Hydraulic Burst Tests Research Articles

Robust instrumentation of composite pressure vessels manufactured via multi-filament winding for distributed fiber optic sensing

The development of hydrogen storage and transport technologies with safety, efficiency and economy is one of the main scientific and technological challenges to stablish the infrastructure for a hydrogen economy. The storage must not only be lightweight and compact but also safe, cost-effective, long-range and rapidly refuellable. Type IV composite pressure vessels have been recognized as a cost-efficient solution that can address these problems for on-board storage in the hydrogen-powered mobility and hydrogen transport in tube trailers. The demanding working environment presents a challenge to the failure analysis and predictive maintenance of composite pressure vessels; the knowledge of the precise condition of the pressure vessel is therefore mandatory to guarantee safety usage. The continuous strain monitoring of composite pressure vessels via distributed fiber optic sensors (DFOS) can enable the implementation of a structural health monitoring system. The robust instrumentation of composite pressure vessels with DFOS is here presented; the pressure vessel manufacture is based on the multi-filament winding. Small pressure vessel prototypes are designed and manufactured using carbon fibers as reinforcement; DFOS are integrated into the cylindrical section composite laminate during winding. A connector housing is placed on the dome section of the pressure vessel to protect sensor exit/entry points. The condition of the integrated DFOS is assessed throughout manufacture (winding and consolidation) via optical time domain reflectometry (OTDR). Afterwards, hydraulic burst tests are performed with step-wise pressure increments and the strain evolution and failure are monitored via distributed strain sensing. The integrated DFOS are capable of monitoring the strain evolution over the length of the vessel for the circumferential direction.

Finite element analysis and experimental validation of the failure characteristic of pressurized cylinder

PurposeThe high-pressure accumulator has been widely used in the hydraulic system. Failure pressure prediction is crucial for the safe design and integrity assessment of the accumulators. The purpose of this study is to accurately predict the burst pressure and location for the accumulator shells due to internal pressure.Design/methodology/approachThis study concentrates the non-linear finite element simulation procedure, which allows determination of the burst pressure and crack location using extensive plastic straining criterion. Meanwhile, the full-scale hydraulic burst test and the analytical solution are conducted for comparative analysis.FindingsA good agreement between predicted and measured the burst pressure that was obtained, and the predicted failure point coincided very well with the fracture location of the actual shell very well. Meanwhile, the burst pressure of the shells increases with wall thickness, independent of the length. It can be said that the non-linear finite element method can be employed to predict the failure behavior of a cylindrical shell with sufficient accuracy.Originality/valueThis paper can provide a designer with additional insight into how the pressurized hollow cylinder might fail, and the failure pressure has been predicted accurately with a minimum error below 1%, comparing the numerical results with experimental data.

Experimental Study of Curing Temperature Effect on Mechanical Performance of Carbon Fiber Composites with Application to Filament Winding Pressure Vessel Design.

During the forming process of carbon fiber composite pressure vessels, the parameters of the curing and forming processes become one of the critical factors affecting the production cost and forming quality. The curing temperature of 4251 A4/B2 epoxy resin is measured in this research, and the effect of curing temperature on the mechanical properties of composite materials for winding is studied, which is finally verified in the test of pressure vessels. First, the actual curing temperature of the epoxy resin is tested and analyzed using differential scanning calorimetry (DSC). Second, under two different curing regimes, the tensile and flexural properties are tested by making pure epoxy resin matrix test pieces, Naval Ordnance Laboratory (NOL) rings, and carbon fiber composite unidirectional plates that affect the overall performance of composite pressure vessels. At the same time, the test results provide reliable process parameters for numerical simulation and manufacturing of pressure vessels. Finally, the filament-wound 35 MPa type III pressure vessel is cured and carried out using a hydraulic burst test. The results show the resin matrix has good fluidity and excellent interface bonding with carbon fiber when the curing temperature is 112 °C. Compared with the results in curing temperature of 100 °C, the tensile strength of the NOL ring reaches 2260.8 MPa, up by 22%. In the 90° direction, the tensile and flexural strengths of the unidirectional plates increase by 68.86% and 37.42%, respectively. In the 0° direction, the tensile and flexural strengths of the unidirectional plates increase by 5.82% and 1.16%, respectively. The pressure vessel bursting form is reasonable and meets the CGH2R standard. The bursting pressure of the vessel is up to 104.4 MPa, which verifies the rationality of the curing regime used in the curing process of the pressure vessel. Based on the results of this paper, the curing temperature affects the fluidity of the epoxy resin, which in turn affects the interfacial bonding properties of the composite, and the forming quality of the wound components and the pressure vessel, ultimately. When using 4251A4/B2 epoxy resin for wet winding pressure vessels, the choice of a 112 °C curing temperature will help improve the vessel's overall performance. This work could provide reliable experience and insight into the curing process analysis of pressure vessel manufacturing.

