Analysis of Performance of Pneumatic Impact Absorbers

Performance of impact absorbers employing a pneumatic damper and a linear spring in parallel is analyzed. The governing nonlinear differential equations are derived and converted to nondimensional form. For case of a damper with fixed area orifice the equations are numerically integrated. Performance charts are presented in terms of three dimensionless parameters: mass, spring stiffness and orifice area ratio. Then, a second case is considered in which the damper orifice area is made to vary in two stages. During an initial portion of the stroke the orifice is closed and the air pressure rises to a certain value. In the second stage the orifice area varies in such a manner that a constant deceleration of the mass is achieved. A closed form solution of the governing equations is presented for the second case. The design and performance are compared with that of an impact absorber consisting of a spring only, and with those employing hydraulic dampers.