Prediction durability

Because the fracture toughness depends both on cure time and temperature, the arbitrary selection of time and temperature for accelerated tests may not be appropriate for reliable prediction of longterm service life of joints (J7). In order to reduce test variability and improve the durability prediction of adhesive joints, it would be necessary first to control the cure temperature and time required to produce a level of fracture toughness that does not change further (14). The study is thus an excellent example of a multidisciplinary approach combining chemistry, fracture mechanics, and wood science in the investigation of the adhesive bonding of wood. 

Brinson, H.F., "Durability Predictions of Adhesively Bonded Composite Structures Using Accelerated Characterization Methods," Composite Structures, I.H. Marshall, ed., Elvesier, 1985, p.1-18. 

COMPOUND VISCOELASTIC PROPERTIES AND FRACTURE MECHANICAL BEHAVIOUR IN TRUCK TIRE DURABILITY PREDICTION... 

Karbhari, V.M., Abanilla, A., 2007. Design factors, reliabihty, and durability prediction of wet lay-up carbon/epoxy used in external strengthening. Composites Part B 38, 10—23. 

The durability of a building (i.e. its life expectancy and its resistance to deterioration) is determined by deliberate design decisions relating to stmcture and choice of materials as much as to the natural or precipitate process of ageing. Within certain limits, the design of an industrial building can and should take into account the predicted use or lifespan of the process or method of operation which it is to accommodate. To aim at durability beyond that has ascertainable cost implications. These may be acceptable if the building is to serve future known or even unpredictable purposes. 

A prerequisite to a corrodable material being used is that it is known to have a useful and reasonably predictable life. Planned, or unplanned downtime costs money and the intervals between planned replacements must be of reasonable duration. In practice, the replacement interval is usually conservative at first and then as experience accumulates, the intervals between planned replacements will usually extend. The main reason for choosing a planned maintenance policy is that on a discounted cash flow (DCF) calculation over the life of the plant, the cost of regular replacements including maintenance labour and downtime is less than the extra initial capital cost of a more durable material. 

In this connection, there is some indication that while the Corrodkote test can be depended upon to reveal coatings of unsatisfactory durability, there has been some question as to its ability to distinguish between, or to predict the relative protective value or length of useful life of, different coating systems in the very good or excellent durability range. 

Civil Infrastructure made to withstand the best predictions of likely Extreme Weather Events and with adequate Durability for their exposure to Worsened Average Conditions (CAN/CSA S478 is the Canadian Standards Association s Guideline for Durability in Buildings ). 

Targeted Durability based on Life Cycle Analyses considering the best Predictions of Future Conditions (in terms of changed averages and new extremes). 

Designing for Controlled Durability Adapted to the best Predictions of Future Weather Conditions. 

L. Matisova-Rychla and J. Rychly, Inherent relations of chemiluminescence and thermooxidation of polymers, In R.L. Clough, N.C. Billingham and K.T. Gillen (Eds.), Advances in Chemistry, Series 249 Polymer Durability, Degradation, Stabilization and Lifetime Prediction. American Chemical Society, Washington, DC, 1996, p. 175. 

An important advance in the understanding of the chemical behaviour of glasses in aqueous solution was made in 1977, when Paul (1977) published a theoretical model for the various processes based on the calculation of the standard free energy (AG ) and equilibrium constants for the reactions of the components with water. This model successfully predicted many of the empirically derived phenomena described above, such as the increased durability resulting from the addition of small amounts of CaO to the glass, and forms the basis for our current understanding of the kinetic and thermodynamic behaviour of glass in aqueous media. 

Robinson, S., Nicholson, R. A., Pollard, A. M., and O Connor, T. P. (2003). An evaluation of nitrogen porosimetry as a technique for predicting taphonomic durability in animal bone. Journal of Archaeological Science 30 391 —403. 

There are, however, other components where the process of degradation is clearer and the rate of change easier to deduce, particularly when that process is mechanical rather than chemical. This would be so in a simple case where surface wear proceeded at a linear rate. Discussion of these problems will explain why there is still a shortage of reliable data and also why much durability testing falls short of the breadth and quality necessary to make reliable predictions. 

The uncertainty of a measurement is always a very important consideration but it is especially so with durability tests. In addition to the basic physical test methods, there are the complications of exposure conditions, tests spanning long times and the process of extrapolating results to make predictions. The combination of these factors will inevitably lead to large uncertainties that can very easily be of such a magnitude that any conclusions are meaningless. Terms used to describe precision include repeatability, which refers to within laboratory variation and reproducibility, which refers to variation between laboratories. 

Examination of reinforced structures has so far shown the creep strain to be less than predicted, generally because the soil carries more load than is allowed for in design. Tests on materials buried and then exhumed after 10-20 years have so far shown little significant evidence of degradation, although little would be expected in the relatively benign soil conditions experienced. In common with industrial products, early failures have been shown to be due to errors in design or construction any failures due to poor durability will occur later, hopefully very much later. 

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