Wear Process Research Articles

Ranking analysis of flyash – basalt fibre – polyamide 66 polymer composites based on the mechanical and sliding wear performance metrics using hybrid AHP-R method

This research work investigates the physical, mechanical, thermal, thermo-mechanical, and dry sliding wear characteristics of hybrid flyash particulates (F-class; 0 – 20 wt.% at the step of 5%)–basalt fibres (chopped; fixed 10 wt.%) reinforced polyamide 66 polymer composites fabricated using the twin screw extruder and injection moulding machine. Taguchi's design of experiment optimization approach is used for parameter optimization of the dry sliding wear process, followed by analysis of variance analysis. Further, the hybrid AHP-R method is used for ranking optimization based on the performance metrics. It is observed that the composition having 15 wt.% flyash particulates optimizes overall performance metrics, hence recommended for industrial parts fabrications. It has an experimental density of 1.23 g/cc, voids content of 5.93%, water absorption of 4.21%, tensile strength of 110.73 MPa, flexural strength of 146.72 MPa, Rockwell hardness of 62.44 HRM, fracture toughness of 4.17 MPa√m, impact strength of 2.06 J, the thermal conductivity of 1.24 W/mK, and specific wear rate of 7.55 × 10−4 mm3/Nm. The overall subjective ranking of the hybrid polymer composites attunes with the objective ranking by the hybrid AHP-R method.

Location and Tracking Mode of Sports Rehabilitation Training With Self-Powered Sensors Based on Particle Swarm Optimization Algorithm

With the growth of the country’s economic strength, people’s living standards have steadily improved. Sports have become the main means to change physical fitness and maintain the per capita health index. The state also puts forward higher requirements for the security work of athletes, elderly groups and rehabilitation patients. Traditional rehabilitation training mainly relies on various sensor devices, such as acceleration sensing, pressure sensing and so on. These devices need a lot of energy to supply power for the equipment in the process of use, which is no longer suitable for today’s modern development environment. Based on the concept of self-powered sensors, this paper proposes a sports rehabilitation training model updated by particle swarm optimization algorithm. First of all, the performance and indicators of self-powered sensor devices are analyzed, and the self-powered electrical components are optimized using friction nano new energy technology. Starting from the basic characteristics of wearable models, we can ensure the consistency of posture in sports rehabilitation. During training, the wearing process will stretch 10% of the length in advance to ensure comfort and sensitivity. According to the results of the test record, the pulse index is clear and obvious, consistent with the actual number of minutes per minute. Finally, the sensor array model and function model are improved under the particle swarm optimization algorithm to realize the positioning and tracking function in sports rehabilitation training. The results show that the wearable training equipment optimized by particle swarm optimization can better locate and track the movement track than the traditional sports rehabilitation equipment. It can adjust the movement posture and protect the safety of trainers. At the same time, it is more prominent in performance and power supply duration.

Research on wheat flour‐making technology based on discrete elements

AbstractThe operating characteristics of a mill's rolling distance and roller speed during wheat‐milling were studied to provide a reference for optimizing the operating parameters of the mill. The high‐performance discrete element method software (EDEM) was used to establish a roller‐crushing system for wheat flour production. Numerical simulations of wheat flour production were performed using this system. It was found that increasing the roller distance of the flour mill machine could reduce the wear of the grinding rolls and the power of the grinding roll system, which reduced the crushing rate of wheat during the milling process. Increasing the grinding roll speed can reduce the wear of the grinding rolls but will increase the wheat‐crushing rate. At a constant fast roller speed, increasing the speed ratio increased the wheat‐crushing rate which reduced the power of the grinding roller system. During the grinding roll wear process, the obtuse and sharp angles gradually disappear. A comparison of the simulation and experimental results shows that the discrete element method can accurately predict the wear of the grinding roll.Practical ApplicationsThe milling machine is a key piece of equipment used for making wheat flour. The rolling distance, speed, and speed ratio of grinding rolls are important operating parameters during mill operation. Selecting specific parameters will directly affect the quality of wheat‐milling and the economic efficiency of the milling enterprise. This study adopted a discrete element method to study the effects of these parameters on wheat milling, providing a good reference for the technical personnel of milling enterprises.

