PSI - Issue 17

Formiga J. et al. / Procedia Structural Integrity 17 (2019) 886–893 "Formiga J, Sousa L., Infante V." / Structural Integrity Procedia 00 (2019) 000 – 000

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3.1.2. Pull-out testing apparatus For the pull-out testing, it is necessary to build an apparatus. Regulations for pull-out structures are not well defined and consequently different testing apparatus are used by researchers who made experimental analysis, as Heimbs and Pein (2009), Song et al. (2008), Bunyawanichakul et al. (2005), Lim et al. (2011), Wolf and Brysch (2018), Kim et al. (2008). Analysing the apparatus by areas, it can be divided in three distinct parts, the first one is the mechanism to fix the insert plate, then the structure to apply the force on the insert and lastly the system used to record the data. The plate fixing is a-20mm-thick steel rig with a central hole of 250mm. This rig is made by two plates bolted together, and then the bottom one is attached to the testing machine. Some upgrades were made to the structure allowing a quicker change of specimens between tests. It contributed to improve the alignment of the plates and, consequently, experimental results. To pull the specimen, a T-form steel piece was made by water jet process and two holes were drilled for bolts. This piece was designed with dimensions close to the suspension bracket support, essentially in terms of hole distance and plate ’s contact area to minimize the differences for the numerical model. The experimental test was performed with an Instron tensile testing machine 3369 with a load capacity of 50kN, a SARA digital indicator installed in one of the bolts to measure the displacement and an action camera to record the indicator's displacement values. The testing rig and apparatus are shown in Fig 6.

Fig. 6. (a) Testing rig (b) testing apparatus.

4. Results and Discussion

For each test the load values from the Instrom testing machine and the displacement values from the digital indicators were plotted. The video record starts with the testing machine in order to match the time. Fig.7 shows the comparison between the experimental and numerical results for both configurations.

Fig. 7. (a) insert numerical and experimental result; (b) chamfer numerical and experimental result. The numerical results come from the finite element models, with the optimized laminate, where the force was changed in order to get the numerical curve for each reinforcement type.