PSI - Issue 82

A.T. Andreasen et al. / Procedia Structural Integrity 82 (2026) 146–152

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A.T. Andreasen et al. / Structural Integrity Procedia 00 (2026) 000–000

Alternatively, strain or stress fields can be measured directly on the structure (Carpinteri (2017)). However, these methods have limitations: PSDs lose time-domain information, which is critical for identifying non-proportional stress states, and direct strain/stress measurements, are restricted to the specific locations where sensors are placed. In this paper, a new framework for determining the loading occurring in a lifting arm of a mower, as shown in Fig. 1, is presented. The framework builds on a digital twin of the lifting arm developed in (Larsen et al. (2024)), combined with strain gauge measurements from field tests. By using the digital twin, a so-called influence matrix is constructed to describe the relationship between finite element (FE)-based loading conditions and resulting strains. Correlating this matrix with actual field measurements enables the estimation of FE-accurate loading conditions. The correlation uses the simple linear least squares method (LLSM), making the approach straightforward to implement. The framework is described and validated in this paper based on a Kverneland mower, and the results show that the estimated loading is highly accurate, as seen from the comparison between measured and FE predicted strains. The predicted loading can subsequently be used for highly accurate fatigue life estimation everywhere in the lifting arm and as the loading is established in the time-domain, accurate analysis of e.g. non-proportionality effects can be made. 2. Experimental setup A lifting arm attached to an agricultural disc mower has been used as the basis for the developed load estimation approach. The mower lifting arm can be seen in Fig. 1(a) as a picture and in Fig. 1(b) as the corresponding FE model. As the figures illustrate, the lifting arm has changing geometry and cross-sectional area over its length and consists of several welded connections. The mower unit is connected to the lifting arm using a link system. For the development of the load estimation framework, only the lifting arm is considered, as it mainly transfers the loads from the mower unit to the hitch connection at the tractor.

Fig. 1. (a) Picture of mower with lifting arm; (b) FE model of lifting arm.

Fig. 2. (a) Strain gauge placement from the front; (b) Strain gauge placements from the back.