Alireza Ahmadi and Neda Maghsoodi
J. Comput. Nonlinear Dynam. Feb 2026, 21(2): 021004
https://doi.org/10.1115/1.4070198

​This paper investigates the effect of intrinsic (built-in) bending curvature on the dynamics, energetics, and stability of photomechanical fibers, which deform in response to illumination. We develop a multiphysics dynamic model based on the nonlinear Kirchhoff’s rod theory to capture the coupled photomechanical response of the curved fibers. Using two canonical examples—the bending of a clamped-free strip and the periodic flapping of a clamped-clamped strip—we demonstrate how intrinsic curvature fundamentally affects the spatiotemporal deformation of the strips subject to steady illumination. Our findings reveal that the dynamic behavior of intrinsically curved photomechanical fibers differs both qualitatively and quantitatively from their intrinsically flat counterparts, underscoring the importance of initial geometry in the design and control of photomechanical systems. In particular, in the case of the clamped- clamped strips, although both the pre-stressed strip and stress-free curved strip exhibit self-sustained periodic flapping motions when subject to steady illumination, the stress-free curved strip requires higher input energy (i.e., greater light intensity), oscillates at a lower frequency, and exhibits a largely asymmetric deformation pathway per cycle. Moreover, the range of illumination angles that can trigger self-sustained oscillations in stress-free curved strips is narrower compared to the pre-stressed case.

Bassam J. Alshaer and Hamid M. Lankarani
J. Comput. Nonlinear Dynam. Dec 2025, 20(12): 121008
https://doi.org/10.1115/1.4069962

This research introduces a new analytical framework for modeling finite-length lubricated journal bearings in multibody systems, striking a balance between the simplicity of traditional infinite-length models and the precision of detailed finite-length solutions. Although infinite-length approximations are computationally and implementationally efficient, they ignore axial leakage and 3D pressure effects, leading to inaccuracies in real-world scenarios. On the other hand, existing exact finite-length models provide high accuracy but are mathematically complex, apply domain transformations and implementation inefficient, and hindering widespread use. The proposed method employs a separation of variables approach to the Reynolds equation, deriving closed-form expressions for hydrodynamic pressure and forces that incorporate side leakage while remaining implementing efficient for system-level simulations. Implemented within a dynamic multibody framework using an augmented Lagrangian formulation, the model allows physical lubricated bearings to replace idealized revolute joints. Validation against numerical benchmarks confirms the accuracy of the analytical solutions. Case studies - including a loaded journal-bearing system and a high-speed crank-slider mechanism—demonstrate the model's ability to capture finite-length effects, such as elevated eccentricity ratios and dynamic force overshoots caused by axial leakage, without sacrificing simplicity. The findings underscore the substantial influence of finite-length corrections on dynamic behavior, including journal orbit stability, force distribution, and torque variations. This study provides a scientifically rigorous yet practical approach for integrating realistic lubrication effects into multibody dynamics, enhancing simulation accuracy for engineering systems with lubricated clearance joints.

He Ma, Zijun Yang, Suo Wang, Haitao Xu, and Shengxi Zhou
J. Comput. Nonlinear Dynam. Jan 2026, 21(1): 011002
https://doi.org/10.1115/1.4069824

​Bistable vibration energy harvesters have been comprehensively and thoroughly studied for their outstanding energy harvesting capabilities. The lever mechanism offers a straightforward and effective solution for realizing bistable systems. Neglecting dynamical characterization of such harvesters would lead to unanticipated nonlinear behaviors that impair performance. Thus, this paper proposes a nonlinear lever-type vibration energy harvester with a series-connected RLC circuit. First, a bistable energy harvester is designed by introducing negative stiffness. The theoretical model has been established and is validated by numerical and experimental results. Second, the relationship between the equivalent stiffness and the magnet space is studied, based on which dynamic responses under different magnet spaces are then analyzed by the bifurcation diagram. According to the Poincaré map, chaos can be perceived. The cause of the chaos is figured out as a period-doubling bifurcation through the phase trajectory. Third, potential energy with various lever pivot positions is compared, indicating that a higher potential energy well leads to interwell oscillations, and chaos is highly related to the pivot position. Finally, the power generated is discussed by altering the RLC circuit's resonant frequency and resistance value. The average power is capable of achieving 3.22 mW. Overall, this paper establishes the theoretical foundation for investigating the dynamic characteristics of lever-based bistable energy harvesters, as well as the influence of RLC circuit loading on power output performance.