Study on mechanics and high temperature tribological properties of porous bearing cage material

To meet the self-lubricating performance requirements of aerospace bearing cages, poly-ether-ether-ketone (PEEK)-based self-lubricating bearing cage materials were prepared based on the Fused Deposition Molding (FDM) process. The mechanical and tribological properties under high temperature condition (200°C) of the porous self-lubricating materials were researched. The results of microstructure analysis of porous sample showed that under laboratory conditions, NaCl can exhibit excellent pore-forming effect and could be effectively removed. The mechanical test results showed that the mechanical properties of the samples showed a significant decrease with the increase in porosity, and were affected by the synergistic effect of pore creation. However, the mechanical properties of heat-treated samples can meet the performance requirements of the bearing cage. The results of the tribological performance tests under high temperature conditions showed that the wear process of the dense samples was more smoother. Further comparing with the tribological properties at room temperature, it was found that the wear resistance of PEEK samples decreased under high temperature conditions. The normalized results of the mechanical and tribological properties data show that the samples with 50 wt% of porogenic agent can express the most balanced and excellent overall performance.

Experimental investigation of the tire wear process using camera-assisted observation assessed by numerical modeling

This paper presents a novel experimental method to study the abrasion mechanism of car tires. It is based on the detection of microscopic movements associated with material damage (cracking) on the rubber tread. This is referred to as degrading layer relaxation. It correlates with the wear rate and, interestingly, the direction of the pattern’s movement is opposite to the lateral forces during cornering. To measure and analyze the microscopic movements, a new camera-based method with feature point matching using video stabilization was developed. Besides extensive experimental investigation, the formation and propagation of microcracks are investigated using a simplified numerical model in which a phase field approach coupled with a viscoelastic constitutive behavior is implemented in a finite element framework.

Experimental Study on Friction and Wear Characteristics of Hydraulic Reciprocating Rotary Seals

Wear is one of the main failure causes of hydraulic seals. Wear will lead to degradation in the mechanical properties and sealing properties of seals. Compared with hydraulic seals with one-way rotational motion, the hydraulic reciprocating rotary seals work in more complex operating conditions, so their wear mechanism becomes more complicated. Aimed at exploring the friction and wear law of hydraulic reciprocating rotary seals and the property evolution law during the wear process, this paper set up an experimental system to simulate the working conditions of the hydraulic reciprocating rotary seals. The friction characteristics were obtained under different working pressures and different motion parameters. The wear characteristics were obtained under rated working conditions. The surface morphology was observed by SEM and the wear mechanism was analyzed.

Optimal design in bionic wear-resistant structures by multiscale DEM simulation

To address the problems of long optimization times of bionic wear-resistant structures in discrete element simulation. We established two-dimensional homoscale discrete element simulation models for four biomimetic structures, along with their respective abrasive wear computational models. We then deliberated upon their wear behavior in relation to the structural morphology, contact constraints, contact force, and wear volume during the wear process. The study found that the shedding of brittle wear body surface abrasives had little effect on the substrate of the bionic structure. Based on the above findings, a multi-scale/cross-level study of the interaction between biological wear surface structure and abrasive was conducted. The findings evince that utilization of a multi-scale computational model ensures the precise examination of the mechanical response of a material to external forces, while also economizing computational time. Finally, the design of the conical bionic structure is optimized based on the multi-scale/cross-level computational model. The results show that the conical bionic structure has good wear resistance when the abrasive grain size is small and when the monomer spacing is not larger than the monomer width. The bionic structure/abrasive interaction multi-scale numerical simulation system established in this paper reduces the complexity of dynamic numerical simulation of wear behavior on the surface of wear- resistant organisms, improves the calculation efficiency, and provides an important research means and method for optimizing the design of bionic wear-resistant parts.

Evolution of Fretting-Induced Cracks and Delamination Wear on Alloy 690 Steam Generator Tubes During Mixed Fretting Regime in Air at Room Temperature

The occurrence of fretting-induced cracks and delamination wear processes in a mixed fretting regime on Alloy 690 steam generator tubes against 304L stainless steel pads was analyzed. Fretting tests in 90° cross-cylinder configuration were performed in air at room temperature. Changes in the contact conditions were evaluated using the energy ratio and the sliding ratio criteria. Damage was characterized using light microscopy, scanning electron microscopy, and optical profilometry. Vickers microindentation was applied to characterize the initial plastic deformation process. It was found that during the initial 1 × 103 cycles, plastic deformation constitutes the main damage mechanism. Thereafter, between 1 × 103 and 1 × 104 cycles, cracks nucleation and propagation accompanied by negligible wear were detected. Beyond 1 × 104 cycles, the dominant main damage mechanism consists of delamination wear assisted by cracks coalescence, and a change from a U-shaped to a W-shaped scar profile was observed in correspondence with the appearance of the delamination wear process.

