Viscoelastic Finite Element Modeling of Bimodal High Density Polyethylene (HDPE) Piping Materials for Nuclear Safety-Related Applications

2010 ◽  
Author(s):  
Do-Jun Shim ◽  
Prabhat Krishnaswamy ◽  
Yunior Hioe ◽  
Sureshkumar Kalyanam
Keyword(s):  
Finite Element ◽  
Service Life ◽  
High Density Polyethylene ◽  
Viscoelastic Behavior ◽  
Time Dependent ◽  
Tensile Creep ◽  
Uniaxial Tensile ◽  
Fe Model ◽  
Creep Tests ◽  
Uniaxial Tensile Creep

The U.S. Nuclear Regulatory Commission (USNRC) has recently approved Relief Requests for the use of high density polyethylene (HDPE) piping in safety-related applications. The ASME Boiler and Pressure Vessel Code, meanwhile, has developed Code Case N-755 that defines the design and service life requirements for PE piping in nuclear plants though it has not as yet been approved by the USNRC. One of the issues of concern is premature failure of PE piping due to slow crack growth (SCG) that can initiate due to a combination of sustained loads, elevated temperatures, and a pre-existing defect. Understanding and predicting the SCG behavior is an essential step in developing a methodology for predicting the service life of PE piping. The first step in studying the failure process in a polymer under a constant sustained load is the selection of a suitable constitutive model to represent the time-dependent behavior of the material. In this paper, uniaxial tensile creep tests were performed for a bimodal HDPE (PE4710) piping material. This creep data was used to determine the viscoelastic material constants for this bimodal HDPE using a power-law creep model. These material constants were used in finite element (FE) analyses to study the viscoelastic behavior of the bimodal HDPE. As a first step, the FE model was verified by comparing the results from numerical simulations and experiments for a set of uniaxial tensile creep tests. The FE model was then applied to study the viscoelastic behavior of a SCG specimen. The time dependent stress and strain fields were investigated.

scholarly journals Thermo-Viscoelastic Response of 3D Braided Composites Based on a Novel FsMsFE Method

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 271
Author(s):  
Jun-Jun Zhai ◽  
Xiang-Xia Kong ◽  
Lu-Chen Wang
Keyword(s):  
Finite Element ◽  
Cell Model ◽  
Structural Parameters ◽  
Thermal Relaxation ◽  
Viscoelastic Behavior ◽  
Unit Cell ◽  
Time Dependent ◽  
3D Braided Composites ◽  
Equivalent Time ◽  
Representative Unit Cell

A homogenization-based five-step multi-scale finite element (FsMsFE) simulation framework is developed to describe the time-temperature-dependent viscoelastic behavior of 3D braided four-directional composites. The current analysis was performed via three-scale finite element models, the fiber/matrix (microscopic) representative unit cell (RUC) model, the yarn/matrix (mesoscopic) representative unit cell model, and the macroscopic solid model with homogeneous property. Coupling the time-temperature equivalence principle, multi-phase finite element approach, Laplace transformation and Prony series fitting technology, the character of the stress relaxation behaviors at three scales subject to variation in temperature is investigated, and the equivalent time-dependent thermal expansion coefficients (TTEC), the equivalent time-dependent thermal relaxation modulus (TTRM) under micro-scale and meso-scale were predicted. Furthermore, the impacts of temperature, structural parameters and relaxation time on the time-dependent thermo-viscoelastic properties of 3D braided four-directional composites were studied.

scholarly journals 3D-Finite element modeling of lead rubber bearing using high damping material

2019 ◽  
Vol 276 ◽  
pp. 01013
Author(s):  
Ahmad Basshofi Habieb ◽  
Tavio Tavio ◽  
Gabriele Milani ◽  
Usman Wijaya
Keyword(s):  
Finite Element ◽  
Shear Behaviour ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Fe Model ◽  
Rubber Material ◽  
Isolation System ◽  
Cyclic Shear ◽  
Rubber Bearing ◽  
Lead Rubber Bearing

Lead Rubber Bearing (LRB) has been widely applied for seismic protection of mid and high-rise buildings around the world. Its excellent energy dissipation becomes the most important aspect of this isolation system thanks to the plasticity and recovery behavior of the lead core. Aiming to develop a deeper knowledge on the behavior of LRB’s, a 3D detailed finite element (FE) modeling is performed in Abaqus FE software. Some important parameters involved in the model are plasticity of the lead core and hyper-elasticity and viscosity of the rubber material. The parameters for rubber material are derived from the results of experimental works in the laboratory, including uniaxial tensile test and relaxation test. The bearing model is then subjected to a cyclic shear-test under constant vertical load. The result of the 3D-FE model is then compared with the analytic-Abaqus model for LRB isolators, developed in the literature. Finally, both 3D-FE model and analytic model result in a good agreement on the shear behaviour of the presented LRB.

Tensile Creep Behavior of HPC at Early Ages under Different Curing Temperatures

2011 ◽  
Vol 250-253 ◽  
pp. 434-439 ◽  
Author(s):  
Yang Yang ◽  
Peng Li ◽  
Yan Ping Wu
Keyword(s):  
Creep Rate ◽  
Creep Behavior ◽  
Strength Class ◽  
Concrete Specimen ◽  
Curing Temperature ◽  
Tensile Creep ◽  
Uniaxial Tensile ◽  
Creep Coefficient ◽  
The Difference ◽  
Uniaxial Tensile Creep

This paper presents an experimental investigation on tensile basic creep behavior of HPC at early ages by using a uniaxial tensile creep testing apparatus. Concrete specimens of 100×100×400mm with compressive strength class 60MPa was used, sealed and loaded at different curing temperature. The effects of the curing temperature and the age at loading on creep behavior are discussed. The results show that tensile specific creep and creep rate of HPC at early ages were governed by the age at loading. The specific creep, creep coefficient and creep rate were larger at earlier loading ages, and decreased exponentially with age at loading. The tensile specific creep decreased with curing temperature, but the difference in creep due to different curing temperatures decreased with the age at loading, and could be ignored while concrete specimen being loaded after the age of 7 days.

