Papers by Hisham Abdel-aal
INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2009: (ICCMSE 2009), 2012
Cutting tools are subject to extreme thermal and mechanical loads during operation. The state of ... more Cutting tools are subject to extreme thermal and mechanical loads during operation. The state of loading is intensified in dry cutting environment especially when cutting the so called hard-to-cut-materials. Although, the effect of mechanical loads on tool failure have been extensively studied, detailed studies on the effect of thermal loads on the deterioration of the cutting tool are rather scarce. In this paper we study failure of coated carbide tools due to thermal loading. The study emphasizes the role assumed by the thermo-physical properties of the tool material in enhancing or preventing mass attrition of the cutting elements within the tool. It is shown that within a comprehensive view of the nature of conduction in the tool zone, thermal conduction is not solely affected by temperature. Rather it is a function of the so called thermodynamic forces. These are the stress, the strain, strain rate, rate of temperature rise, and the temperature gradient. Although that within such consideration description of thermal conduction is non-linear, it is beneficial to employ such a form because it facilitates a full mechanistic understanding of thermal activation of tool wear.
Wear, 2000
This paper reports the findings of a preliminary investigation of the correlation between the the... more This paper reports the findings of a preliminary investigation of the correlation between the thermal properties of a rubbing material and its wear behavior at elevated temperatures. It is conjectured that, the potential of a material to accommodate a sudden change in its thermal state upon contact is an important factor that influences wear resistance of the material. Accordingly, metals which intrinsically maintain a smooth transition between two thermal states are more likely to display a favorable wear behavior at higher temperatures. Thus for such metals, the nature of transition is conducive to protective layer formation. The results indicate that for all alloys, an equilibrium between the conductive and the diffusive effects is maintained throughout the temperature intervals for which a favorable wear behavior was experimentally reported. Moreover, the bounds of such intervals mark the respective reported wear regime transition temperatures.
Tribology Letters, Jul 21, 2009
This article has been published OnlineFirst, but is withdrawn due to containing sections that had... more This article has been published OnlineFirst, but is withdrawn due to containing sections that had been taken verbatim from other sources. The authors have agreed to modify these sections and the revised article will be published with a new DOI number.
Revue Générale de Thermique, 1999
Wear, 2001
This paper studies the effects of the heat dissipation capacity of a rubbing material on wear res... more This paper studies the effects of the heat dissipation capacity of a rubbing material on wear resistance at high temperatures. These effects are studied with a special focus on the dilatation of the thermal energy in sliding. These results suggest a connection between wear transition and the change in the heat dissipation capacity of a rubbing material. The nature of change in the thermal properties before and after the transition influences the thermal environment within the contacting layers. This controls the kinetics of oxide formation and thereby controls wear. Thermal dilatation is a super position of three functions which represent the competing effects of the room temperature thermal properties and their respective variation with temperature. The possible relation between thermal dilatation and protective oxide formation is studied by examining the fretting wear data for two alloys a Ni-based alloy and a Co-based alloy. The results indicate a strong correlation between the formation of protective oxides and the change in the thermal dilatation of the examined alloys with temperature. Moreover, examination of the wear data suggests that a critical ratio between the effects of the conductivity and those of the diffusivity has to be established for favorable wear resistance. This ratio, which is controlled by the thermal effusivity of the rubbing material, reflects on the intrinsic ability of the material to sustain an oxidative reaction of a controlled rate. So that, the protective glaze oxide layers are formed in a rate that is, approximately equal to the rate of oxide layer break down. Whence, continuous compensation for the removed oxide layer (self-repairing oxides) is established.
International Journal of Precision Technology, 2010
Triboemission is a phenomenon associated with the sliding of variety of materials. The phenomenon... more Triboemission is a phenomenon associated with the sliding of variety of materials. The phenomenon is thought to be related to wear of diamond tools used in precision machining of semiconductors. As such, the physics of emission has recently acquired importance. Many researchers studied emission during scratching of solid surfaces. They observed that the intensity of tribo-induced emission of the electrons, ions, and photons decrease in the order: insulator>semiconductor> conductor. Many experiments conducted to compare the emission of negatively-charged particles in case of the semiconductors Si with that from selected insulators have reported a clear decreasing trend of the tribo-emission intensity as contact progressed over the same wear track for diamond-on-Si. Despite that all of these experiments were performed in vacuum, the origin of the weak signals and the decrease of signal strength in the case of Si centred on the presence of dielectric silicon oxide films formed in air during surface preparation or because of the samples being of mono-crystalline nature. This paper offers an alternative explanation to the behaviour of tribo-emitted particles based on the pressure induced semi-conductor-to-metallic phase transformation that takes place in Si during sliding. It is shown that due to repeated sliding, the wear tracks experience a semiconductor-to-metal transformation that renders the bulk of material immediately under the diamond slider conducting.
