Frictional Heat Dissipation Research Articles

Anisotropic thermal conductivity of antigorite along slab subduction impacts seismicity of intermediate-depth earthquakes

Double seismic zones (DSZs) are a feature of some subducting slabs, where intermediate-depth earthquakes (~70–300 km) align along two separate planes. The upper seismic plane is generally attributed to dehydration embrittlement, whereas mechanisms forming the lower seismic plane are still debated. Thermal conductivity of slab minerals is expected to control the temperature evolution of subducting slabs, and therefore their seismicity. However, effects of the potential anisotropic thermal conductivity of layered serpentine minerals with crystal preferred orientation on slab’s thermal evolution remain poorly understood. Here we measure the lattice thermal conductivity of antigorite, a hydrous serpentine mineral, along its crystallographic b- and c-axis at relevant high pressure-temperature conditions of subduction. We find that antigorite’s thermal conductivity along the c-axis is ~3–4 folds smaller than the b-axis. Our numerical models further reveal that when the low-thermal-conductivity c-axis is aligned normal to the slab dip, antigorite’s strongly anisotropic thermal conductivity enables heating at the top portion of the slab, facilitating dehydration embrittlement that causes the seismicity in the upper plane of DSZs. Potentially, the antigorite’s thermal insulating effect also hinders the dissipation of frictional heat inside shear zones, promoting thermal runaway along serpentinized faults that could trigger intermediate-depth earthquakes.

Underwater dissimilar friction stir lap welding of aluminum alloy and CFRTP

With the rapid development of the transportation and electronic equipment industries, the demand for robust joining technology for metal/polymer has become imperative, especially in the pursuit of lightweight solutions. Underwater welding is one of the methods to reduce the formation of holes and other welding defects, which is conducive to improve the quality and strength of joints. In this study, the underwater friction stir lap welding (UFSLW) of 6061-T6 Al alloy and carbon fiber reinforced thermoplastic (CFRTP) joints is investigated. The welds are evaluated by optical microscope (OM) image, scanning electron microscope (SEM), and energy dispersive X-ray spectrometer (EDS) of the fracture, tensile, and hardness analysis. Research reveals that the presence of cracks and tunnel defects similar to those in air FSLW (AFSLW) is reduced in the underwater welding process. From the microscopic result analysis, the rapid dissipation of frictional heat and substrate viscosity in the cooling medium of circulating water in the stirring zone reduces the interaction between Al alloy and molten CFRTP, which leads to the rapid transformation of the plasticized material into a solid state and reduces the formation of thick stacked layer. In addition, finer Al alloy fragments are obtained in the welding zone due to the fast cooling rate. Ultimately, the maximum tensile strength of 32.12 MPa is achieved, which is 10.76% higher than that of the same welding parameters in air. Based on UFSLW technology, the joint strength of this study is 69% higher than that of Al alloy and polymer joints, which demonstrates enormous application potential and opens up new prospects for the joining technology of dissimilar materials.

Chelated titanate modified multilayer graphene-butylpyridine latex/polyethylene terephthalate composites with enhanced thermal conductivity

