Defect Detecting And Refabrication Evaluating For Drilling Tool Based On Metal Magnetic Memory Technique

Drilling tool plays an important role in drilling operation. Once the drilling tool failure occurs, the drilling operation will be stopped, which can result in huge economic losses. In order to effectively save resources and promote the development of circular economy, most failure drilling tools are used again after remanufacturing. So the detection and evaluation of drilling tools is particularly important to screen out the old drilling tool for remanufacturing.Metal magnetic memory(MMM) testing technology, a new nondestructive testing technique,can not only detect the macro damage, but also effectively evaluate the stress concentration and micro damage. Thus, the technique has the broad application prospect in drilling tool damage detection and remanufacturing blank selection.The loads and failure factors of drilling tool are studied. And the MMM signals are gotten and analyzed by MMM device and software, respectively. The results show MMM characteristics in damage zones are obvious, which indicates MMM testing can effectively detect the damage levels. It also reveals the single signal characteristic parameter can’t represent damage levels comprehensively. So the eight MMM characteristics parameters are used to describe the damage degree of drilling tool. Considering the limitation and ambiguity of actual MMM signals, the multiple classification fuzzy support vector machine(FSVM)classifier is established based on the membership degree of distance. The classifier utilizes the small sample properties of support vector machine(SVM) and the noise resistance of fuzzy membership degree. The result shows the radial basis kernel function has the highest classification accuracy. Moreover, the drilling tools are divided into three types based on damage levels, i.e. the normal one, the one for remanufacturing and the one for scrapping.And the drilling tool blank are selected and remanufactured. Then the MMM signals of remanufactured drilling tools are gotten. By analyzing the testing signal, it reveals the stress concentration degree of remanufactured drilling tools is smaller than that before remanufacturing. In the meanwhile, the damage levels maybe aggravate because of the fault during manufacturing process, which indicates MMM signal can reflect the stress concentration and damage state well. It provides a new method for the damage detection and refabrication evaluation of drilling tool.