Creep-Relaxation Modeling of HDPE and Polyvinyl Chloride Bolted Flange Joints

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Rahul Palaniappan Kanthabhabha Jeya ◽  
Zijian Zhao ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Polyvinyl Chloride ◽  
Creep Behavior ◽  
Creep Property ◽  
Dissimilar Materials ◽  
Operating Conditions ◽  
Relaxation Behavior ◽  
Polymer Materials ◽  
Creep Model ◽  
Tension And Compression ◽  
Bolted Flange

Abstract Similar to many polymer materials, high-density polyethylene (HDPE) and polyvinyl chloride (PVC) show a clear creep behavior, the rate of which is influenced by temperature, load, and time. Most bolted flange joints undergo relaxation under compression, which is caused by the creep of the material. However, the creep property of the two polymers is different under tension and compression loading. Since the sealing capacity of a flanged gasketed joint is impacted by the amount of relaxation that takes place, it is important to properly address and predict the relaxation behavior due to flange creep under compression and thereby reducing the chances of leakage failure of HDPE and PVC bolted flange joints. The main objective of this study is to analyze the compressive creep behavior of HDPE and PVC flanges under normal operating conditions. This is achieved by developing a respective creep model for the two materials, based on their short-term experimental creep test data. Both numerical and experimental simulations of the polymeric flange relaxation behavior are conducted on an NPS 3 class 150 bolted flange joint of dissimilar materials, where one of the flanges is made of HDPE or PVC material and the other one is made of steel SA105. The study also provides a clear picture on how the compression creep data of ring specimen may be utilized for predicating the flange bolt load relaxation over time at the operating temperatures.

Creep Modeling of Polyvinyl Chloride Bolted Flange Joints

2017 ◽  
Author(s):  
Zijian Zhao ◽  
Rahul Palaniappan Kanthabhabha Jeya ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Polyvinyl Chloride ◽  
Creep Behavior ◽  
Compressive Load ◽  
Dissimilar Materials ◽  
Operating Conditions ◽  
Relaxation Behavior ◽  
Creep Model ◽  
Compression Creep ◽  
Material Creep ◽  
Bolted Flange

Alike other polymer material, PolyVinyl Chloride (PVC) shows a clear creep behavior, the rate of which is influenced by temperature, load and time. Polyvinyl chloride bolted flange joints undergo relaxation under compression for which the material creep properties are different than those under tension. Since the sealing capacity of a flanged gasketed joint is impacted by the amount of relaxation that takes place, it is important to properly address and predict the relaxation behavior due to flange creep under compression and reduce the chances of leakage failure of PVC flange joints. The main objective is study the creep behavior of PVC flanges under the influence of normal operating conditions. This is achieved by developing a PVC creep model based on creep test data under various compressive load, temperature and time. A simulation of a PVC flange relaxation behavior bot numerically and experimentally is conducted on an NPS 3 class 150 bolted flange joint of dissimilar materials one made of PVC material and the other one by steel SA105. The study also provides a clear picture on how the compression creep data on Ring specimen may be utilized for predicating the flange performance under various operating temperatures with time.

Probabilistic Design and Analysis of Pressure Measuring Probes for Creep Behavior

2017 ◽  
Author(s):  
Dattatraya Parle
Keyword(s):  
Creep Behavior ◽  
Probabilistic Approach ◽  
Operating Conditions ◽  
Model Complexity ◽  
Creep Model ◽  
Operating Parameters ◽  
Secondary Creep ◽  
Operating Pressure ◽  
Probabilistic Design ◽  
Input Parameters

Pressure probes are typically used to measure the pressure of a fluid stream. These probes are designed to serve for 25 years life under operating pressure and temperature conditions. Therefore, such pressure probes are also designed for safe creep behavior. Typically creep is time dependent phenomenon and it can be classified as Primary, Secondary and Tertiary creep. In the literature, the creep phenomenon is studied analytically and numerically. Literature review reveals that creep analysis requires special material models and its selection depends on operating conditions. This work presents FEA based probabilistic design and analysis of pressure measuring probes using ANSYS which has several creep models depending on type of creep phenomenon. Probes in this study are subjected to primary and secondary creep. Therefore, this work proposes combined time hardening creep model. Combined time hardening model has 7 coefficients. This further increases the complexity of the model. Apart from the model complexity, there are various other design and operating parameters which further complicates the creep behavior. Some of the important design and operating parameters are length, diameter and tip dimensions along with pressure and temperature. Thus there are around 16 parameters which controls the creep behavior of pressure measuring probe. Traditional design process of probe is based on deterministic analysis which involves the use of safety factors as a way of accounting for uncertainty in design input parameters. This can often results in overly conservative designs. Moreover, to understand optimal creep behavior of probes under several uncertainties in input parameters becomes a challenging. Therefore, this work presents probabilistic approach as opposed to a deterministic approach to understand the combined effect of several uncertain parameters on creep behavior of probes. This work not only determines probability of probe failure more accurately but also determines the sensitivity of each parameter during creep phenomenon using FEA.

