铝合金材料在航空航天、汽车制造、船舶制造等领域广泛应用，其制造和装备过程中的载荷应力和残余应力会直接影响铝合金构件的机械性能和疲劳寿命。为评估铝合金的内部应力，文中基于声弹性原理，研究相控阵纵波检测技术，应用纵波传播时差法构建铝合金内部应力的检测方法；搭建相控阵纵波超声检测应力的实验系统，开展标定实验，获得铝合金内部应力与纵波传播声时差的关系式，得到超声传播声时差与内部应力之间的线性关系，在0~286 MPa的拉伸应力范围内，5 mm和3 mm厚铝合金板平均应力的标定绝对误差不超过2.85 MPa和10.82 MPa，相对误差不超过2.36%和13.93%，两种规格铝合金板的最大相对误差都出现在应力小于28.58 MPa的范围内，表明在小应力测量时需提高超声测量的分辨率和精度；应用相控阵纵波检测系统对5 mm厚铝合金板试样进行检测，平均应力误差为（1.174±4.567）MPa，绝对误差小于9.42 MPa，估算得到初始残余应力为3.329 MPa。实验结果表明，相控阵纵波超声法对5 mm厚铝合金板平均应力的检测效果好，应用纵波传播时差法可以对应力类型、应力大小、残余应力进行检测，该技术可以作为提高铝合金内部应力检测精度和检测效率的一种有效方法。

Aluminum alloy materials are widely used in the fields such as aerospace, automotive manufacturing and shipbuilding. However, the load stress and residual stress during the manufacturing and equipment process directly affect the mechanical properties and fatigue life of aluminum alloy components. In this paper, for the purpose of evaluating the internal stress of aluminum alloy and on the basis of acoustic elasticity principle, the phased array longitudinal-wave detection technology was studied, and an internal stress detection method of aluminum alloy was set up based on the time difference during longitudinal wave propagation. Then, an experimental system for phased array longitudinal-wave ultrasonic stress detection was set up, and calibration experiments were carried out to reveal the linear relationship between the internal stress of aluminum alloy and the time difference during longitudinal wave propagation, with the correlation equations being also formulated. The results show that, within the tensile stress range of 0~286 MPa, the absolute calibration errors of 5 mm and 3 mm aluminum alloy plates are respectively less than 2.85 MPa and 10.82 MPa, the corresponding relative errors are respectively not more than 2.36% and 13.93%, and the maximum relative errors of both specifications occur within the stress range of less than 28.58 MPa, meaning that it is necessary to improve the resolution and accuracy of ultrasonic measurement in small stress detection. The phased array longitudinal-wave system was then used to detect the stress 5 mm aluminum alloy plate specimens, and an average stress error of (1.174±4.567) MPa, an absolute error of less than 9.42 MPa as well as an estimated initial residual stress of 3.329 MPa was obtained. The experimental results show that the proposed phased array longitudinal-wave ultrasonic method is effective in detecting the average stress of 5 mm aluminum alloy plate; that the method based on the time difference during longitudinal wave propagation can be used to detect the stress type, stress size and residual stress; and that the proposed method is effective in improving the detection accuracy and efficiency of the internal stress detection of aluminum alloy.