Disk Contact Research Articles

Droplet impact on a flexible disk

In this paper, we simulate the process of two-dimensional axisymmetric fluid–structure coupling of a droplet impacting on a flexible disk. The effects of dimensionless disk stiffness (K = 0.1–1000), Weber number (We = 1–500) and contact angle (θ = 130° and 60°) on the dynamics of the droplet impacting on the flexible disk are analysed. The results indicate that there are five typical impact modes for a hydrophobic surface (θ = 130°) and four typical impact modes for a hydrophilic surface (θ = 60°) within the range of considered parameters. The analysis of spreading factor reveals that a part of the energy is transferred to the substrate, which is manifested as a weakening of the droplet spreading, when the substrate deforms downwards due to the droplet impact; the squeezing of the droplet causes a tendency to flow from the centre of the droplet to the edge, which is manifested as an enhancement of the droplet spreading, when the substrate recovers from the downward deformation. The effect of the substrate flexibility on the maximum spreading factor depends on the competition of the two mechanisms above. Based on this, a modified scaling law of βmax has been proposed by introducing the effective Weber number (Wem). The analysis of impact force demonstrates that the peak of the impact force is related to the deflection of the flexible substrate which is different from that of a rigid wall; and three typical processes of impact force variation have been summarised. In addition, unlike the rigid substrate scenario, there is an energy interaction between the droplet and the flexible substrate after impact occurs, which is classified as three typical energy transformation processes.

Analyzing the Dry Sliding Wear Performance on Aluminum 6061 Alloy Reinforced with SIC And B₄C Hybrid Nanocomposite

Abstract The methodology of enhancing the wear resistance of hybrid Metal Matrix Composites (MMCs) involves reinforcing the metal or alloy with robust materials. This study focuses on the manufacturing of a hybrid nanocomposite, which includes 0.6 vol.% of Silicon Carbide (SiC) and 0.2 vol.% of Boron Carbide (B₄C) nanoparticles with aluminum (Al) 6061 alloy. This is achieved through an ultrasonic assisted stir casting methodology, and a pin-on-disc tribometer is used to investigate the sliding wear rate and Coefficient of Friction (COF). Vicker's microhardness tester evaluated the microhardness of the nanocomposite, revealing it to be 18% harder than the Al 6061 alloy. Further, the metallurgical examination done through Hi-Resolution Scanning Electron Microscope (HRSEM) and X-ray diffraction (XRD) techniques confirmed the existence of SiC and B₄C nanoparticles. The wear experiment was done under diverse input wear experiment variables such as applied load, sliding velocity, and sliding distance, and optimization was done through Taguchi’s technique. Applied load contributed 40.9% to wear rate, and increasing load increased wear rate due to higher pin-counter disc contact pressure. Sliding speed contributed 42.18% to the COF, while increasing it decreased it due to lower pin-disc contact. The worn area inspection revealed an abrasive wear mechanism with substantial surface degradation at higher loads. The study may progress science and develop stronger materials for many purposes.

Biomechanical changes in the lumbar and hip joint after curved periacetabular osteotomy.

The alignment of the spine and pelvis significantly impacts overall body balance; therefore, alterations in hip and lumbar spine biomechanics following curved acetabular osteotomy (CPO) can help surgeons optimize acetabular correction. To achieve this goal, we conducted patient-specific finite element analyses to compare hip and lumbar disc contact pressure (CP) between patients with developmental dysplasia of the hip (DDH) and healthy individuals. Additionally, we examined the influence of CPO on the CP of both the hip and lumbar discs in patients with DDH. We conducted finite element analyses of the hip and lumbar spine before and after CPO and compared them with those of a healthy human model. Subsequently, we simulated CPO on the preoperative model. Nonlinear contact analysis was employed to calculate the CP of the acetabular cartilage and lumbar discs during a single-leg stance. The maximum and average acetabular CP in patients with DDH were 5.4MPa and 4.5MPa, respectively. The average CP for the five lumbar discs were 3MPa, 2.5MPa, 2MPa, 3.5MPa, and 4.4MPa. In contrast, the maximum and average acetabular CP in normal subjects were 3.7MPa and 2.1MPa, respectively, and the average CP of their lumbar discs were 1MPa, 2 MPA, 1.88MPa, 2.1MPa, and 2.1MPa, respectively. After CPO, the maximum and average CP of the hip decreased, as did the average CP of the lumbar discs. The maximum and average compressive stress of the acetabulum decreased to 3.79MPa and 2.3MPa, respectively, and the average compressive stress of the five intervertebral discs decreased to 1.96MPa, 0.79MPa, 0.78MPa, 1.13MPa, and 3.14MPa, respectively. Our finite element analysis indicated that CPO effectively normalizes hip contact pressure while reducing lumbar disc contact pressure. However, further investigation is required to elucidate the specific biomechanical mechanisms underlying these changes.

