Experimental analysis of the effect of bed-load movement on flow hydraulic characteristics

In this study, the effect of bed-load movement on mean flow characteristics was evaluated in two rigid rectangular flumes. The experiments consisted of creating flow conditions carrying sediments with mean diameters of D50 = 0.5, 0.6, and 2.84 mm over both smooth and rough beds. Various sediment concentrations were injected at the upstream end of the flume at non-deposit injection rates to study the effect of various concentrations on flow resistance. The effect of sediment movement on flow resistance was examined by comparing the results with those of clear water flows (without sediment injection on both smooth and rough beds). The results showed that the sediment transport in maximum injection rate may increase the friction factor up to 50 and 58 percent for smooth bed, and up to about 75 and 80 percent in rough bed with mean diameter of 0.5 and 0.6 mm. Besides, for D50 = 2.84 mm, the friction factor decreased in smooth bed and increased up to 50 percent in rough bed. In general, it can be concluded that bed-load transport can be increased by the flow friction factor. The results also showed that bed-loads may decrease the average velocity and increase shear velocity with extraction of momentum from the flow, which both of mentioned factors may increase the flow friction factor. Raising the bed-load concentration in the flow may increase the elevation of the friction factor, approaching a constant value after reaching to the aggregation threshold and generation of bed forms.

Evaluating the energy storage capabilities of forklift actuator

Energy saving in construction and logistics is a topical and open issue today. Forklifts are one of the main self-propelled means of mechanization of warehouses, in which the effect of energy recovery can be applied. This is due to the peculiarity of such systems that operate in overclocking and braking modes. The purpose of this work is to study the energy consumption in the drive system of the loader based on the analysis of the sequence diagram of its operation for given sections of movement. Methodology. The equation of traction balance of a wheeled machine is used to estimate energy consumption at given sections of the load movement. Determination of the kinematic parameters of the loader system with the load is determined from the condition of maximum traction. Results. The mass characteristics of the system, speed of movement, characteristics of the road surface contribute to the formation of the energy return by the system of the loader in the process of its braking. Increasing operating speeds will have a positive effect on energy savings in energy storage systems. Analysis of energy consumption during the operation of the loader shows that in the process of its operation you can effectively store from 30 to 70% of energy. Originality. This study uses an engineering assessment approach that will be useful for practical applications in the design of such systems. Practical value. In this study, the sequence diagram of the energy consumption of a forklift when working with loads of 2000 kg, 1000 kg and 500 kg is essential. The sequence diagram method is simple and can therefore be easily implemented in forklift control systems to enable energy recovery systems.

Mechanical and mathematical modeling of the load movement on the thread wound on cylindrical drum with movable axis

A mechanical system, where the load in the form of material point is suspended on inextensible thread screwed on the rotating cylindrical drum, but the drum is connected to the boom rotating around fixed horizontal axis is considered. Using the Lagrange equation of the second kind, a mathematical model of the motion of the mechanical system is obtained. The system has three degrees of freedom, two of which are cylindrical. The investigation of the system motion is carried out using computer technology. As a result, the dependences of linear and angular coordinates and velocities in time at different values of the output data for two main modes of the system operation, namely – under the conditions of lifting and lowering the load are obtained. Appropriate graphs are constructed, including the trajectories of the cargo motion. The mathematical model takes into account nonlinearities of the system and allows you to find the amount of tension of the hoisting rope at any time. The analysis showed that vertical oscillations occur twice as fast as horizontal ones. The phase portrait of the generalized coordinate (angle of the rope with the vertical axis) is the focus, which is untwisted when lifting due to nonlinearity in the system, and when the load moves down, the focus, which twists and approaches the mathematical pendulum is obtained. The obtained results can be used in modeling of controlled pendulum motions for different mechanical systems. The methodology and program are recommended to the students and graduate students in terms of learning the principles of construction and analysis of complex nonlinear dynamical systems.

Analysis of Strain-gage Records from a Static Loading Test on a CFA Pile

A static test was performed on a 610-mm diameter, 10 m long CFA pile installed through 3 m of clay and sand and into a thick deposit of lacustrine clay. The loading procedure included prolonged load-holding and an unloading-reloading event, which adversely affected the interpretations of the strain records and demonstrated the inadvisability of not performing a test with equal load-increments and equal load-holding durations and avoiding all unloading-reloading sequences. The pile was strain-gage instrumented at three levels and the recorded strains were used to calculate the pile axial stiffness and determine the load distributions for the applied load. Back-calculations using effective stress analysis were fitted to strain-gage determined load distributions and were then used in simulating the measured pile-head load-movement of the test pile.

