Deformation Of Pipe Research Articles

Experimental study on thermal deformation of ground heat exchanger pipe

In the application of borehole thermal energy storage, the operation temperature of ground heat exchangers exceeds 50 °C usually. The buried pipe can show thermal buckling under high temperature load. This thermal deformation can be harmful to the structural stability and influence the heat transfer efficiency. The novelty of this study is to investigate the thermal deformation (buckling) of vertical buried pipe and the influence of initial backfill confining pressure. However, the thermal deformation of buried pipe is hard to measure. So the strain method is first put forward in this work. By experiment, the thermal strains, thermal displacement, and residual deformation of the pipe are analysed. The results indicate that the buried pipe with symmetrical arc structure can show asymmetric strains and deformation distribution. By comparison, thermal deformation in heating process can be larger than cooling process. So the residual deformation will generate after heating–cooling process. Increasing initial confining pressure can reduce thermal deformation and residual deformation of pipe.

Effect of Foundation Pit With Different Support and Excavation Methods on Adjacent Buried Hydrogen Pipe

Abstract Support and excavation methods have a great effect on the supporting role of the foundation pit. To investigate the effect of foundation pit with different support and excavation methods on adjacent buried hydrogen pipe, a pipe–soil coupling model was established. Deformation, strain, and stress of the pipe near the foundation pit with different support and excavation methods were analyzed. The results show that stress concentration appears on the upper and lower surfaces of the middle part of the pipe after the foundation pit excavation. The high stress areas on the upper and lower surfaces are distributed symmetrically about the pipe center. Upper surface of the pipe's middle section is pressed and the lower surface is pulled, but the strain distribution of the pipe at the pit edge is opposite. Vertical displacement of the pipe is bigger than its horizontal displacement. The underground continuous wall as the most common support structure can effectively reduce the pipe deformation. Supporting methods have different effects on buried pipe's mechanical behavior. Lateral reinforcement, inner support, and bolt support can effectively reduce the pipe deformation, but the mitigating effect of lateral reinforcement is less than inner support and bolt support. The pipe is also affected by time and space of the foundation pit excavation. The slope excavation can greatly reduce the pipe deformation, but the effects of island excavation and basin excavation are not obvious. Those results can provide references for pipe safety assessment and protection.

Development of Protective Gas Pipes Sleeves for Operation in Permafrost Soils

Experimental studies were carried out and causes of emergencies with gas pipes in protective sleeves used in construction of gas pipelines were identified. Protective sleeve design has been developed that excludes deformation or destruction of gas pipeline during groundwater freezing in the annulus. Model tests of polyethylene gas pipeline in steel casing, using polyethylene foam as an element that compensates expansion of water during freezing, showed complete exclusion of deformation of gas pipes during freezing. Test results of developed designs of protective casings showed the possibility of widespread use to improve reliability and safety of gas supply.

Cold deformation of non-circular drill pipes

In this paper, the pipe billet dimensions are determined according to the required kelly configuration. A finite element model of the deformation center at drawing junctions is created. Based on the stress-strain calculations, the following invariants are determined: hydrostatic pressure, load, and degree of shear strain. The metal damage extent is determined and proved to be reducible by performing the two-pass drawing. It is shown that the ‘pendulum’ heat treatment provides for complete healing of the metal defects caused by plastic deformation. As a result, a technology of producing high quality kellies is proposed.

Mechanical Characteristic Analysis of Buried Drainage Pipes after Polymer Grouting Trenchless Rehabilitation

The application of polymer grouting in underground pipeline rehabilitation is increasing gradually. The leakage and subsidence of buried pipelines could be repaired by polymer grouting technology. In order to analyse the calculation theory of the pipeline repairing process, the Winkler model and the Vlazov model of the pipe-soil-polymer interaction based on the elastoplastic theory are established, the calculation formulas of the pipe-soil interaction under polymer grouting are derived, and the MATLAB calculation program based on the transfer matrix method is compiled. Then the calculated values are compared with the pipeline experimental values, and the influence of different factors on the internal force and deformation of the polymer-repaired pipeline under different work conditions is discussed. The results show that the values and trends of the pipe deformation and circumferential bending moment calculated by the models are consistent with the experimental results, and the results obtained by the Vlazov model are closer to the experimental values. In addition, the void at the bottom of the pipeline has a large impact on the mechanical properties of the pipeline. However, polymer grouting can repair disengaged pipelines effectively and restore their mechanical properties. The proposed methods and calculation results are valuable for pipeline polymer repairing analysis and pipeline void repairing design.