ОПРЕДЕЛЕНИЕ НА СТЕНДЕ ВИБРАЦИОННЫХ ХАРАКТЕРИСТИК ФУНКЦИОНИРОВАНИЯБОК ПЕРЕДАЧ И В ПОДШИПНИКОВ КОРОЛИЯНИЯ НА НИХ ЭКСПЛУАТАЦИОННЫХ ДЕФЕКТОВ

The functioning of mechanical units of vehicles, in particular, the transmission, is associated with the course of wear processes, leading to changes in the structural parameters of their elements. These include a reduction in geometric dimen-sions and shapes, leading to the appearance of excessive vibrations and beats. The study of vi-bration characteristics can serve as a basis for identifying various defects and damages that oc-cur during their operation, as well as determining their degree. The most rational, from this point of view, are the tests on the stand.

High-temperature wear mechanism of roller cone bit spiral seal

When drilling, the spiral seal of the roller cone bit and the journal are prone to collision and wear, and the friction heat and downhole high temperature will affect the wear process. The friction and wear experiments of the spiral seal material (20CrNiMo–40Cr) at different temperatures were carried out to study the wear mechanism of the spiral seal and journal of roller cone bit at high temperatures to determine the wear amount, friction coefficient and main wear forms. The wear model of friction pairs is established based on the Archard wear model and experimental results; The wear results at different temperatures are obtained by establishing the spiral seal structure model and simulation research of the roller cone bit. The results show that:(1) Through the friction and wear experiment of friction pair materials, the higher the temperature is the greater the wear amount and friction coefficient are. When the temperature exceeds 100 °C, the wear amount and friction coefficient begin to decline with the increase in temperature. By observing the wear surface morphology, abrasive and adhesive wears occur simultaneously, and the main wear form is adhesive wear under high-temperature conditions.(2) The maximum temperature rise caused by friction and the relationship between wear volume and time at different temperatures are obtained through the simulation of the spiral seal structure. Taking the groove depth value as the index to evaluate the sealing effect, the roller cone bit works in the temperature range (25 °C-400 °C), and high-temperature wear does not affect its sealing performance.

Study on Friction and Wear Properties of Copper-Impregnated Carbon Slide Plate Under Different Humidity Conditions

The pantograph–catenary system is one of the most commonly used power-receiving modes of metro trains. Its friction and wear performances are related to the safety and stability of train operation. In this study, a copper-impregnated carbon slide plate material, widely used in numerous metro lines in China, is considered as the research object. The problem of abnormal wear of slide plates caused by the decrease in relative humidity in the autumn and winter in tunnels is studied. Current-carrying friction and wear tests under humidity conditions of 20%, 30%, and 40% relative humidity (RH) are performed to reveal the mechanism of seasonal abnormal wear of slide plates and provide a reference for the service of pantograph slide plates under low-humidity conditions. The results reveal that relative humidity significantly influences the wear process of slide plates; further, the wear rate decrease with an increase in relative humidity. As observed by laser scanning confocal microscopy, with an increase in the relative humidity, the mechanical wear of the slide surface is weakened, arc erosion is enhanced, and surface roughness is increased. The Raman spectral scan showed that with the increasing humidity, the graphitization of the surface material decreased significantly, and the molecular structure changed greatly. Scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS) analysis reveal that under high humidity conditions, a relatively complete oxide film forms on the slide plate and plays a role in lubrication and protection.

Striated pattern on worn surface of a retrieved TKR Tibial insert stems from microstructural changes in the UHMWPE

Polyethylene wear has been a concern for the longevity of total knee replacements (TKR). A characteristic wear feature often observed on the articular surfaces of retrieved polyethylene tibial inserts is a striated pattern of hills and troughs. This pattern is of interest because its surface area has been found to correlate with increased tibial insert wear. We therefore addressed the following two research questions: (1) What is the prevalence of the striated pattern on a contemporary tibial insert design made from conventional ultra-high-molecular-weight polyethylene (UHMWPE)? (2) Are the peaks and troughs of the striated pattern connected with differences in crystallinity developed during the wear process? The prevalence and area coverage of the striated patterns were determined on a set of 81 retrieved tibial inserts of a cruciate-retaining TKR design. The striated areas were mapped using an optical coordinate measuring machine. Differences in crystallinity between troughs and hills were determined on a representative tibial insert using Raman spectroscopy. The striated pattern was observed on 61 out of 81 (75%) of the retrieved tibial inserts, covering an average of 32% of the total articular area. In the representative insert that was evaluated, the hills exhibited higher crystallinity (68%) than the troughs (54%) (p = 0.001). Conversely, the troughs exhibited higher amorphous phase content (22%) than the hills (19%) (p = 0.04). In conclusion, this pattern of hills and troughs is another example of microstructural changes in UHMWPE stemming from tribological stresses.

