Wearing-in of a machine component can increase the conformity between contacting pairs and smoothen the surface topography. A two scale model, combining the wearing-in effects, resulting in changes ...in the surface topography, with the wear that occurs on the component, is presented. The geometry of the components is represented with measured coordinates. Wear leads to changes of the geometry, which has an effect on several tribological conditions, such as contact forces, relative velocities and conformity. Due to the wear on the topography scale, the load sharing is also affected. The model is applied to orbital hydraulic motors. The wear depth predicted with the model is qualitatively in good agreement with the wear depth recorded in experiments.
•A mixed lubrication running-in model is presented.•Changes in the surface topography due to wear affect the load sharing.•Running-in is observed in the model due to the wear on two length scales.•Measured surface profiles are used as input to the model.•Simulation results correlate well qualitatively with experiment.
Contamination in hydraulic systems is the cause of 70% of failures. This study highlights the performance degradation caused by solid particle contamination of hydraulic components: hydraulic gear ...pump, 4/3 valve, and orbital motor. Experimental durability tests of components with wear particles and test dust are used to investigate the effects of accelerated wear caused by these two types of contaminants. Results show that oil contaminated with wear particles reduces the volumetric efficiency of the gear pump by 18% and the hydraulic valve by only 0.8%, while oil contaminated with test dust reduces the efficiency of the pump by 76% and the hydraulic valve by 0.9%. This research provides insights for accelerating hydraulic component testing to improve system reliability and longevity.
Dielectric elastomer actuators (DEAs) have raised interest in the field of mobile robotics. In such a field, actuator design requires a fundamental understanding of DEA energy conversion performance. ...To provide insight into DEA mechanical work, energy consumption, and efficiency, this paper proposes a simple thermodynamic description completed by experimental loss factors obtained over a broad range of operating conditions and modes. Extensive data gathered on cone actuators show practical efficiency limits of ~ 26% for acrylic actuators (VHB 4905) operating under constant charge mode and ~ 18% for silicone actuators operating under constant voltage mode. While charge recovery could raise these limits to ~ 60%, the study of a DEA rotary motor shows significant efficiency degradation caused by unconstrained electrode boundaries.
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