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Forage crushers are used to process forage into soft filaments to improve the feeding intake rate of the forage and livestock digestibility. High failure rate and low reliability of the whole machine during forage-crushing operations are a concern. To improve the reliability of crushers, the Bayesian network model was applied to evaluate the reliability of forage crushers and clarify the root cause of forage crushers failure. Multi-Island genetic algorithm was used for multi-objective optimization according to the main causes of crusher failures. The study revealed that the main causes of the failures of forage crushers were resonance caused by uneven wear of hammers, the insufficient fatigue strength of throwing blades or hammers, and wear failure of the hammers. After optimization, the reliability of the forage crusher increased from 0.739 to 0.912, which satisfied the reliability requirements of forage crushers. This study can provide a reference for the fault maintenance and reliability optimization design of forage crushers. [ABSTRACT FROM AUTHOR]

In order to predict the radiation noise of the vibrating shell of the straw crusher in the design phase, the computational fluid dynamics–discrete element coupling method is initially used to simulate the airflow–straw coupled flow field in the straw crusher, and the pulsating pressure generated by the coupled flow field is applied to the inner surface of the shell of the crusher. Then, the harmonic response of the shell is analyzed, and its results are used to be the acoustic boundary condition. Finally, the finite element and acoustic boundary element combined test methods are used to predict vibration noise of the straw crusher shell. The results indicate that the produced vibration noise of the straw crusher shell changes as the excitation frequency of the rotor rotation changes. The maximum vibration noise is achieved at the excitation fundamental frequency, and radiation noises at the harmonic frequencies decrease as the frequency increases. The simulated value of the sound pressure level of each measuring point at the excitation fundamental frequency and harmonic frequencies is basically the same as those of the experiment. Moreover, it is found that the maximum difference between the simulated and experimental value of measuring points is 1.69 dB(A). Therefore, it is concluded that the numerical model of the vibration radiation noise is accurate. The vibration noise of the shell at the inlet is the largest, and the main noise source of the vibration radiation noise is the dipole sound source of the rotating hammer rotor. The corresponding design method provides the reference for the low-noise design of straw crushers. [ABSTRACT FROM AUTHOR]

An impeller blower is one of the major aerodynamic noise sources in straw threshing machines. To reduce its aerodynamic noise, it is essential to understand the mechanism of gas-material-coupled unsteady flow causing aerodynamic noise. However, it is difficult to clarify the mechanism through measurement. Therefore, the following topics are studied in this article. First, a full-field transient numerical simulation of the gas and solid particulates' unsteady flow inside the impeller blower was carried out using a dense discrete phase model and a large eddy simulation turbulence model. Second, based on the Ffowcs Williams–Hawkins equation, the aerodynamic noise of the impeller blower of the straw threshing machines was numerically calculated. Finally, the numerical results were verified by aerodynamic noise test. The results indicate that (1) sound pressure level at the inlet of the impeller blower is the highest, mainly at 100 Hz, which is the fundamental frequency of the rotating impeller, while the sound pressure level at the fourth harmonic frequency of 400 Hz is the main source of the outlet. The total sound pressure level at the inlet is greater than that at the outlet. It is concluded that the dipole source of the rotating impeller is the main noise source, which was generated by the interaction of blade with the air and material as the impeller rotated. Also, acoustic attenuation, acoustic resonance, and impact noise of material and machinery play important roles in aerodynamic noise distribution. (2) The test and simulation results show good agreement, so the numerical model of aerodynamic noise is reliable. This study will provide a reference for the structural and acoustic optimization design of impeller blowers and their integration into threshing machines. [ABSTRACT FROM AUTHOR]

Eccentric telescopic rod conveyors are used to convey straw from chain conveyors to the feeding and compression mechanism of the 4FZ-2000A type self-propelled straw harvesting baler. As the main working component, the telescopic rod endures higher dynamic loads while conveying the straw. This will make the telescopic rod prone to fatigue fracture. Therefore, it is necessary to find a feasible model that can accurately estimate the fatigue reliability life of the telescopic rod. In order to ensure the safe working of the eccentric telescopic rod conveyer, a mechanical model of the main bearing parts of the telescopic rod is established, and virtual prototype technology is used to obtain the work load spectrum borne by the telescopic rod. Static analysis of the telescopic rod using the finite element method shows that the telescopic rod experiences multi-axial stress fatigue, and the critical section is determined. The S-N curve equation of the structure modified by the surface mass and stress gradient, critical plane approach, Miner's cumulative fatigue linear damage model, and Gaussian normal distribution model of fatigue life are used to estimate the fatigue life of the telescopic rod. In order to predict the fatigue life of the telescopic rod accurately, fatigue reliability lives are calculated with and without consideration of the strength degradation. The results show that: (1) the fatigue life prediction without considering the strength degradation is far different from practical experience; the results obtained after considering the strength degradation are more conservative and more consistent with the actual fatigue lives. The prediction results are more accurate. (2) When the strength degradation is considered, the modified Gerber correction method is more accurate than the Goodman correction method. The results of this study can provide a reference for the fatigue reliability analysis and optimization of eccentric telescopic rod conveyors. [ABSTRACT FROM AUTHOR]

Impeller blowers are used to convey materials for various forage harvesters. As the main working component, the throwing impeller endures various static and dynamic loads while conveying the materials. This makes the throwing impeller prone to fatigue fracture, so it is very necessary to find a feasible model to estimate the fatigue life of the throwing impeller accurately. In order to obtain the accurate random cyclic load applied on the high-speed rotating impeller, the finite element analysis and the fluid-solid coupling method are adopted to calculate the stress distribution of the impeller under the combined action of the fluid-solid coupling flow field pressure, the centrifugal force, and the gravity. At the same time, the stress on the dangerous section of the impeller is measured by using the DH5909 wireless strain testing system and is compared with the calculated one. The contrast results show that the numerical calculation results are reliable. To accurately predict the fatigue life of the throwing impeller at the design stage, the two-parameter nominal stress model is deduced and combined with the linear cumulative damage model of Miner and the lognormal distribution model. Its two parameters of the average stress Sm and the stress amplitude Sa can be obtained through finite element analysis and do not have to be equivalent to a symmetrical cyclic load. Therefore, its precision of estimating the fatigue life is improved. By contrasting the rated and predicted fatigue lives of an impeller, it was found that the impeller's actual rated lives are closer to the predicted lives of the Goodman and Gerber twoparameter nominal stress model than those of the conventional S-N curve. In particular, they are closer to the calculation results of the Gerber-type two-parameter nominal stress model. This shows that the Gerber-type two-parameter nominal stress model is more accurate and suitable to predict the fatigue life of the throwing impeller. These achievements will play a significant role in further optimizing the impeller and improving its reliability. [ABSTRACT FROM AUTHOR]