There are next types of shock absorbers: articulated-suspension and telescopic. Two-way absorbers have used for intensive vibration damping in modern cars.
Two-way shock absorbers are most widespread on the modern cars. They create resistance during both recoil and compression step.
Articulated-suspension shock absorber
Articulated-suspension two-way shock absorber has double piston 2 with check valve. Shock absorber arm 4 moves piston 2 to one and other sides. During the smooth compression (a) fluid moves from area 3 in area 1 through calibrated valve stem gap 5 and through the gap of valve 6, overcoming the pressure force of the internal spring.
During the sharp compression (b) the pressure of fluid is up, as a result, the action of the outer spring overcomes. The flow area in the valve 6 increases sharply.
During the smooth resistance (c), the fluid moves from area 1 to area 3 by the slit in stem of valve 5. Valve 6 is closed. During the sharp resistance (d) the pressure of fluid is up, the force of valve spring 5 is overcame. Then the valve ups and the gap increases.