The materials laboratory that you direct received the following data on the tensile strength in MPa of 15 samples of Aluminum Nitride. The data obtained for each sample are: Sample Endurance (Mpa) SAMPLE (STRENGTH) MPa 1 190 2 233 3 268 4 160 5 257 6 300 7 310 8 262 9 185 10 205 11 275 12 245 13 220 14 290 15 228 You are asked to calculate the Weibull modulus, m, considering that the probability of failure is n/16, where n is the number of specimens that failed at a given stress. You can use Excel to speed up the calculations.
Design Against Fluctuating Loads
Machine elements are subjected to varieties of loads, some components are subjected to static loads, while some machine components are subjected to fluctuating loads, whose load magnitude tends to fluctuate. The components of a machine, when rotating at a high speed, are subjected to a high degree of load, which fluctuates from a high value to a low value. For the machine elements under the action of static loads, static failure theories are applied to know the safe and hazardous working conditions and regions. However, most of the machine elements are subjected to variable or fluctuating stresses, due to the nature of load that fluctuates from high magnitude to low magnitude. Also, the nature of the loads is repetitive. For instance, shafts, bearings, cams and followers, and so on.
Design Against Fluctuating Load
Stress is defined as force per unit area. When there is localization of huge stresses in mechanical components, due to irregularities present in components and sudden changes in cross-section is known as stress concentration. For example, groves, keyways, screw threads, oil holes, splines etc. are irregularities.
The materials laboratory that you direct received the following data on the tensile strength in MPa of 15 samples of Aluminum Nitride. The data obtained for each sample are: Sample Endurance (Mpa)
| SAMPLE | (STRENGTH) MPa |
| 1 | 190 |
| 2 | 233 |
| 3 | 268 |
| 4 | 160 |
| 5 | 257 |
| 6 | 300 |
| 7 | 310 |
| 8 | 262 |
| 9 | 185 |
| 10 | 205 |
| 11 | 275 |
| 12 | 245 |
| 13 | 220 |
| 14 | 290 |
| 15 | 228 |
You are asked to calculate the Weibull modulus, m, considering that the probability of failure is n/16, where n is the number of specimens that failed at a given stress. You can use Excel to speed up the calculations.
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