Multi-objective optimization of different dome reinforcement methods for composite cases

A multi-objective optimization method was proposed for different dome reinforcement methods of a filament-wound solid rocket motor composite case based on a Radial Basis Function (RBF) model. Progressive damage of the composite case was considered in a simulation based on Hashin failure criteria, and simulation results were validated by hydraulic burst tests to precisely predict the failure mode, failure position, and burst pressure. An RBF surrogate model was established and evaluated by Relative Average Absolute Error (RAAE), Relative Maximum Absolute Error (RMAE), Root Mean Squared Error (RMSE), and R2 methods to improve the optimization efficient of dome reinforcement. In addition, the Non-dominated Sorting Genetic Algorithm (NSGA-II) was employed to establish multi-objective optimization models of variable-angle and variable-polar-radius dome reinforcements to investigate the coupling effect of the reinforcement angle, reinforcement layers, and reinforcement range on the case performance. Optimal reinforcement parameters were obtained and used to establish a progressive damage model of the composite case with dome reinforcement. In accordance with progressive damage analysis, the burst pressure and performance factor were obtained. Results illustrated that variable-angle dome reinforcement was the optimal reinforcement method compared with variable-polar-radius dome reinforcement as it could not only ensure the reinforcement angle’s continuous changing but also decrease the mass of composite materials. Compared with the unreinforced case, the reinforced case exhibited an increase in the burst pressure and performance factor of 36.1% and 23.5%, respectively.

Analysis on Cracking of a Pipeline Steel Pipe during Hydraulic Burst Test

Through macroscopic and microcosmic analysis of fracture, chemical composition analysis, fracture microscopic analysis and other methods, the causes of longitudinal and transverse fracture (only longitudinal cracking commonly through thousands of columns) in hydraulic burst test of L360M LSAW pipe were analyzed. Test results showed that the causes of transverse cracks in the steel pipe were the poor toughness of the pipe material which was related to the serious ferrite-pearlite banded structure. The serious band structure in the pipe was related to the high manganese content in the steel, which leaded to manganese segregation. We can use some measures to reduce the banded structure including controlling the element manganese content reasonably, reducing the final rolling temperature, controlling cooling rate and micro alloying.

Study on hazards from high-pressure on-board type III hydrogen tank in fire scenario: Consequences and response behaviours

Exploration of thermal performances of composite high-pressure hydrogen storage tank under fire exposure were critical issues to reduce the risk of tank rupture. Three bonfire tests of type III tanks of 210 L-35 MPa with full compressed hydrogen were exposed to a pool fire to study the response behaviours in fire scenarios. Detailed data on the tank wall temperature and inner pressure were presented in this work. Prototype bonfire tests for the type III tank indicated the failure pressure limits amounted to 41.1–41.8 MPa (average 41.4 MPa). Two consequences (rupture and hydrogen blowdown) will be caused when the inner pressure beyond this limits in fire scenario. The loading-bearing capacity of the tank reduced nearly 3 times under the prescribed fire condition when compared to its average burst pressure of 123.5 MPa conducted from the hydraulic burst test. Results also shown that fire resistance rating (FRR, time to rupture) of the three tanks were 784, 666, and 596, respectively. The FRR got shorter when the tank was exposed in the engulfing fire in advance at hydrogen blowdown case.

