scholarly journals Impact of cranks displacement angle on the motion non-uniformity of roller forming unit with energy-balanced drive

2021 ◽  
pp. 141-155
Author(s):  
Viacheslav Loveikin ◽  
Kostiantyn Pochka ◽  
Mykola Prystailo ◽  
Maksym Balaka ◽  
Olha Pochka
Keyword(s):  
Differential Equation ◽  
Angular Velocity ◽  
Electric Motor ◽  
Steady Motion ◽  
Equation Of Motion ◽  
Start Up ◽  
Change Function ◽  
Displacement Angle ◽  
The Impact ◽  
Motion Mode

The impact of the cranks displacement angle on the motion non-uniformity is determined for three forming trolleys of a roller forming unit with an energy-balanced drive mechanism. At the same time, the specified unit is presented by a dynamic model with one freedom degree, where the extended coordinate is taken as the angular coordinate of the crank rotation. For such a model, a differential equation of motion is written, for solved which a numerical method was used. The inertia reduced moment of the whole unit, and the resistance forces moment, reduced to the crank rotation axis, to move of forming trolleys during the formation of products from building mixtures are determined, and also the nominal rated power of the electric motor was calculated, when solved a differential equation of motion. According to these data, asynchronous electric motor with a short-circuited rotor was chosen, for which a mechanical characteristic is constructed by the Kloss formula. Having solved the differential equation of motion with all defined characteristics, we obtain the change function of the crank angular velocity from start-up moment and during steady motion mode. After that, we calculated the time corresponding to the angular velocity value, and obtained the change function of the crank angular acceleration from start-up moment and during steady motion mode. The motion non-uniformity of the roller forming unit has been determined by the motion non-uniformity factor, the motion dynamism factor and the extended factor of motion assessment during steady motion mode. The impact of drive cranks displacement angle on the motion non-uniformity has been traced, as a result, the specified factors have the minimum values at cranks displacement on the angle Δφ=60°. The results may in the future are used to refine and improve the existing engineering methods for estimating the drive mechanisms of roller forming machines, both at design stages and in practical use.

scholarly journals DYNAMICS OF STARTING MACHINES

2018 ◽  
Vol 13 (4) ◽  
pp. 119-123
Author(s):  
Александр Мудров ◽  
Aleksandr Mudrov
Keyword(s):  
Composite Materials ◽  
Service Life ◽  
Electric Motor ◽  
Substantial Reduction ◽  
Steady Motion ◽  
Dynamic Loads ◽  
Elastic Coupling ◽  
Static Loads ◽  
Start Up ◽  
Machine Elements

The operation of any machine includes three periods of operation: start and acceleration, steady motion, braking and stopping. During periods of start-up and braking, large dynamic loads occur, adversely affecting the strength of machine elements and the overloading of the drive source. The purpose of the study is to determine the dynamic loads during the start-up of the machine and to find options for reducing them. The mathematical values of dynamic loads are determined by the example of a spatial mixer from rotating elements of the drive. It has been established that the dynamic moments from the rotating elements of the drive are several times greater than those from static loads. Practical methods are shown to reduce these loads using an elastic coupling, removing the coupling from the structure, manufacturing it from composite materials, and increasing the start-up time of the electric motor. The significance of the results obtained for machines using transmissions through couplings consists in a substantial reduction of the influence of dynamic loads during start-up on the elements and source of the drive and an increase in the service life and productivity of the machines as a whole.

scholarly journals TRANSITION PROCESSES IN ELECTROMECHANICAL TRANSMISSION WITH A RESILIENT-ELASTIC COUPLING

2020 ◽  
Vol 1 (154) ◽  
pp. 44-49
Author(s):  
В. Kindratskyy ◽  
R. Litvin
Keyword(s):  
Electric Motor ◽  
Combustion Engine ◽  
Model Simulation ◽  
Steady Motion ◽  
Peak Torque ◽  
Elastic Coupling ◽  
Driving Mode ◽  
Start Up ◽  
The Moment ◽  
Moment Of Resistance

