Failure Rate Prediction User Guide

Version: 3.9.1

1 Nomenclature

Term	Definition
FRP	Failure Rate Prediction
MTTF	Mean time to failure

2 Introduction

This guide aims to provide the user with a brief overview regarding the features and functionality of the Failure Rate Prediction (FRP) editor and the analyses within.

The Failure Rate Prediction uses standardized formulas to calculate basic reliability metrics (MTTF and failure rate) for parts/components. Inputs required for the calculations are operational and design parameters of the items and their specific use cases. The workflow below describes steps required to conduct an FRP analysis.

3 MADE Failure Rate Prediction Workflow

Figure 1 ("Failure Rate Prediction Workflow") depicts "WF35: Apply Failure Rate Prediction (FRP)":

Pre-requisites:

• A. RAM Module: access to the Reliability, Availability and Maintainability Module is required to enable Failure Rate Prediction analyses.
• B. FBD Model: model items which are representation of items that qualify for Failure Rate Prediction analyses to be conducted.

Flowchart steps:

1. Access Failure Rate Prediction
2. Create FRP Analysis (fed by: Analysis Name, Description, Type)
3. Select Target Item(s)
4. Add Part
5. Define Part Details (fed by: Part Description, Quantity, Operational Factors)
6. All Parts Defined? → No: loop back to step 4 / Yes: continue
7. Apply Analysis Failure Rate / MTTF to Item(s)
8. Failure Rate Prediction Applied

Detailed Descriptions:

1. Access 'Failure Rate Prediction' (FRP) under 'Analyses' in the main menu bar.
2. Create an analysis with the 'Create a new Failure Rate analysis' button along the right-hand side of the Analysis List section. Define a name, description and type for the analysis.
3. Select the target model item(s) to which the predicted Failure Rate / MTTF will be applied. Open the dialog via the Item(s) field that reads "Select an item," and select all relevant target components and/or parts for the FRP Analysis.
4. Add part via the dialog opened with the green plus icon button on the right-hand side of the 'Part List' and select from the list.
5. Define part details that include part description, quantity and operational factors that are specific to the selected part.
6. Continue until all relevant parts and their details are defined to determine the Failure Rate / MTTF for the target model item.
7. The failure rates of defined parts are used to determine a resultant Failure Rate / MTTF which is applied to selected model items with the 'Apply Analysis MTTF to Item(s)' button.
8. Failure Rate Prediction has been performed and the result applied to the model item(s).

4 Accessing Failure Rate Prediction Editor

To access this tool, select Analyses > Failure Rate Prediction from the main menu. Note that MADE must be in the RAM module to use the FRP tool.

Figure 2 shows the Analyses menu with: Fault Tree, Response Paths (submenus), Connection Matrix, Common Mode Analysis (greyed out), Critical Item Analysis (greyed out), Criticality & Reliability Editor, Technical Budget Analysis, Failure Rate Prediction (highlighted), Markov Analysis, RBD Analysis, Reliability Allocation Editor, Back-Fit RCM (greyed out), Model-based RCM, Maintenance Cost Estimates.

5 217F Notice 2 – Electronic Reliability Prediction Standard

The FRP tool uses formulas from the 217F Notice 2 – Electronic Reliability Prediction Standard. Introduced in 1995, Notice 2 is an update of the previous 217F standard. The standard categorizes electronic parts into 19 part groupings and then further into specific part types. Each part type has a formula for predicting the part's failure rate.

MADE's implementation of the 217F Notice 2 standard facilitates the creation of analyses containing failure rate predictions that can be applied back to the MADE reliability model. Parts or components in MADE are linked to an analysis; the predicted failure rate and associated MTTF are assigned to the part or component.

6 217F Failure Rate Prediction Analysis

Overview / Management

The Failure Rate Prediction tool is run from the Overview/Management page. In this page all existing analyses are displayed along with a summary including Name, description and predicted failure rate.

To create an FRP analysis:

• Select the Create button.
• From the dialog, enter the analysis Name and Description. A Type can also be selected, however currently this is limited to only the 217F Notice 2 standard.

To create a copy of an existing analysis:

• Select an analysis from the table.
• Select the Copy button.
• The editor will automatically generate a copy of the selected FRP analysis.

To open an existing FRP analysis:

• Select an FRP analysis from the table.
• Select the Open button.
• The editor will open the FRP analysis in a new window within the FRP editor.

