Multi-axial And Multi-excitations Road Simulation Test Method For Motorcycle Frames

As the most critical bearing components of motorcycle and due to road excitation and other external excitation sources, the frame keeps working under severe long-term impact of vibration, therefore frame fatigue or fracture become the most prominent feedback problems in the user market,so test device and methods for highly efficient and reasonable frame fatigue reliability test are in strong and urgent demand.Traditional fatigue reliability assessment of motorcycle frame mainly depends on the actual road test and testing field test,time-consuming and laborious, road simulation test based on remote parameter control(RPC) can efficiently and accurately indoor reproduced the vibration state of vehicle or parts under actual driving conditons,with nice repeatability and simulation accuracy, which is widely used in reliability assessment of vehicle and parts,while seldom used in the reliability examination of motorcycles and parts. In addition, test objects for the existed road simulation tests for motorcycle and parts are typically motorcycles,not motorcycle frames, thus the tests are less targeted for motorframe assessment and of low efficency. While the existed frame-specific road simulation tests mainly use the frame loading mode of single axial single incentive or single axial multiexcitations,which could not accurately simulate the multi-axial loads on motorcycle frame under actual driving conditions and could hardly meet the demand of the frame fatigue reliability assessment with low simulation accuracy.Therefore, develp a set of multi-axial multi-incentive road simulation device and establish multi-axial multi-incentive road simulation test method for fatigue durability of motorcycle frame based on the combination of CAD/CAE technology and the road simulation test techniques has an important theoretical significance and engineering application value.First, for a newly developed kind of motorcycle frame of a certain enterprise, several typical limited load conditions for motocycle frame under actual driving condition were established through loading characeristics analysis for motorcycle under actual driving condition.Combined with the loading and assessment method of fatigue testing machine of the enterprise, finite element analysis and strength evaluation for motorcycle frame under typical working conditions were completed, stress distribution characterisitcs and weaknesses of motorcycle frame under typical working conditions were therefore obtained,which provided a theoretical basis for measuring points selection of motorcycleframe for road load spectra collection.Then frame sensor arrangement was completed,frame road load spectra under typical road conditons were acquised, and due to pretreatment and statistics analysis in time domain, frequency domain and amplitude domain for collected road load spectra, the stress distribution characteristic of motorcycle frame under actual driving conditions was successfully obtained.Secondly, combined with the frame actual stress distribution, multi-axial multi-excitation road simulation test benches for motorcycle frames were designed, their feasibility were verified and loading method was obtained through multi-body dynamic simulation analysis.What’s more, through futher rigid-flexible coupled dynamic simulation analysis for test benches, stress- time history signal of frame measuring points was achieved, and through sensitivity analysis of measuring points, frame load spectrum simulation iteration measuring points were selected, and finally tesh bench optimization was completed.On this basis, the use of MTS road simulation test system components helped built a multi-axial multi-excitation road simulation test system for motorcycle frame.Then selected frame simulation iteration measuring points and extracted indoor expected response signal for road simulation test, based on the force- displacement coupled control and time- frequency domain error weighted romote parameter control load spectrum simulation iteration method, a bulk of load spectra simulation iteration of measuring points were conducted and frame load spectra under actual driving were accurately indoor reproduced. After that, road simulation excitation spectrum was extracted and factors having an effect on load spectrum simulation iteration accruracy were preliminarily explored, thus multi-axial multi-excitation road simulation test method for motorcycle frames was established.Finally, combined multi-axial multi-excitation road simulation test method for motorcycle frames with fatigue analysis method, virtual fatigue test method for motorcycle frames based on actual road similation excitation spectrum was proposed. Took the extracted excitation spectrum as the drive signal, used stress fatigue total life analysis method based on modal stress recovery(MSR) theory to give a fatigue life prediction of motorcycle frame and thus virtual fatigue test method for motorcycle frames based on actual road similation excitation spectrum was established.