Driving systems for hybrid cars and electric vehicles equipped with electric motors have different structures and characteristics. In the vast majority of hybrids, depending on the driving mode, the torque on the wheels of the car can be generated separately by both the internal combustion engine and the electric motor, or by working together. Based on the research results it is established that at the moment of starting the electric motor, the torque in the transmission sections steeply increases to 17 N•m, and for about 1 s decreases to the value of 7 N•m. In the period from 4 to 5.5 s, the torque increases to 14 N•m, which is explained by the overcoming of the inertial load during acceleration of the driven weight, and rapidly decreases to the value of 4 N•m, which corresponds to the consolidated moment of resistance to movement. The electromagnetic moment of electric motor thus also increases steeply in the initial stage of starting the motor up to 66 N•m and after 1 s decreases to the value of 15 N•m. After 5.5 s there is an increase in the moment to the value of 66 N•m and after 5.8 s it stabilizes and ranges from -6 to 22 N•m. In turn, the calculations for an electromechanical transmission equipped with a resilient-elastic coupling showed that the maximum torque in its sections Т2 during the start-up period decreased to 9 N•m, and the acceleration time to a steady turning velocity of the driven weight slightly increased to 6.8 s. The torque that occurs in the transmission sections during acceleration to a steady velocity does not exceed 13 N•m. The torque in the resilient-elastic coupling sections during the start-up period does not exceed 10 N•m, and its value, upon reaching the steady motion of the driven weight, is slightly less than 5 N•m. Peak torque in the resilient-elastic coupling sections Т1 reaches 22 N•m, while in the transmission Т2 it is 13 N•m, which confirms the efficiency of resilient-elastic coupling operation. Thus, the use of resilient-elastic coupling in an electromechanical transmission can reduce the amplitude of the torque in the drive sections during the start-up period by about 1.9 times, as compared to the amplitude of the torque without resilient-elastic coupling, and reduce the peak torque of the transmission sections by 1.7 times. Keywords: asynchronous electric motor, dynamic model, mathematical model, simulation model, torque.

The Behaviour of the Impact Damper

1965 ◽  
Vol 180 (1) ◽  
pp. 895-906 ◽  
Author(s):  
M. M. Sadek
Keyword(s):  
Differential Equation ◽  
Impact Force ◽  
Equation Of Motion ◽  
Dynamic Equations ◽  
Vibrational Amplitude ◽  
Time Curve ◽  
Impact Damper ◽  
Rectangular Shape ◽  
Force Time ◽  
The Impact

In this investigation a theory is developed relating to the behaviour of the impact damper. The analysis is based on the assumptions that (1) two un-equispaced impacts per cycle occur in the steady state, and (2) the impact force-time curve is of rectangular shape and of infinitesimal duration. Fourier series are used to represent the impact cycle and the differential equation of motion is derived. This is solved using the dynamic equations of impact to determine the boundary conditions. Three equations are developed to determine the variation of impulse, phase angle and vibrational amplitude with the change of the damper parameters. Resonance curves are obtained and the theory is examined experimentally. The regions of validity of the above assumptions are studied both theoretically and experimentally. Non-linearity in the behaviour of this damper is very clear, especially in the range of its optimum behaviour. Two design curves are developed which can be used to determine the damper parameters necessary for a certain amplitude reduction.

scholarly journals АНАЛІТИЧНЕ ДОСЛІДЖЕННЯ ДИНАМІКИ ТИПОВИХ КУЛІСНИХ МЕХАНІЗМІВ ТЕХНОЛОГІЧНИХ МАШИН ЛЕГКОЇ ПРОМИСЛОВОСТІ

2018 ◽  
Vol 122 (3) ◽  
pp. 9-18
Author(s):  
В. М. Дворжак
Keyword(s):  
Differential Equation ◽  
Computer Simulation ◽  
Angular Velocity ◽  
Equation Of Motion ◽  
Analytical Investigation ◽  
Light Industry ◽  
Sewing Machine ◽  
Characteristic Points ◽  
Crank Mechanism ◽  
Angle Of Rotation

