Thin-walled arc plate parts are widely used in aerospace critical equipment. However

such parts show inconsistent local stiffness at different locations under clamping

and their stiffness varies during the machining process

which brings difficulties in stable manufacturing. To address the problem

the discrete finite element model of a bilateral clamped thin-walled arc plate was established

and its position-associated stiffness distribution was obtained by Ansys Workbench. Subsequently

a discrete mirror milling simulation was carried out based on the “Element birth and death” method to investigate the its stiffness evolution under material removal. It turns out that under bilateral clamping

the stiffness of thin-walled arc plate exhibits a spatial “saddle-like” distribution with a gradient of change up to 54.38%

and the highest stiffness occurring in the position adjacent to the clamping area

while there is also an stiffness reinforcing zone in the center. During a single machining process

the local stiffness change of the workpiece shows non-monotonous positional correlation characteristics

and the central stiffness reinforcing zone still exists. With the deepening of the machining stage

the difference in stiffness between different positions further increases

with the maximum stiffness decreasing by about 69.97%

and the range of deformation reaches 0.2619 mm

which is a non-negligible influence on the machining accuracy.