Experimental and numerical investigation on hyperelastic sealing disc contact behavior in pipeline, a comparison between fluid-driven and pull-through approaches

Pipelines are widely recognized as the safest and most efficient means of fluid transportation. Pipeline pigging, a secure and reliable technique, is employed for both cleaning and sealing pipelines to optimize efficiency. Since pigging operation requires differential pressure (ΔP) to facilitate pig movement, this pressure must correspond to the pipeline's operational conditions. Consequently, studying the required ΔP for sealing discs, which serve as primary sealing elements of pigs, is crucial. The primary focus of this study is to examine the difference between pulling the pig using a cable and propelling it with fluid. Furthermore, the main novelty of this research is to experimentally investigate a single sealing disc and conduct fluid-driven tests on it. To study more precisely, three sealing discs with various thicknesses and the same hardness have been launched into a 6-inch spool test, containing five pipes with different wall thicknesses, resulting in multiple oversize ratios (%OSz). In the experimental study, both fluid-driven and pull-through tests were conducted. The range of discrepancy between two methods varies from 15% to 26% for different oversize ratios which is considerable. Additionally, A 2-D axisymmetric nonlinear numerical simulation was conducted in a finite element software ABAQUS in order to study the behavior of sealing discs. Using a pressure-dependent friction coefficient with the proper hyperelastic model was key to achieving simulations that have good agreements with experimental results, with discrepancy of less than 10 percent in all extracted pressures.

Observation of dynamic position and morphological changes of temporomandibular joint discs under Angle's classification

Objective: To observe the dynamic changes of the temporomandibular joint (TMJ) disc in joint movement under different Angle's classification, providing reference for understanding joint functional movement and providing a basis for more accurate clinical imaging diagnosis. Methods: A total of 30 patients (13 males and 17 females) with temporomandibular disorders who were admitted to Beijing Friendship Hospital, Capital Medical University and General Hospital of the People's Liberation Army from January 2022 to April 2024 were enrolled. Thirty adults (13 males and 17 females) with different Angle's classification, with an average age of (34.4±8.5) years, were subjected to dynamic imaging of their TMJ from the closed position to the maximum opening position, and then to the closed position using MRI. The position and morphological changes of the articular discs were observed. Results: The results showed that volunteers with no displacement of the articular disc in class Ⅰ, Ⅱ, and Ⅲ relationships had different shapes of the articular disc during open and closed mouth movements. However, in the maximum opening position, the articular disc were all located directly below the maxillary nodules, and their shape is double concave. In terms of irreversible anterior displacement of the articular disc, in class Ⅰ Angle, the posterior zone of the disc contacts the anterior inclined plane of condyle from the maximum opening position back to the front of the closing position. In class Ⅱ, the posterior zone of the disc contacts the anterior inclined plane of condyle from the beginning of opening position to maximum opening position. In class Ⅲ, the posterior zone of the disc is always in contact with the anterior inclined plane of condyle throughout the entire movement process. And among them, the articular disc presents a forward displacement state at the closing position, its morphology undergoes folding phenomenon. When the openness is 2.5 cm, the articular disc moves up to a certain extent, and is closer to the anterior inclined plane of condyle, and its shape is also partially changed. When the openness is 4.3 cm, the shape of the articular disc, located between the anterior inclined plane of the joint node and the posterior inclined plane of the condyle, is typical double concave, which is sufficient to show that the articular disc is reversible when maximum opening position is reached. In terms of reversible anterior disc displacement, in class Ⅰ Angle, the posterior zone of the disc contact with the anterior inclined plane of condyle at the beginning of the opening position and the end of the closing position. In classⅡ Angle, the posterior zone of the articular disc is not in contact with the anterior inclined plane of condyle. In class Ⅲ Angle, the posterior zone of the articular disc contact with the anterior inclined plane of condyle at the end of the closing position. Conclusions: Multi level dynamic MR imaging data of the temporomandibular joint can dynamically observe the movement of the temporomandibular joint, intuitively and accurately display the position and shape of the articular disc during movement, and can serve as a useful supplement to static conventional MR imaging of the TMJ. The patient's TMJ needs to reach the maximum opening position in order to determine whether the joint disc displacement can be reversible or not.