Pipe-Soil Interaction and Sensitivity Study of Large-Diameter Buried Steel Pipes

Large-diameter buried steel pipes (BSPs) have been widely utilized in water diversion and hydropower fields. This paper presents a comprehensive numerical investigation on the interaction between the large-diameter pipe and soil under three typical working conditions, to capture the structural mechanical behaviors of pipe deformation, soil displacement, and soil pressure. Furthermore, a parametric analysis of pipe diameter is conducted, along with the sensitivity study of soil parameters based on the orthogonal test method. The results show that the water weight increases the pipe deformation significantly by 14%, while the high internal water pressure decreases the deformation greatly with the maximum effect of 39%. The pattern of soil pressure at the top of the pipe changes from parabola to double-hump as the pipe diameter varies from 0.5 m to 5.0 m. The pipe deformation and soil pressure keep increasing with the pipe diameter, but the safety margin for prism load decreases gradually. Pipe deformation and soil pressure are very sensitive to the elastic modulus and Poisson’s ratio of backfill. Friction coefficients of soil-soil (trench sidewall) and pipe-soil have great influences on the soil pressure, while the bedding material and backfill cohesion have small effects on it.

Compacting nanopowder materials by a pulse pressure generated by expanding plasma channel of a spark ignited by wire electrical explosion

The purpose of the article is to explore the possibilities of powder material compaction by the pressure pulse of an electric explosion of a conductor, establish a functional relationship between the parameters of the pressure pulse and an electrical technological installation for powder material compaction, select the parameters for pulse pressure amplitude and duration adjustment, and specify the design options of the working tool for powder material compaction. Analytical studies have been carried out on the basis of the method of formalized representation of the development of the process of pulse pressure wave formation and propagation where the latter is created by an expanding plasma channel of an electric spark in a transmitting medium initiated by an electric explosion of a wire. The simulation of high-speed de formation of the pipe wall under the action of the pulse pressure is carried out in the MATLAB software package. A scanning electron microscope is used to study the microstructure of the breakage of the compacted material with nanomodifiers. Based on the experimental studies on powder material compaction by the pulse pressure created by the expanding plasma channel of a spark initiated by an electric explosion of a wire when the current pulse f rom an electrotechnological installation is supplied to it, it has been determined that the magnitude and shape of the pressure pulse are most influenced by the parameters of this installation. Based on the obtained model studies, the optimal modes for compaction of nanomodified powders have been selected. The relationship is obtained between the parameters of the pulse pressure (Pm amplitude and pressure wave propagation form) and the electrotechnological installation (voltage, inductance, capacitance). It is proposed to use an acoustic-electric wave model to estimate the pressure that provides high-speed deformation of metal pipes, and to plot a deformation profile of metal pipes used for compaction. Analysis of SEM images of the fractures obtained in compact experiments has showed a high degree of particle compaction with the formation of a solid composite.

Lamé's problem on pipe deformation under the action of internal and external pressure

Lamé's problem on pipe deformation under the action of internal and external pressure

Deformation Inspection and Safety Assessment Method of Buried Flexible Pipeline in Service

The working performance of buried flexible pipelines is connected with the pipe- soil interaction; the weak stiffness of backfill leads to large long-term pipeline deformation and even structural failure. Spangler’s formula is a theory for macroscopic evaluation of pipeline deformation, which cannot reflect the deformation state of various parts around the pipe from a microscopic view. A large number of engineering practices have shown that when the macro radial deformation of the flexible pipe is not large, it is also possible that the local geometric size of the pipeline may change suddenly in the microscopic view. Combining with a diversion project, a laser scanning and piecewise elliptic curve fitting combined method was proposed to measure the empty pipeline deformation in this paper. The deformation pattern of the flexible pipeline was analysis. And then, the analysis results were verified by the elastic wave test and material test data. Based on the deformation inspections, the internal force and related reliability of pipe structure were calculated. Finally, the structural safety of each pipe was assessed to guide the replacement, repair and reinforcement of pipeline.

Effects of surging and heaving movements of platform on mechanical behaviors of SCT installation pipe

The effects of surging and heaving movements of installation platform on mechanical behaviors of SCT installation pipe was studied. Movements of SCT installation platform, ocean wave and current, water depth, SCT weight, installation pipe specification and those dominate the mechanical behaviors of installation pipe and SCT installation precision were considered. The results indicate that surging movement of the platform is the main factor that dominate the deformation of the installation pipe. The surging and heaving movements have significant effect on the tension force loaded on the installation pipe and thus need to be considered when designing SCT installation.

