Internal Pressure Loading Research Articles

Simulation of internal water pressure loads for HPP penstock pipes under seismic impacts

Simulation of internal water pressure loads for HPP penstock pipes under seismic impacts

Comparison of Performance of Predicting the Wear Amount of Tire Tread Depending on Sensing Information.

Excessive tire wear can affect vehicle driving safety. While there are various methods for predicting the tire wear amount in real-time, it is unclear which method is the most effective in terms of the difficulty of sensing and prediction accuracy. The current study aims to develop prediction algorithms of tire wear and compare their performances. A finite element tire model was developed and validated against experimental data. Parametric tire rolling simulations were conducted using various driving and tire wear conditions to obtain tire internal accelerations. Machine-learning-based algorithms for tire wear prediction utilizing various sensing options were developed, and their performances were compared. A wheel translational and rotational speed-based (V and ω) method resulted in an average prediction error of 1.2 mm. Utilizing the internal pressure and vertical load of the tire with the V and ω improved the prediction accuracy to 0.34 mm. Acceleration-based methods resulted in an average prediction error of 0.6 mm. An algorithm using both the vehicle and tire information showed the best performance with a prediction error of 0.21 mm. When accounting for sensing cost, the V and ω-based method seems to be promising option. This finding needs to be experimentally verified.

Comparison of fibre reorientation of short-and long-fibre reinforced polypropylene by injection molding with a rotating mold core

Abstract With a rotating mold core during the injection molding of fibre-reinforced plastics, the rotational shear caused by the rotation is superimposed on the injection-induced shear. This allows the fibre orientation in this area to be intentionally manipulated so that, for example, in the case of internal pressure loading, the fibres can be oriented in the tangential main loading direction. This paper deals with the impact of a rotating mold core on the fibre orientation and burst strength of short-and long-fibre-reinforced polypropylene. It is shown that the fibre orientation and strength can be significantly influenced for both short and long fibres, whereby increases in bursting strength of mostly over 80%, in some cases over 200%, could be achieved. The ultimate strength depends, among other things, on the wall thickness used and the fibre content. Major differences between the short-and long-fibre-reinforced polypropylene are less evident in the strength and more in the fibre orientation.

Effects of the legacy pipe ends on the behaviour of pipe-in-pipe repair systems under internal pressure

Pipe-in-pipe (PIP) has become an acceptable system for the rehabilitation and repair of natural gas distribution networks. Damaged host pipes usually contain defects such as circumferential cracks which can affect the performance of the PIP systems. Under internal pressure, the PIP system will be in contact with the damaged pipes and may have an adverse effect on its structural performance. This paper investigates the effect of the sharp edge of the legacy pipe opening on the PIP systems under the internal pressure. The effect of several design parameters including the bonding condition of the PIP to the host pipe, the material properties of the PIP system, and the level of sharpness of the host pipe ends are evaluated. The numerical results show that without bonding of the PIP to the host pipe, the stress concentration is minimised as the PIP can deform around the edge of the host pipe. The use of high strain PIP material systems and rounding the edge of the host pipe also contribute to reducing stress concentration. The irregular opening of the legacy pipe represents the practical situation in which both unbonded and rounded factors are found effective in terms of stress concentration relief. The outcomes of this work provide useful information on minimising stress concentrations on PIP systems, which can be effectively utilised in repairing damaged pipes with a circumferential crack under the internal pressure loading.

A safety assessment approach to pressure vessels based on machine learning

The safety assessment of a pressure vessel with a surface crack is an important part of the safety assessment of engineering equipment. However, the existing methods are mostly based on the assumption of plane specimens and the K criterion applicable to brittle fracture, which may lead to unacceptable errors when applied to a fracture problem in an elastoplastic pressure vessel. In this article, based on the finite element method (FEM) and artificial neural network (ANN), the elastic-plastic three-dimensional J-integral of a crack tip in a pressure vessel with an axial semi-elliptic crack on the surface under the loading of internal pressure is studied. First, the influence of the vessel geometry, the crack size, and internal pressure on the three-dimensional J-integral is analyzed. Second, the machine learning dataset is constructed based on the results of 1,200 cases of FEM calculation; then ANNs are used to discover the potential relationship between multiple parameters and the three-dimensional J-integral. The results show that the neural network constructed in this article can well predict the elastoplastic three-dimensional J-integral of a pressure vessel surface crack.

