Interfacial Temperature Rise Research Articles

Control of Interface Migration in Nonequilibrium Crystallization of Li2SiO3 from Li2O-SiO2 Melt by Spatiotemporal Temperature and Concentration Fields.

During liquid-solid transformation, bulk mass and thermal diffusion, along with the evolved interfacial latent heat, work in tandem to generate interfacial thermodynamic and kinetic forces, the interplay of which decides the solidification velocity and consequently the solidified phase attributes. Hence, access to interface dynamics information in dependence of bulk transfer processes is pivotal to tailor the desired quantity of solid phases of unique compositions. It finds particular application for engineering concentrated Lithium (Li) phases out of Li-ion battery slags, thus generating a high value-added product from a conventional waste process stream. However, considerable challenge exists to predict the impact of the diverse external cooling rates on the evolving internal transfer processes and thus tuning solidification routes for achieving phases of interest. Hence, in this work, a thermodynamically consistent nonequilibrium model, by considering spatiotemporal temperature and concentration fields, is developed and applied to study solidification of Li2SiO3 from a Li2O-SiO2 melt that constitutes an important subsystem of the Li containing battery-recycling slags. The approach treats the sharp solid/liquid interface as a moving heat source. In the presence of different heat extraction profiles, it evaluates the spatial temperature heterogeneity and its implicit correlation to internal material fluxes resulting from maximization of dissipation and consequently the interrelation to interface velocities. Model calculations revealed that irrespective of the external cooling rate, for an initial short time duration, the magnitude of which increased with decreasing cooling rates, the interface velocities show a reducing trajectory directly relatable to the reducing thermodynamic forces due to localized interfacial temperature rise from the generated latent heat of fusion from the initial solidification. This is followed by a thermodynamically controlled regime, whereby for each cooling rate, the interface velocities increase until a maxima, the magnitude of which decreases with decreasing cooling rates. Finally, the interface propagation speeds decrease as controlled by the kinetic regime.

Study the influence of power-current impact with different conditions on the current-carrying wear property of carbon brush/friction disc contact

This study aims to investigate the impact of power current on the friction performance of carbon brushes/disc contact. A unique current impact test was conducted to analyze the impact of different current impact conditions, including impact current, duration, and frequency. The study identified rapid changes in the friction coefficient, electrical contact resistance, and interface temperature rise as the results of instantaneous current impact. The range analysis method was utilized to determine the primary and secondary order of current impact conditions in evaluating the wear properties of the carbon brushes/disc contact. Prolonged current impact duration led to adhesive wear of the interface, while a higher current density worsened the breakdown and melting effects of the oxide membrane between the contact surfaces.

Predictions of friction and temperature at marine cam-tappet interface based on mixed lubrication analysis with real surface roughness

The working conditions of cam-tappet pairs in marine diesel engines are directly influenced by the engine output power, the operational speed, the temperature, as well as the components surface micro-morphology, etc., which cause the cam-tappet pairs work in the mixed lubrication state, thus the interfacial friction, pressure and temperature rise are vital to engine performance, efficiency, and durability. An interfacial friction–temperature prediction model for the cam-tappet pairs, considering the effects of transient working conditions and the real surface roughness, is developed in the present study, based on the theories of the transient mixed EHL and the heat transfer under the condition of a fast moving heat source. The numerical results of surface temperature rise are compared with those from the Blok formula, and a good agreement is found. The obtained results show that the presence of 3D roughness may lead to a decrease in the lubricant film thickness, and the surface temperature rise of tappet may exceed 700 K, which is close to the material scuffing temperature, causing the surface failure due to scuffing and wear. If increasing the cam speed and base circle radius within certain range, it may lead to the increment of film thickness and reduction of surface temperature rise, thus the lubrication effectiveness is increased. In addition, using cast aluminum bronze may significantly reduce the surface temperature rise and improve the interfacial characteristics.

Comparative study of the current-carrying tribological properties of carbon graphite composites with different hardnesses

To investigate the effect of sliding speed and electrical current on the current-carrying friction performance of carbon brushes with different hardnesses. In this paper, two carbon-graphite material samples with different hardnesses manufactured by a powder metallurgical process were prepared. And a pin-disc current-carrying friction tester was used for testing. The results showed that the difference in hardness has a noticeably different effect on the sliding contact resistance and interface temperature rise of the material. As the electric current changes, the material with low hardness exhibited good adaptability. Then, the adhesive wear occurred for all materials of different hardnesses, and it changed to abrasive wear mainly with increasing electrical current. As the sliding speed increased, the wear rate of low-hardness material dropped, while the opposite trend was observed for high-hardness material. The increased sliding speed does not generate remarkable damage to the contact surface of the high-hardness material, which demonstrated good resistance to mechanical shocks.