Equal heat flux loading optimization approach for uniform wear of the wet brake

Due to their exceptional ability to endure heavy loads, cam-lobe radial-piston hydraulic motors are extensively utilized in heavy machinery. The wet brake is a key part capable of providing highly braking torque, which has numerous friction pairs and a compact structure. However, there exists a challenge in solving the issue of irrational pressure distribution which leads to non-uniform heat flux distribution and severe wear failure of the brake discs. For this, an innovative method to optimize the wet brake's loading structure has been developed to address the issue of non-uniform heat flux distribution. A thermomechanical coupling finite element (FE) model was established to establish a clear correlation between loading structure parameters and contact pressure distribution on the brake disc. An innovative equal heat flux criterion was introduced to guide the optimization process. Simulation results confirmed that the optimized loading structure achieved a brake disc contact pressure distribution aligned with the ideal heat flux density criteria. Experimental validation further demonstrated a notable reduction of up to 44.39 % in maximum wear depth (hmax) across different radii of the brake disc compared to the unoptimized structure. These findings underscore the efficacy of our approach in reducing wear rates and enhancing durability of the wet brakes.

The Effect of Slider Configuration on Lubricant Depletion at the Slider/Disk Contact Interface

With decreasing clearance between the protrusion of a slider and a disk interface, there is a higher likelihood of contact occurring during shock or vibration experienced by hard disk drives (HDDs), which may induce lubricant depletion. Based on the molecular dynamics (MD) model of perfluoropolyether lubricant with a coarse-grained beads spring approach, we compared the slider configurations’ influence on the lubricant transfer volume quantitatively. By further investigating the parameters of the cylindrical asperities, including the width and depth, as well as considering the asperity amounts of the slider, we successfully observed the lubricant depletion process during slider and disk contact. The results demonstrate that the penetration depth was reduced as the asperity amount increased, mainly owing to the increased contact area between the surfaces. The decreasing depth of the asperity and the increasing width of the asperity helped to reduce the depletion volume. In addition, the utilization of a cylindrical slider configuration can contribute to a reduction in lubricant depletion resulting from contact between the head and disk.

Evolution of microscopic characteristics of rolling contact fatigue coexisting with wear of U75V rail

During the damage and defects related to rolling contact fatigue (RCF), together with wear occurring at the rail surface, the microscopic characteristics of the rail material change with the accumulation of wheel cycles. To find the relationship between rail material characteristics and RCF damage under wheel-rail contact situations, a series of twin-disc rolling-sliding tests, based on real wheel-rail contact situations at a radius of 80 mm rail profile, was established for a heavy-haul railway in China. The microscale characteristics of the rail disc contact surface was researched, including crack, wear, roughness, and hardness of the U75V rail with different load cycles. The results show that the damage mechanism of RCF and wear alternately dominates the rail disc surface at the microscale, taking a certain cycle as a boundary which makes the RCF crack number and wear rate have opposite evolutionary trends. The above factors also affect the wear at the surface rail discs, alternating between fatigue and adhesion. Meanwhile, increasing the surface micro-hardness leads to a decrease in the relative wear rate and an increase in the roughness, length and number of RCF cracks. The plastic deformation layers, including the severely deformed layer (SDL) and the transition layer (TL), almost maintain the same thickness and the dynamic equilibrium increases during the cycles. Two kinds of cracks are initiated and propagated at the rail disc surface, one at the SDL and the other at the junction of SDL and TL. The number of each kind of crack depends on the SDL thickness.

