Analytical and Modal Analysis of Floating Shaft Failure in a Ship Unloader Crane”.

Fauzi, Moh Iqbal (2026) Analytical and Modal Analysis of Floating Shaft Failure in a Ship Unloader Crane”. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Tesis ini menyajikan investigasi komprehensif terhadap fraktur prematur pada Floating Shaft Group (FSG) di Ship Unloader Crane (SUC). Dilakukan dengan keterbatasan bukti fisik, penelitian ini mengintegrasikan perhitungan tegangan analitik, analisis modal berbasis Metode Elemen Hingga (Finite Element Method/FEM), serta evaluasi mekanis komparatif. Tiga konfigurasi FSG dianalisis: unit yang gagal pada SUC 02, pasangan utuhnya pada SUC 01, dan desain modifikasi yang diusulkan yang dilengkapi coupling fleksibel (FSG 03). Evaluasi tegangan analitik mengonfirmasi bahwa poros tidak mengalami kelebihan beban statis, dengan faktor keselamatan sebesar 1,61 menurut Teori Tegangan Geser Maksimum dan 1,59 menurut Teori Energi Distorsi. Temuan krusial diperoleh dari analisis modal dinamis, yang mengungkap kekurangan kritis pada konfigurasi FSG 02 yang gagal. Kekakuan sistem yang berkurang secara signifikan menyebabkan mode lentur elastis relevan pertama (Mode 3) muncul pada frekuensi 1,04 Hz dengan faktor partisipasi tinggi sebesar 330,13. Lebih kritis lagi, mode lentur orde lebih tinggi (Mode 5) teridentifikasi pada 4,98 Hz—frekuensi ini berbahaya mendekati harmonik ke-6 (4,8 Hz) dari eksitasi operasional utama. Mode spesifik ini mengkonsentrasikan sekitar 30,4% massa rotasi efektif sistem dan menunjukkan faktor partisipasi sangat tinggi sebesar 672,08, menciptakan risiko resonansi yang parah serta kelelahan siklus tinggi (high-cycle fatigue). Evaluasi pada tingkat komponen mengidentifikasi akar penyebab kegagalan: konfigurasi FSG 02 menggunakan dua universal joint secara seri yang dihubungkan oleh flensa coupling kaku. Desain suboptimal ini meningkatkan kekakuan parasitik sistem dan mengurangi kemampuan akomodasi ketidaksejajaran, berbeda dengan desain lebih tangguh pada FSG 01 yang menggunakan satu joint sentral tunggal. Analisis terhadap FSG 03 yang dimodifikasi menunjukkan perbaikan signifikan, di mana frekuensi alami kritis bergeser menjauhi rentang eksitasi operasional. Studi ini menyimpulkan secara definitif bahwa fraktur FSG disebabkan oleh kelelahan akibat getaran (vibration-induced fatigue). Konfigurasi mekanis yang cacat mengubah respons dinamis sistem, menurunkan frekuensi alaminya ke dalam rentang di mana eksitasi harmonik operasional dapat menginduksi getaran resonan. Rekomendasi untuk mencegah kejadian serupa meliputi: retrofit unit yang ada dengan modifikasi coupling fleksibel, penerapan protokol presisi ketidaksejajaran yang ketat, serta implementasi program pemantauan getaran berbasis kondisi (condition-based vibration monitoring). Untuk desain baru, disarankan mengadopsi konfigurasi FSG 01 yang telah terbukti keandalannya.
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This thesis presents a comprehensive investigation into a premature fracture of the Floating Shaft Group (FSG) in a Ship Unloader Crane (SUC). Conducted with limited physical evidence, the study integrates analytical stress calculations, Finite Element Method (FEM) based modal analysis, and comparative mechanical assessment. Three FSG configurations were analyzed: the failed unit in SUC 02, its intact counterpart in SUC 01, and a proposed modified design featuring a flexible coupling (FSG 03). Analytical stress evaluation confirmed the shaft was not statically overloaded, with safety factors of 1.61 per the Maximum Shear Stress Theory and 1.59 per the Distortion Energy Theory. The pivotal finding emerged from dynamic modal analysis, which revealed a critical deficiency in the failed FSG 02 configuration. Its significantly reduced stiffness caused its first relevant elastic bending mode (Mode 3) to occur at 1.04 Hz with a high participation factor of 330.13. More critically, a higher-order bending mode (Mode 5) was identified at 4.98 Hz. This frequency dangerously approaches the 6th harmonic (4.8 Hz) of the primary operational excitation. This specific mode concentrated approximately 30.4% of the system’s effective rotational mass and exhibited an extremely high participation factor of 672.08, creating a severe risk for resonance amplification and high-cycle fatigue. Component-level assessment identified the root cause: the FSG 02 configuration utilized two universal joints in series connected by a rigid coupling flange. This suboptimal design increased parasitic system rigidity and impaired misalignment accommodation, unlike the more robust single central-joint design of FSG 01. The analysis of the modified FSG 03 demonstrated a marked improvement, with critical natural frequencies shifting away from excitation ranges. The study conclusively determines that the FSG fracture was driven by vibration-induced fatigue. The flawed mechanical configuration altered the system’s dynamic response, lowering its natural frequencies into ranges where operational harmonic excitations could induce resonant vibrations. Recommendations to prevent recurrence include retrofitting existing units with the flexible coupling modification, enforcing stringent precision alignment protocols, and implementing a condition-based vibration monitoring program. For new designs, adopting the proven FSG 01 configuration is advised.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Floating Shaft, Ship Unloader Crane, Analytical Method, Modal Analysis, Resonance, Vibration-Induced Fatigue, Finite Element Analysis
Subjects:	Q Science > QA Mathematics > QA401 Mathematical models. Q Science > QA Mathematics > QA76.9 Computer algorithms. Virtual Reality. Computer simulation. Q Science > QA Mathematics > QA935 Vibration
Divisions:	Faculty of Industrial Technology > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User:	Moh. Iqbal Fauzi
Date Deposited:	04 Feb 2026 05:25
Last Modified:	04 Feb 2026 05:28
URI:	http://repository.its.ac.id/id/eprint/131981

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