PENGARUH SHOT PEENING DAN CHROMIC ACID ANODIZING PADA MATERIAL PESAWAT TERBANG AL 7050-T7651 TERHADAP LAJU PERAMBATAN RETAK FATIK

HARIS ARDIANTO, Dr. Eng. Priyo Tri Iswanto, S.T., M.Eng.

2015 | Tesis | S2 Teknik Mesin

Konstruksi pesawat terbang umumnya akan mengalami beban dinamis berupa tegangan tarik, tekan, bending, atau kombinasinya yang mengakibatkan kegagalan fatik. Selain itu, pesawat terbang juga beroperasi pada wilayah udara dengan berbagai kondisi lingkungan seperti keasaman, kebasaan, garam, kelembaban dan temperatur yang bervariasi, yang akan mempercepat laju korosi. Perlakuan permukaan shot peening dan anodisasi paling banyak diaplikasikan untuk meningkatkan ketahanan fatik dan korosi pada konstruksi pesawat terbang. Penelitian ini bertujuan untuk mempelajari dan membuktikan pengaruh shot peening dan chromic acid anodizing (CAA) terhadap laju perambatan retak fatik pada material Al 7050-T7651. Spesimen dibentuk sesuai dengan standar ASTM E647, dikelompokkan dalam empat kategori as received material-tanpa perlakuan (AR), base metal anodized (BMA), base metal shot peened (BMSP) dan base metal shot peened and anodized (BMSPA). Proses perlakuan shot peening (dengan intensitas Almen 0,006 A, diameter shot 0,017 inch) dan CAA (standar perusahaan) dilakukan di area surface treatment PT. Dirgantara Indonesia. Selanjutnya pengujian perambatan retak fatik dilakukan dengan mesin Servopulser di Lab. Bahan Teknik Jurusan Teknik Mesin UGM, dengan beban sekitar 11% dari tegangan tarik maksimum (spesimen standar ASTM E8M) yang dihubungkan dengan analisis beban kombinasi, dengan stress ratio R=0,1. Data hasil uji tersebut diolah menggunakan metode incremental polynomial untuk mendapatkan hubungan da/dN - ΔK. Hasil uji perambatan retak fatik pada spesimen AR menghasilkan angka konstanta Paris A=1,288×10-9dan n=2,02; BMA dengan A=1,603×10-11 dan n=3,6; BMSP dengan A=1,286×10-9 dan n=2,01 dan BMSPA dengan A=7,821×10-10dan n=2,02. Dengan demikian perlakuan anodizing terbukti meningkatkan laju perambatan retak fatik. Perlakuan shot peening terbukti menurunkan laju perambatan retak fatik meskipun tidak terlalu signifikan. Sedangkan penurunan laju perambatan retak fatik yang paling optimal adalah setelah gabungan perlakuan shot peening dan anodizing. Kata kunci : fatik, CAA, shot peening, konstanta Paris

Aircraft construction will generally experience a dynamic load such as tensile stress, press, bending, or a combination thereof resulting fatigue failure. In addition, the aircraft also operate in airspace with a variety of environmental conditions such as acidity, alkalinity, salt, humidity and temperature are varied, which will accelerate the corrosion rate. Shot peening surface treatment and anodizing most widely applied to improve fatigue resistance and corrosion in aircraft construction. This research aims to study and prove the effect of shot and chromic acid anodizing peening (CAA) on the rate of fatigue crack propagation the material of Al 7050-T7651. The specimen is formed in accordance with ASTM E647, grouped in four categories as received material-without treatment (AR), base metal anodized (BMA), base metal shot peened (BMSP) and base metal shot peened and anodized (BMSPA). The process of shot peening treatment (Almen intensity 0.006 A, 0.017 inch diameter shot) and CAA (standard companies) conducted in area of surface treatment PT. Indonesian Aerospace. Further testing fatigue crack propagation is done by machine Servopulser in Lab. Materials Engineering Department of Mechanical Engineering, UGM, with a load of approximately 11% of the tensile stress maximum (ASTM standard specimens E8M) associated with the analysis load combination, with a stress ratio of R = 0.1. The test result data processed using incremental polynomial method to obtain the relationship da/dN - ΔK.The results of fatigue crack propagation tests on specimens AR produce numbers Paris constants A = 1.288 × 10-9 and n = 2.02; BMA with A = 1.603 × 10-11 And n = 3.6; BMSP with A = 1.286 × 10-9 and n = 2.01 and BMSPA with A = 7.821 × 10-10 and n = 2.02. Thus anodizing treatment proven increase the rate of fatigue crack propagation. Shot peening treatment proven lowering the rate of fatigue crack propagation although not too significant. While the decline in the rate of fatigue crack propagation is the most optimal after the combined treatment of shot peening and anodizing. Keywords : fatigue, CAA, shot peening, constants Paris

Kata Kunci : fatik, CAA, shot peening, konstanta Paris; fatigue, CAA, shot peening, constants Paris