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# Tetrahedral mesh used to model the acoustics in tractor cabin interior. The cabin structure was mostly steel but the windows are glass and the acoustic domain consists of air. The solid do- main W s was modelled to be composed of two parts, i.e., metallic skeleton and glass windows. The skeleton part was assumed Pa, Poisson’s to consist ratio of n steel = 0 . 3, with and Young’s density Modulus r s = 7850 E = kgm 2 · 10 11 3 . Pa, The n material = 0 . 161, parameters and r s = for 2190 the kgm windows 3 . The are structure E = 6 . 5 is · 10 sup- 10 ported rigidly at the lower corners. The inside of the cabin W f is modelled as air having sonic velocity c = 343 m/s and density r = 1 . 2 kgm 3 implying the wavelegth l = 3 . 18 m. The ceiling is modelled as an absorbing boundary with the value of absorption coefficient b = 0 . 04.

Source publication

Computational acoustical models allow automated optimization of tractor design with respect to acoustic properties, which could speed up significantly the design process of tractor cabin prototypes. This article gives insightful prospec-tives to the tractor design process by considering modern computational acoustics technology. Mathematical formul...

## Context in source publication

**Context 1**

... n s and n f are the unit normal vectors pointing out- ward from the solid and the fluid domain, respectively. Mod- els related to Eqs. (2)–(6) can be used in modelling various applications such as concert halls, loudspeakers, noise barri- ers, mobile phones, and acoustic materials. For existence and uniqueness of the solution for structural-acoustic problems we refer to [ 11]. Another significant subject, alongside with mathematical modelling and method development, is to test and tailor the existing simulation methods and software to get rid of the time-consuming handwork between the simulation steps from geometry modelling to optimization results. A typical method to reduce the size of the computational problem in three-dimensional vibro-acoustical simulations is to use combinations of boundary and finite elements. There, finite elements are used to model elastic vibrations in the cabin structure, which is coupled to the boundary element method solution of the air volume acoustic pressure field in- side the cabin. In [9], this was done to a tractor cabin by using Sysnoise software. In [5], acoustical optimization of construction machinery cabin is considered with combination of ModeFrontier, ANSYS, and Sysnoise software packages. There, ANSYS is used for the structural, Sysnoise for acous- tical simulations, respectively and ModeFrontier is used as an optimization backend which communicates with other soft- ware. Recently, the pure FEM approach is used with the ANSYS program in [19] for simulating the noise in a bus passenger compartments. In [17], the finite elements simulations were carried out with the direct inversion method in ANSYS. The results were compared to the solutions obtained by structural- acoustic problems by Krylov-based model order reduction techniques discretized with FEM. Passive noise control op- timization was discussed in [12]. In this paper, we present one choice for using commercially available software tools. The basic setting is similar to the ap- proach introduced in [9], but we have chosen to use a different software. The motivation for the choice of the software was to make the data transfer between CAD software and simulation and optimization tools easier. The intention is to make a step towards better automatization in digital product development including design for manufacturing processes and numerical optimization for improving the product properties. The 3D geometry that we used in numerical experiments was based on a tractor CAD model by Valtra Inc. The original CAD model was simplified by removing small details from the original model with CATIA V5 CAD software. Further preprocessing was done in ANSYS DesignModeler 12.1. Meshing and computing was done in ANSYS Mechanical 12.1. Triangular shell elements were used in the elastic struc- ture of the cabin (see Fig. 1). The interior of the tractor cab- in, presented in Fig. 2, was meshed using tetrahedral finite elements. (see, e.g., [6, 20]). The parts were connected to- gether with bonded connections. The two-way fluid-structure interaction works so that the fluid nodes at the interface have translational degrees of freedom and are bonded to the ...

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