Kyntöauran rakenteiden kehittäminen mitatun kuormitusaineiston perusteella

In this study different fatigue design methods of welded and bolted joints for the agricultural machine based on the strength of materials and standards was applied. The loads that affect the structures of the plough were measured with the strain gauge method.  Also the behaviour of the structures during conventional use was analyzed. Based on the measured loads the lifetime of original components made from S355-steel was evaluated. The body of the plough was redesigned using S700-steel and the fatigue design for the components was carried out based on the measured loads. The FE-method was used on stress calculation and components design. The components of the welded joints had to be reshaped to reach the permissible stress level. In the fatigue design, the simplified S-N curve, endurance limit reduction coefficient and stress concentration factors according to strength of materials were used. In the fatigue design of the welded joints, the design was carried out based on the tabulated values of characteristic fatigue strength and structural details. As a result of the study, it was found that the geometry and post-treatment have the greatest impact on the fatigue strength of the welded joint. Furthermore, it was found that the endurance limit of the un-notched material increases when the tensile strength increases. However, the endurance limit of the welded joint does not increase in the same proportion. Also it was found that the total mass of the structure decreases while the fatigue strength increases.