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<p>Large-diameter thick-walled LSAW pipes are widely used in the transportation of oil and gas at sea. However, the bending forming of medium-thick plates is prone to produce crack defects. In this paper, an extended study on crack prediction for bending forming of medium-thick plates is carried out. An improved theoretical crack prediction model considering the neutral layer offset is proposed, aiming to improve the bending crack prediction accuracy of medium-thick plates. The improved Lemaitre ductile fracture criterion integrates the effect of large plastic strain accumulation on damage and investigates the effect of neutral layer offset on strain. With 7075-T6 aluminum alloy as the object, verified by theoretical calculation, DEFORM finite element simulation and macro–micro experiments, the neutral layer offset is 0.6–0.7&#xa0;mm when cracks initiate. The Lemaitre ductile fracture criterion threshold, <i>C</i>, at the time of experimental (<i>C</i> = 11.46) is compared with theoretically ( <i>C</i> = 11.9), and its relative error is 3.6%. The influence of the neutral layer offset on the accuracy of strain and crack prediction was verified. This criterion effectively improves crack prediction accuracy, provides theoretical support for optimizing the bending process of high-strength aluminum alloy medium-thick plates in marine engineering and aerospace fields.</p>

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Application of Neutral Layer Offset to Crack Prediction in Sheet Metal Bending Forming

  • 期刊论文

  • 发表日期：

    2026年1月8日

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  • Chen Zhang,
  • Qiang Li,
  • Sha Li,
  • Hao Liu,
  • Hailian Gui,
  • Leifeng Tuo,
  • Zhibing Chu,
  • Chunlei Shen

摘要

Large-diameter thick-walled LSAW pipes are widely used in the transportation of oil and gas at sea. However, the bending forming of medium-thick plates is prone to produce crack defects. In this paper, an extended study on crack prediction for bending forming of medium-thick plates is carried out. An improved theoretical crack prediction model considering the neutral layer offset is proposed, aiming to improve the bending crack prediction accuracy of medium-thick plates. The improved Lemaitre ductile fracture criterion integrates the effect of large plastic strain accumulation on damage and investigates the effect of neutral layer offset on strain. With 7075-T6 aluminum alloy as the object, verified by theoretical calculation, DEFORM finite element simulation and macro–micro experiments, the neutral layer offset is 0.6–0.7 mm when cracks initiate. The Lemaitre ductile fracture criterion threshold, C, at the time of experimental (C = 11.46) is compared with theoretically ( C = 11.9), and its relative error is 3.6%. The influence of the neutral layer offset on the accuracy of strain and crack prediction was verified. This criterion effectively improves crack prediction accuracy, provides theoretical support for optimizing the bending process of high-strength aluminum alloy medium-thick plates in marine engineering and aerospace fields.