超声激励下混凝土板裂缝发热的有限元分析

Finite Element Analysis on Crack Heating of Concrete Slab under Ultrasonic Excitation

针对现有混凝土结构缺陷检测手段的不足,引入了混凝土裂缝检测的超声红外热像检测方法。①总结了超声红外热像检测的理论基础,对裂缝发热机制进行了推导和解释。②采用有限元软件ANSYS/LS⁃DYNA,考虑材料阻尼、自振特性、接触效应等情况,建立模型,对混凝土板件在超声激励下的发热效应进行了分析,结果表明在超声激励下,混凝土板件发热明显,而且在实验室条件下该方法适用于混凝土材料;裂缝不同区域接触和发热效应不相同,裂缝中下部接触作用强烈,发热明显;裂缝接触面节点生热由X方向(接触面法向)接触碰撞作用和Y方向(接触面切向)摩擦滑移作用共同决定;裂缝发热效应与板件自振特性有关,激励频率近于板件自振频率时,板件振动强烈,发热效应明显。以上结果对混凝土结构无损检测研究具有一定参考价值。

Aiming at the shortcomings of the existing defect detection methods for concrete structures,an ultrasonic infrared thermography detection method for concrete cracks was introduced.(1)The the⁃oretical basis of the ultrasonic infrared thermography detection method was summarized,and the ther⁃mal mechanism of crack was deduced and explained.(2)Considering material damping,self-vibration characteristics and contact effects,a model was established to analyze the heating effect of a concrete slab under ultrasonic excitation,based on finite element software ANSYS/LS-DYNA.The results show that,under ultrasonic excitation,the heating of the concrete slab is obvious,and the method is suitable for concrete material under the condition of laboratory.The contact and heating effects are dif⁃ferent in different areas of the crack.The contact effects in the middle and the lower part of the crack are strong and the heat is obvious.The nodal heating is determined by the contact collision effect of X direction(normal direction of contact surface)and the frictional slip effect of Y direction(tangent di⁃rection of contact surface).The heating effect of the crack is related to the self-vibration characteristics of the slab.When the excitation frequency is close to the slab’s natural frequency,the vibration of the slab is strong and the heating effect is obvious.The above results have a certain reference value for the nondestructive testing of concrete structures.