Analisis Respons Struktur Double Bottom Kapal Akibat Ledakan Bawah Air Menggunakan Metode Uncoupled Eulerian Lagrangian

Pakpahan, Deven Darrell (2026) Analisis Respons Struktur Double Bottom Kapal Akibat Ledakan Bawah Air Menggunakan Metode Uncoupled Eulerian Lagrangian. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Struktur double bottom merupakan elemen kritis pada lambung bawah kapal yang menjaga integritas struktural dan keselamatan kapal, sehingga ketahanannya terhadap pembebanan impulsif ledakan bawah air perlu dievaluasi secara kuantitatif. Penelitian ini menganalisis respons awal struktur double bottom akibat shock wave primer menggunakan metode elemen hingga dengan solver eksplisit melalui pendekatan Uncoupled Eulerian-Lagrangian (UEL) pada perangkat lunak ANSYS Explicit Dynamics. UEL diterapkan dalam dua tahap, yaitu tahap Eulerian memodelkan detonasi muatan TNT dalam domain air dan menghasilkan riwayat tekanan, serta tahap Lagrangian menerapkan tekanan pada struktur. Muatan TNT dimodelkan dengan persamaan keadaan Jones-Wilkins-Lee, air dengan persamaan keadaan shock, dan material lambung Al5083 H116 dengan model Johnson-Cook. Pembebanan divariasikan pada massa 5, 10, dan 15 kg TNT serta jarak ledakan 1, 3, dan 5 m dari baseline kapal pada blok midship, menghasilkan sembilan kombinasi. Validasi distribusi tekanan Cole Spasial dilakukan pada Model Variasi 1 dengan membandingkan tekanan puncak teoritis Cole terhadap tekanan yang diimplementasikan di ANSYS setelah proses pemetaan node, menghasilkan selisih sebesar 1,74 persen. Parameter respons yang dievaluasi meliputi deformasi total, tegangan ekuivalen, dan regangan plastis ekuivalen. Hasil menunjukkan peningkatan massa muatan dan penurunan jarak ledakan meningkatkan intensitas respons struktur, dengan regangan plastis ekuivalen pada kondisi paling ekstrem mendekati ambang kegagalan material sebesar 0,2. Perbandingan pada salah satu variasi menunjukkan baja AH36 menahan tegangan ekuivalen jauh lebih tinggi namun deformasinya jauh lebih kecil daripada aluminium. Penelitian ini memberikan pemahaman kuantitatif tingkat kerusakan awal struktur double bottom kapal akibat shock wave primer.
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The double bottom is a critical structure of the lower hull that maintains structural integrity and ship safety, so its resistance to impulsive loading produced by an underwater explosion must be evaluated quantitatively. This study analyses the early structural response of a ship double bottom under the primary shock wave using the finite element method with an explicit solver through the Uncoupled Eulerian-Lagrangian (UEL) approach in ANSYS Explicit Dynamics. UEL is implemented in two stages: an Eulerian stage that models the TNT charge detonation in a water domain to obtain the pressure history, and a Lagrangian stage that applies it to the structure. The TNT charge uses the Jones-Wilkins-Lee equation of state, water with a shock equation of state, and the Al5083 H116 aluminium hull the Johnson-Cook model. Loading is varied over charge masses of 5, 10, and 15 kg TNT and standoff distances of 1, 3, and 5 m from the ship baseline at the midship block, producing nine combinations. The Cole Spatial pressure distribution is validated on Model Variation 1 by comparing the theoretical Cole peak pressure against the pressure implemented in ANSYS after node mapping, yielding a deviation of 1,74 percent. The response parameters evaluated are total deformation, equivalent stress, and equivalent plastic strain. Results show that increasing the charge mass and reducing the standoff distance raise the structural response intensity, with the equivalent plastic strain at the most severe condition approaching the material failure threshold of 0,2. In one variation, AH36 steel sustains a much higher equivalent stress but a far smaller deformation than aluminium. This study provides a quantitative understanding of the early damage level of the ship double bottom due to the primary shock wave.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	double bottom, ledakan bawah air, shock wave primer, Uncoupled Eulerian-Lagrangian, deformasi plastis, underwater explosion, primary shock wave, plastic deformation
Subjects:	V Naval Science > VM Naval architecture. Shipbuilding. Marine engineering > VM156 Naval architecture 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:	Deven Darrell Pakpahan
Date Deposited:	03 Aug 2026 10:02
Last Modified:	03 Aug 2026 10:02
URI:	http://repository.its.ac.id/id/eprint/142345

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