Topology optimization of turbine disk considering maximum stress prediction and constraints

For the stress-constrained topology optimization of a turbine disk under centrifugal loads, the jagged boundaries of the mesh and the gray densities on the solid/void interfaces could make the calculated stress field inconsistent with the actual value. It may result in overestimating the maximum stress and thus affect the effectiveness of stress constraints. This paper proposes a new method for predicting the maximum stress to overcome the difficulty. In the process, a predicted density is newly defined to obtain stable boundaries with thin layers of gray elements, a transition factor is innovatively proposed to evaluate the effects of intermediate-density elements, two different stiffness penalty schemes are flexibly used to calculate the elastic modulus of elements, and a linear stress penalty is further adopted to relax the stress field of the structure. The proposed approach for predicting the maximum stress value is verified by the analysis of a structure with smooth boundaries and the topology optimization of a turbine disk. An updating scheme of the stress constraint in the topology optimization is also developed using the predicted maximum stress. Some key ingredients affecting the optimization results are discussed in detail. The results prove the effectiveness and efficacy of the proposed maximum stress prediction and developed stress constraint methods.     

Research progress of space non-pyrotechnic low-shock connection and separation technology (SNLT): A review

Space missions have become diversified in recent years, where connection and separation devices play a crucial role as key components of various spacecraft. Traditional pyrotechnic devices have the advantages of large carrying capacity, rapid motion and functional reliability. However, their shortcomings such as great release shock, poor safety, unrepeatability and other prominent defects make them unsuitable for new generation spacecraft such as microsatellites to separate at low shock or lock repeatedly, etc. Therefore, it is necessary to develop space non-pyrotechnic low-shock connection and separation devices (SNLD) which are required for advanced aerospace missions. In this paper, the progress of the research on space non-pyrotechnic low-shock connection and separation technology (SNLT) is summarized and reviewed. Proceed from the principle of reducing shock for non-pyrotechnic devices, present studies are classified from the perspective of actuating technology and systematic designing methods. For non-pyrotechnic actuating techniques, according to different driving sources, the separation devices are classified into several main categories: electric, magnetic, gas and thermal actuating devices. The actuation principle and application prospect of separation techniques are introduced and the working process, dimension and mechanical properties of typical devices are compared and evaluated. For the systematic designing method, the common mechanism types of SNLDs are summarized according to the designing concept of reducing shock. Then connection configurations are classified according to the structural forms of connection devices, of which the principles, bearing capacities and general applications are discussed. This paper systematically summarizes the key problems, puts forward the future development trend of SNLT, and points out the breakthrough direction for related scholars.