Journal articles: 'Crack in pipe'

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Zhang, Zongyuan, Hongyuan Fang, Bin Li, and Fuming Wang. "Mechanical Properties of Concrete Pipes with Pre-Existing Cracks." Applied Sciences 10, no. 4 (February 24, 2020): 1545. http://dx.doi.org/10.3390/app10041545.

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Concrete pipes are the most widely used municipal drainage pipes in China. When concrete pipes fall into years of disrepair, numerous problems appear. As one of the most common problems of concrete pipes, cracks impact on the deterioration of mechanical properties of pipes, which cannot be ignored. In the current work, normal concrete pipes and those with pre-existing cracks are tested on a full scale under an external compressive load. The effects of the length, depth, and location of cracks on the bearing capacity and mechanical properties of the concrete pipes are quantitatively analyzed. Based on the full-scale tests, three-dimensional finite element models of normal and cracked concrete pipes are developed, and the measured results are compared with the data of the finite element analysis. It is clear that the test measurements are in good agreement with the simulation results; the bearing capacity of a concrete pipe is inversely proportional to the length and depth of the crack, and the maximum circumferential strain of the pipe occurs at the location of the crack. The strain of the concrete pipe also reveals three stages of elasticity, plasticity, and failure as the external load rises. Finally, when the load series reaches the limit of the failure load of the concrete pipe with pre-existing cracks, the pipe breaks along the crack position.

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Sevcik, Martin, Pavel Hutar, Lubos Nahlik, Ralf Lach, Zdenek Knesl, and Wolfgang Grellmann. "Crack propagation in a welded polyolefin pipe." International Journal of Structural Integrity 3, no. 2 (May 25, 2012): 148–57. http://dx.doi.org/10.1108/17579861211235174.

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PurposeThe purpose of this paper is to study the effect of the material inhomogeneity on crack behavior initiated both axially and circumferentially in or near the butt weld and to discuss consequences on residual lifetime of the welded structure.Design/methodology/approachA three‐dimensional numerical model of pipe weld with smooth and continuous change of material properties has been used to study the fracture behavior of the cracked pipe structure. The stress intensity factor was considered as a parameter controlling the fracture behavior. The semi‐elliptical shape of the crack front was estimated under assumption of constant stress intensity factor along the crack front.FindingsAccording to the results obtained in the paper the following conclusions were deduced. First, the most critical location of the crack is in the middle of the inhomogeneous region (weld center) regardless of the crack orientation. The stress intensity factor is substantially higher than in the case of a crack located in the homogenous pipe. Second, with regard to crack shapes, the circumferentially oriented cracks are practically identical regardless to the crack location if compared with the axial cracks. Third, the stress intensity factors of axially‐oriented cracks are approximately twice higher than in the case of circumferential cracks. This implies that the cracks are more likely to grow in an axial direction.Originality/valueThe results described in the paper can be used for estimation of critical crack length or for estimation of the critical applied inner pressure of medium transported in the pipe and are of paramount importance for service life estimations of polymer welded pipes in actual use.

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Fezazi, Amina Ismahène, Belaïd Mechab, Salem Mokadem, and Boualem Serier. "Numerical prediction of the ductile damage for axial cracks in pipe under internal pressure." Frattura ed Integrità Strutturale 15, no. 58 (September 25, 2021): 231–41. http://dx.doi.org/10.3221/igf-esis.58.17.

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This study presents a numerical prediction of the ductile damage for axial cracks in pipe subjected to internal pressure. The three dimensional finite element methods used to evaluate the J-integral. The effect of the external radius (Rext),the thickness (t), length crack (a) , the applied loads (P) and the crack position of the pipes has studied. The Monte Carlo method was used to determine the probabilistic characteristics of the J-integral. It’s also used later to predict the failure probability based on initiation of the crack growth. We note that the crack size and the geometries of the pipe are an important factor influencing on the durability of the pipe.

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Jinxin, Dou, Yang Tongguang, Yu Xiaoguang, Xue Zhengkun, Liu Zhongxin, and Sun Jie. "Model-driven fault diagnosis of slant cracks in aero-hydraulic straight pipes." Advances in Mechanical Engineering 12, no. 9 (September 2020): 168781402095497. http://dx.doi.org/10.1177/1687814020954970.

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A model-driven fault diagnosis method for slant cracks in aero-hydraulic straight pipes is presented in this paper. First, fracture mechanics theory and the principle of strain energy release are used to derive an expression for the local flexibility coefficient of straight pipes with slant cracks. The inverse method of total flexibility is used to calculate the stiffness matrix of straight pipe elements with slant cracks. Second, the Euler-Bernoulli beam model theory is used in conjunction with the finite element method to construct a dynamic model of the cracked pipe. Finally, a contour map method is used to diagnose the slant crack fault and quantitatively determine the crack position and depth. Experimental results show that the proposed method can accurately and effectively identify a slant crack fault in aero-hydraulic pipelines.

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Wang, Fusheng, Zheng Wei, Pu Li, Lingjun Yu, and Weichao Huang. "Initial Crack Propagation and the Influence Factors of Aircraft Pipe Pressure." Materials 12, no. 19 (September 23, 2019): 3098. http://dx.doi.org/10.3390/ma12193098.

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In aircraft engineering, an increase of internal pressure in a hydraulic pipe increases the probability of pipe damage, leading to crack propagation becoming a serious issue. In this study, the extended finite element method (XFEM) is applied to simulate initial crack propagation in hydraulic pipes and to investigate the influence factors. Stress intensity factors are extracted to verify the mesh independence of XFEM, which is based on the level set method and unit decomposition method. A total of 30 finite element models of hydraulic pipes with cracks are established. The distribution of von Mises stress under different initial crack lengths and internal pressures is obtained to analyze the change of load-carrying capacity in different conditions. Then, a total of 300 finite element models of hydraulic pipes with different initial crack sizes and locations are simulated under different working conditions. The relationship between the maximum opening displacement and crack length is analyzed by extracting the opening displacement under different initial crack lengths. The length and depth of the initial crack are changed to analyze the factors affecting crack propagation. The opening size and crack propagation length are obtained in different directions. The results show that radial propagation is more destructive than longitudinal propagation for hydraulic pipes in the initial stage of crack propagation.

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Zahoor, A. "Analysis of Part-Throughwall Crack in a Pipe Under Combined Tension and Bending." Journal of Engineering Materials and Technology 114, no. 3 (July 1, 1992): 245–49. http://dx.doi.org/10.1115/1.2904168.

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J-resistance curve solution is developed for a circumferential part-throughwall crack in a pipe under combined tension and bending. The J solution can be applied with load-displacement-crack extension data from one pipe test. Material resistance curves are developed for part-throughwall cracks in Type-304 stainless steel base material and SAW weld, and SA333 Gr6 and A106 GrB carbon steel base materials. Posttest tearing instability analyses are performed to predict the load carrying capacity of pipes containing part-throughwall cracks and to assess the accuracy of a Jestimation scheme solution.

