An Experimental Study of Contact Temperatures at Sealing Interface against Varying Shaft Surfaces

Increased temperatures at the sealing interface between the seal and shaft can reduce the work-ing life of a seal through elastomer aging, swelling and increased friction. Degradation of the seal due to increased temperatures can cause pre-mature failure, wear and leakage. There is no such thing as a perfect seal; each application has requirements to cater to the needs of each sys-tem. For radial oil seals in helicopter gearboxes, the contact temperatures at the sealing interface are a critical parameter to consider. In this manuscript, investigating the factors that influence the temperatures at the contact interface shed light on the operating parameters that cause an in-crease in contact temperatures. Four varying shaft coatings are tested against three seal spring loads for a range of sliding velocities between 5–25 ms−1 to reproduce conditions of the gearbox. The study reveals an optimum seal spring of 12 oz, with a circumferential load of 3.34 N for lowest temperatures at the interface. Higher springs of 14 oz and lower springs of 8.5 oz both cause increased temperatures at the interface. Additionally, the need for surface coatings on the shaft is re-enforced through experimental evidence demonstrated by comparing temperatures reached between a plain stainless steel shaft and three surface coated shafts. Chrome plating shafts are undesirable due to the ‘polishing’ in effect they experience. The results of this study build on this by showing that chrome plated shafts have higher temperatures at the interface, aggravating any wear or polishing in of that surface. Contact temperatures with Tungsten car-bide and Chrome oxide coatings remain within the expected temperature rise. Lastly, micro-scopically ‘rougher’ surfaces result in increased temperatures in contrast to surface coatings within the specified range of roughness as provided by DIN 3760/61/ISO 6194.

在密封件与轴之间的密封界面温度升高，可通过橡胶老化、膨胀和摩擦增加降低密封件的使用寿命。由于温度升高导致的密封件退化可引起过早失效、磨损和泄漏。完美的密封件并不存在；每种应用都需满足不同系统的需求。对于直升机变速箱中的径向油封，密封界面的接触温度是一个至关重要的参数。在本篇论文中，通过对影响接触界面温度的因素进行研究，揭示了导致接触温度升高的运行参数。通过对四种不同的轴涂层进行测试，并与三种密封弹簧负荷相结合，在5至25 ms−1的滑动速度范围内，以再现变速箱条件。研究表明，12盎司的密封弹簧在界面处达到最低温度，其周向载荷为3.34 N。14盎司的较高弹簧和8.5盎司的较低弹簧均导致界面温度升高。此外，通过将普通不锈钢轴与三种表面涂层轴的温度进行比较的实验证据，证实了轴表面涂层的需求。由于镀铬轴在‘抛光’过程中产生的效果，因此不推荐使用镀铬轴。本研究的结果在此基础上进一步表明，镀铬轴在界面处的温度较高，加剧了表面的磨损或抛光。碳化钨和氧化铬涂层的接触温度保持在预期的温度升高范围内。最后，与DIN 3760/61/ISO 6194规定的粗糙度范围内的表面涂层相比，‘微观上更为粗糙’的表面会导致温度升高。