Effects of Postweld Parallel Heating on The Residual Stress Distribution and Fatigue Life of Weldments

Firmansyah, Aji Budiman (2025) Effects of Postweld Parallel Heating on The Residual Stress Distribution and Fatigue Life of Weldments. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Residual stresses introduced during welding can significantly reduce the fatigue performance of welded components. Tensile stresses, especially near the weld toe, promote early crack initiation under cyclic loading. This study proposes a novel postweld parallel heating method using TIG welding without filler metal, applied along the weld centerline to more effectively redistribute residual stresses in SS400 low-carbon steel weldments.
Tensile, fatigue, and residual stress tests were conducted to evaluate the effectiveness of the method. Optimal heating parameters (120 A at 15.7 mm/s) produced compressive residual stress up to −95 MPa at 7 mm from the weld centerline. This location is critical for fatigue initiation, and shifting the stress to a compressive state greatly enhances fatigue resistance.
Fatigue life improved significantly with postweld parallel heating. AW-PH-40 specimens showed 87,353 cycles, a 37% increase over the 63,629 cycles of as-welded (AW-40) samples. Residual stress at the weld toe was reduced from +330 MPa (as-welded) to near 100 MPa after five heating passes. These findings confirm that center-focused parallel heating is a practical, low-cost technique for improving the durability of welded steel structures
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Tegangan sisa yang muncul akibat proses pengelasan dapat secara signifikan menurunkan performa kelelahan (fatigue) dari sambungan las. Tegangan tarik, terutama di area toe las, mendorong inisiasi retak lebih awal saat mengalami pembebanan siklik. Penelitian ini mengusulkan metode pemanasan paralel pasca pengelasan menggunakan proses TIG tanpa logam pengisi, yang diterapkan sepanjang garis tengah las untuk meredistribusi tegangan sisa secara lebih efektif pada material baja karbon rendah SS400.
Pengujian tarik, kelelahan, dan tegangan sisa dilakukan untuk mengevaluasi efektivitas metode ini. Parameter optimal (arus 120 A dengan kecepatan 15,7 mm/s) menghasilkan tegangan sisa tekan hingga −95 MPa pada posisi 7 mm dari garis tengah las, yaitu area kritis tempat awal retak kelelahan sering terjadi. Perubahan tegangan dari tarik menjadi tekan di area ini terbukti meningkatkan ketahanan kelelahan secara signifikan.
Umur kelelahan meningkat signifikan setelah perlakuan pemanasan paralel. Spesimen AW-PH-40 menunjukkan umur kelelahan 87.353 siklus, meningkat 37% dibanding spesimen AW-40 tanpa perlakuan, yang hanya mencapai 63.629 siklus. Tegangan sisa di toe las juga berkurang dari +330 MPa (kondisi as-welded) menjadi mendekati 100 MPa setelah lima kali pemanasan. Hasil ini membuktikan bahwa pemanasan paralel terfokus di pusat las merupakan metode praktis dan ekonomis untuk meningkatkan daya tahan sambungan las terhadap pembebanan siklik.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	SS400 steel, parallel heating, residual stress, fatigue life
Subjects:	Q Science Q Science > QC Physics > QC320 Heat transfer
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User:	Aji Budiman Firmansyah
Date Deposited:	01 Aug 2025 09:38
Last Modified:	01 Aug 2025 09:38
URI:	http://repository.its.ac.id/id/eprint/125961

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