Metal fatigue can start without defects, new study shows
Scientists discovered that cracks in stainless steel can initiate deep inside the material even when no inclusions or defects are present—a finding that upends decades of assumptions. The discovery has implications for industries relying on components subjected to extreme cycles, from aerospace to power generation, potentially requiring new safety standards and material testing protocols.
Originaltitel: On fatigue crack origin with a fine granular area in matrix without defect
<p>Fatigue crack initiation in metallic materials during very high cycle fatigue has been characterized by a subsurface crack origin with defect such as an inclusion. In this paper, fatigue damage behavior in an austenitic stainless steel has been studied using a novel progressive stepwise load increasing test method with each cycle step higher than 108 cycles. Subsurface crack origin with a fine granular area has formed in the matrix without defect. This is a new phenomenon. The mechanism has been investigated using Focused Ion Beam crosssectioning and electron channeling contrast imaging techniques. Strain localization, grain fragmentation and local plasticity exhaustion are the main factors that cause fatigue damage and crack initiation in the matrix. This study provides a fundamental understanding how material damage and crack initiation occur in material matrix during very high cycle fatigue.</p>