Reliability planning and reliability testing

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In the reliability planning is part of the quality planning , which deals in consideration of predetermined time periods and conditions of use with the planning and predicting the behavior of a single unit. The reliability test is about checking or confirming that the requirements relating to certain reliability features have been met.

The planning and the checking of the reliability are parts of the reliability management, which in turn is part of the quality management .

Reliability planning

Objective and task of reliability planning

The goal of reliability planning is the creation, preparation and organization of rules for reliability and safety management . Therefore, reliability planning (planning the reliability requirement) is one of the most important elements of quality planning. Reliability planning is part of reliability management together with organization, management and control. These reliability management activities are applied to a company's reliability requirements. In addition, reliability planning is a sub-area of ​​claims planning. Here, plans are made with regard to the individual reliability requirements. Planning refers to a group of reliability characteristics.

Elements of reliability planning are the

  • Project organization,
  • Project planning,
  • Quality requirements,
  • Security analysis,
  • the correct selection of components and manufacturing processes,
  • Configuration management and
  • Quality inspection.

System reliability planning

The planning also has the goal of deriving the failure of a system. It is assumed that the individual components fail. This means that you can plan the reliability in advance based on calculations and previous behavior of the individual elements. Boolean theory is often used in calculating the reliability of a system . With this theory, the service life of the system can be determined based on the service life of the individual components and under certain conditions. The prerequisite for this is that the failure behavior of the components does not influence one another. The failure behavior of the elements often depends on the structure of the system. Therefore z. B. the coupling or the arrangement of the elements of the system has an influence on the failure behavior of an element. This is best seen in the mechanical, electromechanical and optical components. If the degree of mutual interference between the components is very high, the failure rate for an individual component cannot be given. For this reason, the failure rate in such cases can only be planned once the failure rate of the entire system has been determined empirically.

There are qualitative and quantitative methods (failure rate analysis) to determine the reliability of systems. In the quantitative methods, the weak points and their effects are sought. These include B. FMEA , FMECA and event flow analyzes . The effects of errors and failures are examined with the qualitative methods. These methods are used to plan the reliability or to be able to calculate the system reliability in advance. With these methods, the failure behavior is determined by statistical methods such as fault tree analysis and Markov theory .

Furthermore, there are models for planning and forecasting reliability on the basis of current data, which can provide results on the increase in reliability. This includes B. Reliability Growth Management (RGM). The RGM method is used to plan, visualize and track reliability in the development phase. In this program, the mean target service life and the cumulative total service life are first determined in the planning phase on the basis of existing empirical values. The mean service life is estimated on the basis of previous developments or determined in an initial test phase. In the development phase, at least the growth rate that is planned based on the start and end point should be achieved if the desired reliability goal can be achieved in a foreseeable time with certain resources.

Reliability check

Aim and task of the reliability check

The aim of the reliability test is to provide evidence of the reliability of the products. The prerequisite for this is that the productivity of the test conditions and their definition in a test plan are given.

The reliability check also has other objectives. During the test, certain parameters should be determined and the possible weak points of the product identified. Improvement measures can thus be taken. In addition, it should be checked whether the actual planning made in the production planning and development phase can be confirmed. Furthermore, the reliability test should prove that the requirements are met and determine whether the technological processes influence the reliability. Ultimately, the reliability test should lead to a reduction in incorrect performance and life cycle costs.

During the development phase, the reliability test can be carried out on a test sample (sample component). If the test is made during production, the products are then available in greater numbers and have a higher value. Due to the limited capacity of the test bench, the test has to be restricted because it is not possible to carry out as many tests as in the development phase. The response time would be too long with the throughput times up to failure considering normal operations to be able to recognize the risks and the reliability in time.

It is possible to check the changes in relevant characteristics with specific tests at higher loads. Some tests used to check reliability are the HASS test (Highly Accelerated Stress Screening) and the Highly Accelerated Life Test (HALT test). In order to ensure the reliability of the product in the use phase, it is necessary to carry out so-called reliability tests in the development phase. The statistical evaluation of these tests is made by life time distributions.

In the reliability test, the results can only be known when the life expectancy of the units has passed. Longer periods of time are required for this, which is why the reliability tests are very complex. Consequently, the reliability check is only an addition to the reliability planning.

literature

  • A. Birolini: Quality and reliability of technical systems: theory, practice, management. Berlin / Heidelberg 1985, ISBN 3-540-15542-2 .
  • Association of the Automotive Industry: Quality Management in the Automotive Industry: Reliability Methods and Tools. 3. Edition. Frankfurt am Main 2000, ISSN  0943-9412 .
  • H. Zollondz: Lexicon quality management: Handbook of modern management based on quality management. Munich 2001, ISBN 3-486-24316-0 .
  • E. Hering, J. Triemel, H. Blank: Quality management for engineers. 5th edition. Heidelberg 2003, ISBN 3-662-09616-1 .
  • W. Geiger: Introduction to quality theory, systematics, terminology. Braunschweig 1986, ISBN 3-528-03357-6 .
  • G. Linß: Quality Assurance-Technical Reliability. Munich 2016, ISBN 978-3-446-44658-8 .
  • R. Jochem, M. Menrath: Global Quality Management. Düsseldorf 2015, ISBN 978-3-86329-450-2 .
  • web.utanet.at

Individual evidence

  1. a b A. Meyna, B. Pauli: Reliability Technology: Quantitative Evaluation Methods. 2nd Edition. Munich / Vienna 2010, ISBN 978-3-446-41966-7 .
  2. W. Geiger, W. Kotte: Handbook Quality: Basics and elements of quality management: Systems perspectives. 5th edition. Wiesbaden 2008, ISBN 978-3-8348-0273-6 .