Martian Buildings: Design loading

Multiplanetary life has been studied by scientists as a way to supply energy or sustain human life in the future. Mars is likely to be man’s first destination, colonization using onsite structural construction would be one of the main options. The first step to designing a reliable building is to know the applied structural loads and to have an accurate design load combination. Due to lack of complete knowledge, short span of recorded data, Martian environment, and hazardous environment that Martian structures face, constructed Martian structures should behave appropriately under the highest likely live, dead and environmental loads either simultaneously or as a worst-case scenario. The present study evaluated and calculated probable Martian structural loads, including live, internal pressure, snow, gravity (dead), dust accumulation, thermal stress, wind, marsquake, asteroid, and meteoroid impact loads and their effects. Information was gathered from previous studies and valid data from Martian landers, rovers and orbiters. Wind loads were calculated based on the over 6.5 years of data recorded by Vikings 1 and 2, temperature and winds for InSight (TWINS) sensor. A wind shear exponent and wind profile have been proposed for a Martian flat terrain construction site. Marsquake lateral loads, frequency content and seismicity were assessed using data from the seismic experiment for interior structure (SEIS) and the Viking 2 seismometer. Considering the high influx of micrometeoroids, their penetration distance, impact loads and their effects on structures were calculated. The annual probability of an asteroid impact on a settlement was assessed for a 30-year mission. A load map for Martian residential buildings that considers the worst-case scenario in which a Martian structure should be designed based on them has been proposed.

Design Methods for Variable-Stiffness Super-Ellipsoidal Pressure Vessels Under Thermomechanical Loading

Pressure vessels are widely used in a broad range of applications in many industries, including possible use for hydrogen storage. Additionally, pressure vessels comprise non-circular-cross-section fuselages such as in blended-wing–body aircraft. Failure performance, weight, and packing efficiency are important factors that should be considered when designing pressure vessels. Often, lightweight pressure vessels maximize their volume for a given available space volume and withstand substantial internal pressure. Bend-free super ellipsoids of revolution, enabled by stiffness tailoring via variable-angle tow placement of composite plies, present an appealing solution that makes them possible candidates for future composite pressure vessels. To date, the bend-free design methodology for super ellipsoids of revolution has only been developed under uniform internal pressure loading. However, in reality, pressure vessels can also be subjected to thermal loads during service. Therefore, this study develops an initial bend-free design methodology for super ellipsoids of revolution that are subjected to both uniform internal pressure and thermal loads.

Numerical Study of the Performance of Existing Prestressed Cylindrical Concrete Pipes Strengthened with Reinforced Concrete or Carbon-Reinforced Fiber Polymer Jackets—Part B

A popular water pipe system, used in many countries, is one formed by prestressed cylindrical concrete pipes (PCCP). This study used the results of an experimental investigation on ten (10) PCCP samples taken from an existing water pipeline. The objective was to investigate their bearing capacity under three-edge bending or internal hydraulic pressure loads to check the capability of specific retrofitting/strengthening schemes to upgrade this bearing capacity and thus enhance the operational period (Part A). In this part B study, the measured response of the PCCP pipes was made to validate a numerical approach aimed at numerically simulating the behavior of the original and retrofitted PCCP pipes under hydraulic internal pressure. From the obtained numerical results, it was seen that the assumed nonlinear mechanisms for the concrete volume and steel membrane were verified by comparing numerical predictions with measurements in terms of strain response of the steel membrane, damage patterns of the concrete volume, and the overall internal pressure versus radial expansion response. The numerical predictions of the bearing capacity contribution of the fully active prestress as well as the three specific jacketing schemes, including carbon fiber reinforced polymer (CFRP) or reinforced concrete (RC) jackets, were also verified from comparisons with the corresponding measured response.