Stochastic analysis of failure pressure in reinforced thermoplastic pipes under axial loading and external pressure

Reinforced thermoplastic pipes (RTPs) are flexible composite pipes that are acknowledged as a good alternative to conventional submarine pipes. This study aims at investigating the impact of the uncertainties involved in the production process of the RTPs on the failure pressure under combined loading conditions. The stress distributions of RTPs were analyzed using the theory of the three-dimensional (3D) thick-walled cylinder method, combined with the homogenization method. Based on these results, to evaluate the failure mechanisms of RTPs, the 3D Hashin–Yeh failure criterion and the damage evolution model were adopted to establish a progressive failure model. For analyzing the influence of randomness of the related parameters on the first-ply failure (FPF) pressure as well as the final burst failure (FF) pressure of RTPs, a sufficient number of samples were generated using the Monte-Carlo method. Results of the stochastic analysis were validated using the hydraulic burst test data. The statistical evaluation of the stochastic analysis results was performed by using the Weibull probability density distribution function, and the results showed an increase in the probability of getting a lower failure pressure of RTPs than the average failure pressure (considering the randomness of production parameters).

INVESTIGATION ON THE EXPLOSIVE CHARACTERISTICS AND DAMAGE MODE OF CYLINDRICAL IMPROVISED EXPLOSIVE DEVICES

To study the explosive characteristics of improvised explosive devices (IEDs), the damage mode of cylindrical IEDs and the formation mechanism of natural fragments under blast loading are investigated by using the ANSYS/AUTODYN 3D finite element code with Mott’s stochastic failure model, as well as experiments of the hydraulic burst test and explosion test. The influence of the explosive charge amount and its position is also discussed. The main damage mode of the pressure container is the shearing damage, which is obviously affected by the explosive charge amount, charge position, and its power. The ability of the instantaneous function (pressurization rate) of the self-made explosive is far smaller than that of the standard explosive. Under the action of the self-made explosive, the closer to the detonation point, the smaller the size of the fragments formed.

Progressive damage analysis for multiscale modelling of composite pressure vessels based on Puck failure criterion

This study proposed a method for progressive failure analysis to investigate the failure modes of 35 MPa Type III composite pressure vessels during hydraulic burst tests. Representative volume elements (RVEs) were introduced, and the degraded elastic parameters of composite, which include fibre and matrix failure modes, were calculated by the finite element analysis (FEA) method to obtain the macroscopic stiffness degradation parameters. The Puck failure criterion was adopted, and the effective elastic parameters calculated from RVEs was introduced by the UDSLFD subroutine to simulate the multiscale progressive damage of composite layers during hydraulic burst test. Combined with acoustic emission detection, composite microscopic photos and hydraulic burst test, the burst pressure and failure modes of the vessels were analysed. The results showed that meso-macroscopic finite element models could effectively predict the progressive damage of composite pressure vessel, such as matrix crack, interlaminar failure and fiber fracture under internal pressure loading. Finally, the predicted burst pressure was about 5.4% average difference of the actual experimental results. Besides, cylinder section of the vessels was the predicted blasting position, which was close to the actual tests. Thus, the proposed method can provide theoretical reference for the design and optimisation of composite pressure vessels.

Theoretical and experimental study on sealing performance of a novel ultra-high pressure bursting disc

Bursting disc overpressure relief device services as the last safety barrier in preventing catastrophic overpressure of the pressure vessel. The design of ultra-high pressure bursting disc device is a tough engineering issue as it requires both strength and sealing reliability under ultra-high working pressure. In this paper, a novel ultra-high pressure bursting disc device is proposed as well as the sealing structure is designed. Firstly, the novel bursting disc device structure is introduced. Then, the wall thickness of the sealing ring is designed based on elastoplastic mechanical analysis. Numerical simulation is also conducted to investigate the mechanical and sealing performance theoretically. At last, the strength and the reliability of the sealing performance is proved by hydraulic burst test.

