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1
Volianiuk, Vladimir, Dmitry Mishchuk e Eugene Gorbatyuk. "Determination of inertial loads of the rota-ry boom of a self-propelled crane". Gіrnichі, budіvelnі, dorozhnі ta melіorativnі mashini, n. 96 (31 dicembre 2020): 13–21. http://dx.doi.org/10.32347/gbdmm2020.96.0201.
Testo completoAbstract (sommario):
Self-propelled jib cranes are most widely used in construction for loading and unloading operations, the main advantage of which, among other types of cranes, is high mobility. The share of self-propelled jib cranes in construction is more than 60%.
An important element of the construction of self-propelled jib cranes is the boom, the strength of the structure of which largely depends on the safety of the crane and the prevention of accidents that lead to injuries and death of maintenance personnel. When calculating the crane boom for strength, power of electric motors for changing the departure of the boom and turn, the brakes of these mechanisms must take into account all types of loads acting on the rotary boom with load, including inertial, which account for a significant share among other loads.
The paper considers the calculation of the following moments of inertia forces: created by vertical inertial forces during braking of the load lifting mechanism; arising from the mass of the load and the boom during the period of unstable movement of the mechanism of change of the boom departure during start-up and braking; the load created by centrifugal force which arises at rotation of a rotary part of the crane; arising from the mass of the load and the boom during the period of unstable movement of the crane rotation mechanism. When calculating these moments of inertia, the following initial data are taken into account: geometric dimensions of the crane, weight and length of the boom, weight and height of the load, angle of the self-propelled crane in the construction area, radius of the crane boom, boom and load speeds, start and braking times mechanisms for lifting the load, changing the departure of the boom and turning the crane.
The obtained dependences for determining the inertial loads of the rotary boom of a self-propelled crane will allow more accurately taking into account multiple factors to calculate the values of these loads in order to perform strength calculations of the boom, selection of components for lifting, changing the boom and turning the crane.
2
Niu, Congmin, e Huajiang Ouyang. "Nonlinear Dynamic Analysis of Lifting Mechanism of an Electric Overhead Crane during Emergency Braking". Applied Sciences 10, n. 23 (24 novembre 2020): 8334. http://dx.doi.org/10.3390/app10238334.
Testo completoAbstract (sommario):
Mechanical brakes are essential for electric cranes when emergency braking occurs. This paper presents, for the first-time, a dynamic response analysis of emergency braking events of electrical cranes that has modelled crane components as flexible and rigid bodies. Based on the Hamilton principle, a nonlinear and non-smooth dynamic model is derived from a modified Lagrangian function and the virtual work of non-conservative forces. The dynamic responses of a 32-ton overhead travelling crane during the emergency braking process of its lifting mechanism with two service brakes determined by simulating realistic operations. The numerical results show that the loads acting on components of the crane during the braking process depend on the braking capacity and the action time of the mechanical brakes, as well as the magnitude and the initial position of the payload. When a dual-brake scheme of the lifting mechanism is adopted, the maximum load of the high-speed links and the maximum thermal power of the mechanical brake appear in the emergency braking process when one of the two brakes fails to work. In addition, it is found to be a false belief that the lower the initial speed, the lower the maximum loads acting on components of cranes become during the braking process.
3
Xiao, Yelong, Pingping Yao, Haibin Zhou, Zhongyi Zhang, Taimin Gong, Lin Zhao e Minwen Deng. "Investigation on Speed-Load Sensitivity to Tribological Properties of Copper Metal Matrix Composites for Braking Application". Metals 10, n. 7 (4 luglio 2020): 889. http://dx.doi.org/10.3390/met10070889.
Testo completoAbstract (sommario):
A sensitivity analysis of braking speed and normal load on tribological properties of copper metal matrix composites (Cu-MMCs) was investigated using a subscale dynamometer. The morphologies of the worn surface and subsurface were observed by a scanning electron microscope and 3D video microscope. The results indicated that temperatures on the Cu-MMC surface increased with increasing the braking speed and normal load. The average coefficient of friction gradually decreased as the braking speed or normal load increased, and a slight decrease in the wear rate with increasing the braking speed up to 17 m/s after which a clear increasing trend was observed. As the normal load increased from 612 N to 1836 N, the wear rate decreased firstly and then promptly decreased. The transition in wear mechanism of Cu-MMC significantly depended on braking speed and normal load.
4
Wu, Meng Ling, Xiang Jun Zhang, Chun Tian e Ying Xi. "Design and Optimization of Rotating Mechanism for Wind Load Test-Bed of Aerodynamic Brake". Advanced Materials Research 482-484 (febbraio 2012): 1851–59. http://dx.doi.org/10.4028/www.scientific.net/amr.482-484.1851.
Testo completoAbstract (sommario):
To adjust the angle between braking panel of aerodynamic brake and the wind direction, the duct and the direction of the wind are fixed, and the panel is rotated horizontally. So a rotating mechanism should be designed out to make the aerodynamic braking equipment rotate horizontally. This paper emphatically completes the design of rotating control system. The rotating direction is controlled by two bevel gears; magnetic powder clutch is used to simplify the organization, optimize the control mechanism, and let electric signal control the movement of clutch directly; the rotary supporting mechanism is consist of slewing bear which have two functions, supporting and rotating, and this mechanism is more compact and stable. In a word, this mechanism realizes horizontal rotating of the test-bed. And it lays the foundation of experiments about aerodynamic braking system.
5
Hu, Jing Bo, Hui Zou, Yue Gui Feng, Hui Jin e Xiao Ling Wu. "Simulation Calculation of the Braking Performance of Portal Cranes Based on ADAMS". Advanced Materials Research 690-693 (maggio 2013): 2762–66. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.2762.
Testo completoAbstract (sommario):
The braking performance of open-air crane is essential to safety. Taking 40t Portal crane as the study object, this paper first analyzed and calculated the braking torque of traveling mechanism according to the design rules for cranes. Then the portal crane traveling mechanism model was established by the use of simulation software ADAMS, the braking process of crane of constant wind load was studied on typical operation conditions, and its braking performances were comparative analyzed. Finally, it can be concluded that it will substantially increase the crane braking time and braking distance after braking torque is adjusted small and cause hidden troubles of accident. The analytical method and conclusions of this paper can provide a theoretical basis to crane safety management.
6
Zhang, S., Q. Hao, Y. Liu, L. Jin, F. Ma, Z. Sha e D. Yang. "Simulation Study on Friction and Wear Law of Brake Pad in High-Power Disc Brake". Mathematical Problems in Engineering 2019 (14 luglio 2019): 1–15. http://dx.doi.org/10.1155/2019/6250694.
Testo completoAbstract (sommario):
For the serious and uneven wear of the brake pad in the high-power disc brake during braking, the dynamic variation of the brake disc and the brake pad interface variable is considered, the wear calculation model is established based on the friction and wear mechanism, and the wear depth and volume of the brake pad can be calculated by equations. A finite element model of the brake disc and the brake pad is established by DEFORM software which can analyze wear of the brake pad directly. The variation trend of wear during braking is studied, and influences of braking load and initial braking speed on the wear are analyzed. The results show that the amount of the wear increases rapidly in the early wear stage of braking, and it becomes slow in the later stage; the wear of the brake pad is serious at the friction inlet and outlet, and the middle area of the brake pad is lightly worn; heavy braking load and high initial braking speed can exacerbate the wear of the brake pad.
7
POPOV, I. P. "MULTI–INERT OSCILLATORY MECHANISM". Fundamental and Applied Problems of Engineering and Technology 2 (2020): 19–25. http://dx.doi.org/10.33979/2073-7408-2020-340-2-19-25.
Testo completoAbstract (sommario):
A mechanical oscillatory system with homogeneous elements, namely, with n massive loads (multi– inert oscillator), is considered. The possibility of the appearance of free harmonic oscillations of loads in such a system is shown. Unlike the classical spring pendulum, the oscillations of which are due to the mutual conversion of the kinetic energy of the load into the potential energy of the spring, in a multi–inert oscillator, the oscillations are due to the mutual conversion of only the kinetic energies of the goods. In this case, the acceleration of some loads occurs due to the braking of others. A feature of the multi–inert oscillator is that its free oscillation frequency is not fixed and is determined mainly by the initial conditions. This feature can be very useful for technical applications, for example, for self–neutralization of mechanical reactive (inertial) power in oscillatory systems.
