A General Workflow for Static Failure Criteria and Allowable Defect Size Calculation in Presence of Defects due to Manufacturing Process and Abusive Loads

Manufacturing processes such as casting, welding and additive manufacturing (AM) are prone to internal porosity and high surface roughness on the manufactured parts. These defects are inherent in the process and cannot be completely eliminated. Handling, transportation and maintenance of manufactured parts can also lead to defects such as scratches and dents due to abusive loads. The defects can be characterized in a number of ways, assuming they resemble a U-notch or V-notch, elliptical pores, or a continuous distribution of consecutive defects in combination with surface roughness. The designer utilizes existing analytical and empirical equations to predict stress concentration due to presence of various types of defects and compute factor of safety to ensure structural integrity of design subjected to various load cases. The applicability of existing analytical and empirical equations is studied, and modifications are suggested to improve the predictions. The limits of analytical equation to predict stress concentration due to presence of surface roughness is studied. A relation is established between surface roughness amplitude, frequency and the error between analytical equation and finite element analysis. This method quantifies shallowness of surface profile for prediction using analytical equations. A workflow of developed methodology is recommended to estimate allowable defect for different type, location, size, and shape of the defects.