scholarly journals Моделирование временных эффектов необратимого деформирования на основе релаксационной модели пластичности

2019 ◽  
Vol 61 (6) ◽  
pp. 1015
Author(s):  
Н.С. Селютина ◽  
Ю.В. Петров
Keyword(s):  
Plastic Deformation ◽  
Yield Strength ◽  
High Strength ◽  
High Rate ◽  
Smooth Transition ◽  
Strain History ◽  
Strain Rates ◽  
Relaxation Model ◽  
Yield Drop ◽  
Wide Range

The analysis of plastic deformation of metals and polymethylmethacrylate under dynamic loading is carried out using a relaxation model of plastic deformation. The invariance of the parameters of the relaxation model of plasticity to the strain history allows us to obtain any set of deformation curves from a united viewpoint, both monotonic, with varying yield strength, and non-monotonic, with emerging and varying yield drop, as it is observed in experiments. The increase of the yield strength of high-strength 2.3Ni-1.3Cr steel together with the hardening effect both under high-rate and slow deformation is also modeled on the basis of the relaxation model. Using DP600 steel and nanocrystalline nickel as an example it is shown that the relaxation model of plasticity allows one to predict a smooth transition to the plastic deformation stage at slow quasi-static effects of ~ 10–3 s – 1, and also the appearance of a yield drop effect at strain rates of 500–6000 s –1. It is also shown that the developed approach allows one to simulate similar effects under high-rate deformation of polymethylmethacrylate. Thus, it was demonstrated using specific materials as an example that it is possible to effectively predict the deformation dependencies of the materials studied in a wide range of strain rates of 10-4-104 s-1 based on the parameters of the relaxation model of irreversible deformations.

scholarly journals Comparative Analysis of Dynamic Plasticity Models

2018 ◽  
Vol 57 (2) ◽  
pp. 199-211 ◽  
Author(s):  
N.S. Selyutina ◽  
Yu.V. Petrov
Keyword(s):  
Plastic Deformation ◽  
Comparative Analysis ◽  
Wide Spectrum ◽  
High Rate ◽  
Relaxation Model ◽  
Time Model ◽  
Slow Dynamic ◽  
Stress Strain Relation ◽  
Wide Range ◽  
Deformation Models

Abstract In the paper, a new phenomenological interpretation of some of the principal temporal effects of high-rate plastic deformation of metals from a united viewpoint is represented. A comparative analysis of some of the well-known dynamic plastic deformation models is given. Influence of strain rate on the stress-strain relation in a wide range of strain rates for different types of aluminum alloys and steels is described by the relaxation model of plasticity, by original and improved empirical Johnson-Cook models, and by the phenomenological Rusinek-Klepaczko model. It is shown that the structural-time model (“the relaxation model of plasticity”) is capable to effectively predict a wide spectrum of materials responses to fast and slow dynamic loading.

Strain-Rate Effect on the Tensile Behaviour of High Strength Alloys

2011 ◽  
Vol 82 ◽  
pp. 124-129 ◽  
Author(s):  
Ezio Cadoni ◽  
Matteo Dotta ◽  
Daniele Forni ◽  
Stefano Bianchi
Keyword(s):  
Strain Rate ◽  
Rate Sensitivity ◽  
High Strength ◽  
Constitutive Law ◽  
Tensile Behaviour ◽  
Strain Rates ◽  
Cross Sectional ◽  
Split Hopkinson Tensile Bar ◽  
Wide Range ◽  
First Results

In this paper the first results of the mechanical characterization in tension of two high strength alloys in a wide range of strain rates are presented. Different experimental techniques were used for different strain rates: a universal machine, a Hydro-Pneumatic Machine and a JRC-Split Hopkinson Tensile Bar. The experimental research was developed in the DynaMat laboratory of the University of Applied Sciences of Southern Switzerland. An increase of the stress at a given strain increasing the strain-rate from 10-3 to 103 s-1, a moderate strain-rate sensitivity of the uniform and fracture strain, a poor reduction of the cross-sectional area at fracture with increasing the strain-rate were shown. Based on these experimental results the parameters required by the Johnson-Cook constitutive law were determined.