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Okodi, Allan, Yong Li, Roger Cheng, Muntaseer Kainat, Nader Yoosef-Ghodsi, and Samer Adeeb. "Crack Propagation and Burst Pressure of Pipeline with Restrained and Unrestrained Concentric Dent-Crack Defects Using Extended Finite Element Method." Applied Sciences 10, no. 21 (October 27, 2020): 7554. http://dx.doi.org/10.3390/app10217554.

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Mechanical damage in form of dents, cracks, gouges, and scratches are common in pipelines. Sometimes, these damages form in proximity of each other and act as one defect in the pipe wall. The combined defects have been found to be more injurious than individual defects. One of the combined defects in pipeline comprises of a crack in a dent, also known as dent-crack defect. This paper discusses the development of finite element models using extended finite element criterion (XFEM) in Abaqus to predict burst pressure of specimens of API X70 pipeline with restrained and unrestrained concentric dent-crack defects. The models are calibrated and validated using results of full-scale burst tests. The effects of crack length, crack depth, dent depth, and denting pressure on burst pressure are investigated. The results show that restrained dent-crack defects with shallow cracks (depth less than 50% wall thickness) inside dents do not affect pipeline operations at maximum allowable operating pressure if crack lengths are less than 200 mm. Releasing restrained dent-cracks when the pressure is at maximum allowable operating pressure can cause propagation of deep cracks (depth of 50% wall thickness or more) longer than 60 mm. However, only very long cracks (200 mm and higher) propagate to burst the pipe. Cracks of depth less than 20% of wall thickness inside dents formed at zero pressure are not propagated by the maximum allowable operating pressure. Dent-crack defects having dents of depth less than 2% outside diameter of pipe behave as plain cracks if the dents are formed at zero denting pressure but are more injurious than plain cracks if the dents are formed in pressurized pipes.

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Yang, Zhuan Zhao, Dao Xin Liu, and Xiao Hua Zhang. "Crack Analysis of Induction Heating Bent Pipe." Applied Mechanics and Materials 29-32 (August 2010): 697–702. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.697.

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There were 20 of 103 length of pipe found cracks on the extrados surface of the bent pipe made of Φ406.4×10mm L360 Longitudinal Submerged Arc Welding (LSAW) pipe, the cracks were mostly distributed in the extrados surface and the arc initial point of the bent pipe, the cracks were spindle-shaped and narrow at both ends with the longitudinal direction vertical to the axis of bent pipe. The mechanism and the causes of the cracks were studied by macro inspection, mechanical property test, microscope, scanning electron microscopy and energy spectrum analysis, which shown that the cracks were result from the contamination of copper or its alloy during or before the bent pipe production. The contaminated material like copper infiltrated and diffused into the base metal at high temperature, and could hardly stead to and transfer the normal stress from the base metal where the inertial crack was shaped. Meanwhile, the new crack was formed at the tip of inertial crack after the new infiltration and diffusion under the condition of both high temperature and tensile stress, so that the crack progressed and extended in this way.

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Kim, D. S., and K. H. Lo. "Crack Interaction Criteria in Pressure Vessels and Pipe." Journal of Offshore Mechanics and Arctic Engineering 117, no. 4 (November 1, 1995): 260–64. http://dx.doi.org/10.1115/1.2827232.

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An attempt was made to define a new crack interaction criterion for pressurized cylinders with two co-planar surface cracks. Elastic-plastic finite element method with line spring concept (line spring element method) was used to verify the validity of the new interaction criterion and to establish the relative conservatism built into various codes/standards. The crack interaction criteria of two co-planar surface cracks as defined by ASME Section XI and BS PD6493 were studied and a new interaction criterion which accounts for crack shape and load factor was introduced. The basic idea behind the crack interaction criteria for co-planar surface cracks was the plastic zone and stress interaction near crack tips. To verify the new crack interaction criterion, comparisons of J-integral values were made for various crack sizes with different distances between cracks and loading conditions. Based upon these comparisons, the new crack interaction criteria, comparing a physical distance, s, to a characteristic distance d=(σ/σy)2(c1Q1 + c2Q2), proved to be a reasonable parameter for indication of the crack driving force interaction for co-planar cracks. The characteristic distance also represents a rigorous measure of an equivalent crack driving force for interacting cracks.

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Olamide, Ayodeji, Abdeldjalil Bennecer, and Stefan Kaczmarczyk. "Finite Element Analysis of Fatigue in Offshore Pipelines with Internal and External Circumferential Cracks." Applied Mechanics 1, no. 4 (November 24, 2020): 193–223. http://dx.doi.org/10.3390/applmech1040013.

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Fatigue lifetime of offshore pipelines with semi-elliptical circumferential surface cracks is often underestimated. An accurate prediction of the pipeline structural integrity is nevertheless important in order to prevent unnecessary and expensive downtime, failures leading to leakage or spillage of pipeline contents to the surrounding environment, and ultimately improve the reliability of the pipeline. The estimation of crack growth in pipelines under varying loads is highly dependent on the calculation of crack driving parameters, such as the stress intensity factor and the crack tip opening displacement (CTOD) using the 3D J-integral or its equivalent. This paper presents a numerical study to predict the fatigue lifetime of cracks in pipes, determining the J-integral that includes first and second derivatives of the displacement field for pipes containing a range of circumferential surface cracks. A pipe segment is structurally loaded and stress intensity factors (SIF) evaluated using the finite element method (FEM). Based on the results, a number-of-cycles to failure curve shows a longer lifetime than previously predicted by about 5% for a pipe with semi-elliptical external surface cracks. In addition, they indicate that the external short cracks are more dangerous than the internal long surface crack hereby requiring earlier assessment.

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Kim, Yun Jae, Chang Sik Oh, Bo Kyu Park, and Young Il Kim. "Limit Loads for Circumferential Cracked Pipe Bends under In-Plane Bending." Key Engineering Materials 321-323 (October 2006): 38–42. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.38.

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This paper presents limit loads for circumferential cracked pipe bends under in-plane bending, based on detailed three-dimensional finite element limit analyses. FE analyses are performed based on elastic-perfectly-plastic materials and the geometrically linear assumption. Both through-wall cracks and part-through surface cracks (having constant depths) are considered, together with different crack locations (extrados and intrados). Based on the FE results, closed-form approximations are proposed for plastic limit loads of pipe bends. It is found that limit loads of pipe bends are smaller than those of straight pipes, but are close for deep and long cracks.

