G. Raghava

Evaluation of Cyclic Hardening Parameters for Type 304LN Stainless Steel

Engineering components are often subjected to cyclic load excursions beyond elastic limit and hence cyclic plastic deformation of engineering materials 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 of engineering materials. Also, cyclic hardening parameters are required in the design of structural components subjected to large plastic deformation. Constitutive equations were proposed by Prager, Armstrong and Frederick, Chaboche, and Ohno-Wang based on the stabilized strain-controlled hysteresis curve to evaluate the hardening parameters. In the present study, cyclic hardening parameters for SA 312 Type 304LN stainless steel have been determined based on the results of constant amplitude strain-controlled fatigue tests carried out earlier at CSIR-SERC under five different strain amplitude values, viz, 0.20%, 0.35%, 0.65%, 0.80% and 0.95%. It is observed that in isotropic hardening, the values of Q decreased with increase in strain amplitude. In kinematic hardening, the values of C1and γ1 are constant for all values of strain amplitude.

Studies on Fatigue Life of Typical Welded and Bolted Steel Structural Connections

This paper presents the results of fatigue tests conducted on typical welded and bolted connections made of IS 2062: 2011 steel and conforming to selected Constructional Details categorised in IS 800: 2007. The connection types include: longitudinal and transverse butt welded connections, fillet welded cruciform connections with load-carrying and non-load-carrying welds, and bolted (double cover butt type) connections. The tests were carried out at various values of maximum stress which were decided as a percentage of the yield strength of the base material. The S–N data obtained were compared with the characteristic S–N curves recommended in IS 800: 2007. In the case of transverse butt welded joints, all specimens which were tested at a maximum stress value equal to 65 % of the yield strength of the material and above, and one out of the two specimens tested at a maximum stress value equal to 60 % of the yield strength of the material failed to satisfy the codal provisions. Two out of the three cruciform joints with load-carrying welds tested at a maximum stress value equal to 80 % of the yield strength of the material failed to satisfy the codal provisions. Bolted specimens which were tested at a maximum stress value equal to 60 % of the yield strength of the material and above failed to satisfy the codal provisions.