| The frame of the rice transplanter is its main bearing structure, and the strength, stiffness and fatigue properties of the frame has significant and direct impacts on its service life, safety and operation reliability. The Chinese traditional rice transplanter frame design mainly refers to the frames of similar foreign products, and at the same time focus on the strength, stiffness and so on, but has no interest in the fatigue analysis of the frame. By testing the dynamic load spectrum of the rice transplanter which is in idle state and field planting condition, the paper get the fatigue life of the frame of the transplanter. Then the rice transplanter frame design may refers to the spectrum to analysis the fatigue life of the frame.The dissertation is to study the fatigue life of the transplanter frame with the use of the dynamic load spectrum of the rice transplanter which is in idle state and field planting condition.1)Established a finite element model of the frame of LNC8 rice transplanter, followed by a static mechanical analysis on the frame with the use of the finite element method to get the static stress extreme point of the frame. The middle area of the frame is where the highest stress extreme point appears to be 86.1MPa. The safety guarantee number is 2.73, it shows that the frame is safe. The test point on the frame was obtained per the extreme point and dynamic load spectrum.2)The test was settled per the dynamic load spectrum of transplanting machine, and then, the test got the load spectrums of the transplanter when it was in idle state and field planting condition. Both of two conditions completely cover the various work conditions of the transplanting machine.3)The original data of the load spectrum was processed through Matlab software programming. The data processing phrase, first of all, transformed the strain stress signals and get the resultant of equivalent stresses of test points, and then, eliminated noises of the equivalent stresses through the five point average method and the gradient threshold method, and also tested the noise removal effect by the rain-flow counting method. At the same time, according to time comparison between the idle state and field transplanting condition, the load spectrum was processed to get an integrated load spectrum of the frame.4)Because the load spectrum is a non-symmetrical cycle, it needs to use the Goodman method to correct the average stress before the calculation of the fatigue life so as to get an equivalent symmetrical cycle. By analysis of fatigue life of the frame, we get the fatigue life contours of the frame and to find that the extreme points in the static mechanical analysis were in good agreement with the hot spots of fatigue damage. When the transplanter was in idle state, it wouldn’t happen to fatigue failure; and in field planting condition, the fatigue life of the frame could be 19.9years which is almost about twice of the machine life. The conclusion is that the fatigue life of the frame is safe enough.Through this research, it is found that the risk point in the static mechanics analysis is basically in the same area as the fatigue risk point in the dynamic loading fatigue analysis, and that the hot spot areas under the static mechanics analysis need to be considered as fatigue damage hot spots in the frame design. Considering that the working environment of planting machines are worse than that of ordinary passenger vehicles, the actual fatigue life of the former machines are shorter than the latter ones even if they are under the same computational scheme and load spectrum, which is another point needing attention in transplanter vehicle design. This study established a relatively complete data recording of the transplanter load spectrum, enriched the reference database of transplanting machine design, and also established a replicable fatigue life analysis of the transplanter frame, providing good reference significance to the following similar fatigue life estimation of riding transplanters. |
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