Paradox of Strength and Ductility in Metals Processed Bysevere Plastic Deformation

2002 ◽  
Vol 17 (1) ◽  
pp. 5-8 ◽  
Author(s):  
R. Z. Valiev ◽  
I. V. Alexandrov ◽  
Y. T. Zhu ◽  
T. C. Lowe
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Grain Size ◽  
Yield Strength ◽  
Mechanical Behavior ◽  
High Strength ◽  
High Ductility ◽  
Elongation To Failure ◽  
Failure Ductility ◽  
Strength And Ductility

It is well known that plastic deformation induced by conventional forming methodssuch as rolling, drawing or extrusion can significantly increase the strength of metalsHowever, this increase is usually accompanied by a loss of ductility. For example, Fig.1 shows that with increasing plastic deformation, the yield strength of Cu and Almonotonically increases while their elongation to failure (ductility) decreases. Thesame trend is also true for other metals and alloys. Here we report an extraordinarycombination of high strength and high ductility produced in metals subject to severeplastic deformation (SPD). We believe that this unusual mechanical behavior is causedby the unique nanostructures generated by SPD processing. The combination ofultrafine grain size and high-density dislocations appears to enable deformation by newmechanisms. This work demonstrates the possibility of tailoring the microstructures ofmetals and alloys by SPD to obtain both high strength and high ductility. Materialswith such desirable mechanical properties are very attractive for advanced structuralapplications.

Comparative Study of the Dynamic Behavior of AA2519 Aluminum Alloy in T6 and T8 Temper Conditions

2019 ◽  
Author(s):  
Adewale Olasumboye ◽  
Gbadebo Owolabi ◽  
Olufemi Koya ◽  
Horace Whitworth ◽  
Nadir Yilmaz
Keyword(s):  
Plastic Deformation ◽  
Aluminum Alloy ◽  
Stress Response ◽  
Flow Stress ◽  
Yield Strength ◽  
Strain Rate ◽  
High Strain ◽  
Second Phase ◽  
Strain Rates ◽  
High Strain Rates

Abstract This study investigates the dynamic response of AA2519 aluminum alloy in T6 temper condition during plastic deformation at high strain rates. The aim was to determine how the T6 temper condition affects the flow stress response, strength properties and microstructural morphologies of the alloy when impacted under compression at high strain rates. The specimens (with aspect ratio, L/D = 0.8) of the as-cast alloy used were received in the T8 temper condition and further heat-treated to the T6 temper condition based on the standard ASTM temper designation procedures. Split-Hopkinson pressure bar experiment was used to generate true stress-strain data for the alloy in the range of 1000–3500 /s strain rates while high-speed cameras were used to monitor the test compliance with strain-rate constancy measures. The microstructures of the as received and deformed specimens were assessed and compared for possible disparities in their initial microstructures and post-deformation changes, respectively, using optical microscopy. Results showed no clear evidence of strain-rate dependency in the dynamic yield strength behavior of T6-temper designated alloy while exhibiting a negative trend in its flow stress response. On the contrary, AA2519-T8 showed marginal but positive response in both yield strength and flow behavior for the range of strain rates tested. Post-deformation photomicrographs show clear disparities in the alloys’ initial microstructures in terms of the second-phase particle size differences, population density and, distribution; and in the morphological changes which occurred in the microstructures of the different materials during large plastic deformation. AA2519-T6 showed a higher susceptibility to adiabatic shear localization than AA2519-T8, with deformed and bifurcating transformed band occurring at 3000 /s followed by failure at 3500 /s.

