【正文】 re 7 shows a typical FD plot. This plot is a carryover from the efforts to characterize dampers when all mechanical equipment used measured and charted only Force vs. Displacement. FD plots use the same force sign convention。 positive for pression, negative for rebound. For both pression and rebound, the forces in Figure 7 are not symmetric about the yaxis. The same hysteresis shown in the FV plots is the cause of this asymmetry. In an attempt to gain understanding, hysteresis can also be examined using a hypothetical ideal spring, a hypothetical ideal damper, and sinusoidal motion input. A hypothetical linear spring will produce a straight line with slope K in an FD plot and an ellipse in and FV plot (see Appendix A). A hypothetical linear damper will produce a straight line with slope C in an FV plot and an ellipse in an FD plot. Hysteresis in an FV plot for an actual damper results when the damper produces springlike forces. LITERATURE REVIEW A literature review was conducted with two major goals. The first goal was to obtain a better understanding of how individual internal ponents and internal flows had been characterized in the past by studying the development of parametric models for damper characterization. The second goal of the literature review was to gain an insight into the hysteretic behavior that occurs in characteristic FV plots. Understanding the causes of this phenomena and how it can be minimized are of crucial importance in damper design. Both of these concepts will be addressed in the cited literature. DAMPER SPECIFICATIONS The damper used for this research is a Tanner Externally Adjustable Gen 2 from Tanner Racing Products. It is a gas charged monotube configuration with a floating piston which separates the gas and oil chambers. The primary use for the Tanner Gen 2 s in quarter midget car racing, but their size, price, and range of available damping force make them appropriate for Formula SAE racecars as well. The Tanner Gen 2 is ightweight, relatively inexpensive, and can attain the desired damping forces with nterior modifications. Figure 8 shows a three dimensional model of the Tanner Gen 2 damper. The length at maximum extension of the damper is inches from centers of the spherical mounting bearings. The stroke of the damper is approx three inches. Outer housing of the damper and end caps are made of aluminum, while the chromed rod is made of polished steel. The end caps are threaded for removal which makes disassembly easy for tuning or rebuild purposes. The design of the piston and the shims used for controlling the piston orifice flow allow these parts to be manufactured much less expensively than most other racing dampers. The piston is made of machined aluminum and contains six straight orifice flow holes. The piston is shown in Figure 9. The piston flow orifices have diameters of .038” and the center hole for mounting the piston on the rod is ” diameter. The groove on the outer diameter of the cylinder is for the rubber seal between the piston and the cylinder wall. This piston design is less plex than that of an Ohlins or Penske brand damper and this simple design is much less expensive to produce. Depending on the desired damping levels, pistons are available with the flow orifice diameters from ” (soft damping) to ” (hard damping). Without any shims, the six orifices allow flow in both pression and rebound. A separate shim tuning kit is also available from Tanner racing products。 it is shown in Figure 10. The shims kit from Tanner Racing includes carbon fiber shims. The shims have almost an identical modulus of elasticity and Poisson’s ratio to that of steel, but are much lighter in weight. The shims contain holes at locations corresponding to holes in the piston that can be used to create one way flow for pression or rebound. For example, if a two hole shim is used for the pression side of the piston and a three hole shim for the rebound side of the piston, two oneway paths would exist for rebound and three paths would exist for pression as long as no holes are shared. Also a bination of one way and two way flows can be created. The arrangement of the shims can create numerous possibilities for tuning the Tanner Gen 2 damper. It would also be possible to create shims of varying thicknesses or different materials to achieve desired damping traits. The threaded needle valve for adjusting the bleed orifice flow has turns. The notation of zeros turns is analogous to a fully closed bleed orifice. The larger the number of turns of adjustment, the more the bleed orifice is open. This is a practical consideration since the fully closed position is easy to identify. The damper fluid used was Tanner Tuned Shock Oil. The properties were unknown for this oil, so typical 5W oil values were used for modeling purposes. Density and viscosity were of primary importance.