Effect of Creep of Non-Asbestos Sheet Gaskets at Elevated Temperature on Relaxation Behavior of Bolted Flange Joints

2011 ◽  
Author(s):  
Atsushi Yamaguchi ◽  
Takashi Honda ◽  
Masahiro Hagihara ◽  
Hirokazu Tsuji
Keyword(s):  
Elevated Temperature ◽  
Creep Strain ◽  
Creep Behavior ◽  
Elevated Temperatures ◽  
Relaxation Behavior ◽  
Test Conditions ◽  
Internal Fluid ◽  
Fiber Sheet ◽  
Ptfe Sheet ◽  
Bolted Flange

Gaskets in bolted flange joints experience creep when used for long periods of time. Since gaskets are often used at elevated temperatures, the clarification of their high-temperature creep behavior is essential. Relaxation of bolted flange joints is caused by creep in the gaskets, and may result in leakage of internal fluids. Therefore, the ability to predict relaxation in bolted flange joints due to the effects of creep in gaskets would allow the lifetime of the gaskets to be estimated and thus prevent leakage of internal fluid. In the present study, the creep behavior of non-asbestos sheet gaskets and the relaxation behavior of these gaskets in bolted flange joints at room/elevated temperature were investigated using four-inch flanges. The test conditions were 180 °C for 360 hours (approximately 2 weeks). The test samples were four types of non-asbestos sheet gaskets, two types of compressed fiber sheet gaskets and two types of PTFE sheet gaskets. The differences in creep behavior between the two types of compressed fiber sheet gaskets and between the two types of PTFE sheet gaskets were clarified. The creep strain at the end of the test was always larger than that just after reaching the test temperature for all gasket materials. On the other hand, the creep strain in the PTFE sheet gaskets just after reaching the elevated temperature was approximately equivalent to the total creep strain after the test has been completed. Thus, the creep behavior of each test gaskets was clarified under aging. In addition, the time for replacement of gaskets was estimated using the relaxation behavior in bolted flange joints by defining the time to reach the minimum design seating stress of the test gasket.

Study on triaxial creep behavior and the damage constitutive model of red sandstone containing a single ice-filled flaw

2020 ◽  
pp. 105678952096143
Author(s):  
Yao Bai ◽  
Renliang Shan ◽  
Tianyu Han ◽  
Haoyu Dou ◽  
Zhe Liu
Keyword(s):  
Constitutive Model ◽  
Creep Behavior ◽  
Creep Property ◽  
Creep Model ◽  
Creep Process ◽  
Red Sandstone ◽  
Creep Curves ◽  
Triaxial Creep ◽  
Dip Angle ◽  
Frozen Red Sandstone

The freezing method is widely used in the construction of vertical shafts in water-rich strata. The formed frozen rock wall is often involved in the creep process, and in particular, the creep behavior of frozen fissured rock mass poses a great threat to construction safety. To better understand the creep instability law of ice-filled, fractured red sandstone under freezing and triaxial stress conditions, a series of triaxial creep tests on frozen red sandstone specimens containing a single, pre-existing flaw at −10°C and under a confining pressure of 4 MPa were carried out with a self-developed DRTS-500 subzero rock triaxial testing system. The multistage loading creep curves were obtained, and the evolution laws of deformation and damage for the frozen specimens in the primary (instantaneous), secondary (steady-state) and tertiary (accelerating) phases were analyzed. The nonlinear visco-elastoplastic constitutive model of red sandstone with a single ice-filled flaw was established according to the fractional calculus theory and the Kachanov damage theory. The results show that the initial creep property, unstable creep property and creep failure mode of frozen single-flaw red sandstone are significantly affected by the flaw dip angle. The proposed creep damage model can accurately describe the complete creep curves of frozen red sandstone with a single ice-filled flaw, especially in the unstable creep stage. The influences of the stress level and flaw dip angle on the creep parameters were analyzed, and sensitivity analyses of the characteristic creep parameters were carried out to verify the reliability and rationality of our creep model. This research can be applied to the assessment of collapse, cracking and other long-term failures and hence can be used as a theoretical basis of design in the freezing engineering of coal mine shafts.

