Wednesday, July 22, 2015
OT- LUNA BLOG-Luna Innovations ODiSI platform with HD-FOS technology for temperature enables automotive engineers to expand the limits of design
When components are designed for aerospace, automotive or other general industrial applications, design factors are used to account for unknowns in the application or limitations in design validation. These design factors can come at a price in the form of excess material and cost. In cases where knowledge of the application is insufficient to determine the correct design factor, premature component failure may result. It is clear that commensurate with continued advancements in component design, advanced methods for test validation are also required to both realize a designs full potential and to mitigate the risk of pre-mature failure.
In a paper published in the Journal of Engineering Tribology titled “A new approach for the optimization of the thermo-mechanical behavior of dry-running clutches using fibre-optic sensing technology with high spatial measurement density”, authors, Kniel Jonas, Gommeringer Michael and Lorenz Benoit report the results of thermally testing a dry running friction clutch using Luna’s high definition fiber optic sensing (HD-FOS) technology. In clutch design the limiting factor determining the clutch load capacity is temperature and this temperature can vary widely both as a function of time and location across the face of the pressure plate. The variation in temperature immediately following clutch engagement is particularly dramatic due to the slip period between pressure plate and friction surface. For this reason Luna’s HD-FOS distributed sensing system adds significant value in its ability to fully characterize the thermal response of the clutch under all conditions of operation thus ensuring that any design factors used are well considered. This same level of data characterization cannot be obtained using traditional point sensing methods or other temperature sensing technologies.
Figure 1 shows instrumentation of the 200 mm diameter pressure plate with a single one meter length of a fiber sensor constructed of standard unaltered fiber optic cable. The fiber is routed through 28 bores in the pressure plate spaced equidistantly around the perimeter of the plate. This fiber sensor acquired over 700 temperature data points with a distance between measurements of only 1.28 mm. This high density data, acquired at a scanning rate of 23 Hz, provided the authors a full and complete view of the steady state and transient thermal response of the clutch plate under various loading conditions.
Figure 2 shows four full field temperature maps created using data collected by Luna’s HD-FOS system. Each map represents a different permutation of the parameters of speed, contact pressure and simulated inertia. As can be seen from the data, the temperature varies considerably as a function of the distance across the pressure plate face and as a function of time from clutch engagement. The data also shows that the characteristic of the temperature map profile is quite different depending on the combination of speed, contact pressure and simulated inertia used during each test. The data shown in figure 4 demonstrates conclusively the value that Luna’s HD-FOS technology brings to machine design and validation. No other technology can provide this same level of data density for this type of application.
In summary, Luna’s HD-FOS distributed sensing technology provides design engineers unique capabilities to optimize component designs, validate design assumptions and reduce risk of pre-mature component failure. The data shown in figure 4 show conclusively the inadequacy of design validation using only point sensing. Other temperature sensing technologies such as thermal imaging are also not feasible as the points of interest are not visible during operation and loading. In this, and similar applications, Luna’s HD-FOS distributed sensing technology and its ability to gather high density data stand alone among all other temperature sensing technologies.
To learn more about what HD-FOS can do for your testing application, click here to visit ourproduct page.
Reference: Institute of Mechanical Engineers, Journal of Engineering Tribology 0(0) I-8 – “A new approach for the optimization of the thermo-mechanical behavior of dry-running clutches using fibre-optic sensing technology with high spatial measurement density”, authors, Kniel Jonas, Gommeringer Michael and Lorenz Benoit