Comprehensive evaluation of surface parameter correlation in running-in wear process

The first wear process is running-in, which is a stage of each machine system must go through. The friction pair’s surface topography is an important feature of the running-in process. After running-in, the surface topography directly affects the performance in stable working state. The wear performance of the contact pair was focused on by mostly existing studies after a time; however, we should consider the correlation of the surface topography before and after running-in. In fact, exploration of this problem is significantly important to extend the service life of machine parts and improve the running performance. Based on the three-dimensional (3D) surface topography parameter evaluation method, in this study, experiments were designed to analyze the effect of the unworn surface topography on that after running-in, and investigated the correlation of 3D surface topography parameters. The results demonstrated that the topography characterization parameters, i.e., Sa, Sq, Sv, Sdc, Str, Sdq, and Sdr under different working conditions maintained a strong autocorrelation (the correlation coefficient of the same parameter). Moreover, the cross-correlation (the correlation coefficient between different parameters) among height parameters (Sq), hybrid parameters (Sdq, Sdr), and functional parameters (Sdc, Sk) was strong. The results of the surface roughness parameters found in this study can be used as input and output feature selection research based on working conditions and surface topography prediction after the modeling research of running-in surface topography.

Ayurvedic concept of Ahara Rasa and Rasa Dhatu

According to Ayurveda, food is the main pillar of healthy life. Living body is continuously subjected to wear and tear process. Dhatus which are being lost in physiological activities are replenished by food and water. Man needs to eat food to build a new Dhatus and to repair damage Dhatus. After consumption food is digested in gastro intestinal tract. Fluid formed from the digested part of food is called as Ahara-Rasa. For growth, Dhatus needs nourishment, and these Dhatus are nourished by food and water. Aahar Rasa is formed in Annavaha Srotas. Aahar Rasa contains nutrients of seven Dhatus. Aahar Rasa is absorbed from Grahani (small intestine) and brought into heart. Heart is a root of Rasavaha Srotas, hence in heart, Rasa Dhatvagni transforms nutrients of Ahara Rasa into stable Rasa Dhatu. Rasa Dhatu is formed in Rasavaha Srotas. Rasa is the first Dhatu formed from Aahar-Rasa.

Certain concepts and definitions of the physical process of wear of friction discs of sewing machine clutches

The article covers analytical research of the performance of the pads of the friction clutch of the sewing machine. The results of research showed that the wear resistance of the pads decreases with increasing temperature. The wear resistance of pads made of different materials tested on the same type of friction clutch of sewing machine is different. The research has been carried out to determine the maximum value of the specific work of slipping and thermal impulse which determines the characteristics of the temperature field of the friction pair which significantly affects the wear resistance of the friction interface. The wear resistance of friction clutches which are one of the main characteristics that determine the reliability and durability of the friction assembly has been studied.

Tool anisotropic wear prediction and its influence on surface topography in diamond turning of oxygen-free copper

Oxygen-free copper components are widely used in high energy physics engineering, which are usually fabricated by the diamond machining process for achieving low roughness surface. However, the wear of diamond tool heavily affects the surface quality. In this work, the wear law of diamond tool in machining of oxygen-free copper is studied with consideration of the anisotropy of diamond strength. Firstly, the stress distribution on the tool face in machining is calculated. The results show that the cutting stress near the flank face is larger than that near the rake face. Secondly, the strength distribution of tool cutting edge is modeled. The theoretical prediction reveals that the anisotropy of diamond crystal leads to the great differences in the strength of cutting edge at different positions, and further affects the cutting edge wear resistance. Thirdly, the wear model of diamond tool is established with consideration of cutting stress distribution and tool edge strength, in which the mechanical wear is the dominant wear process. Finally, the variation of the surface roughness is analyzed on the basis of the tool wear through the cutting experiments. The experiment results indicate that the surface material deformation is closely related to the tool cutting edge wear transition area and results in different values of surface roughness. The obtained results can improve the understanding of the diamond tool wear law and estimate the diamond tool wear in machining of oxygen-free copper.

Tool wear process monitoring by damping behavior of cutting vibration for milling process

Tool wear process is a complex thermo-mechanical coupling dynamic process. Tool wear will cause the change of the dynamic property of the cutting process, namely the process damping. A new method for monitoring tool wear by on-line recognition of damping behavior of cutting vibration is presented. By modeling the milling force of worn tools, the influence of tool wear on milling force and cutting vibration is analyzed. For accurately identify the time varying process damping with tool wear increases, the vibration component near the dominant mode of cutting system is extracted from cutting vibration signal, and the local mean damping ratio is calculated using the instantaneous frequency (IF) and the instantaneous amplitude (IA). The method performance is demonstrated through experimental data of milling. The results indicate that the local mean damping ratio of milling vibration increases with tool wear, which can clearly indicate the wear progression of tool. The method provides an effective monitoring index for tool wear monitoring in machining.