To delete an existing FRP analysis:

• Select an FRP analysis from the table.
• Select the Delete button.
• A pop-up dialogue will ask to confirm that the FRP analysis is deleted.
• Select 'Yes' to confirm delete.

Figure 3 ("New Failure Rate Prediction analysis dialog") shows "Create a new Failure Rate Analysis": Name field (example: "Example"), Description text area, Type dropdown = "217F Notice 2 - Electronic Reliability Prediction".

Analysis Page

Once an analysis is created and opened, it appears as a new page below the Overview/Management page. Within this page, one or more Parts can be added to the analysis. Each Part added to the analysis has a Predicted Failure Rate. If multiple Parts are added to an analysis, then the sum of all the constituent Parts' Predicted Failure Rates is taken as the analysis's Predicted Failure Rate.

To create a New Part:

• Select the New Part button.
• From the dialog, select a Part from the list and select 'OK'. Alternatively, the user can search for a Part using the filter text field.

Each Part's Predicted Failure Rate is calculated using a formula that contains a set of factors and base failure rates. Factors are indicated using the 'Pi' (π) designation; base failure rates use the 'Lambda' (λ) designation. Each factor is dependent on the user inputting some parameter(s) relating to the design of the Part (e.g. maximum voltage rating) or the operation of the Part (e.g. case temperature).

Worked Example: Diode Failure Rate (Figure 4)

Figure 4 ("Example of inputs required to generate a Predicted Failure Rate for a Diode") shows the "Part Details" panel with the following 217F Notice 2 diode failure-rate model, structured as:

λp (Diode Failure Rate) = λb × πE × πQ × πC × πS × πT

With example values entered:

Factor	Selected value	Computed factor value
Base Failure Rate — λb	General Purpose Analog	0.003800
Environment Factor — πE	GB - Ground, Benign	1.000
Quality Factor — πQ	JANTXV	0.7000
Construction Factor — πC	Metallurgically Bonded	1.000
Electrical Stress Factor — πS (Voltage Stress Ratio = 0.5)	—	0.1856
Temperature Factor — πT (Junction Temperature TJ = 35.00°C, Case Temperature = 35.00°C [Default], Environment = GB - Ground Benign, Junction to Case Thermal Resistance θJC = 70.00°C/W [Default], Package Type = blank, Device Worst Case Power Dissipation = 0.0 W)	—	1.400
Resulting Diode Failure Rate — λp	—	0.0006913

Other fields on the Part Details form: Description (free text), Quantity (default 1).

This is the concrete MIL-HDBK-217F-Notice-2-style multiplicative reliability model MADE implements for electronic parts (base rate times a product of Pi-factors for environment, quality, construction, electrical stress, and temperature) — directly reusable as a template for validating or reproducing a diode λp calculation, or for understanding the general shape of 217F Notice 2 formulas for other part types (each part type substitutes its own specific set of π-factors and λb lookup table, per the 19-part-grouping taxonomy referenced in Section 5).

Applying a Predicted Failure Rate to a Model Item

Once an analysis has a Predicted Failure Rate, it can be applied to a modelling item in the system (either a Part or Component). This writes the failure rate and MTTF of the analysis to the item for the purpose of reliability analysis.

Figure 5 ("Selection of item for application of failure rate") shows the "Failure Rate Prediction" > "Select Target Items" dialog: a tree of Vehicle System > Coupling, Driveline (Differential, Driveshaft, Half Shaft Front/Rear, Planetary Gearbox Front/Rear, Transmission, Wheel Front/Rear, Wheel Resistance Front/Rear), Power Generation (Control Unit checked, Diesel Engine > Air Filter, Coupling 1, Engine, Governor, Injector Pump, Lift Pump, Primary Fuel Filter) — each row showing an "MTTF [Hours]" column, e.g. Differential/Driveshaft/Half Shafts/Planetary Gearboxes/Transmission/Wheels = 1,000,000.00 hours; Control Unit = 14,774.00 hours; Air Filter = 5,297.51 hours; Coupling 1/Engine/Injector Pump/Lift Pump = 37,981.69 hours; Primary Fuel Filter = 469.48 hours.

Figure 6 ("Predicted Failure Rate application to item") shows the resulting "Predicted Failure Rate" panel after selecting Control Unit: Item(s) = Control Unit, Item MTTF = 14,774 hours, Analysis Failure Rate = 67.6865, Analysis MTTF = 14,774 hours, with an "Apply Analysis MTTF to Item(s)" button to write these values back onto the model item.