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Zhu, Zhi Bin, Xiao Xiang Yang, Li Jing Chen, Nai Chang Lin, Zhi Tuo Wang, and Zhe Fang Wang. "Finite Element Analysis of Polyethylene Pipe Butt Fusion Joints with Circumferential Surface Cracks." Advanced Materials Research 785-786 (September 2013): 1151–58. http://dx.doi.org/10.4028/www.scientific.net/amr.785-786.1151.

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Based on the viscoelastic material property of polyethylene pipe, software ANSYS was used to simulate and analyze the mechanical property of polyethylene pipe butt fusion joints with circumferential surface crack defects. The viscoelastic material creep parameters were characterized as Prony series and 1/4 node singular element was selected for meshing along the boundaries of the crack, then the stress intensity factor of polyethylene pipe butt fusion joints with circumferential surface crack was calculated under the uniform internal pressure. Through the finite element simulation, the result showed that polyethylene pipe were most likely to fracture failure when crack initiated. Thus the viscoelasticity of materials can be ignored when analyzing the stress intensity factor of circumferential surface cracks of polyethylene pipe. the main influencing factor of the circumferential crack defects was the ratio of the crack depth to the thickness of polyethylene pipe.

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Chen, Guanren, Takuya Katagiri, Noritaka Yusa, and Hidetoshi Hashizume. "In-pipe crack detection for multiple diameters using TE11 mode microwaves." International Journal of Applied Electromagnetics and Mechanics 64, no. 1-4 (December 10, 2020): 39–46. http://dx.doi.org/10.3233/jae-209305.

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This study evaluated the effect of pipe diameter on the applicability of a technique using TE11 mode microwaves for in-pipe crack detection. Three TE11 mode converters of different inner diameters were designed based on theoretical calculations and verified via numerical simulations. The working bandwidths of these mode converters were 7.0, 4.0, and 1.9 GHz. Experimental verification was carried out using brass pipes with the corresponding three inner diameters, and with pipe lengths up to 21–25.5 m. An axial and a circumferential slit were introduced to simulate cracks and deployed at multiple positions along the pipes under test. The results showed that both axial and circumferential slits could be detected and located for an inner pipe diameter up to 39 mm and at a distance of 15 m–24 m.

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Law, M., Valerie Linton, and Erwin Gamboa. "Fatigue Crack Growth Comparison between Sleeved and Non-Sleeved Pipeline." Advanced Materials Research 41-42 (April 2008): 105–12. http://dx.doi.org/10.4028/www.scientific.net/amr.41-42.105.

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A section of gas pipeline containing dormant stress corrosion cracks was removed from service and pressure cycled, and the crack growth from fatigue was measured. Crack growth was able to be conservatively calculated by BS7910. Parts of the pipeline section had composite repair sleeves placed over it in order to compare fatigue crack growth of sleeved and unsleeved cracks. Sleeved cracks consistently showed less crack growth than unsleeved cracks; this is believed to be due to reduced hoop stresses in the pipe under the composite repair sleeve and reduced crack opening. A simple model of the sleeve repair was developed which was consistent with the measured strains in the pipe. The application pressure of the sleeve repair affects the amount of stress reduction in the pipe and the amount of crack growth experienced. Two possible methods of repair of SCC affected pipelines were validated by this work.

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He, Yu Min, Xi Chen, and Xiao Long Zhang. "Influence of a Crack on the Natural Frequency of Pipe." Applied Mechanics and Materials 80-81 (July 2011): 527–31. http://dx.doi.org/10.4028/www.scientific.net/amm.80-81.527.

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Pipe crack identification method based on vibration has been researched by many people in recent years. The natural frequency plays an important role in the method. The natural frequency will change due to the appearance of the crack, so the crack may be identified according to the change law of the natural frequency with the size and location of crack. The dynamic model of cracked pipe is established by dispersing the pipe into a series of nested thin-walled pipes in this paper, and then the change law of the first three natural frequencies of the pipe is discussed.

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Poduška, Jan, Pavel Hutař, Andreas Frank, Jaroslav Kučera, Jiří Sadílek, Gerald Pinter, and Luboš Náhlík. "Soil Load on Plastic Pipe and its Influence on Lifetime." Strojnícky časopis - Journal of Mechanical Engineering 69, no. 3 (November 1, 2019): 101–6. http://dx.doi.org/10.2478/scjme-2019-0036.

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AbstractLifetime of plastic pipes can be estimated by integration of a power law describing the crack kinetics. However, this procedure requires an FEM (finite element method) calculation of the possible crack propagation in the pipe to obtain stress intensity factor dependency on the crack length. It is very important for the simulation to consider every possible load that is acting on the pipe. This contribution deals with FEM modelling of a pipe that is loaded by internal pressure, residual stresses and soil loads. Comparison of the factors and pipe lifetime estimation is carried out.

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He, Jia Sheng, Meng Qi Yan, and Xiao Ming Zhu. "The Numerical Analysis and Experimental Study of the Stress Intensity Factor and Outer Surface Strain of the Pressure Pipe with Internal Longitudinal-Cracks." Applied Mechanics and Materials 853 (September 2016): 221–25. http://dx.doi.org/10.4028/www.scientific.net/amm.853.221.

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The strain characteristics in the outer surface of the pipe and the stress intensity factor in crack front with internal longitudinal-cracks were analyzed by the finite element method. According to the results of analysis, the outer surface strain variation to crack size was got and the relationship of stress intensity factor and crack size was known. Based on resistance strain gauges and fiber optic sensing technology, pressure pipe crack extension monitoring device was designed and the outer surface circumferential strain were tested .The results of finite element analysis and experiment are in good agreement. The outer surface strain variation in this paper can be used to analyze the situation of internal longitudinal-cracks extension.That relationship of stress intensity factor and crack size has an important reference to the safety assessment of pipe with internal longitudinal-crack.

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Zitouni, T. A., and Z. Labed. "Numerical Study on Dimensions and Orientation Effect of Semi-Elliptical Cracks in PE100 Pipelines." International Journal of Applied Mechanics and Engineering 26, no. 3 (August 26, 2021): 198–207. http://dx.doi.org/10.2478/ijame-2021-0045.

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Abstract The through-thickness crack or surface crack in PE100 pipes subjected to internal pressure represents a serious risk to the structural integrity of HDPE pipes, which has attracted wide attention in modern industry. Although experimental research offers reliable predictions of surface crack influence on pipes, the relatively high cost hinders its application. The numerical simulation, as a cost-effective alternative, has been widely applied to assess stress displacement and strain to the entire pipe structure. This is the initial approach adopted in recent decades. This article provides simulations tests of an uncracked pipe and cracked PE100 pipe under different internal pressure values, with varying each time the dimensions of the crack with 1 mm rate for minor and major radius and 0.5mm rates for the largest contour radius, using ANSYS MECHANICAL STRUCTURAL STATIC for simulation.