scholarly journals A Phenomenological Primary–Secondary–Tertiary Creep Model for Polymer-Bonded Composite Materials

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2353
Author(s):  
Xiaochang Duan ◽  
Hongwei Yuan ◽  
Wei Tang ◽  
Jingjing He ◽  
Xuefei Guan
Keyword(s):  
Composite Materials ◽  
Creep Behavior ◽  
Reference Model ◽  
Creep Model ◽  
Creep Process ◽  
Validation Dataset ◽  
Testing Conditions ◽  
Proposed Model ◽  
Testing Data ◽  
Bonded Composite

This study develops a unified phenomenological creep model for polymer-bonded composite materials, allowing for predicting the creep behavior in the three creep stages, namely the primary, the secondary, and the tertiary stages under sustained compressive stresses. Creep testing is performed using material specimens under several conditions with a temperature range of 20 °C–50 °C and a compressive stress range of 15 MPa–25 MPa. The testing data reveal that the strain rate–time response exhibits the transient, steady, and unstable stages under each of the testing conditions. A rational function-based creep rate equation is proposed to describe the full creep behavior under each of the testing conditions. By further correlating the resulting model parameters with temperature and stress and developing a Larson–Miller parameter-based rupture time prediction model, a unified phenomenological model is established. An independent validation dataset and third-party testing data are used to verify the effectiveness and accuracy of the proposed model. The performance of the proposed model is compared with that of an existing reference model. The verification and comparison results show that the model can describe all the three stages of the creep process, and the proposed model outperforms the reference model by yielding 28.5% smaller root mean squared errors on average.

An Experimental Study on the Effect of Prior Plastic Straining on Creep Behavior of 304 Stainless Steel

1993 ◽  
Vol 115 (2) ◽  
pp. 200-203 ◽  
Author(s):  
Z. Xia ◽  
F. Ellyin
Keyword(s):  
Stainless Steel ◽  
Plastic Strain ◽  
Strain Rate ◽  
Creep Behavior ◽  
Test Procedure ◽  
Constant Strain Rate ◽  
304 Stainless Steel ◽  
Creep Model ◽  
Plastic Strain Rate ◽  
Creep Tests

Constant strain-rate plastic straining followed by creep tests were conducted to investigate the effect of prior plastic straining on the subsequent creep behavior of 304 stainless steel at room temperature. The effects of plastic strain and plastic strain-rate were delineated by a specially designed test procedure, and it is found that both factors have a strong influence on the subsequent creep deformation. A creep model combining the two factors is then developed. The predictions of the model are in good agreement with the test results.

scholarly journals Influence of Normal Stress on Creep in Tension and Compression of Polyethylene and Rigid Polyvinyl Chloride Copolymer

1962 ◽  
Vol 84 (2) ◽  
pp. 237-246 ◽  
Author(s):  
D. G. O’Connor ◽  
W. N. Findley
Keyword(s):  
Normal Stress ◽  
Polyvinyl Chloride ◽  
Material Structure ◽  
Reasonable Accuracy ◽  
Creep Tests ◽  
Compression Creep ◽  
Cent Relative Humidity ◽  
Tension And Compression ◽  
New Apparatus ◽  
Shear Planes

New apparatus suitable for compression creep tests of slender specimens is described. The apparatus is designed to prevent buckling and to introduce a minimum of friction. Results are reported for tension and compression creep of polyethylene and annealed, unplasticized polyvinyl chloride copolymer at 75 deg F and 50 per cent relative humidity. The stress σ, strain ε, time t data from these tests were found to be describable with reasonable accuracy by the equation ε=ε0′sinhσ/σε+m′tnsinhσ/σm where ε0′, m′, n, σε, and σm are material constants. The results for polyethylene show that the creep in tension and compression were virtually the same. However, the creep in tension was similar but larger than in compression for polyvinyl chloride. These observations are interpreted in terms of the material structure and the influence of the normal stress on active shear planes.

