What is the source for this theoretical calculation?
Why do you think it is accurate?
What simplifying assumptions did it make?
How did you model the multi-leaf spring in ANSYS?
Is each leaf free to slide on the adjacent leaf or are the leaves bonded together?
Are the leaves modeled with shell elements or solid elements?
Are the elements linear or quadratic?
If the leaves are modeled with solid elements, how many elements are across the thickness?
Please insert some images into your reply.