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<p>Superalloys are widely used in aerospace for their high tensile and yield strength under high temperatures. Laser ultrasonic technology (LUT) is the most promising means to achieve online real-time detection in extreme environments. The directivity and propagation path of laser-generated ultrasound are affected by inhomogeneous temperature fields. To accurately obtain detection signals in high temperatures, it is necessary to study the influence of inhomogeneous temperature fields on the directivity and propagation path of laser ultrasound (LU). In this paper, the directivity and amplitude of LU in the nickel-based superalloy are investigated by theoretical analysis under different temperatures, and the propagation paths of longitudinal (L) waves generated in the thermoelastic regime and shear (S) waves generated in the ablation regime are analyzed in inhomogeneous temperature fields by the developed procedure. It is shown that the amplitude of the L wave decreased by 22%, and the relative position variation <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({\Delta \beta }_{TL}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mi mathvariant="normal">Δ</mi> <mi>β</mi> </mrow> <mrow> <mi mathvariant="italic">TL</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> exceeded by 17%. Numerical simulations and experiments are conducted to study and verify the directivity, amplitude, and propagation paths of the LU under inhomogeneous temperature. The simulation results show that the amplitude of the L wave reduced by 17% in the thermoelastic regime, and the optimal receiving position decreases as the temperature gradients increase. The experiment results also show that the optimal receiving position decreases with rising temperature gradients, and verify the accuracy of the developed procedure and simulation models. The relationships between the temperature gradient and relative position changes are established in different temperature ranges. This work establishes a reference and theoretical basis for the application of LUT in high-temperature detection.</p>

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Study on Directivity and Propagation Path of Laser Ultrasound under Inhomogeneous Temperature in Nickel-based Superalloy

  • 期刊论文

  • 发表日期：

    2026年4月28日

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  • Yan Tang,
  • Hai Gong,
  • Tao Zhang,
  • Peng Cheng

摘要

Superalloys are widely used in aerospace for their high tensile and yield strength under high temperatures. Laser ultrasonic technology (LUT) is the most promising means to achieve online real-time detection in extreme environments. The directivity and propagation path of laser-generated ultrasound are affected by inhomogeneous temperature fields. To accurately obtain detection signals in high temperatures, it is necessary to study the influence of inhomogeneous temperature fields on the directivity and propagation path of laser ultrasound (LU). In this paper, the directivity and amplitude of LU in the nickel-based superalloy are investigated by theoretical analysis under different temperatures, and the propagation paths of longitudinal (L) waves generated in the thermoelastic regime and shear (S) waves generated in the ablation regime are analyzed in inhomogeneous temperature fields by the developed procedure. It is shown that the amplitude of the L wave decreased by 22%, and the relative position variation \({\Delta \beta }_{TL}\) Δ β TL exceeded by 17%. Numerical simulations and experiments are conducted to study and verify the directivity, amplitude, and propagation paths of the LU under inhomogeneous temperature. The simulation results show that the amplitude of the L wave reduced by 17% in the thermoelastic regime, and the optimal receiving position decreases as the temperature gradients increase. The experiment results also show that the optimal receiving position decreases with rising temperature gradients, and verify the accuracy of the developed procedure and simulation models. The relationships between the temperature gradient and relative position changes are established in different temperature ranges. This work establishes a reference and theoretical basis for the application of LUT in high-temperature detection.