Response of Various Metals to Large Torsional Strains Over a Large Range of Strain Rates—Part 1: Ductile Metals

1983 ◽  
Vol 105 (1) ◽  
pp. 42-47 ◽  
Author(s):  
G. R. Johnson ◽  
J. M. Hoegfeldt ◽  
U. S. Lindholm ◽  
A. Nagy
Keyword(s):  
Large Range ◽  
High Strain ◽  
Strain Rates ◽  
Test Results ◽  
Ductile Metals ◽  
Positive Strain ◽  
Lower Strain ◽  
Torsional Test ◽  
Shear Strains ◽  
Nickel 200

This paper presents torsional test results for six ductile metals subjected to large shear strains and high strain rates. Included are OFHC copper, Cartridge brass, Nickel 200, Armco IF iron, Carpenter electrical iron, and 1006 steel. Torsional shear strains as high as 700 percent are achieved and strain rates vary from quasi-static to over 300 s−1. At the lower strain rates all of the materials exhibit positive strain hardening and strain rate hardening under essentially isothermal conditions. At the higher strain rates there is significant adiabatic thermal softening and strong evidence for shear instabilities and localizations. Constitutive relationships are derived from the test data and finite element computations of the tests are performed.

Response of Various Metals to Large Torsional Strains Over a Large Range of Strain Rates—Part 2: Less Ductile Metals

1983 ◽  
Vol 105 (1) ◽  
pp. 48-53 ◽  
Author(s):  
G. R. Johnson ◽  
J. M. Hoegfeldt ◽  
U. S. Lindholm ◽  
A. Nagy
Keyword(s):  
Large Range ◽  
High Strain ◽  
Tungsten Alloy ◽  
Strain Rates ◽  
Test Results ◽  
Low Alloy Steel ◽  
Ductile Metals ◽  
Torsional Test ◽  
Shear Strains ◽  
Strain Rate Hardening

This paper presents torsional test results for six metals subjected to large shear strains and high strain rates. Included are 2024-T351 aluminum, 7039 aluminum, low alloy steel, S-7 tool steel, tungsten alloy and DU-.75Ti (Depleted Uranium). The specimens are strained to fracture at strain rates from quasi-static to over 100 s−1. All of the materials exhibit strain hardening and strain rate hardening. At the higher strain rates some of the materials develop shear instabilities and localizations. Constitutive relationships are derived from the test data and finite element computations of the tests are performed.

A Micro-Damage Model for High Velocity Impact Using Combined Viscosity and Gradient Localization Limiters

2005 ◽  
Author(s):  
Rashid K. Abu Al-Rub ◽  
George Z. Voyiadjis ◽  
Anthony N. Palazotto
Keyword(s):  
High Strain ◽  
Broad Class ◽  
Damage Model ◽  
Mesh Size ◽  
Damage Mechanism ◽  
Strain Rates ◽  
Ductile Metals ◽  
Physical Description ◽  
Rate Dependent ◽  
Nonlinear Continuum

During dynamic loading processes, large inelastic deformation associated with high strain rates leads, for a broad class of ductile metals, to degradation and failure by strain localization. However, as soon as material failure dominates a deformation process, the material increasingly displays strain softening and the finite element computations are considerably affected by the mesh size and alignment. This gives rise to a non-physical description of the localized regions. This paper presents theoretical and computational frameworks to solve this problem with the aid of nonlocal gradient-enhanced theory coupled to visco-inelasticity. Constitutive equations for anisotropic thermo-viscodamage (rate-dependent damage) mechanism coupled with thermo-hypoelasto-viscoplastic deformation are developed in this work within the framework of thermodynamic laws, nonlinear continuum mechanics, and nonlocal continua. Explicit and implicit micro-structural length scale measures, which preserve the well-posedness of the differential equations, are introduced through the use of the viscosity and gradient localization limiters.

