In recent years, car manufacturers and various industrial equipment manufacturers have accelerated electrification and energy saving, which requires rolling bearings used in these fields with lower friction torque and higher rotational speeds. In addition, the operating environment of bearings is harsher than before, such as rapid acceleration or deceleration and complex load fluctuations, therefore, durability and performance in the above-mentioned operating environment must be guaranteed. Bearings are being used more and more under never-before-seen conditions, and at the same time, in order to respond to customer requirements in a timely manner, the lead time for bearing design needs to be shortened. Due to these changes in the internal and external environment, a great deal of attention is focused on the development process utilizing analysis/simulation compared to the conventional development process focused on prototyping and experimentation. In response to this environmental change, JTEKT independently developed the Shafting Analysis Program (S.S.A.P.) as software to support bearing design. The main functions of S.S.A.P. are shown in Figure 1. S.S.A.P. allows modeling at the element level through multiple shafts, gears and bearings. At the same time, bearing life, internal load distribution, friction torque and other bearing internal load states can be studied through bearing analysis that considers factors such as power flow, housing stiffness, shaft stiffness, etc. Due to the above background, people pay more attention to the damage caused by impact and the internal performance of bearings under complex working conditions. These situations cannot be understood using current static analysis, and more and more situations require dynamic analysis. Therefore, an important factor in bearing design is to understand the performance of the bearing under actual operating conditions at the initial design stage. Due to the increasing demand for bearing analysis using dynamic analysis (simulation), the Bearing Dynamics Analysis System (S.S.A.P./MBD) was developed as a new function of S.S.A.P. This article provides an overview of S.S.A.P./MBD and an example of usage. Fig. 1 Main functions of S.S.A.P 1. System overview 1.1 Analysis method S.S.A.P./MBD is a 3D dynamic analysis system for bearing modeling based on the concept of multi-body dynamics (MBD). For a mechanical system composed of multiple parts, the equation of motion of each part is established in MBD, which can calculate the interaction between parts that are difficult to measure, and factors such as the displacement and velocity of a single part. The analysis method of S.S.A.P./MBD is shown in Figure 2. Fig. 2 Analysis method of S.S.A.P./MBD First, the independent state vector of each part including the bearing is given, that is, next, the force and moment acting on each part in this state are calculated. An example of a typical interaction is the contact force between parts. Contact forces are calculated using the Hertz contact theory, where geometric interference is derived from the positional relationship of individual parts in 3D space, and the amount passing through the oil film is defined as an elastic approximation. In this way, equations of motion are established to solve for the forces and moments acting on each part. Equations (2) and (3) are examples of equations of motion for rolling elements. As shown in equations (2) and (3), the forces and gravity generated by the liquid and lubricant, such as the interaction of each part, rolling viscous resistance and mixing resistance, are considered, and the 6-degree-of-freedom flatness of each part is established. Equations of motion and rotation. The equation of motion thus established is solved by numerical integration, and the state vector of the next step is obtained. From this point on, by repeating the cycle, the state vector of each part at each moment is obtained and bearing performance is predicted. 2.2 Analysis flow/function The basic flow of bearing research using S.S.A.P./MBD is shown in Figure 3. Fig. 3 Analysis flow First, static analysis was carried out using the shafting model simulating the target product to understand the axial and radial loads acting on the studied bearing, as well as the clearance change and raceway deformation caused by meshing. The data obtained from the static analysis is used as the input data for the kinetic analysis, and the event time and other data are also input in the kinetic analysis. In addition, in order to set the friction factor between the rolling elements and the raceways, the relationship between the slip ratio and the friction factor (drag curve) with respect to the peripheral speed at different pressures using a typical lubricating oil was measured. A database is thus established to enable automatic setup. An example of dragging a curve is shown in Figure 4. Fig. 4 Drag curve In addition, for the contact damping coefficient between parts, a database was established by combining various materials, oils and greases through independent contact damping tests and simplified data entry. The system supports the bearing types listed in the catalogue, and in addition to more accurate calculation of raceway roundness deformation and edge contact (Fig. 5), it can also analyze factors that are not easily analyzed by general-purpose software, such as various bearing loads as analysis conditions and Fluctuations, skew, excitation and other operating conditions. After the analysis is completed, the bearing performance will appear on the result processing window in the form of animation analysis, and the calculation results of impact load and friction effect can also be displayed in animation to provide data support for bearing design. The result processing window of S.S.A.P./MBD is shown in Figure 6.