Basic Research Of Non-destructive Evaluation Technology Of Residual Life For Crankshaft Remanufacturing Core

Remanufacture engineering is an effective way to build circular economy, realizeenergy saving and achieve sustainable development. Remanufacture production object (orremanufacturing core) is the recovering worn parts and its residual life prediction is the keylink to evaluate its remanufacturability. Because of the complexity, randomness andindividual difference of the worn parts damage, remanufacture life evaluation is achallenging problem.Based on crankshaft which is the critical engine parts, failure analysis, Finite ElementAnalysis, bending fatigue tests and signal processing are combined to explore the way forresidual fatigue life prediction of crankshaft remanufacturing core in this paper. The mainresearch contents are as follows:Dynamic performance of the bending fatigue test bench for crankshaft isstudied.Combined Finite Element Analysis and Experimental Mode Analysis, dynamicperformance of the mechanical test bench is analyzed and studied. The results show that thefirst-order natural frequency of the test bench is about40Hz and the first vibration mode ispure bending mode.The mechanical test bench could impose fatigue load to experimentalcrankshaft and its precision of measurement control system meets the functionalrequirements of the crankshaft bending fatigue tests.The real shape of the crack in Finite Element Model is used as an input parameter toobtain the distribution features of stress intensity factor of crack initiation zone and crackpropagation zone. Combined with residual stress test results, the general law of crankshaftfatigue crack propagation is made clearly: in the fatigue crack initiation stage, the crack tipalong the surface of the fillet has faster growth rate and the crack central portion has lowergrowth rate; When the crack size exceeds the threshold of shape ratio, the crack tip alongthe surface of the fillet has lower growth rate and the crack central portion has faster growthrate.Then the crack enters into rapid extended stage and residual fatigue life of crankshaft isin serious shortage.Based on the multi-sensor information which contains magnetic information, optical information and acoustic information, a fatigue life evaluation system for crankshaftremanufacture core is established. The fatigue crack initiation information of crankshaftfillet is obtained by using acoustic emission sensors; Based on Machine-vision opticalsensor, surface scale information of fatigue crack propagation is collected. Extended depthinformation of fatigue crack propagation is obtained by using the self-magnetic emissionsensor.Evolution law of the multi-sensor information in crankshaft fatigue crack initiationand propagation process is studied systematically. Acoustic emission technology perceivesfatigue crack initiation firstly and emits warning information for crankshaft lifeevaluation.With the growth of crack, Machine Vision and MMM signals simultaneouslyresponds to fatigue crack until the crankshaft fractures. A strong correlation is found outbetween the depth of crack propagation and the H p(y)component of MMM signals.Based on residual strength theory, a residual fatigue life evaluation model ofremanufacture crankshaft core which contains crack depth and surface crack lengthparameters is proposed. Combined crack depth which is obtained from MMM signals withWavelet Entropy with surface crack length which is obtained from Machine Vision, acomprehensive evaluation model of crankshaft residual fatigue life is initially established.Hidden Markov function is used to comparatively analyze the prediction accuracy betweencomprehensive evaluation model and traditional mechanical model. It shows thatcomprehensive evaluation model has higher prediction accuracy.