Abstract
Fatigue behaviour of DIN 34CrNiMo6 lateral notched round bars subjected to in-phase bending-torsion loading was investigated. Experimental tests were conducted under constant amplitude loading with stress ratios close to zero. Crack initiation and crack growth were monitored in-situ using a high-resolution digital system. Fracture surfaces were examined by scanning electron microscope (SEM). A multi-crack initiation phenomenon from material defects at the notch surface was found. The SEM analyses revealed the presence of relatively high inclusions with sizes ranging from 2 to 30 μm. Finally, fatigue life predictions were carried out using both the Coffin-Manson (CM) and the Smith-Watson-Topper (SWT) models. The notch effect was simulated with the Theory of Critical Distances (TCD) and the Equivalent Strain Energy Density (ESED) concept. Regardless of the model, very good correlations between experimental and predicted fatigue lives were observed, particularly for lives greater than 10 4 cycles.
Highlights
DIN 34CrNiMo6 high strength steel is a very versatile engineering material
The notch effect was simulated with the Theory of Critical Distances (TCD) and the Equivalent Strain Energy Density (ESED) concept
Fatigue behaviour of lateral notched round bars made of DIN 34CrNiMo6 high strength steel subjected to in-phase combined bending-torsion loading is investigated
Summary
DIN 34CrNiMo6 high strength steel is a very versatile engineering material It combines high ductility, deep hardenability, toughness and strength. Due to these exceptional properties, it is ideal for critical components such as pinions, crankshafts, connecting rods, axles, torsion bars, among others. These components have severe geometric discontinuities and work under complex loading. Tests were conducted under constant-amplitude loading with stress ratios close to zero.
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