scholarly journals Mechanical behaviour modelling under dynamic conditions: Application to structural and high strength steels

2018 ◽  
Vol 183 ◽  
pp. 01056
Author(s):  
Pierre Simon ◽  
Yaël Demarty ◽  
Alexis Rusinek
Keyword(s):  
Strain Rate ◽  
Dynamic Loading ◽  
High Strain ◽  
Constitutive Relations ◽  
High Strength Steels ◽  
Rate Sensitivity ◽  
High Strength ◽  
Numerical Approach ◽  
Large Field ◽  
Dynamic Conditions

Current needs in the design and optimization of complex ballistic protection structures lead to the development of more and more accurate numerical modelling for high impact velocity. The aim of developing such a tool is to be able to predict the protection performance of structures using few experiments. Considering only numerical approach, most important issue to have a reliable simulation is to focus on material behaviour description in term of constitutive relation and failure model for high strain rates, large field of temperatures and complex stress states. In this context, the study deals with the behaviour of two steels including a high strength steel and a structural steel. For this application, the materials can undergo both quasi-static and dynamic loading. Thus the strain rate range studied is varying from 10−3 to more than 103 s−1. Although the high strength steels do not exhibit high strain rate sensitivity, the temperature increases during dynamic loading is inducing thermal softening. Thus, temperature sensitivity is defined up to 500 K under quasi-static and dynamic conditions. Then, experiments are used to define the parameters of several constitutive relations like the Johnson-Cook model or the Rusinek Klepaczko model.

Warm-Forging Characteristics and Microstructural Response of Medium-Carbon High-Strength Steels for High-Duty Components

2014 ◽  
Vol 611-612 ◽  
pp. 167-172 ◽  
Author(s):  
Piotr Skubisz ◽  
Łukasz Lisiecki
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Microstructure Evolution ◽  
High Strain ◽  
Deformation Behaviour ◽  
Metal Flow ◽  
High Strength Steels ◽  
High Strength ◽  
Medium Carbon ◽  
Warm Forging

Paper presents deformation behaviour and microstructural response of selected medium-carbon high-strength steels commonly used for high-duty components deformed under high-strain-rate and warm work temperature range. The investigation of material behaviour is oriented at analysis of hot and warm workability of material and microstructure evolution resultant from deformation mechanisms, strain induced recrystallization and hardening at temperatures of lower forging regime and high strain rate deformation. The effect of these factors on microstructure after forging and subsequent direct-cooling was studied. Metallographic work aided with numerical methods of simulation of the metal flow and microstructure evolution during forging were used to correlate thermo-mechanical parameters observed with microstructure and mechanical properties after forging and cooling.

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.

IMPROVED MECHANICAL PROPERTY OF ELECTRODEPOSITED NANOCRYSTALLINE NICKEL-COBALT ALLOY

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2285-2290 ◽  
Author(s):  
XIXUN SHEN ◽  
JIANSHE LIAN
Keyword(s):  
Strain Rate ◽  
High Strain ◽  
Rate Sensitivity ◽  
High Strength ◽  
Strain Rate Range ◽  
Nickel Cobalt ◽  
Average Grain Size ◽  
High Strain Rate Sensitivity ◽  
Small Activity ◽  
Very High

A bulk and dense nc Ni -24.7% Co with an average grain size of 15nm was fabricated by a direct current electrodeposition. This Ni -24.7% Co exhibits very high tensile strength of 1813MPa to 2232MPa with relatively good tensile ductility of 6.0%~9.6% under tensile test over a wide strain rate range of 0.417s-1 ~ 1.35×10-5s-1. The combination of high strength and good ductility should be attributed to the increased strain hardening ability induced by the addition of alloying Co element. The interaction of dislocation and grain boundaries is the rate-controlling deformation mechanism controlled in the Ni -24.7% Co based on its high strain rate sensitivity of 0.029 and small activity volume of ~14b3.

scholarly journals Material Behavior Description for a Large Range of Strain Rates from Low to High Temperatures: Application to High Strength Steel

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 795 ◽  
Author(s):  
Pierre Simon ◽  
Yaël Demarty ◽  
Alexis Rusinek ◽  
George Voyiadjis
Keyword(s):  
High Strength Steel ◽  
Constitutive Relations ◽  
High Strength ◽  
Numerical Approach ◽  
Complex Stress ◽  
Material Behavior ◽  
Experimental Results ◽  
Large Field ◽  
Strain Rates ◽  
Behavior Description

Current needs in the design and optimization of complex protective structures lead to the development of more accurate numerical modelling of impact loadings. The aim of developing such a tool is to be able to predict the protection performance of structures using fewer experiments. Considering only the numerical approach, the most important issue to have a reliable simulation is to focus on the material behavior description in terms of constitutive relations and failure model for high strain rates, large field of temperatures and complex stress states. In this context, the present study deals with the dynamic thermo-mechanical behavior of a high strength steel (HSS) close to the Mars® 190 (Industeel France, Le Creusot, France). For the considered application, the material can undergo both quasi-static and dynamic loadings. Thus, the studied strain rate range is varying from 10−3–104 s−1. Due to the fast loading time, the local temperature increase during dynamic loading induces a thermal softening. The temperature sensitivity has been studied up to 473 K under quasi-static and dynamic conditions. Low temperature measurements (lower than the room temperature) are also reported in term of σ − ε | ε ˙ , T curves. Experimental results are then used to identify the parameters of several constitutive relations, such as the model developed initially by Johnson and Cook; Voyiadjis and Abed; and Rusinek and Klepaczko respectively termed Johnson–Cook (JC), Voyiadjis–Abed (VA), and Rusinek–Klepaczko (RK). Finally, comparisons between experimental results and model predictions are reported and compared.

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.

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