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Prediction Methods: Various organizations have published standards specifying how parts stress modeling should be carried out. Some from electronics are:
- MIL-HDBK-217 (US Department of Defense)
- Bellcore
- HRD-5 (British Telecom)
- and many others
These "standards" produce different results, often by a factor of more than two, for the same modeled system. The differences illustrate the fact that this modeling is not an exact science. System designers often have to do the modeling using a standard specified by a customer, so that the customer can compare the results with other systems modeled in the same way.
All of these standards compute an expected overall failure rate for all the components in the system, which is not necessarily the rate at which the system as a whole fails.
MIL-HDBK-217: The original reliability prediction handbook was MIL-HDBK-217, the Military Handbook for "Reliability Prediction of Electronic Equipment". MIL-HDBK-217 is published by the Department of Defense, based on work done by the Reliability Analysis Center and Rome Laboratory at Griffiss AFB, NY. The MIL-HDBK-217 handbook contains failure rate models for the various part types used in electronic systems, such as ICs, transistors, diodes, resistors, capacitors, relays, switches, connectors, etc. These failure rate models are based on the best field data that could be obtained for a wide variety of parts and systems; this data is then analyzed and massaged, with many simplifying assumptions thrown in, to create usable models.
RIAC 217Plus: The Reliability Information Analysis Center (RIAC) released 217Plus in July 2006 as a replacement for the earlier Reliability Analysis Center (RAC) methodology. The new methodology that correct several recognized deficiencies of MIL-HDBK-217
Bellcore: Bellcore was a telecommunications research and development company that provided joint R&D and standards setting for AT&T and its co-owners. Because of dissatisfaction with military handbook methods for their commercial products, Bellcore designed its own reliability prediction standard for commercial telecommunication products. In 1997, the company was acquired by Science Applications International Corporation (SAIC) and the company's name was changed to Telcordia. Telcordia continues to revise and update the standard. The latest two updates are SR-332 Issue 1 (May 2001) and SR-332 Issue 2 (September 2006), both called "Reliability Prediction Procedure for Electronic Equipment."
HRD-5: The HRD5 model is based on the Handbook for Reliability Data for Electronic Components used in Telecommunications Systems. Developed by British Telecommunications plc, this standard provides part models for a wide range of electronic components. The HRD5 model replaces the earlier CNET 93 model. Both are similar but HRD5 provides simpler failure rate models and requires fewer data parameters for analysis.
IEC 62380: The IEC 62380 (formerly RDF 2000 (UTE C 80-810)) module is a reliability prediction program based on the French telecommunications standard IEC TR 62380 Edition 1. The IEC 62380 standard predicts failure rates for electronic equipment based on the reliability data handbook UTE C 80-810 published by UTE (Union Technique de l'Electricite). The IEC TR 62380 reliability prediction method considers the effects of phased mission profiles on operating and non-operating components. This method also accounts for the effects of thermal cycling on the component failure rate due to variations in the ambient temperature and component switch on and off. IEC TR 62380 also predicts life expectancy for components where applicable.
NSWC-98: NSWC Standard 98 is the US Naval Surface Warfare Center standard for the reliability prediction of mechanical components. NSWC-98 uses a series of models for various categories of mechanical components to predict failure rates which are affected by temperature, stresses, flow rates and various other parameters. Many of the categories of mechanical equipment are in fact composed of a collection of sub-components which must be modeled by the user. The user should be familiar with the equipment and the Handbook so that the correct type and number of sub-components can be included in the model.
FIDES: The FIDES Guide aims to enable a realistic assessment of the reliability of electronic equipment, including systems operating in severe environments (defense systems, aeronautics, industrial electronics, transport, etc.). The FIDES Guide also aims to provide a concrete tool to develop and control this reliability. The FIDES methodology is based on the physics of failures and supported by the analysis of test data, field returns and existing modeling. It is therefore different from the traditional methods developed mainly through statistical analysis of field returns. This process yields predicted reliability results that are not influenced by the industrial domains of the methodology's creators.
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