A Composite Transformer-Based Multi-Stage Defect Detection Architecture for Sewer Pipes

Urban sewer pipes are a vital infrastructure in modern cities,and their defects must be detected in time to prevent potential malfunctioning.In recent years,to relieve the manual efforts by human experts,models based on deep learning have been introduced to automatically identify potential defects.However,these models are insufficient in terms of dataset complexity,model versatility and performance.Our work addresses these issues with amulti-stage defect detection architecture using a composite backbone Swin Transformer.Themodel based on this architecture is trained using a more comprehensive dataset containingmore classes of defects.By ablation studies on the modules of combined backbone Swin Transformer,multi-stage detector,test-time data augmentation and model fusion,it is revealed that they all contribute to the improvement of detection accuracy from different aspects.The model incorporating all these modules achieves the mean Average Precision(mAP)of 78.6% at an Intersection over Union(IoU)threshold of 0.5.This represents an improvement of 14.1% over the ResNet50 Faster Region-based Convolutional Neural Network(R-CNN)model and a 6.7% improvement over You Only Look Once version 6(YOLOv6)-large,the highest in the YOLO methods.In addition,for other defect detection models for sewer pipes,although direct comparison with themis infeasible due to the unavailability of their private datasets,our results are obtained from a more comprehensive dataset and have superior generalization capabilities.

Analysis of Heat Transfer Performance of Oscillating Heat Pipes Based on a Central Composite Design

Oscillating heat pipes (OHPs) are very promising cooling devices. Their heat transfer performance is af- fected by many factors, and the form of the relationship between the performance and the factors is complex and non-linear. In this paper, the effects of charging ratio, inclination angle, and heat input and their interaction effects on heat transfer performance of a looped copper-water OHP are analyzed. First, suppose that the relationship between the response and the variables approximates a second-order model. And use the central composite design to arrange the ex- periment. Then, the method of least squares is used to estimate the parameters in the second-order model. Finally, multi- variate variance analysis is used to analyze the model. The results show that the assumption is right, that is to say, the re- lationship is well modeled by a second-order function. Among the three main effect variables, the effect of inclination angle is the most significant, but their interaction effects are not significant. In the range of the considered factors, both the optimum charging ratio and the optimum inclination angle increase as the heating water flow rate increases.

A Comparative Study on the Post-Buckling Behavior of Reinforced Thermoplastic Pipes(RTPs)Under External Pressure Considering Progressive Failure

The collapse pressure is a key parameter when RTPs are applied in harsh deep-water environments.To investigate the collapse of RTPs,numerical simulations and hydrostatic pressure tests are conducted.For the numerical simulations,the eigenvalue analysis and Riks analysis are combined,in which the Hashin failure criterion and fracture energy stiffness degradation model are used to simulate the progressive failure of composites,and the“infinite”boundary conditions are applied to eliminate the boundary effects.As for the hydrostatic pressure tests,RTP specimens were placed in a hydrostatic chamber after filled with water.It has been observed that the cross-section of the middle part collapses when it reaches the maximum pressure.The collapse pressure obtained from the numerical simulations agrees well with that in the experiment.Meanwhile,the applicability of NASA SP-8007 formula on the collapse pressure prediction was also discussed.It has a relatively greater difference because of the ignorance of the progressive failure of composites.For the parametric study,it is found that RTPs have much higher first-ply-failure pressure when the winding angles are between 50°and 70°.Besides,the effect of debonding and initial ovality,and the contribution of the liner and coating are also discussed.

Discussion on New Evaluation Technology of Non-Metallic Composite Continuous Pipe for Oil and Gas Field

In view of the serious lack and lag of the test and evaluation technology of non-metallic composite continuous pipe, and focusing on the characteristics of the application of non-metallic composite continuous pipe in oil field, this paper discusses a series of new full-scale test and evaluation technologies for accurately evaluating the product quality and practical application performance of non-metallic composite continuous pipe, which effectively solves the major technical problem that the new products of non-metallic pipe cannot be accurately evaluated. Based on the characteristics of the application of non-metallic composite continuous pipe in oil field, a series of new full-scale test evaluation technologies which can accurately evaluate the product quality and practical application performance of non-metallic pipe are designed through a large number of tests. The test and evaluation technology can accurately evaluate the key performance of high and low pressure cycle, high and low temperature cycle, gas permeability resistance, minimum bending radius etc. It provides a scientific evaluation basis for the standardized application of non-metallic continuous pipe and a reliable quality control method for the selection of products in oil field.

