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Abstract(s)
Devido ao crescente uso das ligações adesivas na indústria, houve a necessidade de criar métodos que consigam prever o comportamento da junta, o qual depende de diferentes variáveis. Entre estas variáveis, as principais são o tipo de adesivo, o material do substrato e a geometria da junta. Em relação à natureza dos adesivos, estes são caracterizados desde frágeis e rígidos, como o Araldite® AV138, a dúcteis e menos rígidos, como o Araldite® 2015. Ainda existem adesivos de alta resistência e ductilidade como o adesivo poliuretano Sikaforce® 7888. Neste trabalho usou-se o Radial Point Interpolation Method (RPIM) de forma a prever a resistência de juntas de sobreposição simples (JSS) com diferentes comprimentos de sobreposição (Lo) para três adesivos. Para tal foram considerados dois critérios de cedência, o de von Mises e o de Drucker-Prager exponencial. Os critérios de rotura usados para prever a resistência das juntas têm como base a deformação sofrida pelo adesivo e não as tensões nele instaladas. A apresentação de resultados teve início com a comparação dos modos de rotura e a apresentação das curvas força-deslocamento (Pδ). Como apoio à discussão da resistência das juntas, e respetiva comparação entre os dados experimentais e numéricos, foi realizada uma análise de tensões de arrancamento e corte no instante da força máxima (Pmáx). Ainda foram obtidos os gráficos de deformação plástica efetiva e os gráficos de linhas de contorno para o instante de Pmáx. Com este trabalho foi possível concluir que o RPIM é bastante fiável para obter as tensões de arrancamento e de corte ao longo da camada adesiva. No entanto, em relação à precisão dos valores de Pmáx, esta difere em função das características mecânicas dos adesivos e do Lo. Para adesivos frágeis e rígidos, obtêm-se melhores resultados, mas à medida que se aumenta a ductilidade do adesivo, estes tendem a piorar.
Due to the increasing use of adhesive joints in the industry, there was a need to create methods that can predict the joint behaviour, which depend on different variables. Among these variables, the main ones are the type of adhesive, the substrate material and the joint geometry. Regarding the nature of the adhesives, they are characterized from brittle and stiff, such as the Araldite® AV138, to ductile and less stiff, such as the Araldite® 2015. There are still high-strength and ductile adhesives such as Sikaforce® 7888 polyurethane adhesive. In this work, the Radial Point Interpolation Method (RPIM) was used to predict the strength of single-lap joints (SLJ) with different overlap lengths (Lo) for three adhesives. For this purpose, two yield criteria were considered, von Mises and exponential DruckerPrager. The failure criteria used to predict the joint strength are based on the adhesive strain instead of the stresses. The presentation of results started with the failure mode comparison and the presentation of the load-displacement curves (P-δ). To support the discussion of joint strength, and the respective comparison between experimental and numerical data, a peel and shear stress analysis was performed at the instant of maximum load (Pmax). The plots of effective plastic deformation and the contour plots were also obtained at Pmax. With this work it was possible to conclude that the RPIM is very reliable to obtain the peel and shear stresses along the adhesive layer. However, in relation to the precision of the Pmax values, this differs depending on the mechanical characteristics of the adhesives and Lo. Better results are obtained for brittle and stiff adhesives but, as the adhesive's ductility increases, higher deviations are found.
Due to the increasing use of adhesive joints in the industry, there was a need to create methods that can predict the joint behaviour, which depend on different variables. Among these variables, the main ones are the type of adhesive, the substrate material and the joint geometry. Regarding the nature of the adhesives, they are characterized from brittle and stiff, such as the Araldite® AV138, to ductile and less stiff, such as the Araldite® 2015. There are still high-strength and ductile adhesives such as Sikaforce® 7888 polyurethane adhesive. In this work, the Radial Point Interpolation Method (RPIM) was used to predict the strength of single-lap joints (SLJ) with different overlap lengths (Lo) for three adhesives. For this purpose, two yield criteria were considered, von Mises and exponential DruckerPrager. The failure criteria used to predict the joint strength are based on the adhesive strain instead of the stresses. The presentation of results started with the failure mode comparison and the presentation of the load-displacement curves (P-δ). To support the discussion of joint strength, and the respective comparison between experimental and numerical data, a peel and shear stress analysis was performed at the instant of maximum load (Pmax). The plots of effective plastic deformation and the contour plots were also obtained at Pmax. With this work it was possible to conclude that the RPIM is very reliable to obtain the peel and shear stresses along the adhesive layer. However, in relation to the precision of the Pmax values, this differs depending on the mechanical characteristics of the adhesives and Lo. Better results are obtained for brittle and stiff adhesives but, as the adhesive's ductility increases, higher deviations are found.
Description
Keywords
Adesivos Juntas adesivas Juntas de sobreposição simples Análise elasto-plástica Métodos Drucker-Prager exponencial sem malha von Mises Radial Point Interpolation Method Adhesives Adhesive joints Single-lap joints Elastoplastic analysis Meshless methods Exponential Drucker-Prager