Search Results

Several recent product developments for vibration and motion control have needed passive viscous damping, in addition to traditional elastomer-based hysteretic damping, to be successful in their respective applications. In addition to attenuating steady-state vibration, an important function of these recent product developments is to control motion from impulsive or mechanical shock input. Examples are the cab mounts of off-highway vehicles that need damping in the vertical direction to control cab motion from ground input through the vehicle and some torsionally flexible couplings that need damping to control torque spikes from shift shocks or other transient events. In this work, the theoretical damped impulse response quantities of displacement, velocity, acceleration, force, jerk, yank, and jounce are investigated. This work shows that, for certain response quantities, there is a specific magnitude of damping that minimizes response from impulsive or mechanical shock input.

The procedure for selecting a flexible coupling to suppress driveline torsional vibration from the engine of an off-highway vehicle or stationary industrial unit with a remotely mounted driven unit is widely studied and documented. However, the successful selection of a torsionally flexible coupling in an off-highway vehicle or stationary industrial unit to suppress engine vibration can create new vibration and performance problems in the driveline and driven unit. This paper presents the unintended consequences of utilizing a torsionally flexible coupling, provides descriptive solutions to the unintended consequences and methods to avoid them.

This work presents theory for a passive vibration isolation component for which the effective stiffness changes with the frequency of steady-state operation. The effective stiffness can be passively adjusted, or tuned, to be a minimum at a particular frequency, thereby reducing transmitted vibratory forces at or near that frequency. The new suspension component offers performance similar to a lowly-damped, long-inertia-track hydraulic mount but with fewer components and with no fluid. Prototypes of the new suspension component have been built and tested. The results demonstrate that the new suspension component isolates vibratory forces for a relatively wide frequency range.

This paper presents simple but comprehensive modeling of the loads on the rubber sandwich-type mounts that often suspend the drum(s) in vibratory compactors or asphalt rollers. The goal of the modeling is to predict the overall performance of the rubber mount system. The modeling includes calculations to 1) identify and quantify all predictable low-frequency loads on the rubber mounts during normal vehicle operations, 2) predict the steady-state high-frequency vibration response of the drum, rubber mounts, and vehicle frame during compaction operations, 3) predict the heat generation in the rubber mounts from their hysteretic damping, and 4) predict the fatigue life and life distribution of the rubber mounts. Some typical results of the modeling are provided along with some brief criteria to assess suspension performance. Other, unpredictable suspension loads are discussed but not modeled.

This work provides a theoretical analysis of the natural and forced lateral vibration in a driveline having a flexible coupling and universal joints. The analysis is specific to the front driveline common in many off-highway vehicles which usually consists of a flexible coupling at the engine flywheel, the driveshaft, and one or two universal joints. A torsionally flexible coupling is often needed in a front driveline to suppress torsional vibration. The problem is that most torsionally flexible couplings are also inherently flexible in their radial and cocking directions. These additional directions of flexibility, compounded by the presence of universal joints, can result in unexpectedly low lateral natural frequencies of the driveline. With a few axial dimensions, mass properties of the driveline, and stiffness properties of the flexible coupling, this work provides simple, closed-form calculations for the lowest lateral natural frequencies.