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Hosseini-Toudeshky, Hossein, and Mir Ali Ghaffari. "A Simple Method to Estimate the Fatigue Crack Growth Life of Repaired Pipes with Composite Patches." Applied Mechanics and Materials 152-154 (January 2012): 387–92. http://dx.doi.org/10.4028/www.scientific.net/amm.152-154.387.

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In this paper, a simplified method is performed to predict the fatigue crack growth life of repaired pipes by glass/epoxy composite patches. For this purpose, an already developed automatic procedure by the authors is adapted to handle 3D crack growth analyses of repaired pipes subjected to internal cyclic pressure. The analyses are performed for offshore pipes made of low-strength steel containing an initial fatigue corrosion crack and repaired by glass/epoxy composite patch. Finally, an equation is presented here suggesting a point along the thickness of a repaired pipe in which, the calculated fatigue crack growth life based on the fracture parameters of that point in a simple uniform crack growth modeling along the pipe thickness (UCG) is almost equal to the calculated fatigue life in non-uniform crack growth analysis (NUCG) or a real crack-front modeling approach.

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Rajab, M. D., and A. Zahoor. "Crack Instability in Pipes Containing Internal Surface Flaw." Journal of Engineering Materials and Technology 111, no. 3 (July 1, 1989): 243–47. http://dx.doi.org/10.1115/1.3226462.

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Crack associated pipe axial displacement and tearing modulus solutions are derived for pipes containing internal circumferential part-through wall surface flaw under axial tension loading. The tearing modulus solution is derived for both load control and displacement control loadings. The solutions are useful for practical applications involving contained yielding in the crack section. The analytical solutions can be readily applied to pipe radius-to-thickness ratio ranging from 5 to 20. A sensitivity study was performed to assess the influence of flaw size, pipe radius and wall thickness, pipe length, and axial tension load on the applied tearing modulus. Numerical results are presented for critical stress as a function of flaw size for 4130 carbon steel pipe.

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Edmund, Jonathan Emmanuel, and Zahiraniza binti Mustaffa. "Numerical Analysis of Crack Failure of Reinforced Thermoplastic Pipe (RTP)." MATEC Web of Conferences 203 (2018): 01023. http://dx.doi.org/10.1051/matecconf/201820301023.

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Composite pipeline can drastically reduce losses caused by corrosion that occurs in carbon steel pipes in the industry. Multiple numerical testing has been conducted to determine maximum stress and strain a Reinforced Thermoplastic Pipe (RTP) can withstand before hitting failure. Not many studies were done to find the maximum stress intensity a defected RTP can resist before failing. Objectives are to validate the numerical model for Reinforced Thermoplastic Pipeline (RTP) to industry standard and to analyze the maximum stress intensity of Reinforced Thermoplastic Pipes (RTP) can withstand with various size of defects under constant pressure and incremental internal pressure with constant crack defect. Results were, under constant internal pressure of 6 MPa, the pipe will fail with a defect length of 2.05mm and at constant design pressure of 10 MPa, the pipe will fail with a defect length of 0.3mm. At constant crack depth and width, crack tip propagation (failure) is more dependent on internal pressure rather than crack length. However, when comparing the severity of crack depth to internal pressure, crack depth is the major cause of failure.

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Lee, Kuang Chyi, Yuan Cheng Liang, and Chien Chang Lin. "Analysis for Repairing the Cracked PVC Pipe." Materials Science Forum 505-507 (January 2006): 565–70. http://dx.doi.org/10.4028/www.scientific.net/msf.505-507.565.

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This paper proposes a stress analysis model for the cracked PVC pipe. The cracked PVC pipe is rehabilitated with an inner composite epoxy material by a dig-free method. The optimal thickness which can get the maximal flow rate after rehabilitated will be found by the finite element model. When the crack width of the pipe with 324 degree crack angle is 30 mm, the optimal thicknesses will be obtained with the compression ratio of 5%. The optimal thicknesses of theφ 300 ,φ 400 , φ 500 and φ 600 PVC pipes are 0.6, 0.8, 1.1 and 2.5 mm respectively. With these optimal thicknesses, the flow rates of rehabilitated pipes are lager than 98% the flow rates of original pipes.

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Hutař, Pavel, Martin Ševčík, Ralf Lach, Zdeněk Knésl, Luboš Náhlík, and Wolfgang Grellman. "A Description of Local Material Properties Close to a Butt Weld." Key Engineering Materials 586 (September 2013): 146–49. http://dx.doi.org/10.4028/www.scientific.net/kem.586.146.

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The paper presents a methodology for the lifetime assessment of welded polymer pipes. A fracture mechanics analysis of a butt-welded joint is performed by simulating radial crack growth in the nonhomogenous region of the pipe weld. It was found that the presence of material nonhomogeneity in the pipe weld caused by the welding procedure leads to an increase in the stress intensity factor of the radial crack and changes the usual failure mode of the pipe system. This can lead to a significant reduction in the lifetime of the pipe system.

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Bai, H., A. H. Shah, N. Popplewell, and S. K. Datta. "Scattering of Guided Waves by Circumferential Cracks in Steel Pipes." Journal of Applied Mechanics 68, no. 4 (September 15, 2000): 619–31. http://dx.doi.org/10.1115/1.1364493.

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A novel numerical procedure is presented in this paper to study wave scattering problem by circumferential cracks in steel pipes. The study is motivated by the need to develop a quantitative ultrasonic technique to characterize properties of cracks in pipes. By employing wave function expansion in axial direction and decomposing the problem into a symmetry problem and an antisymmetry problem, a three-dimensional wave scattering problem is then reduced into two quasi-one-dimensional problems. This simplification greatly reduces the computational time. Numerical results for reflection and transmission coefficients of different incident wave modes are presented here for a steel pipe with cracks (may have arbitrary circumferential crack length and radial crack depth) and they are shown to agree quite closely with available but limited experimental data.

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Khaled, Ali Jamal, and Ahmed Abdul Hussain. "Crack Growth Behavior through Wall Pipes under Impact Loading And Moisten Environment." Journal of Engineering 25, no. 1 (December 30, 2018): 1–12. http://dx.doi.org/10.31026/j.eng.2019.01.01.

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This search concerns study the crack growth in the wall of pipes made of low carbon steel under the impact load and using the effect of moisture (rate of moisture 50%). The environmental conditions were controlled using high accuracy digital control with sensors. The pipe has a crack already. The test was performed and on two type of specimens, one has a length of 100cm and other have length 50cm. The results were, when the humidity was applied to the pipe, the crack would enhance to grow (i.e. the number of cycles needed to grow the crack will reduce). In addition, when the test performed on the specimens of length 50cm the number of cycles needed to grow the crack is increased due to the effect of bending stress on the pipes.

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Chua, Chien An, and Peter Cawley. "Crack growth monitoring using fundamental shear horizontal guided waves." Structural Health Monitoring 19, no. 5 (October 23, 2019): 1311–22. http://dx.doi.org/10.1177/1475921719882330.

