التحقق من انتشار الشقوق في الصفائح المعرضة لأحمال صدمية دورية
Cracks Propagation Investigation of Plates Subjected to a Cyclic Impact Loading
- الباحث
- أزهر صباح حميد
- المشرف
- فرج محل محمد - احلام لعيبي شريجي
- الجامعة
- الجامعة التكنولوجية
- الكلية / القسم
- قسم الهندسة الكهروميكانيكية / الهندسة الكهروميكانيكية
- الشهادة
- دكتوراه
- السنة
- 2024
- لغة الرسالة
- انكليزي
- الكلمات المفتاحية
- Crack propagation;Cyclic impact loading;Thin plates;Finite element method
Abstract
This study investigates the behavior of central crack propagation in thin plate aluminum alloys. Al 5052-O, and Al 6061-T6, were tested under a dynamic cycling impact load of 14.7 N. Analytical, numerical, and experimental analyses investigated crack propagation behavior under various conditions. The analytical solution estimates stresses from combined cycling impact loading and thermal stress over time. Stresses in the plates were estimated using classical plate theory and Lévy’s solution. The impact of loading and temperature changes over time was described using the Fourier series. The crack growth velocity was estimated using linear elastic fracture mechanics and effective stresses over time to determine the crack’s kinetic energy to create a mathematical model for dynamic crack propagation. This model was supported by using MATLAB software. A numerical analysis was carried out using ANSYS Workbench 19.R3 to simulate a three-dimensional model of the test sample. The crack growth simulation was automated, accurately predicting stress concentrations on the central crack in the plate. An electromechanical device was designed and fabricated for experimental work to simulate the effect of a cyclic impact load applied to a thin plate with a central crack, which was fixed in a thermal chamber. Using the digital controller to control the number of impacts, and a speed regulator to adjust the speed of the impact arm. Additionally, the surfaces of the plates were treated with a laser to determine the impact of this treatment on the growth of the crack. A device crack width tester of CK102 type was used as an accurate crack detection instrument to measure crack growth. Various tests were conducted on plates with different aspect ratios, crack angles, and crack lengths under different boundary conditions. The study found that the rate of dynamic crack propagation increases with longer crack lengths and larger plate aspect ratios. The study also revealed that the values for dynamic crack propagation rates were higher at a 0° angle than at 45° and 90° angles. Additionally, the results showed that for plates with aspect ratios of 1:1.5 and 1:2, crack closure occurred at a 90° angle. Moreover, the findings indicated that laser surface treat- ment impedes the growth of central cracks in the plate. The analytical, numerical, and experimental methods all showed good agreement in results.
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