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The subsurface topography and element distribution of composites specimen for the test of 30°C~100°C: (a) subsurface topography, (b) Si, (c) Al, (d) C, (e) Mg, (f) O, (g) Fe, (h) S, and (i) Ca.
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Due to the low density and high temperature resistance, the SiCp/A356 composites have great potential for weight reduction and braking performance using the brake disc used in trains and automobiles. But the friction coefficient and braking performance are not stable in the braking process because of temperature rising. In this paper, friction and...
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Citations
... The impact of temperature on copper-free semi-metallic friction composites remains understudied. Ongoing developments in brake friction materials provide crucial insights for formulating novel copper-free compositions [20,21]. ...
... The brake discs employed in urban rail trains, comprising of SiCp/A356 composites, endure repeated and intense impacts, as well as substantial thermal-mechanical loads and severe friction during service [1,2]. Prior research has confirmed that the primary contributor to the stress experienced by these brake discs is the thermal stress arising from frictional heat, which accounts for over 80% of the total stress [3]. ...
This article presents a study on the fatigue damage behavior of SiCp/A356 composites in severe service conditions of brake discs. A representative volume element (RVE) was constructed using finite element modeling technology to simulate the microstructure characteristics of the composites which takes into account the fatigue characteristics of the matrix. The RVE was loaded with local strain components and temperature histories obtained through the simulation of the braking condition of an urban rail train. The study found that the alternating effect of compressive stress and residual tensile stress at the matrix near the interface, especially at the sharp corners of SiC particles, causes fatigue damage on the matrix. Brake temperature was identified as the main factor for thermal–mechanical fatigue damage of the brake disc, and the matrix near the high-temperature position of the friction surface was found to have the highest degree of damage and the fastest failure process. The fatigue microcrack morphology and micro-failure modes inside the RVE were in good agreement with those of SiCp/A356 brake disc, and the RVE was able to characterize the micro-fatigue failure behavior of the SiCp/A356 composites under service thermal–mechanical load. This article provides a novel approach for investigating the thermo-mechanical fatigue behavior of SiCp/A356 composites from macroscopic to microscopic.
... Aluminum matrix composites are a kind of designable material with high specific strength [1][2][3], which is widely used in fields such as transportation, aerospace, and electronic packaging [4,5]. SiCp/A356 composites with particle content of 20 wt.% have become one of the ideal materials for brake discs of urban rail train due to their excellent wear resistance and thermal conductivity [6][7][8][9]. The strengthening mechanism of SiCp/Al composites is mainly reflected in two aspects: one is the micromechanical strengthening mechanism based on the load transfer between SiC particles and matrix, and the other is that the addition of SiC particles changes the microstructure or the deformation mode of the matrix, that is, the microstructure strengthening mechanism [10]. ...
This paper investigates the 20 wt.% SiCp/A356 composites used for brake discs through finite element simulation. A Representative Volume Element (RVE) model considers microstructure morphology, particle geometry, content, and the elastic-plastic damage behavior of the matrix. Tensile deformation and damage failure of the RVE at 200°C is simulated. The advisable interfacial strength is determined by combining simulation and experiment. Parametric modeling of SiC particle characteristics (size, shape, distribution) explores their influence on tensile mechanical properties and damage behavior at 200°C. Refining SiC particles (10~25 μm) improves ultimate strength but reduces ductility. Recommended fabrication: SiC particles with 13 μm nominal size, with main distribution between 10 μm and 16 μm, enhancing ultimate strength while maintaining ductility. Increasing the minimum angle of particle sharp corner (>45°) improves both ultimate strength and ductility, ensuring mechanical stability and reducing brittle fracture risk. SiC particle agglomeration accelerates damage initiation, crack propagation, and reduces elastic modulus. Suggested quality control standard: 25% particle agglomeration within a 140 μm × 140 μm field of view. These findings provide insights into optimizing mechanical properties and damage behavior of SiCp/A356 composites for brake discs.