Experimental Analysis on Residual Performance of Used 70 MPa Type IV Composite Pressure Vessels

This paper was aimed to study residual performance of five 70 MPa type IV hydrogen composite pressure vessels that were employed in vehicles with same driving distance through a series of experiments. Firstly, external and internal visual inspections were performed to evaluate the damage status of hydrogen composite pressure vessels. Then the nonmetallic liner performance tests of one vessel were carried out including crystallinity test, hardness test, and tensile test. Besides, hydraulic fatigue test and hydraulic burst test for the remaining four vessels were conducted to evaluate residual strength. Experimental results show that the nonmetallic liner performance differs in different regions and temperature has an important influence on liner mechanical performance. The comparison between the results of direct burst tests and post-fatigue burst tests shows that long-term fatigue cycles lead to a reduction in burst pressure, but the effect is not significant by using hydraulic fatigue cycles in the current tests.

Experimental investigation of consequences of LPG vehicle tank failure under fire conditions

In case of a vehicle fire, an installed LPG (liquefied petroleum gas) tank with a malfunctioning safety device poses severe hazards. To investigate the consequences in case of tank failure, we conducted 16 tests with toroidal shaped LPG vehicle tanks. Three tanks were used for a Hydraulic Burst Test under standard conditions. Another three tanks were equipped with a statutory safety device and were subjected to a gasoline pool fire. The safety device prevented tank failure, as intended. To generate a statistically valid dataset on tank failure, ten tanks without safety devices were exposed to a gasoline pool fire. Five tanks were filled to a level of 20%; the remaining five were filled to a level of 100%. In order to gain information on the heating process, three temperature readings at the tank surface, and three nearby flame temperatures were recorded. At distances of l = (7; 9; 11) m to the tank, the overpressure of the shock wave induced by the tank failure and the unsteady temperatures were measured. All ten tanks failed within a time of t < 5 min in a BLEVE (boiling liquid expanding vapor explosion). Seven of these resulted directly in a catastrophic failure. The other three resulted in partial failure followed by catastrophic failure. A near field overpressure at a distance of l = 7 m of up to p = 0.27 bar was measured. All ten tests showed massive fragmentation of the tank mantle. In total, 50 fragments were found. These 50 fragments make-up 88.6% of the original tank mass. Each fragment was georeferenced and weighed. Fragment throwing distances of l > 250 m occurred. For the tanks with a fill level of 20%, the average number of fragments was twice as high as it was for the tanks that were filled completely.

Effect of Dome Curvature on Failure Mode of Type4 Composite Pressure Vessel

In this work, a series of burst tests and structural analyses have been carried out to demonstrate that, in terms of failure mode, Type 4 composite cylinder is saferwith a dome designed according to the isotensoid dome theory.In the test series, three sample vessels were used: (1) designed as guided by the isotensoid dome theory (called iso-dome cylinder); (2) with dome longer compared to uniform-stress design (called prolate cylinder); and (3) with dome wider than uniform-stress design (called oblate cylinder). Structural analyses have been performed using ABAQUS finite element code based on the periodic symmetry to circumferential direction. As a result, the maximum stresses are induced around the bodies of all three cylinders. However, the analyses, with the assumption of possible defect demonstrate that the maximum stresses are induced around the dome knuckles for the prolate and the oblate cylinders. The results of the ambient hydraulic burst tests for the three cylinders, conducted in compliance with KGS AC411-2015, show that the burst initiates from the cylinder body of the iso-dome cylinder and from the dome knuckles of the prolate and the oblate cylinders. Finally, it is recommended that, to comply with DOT CFFC 2007, the dome shape should be designed and fabricated as guided by the isotensoid dome theory.

Effect of applied current on the formation of defect in PWR nuclear fuel rods in resistance pressure welding process

The welding of zirconium alloy components is one of the most critical processes in the fabrication of nuclear fuel rods used in pressurized water reactors. For this, various welding processes, such as gas tungsten arc welding, electron beam welding, laser beam welding, and resistance pressure welding (RPW), are used around the world. In Korea, the RPW process is being used to fabricate nuclear fuel assembly fuel rods. This study investigated changes in the weldment shape owing to welding conditions such as welding current, welding force, and overlapping. The welding soundness of the weldment was evaluated by hydraulic burst test. The welding temperature of the weld zone was measured using a thermal infrared method. Discontinuous black spots in the weld line, regarded as a non-bonding defect, were confirmed as spots caused by the carbide precipitation of zirconium during welding.

