NEWS

<p style="text-align: center;"><img src="/ueditor/php/upload/image/20260131/1769821490617463.png" title="1769821490617463.png" alt="1.png"/></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 12px;">A comparative analysis of the measured sound pressure levels for dry and grease-lubricated conditions in Steel–POM and POM–PA66 gear pairs is presented in Figure 13, with corresponding vibration levels summarized in Figure 14. While differences at the lowest tested rotational speed were relatively minor, a marked improvement in NVH performance was observed at intermediate (L3, L4) and high (L5, L6) speed levels under lubricated conditions.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 12px;">Overall, the application of grease exhibited a beneficial effect, acting as an additional damping medium within the gear tooth contact zone. This led to a reduction in impact-induced noise and vibration, as well as a suppression of stick-slip phenomena. The improved dynamic response is attributed to the lubricating film’s capacity to mitigate direct surface interactions and absorb vibratory energy during meshing. In between measured sound pressure level for dry and grease lubricated tests with Steel–POM and POM–PA66 combinations are shown in Fig. 13. Measured vibration levels are summarized in Fig. 14. While at the lowest tested rotational speed the differences were not so evident a quite significant improvement could be observed at the medium (L3, L4) and high (L5, L6) rotational speeds. In general, a beneficial impact of grease could be observed, which can be considered as an effect of an additional damping element in the contact, generating less impact noise and vibrations, while also reducing the stick-slip effect. Conclusions The study presents a comprehensive experimental assessment of the NVH performance of plastic gears in comparison to conventional steel gear pairs. The key findings are summarized as follows: Plastic gear pairs exhibited substantially better NVH characteristics than steel gears. Sound pressure levels were reduced by up to 10 dB, while vibration levels decreased by more than 50% in some cases, underscoring their potential for noise-sensitive applications. Among the tested pairs, POM–PA66+30%GF gears achieved the best NVH performance, benefiting from higher meshing stiffness and lower transmission error. In contrast, the POM–PA66 pair showed the highest vibration levels among plastic gears, linked to lower stiffness and greater transmission error. Gear wear led to a noticeable deterioration in NVH performance. Over 10 million load cycles, sound pressure levels rose by 4–6 dB, and vibration amplitudes nearly doubled, emphasizing wear as a critical determinant of long-term acoustic performance. Grease-lubricated gears consistently outperformed dry-running pairs, particularly at medium and high rotational speeds. The improvement is attributed to grease acting as a damping medium, which reduces impulsive forces and mitigates stick-slip effects. These results provide valuable guidance for gear designers and engineers in selecting suitable polymer materials and lubrication strategies to achieve superior acoustic behavior. Future research may focus on advanced wear monitoring techniques and dynamic modeling approaches to enable predictive NVH performance under real-world operating conditions.</span></p>