Maximum Traction Research Articles

Virtual strain loading method for low temperature cohesive failure of asphalt binder

Cohesive failure is one of the primary reasons for low-temperature cracking in asphalt pavements. Understanding the micro-level mechanism is crucial for comprehending cohesive failure behavior. However, previous literature has not fully reported on this aspect. Moreover, there has been insufficient attention given to the correlation between macroscopic and microscopic failures. To address these issues, this study employed molecular dynamics simulation to investigate the low-temperature tensile behavior of asphalt binder. By applying virtual strain, the separation work during asphalt binder tensile failure was calculated. Additionally, a correlation between macroscopic and microscopic tensile behaviors was established. Specifically, a quadrilateral asphalt binder model was generated based on SARA fractions. By applying various combinations of virtual strain loading, the separation work at tensile failure was determined. Furthermore, the impact of strain loading combinations on separation work was analyzed. Normalization was employed to establish the correlation between macroscopic and microscopic tensile behaviors. The results indicated that thermodynamic and classical mechanical indicators validated the reliability of the tetragonal asphalt binder model. The strain loading combination consists of strain rate and loading number. All strain loading combinations exhibited the similar tensile failure characteristic. The critical separation strain was hardly influenced by strain loading combination. However, increasing strain rate significantly enhanced both the maximum traction stress and separation work of the asphalt binder. An increment in the loading number led to a decrease in separation work. The virtual strain combination of 0.5%-80 provided a more accurate representation of the actual asphalt's tensile behavior trend.

Optimization of Swivel Spherical Hinge Structure Design Based on the Response Surface Method

The accurate analysis of key components of a spherical hinge structure directly affects bridge quality and safety during construction. Considering the key components of a spherical joint structure as the research object, a refined calculation model for the spherical joint is established to examine its stress using finite element analysis. The influence of design parameters on the mechanical characteristics of the spherical hinge structure is systematically analyzed. The response surface method (RSM), devised using a Box–Behnken design, is used to optimize the design of the spherical hinge structure parameters. A response surface model is established to derive the scheme of the optimized spherical hinge structure design. Moreover, by comparing the structural contact stress and rotational traction force before and after optimization, the effectiveness and necessity of the spherical hinge structure optimization are verified. The result comparison shows that the maximum contact stress and rotational traction force in the spherical hinge structure after optimization are reduced by 13.86% and 8.42%, respectively, compared with those before optimization. The relative error between the calculated and predicted values is approximately 3%, indicating that the RSM is feasible for optimizing key components of the spherical hinge structure. Its optimization effect is evident. Based on the identified optimal parameters of the spherical hinge structure, a range of recommended design parameters for the key structure of the rotating spherical hinge at different load carrying capacities is established using the interpolation method, which provides a valuable reference for engineering practice.

Design and development of undercarriage systems for agricultural tractors with replaceable half-tracks

The need to use such propulsion devices in mobile agricultural power units is substantiated. The relevance of this development based on global trends is shown. The purpose of the research is to develop the design, to evaluate strain-stress state and functional characteristics of undercarriages of agricultural tractors with replaceable half-tracks. An experimental design of the replaceable tracked undercarriage was developed and manufactured, modeling of loading modes was performed, calculations were carried out by the finite element method of the stress-strain state of structural elements according to 6 load schemes – tractor parking on a flat horizontal surface; movement with maximum traction force; parking across a 30° slope for the upper track; parking across a 30° slope for the lower caterpillar; driving into an obstacle with a deviation of 15°; driving over obstacles based on the central rollers. It was determined that the selected structural material, by the above mentioned loading modes ensure the operability of replaceable tracked undercarriage. Calculations were carried out to check the adequacy of the developed mathematical model using field tests in testing ground of FSAC VIM. It was determined that the maximum stress-strain state of the frame structure of a replaceable tracked undercarriage for all types of loading did not exceed 100 MPa. This provides a two-fold margin of safety in terms of fluidity of the structure, taking into account the characteristics of the selected material. In the maximum loaded state - parking across a slope of 30° - the highest stress on the upper track is 161 MPa, which corresponds to a safety margin of 1.45. The deformation of the bearing assembly was no more than 4 mm, which is allowed by the design of the drive assembly and the caterpillar.

