WF06: Create Failure Diagram

Pre-requisites

• FBD Model: contains model items defined with functions.
• SRA Module: access enables ability to edit Criticality parameters.

Detailed Descriptions (numbered steps)

1. Select a model item and access 'Failure Diagram' viewer under 'Modeling' of main menu bar or via the right-click context menu opened on the model item.
2. Select a Functional Failure Mode (FFM), to define general details and narratives, in the 'General' tab of the Properties viewer.
3. Continue to the 'Criticality' tab of the Properties viewer and edit the Criticality parameters, for both low FFM and high FFM. Complete this for all FFMs of the model item.
4. Build the failure diagram if necessary and if the physics of the failure are known.
5. Use the Failure Concepts Taxonomy Library to build Failure Diagrams, and where necessary, defining a display name and/or narrative in the 'General' tab of the Properties viewer.
6. For all faults, open 'Criticality' tab of Properties viewer and edit Criticality parameters.
7. Edit Criticality parameters for the connections between the failure concepts of the failure diagram.
8. Failure diagrams created for selected model item.

Fields referenced in the diagram

• Define FFM General Details: Display Name, Unit of Measurement, Initial Value, Internal Damping, Narratives
• Edit FFM Criticality Parameters: Difficulty of Detection, Probability/Occurrence, Severity, Is FFM a Failure?, Controllability, Probability/Exposure, Failure Mode Ratio, Failure Effect Probability
• Build Failure Diagram (Failure Concepts Taxonomy): Causes, Mechanisms, Faults, Failure Conditions, Losses/Symptoms, Display Name, Narrative
• Edit Fault Criticality Parameters: Difficulty of Detection, Probability/Occurrence, Controllability, Probability/Exposure, Failure Mode Ratio, Failure Effect Probability
• Edit Connection Criticality Parameters: Causal Probability, Progression Rate, Polarity, Causal Strength

Decision points

• Build Failure Diagram? — No → go directly to Failure Diagram Created; Yes → Build Failure Diagram (step 5) onward.

Screenshot walkthrough (captions/labels extracted)

Step 1: Access Failure Diagram viewer

• 'Modeling' menu: New Connection, New Item, New RBD Group, Activate Failure Diagram, Hazard Diagram, Functional Diagram, Mission Profile Definition, Requirements, System Environment, Unit Life Parameter, System Model, Bond Graph, Failure Diagram, Functions, RBD Model, Maintenance Actions, System Maintenance Editor, Environment Library, Sensor Library, Annotations.
• Right-click context menu on a model item (e.g. "Fuel Tank" on the "Power Generation" canvas): System Model, Failure Diagram (highlighted, tooltip "Open Failure Diagram"), Functions, Hazard Diagram, Maintenance Actions, Cut, Copy, Paste, Delete, Zoom In/Out, End Effect Item, Fault Tree, Response Paths, Hazard Path Analysis, Propagate All..., Override Failure Diagram, Failure Injection, Response Simulation, Load from Library, Save to Library, Advanced Properties.
• "Fuel Tank" failure diagram canvas showing two function panels: "Lining_Outlet" with items Lining/Outlet and FFM "Supply Liquid Static pressure (Lining_Outlet)"; "Inlet_Lining" with items Inlet/Lining and FFM "Contain Liquid Flow rate (Inlet_Lining)"; plus a top-level FFM "Provide Liquid Static pressure (Fuel Tank)".

Step 3: Define Functional Failure Mode (FFM) General Details

• "Properties" panel for "Liquid Static pressure": tabs General (selected), Narrative, Criticality, ISO 26262, MIL-STD-1629a (Quant), MIL-STD-882E. General tab fields: Name ("Static pressure"), Flow Property ("Static pressure"), Function ("Provide - Liquid (OUT)"), Unit ("psi"), Initial Value slider (0.0, range -10 to 10), Internal Damping slider (2.5, range 0-10).
• "Narrative" tab: toggle High/Low; fields "Cause Narrative" and "Response Narrative" (text areas), shown separately for High and Low FFM states.

