In fatigue design for bolts, whether in stretch-stretch or stretch-compression applications, the decisive factor is to minimize the value of the alternating stresses and keep them within the limits that the bolt can withstand.
Material selection: Protective surface coatings or corrosion-resistant fastener materials prevent corrosion associated with fastener breakage. The protective barrier layer comprises a phosphate treated or rustproof oil of carbon and alloy steel fasteners.
Due to the lubricity of the coating, the wear of the stainless steel fasteners can be reduced and the service life of the fasteners can be extended. These coatings are applied to the surface of the fastener prior to installation or applied to the entire joined surface after installation. Coatings also include the use of rare metals as coatings such as blessed, zinc or tin to plate fasteners, while silver plating is commonly used in high temperature environments.
Corrosion-resistant fastener materials include various grades of stainless steel, superalloy steel, non-ferrous-alloy coffee brass, Chin and aluminum, and materials requiring high strength and stress corrosion cracking. These materials are not resistant to corrosion in every environment, and materials that are resistant to special environments.
When selecting materials, designers should keep in mind that thread stripping can produce the same catastrophic results as bolt breaks.
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