Board Failure Research Articles

Damage criterion and safety assessment approach to tubular joints

Based on the Continuum Damage Mechanics (CDM), a damage criterion is proposed to predict the macrocrack initiation for tubular joints. The guidance on prediction to ultimate load carrying capacity of flawed tubular joints is provided by means of the modified Central Electricity Generating Board (CEGB) Failure Assessment Diagram (FAD). Non-linear FE analyses were carried out on uncracked and cracked T, K and KK tubular joints. Triaxial stress distributions and equivalent plastic strains near weld toes in the chord around the brace were numerically obtained for uncracked tubular joints. The crack driving force, J-integral, and ultimate collapse loads of cracked tubular joints subjected to axial brace loading were evaluated by FE analyses. Load–displacement curves and ultimate strengths for uncracked and cracked T, K and KK-joints were numerically determined. A uni-planar KK tubular joint specimen was tested under anti-symmetrical axial loads. During the test, the load–displacement curve and the ultimate strength were measured. Meanwhile, crack initiation and growth were observed until complete failure. FE and test results show that the damage criterion gives good prediction for macrocrack initiation in tubular joints, and the modified CEGB approach is suitable for the safety assessment to flawed tubular joints.

Fatigue Tests on Prestressed Concrete Beams Made With Debonded Strands

Six fatigue tests were performed on pretensioned concrete beams containing debonded strands to determine if their behavior would be similar to the behavior observed from statistically loaded companion beams. Each initially precracked beam specimen was subjected to at least one million cycles of equivalent service load. Periodically, large static overloads were applied to each specimen to simulate the relatively large permit loads that some structures may be required to resist, and to increase strand bonding requirements. Loads, deflections, and strand slips were measured at significant intervals and beam behaviors were observed. After completion of fatigue testing, the beams were loaded statically until failure. The test demonstrated that although repeated loading may cause some additional slippage, the strand slips remained quite small and did not affect the overall beam behavior. Furthermore, the ultimate behavior of these beams verifies that the prediction for board failure is dependent on the propagation of cracking through the transfer zone of a debonded strand, confirming similar results obtained from static tests.

Analysis of the delaying effects of overloads on fatigue crack propagation: Chen, D.-H. and Nisitani, H. Eng. Fract. Mech. 1991 39, (2), 287–298

Based on the Continuum Damage Mechanics (CDM), a damage criterion is proposed to predict the macrocrack initiation for tubular joints. The guidance on prediction to ultimate load carrying capacity of flawed tubular joints is provided by means of the modified Central Electricity Generating Board (CEGB) Failure Assessment Diagram (FAD). Non-linear FE analyses were carried out on uncracked and cracked T, K and KK tubular joints. Triaxial stress distributions and equivalent plastic strains near weld toes in the chord around the brace were numerically obtained for uncracked tubular joints. The crack driving force, J-integral, and ultimate collapse loads of cracked tubular joints subjected to axial brace loading were evaluated by FE analyses. Load–displacement curves and ultimate strengths for uncracked and cracked T, K and KK-joints were numerically determined. A uni-planar KK tubular joint specimen was tested under anti-symmetrical axial loads. During the test, the load–displacement curve and the ultimate strength were measured. Meanwhile, crack initiation and growth were observed until complete failure. FE and test results show that the damage criterion gives good prediction for macrocrack initiation in tubular joints, and the modified CEGB approach is suitable for the safety assessment to flawed tubular joints.

Natural Language Interface for Fault Diagnosis System of Nuclear Power Plant Control Systems

A fault diagnosis system was developed to improve the availability and maintainability of control systems in nuclear power plants. To facilitate man-machine communications in the system a natural language interface was introduced. Features of the interface include two-step analysis of the meaning of input sentences, identification of the kind of input content using sentence patterns, and retrieval of the information required. For the information retrieval, when information is lacking supplementation is done by referring to the dialog history and knowledge of the control system composition. Dialog tests, including the required information inputs for diagnosis and questions about the validity of the diagnosis results, were performed by the control system simulator for an assumed component failure, such as a printed circuit board failure. Dialog inputs were made by voice and outputs were by voice or a CRT display. The tests confirmed that inputs required in the diagnosis process can be entered by voice without a conscious limitation of the input sentence style, and that adequate answers can be obtainned in about 1 s allowing maintenance personnel to have a dialog naturally without being aware of any waiting time.

