How can I
use ALTA to make warranty
predictions based on data from a quantitative accelerated life test?
If you have data from a quantitative accelerated life test, you can use
ReliaSoft’s ALTA software to
analyze the data in order to make estimates about the performance of the product under
normal use conditions. If you have information about the projected sales for the
product, you can take that analysis a step further and forecast the total expected
returns for future warranty periods.
- First, use one of the Standard Folios in ALTA to enter the accelerated test data
and fit a lifetime distribution and life-stress relationship model.
- Next, choose Project > Add Report to open the Report Wizard. Select your
Standard Folio in the Default Data Source field and then choose
Based on an existing
Template and select the Warranty Forecasts template that is shipped with the
software, as shown next.
- Click OK to add the report to your project. In this worksheet, you
can set the value in the Time Increment field to determine the length of the
forecasted warranty periods. You also can enter the expected sales/shipment quantity for
each period. When you have entered these values, the worksheet will automatically calculate the
expected returns in each warranty period. For example, in the following worksheet, the
time increment is set to 720 hours (i.e. approximately 3 months if the units
operate 8 hours per day). Therefore, the forecasted warranty periods are 720, 1440,
2160, 2880 and 3600 hours. The anticipated sales have been entered in the area on
the left side of the worksheet (i.e. 10,000 new units enter the population in each
period). The area on the right side of the worksheet presents the forecasted returns
from each batch of sales and the row at the bottom of the worksheet presents the
total expected returns in each warranty period. For example, in Period 3, the model
projects ~27.4 returns from the units that were shipped in the first sales period
and ~2.2 returns from the units that were shipped in the second sales period, for
a total of ~29.6 returns in Period 3.
How can I quickly apply the same
changes to the subordinate items of a block in Lambda Predict 3?
The application properties of blocks in Lambda
Predict 3, such as temperature and environment, can affect the properties of items
below them in the system hierarchy. Depending on the block’s settings, these particular properties of
the items contained in the block can change when the
block’s application parameter values are changed. This means that you can ensure that changes
made to the application parameters of, for instance, a subsystem will be applied to
all sub-subsystems and components within that subsystem.
As shown below, the Update Modes node in the Item Properties
area contains the
settings that determine how the updates are applied.
The setting of the Update Children field determines what
happens when you change the block’s properties:
- Always: All subordinate blocks and components will assume the
application parameters of that block. For MIL-HDBK-217F blocks, this also applies the
physical parameters of the block (i.e. its quality settings) to any of its
children that have the given quality type (e.g. a change to the Quality,
Capacitors parameter will affect capacitors below the block, but will not affect
coils below the block because they do not use the Quality, Capacitors parameter).
- Never: Changes made to the parameters will not be applied to any
subordinate blocks or components.
- On Matching: Changes made to a given parameter of the block will be applied
to subordinate items only if the current value of the parameter is the same for the
block and the subordinate item. For example, consider a block with an Environment
parameter of "Ground, fixed" and two subordinate items: component A
(Environment: "Ground, mobile") and component B (Environment: "Ground,
fixed"). If you change the block's Environment parameter to "Ground,
benign," component B's Environment parameter will also change to "Ground,
benign," but component A's Environment parameter will remain unchanged.
For temperature changes, the setting of the
Update Temperature Mode field determines what happens when the block’s temperature
- Absolute: The temperatures of the subordinate
blocks or components will be replaced
with the specified value.
- Increment: The specified value will be added to the current temperature
values for the subordinate blocks or components. For example, if component A has a
temperature of 50 and component B has a temperature of 60 and you enter an incremental
addition of 10, then the temperatures will change to 60 and 70, respectively.