Design of a device for stress corrosion testing in pressurized chambers

In the characterization of the mechanical behavior of metallic materials, the effects of the combined action of corrosive environmental factors, together with stress states induced by operating loads, are the subject of in-depth studies and undergoing continuous development. The idea behind the project was born thanks to the collaboration with the company Nuovo Pignone S.r.l. of Florence, a group headed by General Electric. The aim of the study is the development of a device that allows conducting stress corrosion susceptibility tests on metallic materials, to be carried out inside pressurized chambers of autoclaves according to the NACE- TM0177 standard. The test consists in maintaining a constant uniaxial tensile load on a specimen for 720 hours, in a corrosive environment with temperature values up to 200°C and pressure values up to 100 bar. The main requirement of the design study concerns the possibility of inserting as many specimens as possible in the autoclave, in order to distribute the high test costs over several tests. During the preliminary phase, the solutions currently available are analyzed and two concepts were subsequently developed, one of which was further optimized, particularly as regards overall dimensions, up to the construction of a functional prototype. Following the laboratory testing of the prototype, the application methods are developed, defining, in particular, a procedure to minimize the decay of the clamping force over time. The device guarantees an adequate degree of resistance to both mechanical and environmental stresses and has been patented for future applications in the industrial field.