Tooth deflection under cyclic loading
5.5 Dynamic Performance of Multi Crack Gear
(a) 20 s (b) 60 s
(c) 1000 s (d) just stop
Figure 5.19 The contour of thermograph of the multiple (3) crack gear pair after (a) 20 s, (b) 60 s, (c) 1000 s and (d) just brought to rest, speed 1800 rpm
(a) 20 s
(b) 60 s
(c) 1000 s
(d) just stop
Figure 5.20 The contour of thermograph of the multiple (3) cracks gear pair for 2500 rpm after (a) 20 s, (b) 60 s, (c) 1000 s, (d) just brought to rest, speed 2500 rpm
Chapter 5 Dynamic Performance Evaluation…
It is observed that the induced crack does not affect significantly in variation of flank surface temperature of the test gears.
5.5.1 Performance Analysis along Transverse Direction
Similar results are also obtained along the transverse direction of the gear pair during running where data are accumulated at tooth meshing region. The test results with a speed of 1800 rpm are shown in the Figure 5.21. The contours of thermograph of the corresponding experiment have been shown in the Figures 5.22 to 5.24. It is clearly to be observed that the minimum and maximum temperature rise is close to each other. The reason behind this is the small mesh region of the gear pair selected, where in longitudinal direction, the temperature is measured throughout the gear tooth taking a comparatively bigger rectangular region. It is, further, to be noticed that the rectangular region is selected in the meshing region, exhibits uniform temperature variation. As shown in the previous results, it is found that the threshold speed of the gear is 1800 rpm when load is applied 13.5N and surface temperature raised approximately 34ºC. Beyond this speed, the surface temperature of the gear is increased dramatically, and observed to be around 52ºC for test speed of 2500 rpm.
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Figure 5.21 10% cement reinforced composite driver-and driven intact gear teeth mesh along transverse direction with 1800 rpm
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(a) 20 s (b) 60 s
(c) 1000 s (d) just stop
Figure 5.22 The contour of thermograph of the intact gear pair after (a) 20 s, (b) 60 s, (c) 1000 s and (d) just brought to rest, speed 1800 rpm
(a) 20 s (b) 60 s
(c) 1000 s (d) just stop
Figure 5.23 The contour of thermograph of the single crack gear pair after (a) 20 s, (b) 60 s, (c) 1000 s and (d) just stop at 1800 rpm
Chapter 5 Dynamic Performance Evaluation…
The highest and lowest surface temperature of the gear pair for a single revolution is occurred across the face width of the gear during the test. In the Figure 5.24(e), corresponding to the revolution of the gear, highest and lowest surface temperature can be found. The experimental results are shown for the 10% cement reinforced gear under a load of 13.5N and speed of 1800 rpm. The right one is driver gear that runs clockwise and left one is the driven gear runs in anticlockwise. Referring, 0º is the mesh point of the gear pair, the contact flanks surfaces of the driver and driven gears, measurements are taken at a location of 180º on the driven gear after mesh point and 0º for both driver and driven gear. Similarly, for non- contacting flanks surfaces, measurementsare taken at a location of 270º after the mesh point for the driven and 90º for the driver gear. The surface temperature of non-contacting gear flank is measured to be around 28.8ºC (i.e. corresponding to 270º revolution for driven gear and 90º for driver gear after the reference mesh point) which is 5.2ºC lower than the contact flank surface temperature i.e. 34ºC (corresponding to 180º revolution for driven and 0º revolution for both the driver and driven gear). This surface temperature can be found little different when the cracks takes place at the root of the gear tooth. However, huge difference can be observed when the speed of the gear pair is higher as example, 2500 rpm. This analysis has been quantified as per the literature reported by Mao, (2007).
(a) 20 s (b) 60 s
(c) 1000 s (d) just stop
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180º 270º 90º 0º
Lowest (28.8ºC) Lowest (29.7ºC) Highest (34.0ºC)
Lowest (28.5ºC)
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Highest (33.0ºC)
Highest (33.4ºC)
(e)
Figure 5.24 The contour of thermograph of the multiple crack gear pair after (a) 20s, (b) 60 s, (c) 1000 s,(d) just stop at 1800 rpm and (e) highest and lowest temperature position
Table 5.1 shows the surface temperature rise under variable speeds and loads with inbuilt cracks. It is observed that average surface temperature increases with load and speed. In the present study, it is observed that the location and depth of cracks on the driver and driven gears do not have significant affect on the gear performance compared with the intact gear.
However, it is expected that multiple cracks of variable depths and locations on gear tooth could affect the material performance and further with associated heat emission rise, owing to high speed and loading condition may ultimately lead to failure of the gear. It is also observed that the surface temperature rises more prominently at the flanks surface of the gear
Chapter 5 Dynamic Performance Evaluation…
tooth. The reason behind this is more friction takes place at the flanks surface due to its bulging of the flanks compared to the edge of the tooth.
Table 5.1 Maximum surface temperature in different variables and comparison
Speeds (rpm) 8.5N 13.5N
Intact Single crack Multiple crack Intact Single crack Multiple crack
600 29.0ºC 29.0ºC 29.0ºC 29.0ºC 29.5ºC 30.0ºC
1200 29.5ºC 29.5ºC 30.0ºC 30.5ºC 31.0ºC 31.0ºC
1800 31.2ºC 31.5ºC 31.5ºC 34.0ºC 34.6ºC 36.5ºC
2500 45.8ºC 46.1ºC 46.3ºC 52.0ºC 52.0ºC 52.8ºC
The surface temperature of the cement reinforced polypropylene composite material gear and other gears have been compared and tabulated in the chapter 4. As the results presented and discussed in the Table 4.5 in chapter 4, and correlating with the results given in the Table 5.1, it is observed that the polypropylene and Portland pozzolana cement particles are the cheapest matrix and reinforcing material respectively. In addition, the other advantages of this material such as low melting temperature of the matrix, reasonable mechanical properties, low density, recyclability and other superior characteristics conglomerate core interest in lieu of the metallic gears. Hence, 10 wt% cement filled composite gear is suggested for automotive industrial application and is suitable within the operating speed of 1800 rpm and applied load up to 13.5N.