A new approach for the optimization of the thermo-mechanical behaviour of dry-running clutches using fibre-optic sensing technology with high spatial measurement density

Measuring temperature in tribological contacts remains being a huge challenge. The present paper proposes a new approach to analyze and optimize the thermo-mechanical behaviour of a dry-running clutch without affecting the real interacting surfaces. Using fibre-optic sensing technology makes it possible to gain a very detailed view of temperature distribution in the system. The interpretation of the measurements for different load situations has shown that the behaviour in the first 0.8 s is very similar. But after 0.8 s slip-time, the temperature distribution varies considerably according to the load situations. This behaviour is linked to the clutch engagement parameters and the resulting slip time. Non-lubricated clutches are still subject to numerous investigations in order to determine their dynamic behaviour, especially the dynamic behaviour. Measuring the temperature distribution in the friction contact would deliver a more detailed view of the live friction process. Main restriction remaining to establish this information is the low spatial measurement density of conventional thermal measurement facilities. On this account, fibre-optic sensing technology has been used at the IPEK to measure the temperature distribution with high spatial resolution in a pressure plate of a clutch system. One sensing fibre offers not less than 700 measurement points, divided across 28 measurement sections belonging to the pressure plate. In addition to the very high spatial measurement density, there are two more advantages. Through the low thermal mass of the optical fibre, fast variations of the temperature can be measured. By using only one sensing fibre, with a low capacity to transfer heat in itself, the heat dissipation through the sensor is very low. By means of this measurement method, it is possible to analyze the thermo-mechanical behaviour of a friction system with a high level of details. This method enables the control of temperature distribution in the counter plate. This parameter is an indicator of the load capacity of the system as an optimal homogenization leads to the elimination of local temperature peaks and so to wear reduction. Another topic is the specific adaptation of a system to its working area. The investigation of the influence on the thermo-mechanical behaviour of parameters such as friction energy or power allows the system to be optimally designed regarding to its working area. Another field of application is the validation of the thermal CAE-models.