Improving methods of designing technological machines mechanisms of light industry in CAD-programs. The analytical method of vector transformation of coordinates for calculation of typical mechanisms of technological machines and a numerical method for solving differential equations are used. Mathematical models describing the functions of the position of the moving links and the characteristic points of the multi-link mechanism of the thread take-up mechanism for the sewing machine and the dynamics of its operation are obtained. Schematic modeling of the mechanism in the Mathcad program was performed. The graphs of the dependence of the angular velocity and acceleration on time and on the angle of rotation of the crank mechanism. The algorithm of numerical and analytical investigation of the dynamics of the flat six-link articulated mechanism of the thread take-up of the sewing machine is proposed on the basis of the numerical solution of the differential equation of motion of the mechanism and a computer simulation of the mechanism in the program Mathcad. Practical Value is to use the results of research in kinematic and dynamic study of the target sewing machine mechanisms.

Finite difference code for velocity and surface traction of a Fluid between Two Eccentric Spheres

2015 ◽  
Vol 11 (1) ◽  
pp. 2960-2971
Author(s):  
M.Abdel Wahab
Keyword(s):  
Velocity Field ◽  
Angular Velocity ◽  
Finite Difference ◽  
Numerical Study ◽  
Outer Sphere ◽  
Equation Of Motion ◽  
Annular Region ◽  
Surface Traction ◽  
Angular Velocities ◽  
Axis Passing

The Numerical study of the flow of a fluid in the annular region between two eccentric sphere susing PHP Code isinvestigated. This flow is created by considering the inner sphere to rotate with angular velocity 1  and the outer sphererotate with angular velocity 2  about the axis passing through their centers, the z-axis, using the three dimensionalBispherical coordinates (, ,) .The velocity field of fluid is determined by solving equation of motion using PHP Codeat different cases of angular velocities of inner and outer sphere. Also Finite difference code is used to calculate surfacetractions at outer sphere.

Clients' Expectations on Audit Judgments: A Note

2004 ◽  
Vol 16 (1) ◽  
pp. 63-74 ◽  
Author(s):  
Venkataraman M. Iyer ◽  
Dasaratha V. Rama
Keyword(s):  
Audit Quality ◽  
Financial Statements ◽  
Early Years ◽  
Relative Power ◽  
Client Perceptions ◽  
Audit Firm ◽  
Auditor Tenure ◽  
Start Up ◽  
Nonaudit Services ◽  
The Impact

Audited financial statements can be viewed as the product of negotiations between a company's management and its auditor. Relative power of these two parties is a major factor that determines the outcome of the negotiation. This study examines the impact of auditor tenure, importance of a client to an audit partner, nonaudit purchases, and prior audit firm experience of client personnel on client perceptions about their ability to persuade the auditor in the context of an accounting disagreement. We obtained responses to a survey from 124 CPAs in industry who are employed as CEOs, CFOs, controllers, or treasurers. Our results indicate that respondents from companies with short auditor tenures were somewhat more likely to indicate that they could persuade the auditor to accept their (client's) position in case of a disagreement. This finding is consistent with the argument that auditors are susceptible to influence in the early years as they are still in the process of recouping start-up costs, but is not consistent with concerns expressed by legislators and others that long auditor tenures will adversely affect audit quality. Respondents who believed their business was more important for the audit partner were also more likely to believe that they could persuade the auditor. However, the purchase of nonaudit services and prior audit experience were not related to client's perceptions about their ability to persuade the auditor.

scholarly journals Time-jerk optimal trajectory planning of hydraulic robotic excavator

2021 ◽  
Vol 13 (7) ◽  
pp. 168781402110346
Author(s):  
Yunyue Zhang ◽  
Zhiyi Sun ◽  
Qianlai Sun ◽  
Yin Wang ◽  
Xiaosong Li ◽  
...  
Keyword(s):  
Angular Velocity ◽  
Trajectory Planning ◽  
Optimal Trajectory ◽  
High Efficiency ◽  
Optimal Solution ◽  
Optimal Time ◽  
Target Point ◽  
Robotic Excavator ◽  
The Impact ◽  
Optimal Trajectory Planning