The Influence of Hardness and Toughness on Wear Temperature Dependence of Stainless Steels

The sliding wear behaviors of three typical stainless steels with various microstructural characteristics, including 2205 duplex stainless steel (2205 DSS), 304 austenite stainless steel (304 ASS), and 430 ferritic stainless steel (430 FSS), are investigated at 20 and −120 °C to address wear failure under cryogenic environment conditions for applications such as spacecraft, polar exploration ships, and liquefied gas storage units. Results show that the wear resistance at 20 °C primarily depends on the initial hardness and strain hardening capacity, whereas toughness becomes increasingly important at −120 °C. The wear resistance of 2205 DSS is slightly higher than that of 304 ASS at 20 °C but much higher than that of 430 FSS. As the temperature decreases to −120 °C, the wear resistances of both 2205 DSS and 304 ASS improve due to the enhanced hardness and favorable toughness endowed by fine grains and the stimulated transformation‐induced plasticity (TRIP) effect, respectively. In contrast, owing to the significant decrease in the toughness of 430 FSS, the worn surface delaminates and the wear resistance deteriorates. Therefore, the effect of toughness on the wear process is not negligible. This study provides guidance for the selection of wear‐resistant materials for different service temperatures.

Thin TiN coating on NiTi substrate through PVD method: improvement of the wear resistance

ABSTRACT The preparation of a thin hard coating is the main challenge in the coating of NiTi articles. To achieve a thin coating of titanium nitride (TiN) on NiTi substrate, physical vapour deposition (PVD) was proposed in this study. Deposition of TiN coating was carried out at the nitrogen flows of 0.79 and 0.93 Pa. Phase composition, thickness, porosity, adhesion strength, hardness, and tribological properties of the TiN coatings were evaluated. The adhesion of the coating to the substrate was acceptable. Increasing of the gas flow resulted in a higher thickness (1 μm), lower porosity and higher adhesion strength. On contrary, the samples prepared with the lower gas flow showed higher hardness and elastic modulus. The coated samples showed smaller width of wear, lower wear rate and lower friction coefficient in comparison to the substrate. The delamination and adhesive wear mechanisms govern the wear process.

The hierarchy of coupled sleep oscillations reverses with aging in humans.

A well-orchestrated coupling hierarchy of slow waves and spindles during slow wave sleep supports memory consolidation. In old age, duration of slow wave sleep and number of coupling events decreases. The coupling hierarchy deteriorates, predicting memory loss and brain atrophy. Here, we investigate the dynamics of this physiological change in slow wave-spindle coupling in a frontocentral electroencephalography position in a large sample (N=340, 237 female, 103 male) spanning most of the human lifespan (ages 15-83). We find that, instead of changing abruptly, spindles gradually shift from being driven by-, to driving slow waves with age, reversing the coupling hierarchy typically seen in younger brains. Reversal was stronger the lower the slow wave frequency, and starts around midlife (∼age 40-48), with an established reversed hierarchy at age 56-83. Notably, coupling strength remains unaffected by age. In older adults, deteriorating slow wave-spindle coupling, measured using phase slope index (PSI) and number of coupling events, is associated with blood plasma glial fibrillary acidic protein (GFAP) levels, a marker for astrocyte activation. Data-driven models suggest decreased sleep time and higher age lead to fewer coupling events, paralleled by increased astrocyte activation. Counterintuitively, astrocyte activation is associated with a back-shift of the coupling hierarchy (PSI) towards a "younger" status along with increased coupling occurrence and strength, potentially suggesting compensatory processes. As the changes in coupling hierarchy occur gradually starting at midlife, we suggest there exists a sizable window of opportunity for early interventions to counteract undesirable trajectories associated with neurodegeneration.Significance StatementEvidence accumulates that sleep disturbances and cognitive decline are bi-directionally and causally linked forming a vicious cycle. Improving sleep quality could break this cycle. One marker for sleep quality is a clear hierarchical structure of sleep oscillations. Previous studies showed that sleep oscillations decouple in old age. Here, we show that, rather, the hierarchical structure gradually shifts across the human lifespan and reverses in old age, while coupling strength remains unchanged. This shift is associated with markers for astrocyte activation in old age. The shifting hierarchy resembles brain maturation, plateau, and wear processes. This study furthers our comprehension of this important neurophysiological process and its dynamic evolution across the human lifespan.