Estimating deformation of pipe from its internal image

Estimating deformation of pipe from its internal image

Estimating deformation of pipe from its internal image

Estimating deformation of pipe from its internal image

Protecting buried pipelines using different shapes of geofoam blocks

Purpose. This research presents experimental modeling and numerical analysis on reducing stress and protecting buried pipelines using three arrangements techniques of expanded polystyrene (EPS) geofoam blocks: embankment, EPS block embracing the upper part of the pipe and EPS blocks as two posts and a beam. Methods. An experimental model consisted of steel tank with boundaries dimensions depending on the diameter of the pipe located at the center of it. The backfill on the pipe was made from sand and embedded EPS blocks with two techniques: EPS block embracing the upper part of the pipe and EPS blocks form two posts and a beam. Series of experiments were carried out using static loading on rigid steel plate to measure the pipe deformations and strains, as well as backfill surface displacement. The numerical analysis was used to simulate the experimental model using the finite element software program PLAXIS-3D. Findings. The results reveal that the most effective method which prevents stress on the buried flexible pipe was EPS post and beam system followed by EPS embracing the upper part of the pipe. The results obtained from the numerical analysis and the experiment demonstrate the same trend. The parametric study shows that EPS post and beam blocks model has higher surface displacement than embracing the upper part of the pipe model, which is more effective in case of high rigidity of the pipe. Originality. Reducing stress on buried pipes using different geofoam shapes to find which one is the optimum method. Practical implications. Two configurations of EPS geofoam blocks – EPS block embracing the upper part of the pipe and EPS blocks post and beam system - ensure successful stress reduction and protect buried pipes

Development of Energy-Dissipating Device for Rockfall and Debris-Flow Barriers

In this study on the development of energy-dissipating devices, a significant component of the ring-net system was investigated for the localization of a high-performance rockfall fence and debris flow barriers. The energy-dissipating device was developed as a structure that dissipated the resistance and frictional forces generated by the pipe passing through two steel bars, and the tensile force was transmitted by utilizing the pipe deformation. The performance of the developed energy-dissipating device was verified through simulation analysis and tensile tests. It was confirmed that the most effective dissipating device was made of a D60.5-3.2t pipe subjected to a rolling interval of 40 mm, and the device exhibited an energy-dissipating performance of 52.8-60.2 kJ/m.

Numerical-Experimental Analysis of Polyethylene Pipe Deformation at Different Load Values.

Polymer pipes are used in the construction of underground gas, water, and sewage networks. During exploitation, various external forces work on the pipeline, which cause its deformation. In the paper, numerical analysis and experimental investigations of polyethylene pipe deformation at different external load values (500, 1000, 1500, and 2000 N) were performed. The authors measured strains of the lower and upper surface of the pipe during its loading moment using resistance strain gauges, which were located on the pipe at equal intervals. The results obtained from computer simulation and experimental studies were comparable. An innovative element of the research presented in the article is recognition of the impact of the proposed values of the load of polyethylene pipe on the change in its deformation.

Investigation of the influence of corrosion defects on the durability of main oil pipelines

For the sake of ensuring the energy security of Ukraine, the trouble-free operation of the oil transportation system becomes of strategic importance. The problem is exacerbated in connection with the long service life of individual objects of the system, which leads to degradation of the properties of the pipe material due to corrosive and erosion processes, which is enhanced by the effect of time-varying loads. Today, in world practice, various methods are used to strengthen defective sections of pipelines: installation of steel, plastic and fiberglass couplings, winding of an elastic composite tape, the use of reinforcing composite couplings, etc. To study the effect of microcracks, corrosion and erosion defects on the Druzhba oil pipeline of OJSC Ukrtransnafta with an installed bandage, full-scale tests of a defective section of a pipe (material - 17GS steel) reinforced with bandages made of a similar material using a UI1 / 200 GK installation were carried out. As a result of research, the pressure of its destruction was determined. During the tests, strain gauging was used to determine pipe deformations. Comparison of the values of stresses obtained experimentally and analytically confirmed that the use of bands on defective sections of the pipeline is an effective means for extending their service life. For a more accurate and detailed analysis of the reliability and durability of oil pipelines, a study of the defective parts (break point) cut from the pipeline was carried out. As a result of the studies carried out on the models - "cutouts", corrosion defects with a depth of up to 5 mm were registered, which is about 55% of the loss of metal, however, the pipe was not destroyed by these defects, but by a defect of the "crack" type. To obtain the profile of the defect from the model - "cutout", scanning was carried out using a sensor fixed on a mobile tripod connected to a computer via an ADC. At the next stage of research, the assessment of the residual resource was carried out using the analysis of full-scale kinetic curves of damage to hazardous sections of the oil pipeline through experimental studies of models - "cutouts". A fatigue curve has been constructed, which can later be used to predict the fatigue life of such elements.