Multiobjective Optimization of Traction Substation Converter Characteristic and Train Timetable in Subway Systems

Currently, power supply accidents and excessive energy consumption occur frequently in DC traction power systems of multitrain subway lines. Rail potential (RP) exceeds the standard limit frequently, energy consumption and fluctuation of the traction current are high, which are directly affected by the traction substation converter characteristic and train timetable. In this paper, multi-objective optimization of traction substation converter characteristic and train timetable is conducted to realize the safe and economic operation of subway systems. Firstly, a power flow calculation platform with multitrain running dynamically is established to work out the operating parameters of the system. Then, a multi-objective optimization model consisting of maximum RP, energy consumption and maximum traction current is designed. For the coordination of multiple goals to be optimized, an enhanced Non-Dominated Sorting Genetic Algorithm-III (NSGA-III) is proposed to obtain an optimal traction substation converter characteristic and train timetable. Finally, the multi-objective optimization is conducted with the data of Guangzhou Metro Line 2. Results indicate that three optimized objectives are dropped by 43.8%, 33.4% and 40.3% respectively based on the proposed optimization method, which will greatly enhance the energy conservation and power supply safety of subway systems.

Failure modes and dynamic responses of roller compacted concrete gravity dams subjected to underwater contact explosion based on the cohesive model

Considering the construction technology of roller compacted concrete (RCC) gravity dams, there are layers in dams inevitably, which may affect the blast responses of dams. This paper is aimed to investigate the effects of RCC layers on the failure modes and dynamic responses of RCC gravity dams bearing underwater contact explosion loading. Initially, the zero-thickness cohesive element model is presented to simulate the crack behavior of the RCC layers. An impact test of a concrete beam is selected to verify its reliability. The concrete damage plasticity model considering strain rate effects is utilized to simulate the various responses of concrete under blast load. The dam–reservoir–foundation interactions are described using the coupled Eulerian-Lagrangian method. The numerical methods are validated by a field blast test of a concrete structure. Subsequently, numerical models were established for gravity dam-reservoir-foundation systems, with and without considering RCC layers respectively. Based on validated algorithms, these models were utilized to explore the effects of RCC layers on the blast performance of the dam. Finally, the influence of the parameters of RCC layers on the nonlinear responses and failure modes of the dam is further investigated, including the maximum traction, the fracture energy, and the layer thickness. The results reveal that the layers significantly change the failure modes. The RCC layers are the weak link of the dam and they will lower the anti-explosion performance of the dam. Therefore, it is crucial to take the layers into account when conducting anti-explosion research, and RCC dams cannot be simply simplified as normal concrete dams. To guarantee the safety of the dam, it is important to ensure the layers with sufficient strength and fracture energy, as well as an appropriate thickness.

An adaptive receding horizon-based flexible mode switching control strategy of parallel hybrid electric vehicles

Mode switching is crucial to efficient drive in variable driving conditions for hybrid electric vehicles (HEVs), thus many scholars are attracted to implement its high-quality control. The receding horizon control method is an attractive method to solve this problem. However, the choice of prediction horizon is arduous due to the contradiction between the optimization performance and the computational cost. Motivated by this issue, this paper proposes an adaptive receding horizon control (RHC) method, which contains optimization layer (OPL) and feedback control layer (FCL). First, an OPL adaptive receding horizon control method is proposed to obtain the optimal control command, in which a novel adaptive factor, considering the proportional between the maximum traction motor torque and powertrain demand torque, is proposed to adjust the prediction horizon length and control constraints. Then, regarding OPL output as the reference trajectory, a lower-RHC method is designed in FCL to track the reference trajectory. Finally, the proposed control method is validated in simulation and bench experiment. Compared with the existing method, the clutch trajectory is optimized by RHC with adaptive prediction horizon and constrains, and the anti-disturbance ability is enhanced by the lower-RHC. The simulation and bench experiment results indicate that the 0–40 km/h acceleration time and jerk are reduced using the proposed method, respectively.