Step 3: Edit Functional Failure Mode Criticality Parameters

• "Criticality" tab (ISO 26262 sub-tab) showing Low/High toggle. Sliders: Difficulty of Detection (6.1, labeled "Moderate"), Probability/Occurrence (4.8 Low labeled "Extremely Remote" / 8.4 High labeled "Probable"), Severity (8.7 Low labeled "Hazardous" / 5.6 High labeled "Major"). Radio "Is Failure? Yes/No".
• MIL-STD-1629a (Quant) sub-tab: Controllability (4.4 Low "Controllability 1" / 10.0 High "Controllability 3"), Probability/Exposure (8.4 Low "Probable" / 4.8 High "Extremely Remote"), Severity (5.6 Low "Major" / 8.7 High "Hazardous").
• Additional sub-tab: Failure Mode Ratio (4.56E-2 Low / 3.81E1 High, log scale 1E-4 to 1E3), Failure Effect Probability (0.87 Low / 1.00 High).
• MIL-STD-882E sub-tab: Probability (8.4 Low "Probable" / 4.8 High "Extremely Remote"), Severity (5.6 Low "Major" / 8.7 High "Hazardous"), Software Control (4.4 Low "Redundant Fault Tolerant" / 9.6 High "Autonomous").

Step 5: Build Failure Diagram

• Failure Concepts / Hazard Concept taxonomy browser panels (filterable by icon type: triangle = Cause, diamond = Mechanism, circle-slash = Fault, filled black circle = Failure Condition, filled circle = Loss/Symptom). Categories shown include:
  • Causes tree: Assembly and reassembly (Contamination, Electrical property, Environmental protection, Geometry > Blocked opening, Disconnected, Dynamic imbalance, Excessive clearances, Insufficient clearances, Loose fit, Mechanical interference, Misaligned, Tight fit, Wrong part orientation), Humidity, Material quality, Mechanical loading, Mechanical property, Design, Maintenance, Manufacturing, Operation, Transportation.
  • Mechanisms tree: Corrosion, Elastic deformation, Electrical, Fatigue (Contact fatigue, Fretting fatigue, High cycle fatigue, Impact fatigue, Low cycle fatigue, Thermal fatigue), Fracture, Material decomposition, Material degradation, Material interface, Material transfer, Plastic deformation, Software, State change, Wear.
  • Faults tree: Bulk change, Chemical connection, Chemical property, Electrical connection, Electrical property, Fluid property change, Mechanical connection, Mechanical property (Brittle, Hard, Molten, Plastic, Softened, Stiffened, Stiffness reduced, Toughened, Weakened), Operator faults, Shape change, Software, Surface change.
  • Failure Conditions tree: Degraded output, Failure to cease operation, Failure to operate, Intermittent operation, Loss of output, Other, Premature Operation.
  • Losses/Symptoms tree: Appearance (Shape change, Surface change), Behavior, Energy, Environment, Material, Other.

Step 6: Edit Fault Criticality Parameters

• "Coupling" failure diagram canvas showing a fault tree: Cyclic mechanical loads (Coupling), Vibration loading (Coupling), Imbalanced mechanical loads (Coupling) → combine into High cycle fatigue (Coupling); High mechanical load (Coupling) → Yielding (Coupling); High cycle fatigue → Fractured (Coupling); Yielding → Stretched (Coupling); Fractured AND Stretched → Couple Mechanical - rotational Torque (Coupling). Status bar: "Failure Paths Metrics (with Fault Injected)".
• "Properties" panel for "Fractured": Criticality tab sliders — Difficulty of Detection (4.3 "Moderate"), Probability/Occurrence (6.2 "Remote"); second view: Controllability (8.6 "Controllability 2"), Probability/Exposure (6.2 "Remote"); MIL-STD-1629a (Quant): Failure Mode Ratio (2.6E-1), Failure Effect Probability (0.81); MIL-STD-882E: Probability (6.2 "Remote"), Software Control (8.0 "Semi-Autonomous").

Step 7: Edit Connection Criticality Parameters

• "Properties" panels for connections in the Coupling failure diagram, each with General tab (Source/Target) and Criticality tab:
  • "Imbalanced mechanical loads -> High cycle fatigue": Causal Probability 7.52 ("Moderate").
  • "High cycle fatigue -> Fractured": Causal Probability 8.81 ("High"), Progression Rate 8.0 ("High").
  • "Fractured -> Mechanical - rotational Torque": Source "Fractured", Target "Couple Mechanical - rotational Torque (Coupling)", Function "Couple", Polarity radio (Positive/Negative — Negative selected), Causal Strength slider 6.48; Criticality tab Causal Probability 9.44 ("High").

Step 8: Failure Diagram Created

• Final "Coupling" failure diagram: Cyclic mechanical loads, Vibration loading, Imbalanced mechanical loads (Coupling) converge into High cycle fatigue (Coupling) → Fractured (Coupling); High mechanical load (Coupling) → Yielding (Coupling) → Stretched (Coupling); Fractured AND Stretched combine (OR-gate icons) into "Couple Mechanical - rotational Torque (Coupling)". Status bar: "Failure Paths Metrics (with Fault Injected)".