Assessment of the possibility of quenching pipes made of titanium alloys after pressing

The purpose of the work is to determine the possibility of quenching pipes made of titanium alloys after pressing. To evaluate the level of properties and the structure of pipes after quenching, which will ensure further cold rolling. Methodology. The following methods used: metallographic methods that research-optical microscopy, tensile testing of pipes to assess mechanical properties, Brinell and Rockwell hardness measurements. Results. The structure and mechanical properties of pipes made from Gr 9 and PT-1M titanium alloys after pressing and quenching in water were studied in comparison with air cooling. The possibility of quenching pipes after pressing is shown. The level of mechanical properties and type of structure allows for subsequent plastic deformation of pipes by cold rolling methods. After quenching, the pipe should be thermally treated. Scientific novelty. The impact of quenching after pressing on the structure and mechanical properties of pipes made from titanium alloys has been established. The possibility of quenching pipes after pressing is shown. Practical significance. The established possibility of the quenching process allowed in the technological process of manufacturing titanium pipes to improve the surface quality of pressed pipes, avoid the operation of turning and thereby reduce the consumption coefficient of the metal.

Numerical Study of the Use of Tyre-Derived-Aggregate (TDA) as the Backfill Above Flexible PVC Pipeline

Tyre Derived Aggregates (TDA), produced by shredding scrap car tyres, show many interesting features, such as: durability, low bulk density, thermal insulation, good drainage properties or ability to damp vibrations, which makes them a useful material for civil engineering. One of the possible applications is the partial filling of excavations with TDA during the construction of underground pipelines in order to decrease the load applied on the pipe. The article presents results of a multivariate numerical study of 2D FEM models of a flexible PVC pipe - soil system, in which the presence of a mixture of sand and TDA (tyre chips - 40% by weight) (STCh) in the backfill was simulated. The models differed in the thickness of the STCh layer (t = 0 – 0.9 m) and inclination of the excavation walls (a trench with vertical walls or open excavations with 3:1 and 1:1 slopes). The main goal of the numerical analyses, performed by means of the Z_Soil.PC program, were to investigate the effect of the presence of the softer STCh layer in the backfill zone on the pipe deformation (relative deflection δ/D) and internal forces in the pipe wall. The soil was simulated with the use of either the Hardening Soil Small (HSS) or Coulomb-Mohr (CM) constitutive model with the parameters’ values estimated based on results of laboratory tests (published by researchers from Wollongong University). The PVC pipe was modelled as linear elastic. The results of the analyses show that, due to enhanced arching, STCh layer of the optimum thickness t = 0.55 m can effectively reduce δ/D when used in the backfill of the trench. It can also decrease the difference between the maximum and minimum bending moment in the pipe wall, leading to less ovalization of the pipe cross-section. This positive effect diminishes if the width of excavation is larger, as the model is gradually transforming towards the positive projecting conduit type. The CM model gives underestimated values of the pipe deformation and internal forces. Though, in the case of lack of all the HSS parameters’ values, it is better to use the CM model with E = E 50 than E = E ur as it gives a better approximation of pipe behaviour.

Strain ratcheting failure of dented steel submarine pipes under combined internal pressure and asymmetric inelastic cycling

This paper presents the results of an experimental study in which for the first time the progressive inelastic deformation of high strength steel pressurized pipes with plain and gouged dents was analyzed. The effect of some key loading and geometrical parameters such as initial pre-strain (εmon), dent depth ratio (δ/D) and the presence of the gouge was studied. Local dents with a hemispherical shape and gouges with different dimensions were introduced on the surface of the specimens. Specimens with plain or gouged dents were first internally pressurized, axially compressed to an initial pre-strain then subjected to cyclic nonlinear stressing.The mechanical defects were found to drastically degrade the inelastic cyclic response of the pressurized steel pipes. The presence of a dent, even with small amounts of initial pre-strains, made the pressurized pipes vulnerable to ratcheting failure. Furthermore, the ratcheting responses of the gouged dented specimens significantly differed from those for the corresponding specimens with plain dents. In fact, the combination of a dent and gouge was the severest form of the defect and demonstrated the lowest number of cycles before failure. The degradation effects of gouge were strongly dependent upon the gouge geometry, dent depth and initial pre-strain level.

Burst pressure of thin-walled pipes with dent and gouge defects

Mechanical interference is the main cause of the failure of thin-walled pipelines in some countries. Gouges and dents are two common types of external interference that threaten the structural integrity of thin-walled pipes. This paper presents an experimental and numerical investigation of the failure pressure and strain history of thin-walled pipes with dent and gouge defects. First, four full-scale burst tests were conducted. Then, a 3D nonlinear finite element model was established, and its accuracy and reliability were validated using the experimental data. On the basis of the experimental and numerical results, the failure pressure of the thin-walled pipes with dent and gouge defects was studied in detail. During the burst process, the variation in axial strain is small, whereas the circumferential strain changes significantly. Test results show that failure location occurred at the flank of dent. Pipe deformation is more prominent for small defects. A parametric study suggests that the failure pressure increases with decreasing dent depth, pipe diameter-to-wall-thickness ratio, and gouge depth and length. The gouge size has the strongest effect on the failure pressure of thin-walled pipes with dent and gouge defects.