Analisis Pengaruh Lebar Crack Pada Material Baja Karbon A36 Dengan Variasi Ketebalan Nonconductive Coating Pada Sambungan Las Di Pondasi Mesin Kapal Menggunakan Metode Eddy Current Testing (ECT)

Theresia, Nona (2017) Analisis Pengaruh Lebar Crack Pada Material Baja Karbon A36 Dengan Variasi Ketebalan Nonconductive Coating Pada Sambungan Las Di Pondasi Mesin Kapal Menggunakan Metode Eddy Current Testing (ECT). Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Pada pengelasan di bagian pondasi mesin kapal, sering terjadi crack akibat pengelasan. Crack yang terjadi di permukaan tidak terlihat karena adanya lapisan cat. Oleh karena itu, diperlukan metode Nondestructive Testing guna mendeteksi dan mengukur terjadinya crack pada material, sehingga segala dampak yang ditimbulkan dapat diminimumkan. Salah satu metode yang disarankan adalah Eddy Current Testing. Pada Tugas Akhir ini dilakukan analisis pengaruh lebar crack dan ketebalan lapisan cat terhadap sensitivitas metode ECT. Penelitian ini menggunakan empat buah spesimen. Ukuran dari keempat spesimen adalah sama yaitu, 120 x 300 x 6 mm. keempat spesimen memiliki jumlah crack yang sama, yaitu enam buah, dengan tiga crack orientasi melintang dan tiga crack orientasi memanjang. Masing-masing lebar crack adalah 0.25m, 0.50mm, dan 0.75mm. Kemudian diberikan lapisan cat yang berbeda pada tiap spesimen. Satu spesimen tidak dilapisi cat, satu spesimen dilapisi cat 100 µm, satu spesimen dilapisi cat 200 µm, dan satu spesimen yang lain dilapisi cat 300 µm. Hasil dari pengujian menunjukkan bahwa lebar crack mempengaruhi sensitivitas indikasi mesin ECT. Semakin lebar crack, maka lebar sinyal lift-off yang ditunjukan pada layar akan semakin kecil. Ketebalan lapisan cat pada spesimen juga memperkecil tinggi indikasi lift-off pada layar indikasi. Selain itu, posisi crack yang ternyata mempengaruhi hasil pendeteksian pada layar indikasi. Crack dengan orientasi memanjang memiliki noise yang lebih besar dibanding crack orientasi melintang pada permukaan lasan. ================================================================== Crack often occurred on engine bed due to welding process. Crack that initiated on the weld surface cannot be visually found due to covered by coating. NDT such as Eddy Current Testing may be employed to detect and measure the dimension of such crack. This research analyzes the effect of crack width and coating thickness to the sensitivity of Eddy Current Testing detection. Four crack specimens were used during this research i.e: 120x300x6 mm. Artificial crack manufactured using EDM machine were located on simulated weld metal, where each spesimen contain six artificial cracks. Three cracks were oriented transversally, while three other oriented longitudinally to the direction of weld joint. The width of the cracks were 0.25 mm, 0.50 mm, and 0.75 mm. The three samples then coated with nonconductive coating with 100 µm, 200 µm, and 300 µm thicknesses, while one sample was left uncoated. Results of the experiment indicated that the width of the crack significantly affect the sensitivity of Eddy Current detection. The wider the cracks the narrower the lift-off signals indicated by the machine. Thickness of the coating also reduced the height of the liff-off signals. Furthermore, crack orientation to the direction of weld joint also effect the detectability of the machine. On weld joint, crack that were oriented longitudinally to the weld slam produce greater noise than that of transversally oriented.

Item Type: Thesis (Undergraduate)
Uncontrolled Keywords: crack, non conductive coating, Eddy Current Testing, baja karbon A36.
Subjects: V Naval Science > VM Naval architecture. Shipbuilding. Marine engineering
Divisions: Faculty of Marine Technology (MARTECH) > Naval Architecture and Shipbuilding Engineering > 36202-(S1) Undergraduate Thesis
Depositing User: Nona Theresia
Date Deposited: 14 Dec 2017 07:40
Last Modified: 06 Mar 2019 01:53
URI: http://repository.its.ac.id/id/eprint/47618

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