The low thermal conductivity of polyethylene terephthalate (PET) fabric, which affects the thermal conducting between different layers in composites, is often the weakness in the application of thick butadiene-vinylpyridine latex (BVL)/PET composite, slowing down the composites' processing efficiency and dissipation of frictional heat during operation. In this study, chelated titanate modified multilayer graphene (CTMMG) was used to functionalize butadiene-vinylpyridine latex (CTMMG-BVL), which was further applied for preparing composite to improve the thermal conductivity of PET-reinforced composite (CTMMG-BVL/PET). The static and dynamic stabilities of the CTMMG dispersion as well as thermal conductivity and electrostatic properties of the CTMMG-BVL film and CTMMG-BVL/PET composite were investigated. It was found that both static and dynamic stabilities of the CTMMG dispersion within 24 h were superior to unmodified multilayer graphene (MG) as the MG content and mass ratio of titanate to MG were 10 mg/mL and 25 %, respectively. Compared to the BVL film, the thermal conductivity and tensile strength of CTMMG-BVL film (CTMMG content: 2.19 wt%) were increased by 28.8 % and 4.5 %, respectively. The thermal conductivity of the CTMMG-BVL/PET composite was further enhanced by 48.3 % (from 2.65 to 3.93 W/(m·K)) compared to that of BVL/PET. The electrostatic property of the CTMMG-BVL film and CTMMG-BVL/PET composite was significantly improved. Fourier transform infrared (FTIR) analysis indicated that the mechanism for the excellent static and dynamic stability of waterborne CTMMG dispersions was attributed to the synergistic effects of the hydrogen bond and chemical bond formed between titanate and MG. The prepared CTMMG-BVL/PET composite with excellent thermal conductivity and heat dissipation showed potential application in many fields such as aviation, transportation, and seals.

Kalorimetrische Messung der Ver- zahnungsverlustleistung im Bereich hoher Umfangsgeschwindigkeiten

Gear damage, e.g. scuffing, reacts sensitively to the local dissipation of frictional heat during a full gear mesh. Several empirical friction models have been established in relevant literature. These can be used to calculate the gear friction locally or averaged over a mesh. For calibration purpose, experimental data from twin disc machines with stationary contact conditions are mostly used. However, the assignment of the model as well as the consideration of topographical, rheological and geometrical effects is often subject to uncertainties. In this paper, a method is presented to measure the power losses of high-speed spur gears up to vt = 100 m/s. The measurement principle uses the calorimetric properties of the circulating lubricant. The implementation of the measurement setup in a highspeed gear test rig reduces thermal interferences from sealings and bearings. Analysis regarding the measurement quality show that the measurement method delivers reproducible results with a high measurement resolution over a wide range of operating conditions.

Downscaling for disc-brake wear testing using a thermomechanical approach

Brake wear has been identified to be an important source of non-exhaust emissions in transportation. The high dissipated energy in the contact not only results in large frictional heat dissipation in the brake components but also in the generation of debris, particles and gases produced by the wear of both pads and disc. Numerical simulation or tribological tests at the material scale are still not sufficient to predict wear. Experiments at the original scale of the brake system are necessary, with a significant implementation time, high costs and with a limited scope. The aim of the present work is a downscaling strategy to design experiments at reduced scale (i.e. pin-on-disc tribometer scale) taking care of the thermomechanical characteristics of the full-scale braking situation in the case of a railway application. This approach requires a complete understanding of the thermomechanical processes occurring during braking, with respect to the contact loading, the thermal localizations (migrating hot bands), the kinematics of contact opening and closing, and the couplings with the tribological circuit and the wear processes. Their apprehension is based on tests carried out on a full-scale bench equipped with the studied railway brake. A numerical model has been developed to interpret the experiment with respect to the kinetics of contact location and opening-closing, and to identify the relative determinants, key to wear. The transposition of the brake configuration to the tribometer configuration is based on these determinants in the design of a wear-preserving tribosystem. For example, the design of the disc has been adjusted on the reduced scale pin-on-disc system to fit with the kinetical parameters of contact location previously described related to the wear determinants.

Effect of the Transverse Functional Gradient of the Thin Interfacial Inclusion Material on the Stress Distribution of the Bimaterial under Longitudinal Shear.

The effect of a functional gradient in the cross-section material (FGM) of a thin ribbon-like interfacial deformable inclusion on the stress-strain state of a piecewise homogeneous linear-elastic matrix under longitudinal shear conditions is considered. Based on the equations of elasticity theory, a mathematical model of such an FGM inclusion is constructed. An analytic-numerical analysis of the stress fields for some typical cases of the continuous functional gradient dependence of the mechanical properties of the inclusion material is performed. It is proposed to apply the constructed solutions to select the functional gradient properties of the inclusion material to optimize the stress-strain state in its vicinity under the given stresses. The derived equations are suitable with minor modifications for the description of micro-, meso- and nanoscale inclusions. Moreover, the conclusions and calculation results are easily transferable to similar problems of thermal conductivity and thermoelasticity with possible frictional heat dissipation.

