Electro-mechanical Resonant Ice Protection Systems: Power requirements for fractures initiation and propagation

Abstract

This article focuses on resonant ice protection systems and studies fracture mechanisms at work for flexural modes having frequencies lower than100 kHz. The objective is to study the power required for fracture initiation and propagation in this frequency range. Two types of deicing mechanisms are studied in this paper: tensile stress dominant flexural modes and shear stress dominant flexural modes. Criteria are introduced to enable the comparison between these deicing mechanisms according to their power requirements and the selection of the most promising configurations. Eventually, the numerical results are compared to experiments to verify assumptions and computations. The contribution of this article is to put forward power-efficient de-icing configurations for resonant electromechanical de-icing systems using flexural modes. Low frequency flexural modes appear to be less power consuming for both mechanisms. Tensile stress dominant flexural modes have lower power requirements than shear stress dominant modes. The instantaneous peak power requirement to cover 90% of the area is estimated to be 5.5 kW/m². Nomenclature A = Area (m²) b = Fracture width (m) Cshear = Criterion for fracture initiation by shear stress Ctensile = Criterion for fracture initiation by tensile stress Ccoh = Criterion for cohesive fracture unstable propagation

Improving mechanical ice protection systems with substrate shape optimization

“…The tensile strength of the ice is in this article assumed to be around 3.0 MPa, which is a maximum value commonly used in the literature for freezer ice (Meng and Guo, n.d.;Petrovic, n.d.;Druez et al, 1986;Reich et al, 1994;Andrews and Lockington, 1983). After initiation, in most cases, the fracture instantaneously propagates to the interface thanks to the unstable behavior of the crack (second step of the fracture mechanism) (Palanque et al, 2021). This is explained using the Griffith theory on fracture propagation in brittle materials (Lawn, 1993;Anderson, 2005), which is detailed in the next part of the paper.…”

“…This paper focuses on the last part of the fracture mechanism, with the objective being to maximize ice delamination. Indeed, it has been shown in Palanque et al (2021) that the early steps are much easier to complete and that the challenge is all about completing the last step as it is the main stumbling block to full ice shedding.…”

“…Stresses need very fine meshes to be well-resolved, especially in this case where only local stresses are of interest at each discretization point. This assumption can be made as proportionality is shown between σ 2 and G (Palanque et al, 2021). The second constraint is the criterion introduced in section 2.3 to ensure fracture propagation without damaging the substrate.…”

“…In this article, various approaches are used to model mechanical de-icing. In section 2, a method based on previous works (Pommier Budinger et al, 2021;Palanque et al, 2021) is used to discuss ice delamination limits for substrates of constant thickness. In this paper, delamination is studied for a substrate fully covered with freezer ice in order to study the limits of the fracture mechanism and the potential area protected by flexural modes.…”

Cohesive Strength and Fracture Toughness of Atmospheric Ice

“…The configuration used in this study (described in Fig. 1) has been studied in previous works (Villeneuve et al, 2020c;Villeneuve et al, 2021c;Palanque et al, 2021;Gastaldo et al, 2022). The ice is accumulated on the sample covering the whole surface of the substrate.…”