Characterization of a Ferritic Stainless Sheet Steel in Simple Shear and Uniaxial Tension at Different Strain Rates

2011 ◽  
Author(s):  
Matti Isakov ◽  
Jeremy Seidt ◽  
Kauko O¨stman ◽  
Amos Gilat ◽  
Veli-Tapani Kuokkala
Keyword(s):  
Uniaxial Tension ◽  
Simple Shear ◽  
High Strain ◽  
Image Correlation ◽  
Materials Testing ◽  
Strain Rates ◽  
Test Results ◽  
High Strain Rates ◽  
Stress Strain

In this study the mechanical properties of ferritic stainless steel EN 1.4521 (AISI 444) were characterized in uniaxial tension and simple shear. The specimen geometries were designed so that tests could be carried out both with a conventional uniaxial materials testing machine and at high strain rates with the Tensile Hopkinson Split Bar method. During the tests, specimen surface deformation was measured using a three dimensional digital image correlation technique based on a two-camera stereovision setup. This technique allowed direct measurement of the specimen gauge section deformation during the test. Test results indicate that the selected approach is suitable for large strain plastic deformation characterization of ductile metals. The stress-strain data obtained from the simple shear tests shows a correlation with the tensile test results according to the von Mises effective stress-strain criterion. Since necking is absent in shear, test data can be obtained at considerably higher plastic strains than in tension. However, the final fracture occurs under a complex loading mode due to the distortion of the specimen geometry and multiaxial loading introduced by the simple shear arrangement. Test results also show that reliable material data can be obtained at high strain rates.

scholarly journals Resistance to the piercing of composite materials

2018 ◽  
Vol 19 (6) ◽  
pp. 540-543
Author(s):  
Lesław Kyzioł
Keyword(s):  
Composite Materials ◽  
High Strain ◽  
Physical Nonlinearity ◽  
Impact Loads ◽  
Strain Rates ◽  
Test Results ◽  
The Impact ◽  
The Mathematical Model ◽  
Different Thickness ◽  
Optimal Calculation

For structures that carry dynamic loads, the requirements are imposed for safety reasons. The requirements apply to both materials and construction. This requires searching for optimal calculation methods, including geometric and physical nonlinearity, which are results from the construction of the structure. An example is various ballistic structures (ballistic shields), which are hit by bullets in which huge energy is accumulated. In this case, the hitting in the shield with a bullet can be considered as a load due to mass impact. Loads at high strain rates are described by various mathematical models. The mathematical model is complex because a large number of "coefficients" is required, moreover, the obtained test results are not always repeatable. The paper presents the results of shooting multilayer plates with composite materials with 7.62 mm caliber bullets. The shield consisted of three layers, the outer layers were steel or aluminum, the inner layer was natural or modified wood. The samples had the shape of a shield and were 50 mm in diameter and of different thickness. The results of the research allowed to assess the impact of wood modification on its puncture resistance.

Microstructure Evolution of Ti-46.5Al-2Nb-2Cr at Different Strain Rates and Temperatures

2013 ◽  
Vol 535-536 ◽  
pp. 509-513
Author(s):  
Xiang Zan ◽  
Yu Wang ◽  
Yue Hui He ◽  
Yong Liu ◽  
Wei Dong Song
Keyword(s):  
High Strain Rate ◽  
Microstructure Evolution ◽  
Elevated Temperatures ◽  
Large Range ◽  
High Strain ◽  
Deformation Mode ◽  
Strain Rates ◽  
Deformation Twins ◽  
Ordinary Dislocation ◽  
Main Deformation

The microstructure evolution of Ti-46.5Al-2Nb-2Cr with different microstructure types loaded under a large range of strain rates and elevated temperatures is investigated by TEM. The results show that deformation twins are the main deformation mode under high strain rate loadings and both ordinary dislocation and super-dislocation are the additional modes under quasi-static loadings. The proportion of twinned grains increases with the increased strain rates.

