Development of spring torsion bar type negative stiffness damping device and applied research

Mini-tiller is the most commonly used machine for agricultural production in hilly areas of our country the traditional micro-tiller will produce strong vibration during the working process, which will cause physical injury to the operator while reducing the reliability of the micro-tiller. In response to this problem, a technical solution for arranging a spring torsion bar type negative stiffness vibration damping device on the tiller was proposed, and a spring torsion bar type vibration damping device with stable mechanical performance, economical and practical, and negative stiffness characteristics was developed. A mathematical model of the vibration source of the micro-tiller was established to analyze the vibration parameters of the micro-tiller. On this basis, SolidWorks is used to carry out three-dimensional modeling of the tiller and the vibration reduction device, and Adams is used for vibration simulation analysis. The vibration parameter curve before and after the addition of the vibration reduction device at the handle of the tiller is collected and mathematically analyzed. The results show that the spring torsion bar type negative stiffness damping device has a good damping effect, and the damping rate for displacement in the x, y, and z directions are all above 30%.

Vibration transmission simulation model of a seated vehicle passenger

The paper presents development of vertical vibration simulation for a seated passenger in a moving vehicle is resulting from the bounce effect of the vehicle under various conditions. Although extensive research has been conducted in this field of study, the existing analysis were conducted on either the suspension of vehicle or the human body and not both. In this paper, the simulation model consists of three sub-systems, namely, vehicle suspension, seat suspension and human body model in which the vertical vibration is transmitted. By incorporating these sub-systems into the simulation, a correlation between mechanical and biological aspects can be formed between the three sub-systems. The transmission of vertical vibration in the validated simulation model provides a more realistic approach which can result to a better comparison to the real-life scenario. Parametric analysis of passive suspension system shows that lower mass ratio, higher stiffness ratio and lower damping coefficient results in better ride comfort. The incorporation of variable damper into the suspension system shows significant improvement in settling time, peak displacement and velocity, lesser discomfort rating and higher safety in passenger body.

Characteristics Analysis of Fluid-Structure Coupling Vibration of spray bar for High gap sprayer

With the progressive improvement of the level of mechanization of agricultural production, the high-gap rod sprayer has gradually become an important component of agricultural production equipment. The stability of spray rod has an important influence on the life and operation quality of spray rod. Therefore, considering the stability of the spray rod of high gap sprayer, a fluid-solid coupling vibration simulation model of the spray rod of high gap sprayer is established in this paper. The influence of inlet velocity, inlet pressure, fluid density and fluid viscosity on the flow rate and dynamic pressure in the pipe was analyzed by fluent. The results show that the exit velocity increases with the increase of the inlet velocity, but when the velocity reaches a certain value, backflow occurs. With the increase of inlet pressure, the dynamic pressure increases, and the local energy loss and the energy loss along the path also increase. The velocity and dynamic pressure decrease with increasing density.

Modeling, calculation, and analysis of torsional vibration characteristics of the hydrodynamic transmission system in engineering vehicle

According to the typical working conditions of a loader and considering the complexity of the working conditions, the hydrodynamic transmission powertrain system was modeled in this study. Because the hydrodynamic torque converter is a flexible fluid transmission component in the transmission system, this study proposes and establishes equivalent variable damping and equivalent variable stiffness models of the hydrodynamic torque converter. Based on this, a torsional vibration simulation model of the loader with variable damping and stiffness is proposed, and the frequencies and amplitudes of the torsional resonance modes of the transmission system varying with engine speed and hydrodynamic torque converter speed ratio are obtained. It is determined that the variable stiffness of the hydrodynamic torque converter has little effect on the natural frequency of the vehicle, and taking variable damping and stiffness as input, the natural frequency and resonance points of the transmission system can be calculated more accurately. The simulation modeling and calculation approach are experimentally verified, and the simulation results are valid and closer to the real resonance.

Experimental Comparison of Field and Accelerated Random Vertical Vibration Levels of Stacked Packages for Small Parcel Delivery Shipments

In the last decade, there has been a significant increase in parcel delivery shipments all over the world due to online stores and consumer demand to receive the products in a shorter period of time. It is especially true when situations like COVID-19 limits personal purchases in shopping malls as well as grocery and pharmaceutical stores. This often means that courier operators try to deliver packages utilizing vehicles with racks or shelves, which during the COVID-19 epidemic are not there anymore. This study measured the vertical vibration levels that occur in stacked parcels during express delivery versus the simulation technique in the laboratory. The goal of this paper was to measure and compare the vibration levels between laboratory practice and field transportation. For the measurement a three-layer stacked unit was built to observe the vibration levels on different road conditions in a parcel delivery vehicle and ASTM vibration profile (ASTM International). Then the measured acceleration-time data were analyzed in terms of power spectral densities (PSD) and the presented statistical data provided an understanding of the variability of intensity in different levels in stacked unit. The results showed that the vibration level increases in the stacked load upwards and with worse road conditions, but even in the worst case it did not reach those vibration levels that the laboratory test showed. Moreover, the layers of the stacked unit are in out-of-phase motion in the field, while the stacked unit in the vibration simulation usually is in-phase motion. Results indicate that the proposed vibration simulation does not correlate well with typical field vibration. This is fundamentally true as during a forced vibration created by a single-axis shaker, do not account for additional inputs occurring simultaneously creating an off-balance to the loads and as a result are less severe than simulated conditions. These findings are limited to single axis vibration simulation and unsecured loads.