## 5 Discussion and Vibration of the Pump Housing
Around the maximum and minimum points, the pressure difference across the valves is greatest, potentially leading to increased leakage and further worsening of pressure fluctuations. The compressibility of the hydraulic fluid plays a key role. Highly compressible fluids (such as air-oil mixtures) will exhibit more pronounced pressure fluctuations compared to less compressible fluids. The viscosity of the fluid affects the resistance to flow and can affect the damping of pressure waves within the system. Instrumental factors originate from the dynamics of pressure transducers, which may have resonant frequencies. If the frequency of pressure fluctuations within the pump coincides with the resonant frequency of the transducer, the transducer may amplify the measured pressure fluctuations. Bandwidth limitations have limited bandwidth. High-frequency pressure fluctuations may not be accurately captured or may be attenuated by the response characteristics of the transducer. If the sampling rate of the data acquisition system is insufficient, high-frequency pressure fluctuations may be suppressed or missed completely, leading to inaccurate measurements. Electrical noise within the data acquisition system can introduce spurious signals that contaminate pressure measurements. By carefully considering the internal and instrumental factors, engineers can effectively identify and mitigate pronounced pressure fluctuations in axial piston pumps, resulting in improved system performance, reduced noise levels, and extended service life. In an axial piston pump, variations in cylinder and pressure chamber pressures during the rotation cycle of the drive shaft directly affect the harmonic content of the pump housing vibrations. As the pistons move in the cylinders, the volume within each cylinder changes. This results in significant pressure variations during the compression and expansion strokes. These pressure fluctuations exert dynamic forces on the cylinder block and pump housing, acting as excitation forces that cause vibrations. The flow from the pump is not constant, but pulsates due to the cyclic motion of multiple pistons. This results in pressure fluctuations in the pressure chamber. These pressure variations transmit forces to the pump housing through the fluid and internal pump components. The primary frequency component in the pump housing vibrations typically corresponds to the rotation speed of the drive shaft. Pressure variations within each cylinder, which are often periodic, contribute to fundamental frequency harmonics. The specific harmonics present depend on factors such as the number of pistons, their arrangement, and the shape of the pressure waveforms in each cylinder. Pressure pulsations in the supply line can also cause fundamental frequency harmonics, especially if the pulsations are significant. The pump housing itself has natural vibration frequencies. If the frequencies of the pressure-induced excitation forces coincide with these natural frequencies, resonance can occur, leading to amplified vibrations. To identify the dominant frequencies and harmonics in the frequency domain analysis of the vibration and pressure signals, fast Fourier transform (FFT) was applied. Insights for optimizing pump performance and durability can be gained by continuously monitoring pump housing vibrations. Changes in vibration patterns can indicate developmental defects such as bearing wear, cavitation, or valve problems. Optimizing the pump's structural design should avoid resonances within the typical operating frequency range. Effective vibration isolation techniques are required to isolate the pump from the surrounding system. Pressure pulsation can be reduced by optimizing piston geometry and stroke length to minimize pressure fluctuations. Improving valve design and flow characteristics will reduce pressure transients. Using vibration data, condition-basedmaintenance strategies can be implemented, enabling proactive repairs and replacements before catastrophic failures occur.