Controlling Uniformity of Quality of Inner Surfaces of Bends
Posted: 09/24/2022 10:54:08 Hits: 13
1.1 Introduction
With the rapid development of the equipment manufacturing industry, not only technological innovation is required, but also higher requirements are put forward for the size, shape, properties of materials, and quality of surfaces. As the lifeline of equipment, pipeline systems can improve the stability and reliability of equipment by reducing its failure rate. At present, most piping systems consist of alloy bends with small space and light weights. When the pipe is bent and formed, surface defects such as wrinkles and micro-cracks will occur at the bending part due to the limitation of processing technology. Compared with the straight pipe, the inner surface quality of the bending part is more obvious. Defects on the inner surface of the pipeline will lead to a surge when it transports oil, liquid, gas and other media, and the residual liquid in the pit will aggravate the corrosion of the inner surface of the pipeline and shorten the service life of the pipeline system. Therefore, it is particularly important to realize the control of uniformity of the inner surface of the bend.
In the process of continuous development of the high-precision technology industry, changes in its use requirements have prompted the emergence of various cross-sectional shapes and different sizes of bends. Different types of bends can also play an important role in aviation, shipbuilding, automobile manufacturing and other fields that have stricter requirements for use. The actual application of bends is shown in Figure 1.1.
Figure 1.1 Applications of bends
The aero-engine hydraulic piping system has hundreds of hydraulic pipes and is very sensitive to gaps and cracks on the surface. Hydraulic pipes are usually designed as space bends with different curvature radii due to the limitation of space and weights of pipelines. After preliminary research, it was found that the failure caused by fatigue of the hydraulic pipe was mainly caused by the liquid impacting the inner surface of the bend, and the micro-cracks were extended and ruptured. The stress concentrates at the pipe hoop and rupture due to the vibration of the pipeline caused by the uneven quality of the inner surface of the bend, as shown in Figure 1.2.
Figure 1.2 Hydraulic pipes and typical failure cases
In marine engineering, most piping systems consist of bends with different curvatures. due to the uneven surfaces such as wrinkles and micro-cracks on the inner surface after bending, the compressive strength of the pipeline is inconsistent, and the partial stress is relatively concentrated. Crack propagation or perforation rupture will happen due to the instability of media transported by the pipeline, and even cause pollution to the marine environment due to leakages of pipelines. Therefore, to reduce the energy loss of the fluid in the pipeline and the scouring of the pipeline, it is necessary to strictly control the inner surface quality of the bend.
As an indispensable part of modern internal combustion engine powered vehicles, the performance of the exhaust system determines the exhaust loss and pollutant emission of the engine. The airflow is prone to eddy current oscillation at the bend due to surface defects such as wrinkle waves on the inner surface of the bend in the exhaust system, which cannot guarantee the dynamic balance inside the pipeline, resulting in unstable working states of engines. As a result, the gasoline cannot be fully burned, and the accumulation of sediment on the inner wall of the bend will increase, and the long-term vicious circle will affect the working efficiency and service life of the engine. At present, how to improve the quality uniformity of the inner surface of the bend in the exhaust system is the key technology to solve the energy saving and purification of automobiles.
The process of controlling the uniformity of the inner surface quality of the bend obtained after the pipe is machined and bent has always been a big challenge for precision machining. Some scientific researchers at home and abroad have also been exploring the quality control process of the inner surface of the bend. The conventional machining method for processing the inner surface of the bend cannot realize its quality control. Most of the bends are cut along the axis, polished by hand, and then restored by welding. The process is cumbersome and the workload is great. Therefore, to ensure the reliability of the service of the bend and improve the quality of the inner surface of the bend, it is necessary to grind the inner surface of the bend to remove defects such as micro-cracks and wrinkles on the inner surface and ensure the quality of the surface. This problem also involves space bends in the fields of nuclear power and nuclear submarines.
With the rapid development of the equipment manufacturing industry, not only technological innovation is required, but also higher requirements are put forward for the size, shape, properties of materials, and quality of surfaces. As the lifeline of equipment, pipeline systems can improve the stability and reliability of equipment by reducing its failure rate. At present, most piping systems consist of alloy bends with small space and light weights. When the pipe is bent and formed, surface defects such as wrinkles and micro-cracks will occur at the bending part due to the limitation of processing technology. Compared with the straight pipe, the inner surface quality of the bending part is more obvious. Defects on the inner surface of the pipeline will lead to a surge when it transports oil, liquid, gas and other media, and the residual liquid in the pit will aggravate the corrosion of the inner surface of the pipeline and shorten the service life of the pipeline system. Therefore, it is particularly important to realize the control of uniformity of the inner surface of the bend.
In the process of continuous development of the high-precision technology industry, changes in its use requirements have prompted the emergence of various cross-sectional shapes and different sizes of bends. Different types of bends can also play an important role in aviation, shipbuilding, automobile manufacturing and other fields that have stricter requirements for use. The actual application of bends is shown in Figure 1.1.
Figure 1.1 Applications of bends
The aero-engine hydraulic piping system has hundreds of hydraulic pipes and is very sensitive to gaps and cracks on the surface. Hydraulic pipes are usually designed as space bends with different curvature radii due to the limitation of space and weights of pipelines. After preliminary research, it was found that the failure caused by fatigue of the hydraulic pipe was mainly caused by the liquid impacting the inner surface of the bend, and the micro-cracks were extended and ruptured. The stress concentrates at the pipe hoop and rupture due to the vibration of the pipeline caused by the uneven quality of the inner surface of the bend, as shown in Figure 1.2.
Figure 1.2 Hydraulic pipes and typical failure cases
In marine engineering, most piping systems consist of bends with different curvatures. due to the uneven surfaces such as wrinkles and micro-cracks on the inner surface after bending, the compressive strength of the pipeline is inconsistent, and the partial stress is relatively concentrated. Crack propagation or perforation rupture will happen due to the instability of media transported by the pipeline, and even cause pollution to the marine environment due to leakages of pipelines. Therefore, to reduce the energy loss of the fluid in the pipeline and the scouring of the pipeline, it is necessary to strictly control the inner surface quality of the bend.
As an indispensable part of modern internal combustion engine powered vehicles, the performance of the exhaust system determines the exhaust loss and pollutant emission of the engine. The airflow is prone to eddy current oscillation at the bend due to surface defects such as wrinkle waves on the inner surface of the bend in the exhaust system, which cannot guarantee the dynamic balance inside the pipeline, resulting in unstable working states of engines. As a result, the gasoline cannot be fully burned, and the accumulation of sediment on the inner wall of the bend will increase, and the long-term vicious circle will affect the working efficiency and service life of the engine. At present, how to improve the quality uniformity of the inner surface of the bend in the exhaust system is the key technology to solve the energy saving and purification of automobiles.
The process of controlling the uniformity of the inner surface quality of the bend obtained after the pipe is machined and bent has always been a big challenge for precision machining. Some scientific researchers at home and abroad have also been exploring the quality control process of the inner surface of the bend. The conventional machining method for processing the inner surface of the bend cannot realize its quality control. Most of the bends are cut along the axis, polished by hand, and then restored by welding. The process is cumbersome and the workload is great. Therefore, to ensure the reliability of the service of the bend and improve the quality of the inner surface of the bend, it is necessary to grind the inner surface of the bend to remove defects such as micro-cracks and wrinkles on the inner surface and ensure the quality of the surface. This problem also involves space bends in the fields of nuclear power and nuclear submarines.
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