融合散斑干涉技术的阵列式洛伦兹力微颗粒探测方法

提出了一种阵列式洛伦兹力微颗粒探测法,该方法结合了散斑干涉技术的全场位移测量、分辨率高等特性与洛伦兹力微颗粒探测法中探测量为矢量、可探测内部缺陷等优势,探索了一种实时、在线、原位的缺陷检测方法.针对阵列式洛伦兹力微颗粒探测法中阵列式排布的多个悬臂梁位移测量问题,设计了大剪切数字散斑干涉系统,使来自于被测悬臂梁和安装悬臂梁的横梁的反射光发生干涉,形成剪切干涉,通过对相位差进行分析获得悬臂梁的绝对位移,并且以洛伦兹力及悬臂梁末端的位移量为中间量建立了散斑干涉相位差与缺陷体积之间的关系.本文通过实验成功获得了悬臂梁全场位移量以及缺陷的体积,通过散斑干涉的方法测量悬臂梁位移量理论分辨率可达30 nm,这使洛伦兹力微颗粒探测法具备了微米级缺陷的探测能力.

Lorentz force particle analyzer with an array probe based on speckle pattern interferometry

A new contactless technique called Lorentz force particle analyzer (LFPA) with an array probe for detecting the flaws in metallic material is presented in this paper. Based on the principle of LFPA, the shape and size of the flaw or the direction of the crack can be obtained by analyzing the pulses of the force acting on the permanent magnet. In the LFPA system, the small Lorentz force on the magnet is measured by a laser-cantilever system with high sensitivity, which operates in a similar principle to that of an atomic force microscope. The traditional displacement detecting method in the LFPA is not suitable for the array probe presented in this paper due to its complex structure. Therefore, speckle pattern interferometry is introduced into the LPFA. The speckle pattern interferometry can measure not only the out-of-plane displacement of the multiple cantilever in the array probe, or of slopes of deformation, but also the in-plane displacement. Those advantages make the speckle pattern interferometry a useful tool in the LFPA for analysing the shapes of the flaws and the directions of the cracks. In this paper, a Michelson-type shear of graphic setup with enlarged angle of view is built to measure the displacement of the cantilever which is deformed by the flaws in the sample. Four frames of shear under several grams before and after the deformation are captured and recorded by a digital camera. The phase difference is processed for calculating the displacement with the software which is designed for the LFPA. A full-field measurement of the cantilever displacement is achieved and the relationship between the phase difference and the volume of the flaws is also obtained successfully. The utilization of the speckle pattern interferometry technique in the LFPA leads to the invention of a new real-time, online, in-situ contactless technique of detecting the shapes of the internal flaws and the directions of the cracks.