Report Example: Energy and Temperature Analysis in Grinding

The energy partition ratio is the amount of grinding power absorbed by the workpiece in the contact area (Mills, B. 1997, 1084).

1R=(asVsawVw)12lslw+1=(1.4710-5330001.1510-683.333)120.5553.7+11R=1.7241R=0.58ec*=thm*(leawVw)12lw(0.887Ra)ec*=523(2.641.4710-583.333106)1253.71030.8870.580.0196=129.3J/mm3

Table 1 Experimental Specific Energy

Workpiece No. Experimental specific energy (Us)J/mm3

1 169.99

2 137.72

3 121.55

4 108.11

5 103.42

6 98.19

7 96.48

8 93.89

9 93.42

10 91.94

11 98.26

12 87.41

13 99.28

14 81.22

15 159.33

Table 2

Theoretical Critical Specific Energy

Workpiece No. Theoretical critical specific energy

1 129.3

2 129.3

3 132.7

4 131.5

5 135.78

6 132.7

7 135.24

8 136.46

9 136.95

10 138.47

11 138.69

12 141.53

13 141.98

14 142.57

15 142.57

Table 3

Workpiece no. Workpiece Speed mm/s Experimental critical specific energy Theoretical critical specific energy

1 83.333 169.99 129.3

2 83.333 137.72 129.3

3 100 121.55 132.7

4 116.667 108.11 131.5

5 133.333 103.42 135.78

6 150 98.19 132.7

7 166.667 96.48 135.24

8 183.333 93.89 136.46

9 200 93.42 136.95

10 216.667 91.94 138.47

11 233.333 98.26 138.69

12 250 87.41 141.53

13 283.33 99.28 141.98

14 316.667 81.22 142.57

15 316.667 159.33 142.57

Graph 1 A graph of Critical Specific Energy against the workpiece speed

Discussion

The thermal model predicts the mean energy that the thermal damage or burn occurs. From the graph and data samples, it is evident that certain high workpiece speeds and optimum wheel speed help avoid thermal damage. The theoretical critical specific energy graph is almost linear and increases with the increase in workpiece speed. As seen in the figure, it is clear that the experimental critical specific energy value points past the theoretical critical specific energy value point trendline represent thermal damage. On the other hand, the values below the theoretical critical specific energy mean that there was no thermal damage.

From the experimental data and calculations, the case of dressing the grinding wheel shows a significant variation of critical specific energy. The critical specific energy required to grind material changes with the dressing of the grinding wheel. One reason for this phenomenon is that an undressed grinding wheel clogs its pores with time, and thus become ineffective.

A major cause of experimental error experienced here is the systematic error such as rounding off and truncating the values obtained in the process of calculation, improper calibration of measuring instruments. Another possible cause of error is the reading of measurements especially workpiece length and wheel diameter. Temperature changes during the experiment is another likely source of errors. It is well known that high temperatures affect the recording instruments and physical and chemical properties of materials. Prolonged usage of the grinding machine could lead to systematic errors. Assumptions of specific parameters and values also point to the possibility of errors though they are negligible. The thermal model does not take into account the effects of the type of lubricants used in the process of grinding. However, studies show that the effects are negligible hence would not have adverse effects on the final results.

An alternative machining process to grinding could be hard turning, though it is more of a pre-grinding process (Koepfer, 2010). Another option would be the introduction of a sensor-type device that can control the grinding process. The device would then manage the whole process thus help in minimizing thermal damage and in the long run, would be cost-effective.

In conclusion, from the experiment, calculation of the values of theoretical critical specific energy and experimental critical specific energy is possible. The graph helps to show which temperatures and speeds would result in thermal damage or burn. The thermal model is thus efficient in the estimation of the thermal damage speeds and temperatures.

References

Koepfer, C. (2010). Hard Turning as an Alternative to Grinding. [online] Productionmachining.com. Available at: https://www.productionmachining.com/articles/hard-turning-as-an-alternative-to-grinding [Accessed 8 Dec. 2017].

Rowe W., B. (2009). Principles of Modern Grinding Technology. [online] Abrasiveengineering.com. Available at: http://www.abrasiveengineering.com/bkrowe.html [Accessed 8 Dec. 2017].

Rowe, W., Morgan, M., Batako, A. and Jin, T. (2003). Energy and Temperature analysis in grinding. 44th ed. [ebook] WIT Press, pp.5-18. Available at: https://www.witpress.com/Secure/elibrary/papers/LAMDAMAP03/LAMDAMAP03001FU.pdf [Accessed 8 Dec. 2017].

Sullivan, J. (2000). Choosing The Right Grinding Wheel. [online] Mmsonline.com. Available at: https://www.mmsonline.com/articles/choosing-the-right-grinding-wheel [Accessed 8 Dec. 2017].