Natural language interface for fault diagnosis system of nuclear power plant control systems.

A fault diagnosis system was developed to improve the availability and maintainability of control systems in nuclear power plants. To facilitate man-machine communications in the system a natural language interface was introduced. Features of the interface include two-step analysis of the meaning of input sentences, identification of the kind of input content using sentence patterns, and retrieval of the information required. For the information retrieval, when information is lacking supplementation is done by referring to the dialog history and knowledge of the control system composition. Dialog tests, including the required information inputs for diagnosis and questions about the validity of the diagnosis results, were performed by the control system simulator for an assumed component failure, such as a printed circuit board failure. Dialog inputs were made by voice and outputs were by voice or a CRT display. The tests confirmed that inputs required in the diagnosis process can be entered by voice witho...

Adhesive bonding of acetylated aspen flakes, Part 2. Effects of emulsifiers on phenolic resin bonding

Acetylation of aspen flakes causes a reduction in the wettability of the flakes to a water-soluble phenolic resin. In this study, addition of emulsifiers to the phenolic resin improved wettability of the acetylated flake surface. In general, water-to-oil emulsifiers were more effective than oil-to-water emulsifiers. Internal bond strength and modulus of rupture were higher in acetylated flakeboards in which a water-to-oil emulsifier was added to the phenolic resin compared to nonacetylated control flakeboards made with phenolic resin alone. Image analysis of the failed surfaces of acetylated flakeboards after an internal bond test showed about 50% board failure in the wood and about 50% in the glueline, regardless of the emulsifier used in the phenolic resin.

Comparative Analysis of the Eight Cities

Our purpose in this concluding analysis is to point up the various patterns which seem to emerge in these case studies. We are well aware that eight cities represent a small sample. They were selected more with reference to scholarly access than representativeness. As a result, all of the cities have universities in them. In the three cities which emerge as “most successful,” universities play a significant role—if not a dominant one—in the life of the community. Although direct participation of these universities, as such, is not emphasized in the case studies, their indirect influence may have been extremely significant in producing atypical results. Clearly we cannot hope to present any final and ultimate conclusions, but it is nevertheless possible to make a number of suggestive observations about why the school boards in some cities were able to respond to the problem of de facto school segregation more successfully and effectively than others. While there is, of course, virtually no invulnerable or uncontroversial method for measuring the relative success and failure of school boards confronted with racial imbalance in their schools, three possible yardsticks come to mind. First, do the statistics show either a decrease in the racial imbalance in some or all of a city's schools or a decrease in the trend toward increasing racial imbalance? Second, has the school system actually implemented some sort of desegregation program? Third, did the school boards (or superintendents) resolve conflict by satisfying or placating the various disputants?

No-Distribution Rule Held to Be an Unfair Labor Practice despite Board's Failure to Consider Alternative Means of Communication

No-Distribution Rule Held to Be an Unfair Labor Practice despite Board's Failure to Consider Alternative Means of Communication

Sir Alfred Ewing and Naval Education

THE connexion of Sir Alfred Ewing with naval education came about through the decision of the Admiralty, in 1902, to carry out a root and branch reform of the training of officers and men in all sections of the Navy. The reform was long overdue, for even up to 1901, junior officers spent a part of their time in learning to manoauvre ships under sail, although for all practical purposes sails in warships had been obsolete for thirty years. Then, too, there was the urgent problem of the staffing of the engine rooms of the steadily increasing fleet, a problem rendered difficult by the failure of successive Boards of Admiralty to adjust the status of naval engineers in accordance with their responsibilities.

Medical Forgeries—the Hagen Burger Case.

Denver, Feb. 19,1906. To the Editor: —Dr. J. C. Connell's letter inThe Journal, February 17, contains certain misleading statements relative to the now famous Hagen Burger case that I can not allow to go without correction. By reference to my article on Medical Forgeries inThe Journal, February 3, it will be seen that in the second paragraph of his letter he has misquoted the sentence relative to the power of revocation vested in the Colorado licensing board. He has changed the past tense of the verb to have to the present. In criticising the board's failure to convict Hagen Burger of the criminal charge still pending against him, as compared with the inability, thus far, of the Queen's University senate to revoke the diploma which they know was secured on fraudulent representation, Dr. Connell fails to take into consideration the greater difficulty one encounters in securing a conviction

A School Board Failure

A School Board Failure