Numerical simulation of hydraulic fracturing with consideration of the pore pressure distribution based on the unified pipe-interface element model

Understanding hydraulic fracture propagation behaviours is vital for optimizing fracturing design in oil and gas production. It has been observed that the stress and pore pressure distribution are much more complex during fracturing treatment as a result of long-term fluid injection and production in the reservoir. When rock is subjected to internal hydraulic pressure and external mechanical loading, the closing, opening, or other interactions of pre-existing weaknesses or induced new fractures will be altered. In this paper, a number of hydraulic simulation scenarios are performed to investigate the effect of pore pressure distribution on fracture initiation and propagation using the unified pipe-interface element method (UP-IEM). The proposed method for predicting the hydraulic fracture path in the permeable porous medium with non-uniform pore pressure field is validated with experimental results. Considering the arrangement of well patterns and natural fractures in the rock, the problems of hydraulic fracture propagation behaviours with wellbore interaction and pore pressure induced natural fracture activation are simulated. The influence of pore pressure saturation and the injection sequence of wellbores on hydraulic fracturing are researched. A sensitivity analysis is carried out to investigate the parameter effects on pre-existing fracture tortuosity, opening width and breakdown pressure under pore pressure. These numerical examples provide guidance to engineers to estimate the probability of danger or possibilities to improve the injection and production of wells.

Experimental Investigation of the Structural Performance of Existing and RC or CFRP Jacket-Strengthened Prestressed Cylindrical Concrete Pipes (PCCP)—Part A

A popular water pipe system used in many countries is one formed by prestressed cylindrical concrete pipes (PCCPs) formed by identical precast moduli joined together in situ. This technology was and still is quite popular in many water supply systems internationally. This technology was mainly selected at the time due to its cost-based comparative advantage. However, over the years, numerous incidents of structural failures have been reported for this type of pipeline, causing, in some cases, serious disruption of the water supply. This study summarizes the results of an experimental investigation on ten (10) PCCP specimens taken from an existing water pipeline with the objective of investigating their bearing capacity under either three-edge bending or internal hydraulic pressure loads. Moreover, there is a need to check the capability of specific retrofitting/strengthening schemes to upgrade this bearing capacity and thus enhance the operational period. Provided that the prestressing wires are fully active according to design specifications, the original specimen performed satisfactorily for the set internal hydraulic pressure limit of 8.5 bar. Specimens retrofitted with either internal or external CFRP or RC jacketing performed satisfactorily for internal hydraulic pressure levels well above this 8.5 bar limit. A critical factor is, as expected, the loss of prestress.

A Semi Empirical Regression Model for Critical Dent Depth of Externally Corroded X65 Gas Pipeline.

External corrosion dent is a common type of compound dent. On the one hand, this type of compound dent reduces the bearing area and bearing capacity of the pipeline. On the other hand, it leads to an increase in the stress–strain concentration in the dent and reduces the anti-fatigue load capacity of the pipeline, which is more harmful to the service safety of the pipeline than the simple dent. In this study, the reliability of the modeling method was verified by the numerical inversion of the full-size dented pipe test. A three-dimensional finite element model for a pipe with a small corrosion dent was established by analyzing the internal detection data on corrosion defects of pipes with a diameter of 813 mm. The failure criterion of the corrosion dent pipe and the calculation method of the critical dent depth were determined. The influence of corrosion depth, length, width, internal pressure load, curvature radius of indenter, and diameter–thickness pipeline ratio on critical dent depth was investigated. Finally, a critical dent-depth prediction formula was developed based on the numerical results. This study provides a reference and significant guidance for the applicability evaluation of corroded sunken pipelines.

Shakedown limit of elbow pipe under coupled cyclic thermal-mechanical loading based on the LMM

In this paper, the linear matching method (LMM) is used to study the shakedown limit of elbow pipes under coupled cyclic mechanical-thermal load. Firstly, the thermal stress analyses of elbow pipes under constant internal pressure and cyclic temperature load are investigated. Further, the shakedown limits of the elbow pipes are calculated using the LMM. For the verification purposes, step-by-step inelastic analyses are performed, showing different structure responses under different loading conditions. All the obtained results indicate that the LMM is able to simulate large range of coupled cyclic mechanical-thermal loading conditions with high computational efficiency, and provide shakedown limit with high accuracy. In addition, the effects of bend angles, mean radius to wall thickness ratio (r/t) and five load conditions on the shakedown behavior are also presented.

