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Argatov I.I.,University of Mondragon | Argatov I.I.,Research Institute of Mechanical Engineering Problems | Gomez X.,University of Mondragon | Tato W.,University of Mondragon | Urchegui M.A.,Orona Sa
Wear | Year: 2011

The Archard's wear law based mathematical model of fretting wear between wires is applied to elaboration of the experimental results of the previously reported study of the wear degradation in a stranded steel wire rope subjected to cyclic bending over a sheave. It is shown that the dependence of the coefficient of wear on the contact pressure should be taken into account to explain the observed increase of the wear severity with a reduction of the shave diameter. Accordingly, a mathematical model of fretting wear based on the Archard-Kragelsky wear law was developed, and an example of calibration of the wear law parameters was given. Some implications to fatigue life estimations for stranded wire ropes are discussed. © 2011 Elsevier B.V.

Cruzado A.,University of Mondragon | Hartelt M.,BAM Federal Institute of Materials Research and Testing | Wasche R.,BAM Federal Institute of Materials Research and Testing | Urchegui M.A.,Orona Sa | Gomez X.,University of Mondragon
Wear | Year: 2011

The wear behaviour of thin steel wires has been analyzed under oscillating sliding conditions in crossed cylinders contact geometry. The focus of this analysis was the influence of the crossing angle between the wires on the wear. The wires used had 0.45. mm in diameter and the material was cold-drawn eutectoid carbon steel (0.8% C) with a tensile strength higher than 2800. MPa. Two different types of tests were carried out, the first one representing the influence of the crossing angle for a constant load and the second one representing the influence of the crossing angle with constant contact pressure. In the first type of tests it was seen that as the contact angle decreases the contact pressure decreases too and hence less energy specific wear resistance is observed. As a consequence less wear is produced, thus increasing the life of the wires. In the second type of tests it was seen that with constant contact pressure but different crossing angles, nearly the same energy specific wear resistance was observed. This points at an identical wear behaviour in both type of tests but with a running-in and a steady state period as two different wear periods. The tests showed that the running in period may play an important role in the overall wear particle generation and hence the wear occurring in the steady state period is rather mild. © 2011 Elsevier B.V.

Arrasate X.,University of Mondragon | Kaczmarczyk S.,University of Northampton | Almandoz G.,University of Mondragon | Abete J.M.,University of Mondragon | Isasa I.,Orona Sa
Mechanical Systems and Signal Processing | Year: 2014

Vertical vibrations affect passenger comfort during an elevator travel. This work presents the results of a study of vertical vibrations caused by torque ripple generated at the elevator drive system. Tests are performed on a 1:1 roping configuration laboratory model; the acceleration response at the suspended masses and at the drive machine, the machine shaft velocity and the three phase current intensities supplied to the machine are measured during several travels. The machine torque is estimated from the current intensities. A non-stationary model of an elevator is then developed to simulate the acceleration response. The model accommodates the drive system dynamics. The machine parameters are computed by means of the Finite Element Method simulation software FLUX. FLUX computes the amplitudes of the torque ripple and the radial forces at the air-gap. As the torque ripple computed by FLUX is smaller than that torque estimated from the machine currents, the latter is added as a perturbation to the controller generated torque. With respect to the car-counterweight-sheave-ropes assembly a five degree-of-freedom lumped-parameter model (LPM) and a novel distributed-parameter one (DPM) are developed. The elevator dynamics represented by the DPM is described by a partial differential equation set that is discretised by expanding the vertical displacements in terms of the linear stationary mode shapes of a system composed of three masses constrained by the suspension rope. The models are implemented in the MATLAB/Simulink computational environment and the system response is determined through numerical simulation. It is shown that the LPM forms a good approximation of the DPM. The frequency content of the computed and measured accelerations demonstrates that the elevator car vibrates at frequencies generated at the machine, especially when they are close to the system natural frequencies. © 2013 Elsevier Ltd. All rights reserved.

Bartolome L.,University of Mondragon | Aurrekoetxea J.,University of Mondragon | Urchegui M.A.,Orona Sa | Tato W.,University of Mondragon
Materials and Design | Year: 2013

Thermoplastic polyurethane elastomers under cyclic loading-unloading conditions exhibit inelastic effects, mainly stress softening, hysteresis loss and residual strain. In order to discuss the sensitivity of these effects to deformation state (uniaxial tension and pure shear) and to work conditions (maximum strain, strain-rate and stretching direction), this study is concerned with inelastic effects of an extruded thermoplastic polyurethane elastomer when is subjected to loading-unloading cycles. Based on the behaviour of inelastic effects under both tensile conditions, the present work shows that stress softening and residual strain are sensitive to deformation state only when the maximum strain reached causes permanent set. Furthermore, the hysteresis loss shows an independent behaviour depending on maximum strain. Finally, the behaviour of the hysteresis loss and the residual strain is isotropic for the extruded thermoplastic polyurethane elastomer. © 2013 Elsevier Ltd.

Cruzado A.,University of Mondragon | Urchegui M.A.,Orona Sa | Gomez X.,University of Mondragon
Wear | Year: 2012

Fretting wear is one of the main degradation mechanism produced in steel wire ropes. The experimental characterization of this phenomenon is economically costly and too much time consuming. With the aim to reduce this disadvantage, an optimized methodology for wear scars simulation has been developed. This paper presents the two relevant aspects of this methodology, which consist of the reduction of computational time and the validation of the wear scar with respect to the experimental data. This methodology has been implemented via the commercial FE code ABAQUS in a 90° crossed-cylinders configuration. With respect to the reduction in computational time the effect of mesh size, simulation wear increments per fretting cycle and cycle jump technique are studied. An optimum mesh size for minimal computational time that should be in the range from 3% to 4% of the final longitudinal wear width is defined. On the other hand, an optimum value of 40 increments per fretting cycle and 100 fretting cycles with the corresponding cycle jump is enough to simulate the wear scar in any conditions with differences in dimensions less than 4%, in comparison with more refined simulations. The results of the optimized model are validated with respect to the experimental data obtained by the tests carried out in a small sliding amplitudes tribometer for the same crossed cylinder configuration. The validation consists of three steps: wear scar dimensions, wear scar depth and wear scar volume. This procedure demonstrates that within an error of 10% this optimized method predicts accurately the wear scars. © 2012 Elsevier B.V.

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