The effect of medium strain rates on the mechanical properties of high performance steels (original) (raw)
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Metals, 2018
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 t...
High strain rate properties of fatigued advanced high strength steel sheets
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Before a possible crash, energy absorbing structural elements in cars are often subjected to an important number of loading cycles. It is known that the mechanical properties of the material used for these elements can be significantly influenced by an possible fatigue. Therefore, the influence of the fatigue on the impact-dynamic behaviour of three advanced high strength steel sheets is investigated. Next to static experiments, a series of split Hopkinson tensile bar experiments is performed on a dual phase steel (DP600 Z), a TRIP steel (TRIP700 Z) and an austenitic stainless steel (301LN 2B). During these experiments as-received and fatigued material is subjected to strain rates ranging from 250/s to 1200/s. The experiments clearly show that both the deformation properties and the yield stresses, and thus the energy absorbing potential, are strongly influenced by the fatigue. Due to the fatigue, the strength of all materials considered in this study increases considerably, however the material becomes significantly more brittle. The influence of is most pronounced for the austenitic steel.
Effect of Strain Rate on Material Properties of Sheet Steels
Journal of Structural Engineering-asce, 1992
The liver is one of the most frequently injured organs in abdominal trauma. Although motor vehicle collisions are the most common cause of liver injuries, current anthropomorphic test devices are not equipped to predict the risk of sustaining abdominal organ injuries. Consequently, researchers rely on finite element models to assess the potential risk of injury to abdominal organs such as the liver. These models must be validated based on appropriate biomechanical data in order to accurately assess injury risk. This study presents a total of 36 uniaxial unconfined compression tests performed on fresh human liver parenchyma within 48 h of death. Fach specimen was tested once to failure at one of four loading rates (0.012, 0.106, 1.036, and 10.708s'') in order to investigate the effects of loading rate on the compressive failure properties of human liver parenchyma. The results of this study showed that the response of human liver parenchyma is both nonlinear and rate dependent. Specifically, failure stress significantly increased with increased loading rate, while failure strain significantly decreased with increased loading rate. The failure stress and failure strain for all liver parenchyma specimens ranged from-38.9 kPa to-145.9kPa and from-0.48 strain to-1.15 strain, respectively. Overall, this study provides novel biomechanical data that can be used in the development of rate dependent material models and the identification of tissue-level tolerance values, which are critical to the validation of finite element models used to assess injury risk.
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The growing use of high strength steels in the automotive industry, to improve the crashworthiness and the light-weighting of the car body, requires the knowledge of their behaviour over a large range of strain-rates. The accuracy of the results in medium and high strain-rate tests is often strongly influenced by the experimental techniques used for the mechanical characterization of materials. Moreover, the precision of the constitutive law in reproducing the actual behaviour of the materials has important consequences in the correctness of design and assessment of car body structures subjected to impact loading. The paper presents the experimental techniques used to carry out dynamic tensile tests on thin sheet specimens. The research includes several Advanced High Strength Steels as Dual-Phase steels, TRansformation Induced Plasticity steels, etc. The tests have been carried out in the three strain-rate regimes (1-5, 10-50 and 500 s x1 ). The comparison of the dynamic stress-strain curves of three DP steels is presented and discussed.
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The Effect of Strain Rate on the Mechanical Properties of Automotive Steel Sheets
Acta Polytechnica, 2013
The automotive industry is currently seeking detailed information about various types of materials and their behavior under dynamic loading. Dynamic tensile testing of sheet steels is growing in importance. The experimental dynamic tensile technique depends on the strain rate. Each type oftest serves for a specific range of strain rates, and provides specific types of information. This workdeals with the influence of the strain rate on the mechanical properties of automotive steel sheets.Three different types of steel: IF steel, DP steel, and micro-alloyed steel (S 460) were used to compare static and dynamic properties.
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The occupants protection in vehicle crashes is directly related to the “safety capability” of the vehicles themselves: crash avoidance systems, passive safety devices and crashworthiness structures are all important to reduce injury risks for passengers but the vehicle structure’s ability to manage the impact energy represents the main line of defense. Traditionally the material choice for vehicles body has been carbon steel due to its easy of manufacturing, energy absorption capability and relative low costs. However, in the last years, the exigency to match new targets such as weight reduction (and then fuel economy), durability, crashworthiness and limited NVH levels (Noise, Vibration and Harshness) moved the interest toward other materials. In this context a more and more significant role is coming by stainless steels; their high mechanical properties, very high energy absorption capabilities, excellent formability/strength rate, high corrosion resistance and many other importan...
Identification of the dynamic tensile properties of metals under moderate strain rates
Stainless steel 316L, titanium alloy grade 7, and alloy C22 are currently under consideration as candidate materials for use in various components associated with the spent nuclear fuel package, which must be designed to withstand structural deformation caused by static, thermal, and handling loads. In addition, it has to maintain its integrity in case of accidents, where it may be
1990
The liver is one of the most frequently injured organs in abdominal trauma. Although motor vehicle collisions are the most common cause of liver injuries, current anthropomorphic test devices are not equipped to predict the risk of sustaining abdominal organ injuries. Consequently, researchers rely on finite element models to assess the potential risk of injury to abdominal organs such as the liver. These models must be validated based on appropriate biomechanical data in order to accurately assess injury risk. This study presents a total of 36 uniaxial unconfined compression tests performed on fresh human liver parenchyma within 48 h of death. Fach specimen was tested once to failure at one of four loading rates (0.012, 0.106, 1.036, and 10.708s'') in order to investigate the effects of loading rate on the compressive failure properties of human liver parenchyma. The results of this study showed that the response of human liver parenchyma is both nonlinear and rate dependent. Specifically, failure stress significantly increased with increased loading rate, while failure strain significantly decreased with increased loading rate. The failure stress and failure strain for all liver parenchyma specimens ranged from-38.9 kPa to-145.9kPa and from-0.48 strain to-1.15 strain, respectively. Overall, this study provides novel biomechanical data that can be used in the development of rate dependent material models and the identification of tissue-level tolerance values, which are critical to the validation of finite element models used to assess injury risk.