Atomistic insight into flash temperature during friction

Heat generation at frictional interfaces is important due to its strong influence on the contacting material's deformation, microstructure, and mechanical properties. Inspired by the governing equations of convective heat transfer, a mathematical model is proposed to describe the microscopic friction-induced heat transfer process. The Prandtl-Tomlinson (P-T) model deals with the stick-slip motion of the sliding probe, and the energy conservation equation expresses the heat transfer process. The effect of friction on the heat transfer is represented by the frictional work in the energy conservation equation, and the thermal activation force in the P-T model introduces the effect of heat transfer on friction. Numerical results reveal that the interfacial temperature and friction force have the same period with the opposite trend. When the thermal-friction coupling effect is considered, the stick-slip motion is advanced, and the friction force decreases with the increase of the base temperature, while a barely noticeable difference is observed in the interfacial temperature rise. This work helps to improve the understanding of the heat transfer mechanisms between the rubbing surfaces, which is fundamental for various applications in friction welding and tribology.

Method of quasi-distributed interface fiber Bragg gratings monitoring dry band arc on the moist pollution layer of composite insulators

Arc discharge on the insulator surface poses a threat to the safe operation of electrical power system. However, effective monitoring technology for arc discharge is lacking. In this paper, a 10 kV composite insulator with 3 × 4 quasi-distributed fiber Bragg gratings (FBGs) embedded at the insulator core-housing interface was developed to monitor dry band arc on the moist pollution layer. The temperature coefficient of interface FBGs was obtained by the temperature calibration test. The interface temperature variation exposed to the instantaneous arc with arc duration of 67 ms and the short-lived arc with arc duration of 2.1 s was observed. Results show that owing to the occurrence of short-lived arc, a new phenomenon was observed: interface temperature drops sharply first, then increases rapidly. Three criteria of ED (Euclidean Distance, i.e. the measuring standard for the otherness of interface temperature of different axial positions), the sharp drop of interface temperature and interface temperature rise are proposed to monitor dry band arc. Based on the three criteria, interface FBGs can effectively monitor the instantaneous arc and the short-lived arc. This paper provides a beneficial method for discharge monitoring and flashover warning of composite insulators.

Interface temperature evolution exposed to arc discharges occurred on the uniform moist pollution layer of composite insulators based on interface fibre Bragg gratings

Arc discharges of moist polluted composite insulators pose a serious threat to the stable operation of transmission line. However, there is no effective detection technology for arc discharges. The evolution mechanism of interface temperature accompanied by arc discharges is not clear. In this paper, a 10 kV composite insulator with quasi-distributed fibre Bragg gratings (FBGs) embedded at the insulator core-housing interface was developed. The temperature calibration experiment of interface FBGs, and the arc discharges experiment of the uniform moist polluted composite insulator were conducted. Applied voltage was controlled to get the continuous arc with an arc time of 46 s and the intermittent arc with an arc time of 8 s. Exposed to the two types of surface arcs, the interface temperature evolution was explored. A new phenomenon of the sharp drop of the interface temperature was observed: the interface temperature first drops sharply and then rises rapidly during the continuous arc. Test results show that quasi-distributed FBGs are valid for detecting the two types of surface arcs by interface temperature rise. This paper provides a technical means to evaluate the state of surface discharges and insulating properties of composite insulators.

Tribodynamic studies of textured gearsets lubricated with fresh and MoS2 blended greases

The synergistic effects of surface texture and Molybdenum disulphide (MoS2) blended grease have been explored on the tribodynamic performance of spur gearsets. A texture involving ellipsoidal dimples on the face and flank of pinions’ teeth was fabricated using nanosecond pulsed fiber laser. The experiments were performed at different applied torques and a pitch line velocity of 4 m/s keeping in mind the practical application of the results. Contact resistance, vibrations, temperature rise and surface topographies have been measured and analyzed. Substantial increase (about 300%) in contact resistance and reduction (40% approximately) in vibration amplitudes at gear mesh frequency were found in the presence of texture. Reduction in interfacial temperature rise and less damage to teeth surface were also observed.

