Вплив зазору на залишкові напруження та якість вальцьованих з'єднань труба-трубна дошка

The quality of the tube-to-tubesheet joint is a critical factor determining the reliability and durability of heat exchangers and various types of industrial equipment operating under demanding conditions. This article examines the influence of the clearance between the tube and the tubesheet hole on the magnitude of residual stresses in the joint following the tube rolling process. The experimental component of the study involved precise measurements of actual clearances using specialized tools, the calculation of residual stresses through the mechanical stress relief method, and a comprehensive statistical analysis of the collected data to ensure accuracy and consistency. The findings revealed that the actual clearance typically exceeds the nominal value specified in design standards, and an increase in this clearance directly correlates with a rise in residual stresses within the joint. Notably, the highest stress levels were observed at clearances of 0.40 mm and greater, which may lead to localized plastic deformation, compromising the structural integrity and reducing the fatigue strength of the joint over time. Based on the analysis, the optimal clearance range was determined to be between 0.10 mm and 0.30 mm, as it strikes a balance between ensuring joint reliability and maintaining acceptable stress levels, thus minimizing the risk of premature failure. To validate the reliability of the experimental results, advanced statistical methods were employed, including the calculation of standard deviation to assess data variability and the application of Student's t-test to evaluate the significance of the observed trends. These calculations confirmed a statistically significant relationship between clearance size and residual stress levels, with particularly pronounced effects observed in joints involving small-diameter tubes, where tolerances are more critical. The outcomes of this research have practical implications for the design and manufacturing of shell-and-tube heat exchangers, offering a pathway to optimize joint parameters, enhance operational performance, and extend service life. Additionally, the study provides detailed practical recommendations for quality control, including precise methods for measuring clearances with high accuracy and evaluating residual stresses during production and maintenance processes