8
Ji, Zhanling, Yunhua Li, Rui Xi e Juntao Jia. "Elastic-plastic analysis for wet multidisc brake during repeated braking". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 230, n. 17 (9 agosto 2016): 2968–81. http://dx.doi.org/10.1177/0954406215605334.
Testo completoAbstract (sommario):
To reveal the mechanism and evolution laws of the braking performance declining from heat load in the repeated braking applied for wet multidisc brake, a finite element analysis was carried out by using the bidirectional thermal-structure coupling method. Based on the fundamental principles of the energy conservation and virtual work principle, the elemental equations between temperature and heat load, and deformation displacement and load with heat transferring boundary conditions and heat–structure interaction were derived. Taking a steel disk in the brake for example, the deformation state of its elements, and the starting time, the location, the severity, and evolution laws of the plastic deformation were analyzed and demonstrated by using dimensionless stress distribution contours. The area in contact along the interface and the ratio of the element numbers to produce plastic deformation to the total element numbers on the steel disk were described by contact ratio and plasticity ratio, respectively. Moreover, the results under the repeated braking case were compared with that under the lasting braking case, which indicates that the influence of the temperature load on the performance declining of the repeated braking case is much lower than one of the lasting braking case, and the temperature is lower than 40 K and the plasticity ratio is smaller than 0.35 after the braking time is longer than 350 s. The conducted finite element analyses provided the theoretical fundamentals for the design and the application of the brake in the heavy type of trucks.
9
Xing, Zhichao, Guoye Wang, Zhangpeng Gong, Shudong Zhang, Dongxin Xu e Sijie Peng. "Double-Drum Test Bench for Variable Load Transfer Simulation by Electromechanical Inertia Compensation". Sensors 19, n. 19 (6 ottobre 2019): 4322. http://dx.doi.org/10.3390/s19194322.
Testo completoAbstract (sommario):
To improve the accuracy and actual road equivalence of vehicle performance testing using test benches, a double-drum test bench that meets the test requirements of vehicle control system prototypes and in-use vehicles was designed. Dynamic models of the single-wheel test bench and the vehicle test bench were established, and mechanisms were theoretically analyzed for single-wheel variable adhesion and vehicle load transfer for equivalent testing using the variable placement angle. The mechanism of electromechanical inertia compensation was studied to realize stepless simulation of vehicle inertia and simulate dynamic load while braking. The simulation model of the vehicle test bench system was established based on MATLAB/Simulink. Simulations were carried out to verify the anti-lock braking system (ABS) performance test functionality of the test bench under high adhesion, bisectional, and low adhesion conditions. Referring to the simulation conditions, ABS tests under actual test bench and road conditions were carried out. Results demonstrated that the mechanism of variable load transfer simulation by electromechanical inertia compensation improves the equivalent accuracy compared to that of its road test equivalent, verifying the feasibility of the simulation mechanism. This study could help further improve the accuracy and reduce the cost of vehicle performance testing, thus greatly benefitting the vehicle development and testing industry.
10
Sha, Zhihua, Qiang Hao, Jian Yin, Fujian Ma, Yu Liu e Shengfang Zhang. "Wear calculation and life prediction model of disc brake based on elastoplastic contact mechanics". Advances in Mechanical Engineering 14, n. 4 (aprile 2022): 168781322210931. http://dx.doi.org/10.1177/16878132221093136.
Testo completoAbstract (sommario):
For the friction and wear of the braking surface of the disc brake, the mechanism of friction contact deformation of rough surface is analyzed. Considering elastoplastic contact mechanics of the friction surfaces, combined with Archard wear calculation theory, a wear calculation model of fractal rough surface is established, and a wear life prediction of the brake disc is proposed. Based on high-speed and heavy-load braking conditions, the influence of different braking parameters on the surface wear of brake disc is studied. Moreover, a pin-on-disc wear test is used to verify the validity of the wear calculation model, and the average relative error of test and simulation is 4.97%. The research results show that the fractal parameters affect the complexity of the rough surface, and surface wear is mainly caused by interface plastic contact. The friction coefficient is large, which can strengthen the surface shear effect. Large load and high speed would increase the real contact area of the surface and increase the wear volume per unit time. Furthermore, the wear life of the brake disc could be estimated, which is of great significance for raising the wear life of the brake disc, improving braking life and braking efficiency.
11
Gao, Li Qiang, Ying Xi, Qiang Fu, Mei Hua Zhu e Jin Sen Zhang. "Performance Analysis of a New Type of Wind Resistance Brake Mechanism Based on FLUENT and ANSYS". Advanced Materials Research 562-564 (agosto 2012): 1099–102. http://dx.doi.org/10.4028/www.scientific.net/amr.562-564.1099.
Testo completoAbstract (sommario):
Introduce a new type of non-adhesion braking mode - aerodynamic braking; Meanwhile we analyze the structure of the wind resistance brake mechanism. Based on commercial software Fluent, numeric simulation are applied to the flow field of high speed train with wind resistance brake mechanism in order to work out the pressure distribution law of wing plate and high speed train as well as wind resistance. Based on finite element theory, finite element model of wind resistance brake mechanism is built by ANSYS. Then we make static load analysis and modal analysis to the wind resistance brake mechanism. From the computation and analysis above we get some good conclusions.
12
Houpert, L. "Piezoviscous-Rigid Rolling and Sliding Traction Forces, Application: The Rolling Element–Cage Pocket Contact". Journal of Tribology 109, n. 2 (1 aprile 1987): 363–70. http://dx.doi.org/10.1115/1.3261367.
Testo completoAbstract (sommario):
Piezoviscous Rigid (PVR) film thicknesses, rolling and sliding traction forces formulas for the line and point contact case have been derived. They have been used to study the Rolling Element (R.E.)–cage pocket contact mechanism. As the R.E. gets closer to the cage web, the lubrication regime change gradually from the PVR regime to Piezoviscous Elastic (PVE or EHD) regime when steel cages are used. If plastic cages are used, the lubrication regime moves from the Isoviscous Elastic (IVE) regime to EHD regime. For the conditions simulated herein, the transition occurs at typical film thickness values of the order of 0.5 micrometers and substantially large loads can be calculated in the R.E.–steel cage contact. They can be of the order of 100 N at the transition. In many circumstances, the PVR regime prevails and the braking moment due to hydrodynamic traction in the contact can be easily calculated. A tight osculation between the R.E. and the cage pocket will increase significantly the load and braking moment on the R.E. Starvation effects are also estimated and cause a reduction of the load, but not of the braking moment.
13
Timofeev, G. A., V. V. Panyukhin, V. V. Samoilova e E. S. Novikov. "Research of the Cylindrical Self-Braking Gears Effect on the Drive Operation in Various Modes". Proceedings of Higher Educational Institutions. Маchine Building, n. 5 (746) (maggio 2022): 27–34. http://dx.doi.org/10.18698/0536-1044-2022-5-27-34.
Testo completoAbstract (sommario):
Many electromechanical drives require the fixation of the output link in a given position and the prevention of its spontaneous movement under load. To ensure this, the drive is usually equipped with a brake. However, in many cases it is possible to do without a special braking mechanism if a self-braking mechanism (gear) is included in the drive, which combines the functions of transferring motion and automatic braking the drive after the engine is turned off. This solution allows obtaining a simple and compact structure and reducing the cost of the drive by eliminating the brake. Dynamic models of an electromechanical drive with a power unit consisting of an electric motor and a gearbox, that is a cylindrical self-braking gear are considered. The equations of motion of the main system elements are given, which make it possible to assess the frequency and transient characteristics of the drive, the ability of its operation in various modes.
14
Wang, Dagang, Ruixin Wang, Tong Heng, Guozheng Xie e Dekun Zhang. "Tribo-Brake Characteristics between Brake Disc and Brake Shoe during Emergency Braking of Deep Coal Mine Hoist with the High Speed and Heavy Load". Energies 13, n. 19 (30 settembre 2020): 5094. http://dx.doi.org/10.3390/en13195094.
