scholarly journals Interactions of negative strain rate sensitivity, martensite transformation, and dynamic strain aging in 3rd generation advanced high-strength steels

2019 ◽  
Vol 754 ◽  
pp. 140-151 ◽  
Author(s):  
Michael Callahan ◽  
Astrid Perlade ◽  
Jean-Hubert Schmitt
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Martensite Transformation ◽  
Strain Aging ◽  
High Strength Steels ◽  
Rate Sensitivity ◽  
High Strength ◽  
Dynamic Strain ◽  
Advanced High Strength Steels ◽  
Negative Strain Rate Sensitivity

Advanced High Strength Steels for Automobile Body Structures

2007 ◽  
Vol 539-543 ◽  
pp. 4386-4390 ◽  
Author(s):  
M. Takahashi ◽  
A. Uenishi ◽  
H. Yoshida ◽  
H. Kuriyama
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
High Strength Steels ◽  
Rate Sensitivity ◽  
High Strength ◽  
Thin Wall ◽  
Advanced High Strength Steels ◽  
Limited Length ◽  
Side Collision ◽  
Frontal Collisions

There has been a big demand for increased vehicle safety and weight reduction of auto-bodies. An extensive use of high strength steels is one of the ways to answer the requirement. Since the crashworthiness is improved by applications of higher strength steels to crashworthiness conscious structural components, various types of advanced high strength steels have been developed. The crash energy during frontal collisions is absorbed by the buckling and bending deformations of thin wall tube structures of the crushable zone of auto-bodies. In the case of side collision, on the other hand, a limited length of crushable zone requires the components to minimize the deformation during the collision. The lower the strength during press forming, the better the press formability is expected. However, the higher the strength at a collision event, the better the crashworthiness can be obtained. It can, therefore, be concluded that steels with higher strain rate sensitivities are desired. Combinations of soft ferrite phase and other hard phases were found to improve the strain rate sensitivity of flow stresses. Bake hardening is also one of the ways to improve the strain rate sensitivity of flow stresses.

Incorporation of Dynamic Strain Aging Into a Viscoplastic Self-Consistent Model for Predicting the Negative Strain Rate Sensitivity of Hadfield Steel

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
B. Bal ◽  
B. Gumus ◽  
D. Canadinc
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
Strain Rate Sensitivity ◽  
Strain Aging ◽  
Rate Sensitivity ◽  
Atomic Level ◽  
Hadfield Steel ◽  
Dynamic Strain ◽  
Deformation Response ◽  
Negative Strain Rate Sensitivity

A new multiscale modeling approach is proposed to predict the contributions of dynamic strain aging (DSA) and the resulting negative strain rate sensitivity (NSRS) on the unusual strain-hardening response of Hadfield steel (HS). Mechanical response of HS was obtained from monotonic and strain rate jump experiments under uniaxial tensile loading within the 10−4 to 10−1 s−1 strain rate range. Specifically, a unique strain-hardening model was proposed that incorporates the atomic-level local instabilities imposed upon by the pinning of dislocations by diffusing carbon atoms to the classical Voce hardening. The novelty of the current approach is the computation of the shear stress contribution imposed on arrested dislocations leading to DSA at the atomic level, which is then implemented to the overall strain-hardening rule at the microscopic level. The new model not only successfully predicts the role of DSA and the resulting NSRS on the macroscopic deformation response of HS but also opens the venue for accurately predicting the deformation response of rate-sensitive metallic materials under any given loading condition.

scholarly journals Effect of Aging Process on the Strain Rate Sensitivity in V-Containing TWIP Steel

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 126
Author(s):  
Shaoheng Sun ◽  
Zhiyong Xue
Keyword(s):  
Tensile Strength ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Strain Aging ◽  
Aging Process ◽  
Vanadium Carbide ◽  
Twip Steel ◽  
Rate Sensitivity ◽  
Dynamic Strain ◽  
Negative Strain Rate Sensitivity

The dynamic tensile behavior of the twinning-induced plasticity (TWIP) steel with the vanadium carbide is investigated at different strain rates of 10−4, 10−3, 10−2 and 0.05 s−1. Microstructure characterization, carried out using back scatter electron diffraction (EBSD) and transmission electron microscopy (TEM), shows a homogeneous face center cubic structured matrix with uniformly dispersed vanadium carbide. The vanadium carbide is controlled by the aging temperature and time. The best comprehensive mechanical properties are achieved when the tested steel is aged at 550 °C for 5 h. With the increase of strain rate, the tensile strength and work hardening rate decrease, and the tested material shows negative strain rate sensitivity. This would be due to an increase in stacking fault energy caused by temperature rise by adiabatic heating, which must suppress the formation of twinning. On the other hand, the strain rate sensitivity is affected by dynamic strain aging (DSA). With the increase of strain rate, the DSA weakens, which causes negative strain rate sensitivity. The tensile strength and strain rate sensitivity value both increase first and then decrease with the increase of vanadium carbide size. This is because the tensile strength is mainly affected by the vanadium carbide. In addition to the vanadium carbide, the strain rate sensitivity is also affected by the amount of solute atom (V and C) during the dynamic strain aging process.

