基于随机森林回归的管状带式输送机用托辊优化设计

在管状带式输送机运输过程中,托辊在圆管带的接触载荷激励下会产生振动噪声,这是管状带式输送机运输过程中的主要噪声源。托辊参数的优化设计,对于管状带式输送机整体的减振降噪具有重要意义。为此,以托辊为优化对象,对托辊在不同结构参数下的振动特性和噪声规律进行了研究,提出了一种基于随机森林回归(RFR)的管状带式输送机用托辊参数优化设计方法。首先,对托辊进行了模态分析,得到了托辊的振动特性,确定了托辊的优化方向;基于有限元-边界元混合声场仿真方法,以现场采集的托辊受力频谱作为激励,探究了托辊在不同结构参数影响下的振动噪声及规律;然后,开发了基于RFR算法的机器学习模型,建立了托辊结构参数与噪声值之间的设计数据库,结合约束条件,得到了托辊参数的最优解;最后,针对优化后的托辊结构进行了仿真分析。研究结果表明,当托辊的直径为152 mm、厚度为6 mm、材料为普通钢、轴径为30 mm时,取得最优解,优化托辊产生的振动噪声较原托辊降低了约13.4 dB;通过托辊的优化设计,可以为管状带式输送机整体减振降噪提供参考。

Theoretical and Experimental Research of High-Static-Low Dynamic Torsional Vibration Isolator for Ship Shafting

High-static-low-dynamic stiffness (HSLDS) vibration isolators have been demonstrated to be an effective means of attenuating low-frequency vibrations, and may be utilized for ship shafting applications to mitigate torsional vibration. This paper presents the construction of a highly compact HSLDS torsional vibration isolator by connecting positive and negative stiffness components in paral lel. Based on mechanical model analysis, the restoring torque of negative stiffness components is de rived from their springs and connecting rods, while that of positive stiffness components is obtained through their circular section flexible rods. The quasizero stiffness characteristics of the HSLDS iso lator are achieved through a combination of static structural simulation and experimental test. The tor sional vibration isolation performance is assessed by means of numerical simulation and theory analy sis. Finally, the frequency-sweep vibration test is conducted. The test results indicate that the HSLDS torsional vibration isolator exhibits superior low-frequency isolation performance compared to its linear counterpart, rendering it a promising solution for mitigating low-frequency torsional vi bration in ship shafting.

基于颗粒阻尼的矿用自卸车振动舒适性

采用颗粒阻尼技术对驾驶室座椅进行减振,提高其振动舒适性;选择与驾驶室底板和座椅连接的基座作为颗粒阻尼器,建立了基座阻尼器的离散元模型;模拟整车在发动机最高转速下的振动环境,针对不同阻尼器方案(颗粒材质、阻尼器分层数、颗粒粒径和颗粒填充率),通过离散元仿真计算逐一进行耗能分析,得到了最优方案;对实物模型进行试验,对比原结构与增加阻尼颗粒后基座的加速度均方根,确认减振效果,将试验与仿真计算结果进行趋势对比,验证了离散元模型的可行性;在实际样车试验中应用最优方案,采集了座椅在发动机不同转速下的响应,进行了数据分析;针对最高转速的工况,进行了人体振动暴露的舒适性分析。研究结果表明:从频域图的单峰最大值来看,减振前座椅最大加速度响应出现在425 Hz处的0.643 4 m·s-2,安装颗粒阻尼器后最大值为25 Hz处的0.087 5 m·s-2;从时域图来看,当发动机转速分别为750、1 110、1 470、1 830、2 200 r·min-1时,安装颗粒阻尼器后座椅加速度均方根综合减幅分别达到24.2%、29.6%、34.7%、39.2%、46.0%,发动机转速越高,颗粒阻尼器的减振效果越好;安装颗粒阻尼器后各频段舒适性界限时长均有大幅度增加,频段为3.1和4.0 Hz时,安装颗粒阻尼器后舒适性界限时长均提升了1.50倍,为20 Hz时,安装颗粒阻尼器后舒适性界限时长提升了1.57倍。