PSI - Issue 41

A.R.F. Soares et al. / Procedia Structural Integrity 41 (2022) 48–59 Soares et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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• Allow a maximum load of 20 kN; • Loading in pure I, pure II and mixed I+II mode;

• Unrestricted mixed-mode ratio variation over a wide range of the fracture envelope; • Measurement of  using a linear variable differential transformer (LVDT) system; • The equipment must not mark the test specimen during the tests.

2.3. Methodology The equipment arises in response to the need to increase confidence in the design of adhesive structures, since it is important to be able to accurately predict their strength. The developed MMB test equipment aims to be an evolution of the equipment proposed by Chaves (2013). Thus, initially, a critical and detailed analysis of the several existing developed equipment was accomplished, with emphasis to the equipment of Chaves, to overcome the weaknesses of each equipment and create an improved version. The proposed equipment was designed by the FEM, to optimize the structure for a maximum load of 20 kN, including several iterative design stages up to reaching the final solution. All engineered components were manufactured in high strength steel. The remaining components of the equipment are standard components. In this paper, the final solution is initially described, including the several mechanisms, working principles and FEM analysis. The manufacture and respective assembly of the equipment, as well as the tests carried out, are described next. Finally, working validation of the MMB equipment is accomplished Although several devices for mixed-mode testing of adhesive joints are already reported in the literature, it is also observable that limitations still exist. From those available in the literature, nine devices were further analysed based on their Strengths, Weaknesses, Opportunities, and Threats (SWOT analysis). Then, the device developed by Chaves (2013) was chosen as a base for further improvements. Subsequently, the chosen device was analysed through a FEM analysis based on the requirements of Section 2.2, leading to the identification of the points needing attention. It was found that some of the elements of the original device may yield whilst testing adhesive joints, which is not ideal. The FEM analyses were carried out using SolidWorks® software (SolidWorks 2020, Dassault Systèmes, INC). 3.1. Description of the final solution The proposed device is shown in Fig. 1. After analysing the device of Chaves (2013), it was found necessary to increase the length of the members to allow the testing of longer adhesive joints. Perforated beams were used to allow varying the loading points, and so the mode to be tested. These perforations had to be accurate in both position and diameter. The use of calibrated commercial pins was included, adding accuracy, and increasing the usability of the device. Stress concentration areas on the components were also addressed in the design process. Finally, improvements were made to include provisions for future measurement devices like LVDTs (item 12 in Fig. 1 (b). The approximate overall dimensions of the improved device are height=415 mm, length=220 mm, and width=290 mm, and the final weight is approximately 28 kg. with experimental tests. 3. Equipment design