Stress-State, Temperature, and Strain Rate Dependence of Vintage ASTM A7 Steel

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
S. A. Brauer ◽  
W. R. Whittington ◽  
H. Rhee ◽  
P. G. Allison ◽  
D. E. Dickel ◽  
...  
Keyword(s):  
Stress State ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Rate Dependence ◽  
Maximum Strength ◽  
Strain Rate Dependence ◽  
Dynamic Strain ◽  
Strength Increase ◽  
Negative Strain Rate Sensitivity

The structure–property relationships of a vintage ASTM A7 steel is quantified in terms of stress state, temperature, and strain rate dependence. The microstructural stereology revealed primary phases to be 15.8% ± 2.6% pearlitic and 84.2% ± 2.6 ferritic with grain sizes of 13.3 μm ± 3.1 μm and 36.5 μm ± 7.0 μm, respectively. Manganese particle volume fractions represented 0.38–1.53% of the bulk material. Mechanical testing revealed a stress state dependence that showed a maximum strength increase of 85% from torsion to tension and a strain rate dependence that showed a maximum strength increase of 38% from 10−1 to 103 s−1at 20% strain. In tension, a negative strain rate sensitivity (nSRS) was observed in the quasi-static rate regime yet was positive when traversing from the quasi-static rates to high strain rates. Also, the A7 steel exhibited a significant ductility reduction as the temperature increased from ambient to 573 K (300 °C), which is uncommon for metals. The literature argues that dynamic strain aging (DSA) can induce the negative strain rate sensitivity and ductility reduction upon a temperature increase. Finally, a tension/compression stress asymmetry arises in this A7 steel, which can play a significant role since bending is prevalent in this ubiquitous structural material. Torsional softening was also observed for this A7 steel.

Amplitude Equation for a Dynamic Strain Aging Model: Beyond Linear Stability Analysis of Serrated Flow in Metallic Alloys

2000 ◽  
Vol 652 ◽  
Author(s):  
Sergey N. Rashkeev ◽  
Michael V. Glazov ◽  
Frédéric Barlat ◽  
Daniel J. Lege
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Qualitative Difference ◽  
Rate Sensitivity ◽  
Sudden Onset ◽  
Dynamic Strain ◽  
Strain Rates ◽  
Serrated Flow ◽  
Negative Strain Rate Sensitivity ◽  
First Case

ABSTRACTA method for construction of “processing windows” to avoid negative strain rate sensitivity and associated serrated flow in some aluminum alloys is described. The method is based on the amplitude Ginzburg-Landau (GL) equations and analysis of bifurcation diagrams. The mathematical technique developed in the present work was applied to a specific aluminum alloy, Al-0.4%Mg-0.2%Si considered earlier in the literature [1-3], and yielded good results in terms of predicting the negative strain rate sensitivity regions in the “strain rate “temperature” parameter space. Using the GL-analysis it was demonstrated that even though the instability area is located in the region of intermediate strain rates, a qualitative difference exists between the areas of (relatively) fast and (relatively) slow strain rates. In the first case the dynamic behavior of the system is supercritical, in the second case it is subcritical. The second case is highly undesirable because it causes a sudden onset of stable stress serrations that are difficult to suppress, while in the first case the development of instability is gradual and, consequently, more easily controllable.

The Effect of Strain Rate on Yielding in High Strength Steels

1966 ◽  
Vol 88 (1) ◽  
pp. 37-44 ◽  
Author(s):  
D. P. Kendall ◽  
T. E. Davidson
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Power Law ◽  
High Strength Steels ◽  
Rate Sensitivity ◽  
High Strength ◽  
Strain Rates ◽  
Alloy Steels ◽  
Strength Alloy ◽  
Continuous Power

The effect of strain rates ranging from 10−4 to 10 in/in/sec on the yield strengths of several high strength alloy steels is investigated. Quenched and tempered-type alloys exhibit two regions of strain-rate sensitivity with the strain rate dividing the sensitive and insensitive regions varying from 0.5 to greater than 10 in/in/sec, depending on composition, microstructure and grain size. At the higher rates a power-law relationship is found which is consistent with a yielding model involving breakaway of dislocations from solute atmospheres. Maraging steel exhibits a continuous power law-strain rate sensitivity over the entire range.

Sign in / Sign up

Export Citation Format

Share Document