Elastic, Finite Deflection and Strain Rate Effects in a Mode Approximation Technique for Plastic Deformation of Pulse Loaded Structures

1980 ◽  
Vol 22 (4) ◽  
pp. 189-197 ◽  
Author(s):  
P. S. Symonds
Keyword(s):  
Strain Rate ◽  
General Scheme ◽  
Rate Sensitivity ◽  
Finite Geometry ◽  
Approximation Technique ◽  
Test Results ◽  
Rigid Plastic ◽  
Strain Rate Effects ◽  
Rate Effects ◽  
Clamped Beams

A general scheme is proposed for including effects of elastic deformation, finite geometry changes, and strain rate sensitivity in a simple approximate scheme for estimating maximum transient and permanent deformations in structures subjected to load pulses of high intensity. The method is applied here to fully clamped beams of mild steel subjected to explosive loading. Comparisons are made between estimates from the present method and test results, as well as with estimates by various rigid-plastic methods and (to a limited extent) with results from numerical methods.

Mechanical Behavior of a Rephosphorized Steel for Car Body Applications: Effects of Temperature, Strain Rate, and Pretreatment

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Yu Cao ◽  
Johan Ahlström ◽  
Birger Karlsson
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Rate Sensitivity ◽  
Uniaxial Tensile ◽  
Good Precision ◽  
Interstitial Free ◽  
Softening Effect ◽  
Strain Rate Effects ◽  
Uniaxial Tensile Testing ◽  
Rate Effects

Temperature and strain rate effects on the mechanical behavior of commercial rephosphorized, interstitial free steel have been investigated by uniaxial tensile testing, covering temperatures ranging from −60°C to +100°C and strain rates from 1×10−4 s−1 to 1×102 s−1 encompassing most conditions experienced in automotive crash situations. The effect of prestraining to 3.5% with or without successive annealing at 180°C for 30 min has also been evaluated. These treatments were used to simulate pressing of the plates and the paint-bake cycle in the production of car bodies. Yield and ultimate tensile strengths, ductility including uniform and total elongation and area reduction, thermal softening effect at high strain rate, and strain rate sensitivity of stress were determined and discussed in all cases. It was found that the Voce equation [σ=σs−(σs−σ0)exp(ε/ε0)] can be fitted to the experimental true stress-true plastic strain data with good precision. The parameter values in this equation were evaluated and discussed. Furthermore, temperature and strain rate effects were examined in terms of thermal and athermal components of the flow stresses. Finally, a thermal activation analysis was performed.

Strain-Rate Effects in the Dynamic Buckling of a Simple Elastic-Plastic Model

1997 ◽  
Vol 64 (1) ◽  
pp. 193-200 ◽  
Author(s):  
D. Karagiozova ◽  
N. Jones
Keyword(s):  
Strain Rate ◽  
Plastic Material ◽  
Rate Sensitivity ◽  
Dynamic Buckling ◽  
Strain Rate Effects ◽  
Plastic Model ◽  
Elastic Plastic ◽  
Rate Effects ◽  
Elastic Plastic Material ◽  
The Impact

The phenomenon of dynamic buckling is examined when the influence of material strain-rate sensitivity is retained in the basic equations for a simple elastic-plastic model with linear strain hardening when subjected to an impact by a mass. Two approaches are proposed for taking into account the material strain-rate effects and both use the Cowper-Symonds constitutive equation. The critical impact velocities depend on the impact mass and are determined for a wholly elastic material, a strain-rate insensitive elastic-plastic material and an elastic-plastic material with a dynamic yield force together with linear or nonlinear hardening due to the strain-rate effects. The results obtained show that both strain-rate sensitive models predict impact velocities which are higher than those predicted by the strain-rate insensitive idealization and that the influence of any initial imperfections is important for the three material models considered.

From Dislocation Cores to high Temperature Strain rate Effects in L12 Compounds

1990 ◽  
Vol 213 ◽  
Author(s):  
V. Vitek ◽  
Y. Sodani ◽  
J. Cserti
Keyword(s):  
Strain Rate ◽  
Yield Stress ◽  
Rate Sensitivity ◽  
Physical Models ◽  
Strain Rate Effects ◽  
Screw Dislocations ◽  
The Core ◽  
Rate Effects ◽  
Temperature Dependences ◽  
Further Development

ABSTRACTIt is now generally accepted that in many L12 compounds the yielding behavior is controlled by the special features of the cores of screw dislocations. In this paper we first summarize results of the atomistic studies of the core structures of the <110> screw dislocations in these compounds. At this point we show that, depending on the atomic bonding, two distinct classes of L12 alloys exist. In the first, represented by alloys like Ni3Al, a glissile configuration of the core exists on {111} planes although a sessile configuration is energetically more favored. In the second class, represented by alloys like Pt3A1 and A13Ti modified by alloying into L12 structure, the cores of screw dislocations are always sessile. Using the results of the atomistic studies we present physical models explaining the temperature dependences of the yield stress in both classes of L12 alloys. At this point we also present a further development of the model for the anomalous temperature dependence of the yield stress in alloys like Ni3A1, originally put forward by Paidar et al. [15]. In this development strain rate effects are included and it is shown that the model explains not only the orientation dependences of the yield stress in the anomalous regime but also the very low strain rate sensitivity observed in this regime.

Strain-rate effects in self-boring pressuremeter tests in clay

2006 ◽  
Vol 43 (9) ◽  
pp. 915-927 ◽  
Author(s):  
Vincenzo Silvestri
Keyword(s):  
Strain Rate ◽  
Radial Strain ◽  
Strain Curve ◽  
Soil Mass ◽  
Test Results ◽  
Pressuremeter Test ◽  
Strain Rate Effects ◽  
Expansion Curve ◽  
Rate Effects ◽  
Strain Relationship

A method is proposed for assessing the effect of strain rate on pressuremeter test results in clay. The approach takes into account the strain rate used to expand the cavity and its variation within the soil mass, both of which influence the value of the undrained shear strength deduced from the pressuremeter expansion curve. The method is applied to quantify strain-rate effects in idealized materials and in model pressuremeter test results. The pressuremeter-deduced stress–strain curve is also used to predict the total pressure – radial strain relationship observed in one of the model tests.Key words: pressuremeter test, clays, strain rate, idealized materials, model tests.

Test and Numerical Analysis of Underwater Explosion on Circular Plates

2012 ◽  
Vol 187 ◽  
pp. 74-79
Author(s):  
A.A. Sheikhi Koohsar ◽  
S.M.S. Nasereddini ◽  
E. Bazrafshan
Keyword(s):  
Numerical Analysis ◽  
Strain Rate ◽  
Good Accuracy ◽  
Underwater Explosion ◽  
Steel Plates ◽  
Test Results ◽  
Circular Plates ◽  
Two Phase ◽  
Strain Rate Effects ◽  
Rate Effects

Underwater explosion is a complex discussion because it has two phase environment including shock waves, bubble effects, cavitation, high strain rate, geometric and material non linearity. Results of underwater explosion tests on the circular steel plates have been discussd. Test results compared with numerical analysis results which it is done by LS-DYNA code. LS-DYNA is the software which is used to analyze large dynamic deflections by use of explicit method. We found that this code has good accuracy to predict the maximum deflections. Strain rate effects included in the program by use of Cowper-Symonds relation.

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