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Monitoring cracks in critical sections of steel structures is a topic of growing interest. Existing high-frequency ultrasonic techniques have good detection sensitivities but poor inspection coverage, requiring an impractical number of transducers to monitor large areas. Low-frequency guided waves are used for corrosion detection in pipelines but are insufficiently sensitive for many crack detection applications. The sensitivity can be improved using higher frequencies and by placing the receiving transducers closer to the defect. This study evaluates the monitoring performance of an SH0 mode system at frequencies just below the high-order mode cut-off. Baseline subtraction with temperature compensation was applied to experimental data generated by a ring of transducers on a 6-in diameter pipe. It was found that the residual signals after baseline subtraction were normally distributed so the random fluctuations could be reduced by coherent averaging; it was thereby possible to reliably detect a 2 mm × 1 mm notch simulating a crack located one pipe diameter along the pipe from the transducer ring. The damage detection performance at different locations along the pipe was assessed by analysing receiver operating characteristic curves generated by adding simulated defects to multiple experimental measurements without damage. At a fixed standoff distance, the damage detection performance increases with the square root of the number of averaged signals and is also improved by averaging the signals received by transducers covering the main lobe of the reflection from the defect. When the defect is located more than about one pipe circumference from the transducer ring, the optimal performance is obtained by averaging across all the transducers in the ring, corresponding to monitoring the T(0,1) pipe mode. Therefore, an SH0 mode monitoring system has great potential for crack monitoring applications, particularly for welds in pipes.

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Liang, Wen Fu, Tong Liu, and Min Shan Liu. "Three-Dimensional Leak before Break Analysis of Nuclear Pipes Containing Cracks." Applied Mechanics and Materials 750 (April 2015): 376–81. http://dx.doi.org/10.4028/www.scientific.net/amm.750.376.

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Three-dimensional crack behavior simulation analysis and anti-fracture design have been a main subject in fracture theory and engineering application. Piping system is a key part of nuclear power engineering. Utilizing the three-dimensional finite element analysis software ANSYS and the specialized crack analysis programs Franc3D, three-dimensional crack behavior and leak before break (LBB) case were simulated and evaluated of a pipe with a crack in waste heat exhaust system of China Experimental Fast Reactor ( CEFR ). In fast reactor, the piping is working under a high temperature. Therefore, the code RCC-MR.A16 was adopted that is suitable for materials and structural safety design at high temperature. Material used in this article is modified 9Cr1Mo-T91/P91. The analysis model of pipe section was built in three-dimensional entity structure containing a cracks and the high temperature and creep effects were considered. The simulation results show that creep contributes more effect on crack growth than fatigue. The evaluation results on LBB of studied T91 steel pipe with a crack-like defect can satisfy the need of LBB design guidelines. The research results can be referenced in pipe material choose, safety assessment and structural integrity evaluation of a pipe containing defects at high temperature in a fast reactor design.

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Su, Lin, Jie Xu, Wei Song, Lingyu Chu, Hanlin Gao, Pengpeng Li, and Filippo Berto. "Numerical Investigation of Strength Mismatch Effect on Ductile Crack Growth Resistance in Welding Pipe." Applied Sciences 10, no. 4 (February 18, 2020): 1374. http://dx.doi.org/10.3390/app10041374.

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The effect of strength mismatch (ratio between the yield stress of weld metal and base metal, My) on the ductile crack growth resistance of welding pipe was numerically analyzed. The ductile fracture behavior of welding pipe was determined while using the single edge notched bending (SENB) and single edge notched tension (SENT) specimens, as well as axisymmetric models of circumferentially cracked pipes for comparison. Crack growth resistance curves (as denoted by crack tip opening displacement-resistance (CTOD-R curve) have been computed using the complete Gurson model. A so-called CTOD-Q-M formulation was proposed to calculate the weld mismatch constraint M. It has been shown that the fracture resistance curves significantly increase with the increase of the mismatch ratio. As for SENT and pipe, the larger My causes the lower mismatch constraint M, which leads to the higher fracture toughness and crack growth resistance curves. When compared with the standard SENB, the SENT specimen and the cracked pipe have a more similar fracture resistance behavior. The results present grounds for justification of usage of SENT specimens in fracture assessment of welding cracked pipes as an alternative to the traditional conservative SENB specimens.

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29

Zouhar, Michal, Pavel Hutař, Martin Ševčík, and Luboš Náhlík. "Pressure Pipe Damage: Numerical Estimation of Point Load Effect." Key Engineering Materials 525-526 (November 2012): 177–80. http://dx.doi.org/10.4028/www.scientific.net/kem.525-526.177.

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The most relevant loading conditions for real polymer pipe systems are not only internal pressure, but also loading caused by sand embedding including bending or different kinds of point loads. It has been shown that service lifetime of buried pipes can be reduced especially due to stress concentration caused by external point loads. If the pipe is loaded locally the stress is concentrated here and a crack can initiate at this position or the existing crack can be affected by corresponding stress redistribution. In the paper the effect of the hard indenter, Poissons ratio, hoop stress level and pipe wall thickness on the crack shape was estimated using numerical simulations of the creep crack propagation based on finite element method. Relation between crack length and crack width was found and expressed by simple relationship. A deeper understanding of the point load effect in order to prevent unexpected failure of the pipelines is of paramount importance for pipeline design.

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30

Wan, Xiong. "Simulation and Experimental Analysis of the Infrared Detection for Surface Cracks of Metal Pipes with Penetration Treatment." Applied Mechanics and Materials 719-720 (January 2015): 238–42. http://dx.doi.org/10.4028/www.scientific.net/amm.719-720.238.

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Working in the corrosive environment for a long time, it is easy for metal pipes to produce stress corrosion cracks which will affect the use. An infrared detection method combining permeate treatment with heat-incentive steam is proposed to detect surface cracks, which then has been verified by simulations and experiments. For the simulation, pipe model including four cracks of different depth and width was constructed by ANSYS. Transient thermal analysis was made after convection incentive loaded on internal and external wall in the case of whether or not undergo surface infiltration processing. For the experiment, pipe including cracks were made the same as simulation parameters, then experiments were made using the thermal excitation system in two cases. Surface temperature distributions of the pipe were compared in two cases, the results of the study show that penetration treatment before heat incentive can significantly improve the surface crack detection sensitivity.

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31

Kelemenová, Tatiana, František Duchoň, Michal Puškár, Michal Kelemen, Piotr Kuryło, Erik Prada, and Tomáš Lipták. "Influence of Pipe Geometric Deviations on In-Pipe Machine Locomotion." Applied Mechanics and Materials 611 (August 2014): 221–26. http://dx.doi.org/10.4028/www.scientific.net/amm.611.221.

