Institute of Fundamental Technological Research

This paper presents a systematic study of the thermo-viscoplastic behavior of a 304 austenitic stainless steel (ASS). The experiments were conducted over a wide range of strain rates (10^−3 s^−1 to 3270 s^−1) and temperatures (-163°C to 172°C), for which the deformation behavior of 304 ASS becomes more complex due to the strain-induced martensitic transformation (SIMT) effect. Dynamic tests at low/elevated temperatures were conducted using the Hopkinson technique coupled with a cooling device/heating furnace, and temperature distribution within the specimen was verified to be uniform. Experimental results showed that the strain hardening rate of 304 ASS was strongly affected by SIMT effect. For quasi-static tests (10^−3 s^−1 to 1 s^−1) at low temperatures (-163°C to -20°C), the stress-strain relations exhibited an S-shape and a second strain hardening phenomenon. The strain rate sensitivity and temperature sensitivity of 304 ASS were also different from metallic materials deformed by dislocation glide. Several unexpected phenomena including the negative strain rate sensitivity and the changing temperature sensitivity from quasi-static to dynamic tests were observed. Based on experimental results, an extension of the Rusinek-Klepaczko (RK) model considering SIMT effect was used to simulate the deformation behavior of 304 ASS: it predicted flow stress curves of 304 ASS above -60°C correctly. In addition, to validate the extended RK model and the identified model parameters, numerical simulations of ballistic impact tests of 304 ASS plates at various temperatures were carried out, showing a good agreement with experiments.

304 austenitic stainless steel, strain rate sensitivity, temperature sensitivity, constitutive model, ballistic impact test

The biaxial compression test, based on the concept presented in [1] and on the technique of the channel-die test [2] and [3], is discussed as an experimental method allowing evolution of the friction conditions from the dry-film lubrication, by using MoS2 grease, to the dry conditions to be analysed. This article gives an outline of the experimental set-up, its validation and the technique of the test results analysis. The analysis of friction is based on the experimental data coupled with the numerical simulation of the performed tests and on the theoretical approach introduced in [4]. The Oxygen-Free High Conductivity (OFHC) copper in the ‘as-received’ state in contact with the 42CrMo4 steel are chosen as the materials used for the experimental investigation.

Biaxial compression, Friction modelling, OFHC copper