Methodology for Assessing Tractor Traction Properties with Instability of Coupling Weight

The purpose of the study is to increase the efficiency of using the tractor hitch weight in traction mode by reducing the uneven distribution of vertical reactions between the wheels. This work is grounded on a methodology that involves summarizing and analyzing established scientific findings related to the theory of tractors operating in traction mode. The analytical method and comparative analysis were employed to establish a scientific problem, define research objectives, and achieve the goal. The key principles of probability theory were applied in developing the empirical models of the tractor. The main provisions of the methodology for evaluating the traction properties of the tractor with the instability of the coupling weight were formulated. The method of evaluating the vertical reactions on the wheels of the tractor is substantiated, which is based on the measurement of the vertical reaction on one of the four wheels. It was proven that tractors with a center of mass offset to the front or rear axles have the greatest probability of equal distribution of vertical reactions between the wheels of one axle, and tractors with a center of mass in the middle between the axles have the lowest probability. It is theoretically substantiated and experimentally confirmed that when the tractor performs plowing work with uneven distribution of loads on the sides, its operation with maximum traction efficiency is ensured by blocking the front and rear axle drivers.

Simulation Research on the Grouser Effect of a Reconfigurable Wheel-Crawler Integrated Walking Mechanism Based on the Surface Response Method

To improve the unstructured terrain traversing performance of the scientific research robot of the Qinghai–Tibet Plateau station, the parameters of the track shoe of the reconfigurable wheel-crawler walking mechanism were studied. Based on a typical track shoe puncture effect model, the experimental design was carried out based on the surface response method, and the dynamic model of the triangular crawler mode of the reconfigurable wheel-crawler walking mechanism was constructed and tested using RecurDyn V9R3 software. Through an analysis of the simulation results, the interaction of the grouser parameters was further clarified, and the regression equation of the traction force of the walking mechanism was obtained. The grouser parameters that enabled the reconfigurable wheel-crawler walking mechanism to have the maximum traction were obtained; these will be used to guide the machining of the prototype walking mechanism.

On the Control of Traction Characteristics and Resistance to Movement of Mobile Robots with Walking Propulsion Devices

The problem of increasing the traction and dynamic properties of mobile robots with walking propulsion devices is considered. The interdependence of the traction forces developed by the propulsion devices and the forces of resistance to the movement of robots, due to their interaction with the environment, is analyzed. A mathematical model is proposed based on the quasi-static nature of the robot’s movement and taking into account the static uncertainty of the problem. Static indeterminacy is due to the presence of propulsion devices on each of the sides and interacting with the supporting surface in the amount of more than two. A feature of the solution is also taking into account the gait and schedule of the robot’s movement, which characterize the time sequence of the propulsion devices being in the phase of interaction with the supporting surface and in the phase of transfer to a new position. The gait is also characterized by the mode coefficient, which is the ratio of the time the propulsion device is in the stance phase to the total time of the cycle of its movement. An optimality criterion is introduced on the basis of which the design perfection of the propulsion devices and the place of their installation on the robot is evaluated. The optimality criterion consists of two indicators: the value of the maximum traction force and the average force of resistance to movement. The tractive force is assumed to be proportional to the sum of the maximum normal loads acting on each propulsion device unit, and the resistance force to the squares of the same loads. Simulation modeling has been carried out, proving the dependence of the magnitude of traction properties and the forces of resistance to movement on the location of the propulsion devices. Two systems of vertical arrangement of the points of suspension of propulsion devices were compared. It has been established that a sufficiently small change in the vertical coordinate of the suspension point of even one propulsion devices has a noticeable change in the maximum traction forces and movement resistance forces. It is concluded that by adjusting the vertical position of the propulsion devices foot relative to the robot body, it is possible to control the traction properties and movement resistance, as well as the importance of the positioning accuracy of the foot of the propulsion devices walking mechanism during movement.

