Download or read book Deformation and Shear Band Development in an Ultrahigh Carbon Steel During High Strain Rate Deformation written by C. K. Syn and published by . This book was released on 2004 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mechanical response of a pearlitic UHCS-1.3C steel deformed at approximately 4000 s{sup -1} to large strains ({var_epsilon} = -0.9) has been studied. Failure, at both the macroscopic and the microscopic levels has been evaluated, and the ability of the material to absorb energy in compression has been examined. Failure occurred by the development of a shear band. However before failure, extensive buckling of the carbide plates was observed and the UHCS-1.3C material exhibited significant potential for compressive ductility and energy absorption due to the distributed buckling of these plates. Strain localization during adiabatic shear band development resulted in the formation of austenite. Subsequent cooling produced a divorced-eutectoid transformation with associated deformation, which resulted in a microstructure consisting of 50 to 100 nm sized grains. The stress-strain behavior within the shear band has also been determined. The results are used to critically evaluate the maximum shear stress criterion of shear band development. New criteria for the development of shear bands are developed based on a strain energy concept.

Download or read book Severe Plastic Deformation Through Adiabatic Shear Banding in Fe C Steels written by and published by . This book was released on 2004 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Severe plastic deformation is observed within adiabatic shear bands in iron-carbon steels. These shear bands form under high strain rate conditions, in excess of 1000 s−1, and strains in the order 5 or greater are commonly observed. Studies on shear band formation in a ultrahigh carbon steel (1.3%C) are described in the pearlitic condition. A hardness of 11.5 GPa (4600 MPa) is obtained within the band. A mechanism is described to explain the high strength based on phase transformation to austenite from adiabatic heating resulting from severe deformation. Rapid re-transformation leads to an ultra-fine ferrite grain size containing carbon principally in the form of nanosize carbides. It is proposed that the same mechanism explains the ultrahigh strength of iron-carbon steels observed in ball-milling, ball drop tests and in severely deformed wires.

Download or read book High Strain Rate High Strain Response of an Ultrahigh Carbon Steel Containing 1 3 C and 3 SI written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The mechanical response of a UHCS-1.3C material deformed at approximately 3000 s−1 to large strains (60%) has been studied. The influence of three different heat treatments, which resulted in pearlitic, martensitic and tempered martensitic microstructures, on the stress-strain response has also been examined. Failure, at both the macroscopic and the microscopic levels, and the ability of the material to absorb energy in compression have been evaluated. Failure for all heat treatments occurred due to shear localization. However, in the pearlitic condition, extensive buckling of the carbide plates was observed and the UHCS-1.3C material exhibited significant potential for compressive ductility (>60%) and energy absorption due to the distributed buckling of these plates. In the pearlitic condition, localization occurred due to adiabatic shear bands, in which austenite formed. Subsequent cooling produced a divorced-eutectoid transformation with associated deformation, which resulted in a microstructure consisting of 50 to 100 nm sized grains. The results show the large potential for use of UHCS in applications involving dynamic loading.

Download or read book Microstructure in Adiabatic Shear Bands in a Pearlitic Ultrahigh Carbon Steel written by and published by . This book was released on 2003 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Adiabatic shear bands, obtained in compression deformation at a strain rate of 4000 s−1, in a pearlitic 1.3%C steel, were investigated. Shear-bands initiated at 55% compression deformation with the width of the band equal to 14 [mu]m. Nano-indentor hardness of the shear band was 11.5 GPa in contrast to the initial matrix hardness of 3.5 GPa. The high strength of the shear band is attributed to its creation from two sequential events. First, large strain deformation, at a high strain rate, accompanied by adiabatic heating, led to phase transformation to austenite. Second, retransformation upon rapid cooling occurred by a divorced eutectoid transformation. The result is a predicted microstructure consisting of nano-size carbide particles within a matrix of fine ferrite grains. It is proposed that the divorced eutectoid transformation occurs in iron-carbon steels during high rate deformation in ball milling, ball drop tests and in commercial wire drawing.

Download or read book Modelling Hot Deformation of Steels written by John G. Lenard and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computer Aided Engineering may be defined as an approach to solving tech nological problems in which most or all of the steps involved are automated through the use of computers, data bases and mathematical models. The success of this ap proach, considering hot forming, is tied very directly to an understanding of material behaviour when subjected to deformation at high temperatures. There is general agreement among engineers that not enough is known about that topic -and this gave the initial impetus for the project described in the present study. The authors secured a research grant from NATO (Special Research Grant #390/83) with a mandate to study the "State-of-the-Art of Controlled Rolling". What follows is the result of that study. There are five chapters in this Monograph. The first one, entitled "State-of-the Art of Controlled Rolling" discusses industrial and laboratory practices and research designed to aid in the development of microalloyed steels of superior quality. Follow ing this is the chapter "Methods of Determining Stress-Strain Curves at Elevated Temperatures". The central concern here is the material's resistance to deformation or in other words, its flow strength, the knowledge of which is absolutely essential for the efficient and economical utilization of the computers controlling the rolling process.