Testo completoAbstract (sommario):
The friction wear and thermal fatigue cracking of the brake shoe and friction-induced self-excited vibration (frictional flutter) of the disc brake can easily occur during emergency braking of a deep coal mine hoist with at high speed and with a heavy load. Therefore, tribo-brake characteristics between the brake disc and brake shoe during emergency braking of a deep coal mine hoist are investigated in the present study. Scaled parameters of the disc brake of a deep coal mine hoist are determined by employing the similarity principle. Friction tests between friction disc and brake shoe are carried out to obtain the coefficient of friction in the case of high speed and large specific pressure between the friction disc and brake shoe. Coupled thermo-mechanical finite element analyses of the brake disc and brake shoe are established to investigate temperature and stress fields of the brake disc and brake shoe during emergency braking, which is validated by the engineering failure case. Effects of braking parameters on flutter characteristics between the brake disc and brake shoe are explored by employing a double-degrees-of-freedom vibration mechanism model. The results show that the maximum temperature, equivalent Von Mises stress and contact pressure are all located at the average friction radii of contact surfaces of the brake disc and brake shoe during emergency braking. The cage crashing accident in the case of high speed and heavy load in a typical coal mine shows crack marks and discontinuous burn marks at central locations of brake shoe and brake disc surfaces, respectively, which indicates frictional flutter characteristics between brake disc and brake shoe. During emergency braking, flutter time duration decreases with increasing initial braking speed and damping parameter; the flutter amplitude and frequency of the disc brake increases with increasing normal braking load and stiffness, respectively.
15
Singh, Arjun, e R. Deivanathan. "Design and Analysis of a Glass Fibre Trolley". Applied Mechanics and Materials 852 (settembre 2016): 525–30. http://dx.doi.org/10.4028/www.scientific.net/amm.852.525.
Testo completoAbstract (sommario):
This project is based on design and analysis of a glass fibre trolley, for carrying engineering components, other materials at an engine manufacturing plant. Currently AISI 1020 mild steel trolleys are used for moving the goods around the stores or assembly area. These are simple in design but hefty, with four rollers but no braking mechanism. Use of glass fiber as a trolley material is advisable. Stress analysis has been performed for a typical load. This project will ensure weight reduction as well as an improved design, that makes use of electro pneumatic braking system.
16
Dong, Ze Jiao, Zong Jie Sun, Xiang Bing Gong e Hao Liu. "Mechanism Analysis of Rutting at Urban Intersections Based on Numerical Simulation of Moving Loads". Advanced Materials Research 152-153 (ottobre 2010): 1192–98. http://dx.doi.org/10.4028/www.scientific.net/amr.152-153.1192.
Testo completoAbstract (sommario):
Frequent starting and braking of vehicles causes rutting of asphalt pavement at urban intersection. As a result, dynamic response of pavement subjected to these kinds of vehicle loadings can be used to analyze rutting mechanism. At first, vehicle loading at urban intersection was described by a vertical and horizontal combined moving pressure with variable speeds. Then, three-dimensional finite element model in transient dynamic mode is developed based on the practical pavement structure. And the moving load, boundary conditions and material parameters were briefly introduced. Finally, through the comparison of time histories and spatial distribution among accelerating, decelerating and uniform motion, mechanism of rutting of asphalt pavement at urban intersections was illustrated according to the finite element simulation. It shows that frequent starting and braking of vehicle at urban intersections, obviously change the stress distribution within pavement structure compared with uniform motion case. The distribution and amplitude of maximum shear stress and horizontal shear stress was observed during the passage of the loading, which will result in shear flow deformation. Pavement structure subjected to moving load exhibits an alternative characteristic which will accelerate the rutting damage of pavement.
17
Kumar, N. Satheesh. "Increasing the Cruise Range and Reducing the Capital Cost of Electric Vehicles by Integrating Auxiliary Unit with the Traction Drive". International Journal of Vehicular Technology 2016 (10 febbraio 2016): 1–11. http://dx.doi.org/10.1155/2016/7617692.
Testo completoAbstract (sommario):
Poor cruise performance of Electric Vehicles (EVs) continues to be the primary reason that impends their market penetration. Adding more battery to extend the cruise range is not a viable solution as it increases the structural weight and capital cost of the EV. Simulations identified that a vehicle spends on average 15% of its total time in braking, signifying an immense potential of the utilization of regenerative braking mechanism. Based on the analysis, a 3 kW auxiliary electrical unit coupled with the traction drive during braking events increases the recoverable energy by 8.4%. In addition, the simulation revealed that, on average, the energy drawn from the battery is reduced by 3.2% when traction drive is integrated with the air-conditioning compressor (an auxiliary electrical load). A practical design solution of the integrated unit is also included in the paper. Based on the findings, it is evident that the integration of an auxiliary unit with the traction drive results in enhancing the energy capturing capacity of the regenerative braking mechanism and decreases the power consumed from the battery. Further, the integrated unit boosts other advantages such as reduced material cost, improved reliability, and a compact and lightweight design.
18
Ajmal, Aidha Muhammad, e V. K. Ramachandaramurthy. "Regenerative Braking of Electric Vehicle with Brushless DC Motor". Applied Mechanics and Materials 785 (agosto 2015): 280–84. http://dx.doi.org/10.4028/www.scientific.net/amm.785.280.
Testo completoAbstract (sommario):
Given the volatile market prices and impending reduction in fuel supplies, electric vehicles (EV) have drawn increasing attention. The electric motor in EVs is an important component because it functions as an engine during acceleration and as a generator during deceleration or braking. Energy is saved in these processes when the kinetic energy is converted into electrical energy, which is then stored in a storage system by a regenerative braking system (RBS). In terms of highly efficient performance, ideal torque and speed, high-powered density, and cost-effective maintenance, brushless DC (BLDC) motors are preferred. This paper aims to explore and propose a seamless and effective method of RBS for a BLDC motor in an EV. In braking mode, the proposed method change the motor to act as a generator even without any additional converter, ultra-capacitor, or a complex winding-changeover technique. In this mechanism, the energy flows to the DC side. By using MATLAB/SIMULINK, the BLDC motor with speed and current controller is simulated. Accordingly, in the deceleration or braking mode, the motor functions as a generator and transports the power to the DC side. The proposed model is validated in both starting or no-load and load conditions.
19
Zhang, Lei, Jie Xuan Lou e En Guo Dong. "Robust Integrated Design for Vehicle Chassis Based on Uncertainties". Applied Mechanics and Materials 644-650 (settembre 2014): 29–32. http://dx.doi.org/10.4028/www.scientific.net/amm.644-650.29.
Testo completoAbstract (sommario):
In order to improve overall vehicle performance and decrease movement deviation caused by uncertainties from automobile chassis, a robust vehicle chassis model is built with steering system, suspension system and braking system. In the model, the length of the steering trapezoid arm, the bottom angle of trapezoid mechanism, inclination angle, caster, camber and toe-in are defined as controllable variables, and load, driving force, steering torque are defined as noise factors. The optimum objectives include the maximum turning angle error of steering mechanism, the maximum braking sideslip and the maximum swing angle of front wheel on bumpy road. Taguchi method is applied to solve the robust result for automobile chassis model. Compared that the variances of objective values are decreased with the same noise factors and the robustness of sub-systems of chassis is improved.
20
Wang, Kuiyang, Ren He, Jinhua Tang e Ruochen Liu. "Performances Analysis of a Novel Electromagnetic-Frictional Integrated Brake Based on Multi-Physical Fields Coupling". World Electric Vehicle Journal 10, n. 1 (21 febbraio 2019): 9. http://dx.doi.org/10.3390/wevj10010009.
Testo completoAbstract (sommario):
In this article, a novel electromagnetic-frictional integrated brake is proposed, and its structure and working principle are introduced. The geometric model and mathematical models of integrated brake were established, and the multi-field coupling mechanism of integrated brake were analyzed. With BYD Qin as a reference vehicle, the boundary conditions of thermal load and force load of integrated brake were determined according to its structure and performance parameters. Based on the COMSOL software, numerical coupling calculations of electric, magnetic, thermal, and solid fields of integrated brake were carried out respectively in the emergency and downhill braking at a constant speed. The axial, circumferential, and radial temperature distributions of integrated brake disc were analyzed respectively, and they were compared with those of the traditional friction brake disc. The analysis results show that the proposed integrated brake can effectively improve the heat fading resistance of automotive brake during emergency and continuous braking. Under the two braking conditions, the temperature rise of friction brake was faster than that of an electromagnetic brake, and the effect of the electromagnetic brake on temperature rise of integrated brake was small.
