Effects Of Different Working Conditions Research Articles

Deformation and Force Analysis of Utility Tunnel joint under Longitudinal Uneven Foundation

To study the regularity of force and deformation of utility tunnels under longitudinal uneven foundations, considering the traffic load, the authors established a finite element model based on pipe-soil interaction to analyze the effect of different working conditions on force and deformation of utility tunnel joints. The results indicated that different stiffness of the foundation can lead to different mechanical properties of the utility tunnel top plate, bottom plate and socket joints. The deformation of the bell joint which on the undisturbed soil and located 2 to 3 sections pipes to the replacement junction changes most obviously, meanwhile, as the longitudinal stiffness difference increases, the maximum horizontal opening on the top plate shifts closer to the replacement junction, and the maximum opening up to 3.561mm; the phenomenon of axial stress below the waterproof requirement exists in the interface of the top plate on the undisturbed soil and the interface of the bottom plate on the replacement soil at the difference in stiffness of the foundation is greater; the maximum differential settlement of joint is located the first corridor interface to the replacement junction which on the undisturbed soil, that is characterized by ‘decreasing from the replacement junction to both sides’.

Study on the permanent deformation of asphalt mixtures based on the modified Burgers model

Based on the confined test results and the viscoelastic constitutive model of asphalt mixtures, a three-dimensional finite element model of an asphalt pavement was established to study the effect of different working conditions on asphalt pavement. With the actual pavement structure response, a comparative analysis was conducted to assess the stress and strain experienced by the asphalt pavement under various working conditions. The results show that the asphalt pavement structure model can reflect the effect of different working conditions on asphalt pavement; the transverse stress and strain of asphalt pavement are most significantly affected by the working conditions during cornering, and the position of the maximum value is concentrated on the outer edge line of the wheel and a distance away from it; however, the longitudinal tensile stress and strain of the asphalt pavement are most significantly impacted by the working conditions of driving and braking, and the position of the maximum value is mainly distributed in the center line of the single wheel. The research results can provide a reference for the design of asphalt pavement structures.

Study on contact and vibration characteristics of composite cylindrical roller bearings

PurposeThe purpose of this paper is to establish a dynamic analysis model of composite cylindrical roller bearings, investigate the effects of different working conditions on the kinematic characteristics of composite bearings and compare the differences between them and solid roller bearings.Design/methodology/approachThis paper establishes a dynamic analysis model for composite cylindrical roller bearings and proves the correctness of the established model by establishing dynamic vibration experiments and contact theory for composite roller bearings. Comparative analysis was conducted on the effects of coupling changes in rotational speed, load, number of rollers and filling ratio on parameters such as bearing static stiffness, contact stress and vibration acceleration.FindingsThe composite roller can enhance the bearing’s operational stability and minimize contact stress, but that a higher filling ratio is going to increase the bearing’s stiffness. The acceleration degree of bearing vibration, the load on the outer raceway nodes and the bearing stability all decrease as inner ring speed rises.Originality/valueA dynamic calculation model of composite cylindrical roller bearings is established, and the influence of multiparameter coupling changes on bearing vibration and contact is studied, which lays a foundation for the structural improvement of the bearings.

Tribological characteristics and wear mechanisms of reinforced composites against steel

To explore the potential wear performance of commonly utilized hydraulic system polymer components, we investigated the effects of different working conditions on the frictional and wear behaviors of three polymer sealing materials in this study. Polytetrafluoroethylene (PTFE), nylon (PA), and polypropylene (PP) composites were prepared using copper (Cu) and glass fiber (GF) as fillers. The tribological and wear properties (wear rate, surface appearance, wear patterns) of the sealing composites were evaluated. The results showed consistent trends toward increasing average coefficient of friction as load and speed increased for PTFE. The incorporation of filler improved the wear resistance of the composites. The addition of Cu particles showed lower coefficient under higher load and sliding speed. PA with continuous glass fiber (CGF) sealing composites showed lower coefficient, less wear volume, and relatively smoother wear zone surfaces than PTFE-based composites or PP with short glass fiber (SGF). We propose that PA-CGF outperforms other materials in regards to fatigue and friction and wear even under extremely high silding speed,as well as sealing properties.

