This paper deals with light-emitting phenomena in hydraulic components, which are closely linked to cavitation.
Both the micro-diesel effect and the gas discharge have been optically investigated within plane models of a
valve and a pump section, respectively. The gas discharge is caused by an electrostatic charge of the oil or of the
component. One result of the investigations is an overview of the areas of occurrence and the minimum
necessary operating conditions of the phenomena. The form of appearance of both phenomena is also shown.
Furthermore, the impact of electrically insulating materials is presented. In addition some measurements of the
temperatures in close proximity to the phenomena are presented.

In this investigation, hydraulic fluids of varying base oil and additive composition were evaluated in a dynamometer fitted with a reservoir that incorporated an aerator at the inlet, and a mass flow meter at the outlet. The effects of aeration on piston pump efficiency and air borne noise generation were evaluated. Hydraulic oils that entrained a greater volume of air demonstrated lower volumetric efficiencies and higher sound levels. The fluids differed in volumetric efficiency by as much as 8% and perceived sound level by as much as 50%. Based upon 2,500+ hours of testing in a high-intensity loader application, the performance benefits of the low aeration fluid were persistent.

In common practice a hydraulic cylinder undergoes permanent acceleration and deceleration. In general this transient behaviour is neglected in the simulation of hydraulic seals, especially regarding the fluid film where stationary conditions are assumed. In order to gain a detailed understanding of the dynamic sealing process, a finite element based, elastohydrodynamic simulation model for hydraulic seals has been developed, including transient effects /1/. In this paper the influence of these transient effects on the behaviour of a hydraulic seal is investigated. The influence is studied under different system conditions in order to examine to which extend the consideration of transient effects in a simulation of hydraulic seals is inevitable.

The presented work investigates the temperature dependence of the Navier slip boundary condition and the related reduction of load capacity of a bearing. In part (i), the Navier slip boundary condition is discussed and a modified Reynolds equation, including slip, is derived. Based on this modified Reynolds equation, the pressure distribution and the load capacity of a slider bearing are obtained. Part (ii) presents the Darmstadt Slip Length Tribometer, utilized for measuring the slip length of technical rough surfaces. Part (iii) shows the temperature dependent results of the slip length measurements and the effect on the load capacity of the slider bearing in comparison to the standard no slip boundary condition.

The piston/cylinder interface in axial piston machines requires both sealing and bearing functions. The fluid and structure coupled physical phenomena including the temperature distribution of the piston and cylinder block controls the gap fluid behavior, therefore, the dual functions of the piston/cylinder interface. Instead of addressing the heat transfer problem of the piston and the cylinder block separately as the former model, the proposed advanced heat transfer model solves the temperature distribution of both solid bodies together using the fluid domain heat transfer characteristic to assemble the two solid parts. Comparing to the former unconnected heat transfer model, the integrated model is found more robust and accurate especially at challenging operating conditions.