Development of a Modular Fretting Wear and Fretting Fatigue Tribometer for Thin Steel Wires: Design Concept and Preliminary Analysis of the Effect of Crossing Angle on Tangential Force

This work presents the design of a modular ad-hoc fretting fatigue and fretting wear tribotester for thin steel wires. The working principles of the diffrent modules are described, such as the displacement and contact modules. Preliminary studies for understanding the effect of crossing angle between wires on tangential force measurement has been carried out on 0.45 mm diameter cold-drawn eutectoid carbon steel (0.8% C). The results show that due to the developed wear scar geometry for high crossing angles there is a non-Coulomb behaviour that is not seen for low crossing angles

Critical analysis of the suitability of surrogate models for finite element method application in catalog-based suspension bushing design.

This work presents a critical analysis of the suitability of surrogate models for finite element method application. A case study of a finite element method (FEM) structural problem was selected in order to test the performance of surrogate algorithms. A simple design of experiments (DoE) approach, based on 1D kernel density estimations, is employed to construct a representative pool of real FEM simulations, which becomes the dataset for five different surrogate models, two linear and three non-linear, whose most relevant hyperparameters were tuned (model selection). Results in a real bushing case study show that surrogate models can accurately mimic FEM simulations outcomes, in this case four types of stiffnesses (axial, radial, torsion, and cardanic)

On the Role of a ZDDP in the Tribological Performance of Femtosecond Laser-Induced Periodic Surface Structures on Titanium Alloy against Different Counterbody Materials

Laser-induced periodic surface structures (LIPSS, ripples) with ~500–700 nm period were produced on titanium alloy (Ti6Al4V) surfaces upon scan processing in air by a Ti:sapphire femtosecond laser. The tribological performance of the surfaces were qualified in linear reciprocating sliding tribological tests against balls made of di erent materials using di erent oil-based lubricants. The corresponding wear tracks were characterized by optical and scanning electron microscopy and confocal profilometry. Extending our previous work, we studied the admixture of the additive 2-ethylhexyl-zinc-dithiophosphate to a base oil containing only anti-oxidants and temperature stabilizers. The presence of this additive along with the variation of the chemical composition of the counterbodies allows us to explore the synergy of the additive with the laser-oxidized nanostructures

On the Role of Contact and System Stiffness in the Measurement of Principal Variables in Fretting Wear Testing

In this work, the role of the contact stiffness in the measurement of principal variables in fretting wear tests is assessed. Several fretting wear tribometers found in the literature, including one developed by the authors, are analysed and modelled using numerical methods. The results show the importance of the tribosystem stiffness and tangential contact stiffness in the displacement sensor calibration and in the correct numerical modelling of fretting wear tests, especially for flat-to-flat contact configuration. The study highlights that, in most cases, direct comparisons between fretting results with severe wear obtained with different tribometers cannot be performed if the contact stiffness is not properly considered during the development of the experiments

An ad-hoc fretting wear tribotester design for thin steel wires

Steel wire ropes experience fretting wear damage when the rope runs over a sheave promoting an oscillatory motion between the wires. Consequently, wear scars appear between the contacting wires leading to an increase of the stress field and the following rupture of the wires due to fatigue. That is why the understanding and prediction of the fretting wear phenomena of thin wires is fundamental in order to improve the performance of steel wire ropes. The present research deals with the design of an ad-hoc fretting wear test machine for thin wires. The test apparatus is designed for testing thin wires with a maximum diameter of 1.0 mm, at slip amplitudes ranging from 5 to 300 μm, crossing angle between 0-90º, and contacting force ranging from 0,5 to 5 N. The working principle of displacement amplitude and contacting force as well as the crossing angle between the wires are described. Preliminary studies for understanding the fretting wear characteristics are presented, analysing 0.45 mm diameter cold-drawn eutectoid carbon steel (0.8% C) wires (tensilestrength higher than 3000 MPa)

Towards the automation of the die spotting process: Contact blue pattern decryption

Automotive die spotting is one of the most complex and least standardized processes in the tool making process. A spotting expert identifies local contact areas through a blue-paste pattern and the die/sheet contact is optimized by manual grinding. Research performed on the impact of tribology conditions and surface irregularities on die behaviour have demonstrated the critical importance of die/sheet contact. Therefore, correctly understanding, standardizing, and automatizing die spotting is of a great interest for the industry. In this work, the first step toward the die spotting automation is performed by decrypting the contact blue pattern. Different test procedures were followed in order to decrypt the relation between the blue-paste pattern and the contact pressure and gap appearance in the interface. Additionally, a numerical method for automatic contact pressure detection based on the blue pattern was developed and validated. The outcome of this study is presented as potential tool for objective decision making towards the automation of the die spotting process and die contact analysis, focused to decrease try-out loops and thus reducing production time and costs

Fretting : review on the numerical simulation and modelling of wear, fatigue and fracture

This chapter presents a general background and the state of the art of numerical simulation and modeling of fretting phenomenon in terms of wear, fatigue and fracture. First, an introduction of fretting and its implications is exposed. Second, different methodologies for wear modeling and simulation are described and discussed. Afterwards, fatigue and fracture analysis approaches are revised. To that end, multiaxial fatigue parameters are introduced putting an emphasis on the physical basis of the fretting phenomena and the suitability of each model. On the other hand, the propagation phase based on linear elastic fracture mechanics (LEFM) via the finite element method (FEM) and the eXtended finite element method (X-FEM) analysis methods is presented and compared. Finally, different approaches and latest developments for fretting fatigue lifetime prediction are presented and discussed

The Interaction between the Sheet/Tool Surface Texture and the Friction/Galling Behaviour on Aluminium Deep Drawing Operations

The increasing demands for lightweight design in the transport industry have led to an extensive use of lightweight materials such as aluminium alloys. The forming of aluminium sheets however presents significant challenges due to the low formability and the increased susceptibility to galling. The use of tailored workpieces and controlled die roughness surfaces are common strategies to improve the tribological behaviour, whilst galling is still not well understood. This work is aimed at analysing the interplay between the sheet and tool surface roughness on the friction and galling performance. Different degrees of Electro Discharge Texturing (EDT) textures were generated in AA1050 material strips, and tooling presenting different polishing degrees were prepared. Strip drawing tests were carried out to model the tribological condition and results were corroborated through cup drawing tests. A new galling severity index (GSI) is presented for a quick and quantitative determination of both galling occurrence and severity. The present study underlines the key role of die topography and the potential of die surface functionalization for galling prevention