The Designation Method of Bend Forming Dies for Aluminum Tube of PE-Al-PE Composite Pipe

The PE-Al-PE composite pipe is a multiplayer pipe t hat is composed of PE (polyethylene) and Aluminum. Al is inlayed the inner PE la yer and the outer PE layer. In the producing technological process of this kind of pipe the bend forming of Al belt to tube is very important. It is the bend fo rming dies that are used in the process of producing PE-Al-PE pipe that is stu died in this article. To make a elaborate division, these dies can be classified as bending dies and forming dies here. In this paper, the designation of bendin g dies and forming dies that are used in producing technological process of PE- Al-PE pipe is put forward. The process starts from a coil of Al belt, in the ac tion of pulling force, passes between several bending dies to change its shape. The first step is to change Al belt to U shape. A couple of rolling wheels can b e used to shape the Al belt. The Al belt goes between the two rolling wheels, dr ives the wheels, at the same time is formed as the shape of the rolling wheels. Considering of the factors such as spring of the bend Al belt, frictional force between Al and the die, bending force needed to bend Al belt, etc., it must be s haped gradually into U by several dies. The designation of these dies has been g iven in this paper. The next step is to forming the U shape into a circle. The U shape Al belt goes through a round that is formed with a four-roller die, and then is shaped to a circle. Because the latter procedure requires the Al circle has a laminated area to be ultrasonic welded, this die must be designed to let t he two edges of the circle belt to be piled up to a definite width. But except f or the laminated area the other of the circle should be as round as possible. So the four rollers are not the same. The calculation and designation of the rolle rs of this four-roller die has also been given. The designation of the roller w hich is supposed to leave a gap to let the two edges of the circle belt to be pi led up is to make a fine rotation of an original circle. Then calculates the cen ter of the rotated arc and defines the arc completely. The designation method of the other rollers has also been given in this paper.

Effect of La_2O_3, Y_2O_3 Additives on Structure and Mechanical Property of Ceramic-Lined Composite Pipe Under Centrifugation

The effect of additives containing rare earth elements La and Y on the structure and mechanical property of ceramic-lined composite pipe was studied in presence of centrifugation. The fracture and shearing strength of ceramic-lined composite pipe containing different additives were measured and analyzed through the fracture and shearing strength experiments. The distribution of shear stress on the interface of ceramic layer and the pipe is computed by finite element method.

The Interlayer Stress Analysis of Polyethylene-steel Composite Pipes

Polyethylene-steel Composite Pipes is widely used in conveying corrosive media occasions,but the pipe may lose effectiveness in the process of transporting hot and cold media,so the research of stress distribution and variation in polyethylene-steel composite pipes is very necessary.This article first assume that a thin adhesive layer is in between the polyethylene and steel,the adhesive layer along the axial shear stress is the major cause of the polyethylene layer and the steel pipe off sticky.Secondly,we use a method of finite element to computer simulation by ANSYS,and verify initial assumptions.Finally,based on simulation data,we analyse the adhesive layer stress distribution and the variation with different parameters to change.Through the above research,preliminarily summarize the variation and distribution of interlaminar stress,and provide technical support for future design and process improvement of polyethylenesteel pipe.

Experiments of Multi-element Composite Foundation with Steel Pipe Pile and Gravel Pile

A set of serf-developed apparatus for foundation physical model were utilized to conduct model tests of the multi-element composite foundation with a steel pipe pile and several gravel piles. Some load-bearing characteristics of the multi-element Composite foundation, including the curves of foundation settlement, stresses of piles, pile-soil stress ratio, and load-sharing ratio of piles and soil, were obtained to study its working performances in silty sand soil. The experimental results revealed that the multi-element composite foundation with steel pipe pile and gravel pile contributed more than the gravel pile composite foundation in improving the bearing capacity of the silty fine sand.

Polyethylene/Aluminum/Polyethylene Composite Pipe for Fuel Gas Application

Polyethylene/aluminum/polyethylene(PAP)composite pipe has the advantages of corrosion resistance,limited joints and convenient installation.We started to use the PAP pipe in fuel gas conveyance 21 years ago.It has excellent performance in indoor gas application.Later,a unique method was designed to apply the PAP pipe in outdoor gas conveyance with the appearance of outdoor gas meter setting,which involves the addition of UPVC casing pipe as a protection technique to prevent the aging of PAP pipe.The method allows the PAP pipe to climb on the outer wall of building and get into user’s home directly after the connection with outdoor gas meter without any joints in the middle.Since 1996,the number of users has increased gradually and it achieves millions level globally today,including Europe,Asia,Oceania,South America and Africa.There were no quality and performance issues of using the PAP pipe in fuel gas conveyance indoor and outdoor in the past 20 years.In this paper,we put our effort on studying the effects of environmental temperature,sealing reliability,resistance to pipe pull-out,thermal compensation,and rat biting on PAP pipe and solve these problems.

