The uncertainty in stiffness and damping of an automotive vehicle’s trim-structure mounts and its effect on the variability of the vibration transfer function

Abstract

A large number of plastic clips are used in an automotive vehicle to connect the trim to the structure. These are small clips with very small masses compared to the structural elements that they connect together; however, the uncertainty in their properties can affect the dynamic response. The uncertainty arises out of their material and manufacturing tolerances and more importantly the boundary conditions. A test rig has been developed that can model the mounting condition of the clips. This allows measurement of the range of their effective stiffness and damping. Initially, the boundary condition at the structure side is replicated. The variability is found to be 7% for stiffness and 8% for damping. In order to simulate the connection of the trim side, a mount is built using a 3D printer. The variability due to the boundary condition on both sides was as large as 40% for stiffness and 36% for damping. A Monte Carlo simulation is used in order to assess the effect of the uncertainty of the clips’ properties on the vibration transfer functions of a door assembly. A simplified connection model is used in this study where only the axial degree of freedom is considered in connecting the trim to the door structure. The uncertainty in the clip stiffness and damping results in a variability in the vibration transfer function which is frequency dependent and can be as high as 10% at the resonant peaks with higher values at some other frequencies. It is shown that the effect of the uncertainty in the clips effective damping is negligible and the variability in the dynamic response is mainly due to the uncertainty in the clip’s stiffness. Furthermore, it is shown that the variability would reduce either by increasing or decreasing the effective stiffness of the clips.

A hybrid approach combining DNS and RANS simulations to quantify uncertainties in turbulence modelling

“…Such uncertainties can have a large effect on the design and performance assessment for a wide variety of engineering applications, for example in turbine blade manufacturing (Thakur, Keane and Nair [1]), in structural properties such as stiffness and damping (Abolfathi et al [2]), or in operating parameters such as fuel burn performance (Amaral et al [3]).…”

The effect of isolation in controlling the variability of point connected structures with uncertain structural attachments

“…Here the uncertain attachment, cable wiring with slowly varying properties represented by low bending stiffness beams, is connected to a host plate through multiple rigid connection points. Subsequently, identical elastic springs 20,29 are used to represent massless elastic mounts. When the elastic spring stiffness is significantly higher than the point dynamic stiffness of the two connected structures, then the relative displacement of the spring ends is negligible and a rigid link assumption is valid.…”

“…The mechanical properties used throughout this article are summarised in Table 1. Souza and Ferguson 8 and Abolfathi et al 29 estimated the bending stiffness of a typical automotive cable wiring bundle and door panel plastic clips, respectively.…”