Prediction of service life

From the design point of view, it would be desirable to be able to predict the service life of a given bonded structure in the use environment this capability has yet to be developed. Some progress has been made, however, particularly in the application of reaction rate theory to predict the failure time of test specimens. 

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Methods. To observe that corrosion testing in the laboratory frequently fails to predict what happens in real-world environments is to admit that the mechanisms controlling corrosion in such environments are not understood, even at this late date of study. Mechanism-based test methods for monitoring corrosion are needed that will provide reliable and rapid prediction of service life for corrosion-susceptible systems. It is expected that statistical analysis will play a... 

Evaluation of protective systems and prediction of service life... 

Fig. 4 Comparison of concepts of prediction of service life between new reinforced concrete with CFRP reinforcement and ordinary reinforced concrete with steel reinforcement...

Areas requiring special attention in the future include improved stabilization processes for existing polymers and the synthesis of new polymeric materials which are more resistant against environmental corrosion than those presently used. The implications of the stability of natural polymers for the prediction of service life of synthetic polymers,the general effects of hydrolysis, the light-induced hydrolytic degradation are relevant research topics. 

Corrosion Testing Objectives of SCC testing are (i) determination of the risk of SCC for a given application and comparison of alloys (ii) examination of the effects of chemical composition, metallurgical processing, fabrication practices for structural components (iii) evaluation of protective systems and prediction of service life (iv) development of new alloys, which are less expensive, and offer a longer, safer, and efficient performance for chosen environments (v) evaluation of claims for SCC performance of improved mill products. 

Table 12.3 Prediction of Service Life as Funrtion Inhibitor Concentrations for Different Types of Steel...

Laboratory accelerated weathering devices have been used for more than 80 years with increasing importance concomitant with the development of more weather-able materials and the need to determine in a short time the effects of natural exposures over prolonged periods. The importance of these devices lies in their ability to accelerate the weathering processes imder controlled and reproducible conditions. They are particularly useful in research and development of new polymeric formulations. They are also used for quality control and specification testing. However, their application to prediction of service life under use conditions is still under development (see section on Laboratory Accelerated Versus Natural Weathering). 

Tests of the bare, unprotected metal are useful to establish a minimum basis of performance and comparative ranking. However, the applicability to the end use and prediction of service life require evaluation of the protective coatings and maintenance procedures to be used in service. 

The glass coating of the GLASTEEL composite is a non-conductive mixture of low energy oxides that can corrode only by a self-limiting ion exchange reaction (acids) or by direct chemical solution (alkalis). Consequently, the corrosion rates of GLASTEEL can be accurately measured and valid predictions of service life can be made. 

Plastics degradation due to atmospheric loads is influenced to various degrees by various factors, such as heat, radiation (UV and IR), rain, humidity, atmospheric pollution (NO j, SO2 and O3 and other industrial emissions), thermal cycles, and the oxygen content of air. None of these factors is locally and temporally constant. In order to obtain as precise a prediction of service life as possible, all factors relevant to the corresponding environment have to be given consideration [65]. 

K Sen, P Kumar. Polypropylene geotextiles long term stability and prediction of service life. Proc World Textile Congress on Polypropylene in Textiles,... 

The stochastic model for the prediction of service life has a number of... 

Weathering Resistance Prediction of service life, although one of the most important areas of testing, is probably the most uncertain. Cable jackets of synthetic rubber used in the Distant Early Warning (DEW) Line in Northern Canada in the 1950s were forecast to have a 20-year lifetime. Most are stiU in service. Similar synthetic rubber wire coverings were used at that time for automotive wire harness when... 

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