The primary function of windscreen wipers is to remove water and debris from the windscreen, ensuring the driver has a clear view of the road ahead. Predicting wiper performance at the design stage is therefore important to ensure their safe operation. There is hence a need to develop physics-based models of wiper performance that can be used as evaluative tools early in the design stage. This paper presents an analysis of the impact of changing screen curvature on the contact force distribution of a wiper blade and the subsequent effects on the transient dynamics. The contact distributions for three distinct screen curvatures and three loading points are calculated via FEA (finite element analysis) and subsequently analysed via multiple connected mass spring dampers to model the wiper blade lip transient dynamics. By analysing time and frequency domain data for several calculated contact distributions it is found that decreasing the screen curvature reduces the contact force at the centre of the blade, however, increases the amplitude of vibrations and range of frequencies observed. Additionally, it is found that moving the loading point towards the tip of the blade reduces the amplitude of vibrations, a result analogous to that of increasing the screen curvature. Based upon the understanding gained through this work the influence of design criteria on wiper blades can now be assessed, and several suggestions made as to how to reduce windscreen wiper noise.

<div class="section abstract"><div class="htmlview paragraph">The primary function of automotive windscreen wipers is to remove excess water and debris to secure a clear view for the driver. Their successful operation is imperative to vehicle occupants’ safety. To avoid reliance on experimental testing there is a need to develop physics-based models that can quantify the effects of design-based decisions on automotive wipers. This work presents a suite of evaluative tools that can provide quantitative data on the effects of design decisions. We analyse the complex non-linear contact interaction between the wiper blade and the automotive screen using finite element analysis, assessing the impact of blade geometry on the contact distribution. The influence of the evolution of normal applied load by the wiper arm is also investigated as to how it impacts the contact distribution evolution. The dynamics of the blade are subsequently analysed using a multiple connected mass spring damper system. Additionally, we apply hydrodynamic lubrication theory to study the residual film thickness post wipe and assess the effect of wiper blade geometry and lubricant composition. Finally, the complete wiper system is studied using a lump dynamic model, and bifurcation analysis is applied to determine areas of instability due to friction induced vibrations. Additionally, the wiper dynamics modelling shows peak frequencies occurring at 30-50Hz, which agrees well with a documented range of chatter frequencies. The friction coefficients calculated within the hydrodynamic model fall within experimentally documented ranges of lubricated sliding friction, <i>μ</i> ≈ 0.1. Furthermore, the areas of operational stability predicted by our bifurcation model coincide with current experimentally determined optimal operational regions for automotive wipers.</div></div>