Friction-induced Heat Research Articles

Enhancing Friction Stir Welding Performance: Finite Element Simulation Study using Filler Material

Friction Stir Welding (FSW) is a groundbreaking method that revolutionizes welding by utilizing friction-induced heat to join metals without melting them. In this study, we conducted a comprehensive investigation into the FSW process using the numerical software Simufact Forming, focusing on the critical aspect of introducing filler material during the welding operation. Our work involved meticulous simulations to analyze the impact of filler material on the quality and integrity of the weld joint. Through detailed modelling and parameter optimization, we successfully demonstrated the significance of the refill stage in achieving superior welding outcomes. Our main results reveal a substantial enhancement in the weld joint's mechanical and metallurgical properties when filler material is strategically introduced. The simulations provided valuable insights into the optimal conditions for the refill stage, including tool movement, material feeding rates, and key process parameters. These findings contribute to the ongoing efforts in refining FSW techniques, facilitating the development of high-performance welded joints.

DEM analysis of heat generation and transfer during granular flow in a rotating drum

In many granular material handling processes, heat generation, and subsequent temperature rise, due to contacts between particles and surfaces is common. Aiming to explore this phenomenon, friction-induced heat generation and heat transfer models are developed and implemented into a Discrete Element Method (DEM) in this paper. The DEM models are validated qualitatively for the temperature distribution pattern and quantitatively for the evolution of particle temperature rise using data obtained experimentally. Moreover, the temperature distribution of the drum end plates obtained in the simulations shows the same annulus pattern observed in experiments. It is also found that increasing the rotation speed of the drum leads to an increase in the annular heated region of drum and in the net heat that particles obtain. In addition, a higher rotation speed leads to higher absolute fluctuations and lower relative variability of particle temperature.

Heating patterns and temperature distribution of projectile surface in lunar regolith penetration

During penetration, a large quantity of friction-induced heat is generated, significantly increasing the projectile surface temperature. Considering that the temperature variation depends on the physical properties of the target being penetrated, understanding this relationship can aid in extraterrestrial material behavior for detection and analysis efforts. The study investigated the patterns of heat generation and the distribution of temperature on the surface of a projectile as it penetrates lunar regolith. For discrete medium penetration, large deviations appear in temperature prediction due to particle extrusion flow. Thus, a heat flux density model on the projectile surface by introducing a relative velocity factor (RVF) for correction was established. The particle flow characteristics simulation and fitting model of the introduced factor were also obtained. We constructed a theoretical relationship between the resistance and stress model parameters using dynamic modeling. Experimental projectiles recording penetration acceleration and temperature at the points of interest on the projectile surface were designed and tested to obtain recorded data. The temperature field in this process was simulated in COMSOL software to calculate the projectile surface's heat flux density and temperature distribution. The results indicate that the developed model is effective. This research infers the physical characteristics of the penetrating target under specified penetration conditions and provides more dimensional information for lunar regolith exploration.

Skiing-inspired robust lubricating composite coatings from thermally sprayed ceramic template

Inspired by the mechanism of skiing, herein, a novel composite coating with excellent lubrication properties was developed by incorporating solid-liquid reversible lubricating phases into the inherent microcracks and pores of thermally sprayed ceramic coatings. The results indicate that the crystalline-amorphous heterostructure formed within the micro-nano cracks, enhancing their cohesive strength and toughness. Compared to traditional ceramic coatings, the friction coefficient of the composite coating has been reduced by 80 %, while the wear rate decreased from 2.89 × 10−4 to 6.44 × 10−7 mm3∙N−1∙m−1. Under the applied load and friction-induced heat, a thin liquid lubrication film is formed. Importantly, the lubricating phase continuously overflows from defects under the induction of frictional heat to replenish the lubricating film, ensuring long-term lubrication of the coating.

Friction and heat partition coefficients in incremental sheet forming process

To understand the thermo-mechanical behaviour in incremental sheet forming (ISF), it is important to precisely determine the interfacial and thermal-relevant parameters including coefficient of friction (COF) and heat partition coefficient (HPC), and to characterise the effect of thermo-mechanically induced heat generation under ISF processing conditions. In the present study, a new tool path-defined straight groove test combined with mechanical and thermal detection is proposed to determine the COF and HPC of Aluminium alloy (AA1050) and commercially pure titanium Grade 1 (CP Ti Grade 1) sheets. The experimental and numerical results show that the determined COF and HPC values are sufficiently accurate. The interaction between friction force and thermal response is observed by this testing method. A novel theoretical thermal model is developed to correlate the relationship between friction-induced heat generation and the thermal effect. The results indicate that the new theoretical model can capture the temperature distribution and variation under different processing conditions, and the results show a good agreement with the finite element (FE) simulation. The presented testing method and theoretical model provide an insight into the determination of the thermal-relevant parameters (COF and HPC), and the quantification of the effect of friction-induced heat generation on the thermal response of the materials.