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The paper deals with the analysis of influence of pipe deviations on in-pipe machine locomotion. In-pipe machine locomotes inside a pipe using the friction difference principle of locomotion. Main task of the machine is inspection of inner pipe wall as the prevention of pipe crack and leaks of transported medium. Pipe systems have deviations of inner pipe wall, which are caused by production process and caused by using of pipe (deformations, sediments, changes from coupling of pipes etc.). These pipe deviations have direct influence on machine locomotion inside the pipe.

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32

Horn, R. M. "Evaluation of Crack Growth in Oxygenated High Temperature Water Using Full Size Pipe Tests." Journal of Engineering Materials and Technology 108, no. 1 (January 1, 1986): 50–56. http://dx.doi.org/10.1115/1.3225841.

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Full Size pipe tests have been conducted as part of EPRI research programs at the General Electric Company to verify IGSCC crack growth predictions made using a linear elastic fracture mechanics model. The tests on 10.16 cm (4″ pipes) were performed in oxygenated, high temperature, high purity water. The pipes were produced through standard manufacturing procedures which in turn led to characteristic field piping sensitization levels in the heat affected zones (HAZ) and characteristic through wall weld residual stresses. The tests were conducted at stresses equal to or below the yield strength under constant load with limited cycling. Ultrasonic inspection and metallography were used to characterize crack depth after several test phases and used to verify model predictions. Significant cracks were detected and radial and circumferential growth were documented. These test results support the predictions made using linear elastic fracture mechanics modeling, and are discussed in terms of crack growth data developed in CT specimens in the laboratory. The stress level and oxygen level are shown to influence the crack growth rates. Rates of circumferential crack growth are also evaluated. The paper discusses the results in the context of other stress corrosion evaluations as well.

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33

Khaled, Ali Jamal, and Ahmed Abdul Hussain. "Crack Growth Behavior through Wall Pipes under Impact Load and Hygrothremal Environment." Al-Khwarizmi Engineering Journal 14, no. 4 (December 1, 2018): 9–15. http://dx.doi.org/10.22153/kej.2018.05.001.

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This research concerns study the crack growth in the wall of pipes made of low carbon steel under the impact load and using the effect of hygrothermal (rate of moisture 50% and 50℃ temperature). The environmental conditions were controlled using high accuracy digital control with sensors. The pipe have a crack already. The test was performed and on two type of specimens, one have length of 100cm and other have length 50cm. The results were, when the humidity was applied to the pipe, the crack would enhance to growth (i.e. the number of cycles needed to growth the crack will reduce). In addition, when the temperature was increase the number of cycles needed to growth the crack are reduced because the effect of heat on the mechanical properties of the material. In addition, when the test performed on the specimens of length 50cm the number of cycles needed to growth the crack is increase because the effect of bending stress on the pipes.

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34

Zahoor, A. "Closed Form Expressions for Fracture Mechanics Analysis of Cracked Pipes." Journal of Pressure Vessel Technology 107, no. 2 (May 1, 1985): 203–5. http://dx.doi.org/10.1115/1.3264435.

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Closed form stress intensity factor (K1) expressions are presented for cracks in pipes subjected to a variety of loading conditions. The loadings considered are: 1) axial tension, 2) remotely applied bending moment, and 3) internal pressure. Expressions are presented for circumferential and axial cracks, and include both part-through and through-wall crack geometries. The closed form K1 expressions are valid for pipe radius to wall thickness ratio between 5 and 20.

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35

Husaini, Nurdin Ali, Teuku Edisah Putra, Faleri Armia, and Akhyar. "Study on Fracture Failures of the Super Heater Water Pipe Boiler." Defect and Diffusion Forum 402 (July 2020): 20–26. http://dx.doi.org/10.4028/www.scientific.net/ddf.402.20.

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The purpose of this study was to analyse the failure of the super heater pipe of the Heat Recovery Steam Boiler Generator (HRSG), which had broken. Investigations are carried out in several stages. First of all, the microstructure of the pipe was observed using an Optic Olympus GX71 Microscope and a Scanning Electron Microscope (SEM) was used to observe the fracture surface to find the initial crack. Thereafter, chemical composition testing, to determine the type of material used in the super heater pipe. The presence of deformation by creep was due to overheating seen on the super heater pipes. Moreover, It was due to operating at elevated temperatures and pressures with long operating times. This condition caused the thickness of the pipe to thin so that it would break due to crack propagation which penetrated the wall of the pipe until breaking as the material was no longer able to withstand the steam pressure inside the pipe. Obviously that this condition indicates that the crack propagation occurred until final failure.

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36

Kessai, Idir, Samir Benammar, Mohamed Zinelabidine Doghmane, and Kong Fah Tee. "Estimation of Circular Arc Crack Depths and Locations in Rotary Drilling Pipes Subjected to Free Vibrations." Vibration 5, no. 1 (March 4, 2022): 165–82. http://dx.doi.org/10.3390/vibration5010011.

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Late detection of cracks can lead to serious failures and damages of drilling components, especially drill pipes and drill bits. Currently, the widely used method of repairing rotary drilling systems after a failure is corrective maintenance. Although this strategy has shown its effectiveness in many cases, waiting for a failure to occur and then performing a repair can be an expensive and time-consuming operation. Thus, the use of preventive maintenance under the aspect of periodic inspections can solve this problem and help engineers detect cracks before they reach critical sizes. In this study, modal analysis and finite element analysis (FEA) combined with artificial neural networks (ANN) were used to dynamically estimate the depth and location of a circular arc crack in the drill pipes of rotary drilling systems. To achieve this goal, a detailed analytical approach based on Euler–Bernoulli beam theory was adopted to validate the first four natural frequencies found by FEA for an undamaged pipe. Afterwards, an arc crack was assigned to the pipe already created using Abaqus, and the first four natural frequencies were obtained for each depth and location of the crack. Simulations with FEA led to the generation of a dataset with two inputs—depth and location of cracks—and four outputs: natural frequencies. Moreover, a multilayer perceptron (MLP) was designed and trained by the data collected from simulations. Finally, a comparison between the results obtained by FEA and ANN was performed, where both approaches showed a good agreement in predicting the depth and location of cracks.

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37

Zhang, Hong Tao, Xiao Xiang Xue, Yan Zheng, and Peng Feng. "Using CFRP to Repair the Steel Pipe with Fatigue Cracks." Advanced Materials Research 146-147 (October 2010): 1086–89. http://dx.doi.org/10.4028/www.scientific.net/amr.146-147.1086.

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This paper provides a new method to repair the steel pipe with fatigue cracks by using carbon fiber reinforced polymer (CFRP). Cracks may arise in Pressure pipeline in service because of low cycle fatigue. Crack defect is the biggest problem, because crack will gradually propagate and seriously threaten the safe operation of pipeline. This paper provides a repair and calculation method for pressure pipeline with fatigue cracks, and some specific engineering cases are given based on this method.

