The Detection Method Of Broken Strand Damage And Bending Fatigue Performance Research Of Automotive Wiring In Bending Fatigue Test

With the rapid development of the automotive industry, people are expressing more and higher requirements about the safety and comfort of the automotive which should be met with by increasing the amounts and complexity of the electrical equipments constantly. The safety and performance of the automotive are dominated by the wiring which acts as the connecting link among these parts, so the failure of the wiring is one of the most important failures of the automotive. What’s more, the current researches of the automotive wiring fatigue performance are deficient. Most of the countries have not put forward related industry standards. And the physical experiments are restricted by the detecting technology level.First, we investigated and surveyed the current wiring failure detection methods, analysised and compared the application advantages and limitations of these methods. According to the practical demand of the wiring bending test, we have improved the test method of YUASA, and put forward the dynamic impedance analysis method for the broken strand damage which can be used for real-time monitoring of wiring bending fatigue test. We researched the principles, established the test platform, put forward the signal processing algorithm and corresponding program based on LabVIEW and MATLAB, and analysised the feasibility and related rules of the method.In general, the e-N curve is for materials, but there are particularities for the wiring:the traditional transducer cannot be fixed on the wiring, as the size of the wring is too small, and the strands have complicated contact relations. So the stress and strain statues of the wiring cannot be measured directly. Thus, the general solution for this problem is the different e-N curve for different automotive wiring. With the help of ABAQUS, we calculated and analysised the steady-state cyclic stress-strain behavior of local hazardous areas of2kinds of wiring at corresponding five different levels strain amplitudes symmetric cyclic bending fatigue tests, and obtained the R50and R95C95e-N curves of2kinds of7-strand and19-strand wiring with50%broken strands under the symmetric bending fatigue tests from25samples with the help of Owen one-side lower-bound tolerance limit method.At last, the original data of fatigue life of wiring with50%broken strands was obtained by the wiring symmetric cyclic bending fatigue tests. The Weibull distribution of the fatigue life was established by median rank method based on the mean order number. According to the model parameters calculated, we analysised the fatigue performce of4kinds of automotive wiring.