436 Selected Topics of Contemporary Solid Mechanics Mechanical behaviour of TRIP steels subjected to low impact velocity at wide range of temperatures J. A. Rodríguez-Martínez 1 , A. Rusinek 2 , D. A. Pedroche 1 , A. Arias 1 , J. R. Klepaczko 2 1 Department of Continuum Mechanics and Structural Analysis, University Carlos III of Madrid, Avda. de la Universidad 30, 28911 Leganés, Madrid, Spain 2 Laboratory of Physics and Mechanics of Materials, UMR CNRS 7554, University Paul Verlaine of Metz, Ile du Saulcy, 57000 Metz, France 1. Introduction The response of materials under impact loading has a considerable interest. It allows for clarification of several problems in different application fields such as civil, military, aeronautical and automotive engineering, [1-2]. The use of TRIP steels is widespread in the industry as a structural element responsible for the absorption of energy during an eventual impact or accident as for example in crashworthiness application. Thus, in the present work mechanical behaviour of TRIP 600 and TRIP 1000 sheets subjected to low impact velocity at different initial temperatures is analyzed. 2. Experimental setup For this task a drop weight tower has been used. Thus, it was possible to perforate the TRIP steel sheets for initial velocities s / m 5 V 0 ≤ in a wide range of initial temperatures K 373 T K 173 0 ≤ ≤ . The dimensions of the square sheets impacted are 100 100 x mm. The steel sheets of thickness t = 1.0 mm and t = 0.5 mm in the case of TRIP 600 and TRIP 1000 respectively. The impactor used had a shape of conical nose with diameter of mm 20 p = φ and mass of kg 7 . 18 M p = . The experimental set-up allows to obtain measurements of the force-time history and both, the initial and residual velocities. Finally, the process has been filmed using a high speed camera. 3. Mechanical characterization of TRIP 600 and TRIP 1000 The mechanical behaviour of both, TRIP 600 and TRIP 1000, has been defined using different strain rates and initial temperatures, Figs 1-2. In Fig. 1 experimental results are reported for TRIP 600 and TRIP 1000 at room temperature for different strain rates. For TRIP 1000 a Lüders’ band propagation is also observed corresponding to a plateau of stress at the beginning of loading, Fig. 1-b. (a) 450 500 550 600 650 0 0,005 0,01 0,015 0,02 0,025 0,03 TRIP 1000 To = 300 K - 0.001 1/s True stress, σ (MPa) True strain, ε 2 1 3 4 0 ε L (b) Fig. 1. Experimental results for TRIP 600 and TRIP 1000 steels at room temperature and different strain rates The influence of the temperature on the behaviour of the materials studied is shown in Fig. 2. It is observed a strong dependency of the strain hardening with temperature http://rcin.org.pl