Theoretical Development of a Unified Wear Mechanism Map for Agricultural Machine Components Operating in Nigerian Lateritic Soil Environments

The abrasive wear behaviour of agricultural machine components in contact with Nigerian lateritic soils has not been unified into a theoretical wear mechanism map framework that accounts for the wide range of laterite mineralogical compositions, moisture contents, and particle size distributions across Nigeria's six geopolitical zones, leaving machine designers without a theoretically grounded tool for predicting component service life and selecting wear-resistant materials for specific soil environments. This research develops a unified theoretical wear mechanism map for agricultural implement components, including plough shares, harrow tines, and seed drill furrow openers, operating in the spectrum of lateritic soil environments across Nigeria. The theoretical framework integrates contact mechanics models of single-particle abrasion with bulk soil mechanics characterisations of soil-tool interaction forces and stress fields, producing dimensionless transition boundary functions separating micro-cutting, micro-ploughing, and surface fatigue dominant wear regimes as functions of normalised hardness ratio, contact stress, and mineralogical abrasivity index. The abrasivity index for 30 laterite soil samples collected across Nigeria's geopolitical zones is characterised through mineralogical analysis by X-ray diffraction, Cerchar abrasivity testing, and micro-indentation of individual mineral phases. Validation wear tests on steels of varying hardness and microstructure under controlled soil abrasion conditions confirm the theoretical boundary predictions within 15 percent. The resulting unified wear mechanism map constitutes an original contribution to the theory of abrasive wear and a practical tool for material selection in Nigerian agricultural machinery design. Keywords: wear mechanism map, lateritic soil, abrasive wear, agricultural machinery, contact mechanics.