21
Tran, Minh Thi, Kok Keng Ang e Van Hai Luong. "Multiple-Railcar High-Speed Train Subject to Braking". International Journal of Structural Stability and Dynamics 17, n. 07 (settembre 2017): 1750071. http://dx.doi.org/10.1142/s0219455417500717.
Testo completoAbstract (sommario):
The dynamic response of a high-speed multiple-railcar train experiencing deceleration under braking condition over a straight track is investigated using the moving element method. Possible sliding of train wheels over the rails is accounted for. The train is assumed to comprise a locomotive as the leading railcar and several passenger railcars connected to each other through train couplers. Each railcar is modeled as a 15-DOF system of interconnected car body, two bogies and four wheels. The rail is modeled as an Euler–Bernoulli beam resting on a two-parameter elastic damped foundation. The train and rails are coupled through normal and tangential wheel–rail contact forces. The effects of various parameters, such as braking torque, coupler stiffness, coupler gap, wheel load, wheel–rail contact condition, initial train speed and partial failure in braking mechanism on the dynamic response of the train subject to braking are investigated. It is found that there is significant interaction between neighboring railcars when the braking torque is applied between the optimal and critical torques. The former is the torque that would result in the smallest braking distance with no occurrence of wheel sliding and the latter is the smallest torque to cause wheel sliding in all four wheels.
22
Klingbeil, W. W., e H. W. H. Witt. "Some Consequences of Coulomb Friction in Modeling Longitudinal Traction". Tire Science and Technology 18, n. 1 (1 gennaio 1990): 13–65. http://dx.doi.org/10.2346/1.2141691.
Testo completoAbstract (sommario):
Abstract A three-component model for a belted radial tire, previously developed by the authors for free rolling without slip, is generalized to include longitudinal forces and deformations associated with driving and braking. Surface tractions at the tire-road interface are governed by a Coulomb friction law in which the coefficient of friction is assumed to be constant. After a brief review of the model, the mechanism of interfacial shear force generation is delineated and explored under traction with perfect adhesion. Addition of the friction law then leads to the inception of slide zones, which propagate through the footprint with increasing severity of maneuvers. Different behavior patterns under driving and braking are emphasized, with comparisons being given of sliding displacements, sliding velocities, and frictional work at the tire-road interface. As a further application of the model, the effect of friction coefficient and of test variables such as load, deflection, and inflation pressure on braking stiffness are computed and compared to analogous predictions on the braking spring rate.
23
Cheng, Meng Ting, Chun Tian, Meng Ling Wu e Ying Xi. "Design of the Wind Channel for the Test-Bed of Aerodynamic Brake". Applied Mechanics and Materials 275-277 (gennaio 2013): 584–89. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.584.
Testo completoAbstract (sommario):
For simulating the wind load strength effect so as to detect the opening and closing performance of the aerodynamic braking device and the reliability of its opening and closing mechanism with the wind load caused by high speed flow field, the wind load test-bed is to build. Wind channel, as the equipment to turn a high pressure flow into a relatively high speed advection, is one of its important components. This paper focuses on the design of the shape of the wind channel. By the means of flow field simulation analysis, with the indexes of the wind load size, the pressure distribution and the flow equality, the shape optimization of the wind channel is realized.
24
Kannan, Kasi Rajesh, Ramalingam Vaira Vignesh, Kota Pavan Kalyan e Myilsamy Govindaraju. "Development and tribological characterization of fly ash reinforced iron based functionally gradient friction materials". Engineering review 41, n. 3 (2021): 20–28. http://dx.doi.org/10.30765/er.1501.
Testo completoAbstract (sommario):
The tribological and thermal properties enable iron based sintered materials with hard phase ceramic reinforcements as promising friction material for heavy-duty wind turbines. In wind turbines, the braking system consists of aerodynamic and mechanical braking systems. During application of mechanical brakes, the friction materials are pressed against the rotating low-speed shaft. The desired braking efficiency is achieved by utilizing a number of friction materials, which in turn are joined in a steel backing plate. Though this arrangement increases the braking efficiency, the hard phase ceramic reinforcement particles reduces the bonding strength between the friction material and steel backing plate. The joint failure leads to catastrophic failure of wind turbine. Therefore, the need of the hour is to develop friction materials with functional gradients that have high wear resistance (contact area) and high bond strength (interface). In this study, an attempt is made to fabricate and characterize a friction material with gradient profile of composition along the cross section to provide functional gradient property. The functional gradient friction material is synthesized by gradient deposition of Fe, Cu, Cg, SiC and fly ash powders which is then compacted and sintered. The prepared functional gradient friction material was characterized in terms of microstructure and microhardness. The tribological performance (wear rate and coefficient of friction) of the developed functionally gradient friction material was investigated at various loads using pin-on disc apparatus. The results show that as the load increases, the wear rate decreases and at the same time the COF tends to increase at higher loads. The predominant wear mechanism was deduced from the morphology of the worn surface.
25
Mathews, Joel Abraham. "Designing & Analysis of Supercapacitor Hybrid Battery System with Regenerative Braking". International Journal for Research in Applied Science and Engineering Technology 9, n. 11 (30 novembre 2021): 894–901. http://dx.doi.org/10.22214/ijraset.2021.38925.
Testo completoAbstract (sommario):
Abstract: This work implements the help of a super capacitor hybridized with a battery pack to power a motor to work an electric bike. The supercapacitor of specification is built in combination with the battery pack to work in pair at instances where more load in needed. For example in situations like accelerating, decelerating, and climbing a slope. The supercapacitor is recharged while in motion using two different technologies: 1. Regenerative Braking and 2. Generator incorporated into wheel hub. Regenerative braking is an energy recovery mechanism that slows down a moving vehicle or object by converting its kinetic energy into a form that can be either used immediately or stored until needed. In this mechanism, the electric traction motor uses the vehicle's momentum to recover energy that would otherwise be lost to the brake discs as heat. This contrasts with conventional braking systems, where the excess kinetic energy is converted to unwanted and wasted heat due to friction in the brakes, or with dynamic brakes, where the energy is recovered by using electric motors as generators but is immediately dissipated as heat in resistors. In addition to improving the overall efficiency of the vehicle, regeneration can significantly extend the life of the braking system as the mechanical parts will not wear out very quickly. The system uses Faradays Law of Electromagnetic Induction to induce an EMF and generate voltage by passing a current carrying conductor through a rotating magnetic field. Using this implementation, it has been noted that the battery life has been increased significantly and the total range of the bike has also increased considerably. Keywords: Batteries, Battery pack, Supercapacitor, Hybrid power system, Dynamo mechanism
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Tian, Chun, Meng Ling Wu, Cheng Li e Lu Zhu. "The Optimization Design of Opening and Closing Mechanism of Aerodynamic Braking in High-Speed Train". Applied Mechanics and Materials 365-366 (agosto 2013): 444–49. http://dx.doi.org/10.4028/www.scientific.net/amm.365-366.444.
Testo completoAbstract (sommario):
Aerodynamic brake is a new type of non-adhesion brake mode used to high-speed train brake by unfolding the brake panel on the roof of the high speed train to increase aerodynamic resistance. This brake mode is effective especially in the condition of high speed. The article is aimed at designing a set of opening and closing mechanism to control the movement of the brake panel. The opening and closing mechanism mainly include three components of guide mechanism, the center of rotation and drive mechanism. The guide mechanism as auxiliary orientation is a functional unit of the bearing parts used to improve the movement and load conditions of the brake panel. The center of rotation is the key component to support the brake panel and transmit the braking force. The drive mechanism, the power source of the opening and closing mechanism, is designed to drive the brake panel up and down in the reciprocating motion. This paper focuses on the design of the three components, using the method of combining structural design and reliability design and aiming at the final optimal design.
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Popov, I. P. "MATHEMATICAL MODELING OF A MULTI-INERT OSCILLATORY MECHANISM". Bulletin of the South Ural State University series "Mechanical Engineering Industry" 20, n. 1 (2020): 22–29. http://dx.doi.org/10.14529/engin200103.
