# Simulative and Experimental Investigation of Vibration Transfer Path at Gearboxes
## 1 Introduction  
Gearboxes are widely used in vehicles, ships, wind turbines, etc. To achieve high safety standards and avoid additional costs resulting from any damages, condition monitoring is one way to achieve maximum reliability and availability. By measuring the vibrations under operation and analyzing the amplitude of the measured signal at specific frequencies, it is possible to detect damages and relate them to specific components. In gearboxes, each rotating component can generate vibrations with different frequencies, so it is important to analyze the vibration transmission through the different components in gearboxes, such as the gears, shafts, bearings, and housing. [PERSON] [1] analyzes the vibration transmission of an entire gearbox using the vibration power flow. He indicates that the bearings and housing are critical for the vibration transmission within the gearbox system. [PERSON] [2] uses lumped parameter modeling to investigate the vibration transmission of a gearbox and indicates that the maximum attenuation occurs at the transmission from the inner race to the outer race, while the minimum is between the outer race and the housing. [PERSON] [3] analyzes the vibration of a gearbox by using both lumped parameter modeling and finite element analysis and shows that the lumped parameter model is suitable for parametric studies on the dynamic response. [PERSON] [4] defines a periodic structural drive shaft that can reduce gear mesh vibration transmission. A periodicstructural shaft means that a few sections of the drive shaft are modeled periodically after each other. [PERSON] (1992) investigates vibration transmission to minimize vibration levels by a modification of the gear. He indicates that discontinuity in the gear body is helpful for structure-borne sound insulation. As the bearing is critical for vibration transmission, several sources ([PERSON] and [PERSON], 1996; [PERSON], 1997; [PERSON], 1998) investigate vibration transfer through bearings. [PERSON] (1992) uses the lumped parameter model to simulate the dynamic behavior of a generic single-shaft-bearing plate system and investigate the vibration transmission through the bearing. [PERSON] (1992) investigates the transfer function of the bearing based on theoretical calculations and experiments. The transfer function describes the ratio of the speed of the vibration between the bearing outer ring and the bearing inner ring. For the investigation of vibration transmission through the housing, the finite element analysis has typically been used because of the complex geometry of the housing. Several sources ([PERSON] and [PERSON], 1996; [PERSON], 1997; [PERSON], 1998) investigate the differences in vibration levels at different positions on the gearbox housing in order to find suitable positions for condition monitoring. [PERSON] (1992) evaluates the vibration level in the time domain at different positions of a gearbox based on an experiment and simulation. [PERSON] (1993) and [PERSON] (1994) also investigate the transfer path of a gearbox system by analyzing the vibration with the gear mesh frequency. The gear mesh frequency (GMF) represents the frequency of mating teeth during gear operation. The dynamic model of the gearbox without the housing is used to calculate the dynamic bearing forces caused by the gear mesh. These bearing forces are considered excitation forces for the housing, and the dynamic behavior of the housing is simulated using the finite element method (FEM). [PERSON] (1996) evaluates the vibration level caused by a bearing defect at different housing positions. Thus, there are multiple sources that investigate vibration transfer, the so-called transfer path analysis (TPA). An early source from [PERSON] (1997) investigates the transfer path from a ship engine with the connected machinery and the hull. [PERSON] (1998) also investigates a powertrain--in this case, a diesel combustion engine in a car.