... Excessive heat because of the friction caused specimen strength in sliding interface to be decreased and it led to the decrease of the coefficient of friction [14]. Formation of friction film at high speeds and temperatures possess a crucial role in protecting the friction of material surface from immediate contact with the disc, so the friction film can decrease the coefficient of friction [15]. Fig. 3 also displays that the coefficient of friction increased with increasing volume fraction of rockwool at variation of sliding speed. ...
The effect of different reinforcement material on mechanical and tribological properties of composite friction brake was studied. This paper aims to investigate the effect of rockwool and glass fiber on specific wear rate, friction coefficient, and flexural strength of composite. Composite specimens were manufactured utilizing a sequential processing as follows: mixing of composite ingredients, cold pressing of the mixture, hot pressing of the preformed specimen, and then post curing of the hot molded specimen. Hot press was carried out under a pressure of 20 MPa at 160 °C. Friction characteristics of composite were measured using pin on disc tribometer. Three-point bending test was carried out to obtain composite flexural strength. The results showed that rockwool had a higher effect on increasing coefficient of friction, specific wear and flexural strength of composite compared to glass fiber. Fiber fracture, fiber pull-out and void were found on the fracture surface of the bending test specimens.
... The temperature of the surfaces of the friction pair influences the coefficient of friction [15]. Brake heating has a negative influence for braking quality [16]. ...
... Brake heating has a negative influence for braking quality [16]. Changes in the coefficient of friction simultaneous to temperature changes are owed to certain aspects regarding the changes which happen on a structural level within the friction pair [15]. ...
The aim of the study is the tribological analysis of the crane drum brakes. A theoretical analysis of the wear processes for brake lining was performed and the coefficient of friction under tribological conditions was determined experimentally simulating the operating conditions for three types of brakes. The theoretical study of the wear was oriented towards of determining the lifetime of the brake lining. In the experimental determination of the coefficient of friction, the following parameters were taken into account: the contact pressure between the shoe and the drum; the initial speed of the brake drum; the humidity of the working environment; and the temperature of the drum-brake lining friction surfaces. After performing the experiments, a statistical analysis was conducted, that shows the amount the coefficient of friction is influenced by the previously mentioned parameters: the highest weight was humidity with a value of 35.58%, followed by temperature with a percentage of 23.95%, velocity with 4.54%, and lastly pressure with 4.19%. Furthermore, the equation that expresses the dependence between the coefficient of friction and the parameters is determined. We consider that the results obtained are important for brake manufacturers in order to improve braking efficiency and the safety of overhead cranes
... The application of probe-less tools is limited to thin sheets of size less than 1 mm only [31]. Lyu et al. [32] developed double-sided friction stir spot welding and investigated the outcome of tool and plunge force on the welding quality. The comparison was done with a single-sided FSSW and found that double-sided FSSW can withstand a higher load than single-sided FSSW. ...
... It was because of the high friction generated between the tool and the welded metal from the four edges of the square probe tool. Which heat generation was higher in the welding zone due to high friction [12,32] between the Square probe tool and weld metal. ...
In the present work, an innovative approach for transforming from engineering design to production has been carried out to achieve enhanced joint strength during a new type of friction stir spot welding (FSSW) process. A process for double spot friction stir welding (DSFSW) and double spot zigzag friction stir welding (DSZFSW) has been developed to achieve higher strength in welded joints. Various mechanical properties of these joints were compared with single spot friction stir welding, considering the effect of tool geometry and spindle speed. The welding material chosen for the process was an AA6063 series of 1 mm thickness. The experiments were carried out by using three different probe shape tools at three different spindle speeds. It was found that at low welding speed, the tensile-shear strength of the welding specimen is higher. The DSFSW joints, welded by a triangular probe tool have higher tensile strength as compared to a single spot and DSZFSW joint. It was also observed that at high spindle speed, the hardness value of the welding specimen decreases while the grain size increases.
... Therefore, this leads to a reduction in wear rate [24]. Other possible causes for the reduction of wear rate at very high temperatures include the change in wear mechanism [25]. The effect of temperature on fretting wear was also examined. ...
