1. Influence of feeding speed on concrete pipe forming
In the production process of concrete pipe, the bell mouth is formed by vibration, and the main part of the pipe is mainly formed by radial extrusion. In different forming stages, the stress-strain characteristics are different. Therefore, it is necessary to study the matching characteristics of feeding speed, vibration intensity and main shaft pipe making speed.
Because different water cement ratio and aggregate particle diameter have a great impact on the physical properties of concrete and affect the whole process of concrete pipe forming, the concrete shaping can be calculated by using the finite element software LS-DYNA, and the influence of parameter changes such as stone porosity and mortar pull-out coefficient on the model can be considered. Under the condition of certain water cement ratio, the influence of aggregate on the water volume of concrete mixing is analyzed to determine the amount of concrete. In addition, by changing the one-way rotation of the extrusion head of the existing vertical cement pipe making machine into two-way movement, its side effects on the reinforcement skeleton can be greatly reduced, making the design position of the reinforcement easier to locate. The inner wall of the pipe making machine uses the die wall composed of aluminum magnesium alloy and steel plate to replace the traditional steel inner wall, which can also greatly improve the smoothness of the pipe wall.
2. Influence of rebound action of reinforcement framework on pipe making quality
During the processing of concrete pipes with different diameters, the feeding speed, the exciting force of vibration forming of socket, the applied force during radial extrusion forming and the rising speed of extrusion roller will affect the stress of reinforcement skeleton, which will lead to the resilience of reinforcement skeleton and affect the processing quality of concrete pipes.
In the process of vertical radial extrusion, due to the use of vertical pipe making, small pipe diameter and large height (up to more than 3.5m), the settlement and deformation of concrete pipe will inevitably occur under the action of gravity. With the change of time, the settlement deformation gradually accumulates, so that the concrete compactness along the axial direction of the pipe body is not completely consistent. In addition, the extrusion time, the rising speed of the extrusion roll and the extrusion force will also affect the pipe quality. On the basis of considering friction factors, the physical model of extrusion molding is established to analyze the stress-strain law of reinforcement skeleton under different spindle speed, rising speed and feeding speed. By optimizing the internal reinforcement framework of reinforced concrete pipe, the longitudinal and circumferential reinforcement of reinforcement framework are thickened. At the same time, the positioning accuracy of the vertical radial extrusion pipe machine is improved, and the anti torsion positioning device of the reinforcement skeleton is improved, so that the vertical radial extrusion pipe machine can operate more stably.
3. Socket collapse
The bell mouth part of the formed pipe is not firm, and the bell mouth is easy to collapse during storage, mainly because the formed pipe is extruded instantaneously during the pipe making process, and the forming time is short, only 2 ~ 3min, so the concrete can not be formed tightly and tightly, resulting in bell mouth collapse.
By analyzing the mechanism and process of bell mouth vibration forming, the topological relationship of vibration is established. The basic form of dynamic equation of axial vibration is established by Newton Euler method. The active vibration excitation is input into the motion equation according to random wave. The dynamic history of bell mouth element is analyzed by process analysis method, and the axial displacement response and acceleration response of bell mouth element are obtained. The finite element model of bell element forming is established by LS-DYNA software, and the effects of concrete parameters, working amplitude and vibration frequency on Bell element forming are considered. Figure 1 is the schematic diagram of bell mouth forming process. The bell mouth is mainly formed by left and right vibration, supplemented by up and down vibration. The most reasonable vibration frequency and direction can be found by simulating the running state of the bell part in production.
Post time: Sep-29-2021