Influence of tool and workpiece interface temperature rise on the life of ice bonded abrasive polishing tool

Ice bonded abrasive polishing (IBAP) is a novel polishing method that employs a frozen slurry of water and abrasives as a polishing tool. This process is capable of producing ultra-fine finish on metallic as well as on non-metallic (ceramic) surfaces. The enhancement of productivity and efficiency of the process depends on the characteristics of the IBAP tool. During polishing, the IBAP tool melts due to frictional heat generated at the tool and workpiece interface. The melting rate influences the tool life and is one of the crucial aspects of the IBAP tool design. The present study aims to develop an analytical model to predict the melting rate of the tool as a function of abrasive properties, applied pressure, the relative velocity between the tool, and the workpiece surface. This model considered Jaeger's moving heat source method (1942) to determine the rise in temperature of tool and workpiece interface at steady-state and Blok's postulation (1963) to determine the fraction of heat conducted into the tool. The estimated melting rate of the IBAP tool is compared with the experimental data obtained from the reduction in the height of the IBAP tool at the polishing zone.

PVD AlTiN coating effects on tool-chip heat partition coefficient and cutting temperature rise in orthogonal cutting Inconel 718

Significant cutting temperature rise is induced in dry machining Inconel 718 with high cutting speed due to its low thermal conductivity and high hot hardness. PVD AlTiN coating can avoid direct contact between tool substrate and moving chip, which will affect tool-chip interface heat partition and temperature rise. However, few studies were relevant with the effect of AlTiN coating on tool-chip interface heat partition and temperature rise in dry cutting Inconel 718. In this study, the tool-chip interface temperature rises due to heat generations in primary and secondary deformation zones (PDZ and SDZ) are predicted with various heat partition coefficients, respectively. The cutting temperatures measured by two-color thermometer are utilized to determine the heat partition coefficient, and to verify the proposed interface temperature predictive model for dry orthogonal cutting Inconel 718 at cutting speed 40, 80 and 120 m/min with uncoated and PVD AlTiN coated tools. It is found that AlTiN coating decreases crater wear, and tool-chip contact length compared with that using uncoated tool. AlTiN coating decreases the maximum tool-chip interface temperature 39.00 °C and 5.47% compared with that using uncoated tool at 120 m/min. Heat partition model RG-W and RR was suitable for temperature prediction with least summary relative errors in cutting Inconel 718 with uncoated and AlTiN coated tools. The results illustrate that the PVD AlTiN coated tool could be beneficial in high-speed dry cutting Inconel 718 due to its less tool-chip interface temperature rises and tool crater wear.

Internal Temperature Detections of Contaminated Silicone Rubber Under Discharge Conditions Based on Fiber Bragg Gratings

Composite insulators are widely used in power grids at home and abroad. The anti-pollution flashover performance, hydrophobicity and hydrophobic migration, and pollution flashover mechanism of composite insulators have been the focus of international attention. Temperature is one of the important parameters to describe the flashover of composite insulators. In this paper, the internal temperatures of a composite insulation sample were detected based on FBGs (fiber Bragg gratings). The sample was layered and made of one layer of silicone rubber 3 mm in thickness and one layer of epoxy-GFRP (Glass Fiber Reinforced Plastics) similar to 220 kV composite insulators. Three gratings were embedded in the interface of the two layers between long and short electrodes on the surface of the sample. Temperature calibration tests were carried out on the gratings in the sample. Then, discharges tests were done on the sample with embedded FBGs. Internal temperatures as well as leakage currents were measured, and the arcs process of the discharges on the sample was photographed. The test conditions are as follows: the output voltage was increased by approximately 0.5 kV/s; the equivalent salt deposit density (ESDD) was about 0.5 mg/cm2 and the non-soluble deposit density (NSDD) was about 1.2 mg/cm2.The results show that the internal FBGs could sense the flashover on the surface of the sample. An interface temperature rise caused by the discharges is within 11 °Cin this paper. There is a time delay of 1.4 s from the leakage current arise to the temperature rise during the discharges. The arcs always develops from the small electrode to the large electrode on the surface of the sample, the rise process of the internal temperature at the interface under the middle surface position of the two electrodes is significantly different from that near the small electrode, the arcs starting electrode, while similar to that near the large electrode, the flashover electrode.