Tribological properties and tribomechanism of nickel nanoparticles in-situ synthesized in rapeseed oil

Nickel (Ni) nanoparticles can be enriched on the surface of iron-based frictional pairs, which provides the possibility to get rid of the competitive adsorption between the polar species of vegetable oil and the surface-active nano-additives thereon. In this paper, nickel acetylacetonate was used as a precursor to in-situ synthesize nickel nanoparticles with an average diameter of about 12 nm in rapeseed oil (RO) as the reducing agent, surface modifier, and solvent as well. The tribological properties of the as-synthesized Ni nanoparticles were evaluated with a four-ball tribometer, and their tribomechanism was investigated based on the characterizations of the tribofilm on rubbed steel surfaces by the scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). It was found that the Ni nanoparticles in-situ prepared in the RO with a mass fraction of 0.3% can reduce the wear scar diameter (WSD) of the steel ball by 36%. This is because, on the one hand, the Ni nanoparticles are adsorbed on the rubbed steel surfaces to repair or fill up the micro-pits and grooves thereon. On the other hand, Ni nanoparticles participate in tribochemical reactions with atmospheric O and steel substrate to form the tribochemical reaction film on the rubbed steel surfaces with the assistance of friction-induced heat and applied normal load. In addition, an amorphous carbon film is formed on the rubbed surface via the carbonization of base oil under the catalysis of Ni nanoparticles. The adsorbed Ni layer, the tribochemical reaction film, and the carbon layer comprise a composite tribofilm composed of amorphous carbon, polar fatty acid, metallic nickel, iron oxides, and nickel oxides on the rubbed steel surfaces, which contributes to significantly improving the antiwear ability and load-carrying capacity of the RO for the steel–steel sliding pair.

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.

Comparison of Friction Extrusion Processing From Bulk and Chips of Aluminum-Copper Alloys

Friction extrusion processing describes the extrusion of metallic materials via severe plastic deformation imposed by friction-induced heat and shear strain. The process features relative rotational movement between die and feedstock material, resulting in complex shear introduction affecting local thermal and material flow conditions. While the processing of powders, chips and bulk material for improvement of extrudate properties has been studied independently, this work focuses on the direct comparison between the friction extrusion of bulk material and chips of AlCu10 under identical processing conditions. Analysis of machine response and microstructure in the extruded wires allows for first conclusions, identifying characteristics and requirements for friction extrusion processing from different feedstock materials.

Flow-coupled thermo-mechanical analysis of frictional behaviors at the tool-workpiece interface during friction stir welding

Friction stir welding (FSW) has been applied to many fields including aerospace manufacturing and the railway industry. However, the interfacial friction behavior remains unclear due to the lack of reliable thermo-mechanical-flow-coupled analysis. In this study, the frictional behaviors, including the interfacial temperature, friction-induced heat generation, interfacial stick-slip state, and mass transfer during the FSW process of AA2024-T4 are elucidated based on experimental investigation and a novel three-dimensional computational fluid dynamics (CFD) analysis. It is found that the temperature is heterogeneously distributed at the tool-workpiece interface which ranges from 380 to 431 °C. The heat generation contributed by the slipping friction is less than that contributed by deformation heating. This stems from the fact that friction-induced interfacial stick is presented over a large area of the tool-workpiece interface, while a significant slip occurs at the shoulder periphery and the middle of the pin end. As a result of the interfacial stick, a highly-localized high-velocity zone (HVZ) is formed within the vicinity of the tool-workpiece interface with nonnegligible vertical velocity. Fast mass transfer occurs within the HVZ in a maelstrom pattern; while relative slow mass transfer occurs in a straight-through pattern outside the HVZ. Moreover, the friction-induced temperature field and material flow field in the vicinity of the tool-workpiece interface during the FSW process are predicted by using numerical simulation and validated by the measured temperature and the observed weld macrograph. By using the state-of-the-art simulation approaches, this study provides a quantitative analysis of the friction behavior during FSW, which benefits an in-depth understanding of FSW and thus brings new design concepts.

