PSI - Issue 77

Vasco Gomes et al. / Procedia Structural Integrity 77 (2026) 559–566 Gomes et al./ Structural Integrity Procedia 00 (2026) 000–000

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3.4. Journal bearing element The other feature included in this model, in which were also used hydraulic components, was the journal bearing element. Throughout the servo press there are several of these components that are crucial to ensure the continuous operation of the press, more specifically of their rotating elements. One of these is the journal bearing located between the crankshaft and the rod, since it is subjected to a cyclic load from the stamping process. With the use of the plain journal bearing element from SimulationX®, factors such as lubrication, temperature, rotational speed, among others, can be determined. The journal bearing dimensions were directly extracted from the press CAD model, with the clearance being defined at 40 μm (in diameter), just as shown in following Table 4.

Table 4. Journal bearing element parameters. Parameter

Dimension

Unit

Fluid pressure (inlet)

60

bar

Bearing diameter Mean clearance

280 0.04 270

mm mm mm

Bearing width

Initial bearing temperature

60

°C

The four additional variables to give as input were: • bearing force: equal to the force acting on the connecting rod element; • angle of bearing force: based on the rod’s axial direction, since this is the load direction; • shaft rotational speed: calculated by the difference in the rotational speed between the crankshaft and the rod; • shell rotational speed: assumed as 0, as shaft speed accounted for the speed difference. 4. Results 4.1. Displacement and load (3D model) With the models defined, the simulations were conducted to analyse the impact on key features of the servo press. For the 3D model, an FMU control targeting 800 rpm (in the motor shaft), without stamping loads, and with both pneumatic counterbalance cylinders and contact elements were used. In Fig. 4-a) showcases the slide’s motion in x = x[1], y = x[2] and z = x[3]. The vertical (z) motion is sinusoidal (which comes from the crankshaft rotation) with a peak-to-peak distance of 315mm (twice the eccentricity of the crankshaft). While the motion in c-direction is negligible, a small displacement in y-direction ( ≈ 0.001 mm) appears, caused by a slight rotation of the slide around the x-axis, which is confirmed by its angular velocity in Fig. 4-b). This phenomenon may be aggravated over time due to wear and increase in guide clearance. Fig. 4-c) presents the force at the crankshaft-rod joint (on the right side). Forces in x-direction are negligible, while y- and z-components are derived from the joint’s rotation. Notably, the green curve (internal force in y-direction) represents the vertical load in this specific scenario.

Fig. 4. (a) Slide displacement; (b) Slide angular speed; (c) Crankshaft-rod joint internal force.