Analisis Pengaruh Ledakan Bawah Air Terhadap Struktur Double Bottom Kapal menggunakan Metode Smoothed Particle Hydrodynamics

Yurahman, Sandy Prayitna (2026) Analisis Pengaruh Ledakan Bawah Air Terhadap Struktur Double Bottom Kapal menggunakan Metode Smoothed Particle Hydrodynamics. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Struktur double bottom merupakan elemen penting pada lambung bawah kapal yang menjaga integritas dan keselamatan struktur, sehingga ketahanannya terhadap beban impulsif akibat ledakan bawah air perlu dievaluasi secara kuantitatif. Penelitian ini menganalisis respons struktur double bottom kapal patroli berbahan aluminium terhadap beban ledakan bawah air (underwater explosion) menggunakan metode Smoothed Particle Hydrodynamics (SPH) yang dikopel dengan metode elemen hingga pada perangkat lunak ANSYS LS-DYNA. Pendekatan ini memungkinkan perambatan gelombang kejut dan interaksi fluida-struktur ditangkap dalam satu simulasi terkopel. Objek kajian dibatasi pada satu blok struktur bagian haluan hingga tengah kapal dengan fokus pada double bottom. Muatan TNT dimodelkan dengan persamaan keadaan Jones Wilkins Lee, air laut dengan persamaan keadaan Grüneisen, dan material aluminium dengan model Johnson-Cook. Pembebanan divariasikan pada massa 5, 10, dan 15 kg TNT serta jarak 1, 3, dan 5 meter, sehingga diperoleh sembilan kombinasi. Model diverifikasi melalui uji konvergensi elemen (selisih 0,42%) dan divalidasi terhadap perhitungan empiris Cole (galat tekanan puncak 1,94%). Parameter yang dievaluasi meliputi deformasi total, tegangan ekuivalen von Mises, dan regangan plastis ekuivalen. Hasil menunjukkan deformasi maksimum 107,850 mm, tegangan maksimum 408,10 MPa, dan regangan plastis tertinggi 0,1657. Seluruh variasi melampaui batas luluh aluminium 201 MPa sehingga mengalami deformasi plastis permanen, namun tidak ada yang mencapai ambang kegagalan material 0,2, dengan variasi ketiga (W = 15 kg dan R = 1 m) sebagai kondisi paling kritis, yaitu mencapai 82,9% dari ambang kegagalan. Respons struktur secara umum meningkat seiring bertambahnya massa muatan dan menurun seiring bertambahnya jarak ledakan, sehingga kombinasi massa terbesar pada jarak terdekat merupakan kondisi paling berbahaya bagi struktur double bottom kapal.
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The double bottom structure is a critical component of a ship's lower hull that maintains the integrity and safety of the structure; therefore, its resistance to the impulsive loading of an underwater explosion must be evaluated quantitatively. This study analyzes the response of the double bottom structure of an aluminum patrol vessel to underwater explosion loading using the Smoothed Particle Hydrodynamics (SPH) method coupled with the finite element method in the ANSYS LS-DYNA software. This approach enables shock wave propagation and fluid-structure interaction to be captured within a single coupled simulation. The scope is limited to a single structural block from the bow to the midship, focusing on the double bottom. The TNT charge is modeled with the Jones Wilkins Lee equation of state, the seawater with the Grüneisen equation of state, and the aluminum material with the Johnson-Cook model. The loading is varied over charge masses of 5, 10, and 15 kg of TNT and standoff distances of 1, 3, and 5 meters, yielding nine combinations. The model is verified through a mesh convergence study (a difference of 0.42%) and validated against Cole's empirical calculation (a peak-pressure error of 1.94%). The evaluated parameters comprise total deformation, von Mises equivalent stress, and equivalent plastic strain. The results show a maximum deformation of 107.850 mm, a maximum stress of 408.10 MPa, and a highest equivalent plastic strain of 0.1657. All variations exceed the aluminum yield limit of 201 MPa and therefore undergo permanent plastic deformation; however, none reaches the material failure threshold of 0.2, with the third variation (W = 15 kg and R = 1 m) as the most critical condition, reaching 82.9% of the failure threshold. In general, the structural response increases with charge mass and decreases with standoff distance, so the combination of the largest charge at the closest distance is the most dangerous condition for the ship's double bottom structure.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Double Bottom, Underwater explosion (UNDEX), Smoothed Particle Hydrodynamics (SPH), ANSYS LS-DYNA, Double Bottom, Underwater explosion (UNDEX), Smoothed Particle Hydrodynamics (SPH), ANSYS LS-DYNA
Subjects:	V Naval Science > VM Naval architecture. Shipbuilding. Marine engineering > VM156 Naval architecture V Naval Science > VM Naval architecture. Shipbuilding. Marine engineering > VM161 Ships--Hydrodynamics V Naval Science > VM Naval architecture. Shipbuilding. Marine engineering > VM163 Hulls (Naval architecture)
Divisions:	Faculty of Marine Technology (MARTECH) > Naval Architecture and Shipbuilding Engineering > 36201-(S1) Undergraduate Thesis
Depositing User:	Sandy Prayitna Yurahman
Date Deposited:	05 Aug 2026 01:14
Last Modified:	05 Aug 2026 01:14
URI:	http://repository.its.ac.id/id/eprint/143519

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