The Impact of Assessing the Vibrational Energy Loss Coefficients of Multi-Purpose Machines on Occupational Safety

Abstract

Introduction. Vibration in multi-purpose drilling-milling-boring machines affects equipment reliability, production noise levels, and operator safety. Literature discusses sources of vibration, damping mechanisms, and methods for measuring vibration characteristics, while regulatory documents establish permissible levels of vibration acceleration and vibration velocity. However, the frequency dependencies of vibration energy loss factors for individual machine components, which are necessary for engineering vibration forecasting, remain insufficiently studied. The aim of this research is to evaluate vibration energy loss factors in the components of multi-purpose drilling-milling-boring machines and analyze their effect on the level of vibration affecting the operator, thereby substantiating measures to improve occupational safety. The objectives included conducting octave-band measurements, performing regression analysis of the data, and selecting relationships with the lowest standard deviation. Materials and Methods . This study utilized an integrated approach combining experimental measurements and mathematical data processing methods. Experiments were conducted on a dedicated test bench and directly on the machine using a torque hammer to excite vibrations. Vibration acceleration was recorded in octave frequency bands using modern measuring equipment. Vibrational energy loss coefficients (η) were calculated using a modified formula that took into account vibration acceleration levels. To summarize the experimental data and construct predictive models, regression analysis was used, including approximation by nonlinear functions and polynomials of varying degrees. The quality of the approximation was assessed using the minimum standard deviation criterion. Results. It was experimentally established that the loss coefficients for cast iron housing parts in the frequency range from 125 to 8000 Hz varied within the range of (7.8–8.8) ·10 –3 , demonstrating a weak frequency dependence. For engineering calculations, constant value of η ≈ 8·10 –3 could be adopted. Regression analysis revealed that the best approximating relationship for the gearbox housing was a sixth-order polynomial. Specific relationships were obtained for the cutting units: for boring and drilling, the best fit was provided by a seventh-order polynomial, and for the milling unit, by a fifth-order polynomial. The resulting mathematical models accurately described the behavior of loss coefficients within the studied frequency range. Discussion. The analysis of the results confirmed that the dissipative properties of machine structural elements were not constant and depended significantly on the type of technological operation and frequency range. The identified analytical relationships allowed us to move from point estimates at fixed frequencies to continuous energy loss prediction, which was critical for analyzing the dynamic behavior of the machine at its natural frequencies. This opens up opportunities for targeted design. Knowing the frequency spectrum of the most hazardous vibration modes, we can optimize damping specifically in these areas. For example, we can select materials with increased internal friction, or use composite vibration-absorbing coatings in specific structural areas. Conclusion. This study provides tools for quantitative assessment of vibrational energy loss coefficients for the main vibration sources in multi-purpose machine tools. The potential practical significance of this work lies in the possibility of using the derived regression relationships to develop active and passive vibration control algorithms, design damping systems, and select materials. Implementation of these findings will reduce noise and vibration levels in work areas, minimize the risk of occupational illnesses for operators, and improve overall occupational safety. Additionally, it will extend equipment life by reducing the vibration loads on components. The practical significance of this work lies in its potential for use in developing vibration control algorithms, which will significantly reduce noise levels in work areas.