KAJIAN METODA NDT UNTUK DETEKSI CACAT LACK OF FUSION PADA LASAN (Mudi Haryanto, Andryansyah, Lily Suparlina)

ABSTRAK
KAJIAN METODA NDT UNTUK DETEKSI CACAT LACK OF FUSION
PADA LASAN. Lack of fusion (kurang lebur) merupakan jenis cacat yang sangat
berbahaya dalam struktur pengelasan karena mempunyai efek takikan (notch) sehingga
retak mudah merambat dengan pembeban kecil. Lack of fusion terjadi karena logam las
tidak sepenuhnya mengisi sambungan lasan, ada ruang antara logam las dan logam induk
weld bead dimana terjadi lack. Tipe cacat ini sangat sulit di deteksi dengan metoda NonDestructive Test (NDT). Oleh karena itu perlu dilakukan penelitian dan pengkajian dengan
cara pembuatan simulasi jenis cacat sebagai referensi cacat lack of fusion yang mempunyai
orientasi cacat berbeda. Penelitian dilakukan pada penggunaan metode NDT radiografi dan
ultrasonik yang diujikan pada cacat referensi lack of fusion untuk mengetahui kemampuan
deteksinya. Sampel yang digunakan dari pabrikan sonaspection berupa cacat lack of side
wall fusion, lack of root fusion dan laminar fusion (lack of inter run fusion). Tahapan pertama
dilakukan pengujian dengan metoda ultrasonik, dilanjutkan dengan metoda radiografi. Hasil
penelitian menunjukkan untuk deteksi cacat lack of side wall fusion, lack of root fusion dan
laminar fusion (lack of inter- run fusion) tidak mampu di deteksi dengan satu metoda
radiografi atau ultrasonik tetapi perlu dua-duanya untuk saling melengkapi.
Kata kunci : lack of fusion, metoda NDT, radiografi, ultrasonik.
ABSTRACT
STUDY OF NDT METHOD FOR DETECTION OF LACK OF FUSION ON WELD. Lack of
fusion (less melting) type of defect is very dangerous in the welding structure because it has
a notch effect so that the cracking is easy with a small load. Lack of fusion occurs because
the weld metal does not completely fill the weld connection, there is space between the weld
metal and the parent metal or between the weld bead where there is lack. This type of defect
is very difficult to detect by the Non-Destructive Test (NDT) method. Therefore, it is
necessary to conduct research and study by making defect type simulation as a lack of
fusion defective reference that has a different defect orientation. The study was performed
on the usage of the radiographic and ultrasonic NDT methods that are tested on the lack of
fusion reference defects to determine its detection ability. The sample used from the
sonaspection manufacturer is a defect of lack of side wall fusion, lack of root fusion and
laminar fusion (lack of inter-run fusion). The first stage of testing is the ultrasonic method,
followed by radiographic methods. The results showed that detection of lack of side wall
fusion, lack of root fusion and lack of inter run fusion was not able to be detected by a single
radiographic or ultrasonic method, but both need to be complementary.
Keywords: lack of fusion, NDT method, radiography, ultrasonic.