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<p>A recurrent failure occurred in a 300-bar (30&#xa0;MPa) container-shifting hydraulic cylinder of an aluminum extrusion press, manifested by gland leakage, circumferential piston rod scoring, and repeated fracture of gland follower bolts. A structured forensic investigation integrating visual inspection, dimensional verification, fractography, stress analysis, and maintenance history correlation was conducted to determine the governing mechanism. Longitudinal grooves uniformly distributed around the piston rod were identified as three-body abrasive wear caused by metallic debris originating from a deteriorated welded oil port. Simultaneously, an unintended 10&#xa0;mm axial clearance in the gland assembly eliminated effective bolt preload and altered the intended load-transfer path. Under cyclic pressurization, hydraulic thrust was transmitted directly to sixteen M16 Grade 8.8 bolts. Stress evaluation incorporating thread-root stress concentration demonstrated alternating stresses approaching or exceeding practical fatigue endurance limits. Fractography confirmed high-cycle tensile fatigue with crack initiation at thread roots and limited final overload. Extending the guide bush length from 10 to 25&#xa0;mm reduced nominal bearing pressure by approximately 60%, eliminated assembly clearance, and restored proper load transfer. Removal of the contamination source and implementation of preload verification procedures prevented recurrence under identical service conditions. The findings demonstrate a field-validated coupled wear–fatigue mechanism and highlight the importance of integrated contamination control and preload integrity in high-pressure bolted hydraulic assemblies. The initiating mechanism was contamination-induced three-body abrasive wear of the piston rod–bush interface. The final structural failure mechanism was high-cycle fatigue fracture of the gland follower bolts once preload was lost due to the unintended 10&#xa0;mm axial clearance. The two mechanisms interacted synergistically.</p>

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Coupled Wear-Fatigue Failure of a High-Pressure Hydraulic Cylinder Due to Contamination and Preload-Loss

  • 期刊论文

  • 发表日期：

    2026年6月23日

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  • Rohit Sharma

摘要

A recurrent failure occurred in a 300-bar (30 MPa) container-shifting hydraulic cylinder of an aluminum extrusion press, manifested by gland leakage, circumferential piston rod scoring, and repeated fracture of gland follower bolts. A structured forensic investigation integrating visual inspection, dimensional verification, fractography, stress analysis, and maintenance history correlation was conducted to determine the governing mechanism. Longitudinal grooves uniformly distributed around the piston rod were identified as three-body abrasive wear caused by metallic debris originating from a deteriorated welded oil port. Simultaneously, an unintended 10 mm axial clearance in the gland assembly eliminated effective bolt preload and altered the intended load-transfer path. Under cyclic pressurization, hydraulic thrust was transmitted directly to sixteen M16 Grade 8.8 bolts. Stress evaluation incorporating thread-root stress concentration demonstrated alternating stresses approaching or exceeding practical fatigue endurance limits. Fractography confirmed high-cycle tensile fatigue with crack initiation at thread roots and limited final overload. Extending the guide bush length from 10 to 25 mm reduced nominal bearing pressure by approximately 60%, eliminated assembly clearance, and restored proper load transfer. Removal of the contamination source and implementation of preload verification procedures prevented recurrence under identical service conditions. The findings demonstrate a field-validated coupled wear–fatigue mechanism and highlight the importance of integrated contamination control and preload integrity in high-pressure bolted hydraulic assemblies. The initiating mechanism was contamination-induced three-body abrasive wear of the piston rod–bush interface. The final structural failure mechanism was high-cycle fatigue fracture of the gland follower bolts once preload was lost due to the unintended 10 mm axial clearance. The two mechanisms interacted synergistically.