Sutureless Technique for Surgical Castration in Adult Boars: A Feasibility Study.

The heterogeneity of Italian manufacturing processes results in the production of a large variety of pork products. In Sardinia, boars are raised and butchered to produce charcuterie. These animals are castrated before slaughter as androstenone would otherwise taint the meat, rendering it unfit for human consumption. However, to date, the literature concerning surgical orchiectomy in adult boars is limited. The goal of this study is to assess whether a sutureless swine orchiectomy procedure is feasible. Additionally, this study aims to determine the appropriate traction force needed to tie knots in the deferens duct of pigs of different weights and ages. Two groups were created: the first (n = 91) underwent orchiectomy by suture ligation; the second (n = 20) was castrated using the sutureless technique. Deferens ducts of animals in the first group (n = 182) were collected following castration, and their tensile strength was measured. Pearson's linear correlation was used to determine the relationship between the maximum traction force and weight and age groups. A correlation of 0.99 and 0.96 was shown between traction force and age and traction force and weight, respectively. In accordance with these results, sutureless castration was performed on 20 animals, calibrating the pulling force needed according to the age and weight of the boars. No complications were observed during the feasibility study, thus validating sutureless orchiectomy in adult boars.

PATELLAR FRACTURE IN ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION: IN VITRO ANALYSIS.

To determine, by biomechanical analysis, safe patellar cut limits in anterior cruciate ligament (ACL) reconstruction that minimize fracture risks. From three-dimensional reconstruction, triangular cuts were made in the patella, with a depth of 6.5 mm and variable width and length (10 to 20 mm and 8 to 12 mm, respectively, both with an interval of 1 mm). The combinations of cuts constituted 55 models for tests, with five variations in width and 11 variations in length, tested with the finite element method (FEM). The mean of the localized principal maximum (traction force) values was 4.36 Pa (SD 0.87 ± 0.76) and the localized principal minimum (compression force) was -4.33 Pa (SD 1.05 ± 1.11). Comparing width and length to the tension force of the values of the main maximum, we found statistical significance from 11 mm for width and 13 mm for length. In ACL reconstruction, the removal of the patellar bone fragment is safe for fragments smaller than 11 mm in width and 13 mm in length, which corresponds to 24% of the width and 28% of the length of the patella used. Level of Evidence II, Comparative Prospective Study.

Desempenho do trator agrícola com diferentes distribuições de massa entre eixos

ABSTRACT: An adjustment of the agricultural tractor is necessary to achieve energy efficiency, which can be done through the correct distribution of mass between the axles for each operating surface. This research evaluated different distributions of mass between axles in a 93 kW tractor equipped with auxiliary front-wheel drive, on two soil surfaces. The experiment was carried out in strip design, with a double factorial scheme (2 x 3), with two soil surfaces (mobilized and firm) and three mass distributions between axes (35/65%, 40/60% and 45/55%), with five repetitions, totaling 30 parcels. The slippage parameters of the front and rear wheelset, engine rotation, hourly and specific fuel consumption, force, power and yield on the drawbar, displacement speed, engine thermal efficiency, traction coefficient, rolling resistance, and yield in traction. On firm soil, the energy performance of the tractor was superior in relation to the mobilized one, which allowed greater tractor and drawbar performance with lower specific fuel consumption. The use of a 35/65% between-axle mass distribution provided maximum traction for the mechanized set, resulting from the reduction in energy expenditure generated by skating and; consequently, the maximum use of the energy made available by the mechanized set. However, the maximum conversion of energy contained in the working fuel is obtained with the 45/55% setting.

