Langzeitzuverlässigkeit

Langzeitzuverlässigkeit, in English long-term reliability, is the probability that a product will perform its required function without failure for a defined period under stated conditions. It depends on design, materials, manufacturing quality, and the operating environment, and it influences safety, availability, maintenance requirements, and life-cycle cost.

Common metrics include mean time between failures (MTBF) and mean time to failure (MTTF), as well as the reliability function R(t) = P[T>t] and the hazard rate λ(t). In constant-stress assumptions, an exponential distribution is used; more generally, Weibull or lognormal models describe time-varying failure behavior.

Assessment methods include life testing and accelerated life testing (ALT), as well as reliability demonstrations and field data collection. Data analysis often relies on survival analysis, censoring techniques, and parameter estimation by maximum likelihood. Graphical methods such as Weibull plots aid interpretation.

Reducing long-term failure risk involves robust design, quality control, material selection, and environmental screening. Redundancy, fault tolerance, preventive maintenance, and reliability-centered maintenance also contribute. Standards and guidelines from IEC, MIL/DoD, and other bodies provide frameworks for reliability assessments.

Limitations include uncertainty when extrapolating beyond tested life, potential bias in accelerated tests, and the difficulty of accounting for real-world usage patterns. A balanced reliability program combines design for reliability, manufacturing discipline, data collection, and ongoing monitoring to manage life-cycle risk.