A thermo‐mechanical model of ultrasonic metal welding process with the focus on the mating interface

AbstractUltrasonic welding (USW) of metals is counted as a solid state consolidation of the involved parts, in which the growing interface temperature is far below the melting point of the material. This type of welding is a joining technique, in which a combined effect of the applied pressure and the ultrasonic frictional vibrations on the surface of the mating parts causes the formation of the bond. This contribution is devoted to study the coupled effect of the process parameters, namely the applied pressure and the amplitude of the ultrasonic vibrations on the interface temperature rise. Finally the result of the proposed thermo‐mechanical model are compared with the results from experiments in ultrasonic wire bonding.

The frictional energy dissipation and interfacial heat conduction in the sliding interface

The energy dissipation rate and interfacial thermal conductance between two sliding surfaces are important to accurately predict the interface temperature rise, while their physical mechanism is not well understood. In this study the energy dissipation and interfacial thermal transport between a sliding silicon film and a fixed silicon substrate are investigated by molecular dynamics simulations. The results show that the mean friction force first increases with increasing normal load. However, when the normal load exceeds the critical value of about 60 eV/Å, the interface atoms begin to collapse, causing the mean friction force to drop with the further increase of the normal load. Our study also shows that the energy dissipated during the friction process is quantitatively equal to the conducted heat. By extracting the interfacial temperature difference, it is found that the interfacial thermal conductance in sliding state is 2∼4 times higher than that in static state with the same normal load from 10 to 60 eV/Å. This is because the interfacial atoms suffer great dynamic impacts during the friction process, which excites more non-equilibrium phonons and helps to enhance the phonon interfacial transmission coefficient. The present investigation demonstrates that the dynamic excitation induced by the friction process can modify the interfacial thermal conductance, which would be of great significance to accurately predict the temperature rise of the sliding interface.

Effect of process parameters on the interface temperature in ultrasonic aluminum wire bonding

In the present work, a very first attempt has been made to investigate the effect of two process parameters, namely the applied sonotrode pressure and the amplitude of the ultrasonic oscillations on the temperature rise at the interfaces of thin aluminum strands during ultrasonic welding (USW) of multi-strand single core cables. By measuring the temperature inside the wire bundle through thermocouples, it is found that increasing the amplitude of vibrations in the USW process of multi-strand cables is more effective in interface temperature rise than increasing the applied pressure.During USW of a strand bundle, the sonotrode pressure defines the potential positions for the weld points, whereas the amplitude of vibrations defines the degree of bonding at those points due to the effective heat generation as a result of sliding friction. A finite element model of the strand bundle displays the same trend for the effect of pressure as well as amplitude of vibrations on the interfacial temperature rise. Furthermore the applied pressure on the mating parts enhances the efficiency of the ultrasonic welding process, whereas an extended sonotrode pressure results in a lower temperature rise, as it prevents the strands from effectively sliding against each other. Microsections of the welded samples, which show the formation of different interfacial bonds under different sonotrode pressures, reveal that with an extended sonotrode pressure, strands undergo strong plastic deformations but a better bondability is not achieved. Observation of aluminum softening at some bonding parts within the wire bundle is an indication of a high local temperature rise at strand interfaces.

Experimental study on fatigue performance of adhesively bonded anchorage system for CFRP tendons

Abstract This study is concerned with the fatigue performance of adhesively bonded anchorage for carbon fiber reinforced polymer (CFRP) tendons subjected to cyclic loading. Series of monotonous and cyclic experiments under different stress amplitudes and loading frequencies were carried out in order to investigate the mechanical performance of bonded anchorage systems for CFRP tendons and to study the influence of cyclic loading on the anchoring performance. The fatigue damage and the relationships between damage, loading frequency and interfacial temperature rise of anchorage systems were analyzed. The results show that cyclic tension-tension loading is instrumental in enhancing the synergistic interaction between the anchorage components and it also stabilizes the entire anchorage system performance provided that the stress amplitude is kept lower than 10% of the ultimate tensile capacity of the anchorage systems and the maximum stress is less than 50% of the ultimate capacity of the anchorage system. The loading frequency influences significantly the temperature variation in the anchorage system. A high loading frequency may result in a sharp temperature rise at the early-stage and mid-stage of cyclic tension-tension loading, followed by a rather stable late stage. This phenomenon of temperature rise during fatigue tests may indicate the extent of fatigue damage in the anchorage system.

