Tensile and wear properties of repetitive corrugation and straightened Al 2024 alloy: an experimental and RSM approach

Repetitive Corrugation and Straightening (RCS) on sheet geometries causes Cyclic Plastic Deformation, resulting in potential improvements of mechanical characteristics in metals and alloys. In this study, sample sheets of Al 2024 are subjected to severe plastic deformation with specially designed corrugated rollers to generate heterogeneous repeated plastic deformation at room temperature. The material shows enhanced properties under severe plastic deformation, with 5.07% increase in tensile strength, compared to unprocessed material. Maximum tensile strength was observed at annealed temperature of 150 °C is of about 3.49% increase in tensile strength over other temperature conditions. A wear study was carried out by considering the processed sheet that yields high tensile strength (annealed at 150 °C) by varying process parameters like sliding distance, load and sliding velocity as per design of experiments. In comparison to all other combinations, the wear resistance was shown to be better with a sliding distance of 6000 m, a load of 9.81 N, and a sliding velocity of 1.45 m s−1. The Response Surface Methodology (RSM) approach was adopted for comparing purpose, the experimental findings are found to be more similar to the RSM approach’s outcomes.

Numerical Prediction of the Fatigue Crack Growth Rate in SLM Ti-6Al-4V Based on Crack Tip Plastic Strain

This study presents a numerical model to predict the fatigue crack growth (FCG) rate in compact tension specimens under constant amplitude cyclic loadings. The material studied is the Ti-6Al-4V titanium alloy produced by selective laser melting, which was submitted to two different post-treatments: (i) hot isostatic pressing, and (ii) heat treatment. The developed finite element model uses the cumulative plastic strain at the crack tip to define the nodal release. Two different FCG criteria are presented, namely the incremental plastic strain (IPS) criterion and the total plastic strain (TPS) criterion. The calibration of the elasto-plastic constitutive model was carried out using experimental data from low cycle fatigue tests of smooth specimens. For both proposed crack growth criteria, the predicted da/dN-ΔK curve is approximately linear in log-log scale. However, the slope of the curve is higher using the TPS criterion. The numerical predictions of the crack growth rate are in good agreement with the experimental results, which indicates that cyclic plastic deformation is the main damage mechanism. The numerical results showed that increasing the stress ratio leads to a shift up of the da/dN-ΔK curve. The effect of stress ratio was dissociated from variations of cyclic plastic deformation, and an extrinsic mechanism, i.e., crack closure phenomenon, was found to be the cause.