mn heavy alloy
    Explosion and Shock Waves, 2007
    Co-Authors: Li Shu-kui
    Abstract:

    Dynamic compression tests of W-Ni-Mn alloy were performed,using cylindrical specimens 5 mm both in diameter and long with the split Hopkinson pressure bar(SHPB) technique.Both sections and fracture surfaces of specimens were observed with SEM.Connected with true stress-strain curves of specimens,it was found that Adiabatic Shear bands in sections of specimens appeared distinctly when specimens took place about 45% true strain.W-Ni-Mn alloy is easier to come into being Adiabatic Shear band(ASB) than the conventional tungsten heavy alloy,and has higher Adiabatic Shear sensitivity.

  • Progresses and trends in researches on Adiabatic Shear deformation
    Ordnance Material Science and Engineering, 2003
    Co-Authors: Li Shu-kui
    Abstract:

    The latest progress in the researches on Adiabatic Shear deformation was reviewed detailedly. The reviews were divided into three research fields: the first one is on Adiabatic Shear constitutive instability; the second one is about microstructure and the micro-structual evolution in the Adiabatic Shear band as well as the evolutionary mechanics; the third one is on the numerical simulation to Adiabatic Shear deformation. Some problems in these researches were discussed and the research directions on Adiabatic Shear deformation were also pointed out.