Friction and wear behavior of PI and PTFE composites for ultrasonic motors

High‐performance polymer‐based frictional materials have become increasingly important to improve the mechanical output properties of ultrasonic motors. This study discussed the friction and wear behavior of 2 dominating frictional materials of polymer composites for ultrasonic motors, polyimide (PI), and polytetrafluoroethylene (PTFE) filled by aramid fibers (AF) and molybdenum disulfide (MoS2). To explore the wear mechanisms, the tribo‐pair contact stress was theoretically characterized, and the interface temperature rise was numerically predicted. The predictions showed that the flash temperature on asperity tips could reach the glass transition temperature of the polymer materials. The experimental results indicated that the contact stress and sliding speed have a small effect on the friction of the PI composite but influence considerably the friction of the PTFE composite. A higher contact stress brings about a higher specific wear rate, but a higher sliding speed reduces the wear rate. Compared with AF/MoS2/PTFE, the AF/MoS2/PI has much better tribological performance under high loads and speeds.

Prediction of the Interface Temperature Rise in Tribochemical Polishing of CVD Diamond

Tribochemcial polishing is one of the most efficient methods for polishing CVD (Chemical Vapor Deposition) diamond film due to the use of catalytic metal. However the difficulty to control the interface temperature during polishing process often results in low material removal because of the unstable contact process. So this research investigates the contact process in the tribochemical polishing of CVD diamond film and proposes a dynamic contact model for predicting the actual contact area, the actual contact pressure, and the interface temperature in the polishing process. This model has been verified by characterizing surface metrology of the CVD diamond with Talysurf CLI2000 3D Surface Topography and measuring the polishing temperature. The theoretical and experimental results shows that the height distribution of asperities on diamond film surface in the polishing process is well evaluated by combining the height distribution of original and polished asperities. The modeled surface asperity height distribution of diamond film agrees with the actual surface metrology in polishing process. The actual contact pressure is very large due to the small actual contact area. The predicted interface temperature can reach the catalytic reaction temperature between diamond and polishing plate when the lowest rotation speed and load are 10 000 r/min and 50 N, respectively, and diamond material is significantly removed. The model may provide effective process theory for tribochemcial polishing.

Transient Thermal Analysis of Cold Strip Rolling Considering Rough Surface Contacts

This paper presents a transient thermal analysis of cold strip rolling, integrating both the microscale asperity deformation and macroscale strip deformation. A statistical characterisation was carried out to obtain the contact pressure and thermal contact conductance at the roll-strip interface. To address the effects of rolling speed and temperature rise, Johnson-cook constitutive model of yielding strength was employed to incorporate the strain rate and temperature variation in the analysis. It was found that the developed model can successfully predict both the interface contact stress and temperature rise in the rolling bite.

Modeling and Parametric-Sensitivity Analysis of Nonisothermal Reactive Absorption

We address the uniqueness and multiplicity of the equilibrium solutions in a specific class of chemically reactive system involving nonisothermal reactive gas absorption. A film model that is not restricted to a particular reaction regime is developed for (m,n)th-order irreversible reactions. Lower and upper bounds for the interfacial temperature rise are proposed, and tested by application to real systems, including the chlorination of n-decane, chlorination of toluene, and sulfonation of dodecylbenzene (DDB). We further develop a categorization of the possible bifurcation parameters, and propose lower and upper bounds for each of the new parameters in the generalized model. A parametric-sensitivity analysis in the kinetic- and reactor-parameter spaces is presented. It is shown that the steady-state multiplicity behavior of the system is more sensitive to the kinetic parameters, whereas a few of the new reactor parameters are of significant impact.

Experimentally-validated mesoscale modeling of the coupled mechanical–thermal response of AP–HTPB energetic material under dynamic loading

This manuscript presents a combined computational–experimental study of the mesoscale thermo-mechanical behavior of the Hydroxyl-terminated polybutadiene (HTPB) bonded ammonium perchlorate (AP) composite energetic material subjected to dynamic loading conditions. The computational model considers the AP–HTPB interface debonding, post-debonding interface friction and temperature rise due to viscoelastic dissipation as well as dissipative interfacial processes. The interface is modeled using a cohesive zone model combined with a contact algorithm to account for the interface separation, particle/binder contact and heat generation. The HTPB binder is modeled as viscoelastic with adiabatic temperature rise. Three experiments are conducted to calibrate and validate the model. Raman spectroscopy and indentation experiment are employed to determine the interface properties, whereas Kolsky bar tension test along with in-situ synchrotron X-ray diffraction measurements are used to validate the model and understand the interface separation characteristics under dynamic loading.