Using twin-screw melt granulation to co-process mannitol and hydroxypropylcellulose

With the advent of continuous manufacturing, twin-screw melt granulation has attracted interest in the pharmaceutical industry as a method for co-processing excipients and developing new formulations. Twin-screw melt granulation relies on the heat and shear produced by the viscous and frictional heat dissipation generated by the rotating screws. The objective of this study is to explore the use of twin-screw melt granulation to co-process excipients in order to develop a new multifunctional excipient that improves the tabletability of mannitol. Binder level, barrel temperature, and screw speed are the main variables studied. Binder level (p < .05) has the most significant impact on the granule tabletability and the weight percentage of fines produced during granulation. Twin-screw melt granulation successfully co-processed mannitol and hydroxypropylcellulose (HPC), and a significant improvement in the tabletability of mannitol was observed at both 5% and 10% HPC levels. A 10% binder level was inferred to be the optimal level for a robust granulation process, and 5% was inferred to be feasible based on the tensile strength. A higher barrel temperature and a higher screw speed resulted in stronger granules. The optimal processing conditions were observed at a barrel temperature of 150 °C and a screw speed of 300 rpm. The tabletability of granules was evaluated against two different particle size fractions at the 10% HPC level. Fines (<150 μm) exhibited good tabletability as the tensile strength of all the compressed tablets exceeded the target of 2 MPa.

Simultaneously enhanced heat dissipation and tribological properties of polyphenylene sulfide-based composites via constructing segregated network structure

Self-lubricating polyphenylene sulfide (PPS) composites were fabricated by constructing a segregated network structure using the co-deposition method. Both carboxyl-functionalized multi-walled carbon nanotubes (CNTs) and silicon carbide (SiC) were successfully coated on the surface of PPS powders with the aid of self-polymerization of dopamine (PDA) and co-polymerization between PDA and polyethyleneimine (PEI), thereby forming [email protected] hierarchical reinforcing hybrids. Results showed that the thermal conductivity of [email protected] (0.97 W/(m K)) is about 120% higher than that of PPS/CNTs/SiC. The friction coefficient (0.193) and specific wear rate (2.50 × 10−5 mm3/(N m)) of [email protected] are 18.9% and 50% lower than those of PPS/CNTs/SiC, respectively. The enhanced thermal conductivity of [email protected] contributes to rapid dissipation of frictional heat at the sliding interface which protects the polymer substrate from being destroyed or peeled, thereby improving the tribological performance. This work provides new insights into expanding the application of self-lubricating polymer composites in the fields where efficient heat dissipation is also a primary concern.

Study of wear losses and frictional heat dissipation during dry sliding wear of ilmenite reinforced Al-alloy composite

In this investigation, ilmenite mineral reinforced Al–Si alloy matrix composite (AMC) has been developed. The wear behavior of the developed composites has been studied for their end application as break drum material to replace cast iron used in automobile industries. Ilmenite is one of the major sea beach mineral. AMC has been prepared through a low-cost stir-casting method in which 1 wt.% graphite (Gr)/tin (Sn) as a solid lubricant has been added during the fabrication of composites itself. The optical micrographs of AMC revealed uniform distribution of ilmenite particles throughout the matrix. The wear rate of the base LM30 alloy containing 17% Si and the developed composites has been studied at different normal loads at a constant velocity of 1.6 m.s−1. Optimized data revealed a significant wear rate reduction due to solid lubrication provided by Gr/Sn (∼32%). The wear rate of composites has been compared with traditional cast iron used in brake drums under similar experimental conditions. Composites exhibit nearly identical wear behavior throughout the test. The microstructural study of wear track and debris revealed that Sn and Gr used as solid lubricants played a vital role in reducing the wear loss of the prepared composites. A theoretical study of frictional heat generated during dry sliding and its dissipation has been done to establish the operative wear mechanism in the composites.