Application of Glass Fiber Reinforced Polymer Composite (GFRPC) Escape Pipeline in Tunnel

During the tunnel construction process,unfavorable geological conditionsare often encountered.Geological disasters such as collapse,roof fall,water inrush,gas explosion,etc.occur frequently,causing different degrees of property damage and casualties to the construction of the tunnel,seriously affecting harmony during construction.The domestic emergency hedging is mainly the use of 8-10mm steel coils,but the steel is heavy and not suitable for the frequent movement of tunnels.This paper introduces the new Glass Fiber Reinforced Polymer Composite(GFRPC)escape pipeline used in Chongqing Jiuyongyi Jinyunshan Tunnel,and compares the traditional steel coil parameters to provide reference for subsequent tunnel hedging measures.

Analytical solutions to edge effect of composite laminates based on symplectic dual system

In the symplectic space composed of the original variables,displacements,and their dual variables,stresses,the symplectic solution for the composite laminates based on the Pipes-Pagano model is established in this paper.In contrast to the traditional technique using only one kind of variables,the symplectic dual variables include displacement components as well as stress components.Therefore,the compatibility conditions of displacement and stress at interfaces can be formulated simultaneously.After being introduced into the symplectic dual system,the uniform schemes,such as the separation of variables and symplectic eigenfunction expansion method,can be implemented conveniently to analyze composite laminate problems.An analytical solution for the free edge effect of composite laminates is obtained,showing the effectiveness of the symplectic dual method in analyzing composite laminates.

交通载荷作用下埋地含缺陷玻璃钢管道力学行为研究

为分析含缺陷玻璃钢管道在交通载荷作用下的力学行为,基于ABAQUS有限元软件建立了含不同形状缺陷管道模型和不同埋深管土模型,研究了不同埋深、不同载荷及缺陷深度对管道不同层中截面沿环向应力分布规律的影响。结果表明,无缺陷管道各层应力分布均匀,含缺陷管道内区域层应力沿管材缠绕方向集中于缺陷对称角处;管道仅含轴向缺陷时管体应力峰值与应力突变幅度最大;缺陷相对深度对管道应力峰值影响较大。

含裂纹油气管道CFRP修复数值研究

裂纹缺陷引发的管道强度下降是埋地油气管道的主要事故原因之一,而高强度、高模量、耐腐蚀的碳纤维增强树脂基复合材料(CFRP)可以很好地缠绕修复缺陷管段。针对有/无CFRP修复20钢含矩形裂纹缺陷管道,采用ANSYS有限元软件模拟内压载荷作用下含裂纹管道修复前后的响应过程,分析了裂纹角度、裂纹长度、裂纹深度、修复长度及修复厚度等参数对含裂纹管道强度的影响规律。研究表明,含裂纹管道的最大Mises等效应力随着裂纹与管道轴向夹角的减小、裂纹长度和深度的增大而增大,内压的增大加剧了缺陷参数对管道强度的影响程度。在工程中要严格控制裂纹在深度和长度方向的扩展,在内部减压后再维修含裂纹管道。CFRP修复厚度是修复后含裂纹管道强度的主要影响因素,随着修复厚度一定程度的增大,含裂纹管道最大Mises等效应力呈线性下降。

钛合金/钢钻杆复合钻柱动力学特性分析与优化设计

钻井深度的持续增加使钻柱面临的载荷工况越来越严苛。钛合金具有密度小、屈服强度高和弹性模量低等特点,基于井口钻杆抗拉余量设计要求,设计3种钛合金/钢钻杆复合钻柱,即复合钻柱1(Φ101.6 mm钻杆段全段使用钛合金钻杆)、复合钻柱2(Φ101.6 mm钻杆上半段使用钛合金钻杆)和复合钻柱3(Φ101.6 mm钻杆下半段使用钛合金钻杆)。为了探究钛合金/钢钻杆复合钻柱(简称为复合钻柱)的动力学特性,基于Hamiton原理建立复合钻柱的动力学模型,并采用节点迭代法和Newmark-β法对模型进行求解,分析3种复合钻柱的涡动特征、动态应力和振动特性,并与常规钢钻柱进行比较。结果表明:钛合金钻杆的使用可有效减缓钻柱涡动速度、动态应力,其中复合钻柱3的涡动速度、动态应力最小;基于振动特征强度对钻井作业参数进行优化,形成复合钻柱3的钻井作业参数推荐图版并给出合理的施工参数范围。

