Abstract
Durability tests of two water hydraulic cylinders with different surface roughness are made. The piston diameter, rod diameter and stroke of the test cylinders are 50 mm, 28 mm, and 250 mm, respectively. Each test cylinder is operated at a velocity of 0.25 m/s under a supply pressure of about 10.5 MPa by an electro-oil hydraulic servo cylinder which is placed in alignment with the test cylinder. The variations of friction characteristic, low speed performance, leakage characteristic of each test cylinder with operating distance are measured until 300 km operation. Friction force decreases at first with increasing operating distance and then becomes an almost constant value. No negative resistance characteristic is observed at low velocities. Both test cylinders can move very smoothly at velocities lower than 0.1 mm/s without stick-slip irrespective of the magnitude of surface roughness. Leakage flow rate tends to increase with increasing operating distance and surface roughness.
