PSI - Issue 82

A.T. Andreasen et al. / Procedia Structural Integrity 82 (2026) 146–152 A.T. Andreasen et al. / Structural Integrity Procedia 00 (2026) 000–000

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Testing is performed to facilitate the development of the load estimation framework which is based on strain gauge measurements. In total, 11 uniaxial strain gauges and a single rosette gauge are placed on the lifting arm to measure the strains occurring during various operational conditions. The rosette consists of strain gauges 4, 5 and 6. Thus, a total of 14 strain gauge channels has been used. The locations of the gauges are shown in Fig. 2(a) and Fig. 2(b). The gauges are 3 mm 3-wire epoxy coated T2. The strain gauge measurements were recorded using two Dewesoft Iolite modules, which were built into a data acquisition box mounted on the tractor. The sampling frequency used was 200 Hz. The data were processed afterwards using the DewesoftX software and MATLAB. The data-acquisition box can be seen in Fig. 3.

Fig. 3. Data-acquisition box.

The purpose of the field testing is to obtain strain gauge measurements that can later be used to establish the loading occurring in the lifting arm. This is further explained in Section 3 and 4. To obtain relevant and realistic loads, a total of 10 tests were performed with various operating modes of the mower. The mower unit primarily operates in two different positions; it can be lowered into working position which is used for field work, or it can be lifted for transport. The tests were chosen to reflect these operating modes at different speeds and on different roads. The full set of tests performed are given in Table 1. As can be seen from the table, the first test was a work test conducted in a field with the mower in working position, i.e. mowing. The remaining tests were conducted as transport tests with varying parameters such as speed and road type, to establish relevant statistical data. Before each test, the mower and lifting arm were positioned in either the working- or transport position depending on the test type, and the strain gauges were zeroed. Thus, the effect of gravitational loading on the lifting arm has been neglected in the measurements. As the purpose of the developed load estimation framework is to estimate the fatigue loading occurring on the lifting arm and subsequently use it for fatigue assessment of the welds, the mean stress effects caused by gravitational loading can be neglected due to the expected residual stresses in the weld (Hobbacher and Baumgartner (2016)). 3. Finite element model A digital twin, consisting of a high-fidelity FE model of the lifting arm, has been created in earlier work (Larsen et al. (2024)). In that work, the FE model was calibrated using a simple testbench to accurately estimate the strains occurring due to vertical and horizontal loading on the lifting arm. The result was a highly accurate FE model. The