Compliant variable negative to zero to positive stiffness twisting elements

Ali Amoozandeh Nobaveh*, Just L. Herder, Giuseppe Radaelli

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Compliant mechanisms have the potential to be utilized in numerous applications where the use of conventional mechanisms is unfeasible. These mechanisms have inherent stiffness in their range of motion as they gain their mobility from elastic deformations of elements. In most systems, however, complete control over the elasticity is desired. Therefore, compliant mechanisms with variable, including zero, stiffness can have a great advantage. We present a novel concept based on the prestressing of open thin-walled multi-symmetric beams. It is demonstrated that by changing the prestress on the center-axis of these beams, a range of variable torsional stiffness can be achieved. For beams with a large warping constant, the stiffness changes from positive to zero and negative as the prestress increases, while for beams with a near-zero warping constant, the range of neutrally stable twisting motion increases. A planar equivalent is shown in this work to elucidate the notion, and numerical and experimental analyses are performed to validate the prestress-related behavior.

Original languageEnglish
Article number105607
Number of pages12
JournalMechanism and Machine Theory
Publication statusPublished - 2024


This work was supported by the Dutch Research Council (NWO) [ P16-05 Shell-Skeletons ]. The authors would also like to thank Patrick van Holst for his assistance with the experiments.


  • Bistable mechanisms
  • Compliant mechanisms
  • Negative stiffness
  • Twisting beams
  • Variable stiffness
  • Zero stiffness


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