Testo completoAbstract (sommario):
It is noted that the free harmonic vibrations of a classical pendulum are due to the mutual conversion of the kinetic energy of the load intothe potential energy of the spring. Oscillators with a different nature of energy exchange have been developed, for example, by converting the kinetic energy of a load into the energy of a magnetic field of a solenoid or the energy of an electric field of a capacitor. All these oscillatory systems and the like were a prerequisite for the creation of a biinert oscillator,in which the acceleration of one load occurs due to the braking of another, i. e. only kinetic energies are exchanged. The aim of the work is mathematical modeling of a multi-inert oscillatory mechanism. The main research methods in the framework of this work are methods of mathematical modeling and analysis. The methods used make it possible to obtain a reliable description of the studied objects. Inthe proposed multi-inert oscillator, inert bodies of mass m each carry out harmonic oscillations due to the mutual exchange of kinetic energy. The potential energy of the springs is not requiredfor this. Body vibrationsare free. A feature of a multi-inert oscillator is that the frequency of itsfree oscillations is not fixed and is determined mainly by the initial conditions. This feature can be very useful for technical applications, for example, for self-neutralization of mechanical reactive (inertial) power. n-gon, formed by inert bodies, carries out complex motion – orbital rotation around the center of coordinates and spin rotation around its axis passing through the center of the n-gon. Moreover, each load performs linear harmonic oscillations along its guide. With the arrangement of the guiding weights not in the form of a star, but in parallel to each other, the angles between the corresponding cranks must be 360/n degrees.
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Pan, Like, Jianmin Han, Zhiyong Yang, Jialin Wang, Xiang Li, Zhiqiang Li e Weijing Li. "Temperature Effects on the Friction and Wear Behaviors of SiCp/A356 Composite against Semimetallic Materials". Advances in Materials Science and Engineering 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/1824080.
Testo completoAbstract (sommario):
Due to the low density and high temperature resistance, the SiCp/A356 composites have great potential for weight reduction and braking performance using the brake disc used in trains and automobiles. But the friction coefficient and braking performance are not stable in the braking process because of temperature rising. In this paper, friction and wear behaviors of SiCp/A356 composite against semimetallic materials were investigated in a ring-on-disc configuration in the temperature range of 30°C to 300°C. Experiments were conducted at a constant sliding speed of 1.4 m/s and an applied load of 200 N. Worn surface, subsurface, and wear debris were also examined by using SEM and EDS techniques. The third body films (TBFs) lubricated wear transferred to the third body abrasive wear above 200°C, which was a transition temperature. The friction coefficient decreased and weight of semimetallic materials increased with the increase of temperature and the temperature had almost no effect on the weight loss of composites. The dominant wear mechanism of the composites was microploughing and slight adhesion below 200°C, while being controlled by cutting grooves, severe adhesion, and delamination above the 200°C.
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Mel'nikov, A. S., O. V. Bilyk, Ki-Yong Choy e A. A. Mel'nikov. "BRAKE OF THE FRONT DRIVE WHEELS OF THE TRACTOR "BELARUS"". Traktory i sel hozmashiny 84, n. 3 (15 marzo 2017): 33–40. http://dx.doi.org/10.17816/0321-4443-66271.
Testo completoAbstract (sommario):
The increase in the energy saturation of the new models of tractors "Belarus", as well as the mass of towed trailers and agro-technological tools that are mounted with them, required an increase in the efficiency of the tractor braking system. The purpose of the study is to increase the efficiency of the braking system of the wheeled tractor "Belarus MTZ" by creating wheel brakes for the front axle with minimal changes in its standard design. The developed drum brake with hydraulic drive of the front drive wheels of the tractor "Belarus MTZ-1221" does not require significant changes in the standard design of the front axle of the MTZ tractor and is adaptive to the anti-lock system, which operates on the basis of measurement and analysis of force factors. The design of the developed brake mechanism allows its adaptation to the anti-lock system, which operates on the basis of measuring and analyzing the forces that arise in the contact of the wheels of the front axle of the tractor with the supporting surface. The braking effect of the tractor "Belarus MTZ-1221" is provided by additional use of its coupling weight, which falls on its front axle. A set of design documentation for the drum brake for the front driving wheels of the tractor "Belarus MTZ-1221" was developed. The use of an additional traction weight of the tractor due to the wheel brakes of the wheels of the front axle of the tractor "Belarus MTZ-1221" will increase the efficiency of its braking, as well as increase the competitiveness of wheeled tractors produced by the JSC "Minsk tractor works". Bench tests confirmed the possibility of braking the calculated moments corresponding to the weight load on the front axle of the tractor "Belarus MTZ-1221". Consequently, the developed brake mechanism will ensure effective use of the tractive weight of "Belarus MTZ-1221" tractor.
30
Liu, Ke, Feng Yang, Zhiyan Yang, Yunxian Zhu e Yongguang Cheng. "Runner Lifting-Up during Load Rejection Transients of a Kaplan Turbine: Flow Mechanism and Solution". Energies 12, n. 24 (15 dicembre 2019): 4781. http://dx.doi.org/10.3390/en12244781.
Testo completoAbstract (sommario):
Dangerous runner lifting-up (RLU) accidents regarding Kaplan turbines, which are widely used in low-head hydropower stations, were frequently reported. Three-dimensional (3D) computational fluid dynamics (CFD) was used to simulate the load rejection transients with guide-vane closing to predict the RLU possibility of the fixed-blade Kaplan turbine in an under-construction hydropower station. It was found that using any linear closing rule, the upward axial water force on the runner was larger than the weight of rotating parts that started before the guide-vanes were closed, which indicated a RLU possibility. It was the pumping effect that caused the imbalance, during which the high rotational speed runner propels water downstream with a low discharge. We proposed a piecewise closing rule based on this finding. By keeping the opening unchanged in a period in the closing process, the rotational speed can be reduced by using the braking effect, and the concurrence of high speed and low discharge can be prevented. Simulations verified this effective measure and accepted by the manufacturer. Although this study used a fixed-blade Kaplan turbine, the revealed mechanism and verified solution to the RLU problem have reference value for all of the Kaplan turbines.
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Lin, M. C., S. A. Velinsky e B. Ravani. "Design of the Ball Screw Mechanism for Optimal Efficiency". Journal of Mechanical Design 116, n. 3 (1 settembre 1994): 856–61. http://dx.doi.org/10.1115/1.2919460.
Testo completoAbstract (sommario):
This paper develops theories for evaluating the efficiency of the ball screw mechanism and additionally, for designing this mechanism. Initially, a quasi-static analysis, which is similar to that of the early work in this area, is employed to evaluate efficiency. Dynamic forces, which are neglected by the quasi-static analysis, will have an effect on efficiency. Thus, an exact theory based on the simultaneous solution of both the Newton-Euler equations of motion and the relevant kinematic equations is employed to determine mechanism efficiency, as well as the steady-state motion of all components within the ball screw. However, the development of design methods based on this exact theory is difficult due to the extensive computation necessary and thus, an approximate closed-form representation, that still accounts for the ball screw dynamics, is derived. The validity of this closed-form solution is proven and it is then used in developing an optimum design methodology for the ball screw mechanism based on efficiency. Additionally, the self-braking condition is examined, as are load capacity considerations.
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Sukumar, T., BR Ramesh Bapu e B. Durga Prasad. "Prediction of hyperelastic material sealing pressure using experimental and numerical analyses". Journal of Elastomers & Plastics 52, n. 8 (3 dicembre 2019): 717–27. http://dx.doi.org/10.1177/0095244319891211.
Testo completoAbstract (sommario):
In commercial vehicle air braking system, leakage is one of the major problems and will affect the performance of the vehicle braking in terms of brake pedal travel and stopping distance. If there is any leakage in the brake system, the vehicle stopping distance will not meet the safety regulations. One of the main reasons for braking system leakage is ineffective sealing mechanism. The majority of sealing elements used in the air brake system are O-rings, lip seals, and gaskets. This article presents an experimental procedure for measuring the sealing pressure between an O-Ring and its mating parts. The contact pressure measurement was performed in a static condition by means of an experimental test rig using Fuji film. For the sealing pressure study, a test rig was properly designed to replicate the actual operating conditions. Contact pressure was evaluated by means of Fuji film interposed between the O-ring and its mating parts. The sealing pressure tests were carried out for different clamping load conditions. The experimental results were compared with the numerical result using the finite-element analysis (FEA). A good correlation was found between the experimental and the numerical results. The outcome from the experimental results will be useful for finalizing the hyperelastic material models, which are input to the FEA for future reference.
