Fracture behavior of rod-in-tube layered configurations under three-point bending: an experimental investigation

Ensuring adequate fracture resistance in structural components is a critical challenge in engineering applications, as sudden crack propagation can lead to catastrophic failure. This study investigates the fracture behavior of novel rod-in-tube layered configuration using EN8 steel, aimed at enhancing fracture resistance and delaying catastrophic failure. Specimens were prepared in accordance with ASTM standards and subjected to three-point bend tests. Stress intensity factor (SIF) values were evaluated over load point displacement and time to assess crack propagation behavior. Compared to plain rod specimens, the layered configurations demonstrated a two-stage crack growth process characterized by initial steady crack propagation and subsequent delayed failure, attributed to the presence of a physical interface that arrests crack growth and redistributes stress. The configuration with an 8 mm diameter inner rod proved as effective, extending the time to failure by approximately 115% when tested and compared with plain rod. The findings affirm the layered design’s effectiveness in enhancing both safe-life and fail-safe performance, offering a promising approach for improving fracture tolerance in structural applications.