Studies on the Dynamic Compressive Properties of Open-Celled Aluminum Alloy Foams

2006 ◽  
Vol 306-308 ◽  
pp. 905-910 ◽  
Author(s):  
Zhi Hua Wang ◽  
Hong Wei Ma ◽  
Long Mao Zhao ◽  
Gui Tong Yang
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Aluminum Foams ◽  
Wide Range ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Dynamic Loading Conditions

The compressive deformation behavior of open-cell aluminum foams with different densities and morphologies was assessed under quasi-static and dynamic loading conditions. High strain rate experiments were conducted using a split Hopkinson pressure bar technique at strain rates ranging from 500 to 1 2000 − s . The experimental results shown that the compressive stress-strain curves of aluminum foams also have the “ three regions” character appeared in general foam materials, namely elastic region, collapse region and densification regions. It is found that density is the primary variable characterizing the modulus and yield strength of foams and the cell appears to have a negligible effect on the strength of foams. It also is found that yield strength and energy absorption is almost insensitive to strain rate and deformation is spatially uniform for the open-celled aluminum foams, over a wide range of strain rates.

scholarly journals Прогнозирование динамического предела текучести металлов с помощью двух структурно-временных параметров

2018 ◽  
Vol 60 (2) ◽  
pp. 240
Author(s):  
Н.С. Селютина ◽  
Ю.В. Петров
Keyword(s):  
Yield Strength ◽  
Incubation Time ◽  
Deformation Process ◽  
Empirical Models ◽  
Strain Rates ◽  
Loading History ◽  
Time Criterion ◽  
Temporal Features ◽  
Plastic Deformation Process ◽  
Wide Range

AbstractThe behavior of the yield strength of steel and a number of aluminum alloys is investigated in a wide range of strain rates, based on the incubation time criterion of yield and the empirical models of Johnson-Cook and Cowper-Symonds. In this paper, expressions for the parameters of the empirical models are derived through the characteristics of the incubation time criterion; a satisfactory agreement of these data and experimental results is obtained. The parameters of the empirical models can depend on some strain rate. The independence of the characteristics of the incubation time criterion of yield from the loading history and their connection with the structural and temporal features of the plastic deformation process give advantage of the approach based on the concept of incubation time with respect to empirical models and an effective and convenient equation for determining the yield strength in a wider range of strain rates.

scholarly journals Large Strain Mechanical Behavior of HSLA-100 Steel Over a Wide Range of Strain Rates

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Maen Alkhader ◽  
Laurence Bodelot
Keyword(s):  
Strain Rate ◽  
High Strain ◽  
Large Strain ◽  
Cold Work ◽  
High Strength ◽  
Adiabatic Shear ◽  
Strain Rates ◽  
Plastic Energy ◽  
Wide Range ◽  
Constitutive Response

High-strength low alloy steels (HSLA) have been designed to replace high-yield (HY) strength steels in naval applications involving impact loading as the latter, which contain more carbon, require complicated welding processes. The critical role of HSLA-100 steel requires achieving an accurate understanding of its behavior under dynamic loading. Accordingly, in this paper, we experimentally investigate its behavior, establish a model for its constitutive response at high-strain rates, and discuss its dynamic failure mode. The large strain and high-strain-rate mechanical constitutive behavior of high strength low alloy steel HSLA-100 is experimentally characterized over a wide range of strain rates, ranging from 10−3 s−1 to 104 s−1. The ability of HSLA-100 steel to store energy of cold work in adiabatic conditions is assessed through the direct measurement of the fraction of plastic energy converted into heat. The susceptibility of HSLA-100 steel to failure due to the formation and development of adiabatic shear bands (ASB) is investigated from two perspectives, the well-accepted failure strain criterion and the newly suggested plastic energy criterion [1]. Our experimental results show that HSLA-100 steel has apparent strain rate sensitivity at rates exceeding 3000 s−1 and has minimal ability to store energy of cold work at high deformation rate. In addition, both strain based and energy based failure criteria are effective in describing the propensity of HSLA-100 steel to dynamic failure (adiabatic shear band). Finally, we use the experimental results to determine constants for a Johnson-Cook model describing the constitutive response of HSLA-100. The implementation of this model in a commercial finite element code gives predictions capturing properly the observed experimental behavior. High-strain rate, thermomechanical processes, constitutive behavior, failure, finite elements, Kolsky bar, HSLA-100.

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