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.

Study on the flash temperature phenomenon in the contact area of rolling bearings

PurposeDue to high speeds, heavy loads, large slide-to-roll ratios (SRR) and other variable operating conditions, some rolling bearings that have been working in harsh conditions may experience flash temperatures in the contact area, which may result in early damage like smearing and then affect service life. This study aims to investigate the flash temperature phenomenon of rolling bearings through theoretical and experimental analysis.Design/methodology/approachA technology for measuring temperature distribution in rolling ball on disk contact under lubrication was developed. The test-rig can simulate the ball bearing contact. The effects of working conditions such as entrainment speed, load, SRR and lubricating oil viscosity on the flash temperature were investigated.FindingsThe results of the theoretical calculation and experiments indicate that the parameters promoting the reduction of film thickness in elastohydrodynamic lubrication are always related with the number of flash points, even film thickness reduced to mixed lubrication. The flash temperature is easier to happen in conditions of high SRR, heavy load, slow entrainment speed and low viscosity oil.Originality/valueThis work conducts an experimental study on the flash temperature phenomenon, providing a test technology for bearing lubrication and failure investigation.Peer reviewThis author has opted into Transparent Peer Review available at: https://publons.com/publon/10.1108/ILT-04-2023-0104

РАЗРАБОТКА МЕТОДИКИ ГИДРОДИНАМИЧЕСКИХ ЭКСПЕРИМЕНТОВ С ДИСКОВЫМ РАСПЫЛИТЕЛЕМ

. A technique for hydrodynamic experiments has been developed to study a disk atomizer in a rotary mass transfer apparatus. In the course of experiments, the indicator method determines the average residence time of the liquid on the disk contact device, the volume of liquid retained on the disk contact device, the average diameter of the droplets formed, and the height of the gas-liquid layer

ИНДИКАТОРНЫЙ МЕТОД ИССЛЕДОВАНИЯ КОНТАКТНОГО УСТРОЙСТВА

It is proposed to use the indicator method for the experimental determination of the average residence time of the liquid on the new disk contact device. It is proposed to use an aqueous solution of MgCl2 as an indicator

Friction and vibration behaviours of high-speed train brake system excited by wheel flats

ABSTRACT To study the interface friction and vibration behaviours of brake systems with wheel flat, a rigid-flexible vehicle dynamics model and a finite element model of brake system are developed. These two models are validated using experimental test data. Additionally, an analysis formula of brake system excited by wheel flat is proposed to reveal the tribological behaviours. The results indicate that the wheel flat directly induces the elastic vibration of brake disc and further affects the disc contact, resulting in a significant increase in the contact force, contact stress, friction force and vibration acceleration between the brake interfaces. Furthermore, the proposed model can be used to investigate the related tribological behaviour of brake systems under other complex wheel-rail excitations.

The Effect of Sembukan Leaf Extract (Paederia Foetida) on the Growth of Klebsiella Pneumoniae Bacteria with the Disc Method and the Contact Method

Sembukan leaf (Paederia foetida) is a wild plant which is known to have many benefits and can be used as a medicinal plant. These plants contain bioactive compounds that function as antibacterial. This study aims to determine the ability of sembukan leaf extract to inhibit the growth of Klebsiella pneumoniae. The methods used in this study were disc diffusion and contact methods, with variations in the concentration of curd leaf extract 0%, 25%, 50%, 75% and 100%. The research data obtained were analyzed by One Way ANOVA with 95% confidence level (p<0.05). The best concentration with the disc diffusion method at a concentration of 75% with an inhibitory diameter of 15.25 mm with a strong category and the best percentage of inhibition method on sembukan leaf extract at 69.42% with a bacteristatic category at a concentration of 75%, while the results of the One Way ANOVA test that has been done obtained a significant value of p=0.000 (p<0.05) indicates a significant effect on the administration of sembukan leaf extract against Klebsiella pneumoniae bacteria. The results showed that sembukan leaf extract was able to inhibit the growth of Klebsiella pneumoniae.