Effect of operating parameters of worm gearbox on lubricant oil temperature

Worm gearbox has the relative sliding motion between a tooth of worm and worm wheel which causes friction energy loss. The loss in friction energy is transfer into an equivalent amount of heat and that heat dissipate into lubricant oil. The frictional heat dissipation into lubricant oil causes an increment in the temperature of the lubricant oil and a decrement in the overall performance of the gearbox. To observe the effect of different operating parameters on increment in temperature of lubricant oil, one response parameter was defined i.e. Lubricant Heating Time (time required to raise the temperature of lubricant from 350 to 500. Oil volume, oil type, load on worm wheel and process time were taken as operating parameters. Every operating parameter was varied at three different levels. From the experimental results, it is observed that for all the oils if the load on the worm wheel increases keeping the oil volume constant then Lubricant Heating Time decreases and it follows the linear decrement relationship with the load on worm wheel. Also, for all the oils if the oil volume increases keeping the load on the worm wheel constant then Lubricant Heating Time increases and it follows a linear increment relationship with oil volume. It is observed that the rate of increase of temperature of lubricant oil initially was very high, latter on it decreases. The viscosity of oil affects the rate of increases in the temperature of lubricant oil. There exists an inverse relationship between Lubricant Heating Time and oil viscosity.

The influence of deformation on the medium-range order of a Zr-based bulk metallic glass characterized by variable resolution fluctuation electron microscopy

The medium-range order (MRO) of both as-cast and deformed states of a Zr-based bulk metallic glass (Zr52.5Cu17.9Ni14.6Al10Ti5 (at.-%) - Vitreloy 105) were analyzed using variable resolution fluctuation electron microscopy (VR-FEM). After deformation significant structural changes in the MRO were observed inside the shear bands and the adjacent matrix; the MRO was altered in terms of types, size and volume fractions. The changes in the matrix MRO confirm the existence of a shear affected zone around the shear band in our deformed sample. Since the MRO correlation length was larger inside the shear bands compared to the surrounding matrix, it is concluded that either frictional heat dissipation or shear induced nucleation and growth also plays a role in the alteration of MRO. The current work illustrates the significance of MRO in deformation of metallic glasses and suggests that the plasticity of monolithic BMGs can be improved by tailoring topological order based on MRO types, sizes and volume fractions.

Safety aspects on icy asphalt pavement in cold region through field investigations

It has been proved that ice shows different friction regimes. This work focuses on rubber friction on ice, a topic of great practical significance when it comes to grip of tires on icy road surfaces. Here the possibility of using Dynamic Friction Tester (DFT) for assessing skid resistance under icy condition is presented. The ice thickness was then controlled by the volume of the freezing water spraying on a consistent area so that the surfaces were characterized by different degrees of ice coverage. As a consequence, eight surface conditions were considered and tests were conducted at different temperatures ranging from −5 to −20 °C. In addition, aiming at the analysis of the changes due to wear of ice, several cycles of measurements were conducted and the effect of the temperature was investigated. The results showed that the dynamic friction coefficient reached steady state on icy surfaces during decelerating process, which is much lower than other conditions. Moreover, the data reached a low point at −14 °C, resulting from the thermal equilibrium between the dissipation of frictional heat during the contact and the melting of the ice layer between two consecutive passages.