When friction processes occur, wear is generated. The generation of wear also leads to airborne noise. There have been many research studies on wear and its correlation with airborne noise, but most research has focused on experimental aspects, and theoretical models are rare. Furthermore, analytical models do not fully account for the wear and airborne noise generation, especially at an asperitical level. One model was developed that gave a reasonable quantification for the relationship between wear and airborne noise generation at an asperitical level under room temperature. In this paper, the accuracy of the model is assessed at higher temperatures. Two materials were set up on a tribometer (aluminium and iron) at 300 RPM. The samples were tested at two different temperatures (40 and 60 degrees) and two different loads were applied (10 N and 20 N). The model computed the predicted wear and sound pressure, and it was compared with the experimental results. The errors are larger for the wear than when the model was validated at room temperature. However, the increase in the error for the sound pressure was smaller at higher temperatures (approximately 20–30%). This is due to the assumptions that were made in the initial model, which are exacerbated when higher temperatures are applied. For example, flash temperatures were neglected in the original model. However, when initial heat is applied, the effects of flash temperatures could be more significant than when no heat is applied. Further refinements could improve the accuracy of the model to increase its validity in a wider temperature range.
... Generally graphite, molybdenum disulfide, hexagonal boron nitride (h-BN) and mica are used as solid lubricants; these materials lessen the friction between sliding parts and protect them from severe wear at normal working conditions. But their effectiveness as a solid lubricant at higher temperature is uncertain because of their unique molecular structure and chances of resection with base material (Pan et al. 2017). Some results reported by different authors on the performance of solid lubricants at high temperature are contradictory. ...
... MMCs are being colossally used in automobile and aerospace industries owing to their elevated properties like elastic modulus, hardness, tensile strength, toughness, wear resistance combined with significant emaciate over un-reinforced alloys [1][2][3][4]. The commonly used metallic matrices include alloys of aluminum, magnesium, titanium and iron. ...
Aluminum MMC is being enormously used in automotive and aerospace applications because of their enhanced mechanical properties. Commonly used MMCs are alloys of aluminum, magnesium, titanium and iron. Particulate reinforcement of Al MMCs includes silicon carbide, boron carbide, tungsten carbide, graphite, etc. Aluminum MMCs reinforced with ceramics like neodymium, yttrium, cerium, Pr praseodymium, beryl, etc., are finding a lot of importance. In the current work, investigation of the mechanical properties of Al2024 with beryl as the reinforcement is being carried out. The composites were prepared by stir casting technique. Mechanical properties like tensile strength, hardness and toughness were determined. Microstructural studies and XRD analysis were carried out to check the uniform distribution of beryl particles and chemical composition of the MMC. The experiments were conducted for As-cast and annealed samples. The experimental results revealed that UTS and hardness increased with an increase in wt% of beryl particles up to 6%. But toughness increased with an increase in wt% of beryl particles up to 10% and remained constant. The annealed samples showed a decrease in UTS (18.7%) and hardness (1.8%). The microstructural studies revealed uniform distribution of beryl particles in the composites, and XRD analysis revealed the chemical composition of the MMC and the presence of beryl in composite. Experimental studies reveal that there is an enhancement of UTS by 10.7%, hardness by 11.1% and the toughness from 2 to 5.75 J/m³. The % elongation has decreased from 11 to 6% when wt% of beryl was varied from 0 to 14%.
... Composite structures are always exposed to different ambient temperatures in service [21]. Yuan et al. [22] studied the damping capacity of composites at a high temperature. ...
Mechanical properties of composites manufactured by high-temperature polymer polyether ether ketone (PEEK) with continuous reinforced fibers are closely dependent on ambient temperature variations. In order to effectively study fatigue failure behaviors of composites under the coupled thermo–mechanical loading, a well-established microscopic model based on a representative volume element (RVE) is proposed in this paper. Stiffness degradation behaviors of the composite laminates at room and elevated temperatures are firstly investigated, and their failure strengths are compared with experimental data. To describe the fatigue behaviors of composites with respect to complex external loading and ambient temperature variations, a new fatigue equation is proposed. A good consistency between theoretical results and experimental data was found in the cases. On this basis, the temperature cycling effects on the service life of composites are also discussed. Microscopic stress distributions of the RVE are also discussed to reveal their fatigue failure mechanisms.
