Failure analysis and optimal redesign study of the connecting rod prototype to be used in the multi-axle steering linkage of an 8x8 Aircraft Rescue and Fire Fighting (ARFF) vehicle is reported. At the prototyping stage, the field tests showed that the connecting rod experiences a plastic deformation during a zero-speed steering manoeuvre. In order to predict the possible causes of the failure, Finite Element (FE) analyses were applied to the complete steering linkage which contains the failed rod design. Primary FE analyses showed that there are critical stress concentration regions on the rod. It was also seen that the maximum stress values at these regions are influenced by the tyre steering angle and the slope of the road surface. Subsequently, critical structural parameters having an influence on the mechanical behaviour of the part were chosen, and a parametric base model was built. Then, using DOE-RSM (Design of Experiments – Response Surface Methodology) based optimisation study, optimal values were selected within the applicable variation range. Nonetheless, by considering the form of the structure together with the loading type, it was decided that the elastic stability should also be taken into account. Although a sufficient improvement was obtained against the overload failure, the elastic stability limit remained exceeded according to the American Institute of Steel Structures (AISC) criteria. Thus, the eccentricity of the connecting rod was also decreased by employing a particular kinematic arrangement in order not to disturb the Ackermann’s rule-based synchronisation ratio of the linkage. Compared to the failed design, it was seen that von-Mises stress can be reduced by up to 66%. The results of this study showed that, factors such as wheel steering angle and road inclination-related axle load variation greatly influence the structural safety of the steering linkage. Field tests also indicated that, suggested design improvements such as increase in thickness and eccentricity reduction meet the strength requirements of the system.

报道了用于8x8飞机救援和消防（ARFF）车辆多轴转向联动装置的连杆原型的故障分析和最佳重新设计研究。在原型设计阶段，现场测试表明，连杆在零速转向操作过程中发生塑性变形。为了预测可能的故障原因，将有限元（FE）分析应用于包含故障杆设计的完整转向连杆。初步的有限元分析表明，棒上存在临界应力集中区域。还可以看到，这些区域的最大应力值受轮胎转向角和路面坡度的影响。后来，选择影响零件机械性能的关键结构参数，并建立了参数基础模型。然后，使用基于DOE-RSM（实验设计–响应面方法学）的优化研究，在适用的变化范围内选择最佳值。尽管如此，通过考虑结构的形式以及载荷类型，决定还应考虑弹性稳定性。尽管针对过载故障已获得足够的改进，但根据美国钢结构学会（AISC）的标准，仍超过了弹性稳定性极限。从而，为了不影响连杆的基于阿克曼规则的同步比，采用特殊的运动学布置也降低了连杆的偏心率。与失败的设计相比，可以看到von-Mises应力可以减少多达66％。研究结果表明，车轮转向角和与道路坡度有关的轴负载变化等因素极大地影响了转向连杆的结构安全性。现场测试还表明，建议的设计改进（例如增加厚度和减小偏心率）可以满足系统的强度要求。诸如车轮转向角和与道路倾斜有关的轴负载变化等因素极大地影响了转向连杆的结构安全性。现场测试还表明，建议的设计改进（例如增加厚度和减小偏心率）可以满足系统的强度要求。诸如车轮转向角和与道路倾斜有关的轴负载变化等因素极大地影响了转向连杆的结构安全性。现场测试还表明，建议的设计改进（例如增加厚度和减小偏心率）可以满足系统的强度要求。