Concepção, projeto e análise estrutural de um tubo de choque acadêmico

Abstract

The shock tube is an equipment used in laboratory studies on supersonic flows, providing data on the flight conditions in which the aerospace vehicles will find themselves. The Federal University of Rio Grande do Norte (UFRN) has stainless steel tubes – donated by the Institute of Advanced Studies (IEAv) – intended for the construction of the Institution's first shock tube. The objective of the research carried out was to make the construction of the equipment technically feasible. The correct sizing of the components is a fundamental part of the project, being essential to prevent accidents and control measurement errors during the tests, since it is a device subjected to high pressures. Structural modeling through software allows reducing material waste and operational risks during the construction of prototypes. Boundary conditions and applied loads must be rigorously selected, to provide a good level of confidence to the research results and, thus, constitute a guide for the execution of the academic project in a technical way. For this, the following were carried out and are presented here: calculations of the flow conditions; modeling and structural analysis of the high pressure (driver) and low pressure (driven) sections of the academic shock tube, considering the dimensions of the stainless-steel tubes available at UFRN; in addition to determining the efforts to which the tubes will be submitted when the equipment becomes operational. Analytical (Lamé Equations) and numerical (Ansys Mechanical) results of circumferential, radial and von Mises stresses were compared by means of their percentage variations. Autodesk Inventor was also used for simulations and comparisons with Ansys Mechanical results. Both the driver and the driven were analyzed considering their ends closed by means of flanges and thus treated as pressure vessels. Ansys Mechanical and Autodesk Inventor software were used in the analysis, with discretization of the models by mesh generation and application of the Finite Element Method. A pressure of 70 atm (7.09 MPa) was applied to the inner surface of the highpressure section during calculations and computer simulation, while other pressures generated in the flow were calculated and applied to the low pressure section. All pressures were also multiplied by four to assess the impact of this change in stresses. Based on the results obtained for von Mises stresses, circumferential stresses, and radial stresses, it was found that, considering the properties of stainless steel AISI 304 and steel SAE 4140, the available tubes will withstand the workloads within the operating range to which they will be subjected without implying any risk of damage, in view of the first stage of the UFRN academic shock tube construction project.