Effect of Internal Support on the Tensile Properties and Fracture Mode of 304 Stainless Steel Thin-Walled Tubes

Steel–tube composite structures contain multiple tubular components under tension. The enhancement of the mechanical properties of tubes under ultimate operating conditions is crucial for improving structural safety. In this study, 110 pieces of 304 stainless steel thin-walled tubes (SSTWTs) under five internal support conditions are investigated. The ultimate tensile strength, ultimate extension, and fracture energy of different groups of specimens are measured to understand the variation mechanism of fracture modes. The elastic modulus of tube filler is treated as a variable to establish a uniaxial tensile fracture matrix of 304 SSTWTs with different tube fillers and loading rates. The results demonstrate that flexible tube fillers can effectively limit the lateral necking of 304 SSTWTs. Under the middle fracture mode, the maximum increments in the ultimate strength, extension, and fracture energy of tubes are 10.81%, 24.56%, and 35.94%, respectively. Furthermore, as the support rigidity increases, the ultimate strength exhibits an overall increasing trend, while the extension and fracture energy initially increase and then decrease. Overall, this study provides a novel route for enhancing the performance of steel–tube composite structures under ultimate loading conditions, which is of great significance for improving the safety of the structural design and reducing the engineering construction cost.