Based on the structure and dynamic characteristics of aero-engine's case

an evaluation method for the whole engine case's non-deformability under safety design regulations was established. In order to evaluate the non-deformability from three aspects: structure characteristics

deformation characteristics under steady load

and deformation characteristics under impact load

three parameters including structure normalized equivalent stiffness

clearance matching coefficient

and impact amplification coefficient were raised respectively. Then a non-deformability assessment on typical high bypass ratio turbofan engine was conducted. The result shows that using the ratio of equivalent stiffness of each cross section to maximal equivalent stiffness as the structure normalized equivalent stiffness

using the ratio of minimal clearance to maximal clearance of each cross section under steady loads as the clearance matching coefficient

and using the ratio of peak force of impact load to bearing's or mount's reaction force as the impact enlargement coefficient

all the three parameters can reveal the dangerous position of the whole engine's case and the response characteristics under ultimate load. This result can provide a reference for structural design and optimization of other aero-engine's cases.