## 1 Introduction  
Reducing mass is of great importance in the automotive and aerospace industries, as it directly affects fuel consumption, which leads to reductions in cost and environmental pollution [1, 2]. Therefore, in this work, the effects of a specially designed lightweight cellular lattice structure of a gear body were experimentally analyzed by measuring the strains in the gear at various positions and in various directions. A gear with a lattice body structure was fabricated by engaging 3D printing, also known as Additive Manufacturing (AM). For this process, a mechanically strong and comparatively lightweight material, i.e., a Ti-6 Al-4V alloy, was used. This choice was made based on the expectation that, under certain circumstances, the use of an optimal design, AM technology, and advanced materials may offer notable benefits in decreasing energy consumption and carbon emissions [3]. In this context, reducing mass by adopting cellular lattice structures looks particularly important. Moreover, apart from mass reduction, lattice structures may well lead to more favorable dynamic behaviour of the gear. This could be potentially exploited in reducing noise and vibration during gear meshing. As gears are typically used to transmit power, i.e., torque, from one shaft to another, the reducing mass, vibration, and noise is crucial, especially in the automotive and aerospace industries [4; 5]. Gears mostly operate in such a way that they are loaded by time-varying and mostly periodic loads, even during steady-state operation. The time variation of loading stems from the impacts, variable location of contact points, and changing number of teeth currently engaged in meshing [6; 7; 8]. This is a permanent source of dynamic loading and also generates vibrations. Much research on reductions in vibration, as well as dynamic loads of gears, has been mainly focused on modifying the tooth profile [9; 10; 11]. As it currently looks, profile modification may be helpful but cannot completely remove dynamic loading, which designates the gear as a permanent vibration generator. Several studies have focused on the gear body to investigate its dynamic response [12; 13]. For example, in some studies, holes were deliberately placed in the gear body, and a finite element model was developed to investigate the impact of these changes. The dynamic behavior of the gear was then assessed to determine the effectiveness of the structural changes. Another strategy employed by some authors [14; 15] involves incorporating functional features into the gear-body design. For example, adequately designed holes within the gear body can be filled with a suitable powder. Such a design could reduce the propagation of vibrations to some extent. In the context of mass reduction, the gear body is mainly addressed to reduce the total mass of the gear. However, such a mass reduction may easily make the body much weaker, as reflected by overly increased strains and stresses [16]. To prevent this, it is necessary to take an innovative approach by incorporating a lightweight structure into the gear body. In this way, it might be possible to reduce both the mass and vibrations while preserving a sufficient load-carrying capacity of the gear. Such lightweight structures of the gear body may be expected to reduce vibration transmission due to their flexibility in the tangential direction. The use of a lattice structure could be a promising solution to significantly reduce the material while maintaining sufficient strength, in addition to reducing vibrations. Lattice structures are gaining popularity due to the growing demand for sustainable products that minimize material usage while maintaining high mechanical performance. They are commonly utilized to increase mechanical strength-to-weight ratios, improve energy absorption, and optimize material efficiency in various engineering applications [17; 18]. In addition, the geometry of such a lattice structure must be fine-tuned to ensure the absence of stress concentrations and low stress levels.