Download or read book Measurement of the Temperature Profile During Shear Band Formation in Steels Deforming at High Strain Rates written by and published by . This book was released on 1986 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: A torsional Kolsky bar (split-Hopkinson bar) was used to deform tubular specimens of AISI 1018 cold rolled steel and AISI 1020 hot rolled steel at a nominal strain of 10 to the 3th power per s. Shear bands were observed to form in both steels and the temperature of the material in the bands was measured by determining the infrared radiation emitted at the metal surface. For this purpose, a linear array of ten indium-antimonide detectors was used to determine temperature history at ten neighboring points lying across the projected path of the shear band. Results showed that shear bands in these low carbon steels are relatively wide, that the maximum temperature rise in the band is about 450 C and that the temperature distribution across the band is consistent with results based on an analysis performed by Shawki and Clifton. The two steels have very different work hardening rates and the strain at which localization is first observed is very different for the two steels: in the cold-rolled steel it occurs at about 15% strain, while in the hot-rolled the strain is nearer 100%. This result also is consistent with predictions based on the analysis.

Download or read book AIST process metallurgy product quality and applications proceedings written by Association for Iron & Steel Technology and published by . This book was released on 2004 with total page 874 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stress Strain Rate Relations in Ultra High Carbon Steels Deformed in the Ferrite Range of Temperature written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The stress-strain rate relations in ultrahigh carbon steels (UHCSs) have been analyzed at high temperatures in the ferrite range where dislocation slip is the principal deformation mechanism. Specifically, the present investigation centers on the factors influencing the strength of UHCS in the ferrite range of 500 to 700 C and in the strain rate range of 10−3 to 103 s−1. These steels contain iron carbide as a second phase either in the form of spheroidite or pearlite and vary in the grain size according to the processing history. The new variables that need to be taken into account are the effect of ferromagnetism and its change with temperature on the creep strength of the ferritic UHCSs. Recent studies have shown that ferromagnetism strongly influences the lattice and dislocation pipe diffusion coefficient and the elastic modulus of iron in the ferrite range of temperature. These variables are shown to influence the creep strength of ferrite-base steels and explain the high activation energies that are observed in many of the ferritic UHCSs.

Download or read book High Strain Rate Induced Failure in Steels at High Shear Strains written by Nebojša Panić and published by . This book was released on 1999 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Material Behavior Under High Stress and Ultrahigh Loading Rates written by John Mescall and published by Springer Science & Business Media. This book was released on 2013-03-07 with total page 327 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Army Materials and Mechanics Research Center in coopera tion with the Materials Science Group of the Department of Chemical Engineering and Materials Science of Syracuse University has been conducting the Annual Sagamore Army Materials Research Conference since 1954. The specific purpose of these conferences has been to bring together scientists and engineers from academic institutions, industry, and government who are uniquely qualified to explore in depth a subject of importance to the Department of Defense, the Army, and the scientific community. The proceedings of this conference, entitled MATERIAL BEHAVIOR UNDER HIGH STRESS AND ULTRAHIGH LOADING RATES, will be published in two parts. The topics covered in the present volume include dynamic plasticity, adiabatic shear/localized deformation, and dynamic fracture mechanics. Papers dealing with ordnance applica tions, projectile launch environment, and recent work-in-progress will appear as an AMMRC Technical Report and will have more limited distribution in accordance with recent Army guidelines. The Conference Chairmen are particularly grateful to the members of the Program Committee. We wish also to acknowledge the assistance of Mr. Charles Polley of the Army Materials and Mechanics Research Center, Mr. Robert Sell, Ms. Helen Brown DeMascio, and Ms. Mary Ann Holmquist of Syracuse University throughout the con ference planning stages and the publication of the text. The continued active interest in and support of these confer ences by Dr. E. Wright and Col. George Sibert, Direct and Deputy Director/Commander, respectively, of the Army Materials and Mechan ics Research Center, is appreciated.

Download or read book High Strain Rate induced Failure in Steels at High Shear Strains written by and published by . This book was released on 1908 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Materials deformed at high strain rates exhibit sometimes the behaviour that is very different from that at static or quasi-static loading. Material and physical properties that are of no concern in low strain rates become crucial in the material response at high strain rates. Material properties such as thermal diffusivity and thermal softening have to be considered in order to understand the mechanism of deformation at high strain rates. The most important aspect of high strain rate deformation is the occurrence of local thermal and mechanical instability that leads to failure of the material, usually characterised by the occurrence of adiabatic shear bands (ASB). In this study, AISI 4140 steel was tested using a torsional split Hopkinson bar at three different strain rates and the impact of strain rate on the material behaviour was examined. The influence of material hardness on failure mechanisms was also investigated by producing different tempers of 4140 steel with distinct microstructures and different hardness. The fracture surface of specimens was examined under the scanning electron microscope (SEM). (Abstract shortened by UMI.).

