Meaning
Deductive failure logic identifies the root conditions necessary for a system state or specific hazard to occur. Fault tree analysis constructs a visual representation of these pathways by linking Boolean gates to primary events. This logic maps the logical intersection of software bugs, hardware degradation, or operator errors that contribute to a failure.
The method calculates probability based on the failure rates assigned to individual branches of the network.
Structural Logic
Components in a system integration phase undergo systematic decomposition to map causal chains from the top level down to the base events. Engineers link nodes with AND gates where all conditions must occur simultaneously for the failure to propagate upward. OR gates connect branches where a single event suffices to trigger the next state.
Analysts define the boundary of the model by the resolution of the sensors and components present in the schematic. The final output provides a mathematical expression for the system reliability.
Quantitative Assessment
Numerical values assigned to each leaf node permit the calculation of the top-level probability. Data from field reliability reports or accelerated life testing provides the input rates for electrical or mechanical elements. A transition to the next gate updates the probability distribution across the entire path.
When multiple failure modes share a common path, the analysis identifies single points of failure that threaten the entire architecture. This calculation establishes the probability density function for the system during a defined mission time.
Operational Verification
Qualification testing uses the developed tree to determine which specific sub-assemblies require redundant paths or additional shielding. Verification engineers run simulations against the model to confirm that the predicted failure modes match the observed physical behavior during thermal stress or vibration cycles. Each branch serves as a target for diagnostic software that monitors signal integrity across the data bus.
The mathematical model remains valid only as long as the component failure rates reflect the actual environmental conditions of the deployment.