Effect of different working conditions on tribological behaviors of PcBN/440c stainless steel in vacuum environment

Polycrystalline cubic boron nitride (PcBN) is a widely used tool material for cutting hard materials under high-speed and heavy-duty cutting conditions. As the need for in-orbit manufacturing and service in vacuum environment of outer space grows, understanding the tribological behavior of PcBN tools during vacuum operation becomes increasingly important. This study investigates the effect of different working conditions on the tribological behavior of PcBN discs and high‑carbon chromium alloy steel (440c) balls in vacuum. The tribological behavior of tribopair is analyzed. The experimental results reveal that the average of coefficient of the friction (CoF) is generally lower at 100 r/min than at 300 r/min and decrease with increasing load at two different speeds. The CoF of the 300 r/min group exhibits greater ups and downs at different load cases. The wear rate increases and then decreases with increasing load at different speeds. These fluctuations in CoF and wear rate are attributed to the transformation of the wear form and the effect of frictional heat build-up. Based on the SEM and EDX results, the wear mechanism is predominated by abrasive wear, gradually transitioning to adhesive wear with increasing loads. These findings provide insights into the tribological behavior of PcBN composite materials in vacuum. The results aim to inform the development of more efficient and dependable PcBN tools for in-orbit manufacturing and service applications.

Isogeometric FE-BE method with non-conforming coupling interface for solving elasto-thermoviscoelastic problems

The isogeometric finite element (FE) and boundary element (BE) coupling method with non-conforming interface is applied to solve 3D elasto-thermoviscoelastic problems. The thermoviscoelastic constitutive relation is expressed by Stieltjes integral, and the equivalent integral weak form of the problem is derived according to the principle of virtual work, in which the time integral is discretized by the trapezoidal difference approximation formula. The parameters of viscoelastic material are described by Prony series, and the discrete formula can be simplified by recursive relationship to avoid storing all solutions in time steps. The equilibrium and compatibility conditions of FE and BE subdomains on the coupling interface are used to couple two different system matrices, and the coupling of non-conforming non-uniform rational B-splines (NURBS) surfaces in different subdomains is achieved by using virtual knot insertion technique. In addition, the time-temperature equivalent principle is applied to observe the mechanical behavior of viscoelastic materials over a wide temperature range in a short time. Through several numerical examples, the effects of different working conditions and geometrical parameters of combustion chamber on the structure of the solid rocket motor (SRM) are studied, and the correctness and robustness of this method are verified.

Study on Downhole Throttling Characteristics of High Water Content Gas

In order not to hinder gas production, we usually hope that the bottom hole effusion can be discharged to the surface with high-pressure natural gas. For the production data of high water content gas wells, the problems of insufficient water content and liquid-carrying capacity affecting gas well production should be considered. Based on the wellbore gas-liquid two-phase pipe flow theory and heat transfer theory, the temperature and pressure coupling prediction model of a high water-bearing gas well is established. Combined with the downhole throttling mechanism and gas-liquid two-phase homogeneous flow theory, the temperature and pressure field distribution model is established. The results show that compared with the Ramey model and Hassan and Kabir model, the temperature and pressure coupling prediction model of high water-bearing gas wells established in this study has the smallest coefficient of variation in the four groups of data tests. Based on this, the effects of different working conditions and choke diameter on downhole throttling characteristics of high water-bearing gas wells are analyzed. The findings of this study are helpful to better predict the wellbore temperature and pressure coupling of high water-bearing gas wells and provide more effective help for the smooth production of gas wells.

Failure analysis of extractor slipping in the cartridge case extraction process under different working conditions

A cartridge case extractor is a component which is used to extract cartridge cases out of a gun barrel. The extractor slipping from the cartridge case is a kind of motion failure caused by the coupled effects of friction and deformation. Certain working conditions have significant effects on this failure mode. In this study, a method for analyzing the failure behavior and condition of the extractor slipping is presented. The failure mode and theoretical model of the extractor slipping are firstly discussed. A finite element model is then established to simulate the cartridge case extraction process of a machine-gun. The effects of different working conditions, including ambient temperature, number of consecutive shots, and friction coefficient, on the cartridge case extraction process, are also analyzed. A concept of critical friction coefficient under a specific working condition is introduced in the extractor slipping condition analysis. The experimental results are also illustrated to verify the simulation results. Finally, the sensitive parameters of the extraction mechanism are analyzed and redesigned based on the established simulation model in order to reduce the failure rate of the cartridge extraction process.

