Linear guideways play a crucial role in determining precision of machine tools. Understanding their dynamic response is essential for objectively controlling their behavior and performance in operation. Due to highly loaded lubricated contacts, mixed-elastohydrodynamic regime is dominant. The mixed-elastohydrodynamic film maintains the coupling between horizontal degree of freedom (feed velocity) and vertical degree of freedom (loading direction). This paper presents a novel tribo-dynamic solution for linear guideways, taking in to account the lubricant effects and coupling between horizontal and vertical degrees of freedom. An analytical tribology model is used implicitly within the dynamic model. For in-depth tribological quantities including pressure and film thickness distribution, an explicit full numerical solution for mixed-elastohydrodynamic is utilized. Results show that the coupled solution of vertical and horizontal degrees of freedom taking in to account lubricated contacts is essential. It is shown that at moderate and light loads, the effect of this coupling and presence of lubricant is more pronounced.

Guideways accommodate tool or workpiece translations, and their dynamic behavior and associated sliding effects have great impact on the precision, stability, and performance of the machine tool. During machining, guideway rollers experience oscillatory excitations because of cutting forces, which necessitate considering their pre-sliding behavior along with the sliding characteristics to compensate for the associated tracking errors using the position control system. This study considers friction effects in pre-sliding and sliding regimes of lubricated linear roller guideway systems to provide an accurate dynamic model of the machine tool element. To model the dynamic characteristics of frictional contact in the lubricated linear roller guideway, the LuGre model, commonly used in the machine tool positioning control system to estimate the compensating drive force, is modified considering the roller-raceway contact physics and the lubricant film dynamics. The proposed model also includes coupling effects between normal and tangential forces in the contact interface. Experimental studies were performed on a lubricated linear roller guideway to verify the performance of the presented modified LuGre model. In the experimental observations, the dynamic behavior of friction in the lubricated linear guideway is well illustrated. A comparison of the experimentally measured data and proposed modified LuGre model predictions shows the model can accurately predict dynamic behaviors of the frictional contact interface.

This paper presents an experimentally validated numerical approach linear roller guideways considering coupled vertical and horizontal (feed) motions and taking into account lubricant starvation. The inlet starvation is considered by incorporating potential flow method. Results show that starvation has pronounced effect on the lubricant film thickness, friction, and applied load on contact by up to 32%. Localised pressure values may vary by up to 100%. The severity of starvation effect is frequency dependent. It is also revealed that the starvation effect can be controlled by the amount of preload on linear guideway.

Model updating techniques are used to update the finite element model of a structure, so that updated model can be predicted the dynamic behavior of an actual assembly structure more accurately. Most of the model updating techniques neglects damping and so amplitudes of vibration at resonance and antiresonance frequencies cannot be predicted by using of these updated models. In dynamic design of structures predicting of these properties is necessary. This paper presents a new technique to create an accurate finite element (FE) updated model of complex assembly structures consisting of substructures and real joint by considering damping of them. Given the fact that modal testing of real joints (such as bolt with some washers) are almost impossible. The updated model of assembly structure is obtained in four steps. In the first step, mass and stiffness matrix of substructures, joint and assembly structure are updated using modal data and Eigen-sensitivity approach. In the second step, damping of assembly structure is identified using complex modal data and updated mass and stiffness matrices which are obtained in first step. In the third step, the effect of damping of joint on frequency response functions (FRFs) extracted from updated model was shown. In the forth step, damping matrix of joint is updated by using FRF-based model updating method and finally damped updated model of assembly structure compared with measured data.

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