Cyclic Plastic Deformation Behaviour of SA 312 Type 304LN Stainless Steel

Avinash Ethirajan, M. Saravanan, S. Vishnuvardhan, J. Jeyanthi

Many engineering components are often subjected to cyclic load excursions beyond elastic limit and hence cyclic plastic deformation in such components becomes inevitable.  Since the resultant elastic-plastic stress-strain response of the material plays a pivotal role in analysis, design and failure of the component, it becomes important to understand the cyclic plastic deformation behaviour.  Strain-controlled fatigue is an important consideration in the design of components that undergo either mechanically or thermally induced cyclic plastic strains which may cause failure in low number of cycles (approximately <105).  This paper presents the details of strain-controlled low cycle fatigue tests carried out on SA 312 Type 304LN stainless steel material.  ASTM E 606 - 12 was followed in preparing the test specimens and carrying out the fatigue tests.  The tests were carried out under constant amplitude cyclic triangular waveform loading.  The specimens were tested at six different strain amplitudes of ±1.10%, ±1.25%, ±1.40%, ±1.55%, ±1.70% and ±1.85%.  Cyclic stress-strain hysteresis curves were obtained throughout the entire duration of the fatigue tests.  The number of cycles to failure of the specimens was recorded.  Using the empirical relationships, fatigue parameters, namely cyclic strength coefficient, cyclic strain hardening exponent, fatigue strength coefficient, fatigue strength exponent, fatigue ductility coefficient and fatigue ductility exponent were evaluated; the values of the same were found to be 414.66 MPa, 0.2048, 777.54 MPa, -0.1010, 0.1955 and -0.4780 respectively.  These fatigue parameters will be useful in determining the number of fatigue loading cycles for fatigue-ratcheting crack initiation in components made of this material.