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Yamafuji, K., V. Gradetsky, M. Rachkov e E. Semenov. "Mechatronics Drive for Intelligent Wall Climbing Robot". Journal of Robotics and Mechatronics 5, n. 2 (20 aprile 1993): 164–71. http://dx.doi.org/10.20965/jrm.1993.p0164.
Testo completoAbstract (sommario):
A new type of mechatronics drive is proposed for an intelligent wall climbing robot in order to satisfy strong load characteristics with velocity and force control on a large scale. The mechatronics drive consists of a pneumatics force piston-cylinder system, electromechanical subcontrol system, and electronic microprocessor control system. The power of mechatronics drive is achieved by means of a pneumatic force piston, and control is attained by internal and external feedback loops of the electromechanical system. The microprocessor system is intended for programming motion. The control moment transmitted from the electromechanical system to the self-braking worming mechanism and gears to the pneumatic piston. The sensory system measures the required parameters as position, pressure, and force. The pneumatic cylinder is mounted on the board of mobile robot. Data of the simulation and experimental investigation of the drive are presented. As the result of investigations, the drive realized the application for the intelligent wall climbing robot for the transportation the loads of more than 100kg on vertical surfaces.
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Посметьев, Viktor Posmetev, Канищев, Denis Kanishchev, Попиков, Petr Popikov, Стороженко e Stanislav Storozhenko. "Modeling workflows of energy-saving hydraulic drive of technological equipment of timber-hauling machine". Forestry Engineering Journal 5, n. 1 (1 maggio 2015): 223–34. http://dx.doi.org/10.12737/11280.
Testo completoAbstract (sommario):
Workflow mechanisms of forestry cranes tower rotation are accompanied by large dynamic loads that cause sudden changes in fluid pressure in balancing and braking modes. When the rotary column stops at different positions damping of pressure of the working fluid vibration occurs due to its overflow from one chamber to another through an orifice, wherein the hydraulic energy is transformed into heat one, resulting in overheating and energy loss of fluid. Efficient are energy-saving hydropneumatic drives of column of the manipulator which are able to recover energy during transient conditions and to return some of the energy back into the system. For hydraulic manipulators with four paired hydraulic cylinders of rotation mechanism of the column one pair of cylinders is proposed to be replaced by pneumatic cylinders connected to a rotary column through the gear and toothed rack that allows you to transfer it into recovery mode of energy. A mathematical model of the boom rotation of the manipulator is developed; equations for a hydro pneumatic system recovery are made. In the model three mechanical processes are considered: the rotational movement of the column about the vertical axis of the manipulator, the forward movement of the plunger along the axis of the damper, and sway of the load relative to the attachment point on the manipulator arm. To solve the system of differential equations, computer program for the simulation of hydraulic manipulator equipped with a hydraulic damper is composed. The dependence of the restoring force of the displacement of the toothed rack is get. In the vicinity of the equilibrium position, this dependence is nearly linear over a wide range of rack movement: from about 50 to 180 mm. With significant turns of the column volume of one of the chambers of the air cylinder approaches zero value, whereby the restoring force of the module increases significantly, which helps braking of the column in the final step of rotation and influences the process of energy accumulation.
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Chu, Yuanbo, Zhaohui Yuan, Xuegong He e Zhichao Dong. "Model Construction and Performance Degradation Characteristics of a Deflector Jet Pressure Servo Valve under the Condition of Oil Contamination". International Journal of Aerospace Engineering 2021 (27 febbraio 2021): 1–17. http://dx.doi.org/10.1155/2021/8840084.
Testo completoAbstract (sommario):
The deflector jet pressure servo valve is a kind of high-precision hydraulic component that can be widely used in the antiskid braking system of an aircraft. In actual service, it will be faced with extreme working conditions of gradual oil contamination, which will cause performance degradation and function maladjustment of the whole valve. To this end, the paper proposes a performance degradation characteristic analysis method. In which, firstly, the structural characteristics and working principle of the deflector jet pressure valve are analyzed; then, the entire dynamics model of the pressure valve is built using the braking cavity as the load blind cavity. Secondly, the two main failure modes induced by oil contamination such as erosion wear of pilot stage and stuck of slide valve stage’s valve core are determined based on the engineering experience, aimed at which the failure mechanism is analyzed; then, the sensitivity simulation model of the servo valve’s output pressure with respect to key degradation parameters is established and the sensitivity analysis is performed. Finally, combining the theoretical analysis with multiphysics simulation correction methods, the performance degradation model of the typical failure modes are established, and then, the performance degradation characteristics under dynamic contamination conditions are analyzed, which is combined with the failure threshold determined by the dynamics simulation to finish the service life prediction of the deflector jet servo valve.
36
Zulfikar, Zulfikar, Bobby Umroh, Amrinsyah Amrinsyah e Fadly A. Kurniawan. "NUMERICAL ANALYSIS OF STRENGTH OF REAR BRAKE HOLDER FLAT ON THE MOTOR CYCLE DUE TO IMPACT LOAD". JOURNAL OF MECHANICAL ENGINEERING, MANUFACTURES, MATERIALS AND ENERGY 2, n. 1 (13 luglio 2018): 1. http://dx.doi.org/10.31289/jmemme.v2i1.1648.
Testo completoAbstract (sommario):
<span class="12paswordenglishChar"><span>Brake is one of vital motorcycle element, which serves as a speed reduction mechanism. This section reinforced with retaining plate which serves to hold the wheels when braking process occurs. Research on the plate strength is still rarely found. Stress distribution that occurs on the plate due to shock loads is also not well known. Therefore, this study aims to obtain the strength retaining plate with a numerical analysis of the distribution of stress and deformation which occur on plate. Research done in two ways, experimentally and numerical simulations. Experimentally, direct measurements on the amount of stress that occurs on the plate. The research was done by putting strain gage on the connection plate and brake. In simulation, using Nastran software with the primary data based on the results of the experimental measurements. Based on the results of the numerical analysis of the stress distribution that occurs is obtained that the maximum stress distributed around the staging area in direct contact with the brake. Therefore, motorists should be aware that section and provide additional anchoring structure to further strengthen the structure of the retaining plate rear brake.</span></span>
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Zhao, Fujun, Yu Li, Zhouyuan Ye, Yong Fan, Siping Zhang, Haifan Wang e Yonghong Liu. "Research on Acoustic Emission and Electromagnetic Emission Characteristics of Rock Fragmentation at Different Loading Rates". Shock and Vibration 2018 (2018): 1–8. http://dx.doi.org/10.1155/2018/4680879.
Testo completoAbstract (sommario):
The relationships among the generation of acoustic emission, electromagnetic emission, and the fracture stress of rock grain are investigated, which are based on the mechanism of acoustic emission and electromagnetic emission produced in the process of indenting rock. Based on the relationships, the influence of loading rate on the characteristics of acoustic emission and electromagnetic emission of rock fragmentation is further discussed. Experiment on rock braking was carried out with three loading rates of 0.001 mm/s, 0.01 mm/s, and 0.1 mm/s. The results show that the phenomenon of acoustic emission and electromagnetic emission is produced during the process of loading and breaking rock. The wave forms of the two signals and the curve of the cutter indenting load show jumping characteristics. Both curves have good agreement with each other. With the increase of loading rate, the acoustic emission and electromagnetic emission signals are enhanced. Through analysis, it is found that the peak count rate, the energy rate of acoustic emission, the peak intensity, the number of pulses of the electromagnetic emission, and the loading rate have a positive correlation with each other. The experimental results agree with the theoretical analysis. The proposed studies can lead to an in-depth understanding of the rock fragmentation mechanism and help to prevent rock dynamic disasters.
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Qian, Xia Yi, Chen Bo Yin e Feng Ma. "Methods for Determining the Dynamic Load of the Shipbuilding Gantry Crane". Advanced Materials Research 605-607 (dicembre 2012): 1288–94. http://dx.doi.org/10.4028/www.scientific.net/amr.605-607.1288.
Testo completoAbstract (sommario):
Aim at the difficulty in determining the dynamic load , dynamic problems were analyzed, including three mechanisms of the shipbuilding gantry crane of lifting、trolley running and cart running under the joint starting and braking by adopting the method for determining the dynamic load based on the vibration theory and the one for determining the dynamic load based on the virtual prototype.Dynamic models and virtual prototype model were established and the time-varying dynamic loads of mechanisms were determined under typical working conditions. The maximum dynamic load obtained provides a reference for the dynamic finite element analysis of the shipbuilding gantry crane.