МЕТОДОЛОГІЯ ОЦІНЮВАННЯ ТЯГОВИХ ВЛАСТИВОСТЕЙ ТРАКТОРА ЗА НЕСТАБІЛЬНОЇ ЗЧІПНОЇ ВАГИ

Abstract Purpose of the study. The purpose of the study is to increase the efficiency of using the tractor hitch weight in traction mode by reducing the uneven distribution of vertical reactions between the wheels. Research methods. The methodological basis of the work is the generalization and analysis of known scientific results regarding the theory of the tractor in traction mode. Analytical method and comparative analysis were used to form a scientific problem, determine the goal and set research objectives. When creating empirical models of the tractor, the main provisions of the theory of probabilities were used. The results of the study. The main provisions of the methodology for evaluating the traction properties of the tractor with the instability of the coupling weight have been formulated. The method of evaluating the vertical reactions on the wheels of the tractor is substantiated, which is based on the measurement of the vertical reaction on one of the four wheels. It has been proven that tractors with lubrication to the front or rear axles of the center of mass have the greatest probability of equal distribution of vertical reactions between the wheels of the same axle, while tractors with the center of mass in the middle between the axles have the lowest probability. It is theoretically substantiated and experimentally confirmed that when the tractor performs plowing work with uneven distribution of loads on the sides, its operation with maximum traction efficiency is ensured by blocking the front and rear axle drivers. Conclusion. A well-founded methodology for evaluating the influence of the position of the tractor’s center of mass on its traction properties. The issue of evaluating the influence of the tractor’s center of mass on its traction properties when aggregated with mounted, trailed and combined agricultural machines remains open. Key words: tractor, traction properties, coupling weight, center of mass, vertical reactions, driving bridges, blocking.

Rigid-hyperelastic Coupling Dynamic Model and Dynamic Characteristics of Spring type of Traction Robot

The traditional anchoring mechanism of the traction robot is rigid, which is easy to be stuck in the wellbore. In order to solve the problem produced by the rigid anchoring mechanism of the traction robot, a novel anchoring mechanism was proposed based on the spring type of anchoring mechanism of the inclined block. The key to make the traction robot motion is whether the traction robot can be anchored on the wellbore under the action of the traction force. Therefore, a rigid-hyperelastic coupling dynamic model of the spring type of anchoring mechanism under the action of the traction force was established. On the basis, the effects of span, width, thickness and chamfer parameters on the anchoring performance of the spring type of traction robot were analyzed. Through the experimental comparison, it was found that the error between the theoretical supporting force and the experimental supporting force is only 6.1%, and the maximum error of theoretical and experimental maximum traction force is 4.9%. Experiments verified the correctness of the rigid-hyperelastic coupling dynamic model. The research results of this paper lay a foundation for the structural design and engineering application of spring type of traction robot. It can effectively ensure the downhole safety of oil and gas wells.

Simulation and experimental research of electric tractor drive system based on Modelica

The electric tractor has the advantages of zero-emission, high efficiency, and low noise, which is the direction of future development and transformation of agricultural power machinery. Aim at the problem that the simulation methods commonly used in the development of electric tractor drive system are poorly generalized and cannot meet the simulation needs of complex multi-domain physical systems. This paper proposes a modeling method for an electric tractor drive system, takes the YTO-500 tractor as the research object, designs and calculates the overall scheme and parameters of its drive system, divides the drive system into modules, establishes the energy system, motor system and mechanical parts model based on Modelica, and integrates the simulation model of electric tractor drive system on this basis. The traction performance and transportation working conditions were simulated and tested. With compared and analyzed, in the traction characteristics, the simulation and test results of maximum speed, maximum traction force, and maximum traction power of each gear are consistent; within 400s transportation simulation conditions, the speed range of electric tractor is 13~28km·h-1, which is consistent with the speed range of electric tractor transportation gear. The results show that the simulation and the test results are consistent, which verifies the credibility of the simulation and the correctness of the model built, providing a basis for future research and development of agricultural machinery.