Texture Formation and Swift Effect in High Strain Torsion of NiAl

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Burghardt Klöden ◽  
Carl-Georg Oertel ◽  
Werner Skrotzki ◽  
Erik Rybacki
Keyword(s):  
Synchrotron Radiation ◽  
High Strain ◽  
Confining Pressure ◽  
Rock Deformation ◽  
Strain Rates ◽  
Texture Formation ◽  
Shear Strains ◽  
Initial Texture ◽  
Increasing Temperature ◽  
Low Shear

Texture formation and Swift effect were investigated in torsion deformed NiAl. High-strain torsion of solid bars was done with a Paterson rock deformation machine at temperatures between 700 K and 1300 K under a confining pressure of 400 MPa. The maximum shear strains and shear strain rates applied were 19×10−4 s−1 and 2.2×10−4 s−1, respectively. Textures were measured by diffraction of neutrons, electrons, and synchrotron radiation. The textures consist of an oblique cube and Goss component, the intensity of which depends on the initial texture and deformation temperature. The axial lengthening and shortening observed are related to the Goss and the oblique cube components, respectively. There is qualitative agreement between experiment and simulation at low temperature and low shear strains. With increasing temperature, continuous and discontinuous dynamic recrystallization take place, strongly influencing the development of texture and Swift effect.

Nucleation control for hot-working of silicon oxynitride based ceramics

1999 ◽  
Vol 14 (1) ◽  
pp. 170-177 ◽  
Author(s):  
Masayoshi Ohashi ◽  
Yasuo Iida ◽  
Stuart Hampshire
Keyword(s):  
High Strain ◽  
Potassium Fluoride ◽  
Hot Working ◽  
Silicon Oxynitride ◽  
Low Flow ◽  
Strain Rates ◽  
Compression Tests ◽  
High Strain Rates ◽  
Lower Strain ◽  
Long Time

An attempt was made to develop an engineering ceramic plastically deformable at high temperatures with low flow stress at high strain rates, and without strain hardening. Dense ceramic preforms were fabricated by pressureless sintering Si3N4 + SiO2 mixed powders with an addition of MgAl2O4 at 1500 °C. A transient liquid, which occurs during the reaction sintering of Si2N2O, was utilized for subsequent net-shape forming. The ceramic (6Φ × 6 mm column) was deformed without any cracks and cavities in compression tests at high strain rates (10−2−10−3:s−1) at 1500 °C, but this was not achieved in a test at lower strain rates for a long time, because of the growth of elongated Si2N2O grains during the test. Potassium fluoride (KF) was used as a dopant for retardation of nucleation of Si2N2O during sintering and hot-working. The KF-doped preforms were successfully plastically deformed even in the test for a long time.

Solid Solution Effects and Deformation Micros trueture of Shock-Loaded Iron Manganese Alloys

1970 ◽  
Vol 28 ◽  
pp. 420-421
Author(s):  
A. Christou ◽  
J. V. Foltz ◽  
N. Brown
Keyword(s):  
Solid Solution ◽  
Shock Loading ◽  
High Strain ◽  
Local Stress ◽  
Strain Rates ◽  
Local Stress Concentration ◽  
Bcc Metals ◽  
Manganese Alloys ◽  
Iron Manganese ◽  
Transmission Microscope

In general, all BCC transition metals have been observed to twin under appropriate conditions. At the present time various experimental reports of solid solution effects on BCC metals have been made. Indications are that solid solution effects are important in the formation of twins. The formation of twins in metals and alloys may be explained in terms of dislocation mechanisms. It has been suggested that twins are nucleated by the achievement of local stress-concentration of the order of 15 to 45 times the applied stress. Prietner and Leslie have found that twins in BCC metals are nucleated at intersections of (110) and (112) or (112) and (112) type of planes.In this paper, observations are reported of a transmission microscope study of the iron manganese series under conditions in which twins both were and were not formed. High strain rates produced by shock loading provided the appropriate deformation conditions. The workhardening mechanisms of one alloy (Fe - 7.37 wt% Mn) were studied in detail.

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