Fastener Evaluation

The aircraft and its components designed with the integration of damage tolerance will tolerate a certain amount of damage and still remain intact until the damage is detected and repaired. 

Sections of a turbojet engine jointed together by bolts. 

Schematics of rivet joint and failure modes (a) riveted connection, (b) failure by pure shear, (c) bending, (d) cracking due to tension, (e) crushing, (f) shearing, and (g) tearing. 

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Fastness to Crocking. Crocking is defined as the transfer of color from the surface of a dyed fabric to another surface by mbbing. AATCC test method no. 8 is a method by which a colored test fabric swatch is fastened to the base of a Crockmeter and mbbed against a white crock test cloth under controlled conditions. Color transfer to the white cloth is evaluated by comparison with the AATCC Chromatic Transference Scale. A similar method, AATCC 116, uses a Rotary Vertical Crockmeter, which requires a smaller area of test fabric than the Crockmeter. 

Cross, J.N. Evaluation of metal fasteners performance in CCA-treated timber , 5th International Conference on Durability of Building Materials and Components, Brighton, (1990)... 

An additional component, fitted in the hose pipe between the pressure sensor and the suds container and fastened to the suds container, is capable of generating a pressure signal from the dynamic movement of the suds container. This is then sent via the pressure sensor to the microprocessor for evaluation (Fig. 5.57). 

This standard consists of 22 test methods, some of which are used in evaluating high-density rigid polyurethane foams for furniture applications. These methods are concerned with fastener-holding properties Lateral Nail Resistance Test, Nail Withdrawal Test, Nail-Head Pull-through Test, and Direct Screw Withdrawal Test. 

A major limitation of the simple method of determining the fastener load distribution is that the stiffness (elasticity and geometry) of the joined members is not explicitly taken into account. Another limitation of the simple method is that the specific elasticity properties of the analysed member is not considered when determining the fastener hole stress distribution. These limitations can effectively be overcome by adopting a numerical method such as the finite element method (FEM) for evaluation of the load distribution. 

Cellulosic materials can be mechanically fastened by a number of methods. However, their rigidity and propensity to have internal molding stresses must be carefully considered. The adhesives commonly used are epoxies, urethanes, isocyanate-cured polyesters, nitrile-phenolic, and cyanoacrylate. Only cleaning is required prior to applying the adhesive. A recommended surface cleaner is isopropyl alcohol. Cellulosic plastics may contain plasticizers. The extent of plasticizer migration and the compatibility with the adhesive must be evaluated. Cellulosics can be stress cracked by uncured cyanoacrylate and acrylic adhesives. Any excess adhesive should be removed from the surface immediately. 

Note to paragraph (e) The determination called for in this paragraph may consist of a check of the conditions that might foreseeably be in the enclosed space. For example, the cover could be checked to see if it is hot and, if it is fastened in place, could be loosened gradually to release any residual pressure. An evaluation also needs to be made of whether conditions at the site could cause a hazardous atmosphere, such as an oxygen-deficient or flammable atmosphere, to develop within the space. 

Salt Spray Testing Evaluation of Fastener Finishes Cyclic Corrosion Test... 

Over 30 other military (MIL) and Federal (FED) specifications include hydrogen embrittlement relief treatments. Structural elements, such as springs or fasteners, are tested directly under constant load, constant displacement or decreasing extension rates (slow-strain-rate testing) for evaluation of the effectiveness of treatments directed at amelioration of hydrogen embritdement. 

Paint/alloy evaluation (fastener insulation test)... 

Automobiles and mUitaiy equipment frequently are exposed to marine environments and road salt. Beach test sites are available, but simulations in the laboratory are convenient. The ASTM B 117, Method of Salt Spray (Fog) Testing, has been widely used for this purpose to evaluate rusting, pitting, and SCC. Martensitic stainless steels and maraging steels have been exposed to salt spray (and other NaCl environments) to evaluate resistance to SCC prior to use in military equipment and fasteners. Ferritic and austenitic stainless steels have been tested to evaluate resistance to rusting prior to use in automotive applications. 

Mechanical fasteners introduce stress concentration which must be carefully evaluated by the designer. 

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