Analysis of upper-limb muscle fatigue in the process of rotary handling

Workers engaged in repetitive manual material handling (MMH) generally suffer from work-related musculoskeletal disorders (WMSDs), particularly in the arms, shoulders, neck, and waist; this significantly limits the individual's strength and ability to work. Currently, research on upper-limb injuries affecting manufacturing workers focusses on the effect of different working conditions on specific muscle fatigue. However, research on the fatigue transformation relationship among various muscles in the process of working is lacking. Therefore, the purpose of this study was to investigate the fatigue changes between the upper-limb muscles during rotary handing. In this study, 13 male subjects were studied to simulate rotating handling during the manual handling process using surface electromyography (sEMG). Handling angles of 90°, 45°, and 0° were arranged as single variables to conduct the single-factor experiment. The sEMG of the brachioradialis, biceps brachii, trapezius, and multifidus muscle was measured during the operation. The results of this study indicate that the characteristics of muscle fatigue are different at different rotation angles: the multifidus muscle and trapezius were fatigued when the rotation was 90°. Under the condition of a 45° rotation, the activities of the four muscles fluctuated significantly. The slope of the median frequency of the muscles was positive, the load of the four muscles was evenly distributed, and no local fatigue was observed. Under the condition of a 0° rotation, the sEMG indicated that the brachioradialis muscle was fatigued, while the other three muscles had lower loads.

Temperature of Grinding Carbide With Castor Oil-Based MoS2 Nanofluid Minimum Quantity Lubrication

Abstract Nanofluid minimum quantity lubrication (NMQL) has better stability, higher thermal conductivity, and excellent lubrication performance compared with traditional flood lubrication. The heat transfer model and finite difference model were established to verify the feasibility of NMQL conditions in grinding cemented carbide. Based on them, the grinding temperature of cemented carbide is calculated numerically. Results show that the grinding zone temperatures of flood grinding and NMQL are lower, 85.9 °C and 143.2 °C, respectively. Surface grinding experiments of cemented carbide YG8 under different working conditions are carried out. Dry grinding (227.2 °C) is used as the control group. Grinding zone temperatures of flood grinding, minimum quantity lubrication, and NMQL decrease by 64.2%, 39.5%, and 20.4%, respectively. The error is 6.3% between theoretical calculation temperature and experimental measurement temperature. Based on machining process parameters (specific grinding force, force ratio) and experimental results (microstructure of grinding wheel, workpiece, and grinding debris), the effects of different working conditions on wheel wear are studied. NMQL achieves the highest G ratio of 6.45, the smallest specific grinding force, and the smallest Fn/Ft ratio of 2.84, which further proves that NMQL is suitable for grinding cemented carbide.

Influence of wheel-diameter difference of the same locomotive on ride quality of locomotive

The existence of wheel-diameter difference of track locomotive will directly affect the motion performance of locomotive. In this paper, the creep force of coaxial wheel-diameter difference is analysed, and the dynamic model of 2-axle bogie locomotive is established by SIMPACK software. Based on the study of two typical wheel-diameter difference of the same bogie, 10 special working conditions of wheel-diameter differences of the same locomotive are put forward. The effects of different working conditions and different wheel-diameter differences of the same working condition on the straight line motion performance of locomotive are analysed. The results show that, the lateral displacement and lateral ride quality index of locomotive body increase with the increase of wheel-diameter difference under the same working condition, and they do not exceed the safety limit. The change of wheel-diameter difference has little effect on the vertical ride quality index of locomotive body. According to the lateral displacement of the locomotive body, the 10 working conditions are divided into three grades. The third grade (working condition 4, working condition 5, working condition 8 and working condition 11) is more conducive to the safe and stable motion of the locomotive. Therefore, in the wheel matching installation and repairing process, priority should be given to the arrangement of wheel-diameter difference of the same locomotive in the third grade. This will provide a reference and basis for the scheme of locomotive wheel economic repairing.

Electrohydrodynamic behaviors of droplet under a uniform direct current electric field**Project supported by the National Natural Science Foundation of China (Grant Nos. 51725602 and 51906039) and the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20180405).

The electrohydrodynamic behaviors and evolution processes of silicone oil droplet in castor oil under uniform direct current (DC) electric field are visually observed based on a high-speed microscopic platform. Subsequently, the effects of different working conditions, such as electric field strength, droplet size, etc., on droplet behaviors are roundly discussed. It can be found that there are four droplet behavior modes, including Taylor deformation, typical oblique rotation, periodic oscillation, and fracture, which change with the increase of electric field strength. It is also demonstrated that the degree of flat ellipse deformation gets larger under a stronger electric field. Moreover, both of the stronger electric field and smaller droplet size lead to an increase in the rotation angle of the droplet.