Experimental and Theoretical Study of Internal Pressure Loads on Boundary Walls under Gusty Wind Conditions

This work contains an acceptable solution to the most practical interest to reduce the internal pressure load variations acting on closed envelops (i.e., inner building walls, fairing of rocket, and missile payloads) under gusty wind conditions. To simulate the gusty wind conditions (i.e., tangential unsteady flow condition), an experimental setup of a wind tunnel with a sinusoidal gust generating mechanism has been established in IDR of the Universidad Politécnica de Madrid (IDR/UPM), Spain. The wind tunnel has been equipped with an air reservoir with vent holes. The pressure jumps shown across the vent holes are studied as a function of sinusoidal gust frequency, volume of the air reservoir, and vent hole size. A theoretical model (based on the mass conservation equation and polytropic law gas evolution) has been proposed to predict the pressure jumps and variations under gusty wind conditions. At the end of the work, theoretical and experimental results have been studied and compared. The relationship between pressure loss coefficient ξ and flow coefficient α under unsteady flow conditions has been evaluated.

Mechanism Study of Bi-Material COPV Structure Based on Composite Structure Design Theory

Composite over-wrapped pressure vessels (COPVs) are widely used in aerospace, aviation, army, Navy, nuclear industry and other military and civil fields because of their light weight, high strength, high reliability and safety, leak before burst (LBB) failure mode safety and many other characteristics. Because the aerospace field has very strict requirements on the weight of platform structure products including COPV, it is necessary to improve the mass efficient of COPV and achieve the characteristics of light weight and high strength. In this paper, through the optimization of composite material grid theory algorithm, the relationship between bidirectional stress and internal pressure of cylinder and dome of isotropic material is deduced. On this basis, the grid theory equations of bidirectional stress and internal pressure load of COPV cylinder and dome are deduced, and the wall thickness equations of ordinary rotating curve head, equal tension head and hemispherical head are proposed. According to the grid theory model of membrane stress of COPV cylinder, the author completed the grid theory algorithm derivation of elastic and plastic lined COPV. This paper is the exploration of composite dome structure analysis, which lays a foundation for the subsequent solution of composite dome grid theory.

Study on Thermal Shock Failure Characteristics of RPV During IVR System Start-Up for Typical Advanced PWR

When the large pressurized water reactor in-vessel retention (IVR) system is put into operation, the outer wall of the reactor pressure vessel (RPV) will experience severe temperature fluctuations and be subjected to high internal pressure loads at the same time. In order to ensure the structural integrity of the RPV under such conditions, first, through the severe accident system program, the case that has the greatest impact on the pressure-bearing thermal shock of the outer wall of the reactor pressure vessel was selected under the station blackout (SBO) accident. Then, based on this case, the fracture mechanics finite element method was used to calculate and evaluate the pressure thermal shock (PTS) of the RPV, and the final crack size at the end of the life of the core barrel and the lower head was obtained by fatigue crack expansion calculation. The maximum ratio of the stress intensity factor correction value and corresponding limit value under the PTS transient load is about 0.874, which meets the requirements of RCC-M specification. The results of the study indicate that the RPV will not experience fracture failure when the IVR system is put into service during the station blackout accident for the HPR1000 nuclear power plant.

Ductile fracture modeling using the modified Mohr–Coulomb model coupled with a softening law for an ASTM A285 steel

Ductile fracture is one relevant failure mechanism in pressurized metallic components such as pressure vessels and pipelines. This work describes a framework to model ductile fracture based on phenomenological critical local strain criterion coupled with softening law rule to predict the onset of ductile fracture and tearing response in typical geometries extracted from an ASTM A285 steel. Overall, the numerical predicted load vs. displacement curves are in good agreement with measured data for all samples. Detailed numerical analyses are also performed to investigate the strain capacity of defected pipes under internal pressure and axial loading.

