超声红外热像中激励源位置对裂纹生热的影响

Effect of excitation position on crack heating characteristics in sonic IR imaging

超声红外热像技术是一种新型无损检测技术,裂纹生热效果直接决定了裂纹的可检测性,而激励源位置是影响裂纹生热的因素之一。针对激励源位置对裂纹生热影响不清楚的问题,建立了超声换能器与被测金属平板的有限元模型,并搭建了超声红外热像检测系统;研究了不同激励源位置时裂纹的生热特性;并利用等效摩擦力、等效速度以及等效热流进行了有效验证。研究表明:当激励源位于裂纹面正下方时,由于裂纹面两侧振动同步,裂纹生热效果将受到抑制;而随着激励源位置向两侧移动,裂纹生热呈现出先波动上升后波动下降的趋势,而且预紧力越大波动越剧烈。研究成果有效地揭示了激励源位置对裂纹生热的影响规律,为超声红外热像技术的检测优化奠定了理论基础。

Sonic IR imaging is one of the emerging NDT methods. The detectability of the cracks is based on its heating effect, which correlates with several excitation conditions, for example the excitation position. For the unclear effect of excitation position on crack heating, the finite element model and the experimental system was utilized to study the characteristic of crack heating under different excitation positions, and made an effective verification by using the equivalent force, equivalent velocity and equivalent heat flux. The research shows that when the excitation position is under the crack face, the crack heating will be restrained as a result of vibration synchronization for the two crack surfaces.However, as the excitation position moves both sides, the crack heating will rise first and fall later with a fluctuation, and bigger engagement force can lead it more severe. The study results clearly demonstrate the effect principle of excitation position on crack heating, which may further lay the theory basis to the optimization of test conditions in the sonic IR imaging.