Mathematical model and methodology of express assessment crisis-deformed state of the machine frame for the care of forest crops

In the development of forestry machines and tools, the finite element method (FEM) is actively used to calcu-late the effect of external loads on the strength and frequency characteristics of structures. As a rule, expensive com-mercial software packages ANSYS, LS-DYNA, etc. are used for this. At the early stages of design, checking unsatisfac-tory solutions with complex software packages is not advisable. The authors have developed a method for expressly assessing the stress-strain state (SSS) of tested brush cutter designs, working directly with a geometric model created in a computer-aided design (CAD) system and allowing the engineer to obtain strength and rigidity indicators that are im-portant for the technological process. The proposed method includes: import of a CAD model in STL format; voxeliza-tion and construction of a regular HEX8 grid with a controlled step h; setting Dirichlet conditions in the embedment zone and the equivalent Neumann load through the distributed pressure on the loaded areas; assembly and solution of a linear elastic problem; calculation of stress fields and von Mises equivalent stresses, as well as assessment of maxi-mum displacements; export of results for subsequent analysis. The express method is demonstrated using a brush cut-ter beam as an example. It was found that under the given loads F=3000 N, the maximum stress in the beam L=500, 40x40x3 mm was 268 MPa, and the yield strength was 220 MPa. The method allows to reject this beam and replace it with a new one, with parameters L=500, 80x80x3 mm, the resulting stress was 58.3 MPa. Thus, the unsatisfactory op-tion was excluded even before the difficult multiphysical calculations.. The presented method is intended for prelimi-nary rejection of weak solutions to reduce the cost of further development of forestry machines. The scope of applica-tion is large-sized mechanical units of forestry machines and tools.