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Additional file 1. Maps of RFCA.

In order to reduce the weld size of weld joints designed based on equal load carrying capacity (ELCC) further, the shape of under-matching butt joints is designed with the parameter of plastic limit loads. The realization condition of ELCC is that the plastic limit loads of the weld equals to that of the base metal. Through analysing the tensile/bending load carrying capacity of weld zone, the weld shape was determined, and the method of tensile/bending ELCC design for butt joints is given. The ELCC joints are designed and their elastoplastic finite element analyses are carried out to verify their load carrying capacities. The tensile ELCC joint fractures at the base metal in the mode of overall yield fracture and its load carrying capacity reaches the tensile strength of the base metal. The load carrying capacity, deformability and stiffness of the bending ELCC joint are better than that of the base metal. The results indicate that the joints with acceptable size meet the requirements of ELCC, which is of great significance to the application of ELCC joints.

In order to ensure the surface form precision of a mirror whose caliber is 320 mm changes as small as possible before and after bonding, while static and dynamic stiffness of the mirror components meet the requirements, bonding technique of primary mirror in space camera was studied. Firstly, specific bonding parameters of six bonds and round bonds were achieved. Then, the finite element analysis for two bonding options was carried out to analyze static stiffness and optical properties. Finally, when the mirror's surface form precision was 0.030(=632.8), the surface form precision of the mirror was tested. Besides, vibration test of mirror components was conducted. Analysis and experiment results indicate that after using six bonds option to assemble the mirror components, its first order frequency is 144.194 Hz and static and dynamic stiffness meet the requirements. Compared to round bonds option, the surface form precision of the mirror improves 13.5%. This results mean that the six bonds option is better for bonding the mirror whose caliber is near 320 mm.