Download or read book On the Measurement of Local Strain and Temperature During the Formation of Adiabatic Shear Bands in Steels written by Y. C. Chi and published by . This book was released on 1969 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study was conducted to determine local strain, local strain rate, and temperature distribution within an adiabatic shear band during its formation. Thin-walled tubular specimens were deformed at dynamic rates in a torsional Kolsky bar (torsional split-Hopkinson bar) and direct observation of the strain localization process was made through ultra high-speed photography of a grid pattern deposited on the specimen's surface. Temperature measurements were effected using an array of sixteen infrared radiation detectors. The optical system employed allows each detector to focus on a band 17 micrometers wide. Three different steels were tested: (1) an AISI 1018 cold rolled steel, (2) a low alloy structural steel (HY-100), and (3) an AISI 4340 VAR steel tempered to either of two hardnesses, HRC 44 or 55. The principal goal of the investigation was to relate initial geometric defects in specimen geometry to the timing of stress collapse during shear band development. A comparison of experimental results with predictions based on the analysis of Molinari and Clifton showed good agreement. In addition, quasi-static tests on the same materials revealed two significant differences between dynamic and quasi-static plastic deformation. First, localization of strain into a shear band occurs in dynamic deformation, but never quasi-statically, and second, the magnitude of the strain fracture is always considerably greater in quasi-static deformation than dynamically. (kt).

Download or read book Adiabatic Shear Localization written by Bradley Dodd and published by Elsevier. This book was released on 2012-05-22 with total page 469 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Download or read book Deformation of Annealed Low Carbon Steel at High Strain Rates written by Reuy-shan Lee and published by . This book was released on 1971 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Prediction of the Formation of Adiabatic Shear Bands in High Strength Low Alloy 4340 Steel Through Analysis of Grains and Grain Deformation written by Ioannis Polyzois and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: High strain rate plastic deformation of metals results in the formation of localized zones of severe shear strain known as adiabatic shear bands (ASBs), which are a precursor to shear failure. The formation of ASBs in a high-strength low alloy steel, namely AISI 4340, was examined based on prior heat treatments (using different austenization and tempering temperatures), testing temperatures, and impact strain rates in order to map out grain size and grain deformation behaviour during the formation of ASBs. In the current experimental investigation, ASB formation was shown to be a microstructural phenomenon which depends on microstructural properties such as grain size, shape, orientation, and distribution of phases and hard particles-all controlled by the heat treatment process. Each grain is unique and its material properties are heterogeneous (based on its size, shape, and the complexity of the microstructure within the grain). Using measurements of grain size at various heat treatments as well as dynamic stress-strain data, a finite element model was developed using Matlab and explicit dynamic software LSDYNA to simulate the microstructural deformation of grains during the formation of ASBs. The model simulates the geometrical grain microstructure of steel in 2D using the Voronoi Tessellation algorithm and takes into account grain size, shape, orientation, and microstructural material property inhomogeneity between the grains and grain boundaries. The model takes advantage of the Smooth Particle Hydrodynamics (SPH) meshless method to simulate highly localized deformation as well as the Johnson-Cook Plasticity material model for defining the behavior of the steel at various heat treatments under high strain rate deformation.The Grain Model provides a superior representation of the kinematics of ASB formation on the microstructural level, based on grain size, shape and orientation. It is able to simulate the microstructural mechanism of ASB formation and grain refinement in AISI 4340 steel, more accurately and realistically than traditional macroscopic models, for a wide range of heat treatment and testing conditions.

Download or read book Effect of Heat Treatment on Stability of Adiabatic Shear Bands in 4340 Steel written by Solomon Boakye -Yiadom and published by . This book was released on 2011 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fingerprint of deformation in materials at large strains and at high strain rates is the formation of adiabatic shear bands. Adiabatic shear bands lead to unexpected failure of materials during service. This study investigated the possibility of eliminating adiabatic shear bands from materials subjected to severe deformation at high strain rates by post impact heat treatment. Five groups of cylindrical AISI 4340 steel samples were impacted using the Direct Impact Hopkinson Pressure Bar (DIHPB) developed at the University of Manitoba. Selected impacted samples with distinct transformed shear bands were soaked at 350°C to 850°C for periods ranging from 30 minutes to 4 hours to investigate how temperature and time affects the properties and structure of the shear bands. Annealing the shear bands at 350°C resulted in an increase in hardness of the shear bands and the surrounding material outside the shear bands regardless of the heat treatment before impact, amount of deformation, and the time of annealing. Significant decrease in hardness of the shear bands occurred after post impact annealing at 650°C for 30 minutes and 2 hours. Hardness of the shear bands reduced to the same level as that of the impacted material outside the shear bands. However, the initial path of the shear bands in the impacted steel samples could be traced through a "signature" left after the annealing. Post-impact annealing of the steel samples at 750°C and 850°C resulted in a homogenous microstructure with no trace of the shear bands. The "signatures" which were used to trace the path of the shear bands in impacted samples annealed at 650°C disappeared and the hardness across the samples became uniform. The observations from this study show that adiabatic shear bands in typical steel can be eliminated by annealing heat treatment. The temperature of annealing is the most critical parameter and the annealing should be performed above 650°C.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 1572 pages. Available in PDF, EPUB and Kindle. Book excerpt: