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Abstract(s)
A constante procura por novos e mais eficientes métodos produtivos leva a indústria a adotar cada vez mais as ligações adesivas. Este método de ligação visa substituir os métodos convencionais de ligação como o parafuso/rebite e a soldadura e é já predominante nas indústrias aeronáutica e automóvel. As principais vantagens das ligações adesivas são a sua capacidade de unir materiais dissimilares, a simplificação do processo de produção e a excelente resistência a solicitações de fadiga. Um dos principais aliados à proliferação deste tipo de junta foi o desenvolvimento de métodos numéricos computacionais precisos capazes de auxiliar no projeto e previsão de resistência da junta adesiva. Neste trabalho será estudada a resistência de juntas adesivas de degrau em aderentes de alumínio da liga AW 6082-T651 com um e dois adesivos, para vários comprimentos de sobreposição. Foram para este efeito considerados três tipos de adesivos com características distintas, o adesivo frágil Araldite® AV138 e os adesivos com diferentes níveis de ductilidade Araldite® 2015 e Sikaforce® 7752. Na análise experimental foram fabricadas as juntas e posteriormente testadas à tração. De seguida foram analisados os resultados obtidos em forma de curvas força-deslocamento (P-δ) e modos de rotura. A análise numérica foi elaborada no programa ABAQUS® com o auxílio de um modelo de dano coesivo integrado com forma triangular. O estudo numérico incidiu sobre as tensões de arrancamento e corte, resistência e energia dissipada. Os valores obtidos foram depois comparados entre si e também com valores relativos a juntas de sobreposição simples. A título de conclusão, foi possível validar a precisão dos modelos coesivos quando comparados com os dados obtidos experimentalmente. Para os comprimentos de sobreposição de 12,5 mm e 25 mm, a junta que revelou deter maior resistência foi aquela com a configuração Sikaforce® 7752-Araldite® 2015-Sikaforce® 7752 de proporção 12,5%-75%-12,5%. Nos comprimentos de sobreposição de 37,5 mm e 50 mm, a configuração mais vantajosa tratou-se da Sikaforce® 7752-Araldite® AV138- Sikaforce® 7752. A técnica de dois adesivos não revelou aumentos de resistência significativos, embora na energia dissipada o aumento de desempenho seja notório, principalmente nas juntas de comprimentos de sobreposição superior.
The constant search for new and more efficient production methods leads industry to increasingly adopt adhesive bonding. This joining method aims to replace conventional joining methods such as bolting/riveting and welding and is already prevalent in the aeronautics and automotive industries. The main advantages of adhesive bonds are their ability to join dissimilar materials, the simplification of the production process and the excellent resistance to fatigue stresses. One of the main allies to the widespread use of this type of joint was the development of highly accurate computeraided numerical methods capable of assisting in the design and joint strength prediction. In this work, the strength of stepped-lap joints in aluminium adherends of the AW 6082-T651 alloy with one and two adhesives, for various overlap lengths, will be studied. For this purpose, three types of adhesives with different characteristics were considered, the brittle adhesive Araldite® AV138 and the adhesives with different levels of ductility Araldite® 2015 and Sikaforce® 7752. In the experimental analysis, the joints were manufactured and subsequently tested in tension. Then, the results obtained in the form of load-displacement curves (P-δ) and failure modes were analysed. The numerical analysis was performed in the ABAQUS® program with the aid of an integrated cohesive zone model with a triangular shape. The numerical study focused on peel and shear stresses, strength, and dissipated energy. The values obtained were then compared with each other, and also with values related to singlelap joints. In conclusion, it was possible to validate the accuracy of the cohesive models when compared with the experimentally obtained data. For overlap lengths of 12.5 mm and 25 mm, the joint that proved to have the highest strength was the one with the Sikaforce® 7752-Araldite® 2015-Sikaforce® 7752 configuration of proportion 12.5%- 75%-12.5 %. In the overlap lengths of 37.5 mm and 50 mm, the most advantageous configuration was Sikaforce® 7752-Araldite® AV138-Sikaforce® 7752. The two-adhesive technique did not reveal significant increases in strength, although in the dissipated energy the performance increase is noticeable, especially in joints of higher overlap lengths.
The constant search for new and more efficient production methods leads industry to increasingly adopt adhesive bonding. This joining method aims to replace conventional joining methods such as bolting/riveting and welding and is already prevalent in the aeronautics and automotive industries. The main advantages of adhesive bonds are their ability to join dissimilar materials, the simplification of the production process and the excellent resistance to fatigue stresses. One of the main allies to the widespread use of this type of joint was the development of highly accurate computeraided numerical methods capable of assisting in the design and joint strength prediction. In this work, the strength of stepped-lap joints in aluminium adherends of the AW 6082-T651 alloy with one and two adhesives, for various overlap lengths, will be studied. For this purpose, three types of adhesives with different characteristics were considered, the brittle adhesive Araldite® AV138 and the adhesives with different levels of ductility Araldite® 2015 and Sikaforce® 7752. In the experimental analysis, the joints were manufactured and subsequently tested in tension. Then, the results obtained in the form of load-displacement curves (P-δ) and failure modes were analysed. The numerical analysis was performed in the ABAQUS® program with the aid of an integrated cohesive zone model with a triangular shape. The numerical study focused on peel and shear stresses, strength, and dissipated energy. The values obtained were then compared with each other, and also with values related to singlelap joints. In conclusion, it was possible to validate the accuracy of the cohesive models when compared with the experimentally obtained data. For overlap lengths of 12.5 mm and 25 mm, the joint that proved to have the highest strength was the one with the Sikaforce® 7752-Araldite® 2015-Sikaforce® 7752 configuration of proportion 12.5%- 75%-12.5 %. In the overlap lengths of 37.5 mm and 50 mm, the most advantageous configuration was Sikaforce® 7752-Araldite® AV138-Sikaforce® 7752. The two-adhesive technique did not reveal significant increases in strength, although in the dissipated energy the performance increase is noticeable, especially in joints of higher overlap lengths.
Description
Keywords
Juntas adesivas de degrau Juntas de dois adesivos Adesivo estrutural Método de Elementos Finitos Modelo de dano coesivo Previsão de resistência Alterações geométricas Stepped-lap joint Bi-adhesive joints Structural adhesive Finite Element Method Cohesive zone models Strength prediction Geometrical modifications