ABSTRACT
Considering that it satisfies high strength and stiffness at a low weight, the grid structure is the ideal option for meeting the requirements for developing the wall panel structure for the satellite. The most attractive grid structures for the satellite wall panel industry are isogrid and honeycomb structures. The first part of this work involves studying the mechanical and dynamic performance of five designs for the satellite wall panel made of 7075-T0 Al-alloy. These designs include two isogrid structures with different rib widths, two honeycomb structures with different cell wall thicknesses, and a solid structure for comparison. The performance of these designs was evaluated through compression, bending, and vibration testing using both finite element analysis (FEA) with the Ansys workbench and experimental testing. The FEA results are consistent with the experimental ones. The results show that the isogrid structure with a lower rib thickness of 2 mm is the best candidate for manufacturing the satellite wall panel, as this design reveals the best mechanical and dynamic performance. The second part of this work involves studying the influence of the length of the sides of the best isogrid structure in the range of 12 mm-24 mm on its mechanical and dynamic performance to achieve the lowest possible mass while maintaining the structure's integrity. Then, a modified design of skinned wall panels was introduced and dynamically tested using FEA. Finally, a CAD model of a hexagonal satellite prototype using the best-attained design of the wall panel, i.e., the isogrid structure with a 2 mm rib width and 24 mm-long sides, was built and dynamically tested to ensure its safe design against vibration. Then, the satellite prototype was manufactured, assembled, and successfully assessed.
ABSTRACT
This work involves studying the effects of applying various designed hot-rolling strategies, using the uniaxial hot compression regimes of the Gleeble 3500 thermo-mechanical simulator on the microstructure, flow behavior, and productivity of Ti-6Al-4V alloy. These strategies were then practically implemented using a rolling mill to produce finished sheets with a thickness of 3 mm. The tensile properties of these finished Ti-6Al-4V sheets were examined, aiming at attaining the optimum rolling strategy conditions that result in upgrading the mechanical performance of the alloy. The undertaken hot-rolling strategies can be divided into two main groups; both comprise applying a total amount of deformation of 75% at a constant strain rate of 0.1 s-1. The first group, isothermal hot rolling regime (IR), includes three strategies and involves applying the total amount of deformation at constant temperatures, i.e., 900, 800, and 750 °C. The second group, non-isothermal hot rolling regime (NIR), includes three strategies and involves partitioning the total amount of deformation into multi-step deformation at variable temperatures in a range of 900-750 °C. The dynamic flow softening is dominant in all IR strategies after the flow stress attains the peak at a low strain value. Then, dynamic flow softening occurs due to the dynamic recrystallization and α phase spheroidization, while a combination of flow softening and hardening takes place on the different passes of the NIR strategies. The designed hot-rolling strategies result in finished sheets with a fine multimodal microstructure that fructifies different mechanical properties that can be employed for different industrial purposes.
