Location for Analysis Matrix (LAM)
Developed by Staehle to be the bookkeeping part of predicting and assuring performance; systematic basis for conducting failure analysis.
Corrosion damage cannot be predicted by generality; it is predicted by details.
The LAM was developed to provide a framework for assessing the details of possible corrosion or other deterioration damage in equipment by focusing attention on specific locations in subcomponents. The LAM method:
- Involves design and materials directly.
- Can be applied to simple or complex systems.
- Requires explicit consideration of possible problems.
- Identifies possibility of multiple locations for damage and possible multiple modes at a single location.
- Integrates design and materials considerations.
An example of multiple locations and multiple modes of failure is shown in Figure 1. This is an example from a steam generator used in pressurized water nuclear reactors (PWR). This figure shows numerous modes and locations of corrosion damage. Actually observed in engineering service.
| Figure 1 Schematic relationship of locations where accelerated corrosion occurs, modes and submodes of corrosion for a U-tube steam generator used in pressurized water nuclear reactor systems. (Numbers in [brackets] indicate similar submodes although they may occur at different stresses or temperatures. Letters e.g., (a), identify different mode-location occurrences of corrosion.) |
Predicting and assuring performance is a matter of the details.
The LAM involves defining the locations where failure is likely and defining the modes by which failure is likely to occur. With respect to Figure 1, a framework for analysis is illustrated in Figure 2. Figure 2a shows the modes and locations of possible corrosion damage for a steam generator of the type in Figure 1.
Figure 2b shows a matrix for organizing combinations of locations and modes of failure. This is called "a locations for analysis matrix", LAM.
| Figure 2 Location for analysis matrix shown in (b). (a) shows at left the locations for analysis, LAi, that are typical of steam generators used in pressurized water nuclear reactors. The possible modes and submodes of corrosion that can occur at these LAis are shown at the right. Locations for analysis and modes and submodes from the steam generator are shown in the matrix. (From Staehle) |
Steps in developing an LAM are:
Action 1. Identifying the chronological stage as in Figure 3: steady state operation, shutdown/startup, extended operation, construction stage.
| Figure 3 Schematic illustration of the 15 stages in the chronology of equipment. Stages separated in two categories according to whether they relate to conditions before startup or after. At each of these stages the possibility of aggressive degradation has to be considered. |
Action 2. Choosing the subcomponent: tubes in a steam generator, rebars in concrete, valves in internal combustion, fasteners and bumpers.
Action 3. Identify Location for Analysis, LAi: Choose where combinations of stressors are highest: stress, disturbed material, temperature, concentration of environmental species.
Action 4. Identify Modes, MDj and submodes SDj: Determine which modes and submodes of corrosion can occur at the LAi.
Action 5. Develop Location for Analysis Matrix, LAM: Develop matrix as shown in Figure 2b.
Action 6. Explicit actions on the i-j cells:
- Eliminate as not relevant
- Neglect if inconsequential
- Apply prior field performance
- Develop fundamental analysis
- Go/no-go experiments
- Accelerated tests
- Borrow from similar cells
| Figure 4 Possible actions for preparing location for analysis chart with respect to one cell. |
Action 7. Develop quantitative relationships from CBDA e.g.
- Environmental definition
- Material definition
- Mode definition
- Failure definition
- Statistical definition
Action 8. Identify necessary work: experimental, calculation, modeling.
Action 9. Integrate results for subcomponent: which cells produce the greatest damage; how many cells in this range?
Action 10. Integrate results for component consisting of multiple subcomponents: which components produce most frequent and most serious failure?
Action 11. Assess approaches for quantification of component performance.
Failures can be prevented; it is not hopeless.
References to Corrosion Based Design Approach and Location for Analysis Matrix
- R.W. Staehle, "Lifetime Prediction of Materials in Environments," Uhlig's Corrosion Handbook, 2nd edition, Ed. R.W. Revie, John Wiley and Sons, New York, 2000, pp. 27-84.
- R.W. Staehle, "Framework for Predicting Stress Corrosion Cracking," Environmentally Assisted Cracking: Predictive Methods for Risk Assessment and Evaluation of Materials, Equipment, and Structures, ASTM STP 1401, Ed. Russ Kane, American Society for Testing and Materials, West Conshohocken, PA, 2000.
- R.W. Staehle, "Combining Design and Corrosion for Predicting Life," presented as a plenary lecture at Life Prediction of Corrodible Structures, Ed. R.N. Parkins, conference held in Kauai, Hawaii, November 1991, NACE International, Houston, 1994, p. 138-291.
- R.W. Staehle, "Development and Application of Corrosion Mode Diagrams," Parkins Symposium on Stress Corrosion Cracking, Eds. S.M. Bruemmer, E.I. Meletis, R.H. Jones, W.W. Gerberich, F.P. Ford, and R.W. Staehle, conference held in Cincinnati, Ohio, October 21-24, 1991, TMS (The Minerals, Metals and Materials Society), Warrendale, Pennsylvania, 1992. pp. 447-491.
- R. W. Staehle, "Environmental Definition," Materials Performance Maintenance, R. W. Revie, V. S. Sastri, M. Elboujdaini, E. Ghali, D. L. Piron, P. R. Roberge and P. Mayer, eds., Pergamon Press, Ottawa, Ontario, 1991, pp. 3-43.
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Roger W. Staehle, Ph.D.
22 Red Fox Road
North Oaks, MN 55127 USA
Telephone (651) 482-9493
Cell Phone: (612) 889-4384
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Email: rwstaehle@rwstaehle.com