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No description available.

No description available.

The work contained herein is in pursuance of the Development of the SMART aircraft bolt. Failure of the bolt in the aircraft wing is taken for granted in the project, and the consequent repairs are presently very costly. The SMART material investigated in this work is the TRIP steel, and any reference to SMART material, in this work, shall at all time mean TRIP steel. Investigation of the stresses pertaining to bolts in general is carried out, based on the bolt theories and using the finite element analysis. An optimal bolt based on impact resistance only has also been suggested. Metallurgical behaviour of materials similar to TRIP materials is also investigated, including a section dedicated only to TRIP steels. Therefore, the work contained herein acts as a good base for further research. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2002.

The motivation behind this study is the lack of specialized analysis regarding internal failure caused by the adiabatic shear hand (ASB) phenomenon in the cold-headed products. Its aim was to present an integrated workability study to improve and assist cold-heading (CH) multistage design procedures to replace the current design rules of thumb, as they are neither effective nor adequate in fulfilling the needs of the new developments in the rapidly expanding CH industry. / To achieve these goals, a comprehensive testing methodology and FE modeling, implemented within ABAQUS/Explicit, were established. This methodology includes an instrumented Drop Weight Compression Test (DWCT) tower equipped with a guided pocket die-set configuration capable of developing internal failure at different stages of ASBs and integrated metallographic inspection techniques. A validated FE model of the DWCT and guided pocket die-set configuration was a valuable tool in establishing the failure criteria and indicating the workability limits. / A detailed experimental and FE study for the ASB stages in the CH process was introduced to uncover the affect of different parameters controlling the failure mechanisms within the ASBs in the CH process. This study investigated the effect of the thermal, geometric and the material flow softening and hardening mechanisms affecting ASB evolution. Moreover, a detailed metallurgical and FE study of the internal ductile and Transformed Adiabatic Shear Band (TASB) failures caused by the ASB phenomenon in DWCT was conducted. / Three ductile failure criteria were introduced to predict the initiation and location of the internal ductile failure in the ASBs. One TASB failure criteria was introduced to predict the phase transformation to undesirable brittle martensite. These failure criteria were employed to establish integrated workability methodologies to indicate the objective workability limits. / Applying these workability methodologies on multistage CH FE models showed that these methodologies are an efficient tool to predict the damage levels and failure initiation locations within the cold-headed bolts. Moreover, these methodologies were successful in optimizing the die designs in order to reduce damage levels.

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An analytical and experimental investigation was conducted to study the six bolt flush moment end-plate connection configuration which is used in steel frame construction. The limit states of plate yielding and bolt fracture were analyzed using yield-line theory to predict endplate thicknesses and a split-tee analogy to develop a method to predict bolt forces. Five experimental tests were conducted on four configurations within a matrix of geometric parameters. The predicted ultimate moment showed good . correlation to the yield moment obtained from the experimental deflection plots. The experimental bolt forces correlated well with the predicted bolt forces when plotted versus the applied moment. Additionally, an equation to model the moment-rotation relationship was developed from a regression analysis to determine the construction type suitable for a given connection configuration. Finally, a method of designing the six-bolt flush end-plate configuration is presented and an example given. / Master of Science

An experimental investigation was conducted to study the behavior of snug tight ASTM A325 bolts in moment end-plate connections for use in single story buildings. Wind loading was deemed to be the critical loading on snug tight bolt, moment end-plate connections. A test loading sequence was established based on a statistical analysis of the 50-year wind loading on low rise buildings. Eleven specimens, representing six end-plate configurations, were tested under cyclic loading covering expected wind loads in the range of 33 to 100 percent of the connection design (allowable stress design) moment. Following the cyclic loading, the specimens were statically loaded to failure, and the experimental strengths were compared with predicted strengths for connections with fully tightened A325 bolts. Additionally, the effect of snug tight bolts on connection stiffness are considered. Finally, recommendations for the use of snug tight bolts in moment end-plate connections were provided. / Master of Science

A new philosophy in structural health monitoring was explored, with the view to the creation of a smart mining bolt: one which would bear the normal load of any bolt used in South African gold mining tunnels, but at the same time be capable of monitoring its own level of damage. To this end, a survey of various smart materials currently used in structural health monitoring applications, was conducted, and a group known as strain memory alloys isolated as holding the most promise in this regard. Strain memory alloys give an indication of peak strain based on an irreversible transformation from paramagnetic austenite to ferromagnetic martensite, which occurs in direct proportion to the amount of strain experienced by the material. A measurement of magnetic permeability can therefore be correlated to peak strain. An extensive study of the alloying chemistry, material processing and transformation characteristics was therefore carried out, including an analytical model for the quantification of the energy associated with martensitic nucleation, at a dislocation-disclination level. The conditions within typical South African gold mining tunnels were evaluated, and a smart mining bolt design produced, based on the loading and environmental conditions present. Several material formulations were then proposed, melted, tested and evaluated against the relevant strength, corrosion and transformation criteria. A suitable material was selected and further tested. A working prototype bolt has been produced, and in situ tests of complete bolts, are scheduled to take place shortly. / Thesis (Ph.D.)-University of Natal, Durban, 2003.

The research objectives for this project were to explicitly define the anchor bolt corrosion problem in the state of Georgia and recommend action to the Georgia Department of Transportation. The bearing assembly of concern is the plate bearing assembly, in which carbon steel and/or bronze plates are anchored by either carbon steel or stainless steel anchor bolts. Inspection report data revealed that anchor bolt corrosion was ubiquitous for all environments in Georgia; the problem was reported for 27% of the steel girder bridges throughout the state. Based on a synthesis of the field investigations, bolt failure analyses, laboratory experimental testing, and review of GDOT inspection report surveys, the corrosion of carbon steel anchor bolts is caused universally by concentration cell corrosion. Other corrosion mechanisms of concern are galvanic and crevice corrosion, which are both enhanced by the current bearing design. Corrosion protection provided through zinc galvanization cannot sufficiently protect the carbon steel bolt for its entire service life. Corrosion potential and cyclic polarization data confirmed that ASTM Type 304, Type 316, Type 2101, and Type 2205 were protected from concentration cell and localized corrosion in the simulated bearing environment. Therefore, it is recommended that the stainless steel anchor bolts of these types be use in future designs and that the bolts should be electrically separated from all dissimilar metals using a Nylon or Teflon washer to prevent preferential corrosion of carbon steel. It is further recommended that the bronze lube plate should be eliminated entirely and that the bearing type should be a reinforced elastomeric bearing. Maintenance of existing sliding plate bearings should include regular cleaning by brushing away debris from the bearing surfaces, and bridges with carbon steel anchor bolts should be retrofitted to provide additional lateral restraint according to current maintenance procedures.