Springer eBooks, 2013
Cage ▶ Rolling Bearing Cage and Retainer Materials Calendar Oil ▶ Paper Machine Oils Canola Oil ▶... more Cage ▶ Rolling Bearing Cage and Retainer Materials Calendar Oil ▶ Paper Machine Oils Canola Oil ▶ Natural Oils as Lubricants
International Communications in Heat and Mass Transfer, Apr 1, 1999
This paper investigates the influence of the interfacial temperature rise, in the dry sliding of ... more This paper investigates the influence of the interfacial temperature rise, in the dry sliding of metals, onthe size of hot spots. An area expansion coefficient that corrects for such thermally induced changes is introduced. It is shown that the discrepancy between theoretical and experimental estimates of the area ratio, reported by some authors, may be avoided by taking into consideration the effects of temperature elevation on the properties of the sliding pair: namely, material softening and thermal expansion
International Communications in Heat and Mass Transfer, Feb 1, 1999
This paper investigates the dependence of the division of friction -induced heat on the contact p... more This paper investigates the dependence of the division of friction -induced heat on the contact parameters through the identification of the behavior of a characteristic funcaon under a combination of loads and speeds. The rubbing pair is assumed to have established contact over a circular spot. Thus allowing the use of pre-existing Green's function for the temperature rise due to an instantaneous disk source. It is shown that the dependonce of heat partition on the contact parameters is reflected only at moderate speeds. At high sliding speeds, however, that dependence is merely a function of the coupling between the local thermal properties (thermal conductivity and thermal capacity).
Tribology International, Nov 1, 2002
ABSTRACT This article investigates the kinetics of friction-induced-heat flux within the contact ... more ABSTRACT This article investigates the kinetics of friction-induced-heat flux within the contact layers of a rubbing solid. It is shown that nominally isotropic solids may exhibit anisotropic thermal behavior due to the mechanical dilatation exhibited during sliding. Depending on the degree of anisotropy the local flow of the thermal flux may be congested. This leads to the accumulation of thermal energy within the mechanically affected zone (MAZ) of the solid and may contribute toward a thermal environment that is conducive to protective layer formation. Depending on the evolution of mechanical dilatation, and the associated congestion of thermal flow, lateral accumulation of heat may take place. This, in turn, under favorable conditions causes the formation of a soft zone of low resistance to shear, thus leading to a transition in the mechanism of wear (e.g. from oxidative to delaminating). These effects are studied within the context of the sliding of a mild steel couple, and the results are subsequently applied to investigate the transition in the wear regime of a titanium (Ti–6Al–4V)–tool steel (AISI M2) sliding pair.
arXiv (Cornell University), Aug 2, 2010
We examine the relationship between wear and the generation of entropy in dry sliding of metals. ... more We examine the relationship between wear and the generation of entropy in dry sliding of metals. It is postulated that wear is related to irreversible entropy generation within the MAZ. We present a model, that treats the MAZ as a heat engine in the Carnot sense. The model assumes that the MAZ is a heat engine that transports heat from a high temperature reservoir, represented by the asperity contact layer, to a low temperature reservoir, represented by the sub-contact layer. Consequently an entropy generation source that represents the irreversibilities within the MAZ is defined and a study of the entropy generation is attempted. Wear data, published elsewhere, of two materials, Oxygen Free High conductivity Copper, and Commercially Pure Titanium are analyzed using the developed model. It is found that wear for both materials is correlated to entropy generation, and to the entropy flow within the MAZ. Interestingly, moreover, in view of the contrasting wear trends of the test materials, the relationship of the mass wear rate and the specific wear rate of each material with respect to entropy generation are totally opposite to each other. A common feature between the behavior of the two materials, was found in wear behavior with respect to a so called Ratio of Residual Entropy. This ratio determines wether the system is over or under supplied with entropy. It is found that when the capacity to transport entropy exceeds the entropy supply the mass wear rate increases, and when the entropy transport capacity of the system is exceeded and entropy generation takes place the mass wear rate decreases. This is attributed to the re-establishment of equilibrium within the system.
