A finite element study on effect of frictional heating in the taylor rod impact problem

2014 ◽  
Vol 11 (6) ◽  
pp. 529-542 ◽  
Author(s):  
Sachin Gautam ◽  
Ravindra Saxena
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
High Strain ◽  
Frictional Heating ◽  
Equivalent Plastic Strain ◽  
Surface Friction ◽  
Effect Of Temperature ◽  
Element Formulation ◽  
Strain Rates ◽  
High Strain Rates

In an impact phenomenon the material is subjected to very short duration high force levels resulting large plastic deformations and rise in temperature at high strain rates. A circular rod impacting against a rigid surface called as Taylor rod impact test is widely used for determining the mechanical behaviour of materials subjected to high strain rates with associated increase in temperature. A three-dimensional large deformation, thermo-elasto-plastic, dynamic, contact, finite element formulation is developed to study the effect of temperature rise due to plastic deformation and surface friction on the deformation and stress fields. It is found that the predicted equivalent plastic strain values are influenced by temperature generated due to plastic deformation and surface friction. The values of the coefficient of friction have a profound effect on the location of fracture initiation on the impacting face in a circular rod.

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.

Effect of Temperature and Strain Rate on the Mechanical Properties of 99.5 Aluminium Rods Extruded by KOBO

2016 ◽  
Vol 879 ◽  
pp. 230-235
Author(s):  
Sonia Boczkal ◽  
Marzena Lech-Grega ◽  
Wojciech Szymanski ◽  
Paweł Ostachowski ◽  
Marek Lagoda
Keyword(s):  
Strain Rate ◽  
Room Temperature ◽  
High Strain ◽  
Effect Of Temperature ◽  
Recrystallization Process ◽  
Extrusion Force ◽  
Strain Rates ◽  
High Strain Rates ◽  
Constant Frequency ◽  
Increasing Temperature

In this study, aluminium rods were cold extruded in a direct process by KOBO method in two variants: variant I with varying (decreasing) frequency of die oscillations necessary to maintain a constant extrusion force, and variant II with constant frequency of die oscillations, leading to a decrease in the extrusion force. The tensile test of rods was carried out in a temperature range of 20 - 200°C and at a strain rate from 8xE10-5 to 8xE10-1 s-1. Significant differences in the elongation of the tested rods were observed. It was found that rods extruded at variable die oscillations and stretched at room temperature had similar elongation, independent of the strain rate. With the increase of temperature, the elongation of samples stretched at a low speed was growing from a value of about 8% at room temperature up to 40% at 200°C. At high strain rates, despite the increasing temperature, the elongation remained at the same level, i.e. 5-6%. In rods extruded at constant die oscillations, the elongation at a low strain rate was growing with the temperature from 10% at room temperature up to 29% at 200°C. At high strain rates, the elongation decreased from 28% at room temperature to 11% at 200°C. The results were interrelated with examinations of the structure of rods and fractures of tensile specimens. In the material extruded by KOBO method with constant die oscillations, the beginnings of the recrystallization process were observed, absent in the material extruded at variable die oscillations.

Rate Dependent Deformation of Semi-Crystalline Polypropylene Near Room Temperature

1997 ◽  
Vol 119 (3) ◽  
pp. 216-222 ◽  
Author(s):  
E. M. Arruda ◽  
S. Ahzi ◽  
Y. Li ◽  
A. Ganesan
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Room Temperature ◽  
Strain Softening ◽  
High Strain ◽  
Constant Strain Rate ◽  
Strain Rates ◽  
High Strain Rates ◽  
Rate Dependent ◽  
Static Conditions

We examine the strain rate dependent, large plastic deformation in isotropic semi-crystalline polypropylene at room temperature. Constant strain rate uniaxial compression tests on cylindrical polypropylene specimens show very little true strain softening under quasi-static conditions. At high strain rates very large amounts (38 percent) of apparent strain softening accompanied by temperature rises are recorded. We examine the capability of a recently proposed constitutive model of plastic deformation in semi-crystalline polymers to predict this behavior. We neglect the contribution of the amorphous phase to the plastic deformation response and include the effects of adiabatic heating at high strain rates. Attention is focused on the ability to predict rate dependent yielding, strain softening, strain hardening, and adiabatic temperature rises with this approach. Comparison of simulations and experimental results show good agreement and provide insight into the merits of using a polycrystalline modeling assumption versus incorporating the amorphous contribution. Discrepancies between experiments and model predictions are explained in terms of expectations associated with neglecting the amorphous deformation.

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