The fundamental structure of the space propellant tank is introduced. The design flow and the numerical simulation method of a typical metal diaphragm are proposed. Then, a range of 237mm diameter titanium diaphragms with different bottom fillet radiuses are designed. Based on the arc-length method, a series of finite element models of the reversal process of these titanium diaphragms are developed. With the aid of the models, this paper analyzes the effect of bottom fillet radius on pressures differential to roll the titanium diaphragms. The results show that the critical pressure increases with the decrease of the bottom fillet radius. A near linear increase is found, which indicated that the bottom fillet radius has a certain effect on the critical pressure. The maximum equivalent von mises stress increases with the decrease of the bottom fillet radius. The increase leads to the increase of the critical pressure. In addition, the deformation of the diaphragms becomes more and more instable with the decrease the bottom fillet radius.

No abstract

A range of titanium diaphragms for spacecraft propellant tanks are designed in detail, and two typical titanium diaphragms were manufactured and corresponding reversal tests were developed. A series of finite element models of the reversal process of these titanium diaphragms is developed based on the arc-length method and a finite element analysis software. With the aid of the models, this paper analyzes the characteristics of pressure drop during the whole reversal process and investigates the effects of the structural parameters on pressure differential to roll titanium diaphragm. The results show that simulated values of the critical pressure and the overturning pressure show good agreement with measured ones. In addition, the critical pressure increases with increasing thickness, decreasing bottom diameter and chamfering radius. The thickness and the bottom diameter are the main influence factors for the critical pressure. The overturning pressure increases with increasing thickness and arc radius. These effects of the bottom diameter, the chamfering radius, and arc radius become sharper with increasing thickness.

No abstract

A improved method is developed to model the effect of grain size on deformation behavior in polycrystalline pure copper. In this method, a grain size controlled polycrystalline geometry model based on the Voronoi tessellation is employed to generate virtual grain structures that are statistically equivalent to metallographic measurements in terms of grain size distributions, and a crystal plasticity constitutive model considering size effect is proposed on the basis of Hall-Petch type relationship. Then, a set of crystal plasticity finite element models are developed to simulate the tension flow stresses of polycrystalline pure copper with different mean grain size. The results show that the size constants τ0', k1, τs', k2 and ns in the crystal plasticity constitutive model are determined as 13.754, 65.584, 152.653, −4.820 and 0.418, respectively, and the simulated data of flow stresses show good agreement with experimental ones. In comparison with the classical method, the shear strain distributions and the differences of their ranges are remarkable, and more local shear strain concentrations can be observed in the transition zones between the larger grains and the smaller ones, when the improved method is applied.