The effect of substrate material properties on the failure behaviour of coatings in the Erichsen cupping test

Cheong, Zhao; Sorce, Fabian S.; Ngo, Sonny; Lowe, C. P.; Taylor, Alison

doi:10.1016/j.porgcoat.2020.106087

Cited by 4 publications

(3 citation statements)

References 37 publications

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“…The t-bending test has been accustomed to evaluate the formability of distinct coating systems in a cooperative way. The T-bend test results are registered in the form ‘xT’ where the x denotes the level of T-bend which a coating can sustain without failure by through-thickness cracking of the coating or loss of adhesion [ 24 , 25 ]. A 0T T-bend relates to a spacer thickness of 0× the sheet metal thickness, a 1T T-bend relates to a spacer thickness of 1× the thickness of the sheet metal, and so on.…”

Section: Resultsmentioning

confidence: 99%

Study on Press Formability and Properties of UV-Curable Polyurethane Acrylate Coatings with Different Reactive Diluents

et al. 2023

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UV-curable coatings have numerous advantages, including environmental sustainability due to 100% solid content, economic feasibility attributable to relatively fast curing time, decent appearance, mechanical properties, chemical resistance, and abrasion resistance. However, UV-curable polyurethane acrylate coatings on metals apparently restrict their engineering applications owing to low mechanical properties and poor thermal stability, giving UV-curable coatings less flexibility and formability. In this study, we evaluated the property change of films according to the type of reactive diluents that lowers the viscosity of UV-curing coatings for pre-coated metal and has a substantial effect on the curing rate, viscoelastic properties, adhesive properties, and flexibility of the film. Moreover, there are many changes in the properties of coatings according to varied curing conditions in order to evaluate the oxygen inhibition phenomenon during the curing process in the atmosphere. In particular, to evaluate the effect of reactive diluents on forming formability, which is the most crucial property for the pre-coated metal, this study used conventional formability tests, such as t-bending or the Erichsen test. Moreover, a cross-die cup drawing mold with a similar form as failure and Safety Zone was utilized in order to obtain clearer information on its actual formability. The analysis on the effect of failure and safety zone on the material used in press forming was conducted by assessing limit punch height and forming a limit diagram of the manufactured film according to varied reactive diluents.

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Section: Resultsmentioning

confidence: 99%

Study on Press Formability and Properties of UV-Curable Polyurethane Acrylate Coatings with Different Reactive Diluents

et al. 2023

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“…The material properties (Young's modulus, yield stress, post-yield behaviour, Poisson's ratio, etc.) of the HDG steel were taken from the material library of the modelling software and have been shown to be representative of the substrate used in the experiments [10,20]. The coating is not modelled as the strain in a coating is equal to the substrate surface strains [9,20].…”

Section: Finite Element Modellingmentioning

confidence: 99%

“…the applied strains) to be understood. The strains in the T-bend test are of particular interest as it has been noted in the literature that failure during the forming of coatings on metal substrates is a strain governed mechanism, as the strain which a given coating is subjected to is equal to that of the substrate surface [9,10,12,20]. The failure stress of the PPM is governed by the substrate [10]; hence, improved formability of coatings can be achieved by better understanding the deformation process and what critical forming strain level causes failure of the coating.…”

Section: Introductionmentioning

confidence: 99%

Quantification and analysis of coating surface strains in T-bend tests

Sorce

Ngo

Lowe

et al. 2021

Int J Adv Manuf Technol

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Pre-painted sheet metal (e.g. coil coated with polyester-melamine) undergoes large deformations when formed into architectural cladding or white goods. The coatings provide protection and superior aesthetics, so must withstand failure by cracking or delamination during forming. The T-bend test is an industry standard test used to qualitatively compare the formability of coatings and mimics the conditions experienced during hemming processes. The failure of coatings during forming is strain governed, so understanding the surface strains in the T-bend test is of great interest to manufacturers. For the first time, the maximum surface strains experienced during the T-bend test have been predicted using finite element modelling (FEM) and verified experimentally using digital image correlation. The experimental shapes of the deformed blank are compared with the FEM results for further verification. In addition, a novel analytical model is proposed to determine the maximum surface strains. It is shown that strains of up to ~ 225% are applied during a 0T test (bent around a zero thickness spacer) reducing to ~ 23% at 4T (bent around a four times sheet thickness spacer). The finite element model, experimental data and new analytical model show excellent agreement and indicate that behaviour is independent of the substrate thickness or material used. Understanding the strain behaviour quantifies the formerly qualitative T-bend. This will improve the efficacy of the test, allowing metal formers and coating developers to better understand the performance requirements, to reduce waste and to develop better coatings. Graphical abstract

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