## 1 Introduction
Furthermore, MR devices have the capability of substantially improving surface finish and reducing tool wear in hard-turning operations [17]. The design of the MR damper device can be assisted by Finite Element Method simulation because it can identify the magnetic field magnitudes needed when located in a tool-holder [18]. It is interesting to point out that most implementations of MR damper devices in machining operations were mainly oriented to boring or turning operations. This could be explained since the MR damper devices could be easily attached to the tool-holder in lathe machines. However, its implementation in milling operations is very infrequent, but there have been a few attempts to apply MR technology to increase the damping of the workpiece. For instance, [PERSON] et al. [19] demonstrated stability improvement in the thin-wall milling process. The most common off-line approach is focused on the calculation of chatter-free cutting parameters based on the study of dynamics stability [20]. Special milling tools such as spherical or bull-nose tools are preferred for thin-floor machining in order to obtain a certain curvature between floors and walls; however, the geometry of the cutting edge has a strong influence over the forces in the tool axis direction, which typically coincides with the direction of the low-dynamic stiffness of thin floors. Since thin-floor dynamics are inherently complex due to the modal parameter variation that depends on the tool-workpiece location, three-dimensional stability diagrams for bull-nose milling tool cutting operations were calculated for identification of the location at which the spindle speed of the cutting tool is a chatter-free tuning interval value [21]. Of course, the accuracy of the location of stability zones depends on predicting the magnitude values of cutting forces. In this sense, [PERSON] et al. [22] developed a method to predict the cutting force of any cutter geometry from orthogonal cutting data. The accuracy of the predicted forces was assessed with collected experimental data. The same method was also applied to ball-end milling tools [23]. By fitting pressure and friction coefficients on the rake and flank contact surfaces of ball cutters, [PERSON] et al. [24] predicted with good accuracy the acting cutting forces in Cartesian directions. [PERSON] [25] described the chip regeneration mechanism in three directions with a bull nose. The stability lobes were predicted in the frequency domain and verified experimentally. Other methods to predict stability are based on the time-domain discretization. For instance, [PERSON] et al. [26] proposed the Enhanced Multistage Homotopy Perturbation Method to compute stability lobes in one degree of freedom mimicking thin wall machining. Later, [PERSON] et al. [27] proposed stability colormaps based on time-domain simulations of peripheral milling in thin-walled parts with barrel cutters. Regarding tool path planning in thin floors, [PERSON] and [PERSON] [28] proposed a tool path strategy that provided extra stiffness by leftover material in the corners; however, this strategy is limited for large areas consisting of mostly thin floors. To implement reliable solutions for the machining operations of thin-floor components, two aspects need to be considered. Firstly, high accuracy is required for the determination of the modal parameters and the associated acting cutting forces for effective and reliable stability prediction. Secondly, it is important to acknowledge the shortcomings of active or semi-active damping techniques, including excessive setup times and customized designs that are only suitable for some specific machine processes. The use of MR fluids still is not mature in cutting operations and requires more investigation if one wants to enhance its industrial application. Therefore, the aim of this work focuses on investigating how a semi-active MR damping device can influence the dynamics of cutting operations in thin-floor components.