A new knee arthrometer demonstrated to be reliable and accurate to assess anterior tibial translation in comparison with stress radiographs

IntroductionFor several years, many arthrometers have been developed to assess anterior knee laxity. The aim of our study was to evaluate the validity of a new practical and handy testing device with the hypothesis that the new arthrometer had good validity in terms of reliability and accuracy.MethodsLachman test was performed on five fresh frozen cadaveric knees by five examiners. Anterior tibial translation (ATT) was measured with a new arthrometer (BLU-DAT) and on lateral stress radiographs. Data on ATT were obtained under 7 kg (69 N), 9 kg (88 N), and maximum manual traction (MMT). Tests were performed on the same specimens before and after arthroscopic ACL excision. Inter-rater reliability of the BLU-DAT measures was assessed with the intraclass correlation coefficient (ICC) for single and average measurements. The Bland–Altman method was used to estimate agreement between the BLU-DAT and stress radiographs.ResultsICC values for single measurements were 0.62, 0.54 and 0.58 for 7-kg, 9-kg and MMT assessment, respectively. Overall reliability was good (ICC = 0.63). ICC values for average measurements were 0.89, 0.85 and 0.88 for 7-kg, 9-kg and MMT assessment, respectively. Overall reliability was very good (ICC = 0.90) SEM ranged from 1.4 mm to 1.6 mm for single measurements and was below 1 mm at each testing condition for average measurements. Analysis of agreement between BLU-DAT and radiographic measurements showed a mean difference equal to 0.83 mm ± 2.1 mm (95% CI: 0.55–1.11). Upper LOA was equal to 4.9 mm (95% CI: 5.39–4.41). Lower LOA was equal to − 3.2 mm (95% CI: − 2.71 to − 3.69).ConclusionMeasurement of anterior knee laxity with the BLU-DAT testing device has a good to very good inter-rater reliability and good agreement with a gold standard such as stress radiographs.Cadaveric Diagnostic Study, Level of Evidence IV.

Postless Hip Distraction Systems Decrease the Amount of Traction Force Needed to Obtain Adequate Hip Distraction Versus a Conventional Post Hip Distractor

To directly compare hip distraction distance and traction force data for hip arthroscopy performed using a post-basedsystem versus a postless system. Adult patients undergoing primary hip arthroscopy for femoroacetabular impingement were prospectively enrolled. Before March 26, 2019, arthroscopy was performed using a post-based system. After this date, the senior author converted to using a postless system. Intraoperative traction force and fluoroscopic distraction distance were measured to calculate hip stiffness coefficients at holding traction (k-hold) and maximal traction (k-max). We used multivariable regression analysis to determine whether postless arthroscopy was predictive of lower stiffness coefficients when controlling for other relevant patient-specific factors. Hip arthroscopy was performed with a post-based system in 105 patients and with a postless system in 51. Mean holding traction force (67.5 ± 14.0 kilograms-force [kgf] vs 55.8 ± 15.3 kgf) and mean maximum traction force (96.0 ± 16.6 kgf vs 69.9 ± 14.1 kgf) were significantly lower in the postless group. On multivariable analysis, postless traction was an independentpredictor of decreased k-hold (β= -31.4; 95% confidence interval, -61.2 to -1.6) and decreased k-max (β= -90.4; 95% confidence interval, -127.8 to -53.1). Male sex, Beighton score of 0, and poor hamstring flexibility were also predictors of increased k-hold and k-max in the multivariable model. Postless traction systems decrease the amount of traction force required for adequate hip distraction for both maximal and holding traction forces when compared with post-based systems. Postless traction systems may help further reduce distraction-type neurologic injuries and pain after hip arthroscopy by lowering the traction force required to safely distract the hip. Level III, prospective cohort-historical control comparative study.

