Multi-directional hydraulic loading for high-precision calibration of additively manufactured aluminum alloy thin-walled tube

Metal additive manufacturing, due to its unique process characteristics, tends to produce deformation defects in thin-walled tubular components. This study proposes a multi-directional composite loading hydraulic calibration method to improve the geometric accuracy and mechanical properties of additively manufactured tubes. Using AlSi10Mg tubes fabricated by Selective Laser Melting (SLM) as the research subject, theoretical models describing dent flattening and axial compression instability were established based on the energy method and Cao-Boyce criterion. The influence of tube geometric parameters and material properties on calibration pressure was analyzed. Results indicate that the material's strain hardening exponent and strength coefficient significantly affect the critical flattening pressure and critical instability pressure. Through finite element analysis and experimental validation, the influence mechanisms of process parameters, including dent flattening pressure, corner forming pressure, and axial compression pressure, on calibration effectiveness were investigated. Under optimal process parameters (dent flattening pressure of 14 MPa, corner forming pressure of 130 MPa, axial compression pressure of 7 MPa, and axial boundary displacement of 20 mm), the method effectively eliminated the initial 1.82 mm dent in the straight edge region and controlled the inner and outer radius deviations of corners within 1.85 % and 0.83 %, respectively, achieving a maximum wall thickness increase rate of 20.53 %. Furthermore, the multi-directional composite loading hydraulic calibration induced a triaxial compressive stress state, which favorably enhanced microstructural homogeneity and mechanical properties. This research provides theoretical guidance and engineering reference for precise calibration of additively manufactured tubular components.