海洋复合管缆设计关键技术与挑战

海洋复合管缆是海洋资源开发的重要装备之一,广泛应用于海上油气开发、深海采矿、海上风电等。海洋复合管缆具有弯曲性能好、质量轻、强度高、耐腐蚀和耐高低温等优点,能满足海洋资源开发不断向深水进发的需求。然而,海洋复合管缆相较于传统均质管道结构设计更加复杂,力学特性和使用寿命的准确预测更加困难。结合相关规范对海洋复合管缆设计的常规方法进行介绍,并归纳总结海洋复合管缆设计中需要进一步考虑的结构优化技术、材料非线性问题、几何非线性问题和界面非线性问题(界面强度、界面疲劳、界面摩擦)等关键技术。研究结果可为海洋复合管缆的设计研究提供指导。

复合扩管式锚索恒阻器的研发与试验研究

深部高应力、软弱围岩、强烈采动影响等条件下的巷道围岩频繁出现大变形,此类围岩大变形支护可控性普遍较差,常规锚索因其较低的延伸率无法适应巷道大变形而大量破断或锚固失效,导致巷道出现冒顶隐患。针对此类问题,研发了一种与常规锚索配合使用的复合扩管式恒阻器,其结构主要由止进端盖、扩径管、一体式托盘和锥式锁具组成,通过锥式锁具克服扩径管“扩胀—摩削”所产生的近似恒定的复合阻力,实现围岩大变形过程中的锚索支护阻力恒定,通过理论分析、数值模拟和静力拉伸试验等综合研究方法,系统分析和试验了复合扩管式恒阻器的力学特性和工作稳定性,掌握了该恒阻器扩径增量、锁具锥角对扩径管变形及恒阻器复合阻力的影响规律。试验结果表明:恒阻器复合阻力主要分为阻力快升段和近恒定阻力段2个过程,且近恒定阻力段作为主要阶段达到试验全程的85%~90%;锁具锥角、扩径增量直接影响了扩径管变形及恒阻器力学特性,锁具锥角小于20°时,扩径管变形均匀且恒阻器复合阻力发挥稳定,而扩径增量则决定了恒阻器复合阻力的大小,可通过调整扩径增量获取需要的锚索恒阻力;Ф17.8 mm锚索条件下,当锁具锥角为15°、扩径增量为5 mm时,恒阻器恒定阻力约为265.92 kN,Ф21.8 mm锚索条件下,当锁具锥角为15°,扩径增量为8 mm时,恒阻器恒定阻力约为424.15 kN,且工作状态稳定可靠,可较好的符合大变形巷道的恒阻支护要求。此外,该恒阻器还具有工作稳定性强、恒阻行程及阻力可调、结构简单、安装便捷等特点,是大变形巷道围岩控制技术的有效补充。

岩溶区PST管桩复合地基的工程应用

经对某场地高层建筑地基素填土厚度大、下伏基岩岩溶发育、以多层串珠状溶洞为主的地层条件研究,提出一种PST管桩刚性复合地基。采用试验和监测等方法来指导复合地基处理设计与施工,根据场地试桩数据来验证设计的合理性。施工完成后,采用静载荷试验对复合地基进行质量验收检测,并连续进行沉降监测。结果表明:岩溶区PST管桩复合地基是一种处理高层建筑地基很可行的方法,处理后可以满足高层建筑物对地基强度、变形及稳定性的要求。

深基坑斜直交替钢管桩复合土钉墙数值模拟分析

依托福建某医院的基坑工程实例,采用数值模拟方法,研究斜直交替钢管桩复合土钉墙支护结构的变形特征及其稳定性。结果表明:坡面水平位移最大变形出现在基坑“腰部”,设计时应适当加强此位置的变形控制;斜直交替钢管桩复合土钉墙支护体系安全可行,其较双排直立钢管桩复合土钉墙及单一土钉墙有更好的变形控制能力和更高的稳定性。

冲击力下薄壁内衬复合管界面黏结强度效应分析

【目的】研究薄壁内衬复合管在受冲击力作用下的界面黏结强度对层间剥离屈曲的影响。【方法】建立薄壁内衬复合管在弹性阶段的非线性分析模型,对薄壁内衬复合管材模态试验与分析模型的分析结果进行对比,验证有限元分析模型可靠性。通过改变衬层与原基层管壁间的界面黏结强度,研究复合管在冲击力下的动态特征。【结果】研究结果表明,当冲击荷载较小、管道变形处于弹性阶段时,薄壁内衬复合管的损伤大都集中在层间界面处。界面黏结强度对层间剥离屈曲有较大的影响,随着层间界面黏结强度的增加,外基层管与内衬层的最大等效应力差值减少。此外,外基层管和内衬层的变形协调性能力随着黏结强度增加而增大,径向层间位移减小,增加了复合管的整体性和连续性。【结论】研究结果可为薄壁内衬修复管道设计方法及层间界面效应分析提供参考。