PSI - Issue 59

Alfiy Alfatarizqi et al. / Procedia Structural Integrity 59 (2024) 420 – 427 A. Alfatarizqi et al. / Structural Integrity Procedia 00 (2024) 000 – 000

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1. Introduction Currently, the world is focusing on renewable energy, and the transition from fossil fuels to renewable energy has become one of the top global priorities. Wind energy is one of the promising forms of energy, as it has lower costs and is also more efficient in its application (Gantes et al., 2023). Poul la Cour, who originated from Denmark, was a major innovator in the late 19th century and after World War I, he proposed the creation of wind turbines with cross sectional blades resembling the angles of an airplane's propeller, which are now referred to as propeller-type wind turbines or wind turbines (Saputra, 2016). The wind turbine experiment with twin-bladed design was conducted in the United States in 1940. This large-scale turbine was known as the Smith-Putman machine, named after its designer Palmer Putman. It was constructed by the Morgan Smith Company from York, Pennsylvania, and had a capacity of 1.25 megawatts (MW). The wind turbine had a propeller diameter of 55 m, weighed 16 tons, and stood at a height of 34 m. However, one of its propeller blades broke in the year 1945. Wind turbines are mostly installed on either tubular or lattice towers. Having a tall tower is advantageous because wind speed increases with height above the ground. In the analysis and design of wind turbine construction, it's crucial to avoid the matching of blade rotation frequency with the natural frequency of the tower, as this can lead to tower resonance and failure. This complexity in tower design is a significant consideration in wind turbine engineering (Nezamolmolki & Shooshtari, 2016). Wind turbines are often installed with the main structure being cylindrical shells due to their excellent performance, mature processing techniques, and strong design (Zhang et al., 2021). Tubular structures with thin walls serve as the basic structure for pressure vessels in both marine, civil, and aerospace industries (Cerik, 2015). The applications of cylindrical tubes encompass both stationary and mobile tanks for the storage or transportation of liquids, pressurized hulls underwater for human habitation, and non-pressure equipment. Indeed, cylindrical tubes have a drawback, which is their vulnerability to instability or buckling because of their efficient geometric shape that allows for the creation of thin-walled structures. Buckling phenomena can occur in slender structures regardless of the material used. Buckling is the process in which a structure is unable to maintain its original shape and, as a result, will deform in order to establish a new equilibrium (Maali et al., 2023). However, cylindrical tubes also have a weakness, which is their susceptibility to instability or collapse, as their efficient geometric shape allows for the construction of thin-walled structures. Buckling phenomena occur in slender structures regardless of their material composition. Buckling is a process in which a structure is unable to maintain its original shape; instead, it undergoes deformation in order to establish a new equilibrium.

Nomenclature t

Shell thickness [mm] Cylindricall radius [mm] Cylindricall height / long [mm] E Young modulus [MPa] D Diameter of the cylinder [mm] Is the yield stress of the material [MPa] Passion ratio Ratio Numeric value / experiment value Axial stiffeners Circumferential stiffeners ℎ Height of stiffeners Thickness of stiffeners Density 2.7 x 10 −6 kg/mm 3 R L

Cylinder reference buckling load required to cause yield [MPa]