International Communications in Heat and Mass Transfer, May 1, 1999
The calculation of temperature fields that develop in rubbing metallic pairs is customary perform... more The calculation of temperature fields that develop in rubbing metallic pairs is customary performed under the assumption of a steady state and: that heat is released at the interface of the rubbing pair. These assumptions have several drawbacks as they neglect the role of the subsurface structural deformations which gives rise to internal heat generation. This paper introduces a solution for the transient temperature fields developed within two rubbing metallic solids with internal heat generation that varies exponentially with the distance from the nominal contact surface. The resuks indicate that in contrast to the customary, models, the maximum teniperature appears at some distance in the subsurface region. A result that is supported by the experimental observations of different authors
Discussion of “Fabrication and Testing of Bioinspired Surface Designs for Friction Reduction at the Piston Ring and Liner Interface” (Maddox, S. R., Gangopadhyay, A., Ghaednia, H., Cai, J., Han, X., Meng, X., Goss, J. A., and Zou, M., 2021, ASME J. Tribol., 143(5), p. 051109) Journal of tribology, Aug 3, 2021
Advances in computational intelligence and robotics book series, 2020
This chapter presents a comparative study of the topographical structure of three common biologic... more This chapter presents a comparative study of the topographical structure of three common biological robotic inspirations: human, canine, and feline feet. It is shown that the metrological roughness of each of the examined feet is customized for the specific locomotion demands of the species. The textural parameters manifest close correlation to the pressure distribution experienced in movement and gait. This correlation enhances the durability and structural integrity of the bio-analogue. It is also shown that the metrological function of the human (plantigrade) feet pads combine that of the back and the front feet pads of the digitigrade mammals examined. It is argued that integrating the targeted engineering of roughness within the design process of robotic feet can enhance the function of walking robots. Further, it offers elegant solutions to some of the current problems encountered in design of humanoids and other bio-inspired walking robots.
Discussion: “Wear Rate and Entropy Generation Sources in a Ti6Al4V–WC/10Co Sliding Pair” (Rudas, J. S., Gomez, L. M., Toro, A., Gutiérrez, J. M., and Corz, A., 2017, ASME J. Tribol., 139(6), p. 061608) Journal of tribology, Sep 29, 2017
Journal of tribology, Nov 11, 2009
Tribology Letters, Jan 29, 2020
Accurate estimation of temperature rise for sliding solids is still challenging. Part of the chal... more Accurate estimation of temperature rise for sliding solids is still challenging. Part of the challenge is accounting for the actual thermal behavior of the solids while sliding (i.e., the nonlinear effects taking place because of sliding conditions and their evolutionary path). Conventionally, only temperature-induced influence on transport properties has been considered. However, thermal properties of the solids also depend on contact stress, the rate of strain, and the rate of heat generation. The contact stress within the mechanically affected zone, even considering the hardness of the softest of the sliding pair, can reach several thousand times the value of atmospheric pressure. Under such a condition, thermal conductivity of many materials show a different behavior than that manifested under standard conditions. This work considers such an influence and its effect on the evolution of temperature. The results show that conventional estimates can considerably under-estimate the actual temperature rise. It is also shown that initial loading, may result in the contacting materials behaving as a layered structure, with each layer having a different capacity of thermal load dissipation. Depending on the distribution of that capacity, dissipation of friction heat may be constrained which may accelerate wear.
International Journal of Thermal Sciences, Feb 1, 1999
This paper proposes a procedure for utilising thermal strains as a thermometric means to recover ... more This paper proposes a procedure for utilising thermal strains as a thermometric means to recover the temperature distribution in tribo-specimens. The procedure is demonstrated in relation to strain data obtained by the analysis of the so-called Double Exposure Speckle Grams. Total strain components, are resolved into three elements: elastic, plastic, and thermal. These in turn are used to construct a system of difference equations, the solution of which yields a complete characterisation of the strain fields. Thermal strains are subsequently fed into a look-up table containing the coefficient of thermal expansion for the test material at different temperatures to yield the temperature distribution. The results are validated by comparison with an analytical model and relevant experimental data. © Elsevier, Paris.
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Papers by Hisham Abdel-aal