Numerical investigation of the effect of harrow tine’s geometry on fatigue life

Harrow tines experience large deflections due to varying soil conditions, leading to fatigue failure through cyclic loads. Selecting the appropriate coil diameter, pitch, and number of coils is crucial for designing harrow tines that can withstand these deflections. The aim of this research is to develop new harrow tine designs that offer improved sustainability compared to conventional harrow tines used in the Canadian prairies. Nine double helical torsion spring harrow tine designs were developed, differing in coil diameters, pitch, and number of turns, while keeping the wire diameter constant. A comparative analysis was conducted, considering fatigue life, failure criteria, and stress distribution patterns assessed through Finite Element Modeling (FEM). Additively manufactured 38% scaled harrow tine prototypes underwent load-bearing tests using identical load sets of 20, 50, 100, and 200 grams. The 2T3D2P, 1T4D2.5P, and 2T4D2.5P models emerged as reliable harrow tine designs with higher fatigue life of 14,115, 14,438, and 27,618 cycles compared to the frequently used conventional harrow tine’s 7533.87 cycles. Coil diameter has a preferential influence on achieving higher fatigue life, overshadowing the effects of pitch and the number of coils. Furthermore, models with larger coil diameters displayed greater flexibility against the defined weight loads, as observed in the load-bearing tests.