Impact of Operating Conditions and Design Parameters on Gas Turbine Hot Section Creep Life

2010 ◽  
Author(s):  
S. Eshati ◽  
M. F. Abdul Ghafir ◽  
P. Laskaridis ◽  
Y. G. Li
Keyword(s):  
Gas Turbines ◽  
Performance Model ◽  
Operating Conditions ◽  
Creep Model ◽  
Design Parameters ◽  
Gas Temperature ◽  
Creep Life ◽  
Cooling Effectiveness ◽  
Radial Temperature ◽  
The Impact

This paper investigates the relationship between design parameters and creep life consumption of stationary gas turbines using a physics based life model. A representative thermodynamic performance model is used to simulate engine performance. The output from the performance model is used as an input to the physics based model. The model consists of blade sizing model which sizes the HPT blade using the constant nozzle method, mechanical stress model which performs the stress analysis, thermal model which performs thermal analysis by considering the radial distribution of gas temperature, and creep model which using the Larson-miller parameter to calculate the lowest blade creep life. The effect of different parameters including radial temperature distortion factor (RTDF), material properties, cooling effectiveness and turbine entry temperatures (TET) is investigated. The results show that different design parameter combined with a change in operating conditions can significantly affect the creep life of the HPT blade and the location along the span of the blade where the failure could occur. Using lower RTDF the lowest creep life is located at the lower section of the span, whereas at higher RTDF the lowest creep life is located at the upper side of the span. It also shows that at different cooling effectiveness and TET for both materials the lowest blade creep life is located between the mid and the tip of the span. The physics based model was found to be simple and useful tool to investigate the impact of the above parameters on creep life.

Creep Analysis for an Unbonded Flexible Pipe Barrier

2006 ◽  
Author(s):  
Lun Qiu ◽  
John Zhang
Keyword(s):  
Finite Element ◽  
Creep Behavior ◽  
Barrier Layer ◽  
Polyvinylidene Fluoride ◽  
Element Model ◽  
Polymer Materials ◽  
Flexible Pipe ◽  
Internal Fluid ◽  
Creep Analysis ◽  
Parameter Matching

The fluid barrier in an unbonded flexible pipe seals the pressure from the internal fluid. Since the barrier is usually made of polymer materials, it is unable to hold the pressure by itself. A metal reinforced hoop layer is usually needed outside the barrier layer in order to resist the pressure. The hoop layer is usually a steel bar with a cross-section of an irregular shape. It is helically wrapped at the outside of the barrier layer. When the pipe is pressurized, the barrier will be supported by the hoop reinforcement layer from outside. However, at the gap between the steel wraps where the barrier layer bridges, material of the barrier will be forced to extrude into the gap. The amount of the extrusion is a function of many parameters such as temperature, material property, and internal pressure and so on. In addition, it is time dependent. The creep effect needs be considered. It is critical to have a proper barrier design for a flexible pipe structure. This article presents a practical finite element method for evaluation of the barrier/gap design. The creep behavior of the polymers is multi-parameter related. Therefore, a series of material tests has been conducted under various stresses and temperatures for nylon, polyethylene and Polyvinylidene Fluoride. In this work a method is given to determine the creep behavior parameters through parameter matching based on the tests. The creep deformation of barrier was analyzed with a finite element model using these parameters.

scholarly journals Hardware-in-the-loop simulation of wave energy converters based on dielectric elastomer generators

Meccanica ◽  
2021 ◽  
Vol 56 (5) ◽  
pp. 1223-1237
Author(s):  
Giacomo Moretti ◽  
Andrea Scialò ◽  
Giovanni Malara ◽  
Giovanni Gerardo Muscolo ◽  
Felice Arena ◽  
...  
Keyword(s):  
Wave Energy ◽  
Large Scale ◽  
Low Cost ◽  
Test Site ◽  
Dielectric Elastomer ◽  
Operating Conditions ◽  
Polymer Materials ◽  
Hardware In The Loop ◽  
Wave Energy Converters ◽  
Energy Converters

AbstractDielectric elastomer generators (DEGs) are soft electrostatic generators based on low-cost electroactive polymer materials. These devices have attracted the attention of the marine energy community as a promising solution to implement economically viable wave energy converters (WECs). This paper introduces a hardware-in-the-loop (HIL) simulation framework for a class of WECs that combines the concept of the oscillating water columns (OWCs) with the DEGs. The proposed HIL system replicates in a laboratory environment the realistic operating conditions of an OWC/DEG plant, while drastically reducing the experimental burden compared to wave tank or sea tests. The HIL simulator is driven by a closed-loop real-time hydrodynamic model that is based on a novel coupling criterion which allows rendering a realistic dynamic response for a diversity of scenarios, including large scale DEG plants, whose dimensions and topologies are largely different from those available in the HIL setup. A case study is also introduced, which simulates the application of DEGs on an OWC plant installed in a mild real sea laboratory test-site. Comparisons with available real sea-test data demonstrated the ability of the HIL setup to effectively replicate a realistic operating scenario. The insights gathered on the promising performance of the analysed OWC/DEG systems pave the way to pursue further sea trials in the future.

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