Crack propagation mechanism of rock-like specimens containing non-parallel flaws subjected to internal hydraulic pressure and shear loading

The rock masses with existing discontinuous joints are more prone to failure under the combination of fissure water and shear loading. Therefore, combining laboratory experiments with discrete element simulation, the mechanism of crack initiation, propagation, and coalescence in rock-like specimens (a type of high brittle cement mortar material) with non-parallel flaws under shear loading and internal water pressure is investigated. The results reveal that for specimens with various flaw dip angles the propagation direction of all newly generated cracks is basically parallel to the shearing loading. When the flaw inclination angle reaches −30°, the cracks initiated near pre-existing flaw tips are the result of the combined effects of fluid pressure and compressive stress fields. Compared with the hydraulic fracturing curve, both plateau period and water pressure fluctuations appear in the selected domain near the crack propagation paths, which can demonstrate that the evolution of water pressure is extremely complex due to the constant crack healing and opening. With the increase of water pressure, the global stress field becomes more uniform, and the stress concentration near pre-existing flaw tips is weakened, indicating that water pressure can lead to local stress redistribution. Ultimately, the work is expected to provide guidance to the safe construction of tunnel excavation under complex geological conditions.

Implementation of multiscale mechanisms in finite element analysis of active composite structures

Interrogation of composite structures for inherent damage is investigated implementing three-tier analysis scheme. The analysis starts at the structure level where a general-purpose Finite Element code ABAQUS is employed to obtain the stress field in the second level of analysis that is the composite laminate. A special material routine is prepared to propagate the local fields to the individual plies and hence to the third level of analysis which is the microstructure modelling of the composite. Through the third level of analysis, interface damage between fiber and matrix is checked implementing a certain failure criteria. The interaction between the different length scales; that are, structure, macro, and micro scales, is implemented using the non-mechanical strains caused by damage. Embedment of electrically active fibers in the laminate serves as a tool to interrogate the structure for inherent damage through the electric displacement generated due to the electro-mechanical coupling. To verify the developed multi-scale model, a comparison with the experimental results of a tube problem under combined internal pressure and axial load is presented. The results show good agreement in both the undamaged and damaged state. As an application, a plate with a hole under biaxial load is solved. The output includes not only the structure global behavior during damage but also detailed information about the location of damage within the structure, the plies that exhibit damage, type of damage and the fiber/matrix debonded length. Comparison between the electric displacement of the active fibers in the undamaged and damaged states is presented as well.

Investigation of Circular, Elliptical and Obround Shaped Vessels by Finite Element Method(FEM) Analysis under Internal Pressure Loading

The forms of pressure vessels applicable withinside the aerospace enterprise are starting from essential load-carrying imperative tank systems to small auxiliary tanks and pressurized cabins. Elliptical and obround stress vessels are used in which there may be a space-constrained. In the present work nonlinear(geometric and material within tensile strength) finite element evaluation is performed for the determination of its stress state in open-ended pressure vessels of various shapes(round, elliptical, and obround). A parametric examine has been completed and outcomes offered for different inside areas of vessel shapes and thickness of the cross-sections. As the inside area of the shape of pressure vessel increases, the effective stress increases for a particular thickness. The deformed shape elliptical/obround under internal pressure might no longer be uniformly enlarged because of non-uniform bending. Deformation and effective stress in the elliptical/obround shapes are found higher than circular shape for a particular thickness and inside area of vessel.

Theoretical and Numerical Study on the Three-Edge Bearing Capacity of Prestressed Concrete Cylinder Pipe

Prestressed Concrete Cylinder Pipe (PCCP) is a composite pipe structure commonly subjected to earth pressure, internal pressure, and ground loads. To confirm the bearing capacity of PCCP by using the in-direct design method, one of the most important experiments is the Three-Edge Bearing (TEB) test. A rational theoretical analysis method and Finite Element Analysis (FEA) are developed in this study because the TEB test is costly and difficult to conduct. The proposed theoretical analysis method and Finite Element (FE) method can be used to calculate the internal force, the displacement, the cracking load, and the bearing capacity of PCCP under the TEB load. In addition, a parametric study is carried out by using the validated theoretical analysis and FEA method. It is found that the concrete strength, the prestressing level, and the radius-to-thickness ratio of the steel cylinder affects the bearing capacity of PCCP under the TEB load. Furthermore, the proposed theoretical analysis method can be used to calculate the bearing capacity of other kinds of rigid pipes under the three-edge bearing load.