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38

Khoramishad, Hadi, and Majid Reza Ayatollahi. "FINITE ELEMENT ANALYSIS OF A SEMI-ELLIPTICAL EXTERNAL CRACK IN A BURIED PIPE." Transactions of the Canadian Society for Mechanical Engineering 33, no. 3 (September 2009): 399–409. http://dx.doi.org/10.1139/tcsme-2009-0028.

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In this research, a buried pipe containing an external semi-elliptical crack has been modeled and investigated using finite element analysis. The interaction between the soil and pipe has been considered according to the Burns and Richard model. A few major parameters, namely, the soil height over pipe, the geometries of pipe and crack and the circumferential position of crack on pipe have been changed and their effects on elastic stress intensity factors have been studied at different positions along the crack front. The results showed that the crack experienced mixed mode loading condition and the circumferential crack position on pipe had a significant influence on the stress intensity factors.

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39

Mechab, Belaïd, Medjahdi Malika, Mokadem Salem, and Serier Boualem. "Probabilistic Elastic-plastic Fracture Mechanics Analysis of Propagation of Cracks in Pipes under Internal Pressure." Frattura ed Integrità Strutturale 14, no. 54 (September 23, 2020): 202–10. http://dx.doi.org/10.3221/igf-esis.54.15.

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This study presents a three dimensional finite element method analysis of semi-elliptical surface cracks in pipes under internal pressure load. In the elastic–plastic case, estimates of the J-integral are presented for various ratios including crack depth to pipe thickness (a/t) and strain hardening index in the (R-O) Ramberg-Osgood (n). Finally, failure probability is accessed by a statistical analysis for uncertainties in loads and material properties, and structural reliability and crack size. The Monte Carlo method is used to predict the distribution function of the mechanical response. According to the obtained results, we note that the stress variation and the crack size are important factors influencing on the distribution function of (J/Je).

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40

Yan, Shi, Ji Qi, Nai Zhi Zhao, Yang Cheng, and Sheng Wen Jun Qi. "Multiple Crack Detection of Pipes Using PZT-Based Guided Waves." Applied Mechanics and Materials 448-453 (October 2013): 3702–8. http://dx.doi.org/10.4028/www.scientific.net/amm.448-453.3702.

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This paper focuses on the multiple crack detection of steel pipelines using PZT-based guided waves. Numerical simulations of cracked pipes based on ultrasonic guided-waves are conducted by using the ANSYS finite element software. Based on the analysis of the reflected signal, the arrival time of the crack reflection waves are determined and the crack positions are accurately evaluated by the calculation of the travel time and group velocity of the PZT-based guided waves. The crack parameters are numerically altered to determine how the parameters impact the sensitive degree of the pipe crack damage. To validate the efficiency of the numerical simulation, an experiment of the multiple crack detection for the same parameter pipe with the numerical model is performed in the laboratory, and the results match well with the numerical simulation.

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41

Li, Chun Qing, Guo Yang Fu, and Shang Tong Yang. "Elastic Fracture Toughness for Ductile Metal Pipes with Circumferential Surface Cracks." Key Engineering Materials 730 (February 2017): 489–95. http://dx.doi.org/10.4028/www.scientific.net/kem.730.489.

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Surface cracks have long been recognized as a major cause for potential failures of metal pipes. In fracture analysis, the widely used method is based on linear elastic fracture mechanics. However, for ductile metal pipes, it has been known that the existence of plasticity results in easing of stress concentration at the crack front. This will ultimately increase the total fracture toughness. Therefore, when using linear elastic fracture mechanics to predict fracture failure of ductile metal pipes, the plastic portion of fracture toughness should be excluded. Otherwise, the value of fracture toughness will be overestimated, resulting in an under-estimated probability of failure. This paper intends to derive a model of elastic fracture toughness for steel pipes with a circumferential crack. The derived elastic fracture toughness is a function of crack geometry and material properties of the cracked pipe. The significance of the derived model is that the well-established linear elastic fracture mechanics can be used for ductile materials in predicting the fracture failure.

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42

Likeb, Andrej, and Nenad Gubeljak. "The Determination of the Limit Load Solutions for the New Pipe-Ring Specimen Using Finite Element Modeling." Metals 10, no. 6 (June 5, 2020): 749. http://dx.doi.org/10.3390/met10060749.

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To estimate the acceptable size of cracks and predict the loading limit of the pipeline or its resistance to the initiation and crack growth by following the structural integrity, the fracture toughness and limit load solutions are required. Standard fracture toughness testing of thin-walled pipelines is often difficult to perform in order to complete standard requirements. To find an alternative technique for the measurement of the fracture toughness of the already delivered pipeline segment, the new pipe-ring specimen has been proposed; however, the limit load solutions have not been investigated yet. The limit load depends on the geometry of the specimen and loading mode. The ligament yielding of pipe-ring specimens containing axial cracks through the thickness under combined loads was calculated by the finite element method. This paper provides limit load solutions of several different pipe-ring geometries containing two diametric symmetrical cracks with the same depth ratio in a range of 0.45 ≤ a/W ≤ 0.55. The limit load (LL) solutions calculated by numerical analysis are shown as a function of the full ring section’s size and the corresponding crack aspect ratio for determining the normalized load. These can potentially construct the failure assessment diagram to estimate the crack acceptance in a part of the pipe.

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43

Xu, Jie, Xiao Min Zhuo, Peng Peng Li, Yu Fan, and Zhi Sun. "Constraint Effect on the Ductile Fracture Behavior of High-Strength Pipeline Steels." Materials Science Forum 850 (March 2016): 899–904. http://dx.doi.org/10.4028/www.scientific.net/msf.850.899.

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This work presents an investigation of the ductile tearing properties for a pipe with internal and external circumferential cracks using 2D plane strain and axisymmetric models. Crack growth resistance curves were computed using the complete Gurson model. The pipes with various crack depths and internal pressures were analyzed. The results were compared with those of corresponding SENT and SENB specimens. It clearly indicated a significant effect of constraint on the resistance curves for internal and external cracked pipes. A minor effect of hoop stress induced by internal pressure on the CTOD-resistance curves is expected for deep-cracked pipes. The SENT specimen is a better representation of circumferentially flawed pipes and an alternative to the conventional standard SENB specimen for the fracture mechanics testing in engineering critical assessment of high-strength pipeline steels.

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44

Benyahia, F., A. Albedah, Bel Abbès Bachir Bouiadjra, and M. Belhouari. "A Comparison Study of Bonded Composite Repairs of Through-Wall Cracks in Pipes Subjected to Traction, Bending Moment and Internal Pressure." Advanced Materials Research 1105 (May 2015): 41–45. http://dx.doi.org/10.4028/www.scientific.net/amr.1105.41.