Оптимізація методики хірургічної корекції прихованого статевого члена в дітей

The purpose - to optimize the buried penis surgical treatment method in children for the most adequate functional and cosmetic results. Materials and methods. The clinical material includes 28 boys with a buried penis between the ages of 11 months to 7 years. Among them 9 (32.14%) children were admitted for repeated surgical interventions with unsatisfactory cosmetic results after previous surgical interventions in other medical institutions. Results. The method of surgical correction of the buried penis in children was offered. In patients whose penis glans could not be exposed, the foreskin stenotic ring was dissected on both sides on the lateral surfaces, or scar-altered tissues were partially excised circularly. During the maximum vertical traction per the ligature on the penis head, the skin at the base of the penis was circularly dissected. The dissection of the skin was extended to the inguinal folds on both sides. The penis spongy and cavernous bodies were skeletonized from the coronal sulcus to the pubic joint with careful excision of inelastic embryonic cords and scars. The skin of the anterior abdominal wall was lifted up with the help of traction ligatures or hooks and mobilized in an acute way. Maximum excision of subcutaneous fat in the suprapubic and inguinal areas was performed. The penis was moved into the hole formed in the lower part of the demobilized skin flap in the suprapubic area. For stable fixation of the penis, the deep fascia at the base of the corpora cavernosa was sutured to the pubic tubercle at maximum traction per the head, and the skin flap of the anterior abdominal wall was sutured with internal sutures to the crest of the upper pubic bone. The penis trunk was closed due to a sufficiently mobile foreskin, shifting the skin to the penoscrotal angle in the area of the formed hole in the abdomen skin flap. The postoperative wound was sutured in layers. Conclusions. Clinical differentiation of different types for penis size «visual» reduction in boys will allow a balanced approach to adequate correction of the defect. The proposed method of buried penis surgical correction in boys eliminates all the preconditions of the defect and demonstrates good anatomical, functional and cosmetic results. The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the local ethics committee of the listed institution. Informed consent of children and their parents was obtained for the research. No conflict of interests was declared by the authors.

Investigation of subsurface microcracks causing premature failure in wind turbine gearbox bearings

One of the reasons behind the low rate of expansion of power production driven by wind turbines is the premature failure of their gearbox bearings, which fail within the first quarter of their designed life. The leading causes of fatigue damage in wind turbine gearbox bearings (WTGBs) are not well recognized despite the massive studies in this field. The damage initiates as subsurface microcracks, propagating to a macro scale and reaching the contact surface. For that, studying the microcracks in the early initiation stage (1–15 μm) significantly impacts the bearing damage trigger. This study is based on evaluating the role of non-metallic inclusions and voids on crack initiation, revealing the varying parts of (maximum shear stress, Von-Mises stress, and traction force) in crack initiation. The results indicated that the effect of inclusion is relatively limited on cracking initiation regardless of their sizes, other than voids, which probably have a considerable role in crack initiation and propagation. The three factors (Von-Mises stress, maximum shear stress, and traction force) played significant roles in the initiation of cracks. However, there is an urgent need to improve the design and manufacturing of WTGBs to decrease the formation of voids and carbides and revise the design standards for both (bearing life and contact stress) to consider the actual relative effects of the severe operating events.

Analysis of wheel pairs slip control of electric freight locomotive with asynchronous traction motors

Introduction. Every year, the amount of electric rolling stock with asynchronous traction motors is continuously increasing on the Russian railway network, since such traction drives have a number of advantages over drives with DC motors. One of the problems associated with the introduction of asynchronous motors and an increase in the mass of trains is the implementation of the maximum traction force by an electric locomotive at the threshold in terms of wheel – rail adhesion. Timely recognition of excessive slip of wheel pairs is the most important indicator of the efficiency of the traction drive in realising the maximum traction properties of the electric locomotive at all axles.Materials and methods. The article reflects the results of the study of slip of electric locomotive wheel pairs with asynchronous traction motors and axial control of the traction force, obtained during experimental runs on a railway section under various adhesion conditions. The article presents a technique for studying the wheel pair adhesion failure of electric locomotives with asynchronous traction motors.Results. During the comparison of the obtained experimental results with the calculated parameters by the O. Polach mathematical model, an updated range of the relative slip of wheel pairs is given, in which the electric locomotive control system could realise the maximum tractive effort. Exceeding this range will lead to increased wear of wheel pairs without increasing traction properties.Discussion and conclusion. It is advisable to use the results of the study in the future when developing systems for controlling the tractive effort at the limit of adhesion and systems for controlling the slip of wheel pairs of electric freight locomotives with asynchronous traction motors.