Professor of Solid and Structural Mechanics
An Elastica Arm Scale
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The concept of ‘deformable arm scale’ (completely different from a traditional rigid
arm balance) is theoretically introduced and experimentally validated. The idea is
not intuitive, but is the result of nonlinear equilibrium kinematics of rods inducing
configurational forces, so that deflection of the arms becomes necessary for the equilibrium, which would be impossible for a rigid system. In particular, the rigid arms of
usual scales are replaced by a flexible elastic lamina, free of sliding in a frictionless and
inclined sliding sleeve, which can reach a unique equilibrium configuration when two
vertical dead loads are applied. Prototypes realized to demonstrate the feasibility of
the system show a high accuracy in the measure of load within a certain range of use.
It is finally shown that the presented results are strongly related to snaking of confined
beams, with implications on locomotion of serpents, plumbing, and smart oil drilling.