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Baris, AV. "Self-braking harmonic drives in mechanisms of mining machines". IOP Conference Series: Earth and Environmental Science 991, n. 1 (1 febbraio 2022): 012014. http://dx.doi.org/10.1088/1755-1315/991/1/012014.
Testo completoAbstract (sommario):
Abstract The conditions of self-braking in harmonic drives with a flexible wheel made in the form of a bushing chain are considered. A special feature of the harmonic drive is the design that has a dual generator and a double-crowned sprocket. This design allows to avoid skewing the chain under load. The criteria for self-braking in chain harmonic drives are defined. It is found that for chain harmonic drives in the range of gear ratios above 30, the effect of self-braking is provided. In the range of gear ratios up to 30, extra-centroid gearing is required to achieve the effect of self-braking.
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GUTAREVICH, Viktor, e Marina KONDRATENKO. "DYNAMICS OF TRACTION DEVICE OF MINE SUSPENDED MONOREL ROAD". Sustainable Development of Mountain Territories 12, n. 3 (30 settembre 2020): 410–17. http://dx.doi.org/10.21177/1998-4502-2020-12-3-410-417.
Testo completoAbstract (sommario):
During the operation of the mine suspension monorail track and traction device form a mechanical system experiencing high dynamic loads associated with implementation of traction and braking forces. Emerging dynamic loads lead to formation of elastic deformations and oscillations that cause vibrations, which leads to displacement of drive wheels and reduces the implementation of traction. The study of the dynamics of traction device is an important step in improving safety and reliability of monorail transport. The aim of the work is to study dynamics of a friction-type traction device moving along a suspended monorail to assess influence of parameters of the elements of device on the vibrations and nature of interaction of drive wheels with monorail. Research methods. Mathematical modeling of the oscillatory processes resulting from interaction of the running gear of the traction device with the monorail is used. Stages of research include drawing up a design diagram oscillations of drive wheels of the traction device interacting with the monorail, developing a mathematical model for the analysis of vibrations caused by moving loads, also assessing the influence of structural parameters of mechanical system under consideration on nature of oscillations. Research results. The developed mathematical model of friction-type traction device movement allows us to establish relationship between parameters of structural elements of its running gear and pressure mechanism, as well as nature of vibrations that arise. As a result, frequencies of the mechanical system under consideration and maximum deviations were found, which allows you to set optimal device parameters to increase traction and increase lifespan of monorail suspended roads. Findings. It was determined that the frequency range of vibration of drive wheels mainly corresponds to the mid-frequency local vibrations of 16–36 Hz. Increasing length of lever for fixing axles of wheels and reducing their radius leads to formation of low-frequency vibrations with a frequency of less than 15 Hz. When length of lever of drive wheels is more than 0.5 m, shoulder of the spring is more than 0.6 m and radius of drive wheels is less than 0.25 m, vibrations with frequencies below 5 Hz can occur. It was found that increasing the length of lever for securing spring increases the oscillation frequency of one drive wheel and reduces frequency of the other. The difference between these frequencies significantly affects changes in the pressure of the wheels against monorail. When difference between frequencies is more than 10–12 Hz, direction of load changes pulsed, with a maximum swing of 0.02 rad, which reduces formation of fatigue fractures of tire wheels, and moments of decrease and increase in pressing force have a negative effect on traction, leading to slippage of drive wheels. When difference between frequencies is less than 10–12 Hz, direction of the load changes sharply, with a maximum swing of 0.03 rad, which increases deformation and formation of fatigue fractures of tire wheels, and short moments of weakening and increase of pressing force, constituting 0.1–0.3 s does not have a significant negative effect on traction.
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Michałowski, Stanisław, e Wiesław Cichocki. "The Peak Dynamic Loading of a Winch in Term of the Rope Flexibility". Key Engineering Materials 542 (febbraio 2013): 105–17. http://dx.doi.org/10.4028/www.scientific.net/kem.542.105.
Testo completoAbstract (sommario):
The cable winch is modeled as a system with two degrees of freedom during a start-up and braking phase for two basic operating cases: raising a lifted load case and elastic bond tensed by a raised load force case. The theoretical calculations were verified with experimental studies. Consequently, it is possible to define the winch drive overloads factor. Moreover, the determination of the number of stress change cycles in the rope can be performed. This important is with regard on possibility of rise in the rope the fatigue cracks. In dynamic experiments, three typical cases of raising mechanisms were taking into account: lifting the load with raising it, lifting the load with tensed rope and braking the load while lowering.
42
Yang, X., e S. Medepalli. "Comfort and Durability Tire Model Validation3". Tire Science and Technology 37, n. 4 (1 dicembre 2009): 302–22. http://dx.doi.org/10.2346/1.3251339.
Testo completoAbstract (sommario):
Abstract In this study, a systematic validation of comfort and durability tire models (CDT) using LMS software was performed by focusing on the measured tire data collection, bench test, and full vehicle model predictions. Different road events are considered in the validation process, including deterministic and random type roads, as well as braking/accelerating and cornering events. The study shows that the current version of commercial CDT models is reasonably accurate for durability road loads simulation, but requires simulation time improvement. The seven published SAE J-documents for road load tire model parameterization tests cover the necessary data to parameterize the CDT model for “non-misuse” road loads simulation.
43
Goo, Byeong Choon, e Jung Won Seo. "Finite Element Analysis of the Rolling Contact Fatigue Life of Railcar Wheels". Materials Science Forum 575-578 (aprile 2008): 1461–66. http://dx.doi.org/10.4028/www.scientific.net/msf.575-578.1461.
Testo completoAbstract (sommario):
Railcar wheels and axles belong to the most critical components in railway vehicles. The service conditions of railway vehicles have been more severe in recent years due to speed-up. Therefore, a more precise evaluation of railcar wheel life and safety has been requested. Wheel/rail contact fatigue and thermal cracks due to braking are two major mechanisms of the railcar wheel failure. One of the main sources influencing on the contact zone failure is residual stress. The residual stress in wheels formed during heat treatment in manufacturing changes in the process of braking. Thus the fatigue life of railcar wheels should be estimated by considering both thermal stress and rolling contact. Also, the effect of residual stress variation due to manufacturing process and braking process should be included in simulating contact fatigue behavior. In this paper, an evaluation procedure for the contact fatigue life of railcar wheels considering the effects of residual stresses due to heat treatment, braking and repeated contact load is proposed. And the cyclic stressstrain history for fatigue analysis is simulated by finite element analysis for the moving contact load.
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Volianiuk, Volodymyr, Ievgenii Gorbatyuk e Dmitry Mishchuk. "The inertial loads of a telescopic boom of a truck crane". Automobile transport, n. 49 (24 dicembre 2021): 54–62. http://dx.doi.org/10.30977/at.2019-8342.2021.0.49.01.
Testo completoAbstract (sommario):
Problem. The analysis of existing research and publications in which the main problem is highlighted, namely, that many factors are not taken into account when calculating the inertial loads of the car crane arrows. Accounting for these factors will allow you to more accurately determine the inertial loads of the boom of the car crane, to carry out strength-hunches of the elements of the boom and the selection of components of its drive mechanisms. Goal. The purpose of the work is to determine the inertial navan-loads acting on the load and arrow of the automobile-side crane during the unstable movement of its. Methodology. To calculate the inertial loads, the technique of determining the total inertial loads of the car crane boom during joint operations in accordance with the Safety Regulations has been developed. Total inertial loads were determined for the following cases: joint lifting (lowering) of cargo and arrows; lifting the load and turning the boom; lifting and turning the arrow. Results. The resulting dependencies for determining the inertial loads of the rotary boom of the car crane will allow more accurately taking into account multiple factors to calculate the values of these loads in order to conduct strong calculations of the boom, the selection of its components mechanisms. Originality. When calculating inertial loads, the weight and length of the boom are taken into account; weight and height of lifting of cargo; the radius of the arrow crane; rotation speed of the rotary part of the crane; speed of movement of cargo and arrows; start time and braking of cargo lifting mechanisms, change of departure and turn of the boom. The advantage of this technique is its originality. Practical value. The use of this technique allows more accurately taking into account multiple factors to determine the values of the inertial loads of the automobile crane during the unstable movement of the cargo lifting mechanisms, changes in the discharge of the boom and its rotation in order to conduct strong-standing calculations of the boom elements, the selection of its components.