Ductility of Zircaloy-4 Fuel Cladding and Guide Tubes at High Fluences

Abstract Zircaloy fuel cladding suffers progressive degradation of ductility as its neutron exposure and hydrogen uptake increase with burnup. The loss of ductility appears to be the key property governing the cladding integrity in service. We report ductility data of Zircaloy-4 fabricated in stress-relief annealed (SRA) and recrystallized (RXA) conditions, covering a range of fluence, hydrogen content, and irradiation and test temperature. The testing was performed on unirradiated and irradiated Zircaloy-4 cladding and guide tubes in SRA and RXA conditions, respectively, in the temperature range 25–350°C. These materials had been exposed to an estimated neutron fluence of ∼8 to 10 × 1025 n/m2 (E &amp;gt; 1 MeV) over four cycles of PWR operation. Due to its RXA fabrication condition, the guide tube material was also believed to represent BWR cladding. The hydrogen contents in the irradiated cladding was in the range of ∼200–600 ppm, exhibiting typical radial distribution of circumferential hydrides. By comparison, the hydrogen content in the irradiated guide tube material was in the range of ∼250–1800 ppm, exhibiting fairly uniform through-wall distribution of circumferential hydrides. Tensile tests and hydraulic burst tests were conducted on 130–150 mm long tubular specimens. In addition, smaller specimens machined in the form of 55 mm long curvilinear dog-bone and 10 mm slotted semicircular arc were tested in plane stress and plane strain configurations. Corresponding unirradiated archive materials in as-received condition and with uniform hydrogen charging up to 1200 ppm were also tested by identical methods. In all tests the fracture mode was examined by SEM fractography. The investigations revealed a decrease in ductility of Zircaloy-4, mainly caused by irradiation and only partly by increasing hydrogen content. Unlike the elongation data, the strength data remained nearly constant with increasing hydrogen content in both materials at all test temperatures. The irradiated RXA material showed better ductility than irradiated SRA material at equivalent hydrogen levels, and exhibited a clearer correlation of ductility with hydrogen content, mainly due to its uniform hydrogen distribution. The paper will provide these and other quantitative data, e.g., those correlating ductility with the local (near fracture surface) hydrogen content. The paper synthesizes the experimental results and discusses their possible application to the criteria for hydrogen concentration and ductility limits in high burnup fuel.

Characterizing steel tube for hydroforming applications

With the increased use of tubular steel products, especially for hydroforming applications, it is important to be able to predict the performance of tube from sheet tensile tests. In the present study, two aluminum killed draw quality (AKDQ) steels and one high strength low alloy (HSLA) steel were evaluated. Tensile properties and plastic strain ratios were measured on sheet material in the longitudinal and transverse directions. Axial tensile tests were performed on material extracted from production tubes. Material from quasi tubes, which are strip material bent to the same curvature as the tubes but not welded or sized, was also tested. Residual stresses in the production and quasi tube were determined by displacement methods. A hydraulic burst test was performed on the production tubes to simulate a hydroforming operation. Effective strains resulting from tubemaking are calculated for two discrete operations: bending and sizing. For the production tubes, a linear relationship was found between a load factor (strength times thickness) and effective sizing strain. The relationship between load factor and residual stress was also linear. Predictions of the maximum pressure and the strain at instability during a hydraulic burst test are shown to compare favorably with experimental values, based on flat sheet properties and tubemaking strains. The prediction of the yield strength in the tube based on flat sheet properties is shown to be fairly accurate when the effective sizing strain is small compared to the effective bending strain.