The Influence of Deformation on the Medium-Range Order of a Zr-Based Bulk Metallic Glass Characterized by Variable Resolution Fluctuation Electron Microscopy

The medium-range order (MRO) of both as-cast and deformed states of a Zr-based bulk metallic glass (Zr52.5Cu17.9Ni14.6Al10Ti5 (at.-%) - Vitreloy 105) were analysed using variable resolution fluctuation electron microscopy (VR-FEM). After deformation significant structural changes in the MRO were observed inside the shear bands and the adjacent matrix. As a result of deformation two distinct MRO cluster types were formed in both matrix and shear bands. The structural evolution during plastic deformation suggests that frictional heat dissipation must have contributed to the alteration of MRO.

Properties of HVOF-sprayed Stellite-6 coatings

Stellite-6 coatings were deposited onto AISI 304 stainless steel substrate by gas-fueled HVOF spraying, systematically varying the process parameter settings.By operating the HVOF torch with a fuel-rich mixture, dense coatings (<1% porosity) are produced, containing up to ≈3 vol% oxide inclusions. A substantial amount of a Cr-rich f.c.c. phase is found, mainly produced by quenching of molten lamellae, and distinct from the equilibrium, Co-based f.c.c. solid solution retained in unmelted particles. These coatings exhibit pseudo-passive behavior and survive 5 cycles (100 h) of the Corrodkote test (ASTM B380-97) with no substrate corrosion. Coatings obtained from oxygen-rich mixtures, on the other hand, contain fewer oxide inclusions but also greater porosity, and do not protect the substrate against corrosion.The wear behavior of the coatings is less influenced by deposition conditions. In ball-on-disk dry sliding tests, all coatings exhibit wear rates of 2–3 × 10−5 mm3/(N·m), higher than those reported for bulk or clad Stellite, because of interlamellar delamination. Strain-induced, “martensitic” phase transformation from the f.c.c. structure to a h.c.p. one is observed over a 1–2 μm depth below the contact surface. Additional tribo-oxidation is onset when frictional heat dissipation has heated the wear debris enough to trigger its reaction with the environment. Correspondingly, a transition to a regime of higher friction occurs (from ≈0.6 to ≈0.8). At 400 °C, lamellar delamination is suppressed but wear rates rise to 5–8 × 10−5 mm3/(N·m) because of abrasive and adhesive wear. At 800 °C, a dense “glaze” tribofilm is formed by sintered debris particles, firmly bonded to a thermally grown oxide scale on the underlying metal surface. The “glaze” protects the coating, lowering the wear rate to ≈1 × 10−5 mm3/(N·m) and the friction coefficient to <0.45. Under high-stress particle abrasion conditions, wear rates of ≈1 × 10−3 mm3/(N·m) are found.

Effect of increasingly metallized hybrid reinforcement on the wear mechanisms of magnesium nanocomposite

Strength and ductility of pure magnesium have experienced simultaneous improvement due to the presence of nanosize hybrid (yttria and copper) reinforcement. Increasing the vol% (i.e., 0.3–1.0) of ductile metallic copper particles in reinforcement has further enhanced the strength of magnesium. Wear behaviour of these magnesium hybrid nanocomposites was investigated using pin-on-disc dry sliding tests against hardened tool steel using a constant sliding speed of 1 m s−1 under a range of loads from 5 to 30 N for a sliding distance of 1000 m. Scanning electron microscopy identified abrasion and delamination as primary wear mechanisms in the hybrid nanocomposite. Oxidation was active in nanocomposite with higher copper content, tested under higher load and positively affected the wear resistance. Limited thermal softening was observed when tested at a relatively higher load. High frictional heat dissipation capacity couples with higher hardness resisted adhesive wear which is common mechanism for magnesium composite.