The influence of Λ ratio and surface roughness on the initiation and progression of micropitting damage

Micropitting is a major failure mode in gears and rolling bearings. Despite its practical importance, there currently exist no universally accepted design guidelines for its prevention primarily due to the great number of influencing parameters. In the absence of an established criterion, the Λ-ratio (the ratio of lubricant film thickness to surface roughness) is often used as a simple way to assess the risk of micropitting. In this paper we present new data to establish and decouple the individual effects of two of the most important influencing parameters in micropitting: the surface roughness amplitude and Λ-ratio. The experiments are conducted on a triple disc contact fatigue rig and carefully designed to decouple the effect of roughness from that of the Λ-ratio. To isolate the influence of the Λ ratio, we use specimens with the same and very tightly controlled surface roughness and then vary the film thickness by blending different viscosities of the same PAO base oil while keeping all other influential parameters constant. To isolate the influence of surface roughness, we keep the Λ ratio the same using the same PAO oils with appropriate viscosities while changing the RMS roughness of the specimen and keeping other roughness parameters as constant as possible. All tests use case carburised 16MnCr5 gear steel specimens. Results show that higher Λ ratio at fixed roughness produces less micropitting as may intuitively be expected. More importantly, at a fixed Λ ratio the amount of micropitting damage was extremely sensitive to the actual surface roughness, with lower roughness both lengthening the micropitting incubation phase and decreasing the rate of material loss in the micropitting wear phase. This shows that Λ ratio on its own cannot be used to assess the risk of micropitting because it is not able to account for the effects of different roughness levels on micropitting, despite including roughness in its definition. Furthermore, in relative terms micropitting was more sensitive to surface roughness than to Λ. In addition, we show that there exists a sufficiently low surface roughness below which micropitting is unlikely to occur even at extremely low Λ ratios. The results presented here can help in design of gears and other mechanical components to mitigate against micropitting.

Numerical and Experimental Study on Rod-Fastened Rotor Dynamics Using Semi-Analytical Elastic-Plastic Model

Abstract Rod-fastened rotor is the core rotating section of the heavy-duty gas turbine. To accurately analyze its dynamic characteristics, the contact model for the disk contact interface needs to be defined and established. Traditional statistical contact models, including the elastic model and elastoplastic model, cannot describe microscopic atomic behavior during the contact process of asperities, while the microscopic contact behavior of the asperities is one of the main factors in affecting the contact stiffness of the rough surface. In this work, the molecular dynamics simulation of the microscopic contact behavior of the rough surface is carried out and the semi-analytical model is built upon that. The semi-analytical model is later combined with the Timoshenko beam element in modeling the rotor system. The influence of plasticity index and surface roughness on the contact model and dynamic characteristics of the rotor is analyzed. Moreover, the experimental tests of natural frequencies and mode shapes are carried out. The results show that the proposed semi-analytical contact model is effective and more accurate compared to other elastic and elastic-plastic contact models.

Nonlinear Dynamic Characteristics of Multidisk Rod Fastening Rotor with Axial Unbalance Mass Distribution

During long-term operation, the blades of rod fastening rotor are very prone to fault and may cause uneven axial mass distribution. The dynamic characteristics of a multidisk rod fastening rotor with axial unbalance mass distribution are studied. A four-disk rod fastening rotor model was established by the lumped mass method. The mass unbalance on different disks was used to simulate blade faults in different parts, and nonlinear factors such as oil film force and disk contact effect were considered. The fourth-order Runge-Kutta method was used to solve the model, and the spectrum and axis trajectory curves were obtained. The influence of fault location and rotating speed on rotor dynamic characteristics was analysed when there were blade faults on two disks. The results show that a large, unbalanced mass will bring strong nonlinear characteristics. The rod fastening rotor may be in different motion states at different rotating speeds. When the fault position of two disks changes, the changes of bearing spectrum, axis trajectory, and phase difference have regularity. The results can provide a theoretical basis for condition monitoring and fault diagnosis of rod fastening rotor.

