Tractors, as agricultural machines consisting of various interconnected assemblies, work in unison to perform specific functions and achieve desired outputs. Among these assemblies, the Hood Assembly, Firewall Assembly, Scuttle Assembly, Fuel Tank Assembly, Fender Assembly, Floor Panel Assembly, and Footstep Assembly are all produced through sheet metal fabrication. The components of these assembly are made from sheet metal and are joined together using various techniques, such as bolts, welds, and others.
The inherent characteristics of welding processes generally results in welded joints having lower fatigue strength compared to the individual parts being joined. Moreover, welds are commonly applied at geometric features or areas where the section changes within a structure. As a result, even in a structurally sound design, welded joints are often more vulnerable to fatigue failure. Hence, a comprehensive assessment of the durability of a welded structure requires placing considerable emphasis on a thorough fatigue evaluation of the welded joints.
Since industrialization, extensive research has been conducted on fatigue analysis of welded joints, leading to the development of various standards. Widely used standards in the industry include Eurocode 3, BS7608,among others.
In this paper, British Standard BS7608 and "Volvo Method," which are widely used for fatigue life prediction of thin sheet metal welded components are discussed. BS7608, which is based on the structural hot spot stress approach, determines stress by extrapolating it from the components to the weld toe, while excluding stresses from areas close enough to the weld toe that could be affected by the weld toe geometry. The "Volvo Method," developed at Chalmers University in collaboration with Volvo Car Corporation, calculates structural stresses at the weld toe using finite element-based nodal forces and moments along the weld line, along with an analytical expression for the stress at the weld toe. The fatigue life of welds in tractor sheet-metal assemblies is predicted using both methods. Testing of the assemblies is conducted in an NABL-accredited laboratory. A strong correlation between the predicted fatigue life and the results from laboratory testing is established and presented in this paper.