Estimating the elastic modulus and bending stiffness of steel ruler with crack using three-point bending test

Cracks are the early signs of distress in structures and must be diagnosed accurately. They reduce the structural stiffness, strength, and may adversely affect the behavior of the structure. This study aims to estimate the elastic modulus and the bending stiffness of a steel ruler with varying crack lengths. A low cost and simple three-point bending test was used for the measurements. A pristine ruler and rulers with three different crack lengths were subjected to loads of up to 6 kg (roughly 13 lbs) and the displacement close to the load location was measured. The load and displacement at the center of the specimen, for loading and unloading, were measured at equal load steps. The effect of a crack on the elastic modulus and the bending stiffness was compared with that of the pristine ruler. Permanent deformation was observed on the 10 mm and 15 mm crack ruler. The presence of crack reduced the elastic modulus of the ruler by 14% and the bending stiffness by 26.5%. The structural load-bearing capacity depends on the presence of cracks. Anticipating the extent of reduction in elastic modulus and bending stiffness aids designers in minimizing the need for repeated design revisions. This investigation supports both structural designers in designing structures such as airplanes and bridges, as well as repair technologists in upgrading existing structures.