Item FR Calculation

FR calculation should be performed only for the lowest (component) level of product tree elements. Assembly FR will be calculated then as a sum of failure rates of underlying components.

There is a number of ways to calculate components Failure Rate:

1. Performing reliability prediction using one from more than 30 reliability prediction methods (such as MIL-HDBK-217, Telcordia, Siemens, FIDES, NPRD-95 etc.)

2. Specifying (manually or importing) fixed Failure Rate received from manufacturer or from field use failure statistics.

3. Specifying known Failure Rates for known temperatures and environments (using the GPRD library)

4. Allocating failure rates from assemblies down to the components (assign a required FR to an assembly and have RAM Commander allocate the required FR to each of its children)

See next paragraphs for more information about each of these methods.

For any of these methods, you will need to open item data screen and switch to Operating or Non-Operating tab.

To open the item data screen in Operating or Non-Operating mode:

1.	Open the product tree view.

2.	Navigate to the desired item and select it.

3.	Double-click the item if it is component or right-click it and choose "Edit" from the popup menu.

4.	Item data screen will appear.

5.	Switch to Operating or Non-Operating tab:

Rel_CC2_Data

You will see the following fields there:

Field	Description
Family	Component family - Electronic, Mechanical or Electro-Mechanical. Leave "---" for assembly.
Item type	Component Item type, like resistor, capacitor or spring. Each family has its own list of Item types.
Ref.Des.	Reference Designator
Part Number	Part Number
Quantity	Quantity of components in the current assembly
Environment	Item environment (see Top item definition for list of environments)
Cur. Environment	Current environment (set to parent’s environment if "---" set in Environment field)
Delta/Fixed temperature	Type of ambient temperature. If Fixed temp. is set, the item’s temperature is equal to the value entered in the adjacent °C field. If Delta Temp, the item’s temperature is equal to the value in the adjacent °C field plus the parent’s temperature.
Temperature	Temperature in oC
Cur. Temperature	Actual current temperature
Method of FR p calculation	Set default to use reliability prediction methods defined in Project Configuration ( Project Configuration ) , set "user-defined" to set specific reliability prediction method (other than default) for currently selected component.
Method	Selected reliability prediction method (MIL-217, NPRD, FIDES etc.).
Failure distribution	Failure distribution type: Exponential, Weibull, Time-independent
Source for failure rate	Source of failure rate selection - predicted, user-defined, field or allocated
FR p	Predicted (calculated) failure rate
FR u	User defined failure rate. Takes effect only if FR source is "user defined " (see above)
FR f	Failure rate from field data or from field data/FRACAS. Takes effect only if FR source is "Field" .
FR a	Allocated failure rate. Takes effect only if FR source is "Allocated". See Failure Rate Allocation
Complexity for FRa	Complexity factor for reliability allocation. This parameter is valid if you selected Allocated failure rate
Field factor	Field factor multiplier for computing item failure rate
Duty cycle	Duty cycle multiplier for computing item failure rate
Mult. factor	Multiplicative factor multiplier for computing item failure rate
Add. factor	Additive factor multiplier for computing item failure rate
Item FR	Computed failure rate value of current item. Item FR = (base FR (FR predicted, FR user-defined, FR field or FR allocated, according to FR source switch) * Field factor * Duty Cycle * Mult.Factor + Add. factor ) * Quatity.
Status - Check	Data validation status, set automatically: --- = no status Err = Error (appears as - in product tree) Warn = Warning (appears as X in product tree) O.K. = OK (appears as + in product tree)
Status - Calc	FR calculation status, set automatically: --- = no status Err = Error (appears as - in product tree) Warn = Warning (appears as X in product tree) O.K. = OK (appears as + in product tree)
Source of FR u	Description of user-defined or field Failure rate source (manufacturer data, field data, accelerated life testing data, other database etc.)
Nc	Number of on/off cycles per 1000 hrs
Cur. Nc	Current number of on/off cycles per 1000 hrs (set to parent’s Nc if ––– in Nc field)

See next paragraphs for different ways of FR definition or calculation.