Numerical simulation of hydrate slurry flow characteristics in vertical pipes based on population balance theory

Solid fluidised mining uses mechanical means to break down hydrates in the seabed. Then the hydrates will be mixed with seawater and transported to secondary crushing and other pre-treatments. Finally, the hydrates will enter the vertical lift pipe and be sent to the platform or mining ship. Therefore, the study of the flow characteristics of hydrate slurry in vertical pipes is of great significance for hydrate mining. To study the effect of different working conditions on the flow characteristics of hydrate slurry in vertical pipes, the flow characteristics of hydrate slurry in vertical pipes were simulated using the population balance theory based on hydrate particle aggregation dynamics. This paper focuses on the simulation of the flow characteristics of hydrate slurry with different initial particle sizes, concentrations and velocities, and according to the simulation results, the flow characteristics of hydrate slurry such as pressure drop, concentration distribution, and hydrate particle size distribution are analysed. The results of this study can provide referenced for the flow characteristics of hydrate slurry in hydrate mining. [Received: October 6, 2018; Accepted: March 29, 2019]

Numerical simulation of hydrate slurry flow characteristics in vertical pipes based on population balance theory

Solid fluidised mining uses mechanical means to break down hydrates in the seabed. Then the hydrates will be mixed with seawater and transported to secondary crushing and other pre-treatments. Finally, the hydrates will enter the vertical lift pipe and be sent to the platform or mining ship. Therefore, the study of the flow characteristics of hydrate slurry in vertical pipes is of great significance for hydrate mining. To study the effect of different working conditions on the flow characteristics of hydrate slurry in vertical pipes, the flow characteristics of hydrate slurry in vertical pipes were simulated using the population balance theory based on hydrate particle aggregation dynamics. This paper focuses on the simulation of the flow characteristics of hydrate slurry with different initial particle sizes, concentrations and velocities, and according to the simulation results, the flow characteristics of hydrate slurry such as pressure drop, concentration distribution, and hydrate particle size distribution are analysed. The results of this study can provide referenced for the flow characteristics of hydrate slurry in hydrate mining. [Received: October 6, 2018; Accepted: March 29, 2019]

Experimental Study of the Particulate Dirt Characteristics on Pipe Heat Transfer Surface

The systematic study of the particulate dirt characteristics on heat exchanging surface can provide theoretical guidance for defouling. In this paper, four main compositions of particulate dirt in the treated city sewage (i.e., CaCO3, MgO, CaSO4 and SiO2) are selected as the research objects. The effects of different working conditions, characteristics of particles on the growth rules of particulate dirt and the synergistic fouling by different particles are researched by thermal resistance method experimentally, while the microstructures of the dirt are observed by Scanning Electron Microscope (SEM). The asymptotic values of both dirt thermal resistance and the scaling rate decrease with the increasing of working fluid velocity, while the two asymptotic values increase with the increasing particle size and particle concentration. Although the working fluid import temperature shows a weaker influence on the thermal resistance, but the increase of working fluid import temperature can retard the fouling rate. Among the stable values of the thermal resistances of four types of fouling, SiO2 is the largest and MgO is the smallest. The synergistic fouling by different types of particles results in the denser structure of mixed fouling.

Probabilistic life analysis of vital components considering multistage degradation under variable working conditions

AbstractThe lifespan of a mechanical product is related to its working conditions; the product's performance typically shows a multistage degradation pattern throughout its life profile. The performance degradation is generally researched under constant test conditions, while the effects of different working conditions on life are seldom considered. This paper proposes a staged recursive derivation method for the multistage degradation under variable working conditions. The proposed method works by merging measured degradation data with an empirical degradation model. The measured degradation data of a new prototype are utilized to update the staged degradation model based on a Bayesian posterior probability analysis. The staged degradation model is derived stage by stage, and then the probabilistic life of the new prototype is predicted. The degradation data of a machine‐gun barrel are used as a case study to demonstrate and validate the proposed method. The results show that the probabilistic life of the test prototype can be predicted effectively in the case of relatively little measured degradation data at the product development stage. Furthermore, the proposed method appears to be especially suited to mechanical components requiring short test periods or low test costs.

Fundamental Investigation of EDM Plasmas, Part II: Parametric Analysis of Electric Discharges in Gaseous Dielectric Medium

The parametric investigation presented in this paper provides an analysis of dry electrical discharge machining (DEDM) under different processing conditions by advanced plasma diagnostics. Optical emission spectroscopy interpretation supported by a collisional-radiative model indicates that DEDM discharges performed with point-type cathode electrode are dominated by the anode material, independently of the used electrodes materials and anode electrode geometry. Moreover, plasma diagnostics suggests substantial influence of the adopted electric current, anode electrode geometry and electrode materials in several discharge properties, such as electron density, fraction of accelerated electrons, expansion and composition of the plasma. The achieved results support a better understanding of the effects of different working conditions on the DEDM discharges, necessary for future industrial development of this process.

