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Methodology to improve design of accelerated life tests in civil engineering projects.

Lin J, Yuan Y, Zhou J, Gao J - PLoS ONE (2014)

Bottom Line: As an example, the methods are applied to the pipe in subsea pipeline.However, they can be widely used in other civil engineering industries as well.The proposed method is compared with current methods.

View Article: PubMed Central - PubMed

Affiliation: Department of Construction Management, Dalian University of Technology, Dalian, China.

ABSTRACT
For reliability testing an Energy Expansion Tree (EET) and a companion Energy Function Model (EFM) are proposed and described in this paper. Different from conventional approaches, the EET provides a more comprehensive and objective way to systematically identify external energy factors affecting reliability. The EFM introduces energy loss into a traditional Function Model to identify internal energy sources affecting reliability. The combination creates a sound way to enumerate the energies to which a system may be exposed during its lifetime. We input these energies into planning an accelerated life test, a Multi Environment Over Stress Test. The test objective is to discover weak links and interactions among the system and the energies to which it is exposed, and design them out. As an example, the methods are applied to the pipe in subsea pipeline. However, they can be widely used in other civil engineering industries as well. The proposed method is compared with current methods.

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Related in: MedlinePlus

MEOST Operating plan graphic.Testing first proceeds inside the “Black Dot Operating Rectangle” which is defined as 97.5% maximum combined stresses over the design life, and then beyond the rectangle by overstressing in time-steps. Individual failure modes are identified by root cause analysis and plotted on a Weibull plot to determine if their 90% confidence limit will intersect the Operating Rectangle before the design life is reached at max stress.
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pone-0103937-g002: MEOST Operating plan graphic.Testing first proceeds inside the “Black Dot Operating Rectangle” which is defined as 97.5% maximum combined stresses over the design life, and then beyond the rectangle by overstressing in time-steps. Individual failure modes are identified by root cause analysis and plotted on a Weibull plot to determine if their 90% confidence limit will intersect the Operating Rectangle before the design life is reached at max stress.

Mentions: Briefly as seen in Fig. 2, the MEOST plan is to operate the system within its operating limits for a period of time while exposing it to all energy types simultaneously. Time should be compressed between cycles so that the system experiences the largest possible fraction of stress cycles expected over its design life. For example, if oil flow in a pipeline is expected to change once a week for 20 years, this is about 1,000 cycles. By cycling flow once every 15 minutes the entire life relative to this stress can be simulated in a little over 10 days. This strategy is time acceleration. Flow rate would go from max to standstill and back, but at normal rates of change (no energy spikes). The “Black Dot” represents 97.5% of the combined maximum stresses (operating plus environmental) applied throughout the design life.


Methodology to improve design of accelerated life tests in civil engineering projects.

Lin J, Yuan Y, Zhou J, Gao J - PLoS ONE (2014)

MEOST Operating plan graphic.Testing first proceeds inside the “Black Dot Operating Rectangle” which is defined as 97.5% maximum combined stresses over the design life, and then beyond the rectangle by overstressing in time-steps. Individual failure modes are identified by root cause analysis and plotted on a Weibull plot to determine if their 90% confidence limit will intersect the Operating Rectangle before the design life is reached at max stress.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4128810&req=5

pone-0103937-g002: MEOST Operating plan graphic.Testing first proceeds inside the “Black Dot Operating Rectangle” which is defined as 97.5% maximum combined stresses over the design life, and then beyond the rectangle by overstressing in time-steps. Individual failure modes are identified by root cause analysis and plotted on a Weibull plot to determine if their 90% confidence limit will intersect the Operating Rectangle before the design life is reached at max stress.
Mentions: Briefly as seen in Fig. 2, the MEOST plan is to operate the system within its operating limits for a period of time while exposing it to all energy types simultaneously. Time should be compressed between cycles so that the system experiences the largest possible fraction of stress cycles expected over its design life. For example, if oil flow in a pipeline is expected to change once a week for 20 years, this is about 1,000 cycles. By cycling flow once every 15 minutes the entire life relative to this stress can be simulated in a little over 10 days. This strategy is time acceleration. Flow rate would go from max to standstill and back, but at normal rates of change (no energy spikes). The “Black Dot” represents 97.5% of the combined maximum stresses (operating plus environmental) applied throughout the design life.

Bottom Line: As an example, the methods are applied to the pipe in subsea pipeline.However, they can be widely used in other civil engineering industries as well.The proposed method is compared with current methods.

View Article: PubMed Central - PubMed

Affiliation: Department of Construction Management, Dalian University of Technology, Dalian, China.

ABSTRACT
For reliability testing an Energy Expansion Tree (EET) and a companion Energy Function Model (EFM) are proposed and described in this paper. Different from conventional approaches, the EET provides a more comprehensive and objective way to systematically identify external energy factors affecting reliability. The EFM introduces energy loss into a traditional Function Model to identify internal energy sources affecting reliability. The combination creates a sound way to enumerate the energies to which a system may be exposed during its lifetime. We input these energies into planning an accelerated life test, a Multi Environment Over Stress Test. The test objective is to discover weak links and interactions among the system and the energies to which it is exposed, and design them out. As an example, the methods are applied to the pipe in subsea pipeline. However, they can be widely used in other civil engineering industries as well. The proposed method is compared with current methods.

Show MeSH
Related in: MedlinePlus