The Reliability/CD Step Stress Pattern.jmp data table contains a column called Pattern ID that identifies four different stress patterns. The stress level at a particular step is the ratio of Voltage to Thickness. (Note that these two columns are hidden.) Thickness is held constant for each stress pattern. However, Voltage is set to different levels and increases within each pattern.
The Reliability/CD Step Stress.jmp data table contains the time to failure data.
1.
Select Help > Sample Data Library and open Reliability/CD Step Stress.jmp and Reliability/CD Step Stress Pattern.jmp.
The Time column gives the failure times.
The Pattern ID column identifies the stress pattern.
The Censor column indicates whether the failure time is exact or censored.
The CD Step Stress Pattern table contains the four stress patterns (identified as 1 through 4). The levels of the stress factor, Stress, are varied within each value of the Pattern ID column. The Duration column represents how many time units a particular level of the stress factor lasted.
2.
Select Analyze > Reliability and Survival > Cumulative Damage.
3.
Click Select Table in the Time-to-Event panel.
4.
Select CD Step Stress and click OK.
The columns from this table now populate the Select Columns list in the Time-to-Event panel.
5.
Select Time and click Time to Event.
6.
Select Censor and click Censor.
7.
Select Pattern ID for Pattern ID.
8.
Click Select Table in the Stress Pattern panel.
9.
Select CD Step Stress Pattern and click OK.
The columns from this table now populate the Select Columns list in the Stress Pattern panel.
10.
Select Duration and click Stress Duration.
11.
Select Stress and click Stress.
12.
Select Pattern ID and click Pattern ID.
13.
Figure 4.2 Event Plot and Stress Patterns Plot
Figure 4.2 shows the initial report that contains the Event Plot and a plot of the defined stress patterns. All four stress patterns increase the stress level quickly over the first 40 time units, after which they increase at much different rates.
14.
Select Fit All from the Cumulative Damage red triangle menu.
Figure 4.3 Model List Report
Figure 4.3 shows the Model List report. From this report, you determine that the best fitting distribution is the Exponential distribution.
17.
Figure 4.4 Distribution Profiler for Exponential Distribution at Specified Settings
Figure 4.4 shows that the predicted probability of failure for a test unit under constant stress of 0.75 at 10000 time units is 0.007233, with a 95% confidence interval of 0.00137 to 0.03776.

Help created on 7/12/2018