A contribution on versatile process chains: joining with adaptive joining elements, formed by friction spinning

Nowadays, manufacturing of multi-material structures requires a variety of mechanical joining techniques. Mechanical joining processes and joining elements are used to meet a wide range of requirements, especially on versatile process chains. Most of these are explicitly adapted to only one, specific application. This leads to a less flexibility process chain due to many different variants and high costs. Changes in the boundary conditions like sheet thickness, or layers, lead to a need of re-design over the process and thus to a loss of time. To overcome this drawback, an innovative approach can be the use of individually manufactured and application-adapted joining elements (JE), the so-called Friction Spun Joint Connectors (FSJC). This new approach is based on defined, friction-induced heat input during the manufacturing and joining of the FSJC. This effect increases the formability of the initial material locally and permits them to be explicitly adapted to its application area. To gain a more detailed insight into the new process design, this paper presents a detailed characterization of the new joining technique with adaptive joining elements. The effects and interactions of relevant process variables onto the course and joining result is presented and described. The joining process comprises two stages: the manufacturing of FSJC from uniform initial material and the adaptive joining process itself. The following contribution presents the results of ongoing research work and includes the process concept, process properties and the results of experimental investigations. New promising concepts are presented and further specified. These approaches utilize the current knowledge and expand it systematically to open new fields of application.

Influence of shoulder diameter on interfacial microstructure and mechanical behavior in dieless friction stir riveting of CP-Copper to 321 stainless steel

This study investigated the influence of changes in the tool shoulder diameter on the microstructure, bonding, diffusion, and tensile-shear behaviors of the dieless friction stir rivetted CP-copper/Zn/AISI 321 stainless steel joints. The results reveal that the increase in the shoulder diameter increases the peak temperature, width of the brazed and stir zones, and the tensile-shear load (1944–2429 N) of the joints. The wider tool shoulder produced a good metallurgical/interfacial bonding at the stir zone and restrained upper sheet bulging (USB) effect at the brazed zone of the joint whereas USB-induced sheet separation and lateral unbonded path could not be prevented with the smaller tool shoulder diameter (12 mm). The change of the tool shoulder diameter changes the fracture behavior and the diffusion gradients of Cu from steep to gradual profile due to differences in the friction-induced heat input/temperature. A wider tool shoulder diameter is recommended for defect elimination and improved strength.

Anti-oxidation mechanism and interfacial chemistry of BN@CaCO3-SiO2 microcapsule-added sodium borate melt on the sliding steel surfaces at elevated temperatures

This study reports the chemistry underpinning the superior anti-oxidation and lubrication of the BN@CaCO3-SiO2 microcapsule-added sodium borate melt at 930 °C by surface-interface tailoring. Under static oxidation at 930 °C, sodium borate reacts to the microcapsule’s shell that generates the sodium-calcium borosilicate melt and releases the h-BN nanosheets. Interfacial characterizations reveal a negligible corrosion attack and superior anti-oxidation of the sodium-calcium borosilicate compared to sodium borate (by ~ 86%) which is due to the weak mobility of sodium in the melt network. Under sliding conditions at 930 °C, friction modifies profoundly the interfacial reactivity of the sodium-calcium borosilicate melt toward the oxide surfaces. An intermixing effect and the friction-induced heat accelerates the high-temperature reactions between the melt and the spinel oxides on the sliding surfaces that result in the formation of the plate-like non-layered M-type CaCrxFe12-xO19 hexaferrite. A synergy between the h-BN nanosheets, the grain-refinement of the sliding surfaces, and the intercalation of the M-type hexaferrite at the sliding interfaces contribute to a superior friction reduction (by ~ 70%) compared to sodium borate melt under boundary conditions with high contact pressures. These findings highlight a potential strategy for achieving excellent lubricity, superior anti-oxidation, and reduced corrosion from the melt lubricants at high temperatures.

Tribological performances of copper perrhenate/graphene nanocomposite as lubricating additive under various temperatures