Analysis of starting in horse head system at optimal jerking mode of movement

This article presents the results of an analytical study of the kinematic and power parameters of the movement of the articulated boom system of the crane at the beginning of the movement. The study was carried out during the acceleration of the electric motor of the mechanism for changing the departure from the state of rest to the rotation frequency corresponding to the nominal operating speed of the load movement. In this case, the start of the electric motor occurs, provided that the entire boom system moves along with the load according to the law of jerking optimization. The using of this regularity allows you to completely smooth out the swinging of the load at the beginning of the movement. In addition, towards the end of the acceleration, the same speeds and accelerations are provided between the end point of the crane trunk and the load. This makes it possible to ensure high smoothness of movement of the boom system, and to avoid the load swinging after the rotor of the electric motor reaches the rated speed. Also, a study of static, dynamic and total force in the drive gear rack was carried out. These studies were carried out at different duration of the process of starting the electric motor according to the law of jerking optimization. This made it possible to establish the dependence of the studied kinematic and power parameters on the duration of the transient process. Based on the above, recommendations have been developed for choosing the duration of the acceleration of the electric motor in the mechanism for changing the departure. During of the study, graphs of changes in the studied parameters of the boom system in time were built. Graphical dependencies were obtained with the most acceptable duration of the acceleration mode from the point of view of reducing the dynamic loads on the links of the boom system, improving the technological process of the crane and its ergonomics.

Study on the influence of ecological vegetation revetment on river flow and sediment environment

This paper studied the influence of vegetation cover on the river water flow environment and on sediment suspended load movement environment, closely combining the development and construction of new ecological water conservancy projects such as ecological embankments and ecological wetlands with ecological vegetation revetment cultivated on river bank slopes. The glass flume experiment was carried out in the vegetation-water flow-sediment environment. In the experiment, natural straight holly in the early growth stage was selected as the experimental vegetation, and erect type vegetation with uniform distribution of the upper and lower branches and leaves was simulated, and a total of 14 experimental groups were set in different combinations with fixed bed, movable bed, submerged and non-submerged conditions. The measured data of flow quantity, flow velocity and suspended load concentration were achieved in the experiment. The experimental results show that: (1) as to the influence of vegetation on the water flow environment, the vegetation canopy density directly affects the turbulent environment of the water flow, and the greater the density, the greater the disturbance to the water flow environment, and the flow velocity near the canopy will be decreased sharply; (2) in the fixed bed, under submerged conditions, the maximum turbulence intensity appears near z/h = 0.6; under non-submerged conditions, the turbulence intensity near the water surface is largest. In the movable bed, under submerged conditions, the maximum turbulence intensity reaches the maximum in the top and upper locations of the top of the plant, and the turbulence intensity reaches the maximum at the top of the plant under non-submerged conditions. (3) In terms of the influence of vegetation on the sediment suspended load movement environment, the concentration of suspended sediment decreases with the increase of plant height, the sediment content in the tail of the plant belt is reduced to some degree. When the relative water depth is z/h > 0.5, almost no suspended sediment exists. And the sediment-retaining effect under non-submerged conditions is better than that under submerged conditions.

Initial testing of students as part of the training method for the skidder operator

Разработана методика первичного тестирования обучающихся на предмет приспособленности к работе с управляемым манипулятором по профессии рабочего 14269 Машинист трелевочной машины . Апробация методики проведена с использованием учебного стенда СГУ-ГПМ на базе Лаборатории сервиса лесных машин ФГБОУ ВО Поволжский государственный технологический университет . Приведенный анализ результатов исследования включает данные времени выполнения цикла перемещения груза для группы обучающихся. Установлено влияние количества повторений цикла работы СГУ-ГПМ на эффективность взаимодействия операторов с перегрузочным оборудованием. Доказано, что в процессе многократного повторения цикла обучающиеся усваивают основные навыки работы с манипулятором и запоминают функционал органов управления, как следствие сокращается время цикла и растет стабильность результатов за счет снижения разброса времени цикла. После стабилизации результатов на учебном стенде СГУ-ГПМ обучающийся получает устойчивый навык работы с органами управления и понимает особенности кинематики шарнирно-сочлененных гидравлических перегрузочных манипуляторов, что позволяет перейти к дальнейшим этапам обучения. A methodology was developed for the primary testing of students for fitness for work with an operated manipulator by worker profession 14269 Skidder operator . The methodology was tested using the training stand on the basis of the Forest Machines Service Laboratory of the Federal State Budgetary Educational Institution of Higher Education Volga State University of Technology . The analysis of the study results includes data on the execution time of the load movement cycle for a group of students. The influence of number of the training stand cycling on the efficiency of interaction between operators and handling equipment was established. It is proved that in the process of repeated cycling, students learn the basic skills of working with the manipulator and memorize the functionality of the controls, as a result, the cycle time is reduced and the stability of the results is increased by reducing the variation in cycle time. After stabilizing the results at the training stand, the student gains a steady skill in working with control devices and understands the kinematics of the articulated hydraulic overload manipulators, which allows us to proceed to the further stages of training.