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In this study, a finite element analysis of the crack repair with composite wrap of circumferential through cracks in pipes subjected to bending moment is presented. Also, the evaluation of the long-term performance of composite repair systems has been addressed. The stress intensity factor is utilized as a fracture criterion. Finally, an attempt was made to provide industry with an overview of the current state of the art in composite repair technology and how the integrity of pipeline systems is being restored using composite materials. The obtained results show that the presence of the bonded composite repair reduces significantly the stress intensity factor, which can improve the residual fatigue life of the pipe. However, the main disadvantage of the technique of bonded composite repair in pipe is the impossibility to bond double sided composite wrap in order to equilibrate the stress transfer between the internal and external crack tip

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45

Sparks, Ross, and Andrew Kasmarik. "Monitoring Deterioration in a Catchment’s Sewerage System." Open Civil Engineering Journal 7, no. 1 (October 31, 2013): 149–58. http://dx.doi.org/10.2174/1874149501307010149.

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Groundwater seepage through cracks in the sewerage pipeline is a major maintenance issue in most cities’ sewer networks. The more the sewer pipes crack – and the wider these cracks are – the worse the rainfall seepage problem becomes. The total volume of rainwater seepage into the sewer pipes for a catchment is correlated with deterioration and can therefore be used to estimate the rate of deterioration. This paper describes a monitoring system that can be used to identify significant trends in sewer deterioration. Effective monitoring by asset managers can highlight the need for early maintenance such as removing tree roots from pipe cracks and patching the cracks.

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46

Zhuang, W., A. H. Shah, and S. K. Datta. "Axisymmetric Guided Wave Scattering by Cracks in Welded Steel Pipes." Journal of Pressure Vessel Technology 119, no. 4 (November 1, 1997): 401–6. http://dx.doi.org/10.1115/1.2842322.

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Scattering of axisymmetric guided waves by cracks and weldments of anisotropic bonding material in welded steel pipes is investigated in this paper by a hybrid method employing finite element and modal representation techniques. The study is motivated by the need to develop a quantitative ultrasonic technique to distinguish flaws and bonding materials in welded cylindrical structures. Numerical results for reflection coefficients are presented for a steel pipe with cracks and V-shaped weldments with and without cracks at the interface between the weldment and the steel pipe. It is shown that as the frequency increases, the coefficients of reflection exhibit resonant peaks at the cutoff frequencies of higher guided modes. These peaks become increasingly pronounced as the slope and the length of the crack increase. Numerical results presented have important applications in quantitative nondestructive evaluation.

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47

Shehadeh, Mohamed, Ahmed Osman, Aly Abdelbaky Elbatran, John Steel, and Robert Reuben. "Experimental Investigation Using Acoustic Emission Technique for Quasi-Static Cracks in Steel Pipes Assessment." Machines 9, no. 4 (March 29, 2021): 73. http://dx.doi.org/10.3390/machines9040073.

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Acoustic emission (AE) is a phenomenon where transient waves of stress are generated during deformed material, which is applied to detect and monitor the cracks and cracks propagation. The majority of related literature studied simulated wave sources, which were utilized for a single point of a pipe and have been strictly controlled by temporal characteristics. Therefore, the realistic wave sources which do not have known temporal characteristics are studied in the present work. The realistic source is quasi-static crack propagation under three-point bending. The distortions of AE signals are experimentally evaluated by testing the AE signals of crack propagation using simulated sources. A variety of stress intensities are applied on a steel pipe to determine the effect of stress type and intensity on the characteristics of the source using time and frequency domains. Machines are mounted on the steel pipe to locate and reconstitute the features of time and frequency domain of the AE sources. It is concluded that the AE energy was sensitive to the crack size which was concerning to the transition of plane-stress to plane-strain. The potential of AE technique for identifying the nature, intensity and location of crack propagation is demonstrated.

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48

Majer, Zdeněk, Martin Ševčík, Luboš Náhlík, and Pavel Hutař. "Point Load Effect Determination for Different Pressure Pipe SDR Series." Key Engineering Materials 627 (September 2014): 373–76. http://dx.doi.org/10.4028/www.scientific.net/kem.627.373.

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In the paper the polymer pipes loaded by internal pressure with additional point load on the external surface are studied using numerical methods. It is shown that the additional external loading can significantly influence residual lifetime of the pressured pipe. In this study the effect of the pipe geometry is considered. The shape of the propagating crack is estimated based on a special algorithm and the stress intensity factor is evaluated by direct method. The relation between crack size and a geometric function YasYas for specific material and geometrical properties is found. The results of this paper should contribute to better understanding of the real pipe behavior and to prevent unexpected failure of the pressured pipe system due to non-homogenous distribution of the soil load.

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Xue, Feng Mei, Fu Guo Li, Jiang Li, Wen Jun Yu, and Jian Fei Li. "Fracture Analysis of Pipe Sleeve on Extrusion Flare-Less Pipe Joints for Aircraft Hydraulic Pipe." Advanced Materials Research 291-294 (July 2011): 1087–90. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.1087.

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The forming process of aircraft hydraulic pipe joints is investigated through experiments and analyses to solve the cracking problem of pipe sleeve on extrusion flare-less pipe joints. It can be concluded that the internal cause of the fracture failure is connected with the content, shape and distribution of δ-ferrite in 0Cr12Mn5Ni4Mo3Al high strength stainless steel, and the external cause is associated with the bearing behavior in the extrusion-bulging process of pipe sleeve. The crack is formed in the criss-crossing section of δ-ferrite on the function of shear stress in the stress concentration position, which belongs to ductile deformed crack. It eventually induces the intergranular fracture of pipe sleeve along the long axis with the expanding of subsequent crack.

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Li, Zongchen, Xiaoli Jiang, and Hans Hopman. "Surface Crack Growth in Offshore Metallic Pipes under Cyclic Loads: A Literature Review." Journal of Marine Science and Engineering 8, no. 5 (May 10, 2020): 339. http://dx.doi.org/10.3390/jmse8050339.

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The surface crack, also known as the partly through-thickness crack, is a serious threat to the structural integrity of offshore metallic pipes. In this paper, we review the research progress in regard to surface crack growth in metallic pipes subjected to cyclic loads from the fracture mechanics perspective. The purpose is to provide state-of-the-art investigations, as well as indicate the remaining challenges. First, the available studies on surface cracked metallic pipes are overviewed from experimental, numerical, and analytical perspectives, respectively. Then, we analyse state-of-the-art research and discuss the insufficiencies of the available literature from different perspectives, such as surface cracks and pipe configurations, environmental influential parameters, the girth welding effect, and numerical and analytical evaluation methods. Building on these surveys and discussions, we identify various remaining challenges and possible further research topics that are anticipated to be of significant value both for academics and practitioners.

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Journal articles on the topic 'Crack in pipe'

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