Critical Insight into Mechanochemical and Thermal Degradation of Imidazolium-Based Ionic Liquids with Alkyl and Monomethoxypoly(ethylene glycol) Side Chains

Processes of mechanochemical degradation of imidazolium bis((trifluoromethyl)sulfonyl)imide ionic liquids with alkyl and monomethoxypoly(ethylene glycol) (mPEG) side groups were studied using the novel technique of mechanically stimulated gas emission spectroscopy. Mechanical stimulus caused degradation of both the anionic and cationic moieties. For the latter, the degradation was concentrated on the alkyl and ether chains rather than on the imidazole. For the anionic moiety, various degradation steps associated with the emission of CHxFy volatile products followed by SO2 and SO3 emission were identified. Simulation of frictional heat dissipation revealed that tribochemical reactivity was induced by the mechanical energy supply rather than the temperature increase. Thermal degradation of the same ionic liquids studied using thermogravimetric analysis and Fourier transform infrared spectroscopy was concentrated mainly on the cationic moiety. Thermal stability significantly depended on the side chains. The decomposition of mPEG-functionalized ionic liquids was a two-step process, where the lower temperature step corresponded to mPEG decomposition.

Effect of frictional heat dissipation on the loss of soil strength

In the present paper through a shear test on a fully saturated granular medium, simulated by the discrete element method, the effect of the heat produced by friction on the internal pore water pressure is explored. It is found that the dissipated energy is enough to increase the pore pressure and reduce the soil strength. In adiabatic and impermeable conditions the heat builds up quickly inside the shear band, and the softening is more pronounced. It is found as well that for real geological materials, heat conduction is not enough to reduce the pore pressure, and the softening prevails. Nevertheless, it is observed that the hydraulic conduction may mitigate or completely eliminate the temperature growth inside the shear band. This result provides new understanding on the thermodynamic factors involved in the onset of catastrophic landslides.

Investigation on Joining of Aluminum and Mild Steel by Friction Stud Welding

Joining of dissimilar metals has various automotive, aerospace, nuclear, chemical, and cryogenic applications. The present study focuses on friction stud welding of aluminum and mild steel. Experiments had been conducted by varying the process parameters and the strength of the friction welded joints was evaluated. Experimental results show that the speed of rotation, friction time, and axial shortening distance have significant effect on the impact strength of the welded joints. The dissipation of frictional heat from the weld center results in temperature gradient across the welded joint, causing different zones with different microstructures. Scanning electron microscope (SEM) micrograph reveals the presence of three distinctive regions in the heat-affected zone, namely, fully plasticized deformed zone, partially deformed zone, and unaffected base metal zone. The microhardness values were measured across the welded joint. At the interfacial region, there is an increased plastic deformation. This is due to the rise in heat input during friction stage and applied upsetting load in the forging stage. Consequently, there is an increase in hardness at the interfacial region of the welded joint.

히트 파이프를 장착한 디스크브레이크의 냉각 성능에 관한 연구

During braking operation, the surfaces of disk have severe contact conditions and high frictional heat would be generated between disk and pad surfaces. The heat makes high temperature gradient on disk surfaces and results in thermal deformation. To enhance the frictional heat dissipation, heat pipes are embedded in the ventilated type disk along the radial direction. The temperatures of the inner vent type disk and the brake disk with heat pipes are compared at the same operating conditions. By comparison a brake disk with heat pipes has higher cooling performance than the inner vent type disk.

Estimation of dry road braking distance considering frictional energy of patterned tires

This paper is concerned with the braking distance estimation of tire controlled by anti-lock brake system (ABS) according to a numerical–analytical method. While the frictional heat dissipation at disc pad is derived analytically, the tire frictional energy loss is computed by the 3D dynamic rolling analysis of patterned tire. Since the tire rolling analysis to obtain the time history of the frictional energy rate for the entire braking period is impractical, we alternatively seek the tire frictional energy rate curve versus the lapse of time by interpolating the discretized frictional energy rates computed at intervals of 10 km/h. The effect of ABS is numerically implemented by specifying the corresponding tire angular velocity to the dynamic rolling analysis. Applying the energy conservation law to each speed interval determines the interval-wise braking times and distances from which the total braking time and distance are predicted. Illustrative numerical experiment is presented together with the comparison with the experimental estimation.