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Geology of Urban Watersheds
Published in Daniel T. Rogers, Urban Watersheds, 2020
Waves erode shorelines in three main ways: Hydraulic action—Waves strike a steep slope and dislodge materialAbrasion: Solid materials such as sand or rocks grind together causing them to become rounded and smaller in size.Corrosion or dissolution—Sea water reacts with the sediments along the shoreline and slowly dissolves portions of the solid material
Characteristic analysis and motion control of a novel ball double-screw hydraulic robot joint
Published in Engineering Applications of Computational Fluid Mechanics, 2022
Jie Shao, Yongming Bian, Meng Yang, Guangjun Liu
The basic parameters of a ball double-screw hydraulic joint are shown in Table 1. The simulation parameters of the hydraulic control system are shown in Table 2. According to the parameters and action requirements of the hydraulic joint, the AVIC FF102/30 series is selected as the electro-hydraulic servo valve, and the parameters are shown in Table 3. The screw pair adopts an embedded ball friction transmission mode, and the ball is a quenched steel ball. The friction contact area between the ball and the circular arc screw pair is small, which is rolling friction, and the clearance is adjustable. While ensuring the assembly accuracy, the preload on the spiral groove can be almost ignored and the friction force is small. The traditional double-screw hydraulic joint adopts trapezoidal thread transmission, and the friction contact area is large. Because of the difficulty of processing, the local pressure and friction on the spiral groove will be large while ensuring the tight assembly. In this simulation experiment, a traditional double-screw hydraulic joint, with similar volume, displacement and hydraulic action area to the designed hydraulic joint, was selected for comparison, and the performance difference between the ball rolling friction and traditional trapezoidal thread sliding friction was analyzed.
Multi-scale approach to analyse the evolution of soft rock coastal cliffs and role of controlling factors: a case study in South-Eastern Italy
Published in Geomatics, Natural Hazards and Risk, 2021
Piernicola Lollino, Rossella Pagliarulo, Rosamaria Trizzino, Francesca Santaloia, Luca Pisano, Veronica Zumpano, Michele Perrotti, Nunzio Luciano Fazio
The low mechanical strength of the rock masses represents a predisposing factor of the failure processes, along with discrete joint patterns; in particular, joint systems and cracks that are enlarged by the hydraulic action and abrasion processes represent highly weak elements where failure propagation accelerates (Fazio et al. 2019) (Figure 2a). The most widespread mechanism of cliff instability in the study area is represented by block falls followed by free fall of debris, controlled by the presence of tension cracks, parallel to the cliff face; however, when persistent joints exist in the rock mass, slice detachments, topplings and wedge failures along two intersecting fractures can also occur. Falls of blocks and big slices of rocks are frequently triggered by the propagation of undercutting at the base of the cliff (notch) (Delle Rose and Parise 2004;2005; Fazio et al. 2019).