Multiphysics circuit of a magnetostrictive energy harvesting device

Kinetic energy harvesting devices based on magnetostrictive materials are composed of several parts, for dealing with multiphysics, including mechanical, magnetic, and electric quantities. An effective method to simulate the effects of different working conditions is important to fully exploit such devices. The aim of this paper is to present an equivalent circuit that can be identified with standard measurements on the device and simulated with a standard circuit simulator, such as Spice. The circuit is a nonlinear three-port circuit, related to the mechanical, magnetic, and electrical parts of the device. Unlike many of the published papers on the subject, the magneto-mechanical modeling is quite realistic and exploits nonlinear functions and the full coupling among the involved physical quantities of the employed magnetostrictive material. The nonlinear equivalent circuit is preliminarily validated on a concept device with permanent magnets biasing on a Stress Annealed Galfenol rod. Experimental data with different resistive loads and magnetic biasing are considered and compared with simulation outputs, in terms of the RMS voltage and harvested power.

Whole Body Vibration Exposure During Operation of Rice Combine Harvester under Egyptian Field Conditions

The main target of this investigation is to study the effect of different working conditions during rice harvesting on the combine harvester operators WBV exposure under actual Egyptian field conditions. Data were measured and collected for four types of rice combine harvester and three methods of planting; manual transplanting, mechanical transplanting and direct sowing. Sixteen representative healthy rice combine harvester operators were selected for this study. Parameters of frequency-weighted vibration acceleration in root mean square (RMS), vibration dose value of weighted r.m.s acceleration, (VDV(8)kZ), heart pulses rate (HR), blood pressure (BP), work related body pain (WRBP), stand height and weight of operators were evaluated. Vibration measurements were performed according to (ISO 2631-1: 1997). Field experiments were conducted in a statistically designed layout (completely randomized design) and were conducted at the applied research farm of RiceMechanizationCenter, Meet Eldeba, Kafr El-Sheikh governorate and other farms beside, in the 2016 grown seasons of rice crop. The obtained results indicated that the yanmer combine harvester used for the field planted by manual transplanting at soil moisture content of 20.38 % recorded the highest WBV data of the vibration dose value of weighted r.m.s acceleration, VDV(8)kZ magnitude, while the largest single orthogonal axis is in the axis (Z) which exceeded both of exposure action and exposure limit values. This causes a high risk on the operator body which increases the heart rate and blood pressure, followed by the Daedong combine harvester for the field planted by manual transplanting at soil moisture content of 20.42 %. On the other hand, the WBV parameters recorded the lowest values for Claas combine harvester used in the field planted by direct sowing at soil moisture content of 20.67 %., consequently there is no risk on the operator and also the heart rate and blood pressure. Using rubber spring during rice harvesting by yanmer combine harvester results in a decrement percentages in the WBV values and so heart rate and blood pressure. The maximum WRBP values were obtained during harvesting rice by yanmer combine harvester for the field planted by manual transplanting, followed by harvesting rice by Daedong combine harvester for the field planted by manual transplanting and harvesting rice by Class combine harvester for the field planted by direct sowing the recorded WRBP values were 13.1, 12.4 and 6.6 (Borg scale CR—10 scale.) respectively. Results showed that there are significant differences between the frequency-weighted RMS acceleration, vibration dose value of weighted r.m.s acceleration, VDV(8)kZ, heart rate and blood pressure during studied different farm operations.

Lubricant film flow and depletion characteristics at head/disk storage interface**Project supported by the National Natural Science Foundation of China (Grant No. 51275124).

The characteristics of lubricant film at head/disk interface (HDI) are essential to the stability of hard disk drives. In this study, the theoretical models of the lubricant flow and depletion are deduced based on Navier–Stokes (NS) and continuity equations. The air bearing pressure on the surface of the lubrication film is solved by the modified Reynolds equation based on Fukui and Kaneko (FK) model. Then the lubricant film deformations for a plane slider and double-track slider are obtained. The equation of lubricant film thickness is deduced with the consideration of van der Waals force, the air bearing pressure, the surface tension, and the external stresses. The lubricant depletion under heat source is simulated and the effects of different working conditions including initial thickness, flying height and the speed of the disk on lubricant depletion are discussed. The main factors that cause the lubricant flow and depletion are analyzed and the ways to reduce the film thickness deformation are proposed. The simulation results indicate that the shearing stress is the most important factor that causes the thickness deformation and other terms listed in the equation have little influence. The thickness deformation is dependent on the working parameter, and the thermal condition evaporation is the most important factor.