• The copper perrhenate was synthesized via microemulsion reaction method, and then was coated on the surface of graphene using an ultrasonic method. • The copper perrhenate/graphene as oil additive exhibited excellent lubricating performance. • The protective layer consisted of copper perrhenate, remnant carbide and native oxide was formed at elevated temperatures. Herein, copper perrhenate (Cu(ReO 4 ) 2 ) was synthesized using a micro-emulsion method and adhered to graphene (Gr) using an ultrasonic process. Then, the as-prepared Cu(ReO 4 ) 2 /Gr composite was added into the synthetic oil as a lubricant additive with the help of ionic liquid to achieve enhanced dispersion stability within the base oil. The tribological performances of the Cu(ReO 4 ) 2 /Gr additive were investigated using four-ball tests and the ball-on-disk reciprocating configuration under various temperatures. The potential lubrication mechanisms of the Cu(ReO 4 ) 2 /Gr additive were performed using a series of characterization methods including XRD, Raman, SEM-EDS, TEM, DSC/TG, and XPS. The results of four-ball tests at room temperature indicated that the Cu(ReO 4 ) 2 /Gr additive could substantially improve the tribological performances of the base oil. The smallest coefficient of friction (COF) and wear scar diameter (WSD) values were 0.068 and 495 μm, respectively, when 0.05 wt% of Cu(ReO 4 ) 2 /Gr was added. Additionally, the graphene accelerated friction-induced heat transfer, which led to decreased friction and wear. The results of reciprocating friction experiments at elevated temperatures revealed that the Cu(ReO 4 ) 2 /Gr additive had excellent friction-reduction properties when the temperature was high. This could be attributed to the generation of a protective layer containing tribo-oxides from the alloy, some residual carbides and copper perrhenate induced by friction heat and stress. This protective layer was uniformly and stably covered on the worn surface, which could effectively alleviate direct contact between the rubbing pair.

Joining with versatile joining elements formed by friction spinning

Mechanical joints are an essential part of modern lightweight structures in a broad variety of applications. The reason for this is the rapidly increasing number of different material combinations needing to be joined in areas of application like the automotive industry. It is currently common to use numerous standardized elements (if necessary, from different joining technologies) instead of individually adapted joining elements. This leads to a large number of different joining elements per product and thus to high costs.An innovative approach to overcome this issue is the design and manufacturing of application adapted joining elements. A promising strategy for the manufacturing of adapted joining elements of this type is the so-called friction spinning process. The joining elements formed in this way can be specifically adapted to the application in question in terms of shape and mechanical properties. The joining process using this friction spun joint connectors (FSJC) benefits from the use of friction-induced heat and supports the process by reducing the joining forces required through a variation of the rotational speed and the feed-rate. By controlling the significant process parameter (e.g. the joining force), it is possible to substantially influence the quality of the joint or the joint properties. The following contribution will present results of ongoing research at Paderborn University and includes the process concept, the process properties, the tooling and the results of the experimental investigations of the joining of two preholed sheet metal parts with help of this new joining process.

Analysis and Optimization Study of Piston in Diesel Engine Based on ABC-OED-FE Method

In order to increase the reliability and service life of piston in a heavy-duty diesel engine, the geometric structure of piston was optimized based on its maximum temperature and maximum coupling stress. To begin with, the boundary conditions of thermal and stress fields are calculated, which include the heat produced by the combustion in cylinder, the friction-induced heat, and the heat transferred to cooling system. Then, the finite element model was established to calculate and analyse the temperature and thermal-mechanical coupling stress fields of the piston. By combining this simulation model with orthogonal experimental design methods, computations and analyses were performed to determine how the five geometric parameters (depth of intake and exhaust valve grooves, radius of valve grooves transition, radius of top of valve grooves, height of first piston ring groove, and depth of piston ring groove) influence the two evaluation indicators (maximum temperature and maximum stress of piston). Subsequently, using the proposed ABC-OED- FE (artificial bee colony, orthogonal experiment design, and fitting equations) method, the fitting equations between the geometric parameters and evaluation indicators were determined. Taking the minimum values of two evaluation indicators of piston as optimization objectives, artificial bee colony method was run to determine the values of parameters. At last, the two evaluation indicators of the optimized piston were computed. The results indicate that, after optimization, the maximum temperature of piston decreases to be 16.05 K and the maximum stress decreases to be 13.54 MPa. Both temperature and stress conditions of the optimized piston had been improved, which demonstrates the effectiveness of the optimization and the validity of the algorithm.

Friction-induced heat generation between two particles

Friction-induced heat generation, dissipation and the associated rise in temperature are still an intrinsic problem in many fields dealing with granular materials. This work presents preliminary attempts of modelling heat generation and estimating the contact flash temperatures with the use of a theoretical model. To check the robustness of this theoretical model simulations were run in parallel with Finite element method. The maximum contact temperatures obtained from the theoretical model show a good agreement with FEM results. The promising results imply that the simple theoretical model can be used accurately to predict heat generation in granular materials.

