This paper investigates the effect of extra weight caused by the Direct Driven Hydraulics (DDH) in a micro-excavator. These projects are investigating the implementation of zonal or decentralized hydraulics for non-road mobile machinery (NRMM) and stationary industrial applications. The benefit of DDH is the combination of electric and hydraulic technologies in a compact package compared to conventional hydraulics, which enables a reduction of potential leakage points, flexible tubing, and boosting of the system efficiency due to switching to direct pump control instead of a loss-generating conventional valve-based control. In order to demonstrate these benefits for the excavator case, this paper proposes a system model approach to assess and predict energy consumption of the zonal hydraulics approach implemented with DDH in various working cycles, complemented by a structural analysis. The finite element analysis utilized for this demonstrated that the extra weight and selected location of DDH units do not negatively affect the structure of the excavator. Simulation results demonstrated that the energy consumption is approximately 15% higher with extra weight added by the three DDH units. Although approximately 20% more regeneration energy is produced, taking into account the regeneration energy, the increases in energy consumption are about 12%.
This
research studies the influence of local weld notch parameters on fatigue crack initiation sites in laser-hybrid butt welds, utilizing high-resolution 3D scans and fatigue tests to failure. The suitability of different local geometric weld notch parameters for fatigue strength characterization is investigated, and the current challenges associated with their measurements are highlighted. The weld notch shapes were found to fluctuate significantly, resulting in considerable variation in notch parameters over short intervals. Undercut depth was found to determine the critical location for crack initiation. There were several instances where the fatigue crack initiated from notches with large radii despite the presence of sharper notches, contrary to what is expected on the basis of previous investigations. The results of the present study indicate that the undercut depth is a suitable fatigue strength indicator for high-quality laser-MAG hybrid welds, overcoming the practical limitations of notch radius measurement.
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