Study On Intensity Analysis And Fatigue Life Of Corn Combine Chassis Machine Frame

Fatigue strength study is the foundation of improving the reliability as well as an important means to reduce the structural mass. The frame is the main bearing load parts of corn combine harvester, which is the important direction of structure optimization, in order to reduce the structural weight and improve the fatigue reliability, the fatigue life of corn combine harvester research was carried out. Major contents of the research are as following:(1) By investigating and analysising the background and situation about the fatigue strength research, the technical route of corn combine harvester frame’s fatigue life research was determined. The nominal stress approach is used to predict the fatigue life. Strain gauge is selected to measure the real-time stress and the rain flow counting is chosen to make the load spectrum. With the load spectrum data and the S-N curve, using the Miner rule evaluate the accumulated fatigue damage.(2) Building a data acquisition system. Data acquisition system consists of hardware and the software. The hardware includes sensors, data acquisition module and computer; the software includes QuantumX and Catalan.When determines the strain gauge measurement location, modal analysis and static analysis were used to find out the high stress concentrated points. With the appropriate method, the strain gauge paste is finished. Connecting data acquisition module, the strain gauge and computer, the real-time strain data collecting system was established.(3) field data collection and data analysis. In order to determine the benchmark of the strain measurement, the calibration experiment of data acquisition system was carried out. Finished field experiments, the strain time histories of various typical conditions were collected. After the strain data acquisition, data preprocessing is carried out to ensure the prediction accuracy, including deleting singular point, filtering the power frequency interference, eliminating signal trend.At the same time, the stress data was analyzed. And the results show that the static strength meets the design requirements and signal amplitude is in accordance with normal distribution. S4, S13, S5, S8, S16 points show dynamic load characteristics; S1, S2, S3, S15 points show obvious static load characteristics; As speed increasing, other points shows obvious dynamic load characteristics. The frequency spectrum of the front and rear axle is focused on 0-20 Hz, the frequency spectrum of the frame beam is focused on the 0-10 Hz, The frequency spectrum of the support structure is focused on 0-40 Hz. The frequency spectrum distribution shows that the design of the chassis frame can effectively reduce the influence of the resonance.(4) Fatigue life calculation and intensity analysis. With the S-N curve of the material and the load spectrum, the fatigue life of each part was calculated. The result shows that, the fatigue life of front axle is 2.63 million hours, the fatigue life of the frame is 24.1 million hours, the fatigue life of the rear axle is 23.8 million hours. The corn harvester frame design life is 7072 days, which can meet 30 years.(5) The optimization design of the key part in frame. Based on the static strength and fatigue life data, using CAE software redesign the mechanical structure of key part. The result shows under the condition of meeting the strength requirement the new model can reduce 24% part mass.