45
Jeusette, J. P., e M. Theves. "Finite Element Analysis of Tire/Rim Interface Forces Under Braking and Cornering Loads". Tire Science and Technology 20, n. 2 (1 aprile 1992): 83–105. http://dx.doi.org/10.2346/1.2139512.
Testo completoAbstract (sommario):
Abstract During vehicle braking and cornering, the tire's footprint region may see high normal contact pressures and in-plane shear stresses. The corresponding resultant forces and moments are transferred to the wheel. The optimal design of the tire bead area and the wheel requires a detailed knowledge of the contact pressure and shear stress distributions at the tire/rim interface. In this study, the forces and moments obtained from the simulation of a vehicle in stationary braking/cornering conditions are applied to a quasi-static braking/cornering tire finite element model. Detailed contact pressure and shear stress distributions at the tire/rim interface are computed for heavy braking and cornering maneuvers.
46
Seo, Jung Won, Byeong Choon Goo, Heung Chai Chung, Jae Boong Choi e Young Jin Kim. "The Effects of Residual Stress of Contact Fatigue Life for Railway Wheels". Key Engineering Materials 297-300 (novembre 2005): 115–21. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.115.
Testo completoAbstract (sommario):
Railway wheels and axles belong to the most critical components in railway vehicles. The service conditions of railway vehicles became more severe in recent years due to the increase of speed. Therefore, a more precise evaluation of railway wheel life and safety has been requested. Wheel/rail contact fatigue and thermal cracks due to braking are two major mechanisms of the railway wheel failure. One of the main sources of the contact zone failure is the residual stress. The residual stress on wheel is formed during the manufacturing process which includes a heat treatment, and then, is changed in the process of braking which results in wheel/rail contact stress and thermal stress. In this paper, an evaluation procedure for the contact fatigue life of railway wheel including residual stress is proposed. Also, the cyclic stress history for fatigue analysis is simulated by applying finite element analysis for the moving contact load. As a result, a fatigue life estimation methodology is proposed for railway wheels which includes the effects of residual stresses due to heat treatment, braking and repeated contact load, respectively.
47
Jiao, Jian, Shu Dong Meng, Qiang Jiao e Nan Li. "The Mechanical Response Analysis of the Airport Asphalt Pavement Considering Horizontal Load". Advanced Materials Research 645 (gennaio 2013): 471–75. http://dx.doi.org/10.4028/www.scientific.net/amr.645.471.
Testo completoAbstract (sommario):
In order to research the mechanical response of asphalt pavement under horizontal load which produced by the large aircraft braking process, large-scale finite element software is used in this paper. The model of main landing gear load is established to analyze the change of principal mechanics indexes of airfield pavement when the aircraft has different landing distance. The results show that: the horizontal load has a significant influence on the normal stress of landing direction, but the influence area is concentrated in the rear of the wheel. The horizontal load has more effect on horizontal shear stress and longitudinal shear stress, while has less effect on tensile stress of surface layer bottom, tensile tress of base course bottom and transverse shear stress. The tensile stress of surface layer will increase significantly when the braking distance is less than 2000m. Meanwhile, thickening surface layer could decrease the tensile stress and increase the fatigue lifetime apparently.
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Ignatyev, Pavel A., Stefan Ripka, Norbert Mueller, Stefan Torbruegge e Burkhard Wies. "Tire ABS-Braking Prediction with Lab Tests and Friction Simulations". Tire Science and Technology 43, n. 4 (1 ottobre 2015): 260–75. http://dx.doi.org/10.2346/tire.15.430401.
Testo completoAbstract (sommario):
ABSTRACT The invention and application of antilock braking systems (ABS) has resulted in a significant improvement of traffic safety and a reduction of stopping distance, especially on wet roads [1]. The reason for this success is rather clear: ABS is designed to steer the braking process in the most efficient way by keeping an optimal level of tire slip. At the same time, it must be clear that ABS uses braking forces generated in the tire footprint, and really good braking is possible only with high-performance tires. The best way to probe tire performance is to build tires and test them. This is, however, a long and an expensive procedure, so prediction of ABS performance based on results of some simple experiments is a very attractive supplement to the development process. Tire-braking performance is related to the friction of rubber on a surface. Relevant friction mechanisms can include adhesion, rubber hysteresis, and various kinds of viscous friction. All of these phenomena depend on the local sliding velocity, load, and temperature of tread rubber. Tire blocks pass the footprint area of a braking tire very rapidly, but their dynamics are indeed influenced by ABS. All of these aspects make the problem of ABS-braking prediction very intricate. In this publication, we present an approach for prediction of the ABS-braking performance. The approach links friction measurements conducted in laboratory to tire tests results. The friction of six specially designed compounds was measured on dry and wet surfaces using a high-speed linear friction test rig. Obtained experimental results are analyzed with the aid of rubber friction theory [2,3] involving both surface and rubber as input parameters. It is demonstrated that lab friction test procedures can be used for prediction of ABS wet braking performance.
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Klubnichkin, Vladislav, Aleksandr Kartashov, Georgiy Kotiev e Denis Druchinin. "RESEARCH OF BRAKING PROPERTIES OF WHEEL FORWARDER 8×8". Forestry Engineering Journal 11, n. 4 (31 gennaio 2022): 124–38. http://dx.doi.org/10.34220/issn.2222-7962/2021.4/11.
Testo completoAbstract (sommario):
The operating conditions of wheeled forwarders have been considered. The requirements for the efficiency of the braking system are described, as well as methods for testing the working and parking braking systems of wheeled forestry machines when operating on ups and downs of up to 50%. The most severe brake loading situations in terms of keeping the forwarder on a slope have been shown. A calculation scheme for determining the loads in the contact patch during the descent of a wheeled forwarder has been drawn up. The initial data necessary for calculating the braking system of the machine have been given. The results of calculations of reactions when the forwarder is located on a horizontal support surface and the calculation of reactions in the contact patch of the wheel during descent and ascent are given. The technical parameters of the braking system of the NAF TAP 7601 balancer axles used on the developed machine have been presented. The results of calculations of the braking properties of the forwarder in running order and at full weight on the descent (characterized by the parameters α = 40% and α = 50%, as well as on the ascent α = -50%) have been presented. The results of calculations of the required braking torque on the wheels of the machine, the maximum-realized braking torque for the adhesion of all wheels of the front and rear axles of the machine have been presented. The safety factor of braking mechanisms and the safety factor for adhesion have been given
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Chovnyuk, Yuriy, Petro Cherednichenko, Olga Ostapushchenko e Valeria Svintsitska. "DISCRETE-TO-CONTINUUM MODELS IN ANALYSIS AND OPTIMIZATION (MINIMIZATION) OF DYNAMIC LOADS IN ELASTIC ELEMENTS/CARRIER CABLES OF HOISTING MACHINERY USED IN URBAN PLANNING AND TRANSPORT TECHNOLIGIES (Part III)". Urban development and spatial planning, n. 78 (29 ottobre 2021): 544–57. http://dx.doi.org/10.32347/2076-815x.2021.78.544-557.
Testo completoAbstract (sommario):
The analysis dynamic loads in elastic elements (ropes) of hoisting mashines and cranes used in urban planning, loading and unloading operations and transport technologies was carried out. Discrete, continuous and discrete-continuous models of crane lifting mechanisms considered. In these models the elastic elements (ropes) are initially considered as elements that have elastic properties of the system with concentrated parameters. Therefore the rope in the lifting mechanism is taken into account as a certain rigidity spring. However, this approach is not correct for quite long ropes (more than 10 meters), in which wave processes can occur during lifting/lowering of loads. These processes can significally increase the dynamic loads − the so-called rope model as a system with distributed parameters. According to the authors of this work, the most correct approach is one that takes into account the discrete properties of the rope (more than 10 meters) itself. That is, the analysis of dynamic loads is carried out within a discrete-continuous model.
The work consists of several parts, in each of which the dynamic loads in the ropes within each of above starting/braking of the crane lifting mechanisms models are comprehensively and in detail considered. Also parameters of work processes at which the above loads become optimal in magnitude calculated (that is, take the minimum values for different ways of lifting cargo: a)“from the base” (“from the ground”), b)“from the weith”, as, incidentally, the coefficient of dynamism.