Guan Zhou

Suspension mechanical performance and vehicle ride comfort applying a novel jounce bumper based on negative Poisson's ratio structure

Abstract Comparing with traditional honeycomb structures, Negative Poissons Ratio (NPR) structures had better mechanical performances in some certain respects, especially the shear modulus and fracture toughness. However, few publications focused on the cylinder-shape NPR structure, which influence the diversity and possibility of NPR structure applications. In this paper, a cylindrical NPR structure was introduced and applied as a suspension jounce bumper in order to solve the issue that the ideal uniaxial compression load-displacement curve sometimes cannot be realized by traditional Polyurethane (PU) jounce bumper. The load-displacement curve of NPR jounce bumper was proved to be smoother and more ideal than that of traditional jounce bumper. Nevertheless, the influences of NPR jounce bumper on the suspension mechanical performance and vehicle ride comfort were not comprehended yet. In this study, the traditional and NPR jounce bumpers were both assembled into virtual prototypes of Macpherson, double wishbone and multi-link suspensions to conduct single wheel travel virtual tests. The results indicated that NPR jounce bumper can achieve more ideal wheel force vs. jounce height curve without adjusting free travel, which is beneficial to spare precise suspension space. Furthermore, a jounce bumper evaluation method using pulse ride comfort was proposed in this paper. The virtual ride comfort tests of travelling through bump and pothole were conducted using established vehicle virtual prototype. The maximum vertical accelerations and weighted root mean square (RMS) of acceleration of vehicle centroid at most speeds were reduced applying NPR jounce bumper. Thus, the NPR jounce bumper can apparently improve vehicle ride comfort.

Multi-objective reliability design optimization of a novel side door negative Poisson’s ratio impact beam:

By possessing a good capacity for energy absorption and a lightweight structure, the negative Poisson’s ratio (NPR) structure has very fine prospects for application in vehicle engineering. By combining the traditional side door impact beam and a NPR structure, a novel side door NPR impact beam is first proposed in this work to improve the side impact crashworthiness in automobiles. The performance of the side door NPR impact beam is first studied in detail by comparison with a traditional side door impact beam and aluminum-foam-filled impact beam. To make further improvement on the performance of the side door NPR impact beam, the multi-objective design optimization while considering reliability is also investigated in this work. The parametric model of the NPR structure is established to improve modeling efficiency when the shape and topology are changed. A Latin hypercube sampling technique, orthogonal design, and a response surface model are then combined to construct the surrogate models. A radial-based importance sampling technique (RBIS) and multi-objective particle swarm optimization algorithm (MOPSO) are applied in the inner and outer loop respectively to find the optimal multi-objective reliability solutions. The results indicate that the side impact crashworthiness is improved remarkably by the side door NPR impact beam and the structure is further improved by the multi-objective reliability optimization. The studies in this work also serve as a good example for other improvements in automobile performance.

Reliability optimization of a novel negative Poisson’s ratio forepart for pedestrian protection

The bumper system always directly causes the injury of the pedestrian leg in the car–pedestrian accidents. Therefore, it is of practical significance to optimize the bumper structure to enhance the protective effect of the pedestrian leg. Based on the original bumper system, this work proposes a novel negative Poisson’s ratio energy-absorbing forepart with inner hexagonal cellular structure, which is designed at the lower leg impact zone between the bumper beam and the cover. The parametric model of the negative Poisson’s ratio forepart, the lower legform impactor model, and the car–pedestrian collision model are firstly established. Then, through integrating the response surface method, second-order reliability method, and archive-based micro genetic algorithm, a reliability optimization design is further conducted for the negative Poisson’s ratio forepart based on the deterministic optimization results. Simulation results show that the optimized negative Poisson’s ratio forepart not only can significantly enhance the reliability and robustness, but also improve the protective effect of the pedestrian leg.