In the marine gear system, the vibration of gears is transmitted to the ship foundation through shafts, bearings, housing, and isolators, and then the underwater noise is generated. Analyzing the vibration transfer properties and identifying the critical path can provide guidance to the low-noise design of the gear system. In this paper, a coupled gear-housing-foundation dynamic model is proposed for a flexible supported gear system, in which the flexibility of each subsystem and the coupling relationship between them are taken into account. The transferring process of gear vibration is divided into different layers between gears, shafts, bearings, housing, isolators, and ship foundation. Based on the vibration power flow (VPF) theory, detailed layering vibration transfer path analyses of the gear isolation coupled system are carried out for both location path and direction path, and the main paths are identified in a broad speed range. The results indicate that though the gear vibration transferred to the foundation attenuate layer by layer, there may be reverse VPF in some special location path and direction path under resonance conditions.

The marine gearbox is usually installed on a vibration isolation system in order to reduce oscillation transmitted to the ship foundation. However, researches on vibration transmission in the gear‐housing system and isolation system are currently independent. With the increasing requirement of lower vibration, a coupled model needs to be built to control the vibration propagation from a view of the whole system. Considering the mesh transmission error excitation of a gear pair, a flexible gear‐housing‐foundation coupled impedance model is constructed in this paper, and the vibratory power flow of the whole system is calculated. Power transmissions between three different gearbox installation configurations, that is, rigid installation, single‐stage isolation, and double‐stage isolation, are compared. Taking the single‐stage isolation configuration as an example, parameter influences on the vibration of the foundation are studied. Results show that double‐stage isolation can achieve lower vibration than single‐stage isolation; decrease in bearing stiffness or Young’s modulus of isolator will yield better vibration isolation performance; housing damping and isolator damping are beneficial to vibration reduction.

Due to the excitation generated by the periodically alternate pumping of dual-hydraulic cylinders, vibration of concrete pump trucks (CPT) occurs. Excessive boom vibration will seriously affect the service life and operation safety of CPT. At the same time, the long boom structure of a CPT makes it very sensitive to the posture and pumping conditions, which directly affect the vibration characteristics of CPT in different postures and different working conditions. This paper establishes a finite element model of a type of CPT. Through force analysis of concrete in the straight pipe and elbow pipe during the pumping and reversing stages, an excitation model of the conveying pipe is established. Based on the secondary development of HyperWorks, a finite element model of CPT with multiple postures is built, and the dynamic response under multiple conditions is analyzed. Finally, the accuracy of the finite element model of CPT and the excitation model of the conveying pipe is verified by experiment.

This paper presents a novel general system-structure coupling dynamic analysis procedure to comprehensively analyze the dynamic performance of planetary gears. The novel coupling dynamic analysis takes dynamic loads of gears as excitations for structure dynamic analysis. Considering the time-varying mesh stiffness of gears, torsional stiffness of carrier and support stiffness of bearings, the system dynamic model of planetary gears is built by using lumped parameter method. Vibration modes and natural frequencies of planetary gears are investigated through modal analysis. Furthermore, system dynamic response is analyzed under various working conditions. Equations of structure dynamic analysis based on finite element method (FEM) are developed, and their solving method is put forward. Dynamic loads obtained from system dynamic analysis are forced on the ring gear to analyze its structure dynamic response. In every analysis step, if dynamic performance criteria are not satisfied, the planetary gears model should be redesigned according to dynamic analysis results.

This article studies the calculation method for the tooth root bending stress of a high-tooth gear pair with a high contact ratio. The boundary point of the double-tooth meshing zone of the high-tooth gear pair is used as the loading point for the load, and the calculation formula for the bending stress at the dangerous section of the tooth root is obtained. By using ANSYS finite element simulation, the effect of the addendum coefficient, pressure angle, and other gear parameters on the bending stress of the tooth root is studied. The analysis shows that increasing the pressure angle will reduce the bending strength of the tooth root. Increasing the coefficient of a tooth’s top height will lead to an increase in the bending strength of the tooth root. Comparing the finite element analysis (FEA) results with the theoretical calculation results, the analysis shows that under low loads, the maximum error of the theoretical calculation values of the driving toothed gear and driven gear shall not exceed $13.53\%$ and $15.42\%$, respectively. Under high loads, the maximum theoretical errors of the driving toothed gear and driven gear shall not exceed $8.78\%$ and $10.91\%$, respectively. This verifies the correctness of the calculation method, which is of great significance for improving the load-bearing capacity of high-tooth gears and for guiding tooth shape design.

Gear transmission systems are widely used in various fields. The occurrence of gear cracks, tooth pitting, and other faults will lead to the dynamic characteristics deterioration of the transmission system. In order to calculate the meshing stiffness of faulty gear pairs more effectively and precisely, this article improves the loaded tooth contact analysis (LTCA) method by analyzing the influence of different fault types on gear deformation, including bending-shearing deformation and contact deformation, which combines the accuracy of the finite element method (FEM) and the rapidity of the analytical method (AM). The improved LTCA method can model the fault areas accurately and optimize the deformation coordination equation under the actual meshing situation of the faulty gear tooth, making it suitable for calculating the meshing stiffness of faulty gears. Based on the calculation results of the finite element method, the accuracy of the improved meshing stiffness calculation method has been verified, and the sensitivity of different fault type parameters on meshing stiffness has been studied.