CAJ | 학술논문

为降低联合收获机正常工作时的共振，该文利用UG 软件对沃得锐龙型稻麦联合收获机割台机架进行建模，求解出割台机架的模态频率和振型，并对割台机架进行模态试验验证及理论分析；在通过分析外部激振频率特点的基础上，使割台机架固有频率避开外部激振频率范围，并对机架进行结构优化与试验。试验结果表明：将割台机架横梁、弯梁厚度减少0.2 mm，底板、侧板厚度减少0.4 mm时，割台机架质量降低了14.02%，前4阶模态频率均避开了联合收获机各激励频率范围；将割台传动轴平衡配重块质量增加254.90 g，使得割台传动轴轴承座处沿联合收获机前进方向、上下方向位移振动幅值分别降低了25.70%和12.70%，并有效避免了割台共振的产生。该文的研究结果为降低联合收获机割台振动提供了设计依据。
위강저연합수획궤정상공작시적공진，해문이용UG 연건대옥득예룡형도맥연합수획궤할태궤가진행건모，구해출할태궤가적모태빈솔화진형，병대할태궤가진행모태시험험증급이론분석；재통과분석외부격진빈솔특점적기출상，사할태궤가고유빈솔피개외부격진빈솔범위，병대궤가진행결구우화여시험。시험결과표명：장할태궤가횡량、만량후도감소0.2 mm，저판、측판후도감소0.4 mm시，할태궤가질량강저료14.02%，전4계모태빈솔균피개료연합수획궤각격려빈솔범위；장할태전동축평형배중괴질량증가254.90 g，사득할태전동축축승좌처연연합수획궤전진방향、상하방향위이진동폭치분별강저료25.70%화12.70%，병유효피면료할태공진적산생。해문적연구결과위강저연합수획궤할태진동제공료설계의거。
With the rapid development of agricultural mechanization in China, the combine harvester has been applied widely in the past decade. As the critical component of the combine harvester, the Cutting table frame bears some parts, such as the blade and reel, and is subjected to the unbalanced inertial force of blade mechanism, the impact load of cutting the crop, the incentives from the engine, and other dynamic loads of road excitation. If its natural frequency is close to the frequency of the dynamic load, resonance would be produced; it will even happen to the whole header and machine. The dynamic stress produced by resonance will seriously affect the performance of the combine harvester, the service life, reliability, and human body comfort. Therefore, it is particularly important to study the vibration of the header frame. In the paper, the parametric modeling of the combine harvester Ruilong-4LZ-2.5B Cutting table frame was developed using the three-dimensional modeling software UG. After meshing, the modal parameters as well as the modal vibration shapes were calculated utilizing the NX Nastran, and the first 4 modal frequencies were 12.1, 28.96, 46.35 and 76.17 Hz respectively. In order to verify the accuracy of the modal analysis results, the laboratory modal testing the combine harvester Ruilong-4LZ-2.5B Cutting table frame was implemented by exciting vibration methods with the DH5902 dynamic analysis system. Then, experimental modal parameters were obtained, and the first 4 modal frequencies were 12.21, 29.54, 46.88 and 72.27 Hz respectively. By comparing the above results, it could be seen that the theoretical modal frequencies were close to the experimental modal frequencies (the maximum error is 5.39%) and their mode shapes were also basically the same, which verifies the correctness of the calculated results and the accuracy of the Cutting table frame finite element model. Then, the excitation frequencies of the exciting vibrations from the pavement as well as the engine, cutter bar, vibrating screen, and threshing cylinder of the combine harvester were analyzed, and the result demonstrated that the first natural frequencies of the combine harvester Cutting table frame were close to or overlapped with the above excitation frequencies, which implies the combine harvester was vulnerable to resonance in operation. Therefore, in order to improve the modal frequencies to avoid the resonance, a reasonable optimization proposal was conducted by the Global sensitivity method. The optimization results indicated that when the thickness of the every beam of the frame is reduced from 3 mm to 2.8 mm and the thickness of the floor and the side of the frame is reduced from 1.2 mm to 0.8 mm, the first 4 order modal frequencies separately are 8.85, 24.31, 40.92, and 72.96 Hz, and each of them is beyond the range of the excitation of the combine harvester, which effectively avoids the resonance. The weight of the clump weight for the transmission shaft of the header is increased by 254.90 g, the vibration amplitude of the bearing block of the transmission shaft along the advancing direction of the combine harvester is reduced 0.691 mm, and the up-and down vibration amplitude is reduced 0.216 mm. This research provides references for the design and improvement of the header structure of the combine harvester.