Due to the fact that intelligent algorithms such as Particle Swarm Optimization (PSO) and Differential Evolution (DE) are susceptible to local optima and the efficiency of solving an optimal solution is low when solving the optimal trajectory, this paper uses the Sequential Quadratic Programming (SQP) algorithm for the optimal trajectory planning of a hydraulic robotic excavator. To achieve high efficiency and stationarity during the operation of the hydraulic robotic excavator, the trade-off between the time and jerk is considered. Cubic splines were used to interpolate in joint space, and the optimal time-jerk trajectory was obtained using the SQP with joint angular velocity, angular acceleration, and jerk as constraints. The optimal angle curves of each joint were obtained, and the optimal time-jerk trajectory planning of the excavator was realized. Experimental results show that the SQP method under the same weight is more efficient in solving the optimal solution and the optimal excavating trajectory is smoother, and each joint can reach the target point with smaller angular velocity, and acceleration change, which avoids the impact of each joint during operation and conserves working time. Finally, the excavator autonomous operation becomes more stable and efficient.

scholarly journals The influence of cronyism on entrepreneurial resource acquisition

2021 ◽  
Author(s):  
Junfan Yu ◽  
Saskia De Klerk ◽  
Michael Hess
Keyword(s):  
Community Involvement ◽  
Private Property ◽  
Resource Acquisition ◽  
Property Development ◽  
Network Utilization ◽  
Start Up ◽  
Entrepreneurial Strategies ◽  
Staged Model ◽  
The Impact

AbstractThis research focuses on how entrepreneurs utilize cronyism to acquire resources. A case study method allowed us to explore three firms in the private property development industry in China. These firms uniquely cultivated cronyism and achieved distinctly different outcomes. Our findings highlight Chinese entrepreneurs in start-up ventures and later-stage enterprises employ cronyism. The underlying rationale for using cronyism have common and heterogeneous motivations. The similarity and distinguishing rationale also apply to the impact of cronyism. We also find two contingency working mechanisms for cronyism: entrepreneurial characteristics and a staged model for cronyism. With the firm’s growth, cronyism remains important, but firms with more community involvement outperform others. This research contributes to the theory on strategic network utilization for resource acquisition during entrepreneurial development stages. We investigate how entrepreneurial strategies can assist in adapting to the “rules of the game” while utilizing resources within the set contextual constraints.

The Numerical Methods of Peridynamics Theory Used in Failure Analysis of Materials

2014 ◽  
Vol 1030-1032 ◽  
pp. 223-227
Author(s):  
Lin Fan ◽  
Song Rong Qian ◽  
Teng Fei Ma
Keyword(s):  
Differential Equation ◽  
Integral Equation ◽  
Numerical Integration ◽  
Integration Method ◽  
Equation Of Motion ◽  
Numerical Integration Method ◽  
Volume Integral ◽  
Volume Integral Equation ◽  
Method Of Molecular Dynamics ◽  
Classic Theory

In order to analysis the force situation of the material which is discontinuity,we can used the new theory called peridynamics to slove it.Peridynamics theory is a new method of molecular dynamics that develops very quickly.Peridynamics theory used the volume integral equation to constructed the model,used the volume integral equation to calculated the PD force in the horizon.So It doesn’t need to assumed the material’s continuity which must assumed that use partial differential equation to formulates the equation of motion. Destruction and the expend of crack which have been included in the peridynamics’ equation of motion.Do not need other additional conditions.In this paper,we introduce the peridynamics theory modeling method and introduce the relations between peridynamics and classic theory of mechanics.We also introduce the numerical integration method of peridynamics.Finally implementation the numerical integration in prototype microelastic brittle material.Through these work to show the advantage of peridynamics to analysis the force situation of the material.

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