Friction stir incremental forming of polyoxymethylene: process outputs, force and temperature

ABSTRACT Despite good creep and fatigue durability, high resistance against chemicals and good surface finish, Polyoxymethylene (POM) has been sidelined in incremental sheet forming (ISF) literature due to its low formability at room temperature. This paper addresses the issue by deploying a cost-effective friction-induced heat at the tool-sheet interface. This work demonstrates a combined experimental, analytical, and numerical approach to investigate the effects of elevated temperature in ISF of POM. For this purpose, the formability of POM was first experimentally investigated under the interactive effects of the process parameters. Employing the membrane analysis approach, the stress state in the FSISF process was defined. The tool-sheet contact area was calculated as a function of toolpath and the relevant process parameters. The Johnson-Cook plasticity model was calibrated based on several universal mechanical tests at various temperatures and rates. Embedding the stress state, contact area, and the material model inside an algorithm developed by adopting the Finite Difference Method, force, friction-induced heat, and temperature at the tool-sheet interface were evaluated. Simulation results were validated by experimental outcomes. A threshold boundary for the maximum allowable tooltip temperature was established to avoid heat-induced defects while ensuring the sheet formability.

Wear and thermal resistance properties of aluminium particulate microcomposites

Wear resistance and thermal stability are not fundamental properties of materials, but their effects are inevitable in applications involving two-body contact because of friction-induced wear and heat. Wear resistance and thermal stability of epoxy containing 10% by weight of 66.34 μm aluminium particles were examined using mass loss per sliding distance approach and glass transition temperature (Tg) was used as a parameter for thermal stability. The results obtained revealed a reduction in the wear rate due to addition of aluminium particles. About 62, 58 and 39% reductions at 9 N/0.65 m s−1; 9 N/1.3 m s−1 and 25 N/1.3 m s−1, respectively imply that both sliding speed (v) and the applied load (F) contribute to an increase in the wear rate. A lower coefficient of friction of epoxy aluminium composites signifies lower surface wear rate in comparison with that of the epoxy polymer upon contact with another body in applications. The linear model establishes that v with a P value of 0.0046 has a greater significant influence on the wear resistance of the composite than F with a higher P value (0.0103). By the model, the epoxy aluminium composite under 24.63 N is expected to experience a wear rate of 0.000537 g m−1 which is 1380% lower than that established by the results of the experiment. About 36% increase in Tg is observed and 2FI model affirms that there is a gradual increase in Tg with heat flow through the sample during the glass transition period. Hence, the 2FI model having adequate precision of 164 > 4 is appropriate to be used for navigating a design phase for thermal stability properties.

Probing the effect of grinding-heat on material removal mechanism of rail grinding

Rail grinding is of vital importance for high-speed railway with safe, reliable and comfortable operation. Here, a self-design grinding machine was applied to evaluate the performance of as-prepared grinding stone (GS) vs Rail under normal loads and grinding speeds. Results illustrate that the increase in normal load leads to the wider and thicker wear debris, but the increasing grinding speed is opposite. Friction-induced heat regulated by working parameters determines the grinding properties of the GSs/Rail contact, high grinding-heat causes the plastic deformation and accelerates the wear. The finite element analysis verifies the source/distribution of grinding-heat and heat flux, thereby revealing the material removal mechanism. It is of great significance for long-term safe and reliable operation of rail via grinding regulation.

A Study on Drilling High-Strength CFRP Laminates: Frictional Heat and Cutting Temperature.

High-strength carbon fiber reinforced polymer (CFRP) composites have become popular materials to be utilized in the aerospace and automotive industries, due to their unique and superior mechanical properties. An understanding of cutting temperatures is rather important when dealing with high-strength CFRPs, since machining defects are likely to occur because of high temperatures (especially in the semi-closed drilling process). The friction behavior at the flank tool-workpiece interface when drilling CFRPs plays a vital role in the heat generation, which still remains poorly understood. The aim of this paper is to address the friction-induced heat based on two specially-designed tribometers to simulate different sliding velocities, similar to those occurring along the flank tool-work interface in drilling. The elastic recovery effect during the drilling process was considered during the tribo-drilling experiments. The drilling temperatures were calculated by the analytical model and verified by the in-situ experimental results gained using the embedded thermocouples into the drills. The results indicate that the magnitudes of the interfacial friction coefficients between the cemented carbide tool and the CFRP specimen are within the range between 0.135–0.168 under the examined conditions. Additionally, the friction caused by the plastic deformation and elastic recovery effects plays a dominant role when the sliding velocity increases. The findings in this paper point out the impact of the friction-induced heat and cutting parameters on the overall drilling temperature.