Comparison of Paresthesia Mapping With Anatomic Placement in Burst Spinal Cord Stimulation: Long-Term Results of the Prospective, Multicenter, Randomized, Double-Blind, Crossover CRISP Study

ObjectivesSpinal cord stimulation (SCS) is an effective therapy for chronic intractable pain. Conventional SCS involves electrode placement based on intraoperative paresthesia mapping; however, newer paradigms like burst may allow for anatomic placement of leads. Here, for the first time, we report the one-year safety and efficacy of burst SCS delivered using a lead placed with conventional, paresthesia mapping, or anatomic placement approach in subjects with chronic low back pain (CLBP). Materials and MethodsSubjects with CLBP were implanted with two leads. The first lead was placed to cross the T8/T9 disc and active contacts for this lead were chosen through paresthesia mapping. The second lead was placed at the T9/T10 spinal anatomic landmark. Subjects initially underwent a four-week, double-blinded, crossover trial with a two-week testing period with burst SCS delivered through each lead in a random order. At the end of trial period, subjects expressed their preference for one of the two leads. Subsequently, subjects received burst SCS with the preferred lead and were followed up at 3, 6, and 12 months. Pain intensity (visual analog scale), quality-of-life (EuroQol-5D instrument), and disability (Oswestry Disability Index) were evaluated at baseline and follow-up. ResultsForty-three subjects successfully completed the trial. Twenty-one preferred the paresthesia mapping lead and 21 preferred the anatomic placement lead. Anatomic placement lead was activated in one subject who had no preference. The pain scores (for back and leg) significantly improved from baseline for both lead placement groups at all follow-up time points, with no significant between-group differences. ConclusionsThis study demonstrated that equivalent clinical benefits could be achieved with burst SCS using either paresthesia mapping or anatomic landmark-based approaches for lead placement. Nonparesthesia-based approaches, such as anatomic landmark-based lead placement investigated here, have the potential to simplify implantation of SCS and improve current surgical practice.

TRIBOLOGICAL BEHAVIOR OF ALUMINUM COMPOSITES USING TAGUCHI DESIGN AND ANN

In this paper is presented the tribological behavior of A356-based aluminum composites using Taguchi design. Testing of tribological characteristics of aluminum composites was done on a tribometer with block on disc contact geometry. Composite materials were obtained by compocasting. The orthogonal matrix L18 is used to form the experimental design using the Taguchi method. The tribological characteristics of the aluminum composite reinforced with SiC (A356/10 wt.% SiC) were compared to the base material A356 for three sliding speeds (0.25 m/s; 0.5 m/s and 1.0 m/s), three values of normal load (10 N, 20 N and 30 N) and sliding distance of 150 m under lubrication conditions. ANOVA analysis showed that the least wear has a composite material at a load of 10 N and at sliding speed of 0.25 m/s.

An improved deep learning-based algorithm for 3D reconstruction of vacuum arcs.

Extensive attempts have been made to enable the application of deep learning to 3D plasma reconstruction. However, due to the limitation on the number of available training samples, deep learning-based methods have insufficient generalization ability compared to the traditional iterative methods. This paper proposes an improved algorithm named convolutional neural network-maximum likelihood expectation maximization-split-Bergman (CNN-MLEM-SB) based on the combination of the deep learning CNN and an iterative algorithm known as MLEM-SB. This method uses the prediction result of a CNN as the initial value and then corrects it using the MLEM-SB to obtain the final results. The proposed method is verified experimentally by reconstructing two types of vacuum arcs with and without transverse magnetic field (TMF) control. In addition, the CNN and the proposed algorithm are compared with respect to accuracy and generalization ability. The results show that the CNN can effectively reconstruct the arcs between a pair of disk contacts, which has specific distribution patterns: its structural similarity indexmeasurement (SSIM) can reach 0.952. However, the SSIM decreases to 0.868 for the arc between a pair of TMF contacts, which is controlled by the TMF and has complex distribution patterns. Compared with the CNN reconstruction method, the proposed algorithm can achieve a higher reconstruction accuracy for any arc shape. Compared with the iterative algorithm, the proposed algorithm's reconstruction efficiency is higher by 38.24% and 35.36% for the vacuum arc between the disk and the TMF contacts, respectively.