ラインパイプ用鋼材の延性き裂発生限界と実管切欠き部からの内圧破壊限界評価への適用性

For two series of API 5L X65 linepipes (Pipes A and B), the critical condition for ductile cracking of the linepipe steel and the applicability of the critical condition to an axially notched linepipe were investigated. Static 3-point bending tests for Charpy V-notch specimens were conducted in order to evaluate the critical condition of ductile cracking from the notch tip by using FE- analyses. At the position of ductile cracking from the notch tip for the Charpy type specimens, the stress triaxiality was approx. 0.6 for both linepipe steels, however the equivalent plastic strain (ep) was different on each linepipe; the ep for the ductile cracking was approx. 0.65 for Pipe A and approx. 1.47 for Pipe B. Hydraulic burst tests were then conducted for internally patched linepipes with an axial through-wall (TW) notch. The results of the FE-analyses for the hydraulic burst tests indicated the following: 1) the position of the ductile cracking at the TW notch tip was not the center of the wall-thickness (WT), but a slightly shifted position to the inner surface from the center of WT, 2) the equivalent plastic strain at the position where a ductile crack was initiated for the TW notched linepipe was almost the same as that obtained from the 3-point bending test result for the Charpy V-notch specimen. The present study revealed that the critical strain for ductile cracking from a notch tip for a Charpy type specimen was in good agreement with that for an axially notched linepipe. It was therefore clarified that the critical condition for ductile cracking for linepipes with an actual flaw could be predicted from the results of a small-scale test and FE-analysis to evaluate the relationship between the stress triaxiality and the equivalent plastic strain at the position of the ductile cracking.

Comparison of Hydraulic‐Burst and Ball‐on‐Ring Tests for Measuring Biaxial Strength

The statistics of failure of the hydraulic‐burst (HB) test were compared with those of the ball‐on‐ring (BOR) test. Polycrystalline Al2O3 tape‐cast specimens, both square and circular, in two different sizes, were tested. Both the mean strengths and the Weibull moduli from the BOR tests were approximately twice the values from the HB tests. The area (volume) under stress is much larger for the HB test than the BOR test; therefore, the HB data can be considered as a low‐probability‐of‐failure, low‐strength tail of the BOR curve that has a lower Weibull modulus than the high‐stress portion. Thus, BOR tests give a misleading picture of improvements in mechanical strength, because of changes in the fabrication and handling of substrates. However, previous observations that the incidence of edge and support failures was very high in the HB test were confirmed. Also, the apparent strength of the HB specimens was affected more strongly by size and shape than was that of the BOR specimens.

Fracture Resistance of Wire-Wrapped Cylinders

Steel cylinders wrapped with steel wire have the capability of offering not only an economical high-strength structure, but also a structure with improved fracture resistance compared with that of an unwrapped cylinder of equivalent strength. Accordingly, 2000-psi-pressure hydraulic burst tests were therefore conducted to determine the fracture resistance of 36-in-dia, 60-ksi yield-strength, 1000-psi-pressure wire-wrapped cylinders at different levels of shell notch ductility, which was varied by testing at different temperatures. The cylinders were prestressed with 1/4-in-dia cold-drawn wire, and the shells contained part-through-wall flaws. A similarly flawed unwrapped cylinder was tested for comparison. The working-stress level was 72 percent of the specified minimum yield strength in the shell and 60 percent of the minimum tensile strength in the wire. The results showed that at a pressure double that of the unwrapped shell, no crack extension occurred at a temperature at which the steel exhibited fully ductile shell behavior (+110 deg F). A 2-ft crack extension occurred at a temperature (+10 deg F) at which the steel was still in the transition temperature range from ductile-to-brittle behavior (about 20 percent shear fracture), but a brittle crack (−70 deg F) propagated to the end of the wire-wrapped shell. Except for the brittle propagating crack, wire wrapping appears to provide sufficient constraint of a shell defect or propagating crack to limit bulging and crack-opening displacement. A model based on the compatibility in displacements between the crack opening and the local wire strain is presented for calculating the arrest conditions of the propagating crack in the test at 10 deg F. The same flaw size was critical at the constant failure pressure for all test temperatures, and showed that, as predicted, ductile initiation occurs even at the −70 deg F temperature in both the wrapped and unwrapped-cylinder tests. A circumferential flaw was shown to be less critical than a longitudinal flaw of the same size.