Investigation on γ-Channel Widening during Uniaxial Creep Test of a Ni-Base Single Crystal Superalloy

2004 ◽  
Vol 449-452 ◽  
pp. 545-548
Author(s):  
Tao Jin ◽  
L.R. Liu ◽  
Na Ru Zhao ◽  
Zhi Wang ◽  
Xiao Feng Sun ◽  
...  
Keyword(s):  
Single Crystal ◽  
Single Crystal Superalloy ◽  
Tensile Creep ◽  
Uniaxial Tensile ◽  
Creep Tests ◽  
Uniaxial Creep ◽  
The Mean ◽  
Channel Widening ◽  
Nickel Base ◽  
Temperature Time

Investigation of γ -channel widening behavior in a nickel-base single crystal superalloy during uniaxial tensile creep tests was carried out. Scanning electron microscopy (SEM) was adopted to reveal the microstructural evolution of γ -channel and the dimension of γ -channel. It was found that different tests condition such as temperature, time and stress in tensile creep tests all influenced the γ -channel widening behavior, and a parabolic rate law governs the mean increase value of γ -channel width. The stress and temperature enhanced the γ -channel widening. The γ -channel widening was the result of directionally diffusion of multiatom.

A Finite Element Model for Ultrasonic Cutting of Toffee

2006 ◽  
Vol 5-6 ◽  
pp. 519-526 ◽  
Author(s):  
E. McCulloch ◽  
Alan MacBeath ◽  
Margaret Lucas
Keyword(s):  
Finite Element ◽  
Failure Criterion ◽  
Uniaxial Tensile ◽  
Test Machine ◽  
Fe Model ◽  
Temperature Dependent ◽  
Erosion Model ◽  
Element Erosion ◽  
Element Removal ◽  
Ultrasonic Cutting

The performance of an ultrasonic cutting device critically relies on the interaction of the cutting tool and the material to be cut. A finite element (FE) model of ultrasonic cutting is developed to enable the design of the cutting blade to be influenced by the requirements of the toolmaterial interaction and to allow cutting parameters to be estimated as an integral part of designing the cutting blade. In this paper, an application in food processing is considered and FE models of cutting are demonstrated for toffee; a food product which is typically sticky, highly temperature dependent, and difficult to cut. Two different 2D coupled thermal stress FE models are considered, to simulate ultrasonic cutting. The first model utilises the debond option in ABAQUS standard and the second uses the element erosion model in ABAQUS explicit. Both models represent a single blade ultrasonic cutting device tuned to a longitudinal mode of vibration cutting a specimen of toffee. The model allows blade tip geometry, ultrasonic amplitude, cutting speed, frequency and cutting force to be adjusted, in particular to assess the effects of different cutting blade profiles. The validity of the model is highly dependent on the accuracy of the material data input and on the accuracy of the friction and temperature boundary condition at the blade-material interface. Uniaxial tensile tests are conducted on specimens of toffee for a range of temperatures. This provides temperature dependent stress-strain data, which characterises the material behaviour, to be included in the FE models. Due to the difficulty in gripping the tensile specimens in the test machine, special grips were manufactured to allow the material to be pulled without initiating cracks or causing the specimen to break at the grips. A Coulomb friction condition at the bladematerial interface is estimated from experiments, which study the change in the friction coefficient due to ultrasonic excitation of a surface, made from the same material as the blade, in contact with a specimen of toffee. A model of heat generation at the blade-toffee interface is also included to characterise contact during ultrasonic cutting. The failure criterion for the debond model assumes crack propagation will occur when the stress normal to the crack surface reaches the tensile failure stress of toffee and the element erosion model uses a shear failure criterion to initiate element removal. The validity of the models is discussed, providing some insights into the estimation of contact conditions and it is shown how these models can improve design of ultrasonic cutting devices.

Dynamic complex modulus predictions of hot-mix asphalt using a micromechanical-based finite element model

2007 ◽  
Vol 34 (12) ◽  
pp. 1519-1528 ◽  
Author(s):  
Zhanping You ◽  
Qingli Dai
Keyword(s):  
Finite Element ◽  
Hot Mix Asphalt ◽  
Complex Modulus ◽  
Asphalt Binder ◽  
Viscoelastic Behavior ◽  
Element Model ◽  
Discrete Element Modelling ◽  
Experimental Program ◽  
Fe Model ◽  
Different Temperatures

A micromechanical-based finite element (FE) model was used to predict the dynamic complex modulus ( E*) of the hot-mix asphalt (HMA). The microstructure of HMA was captured with a high resolution scanner. Two material phases (aggregates and sand mastic) of HMA were modelled with finite elements. The sand mastic herein was composed of fines and asphalt binder with some fine aggregates. The dynamic complex modulus of the sand mastic under different temperatures and loading frequencies was measured in an experimental program. The corresponding principles were applied to bridge the elastic simulation and viscoelastic behavior with the input of the viscoelastic mastic properties. The input parameters in the FE model include the dynamic complex modulus of the sand mastic, the elastic modulus of the aggregates, and the microstructure of the HMA. The E* values of the HMA were measured and used to compare the E* predicted from the FE model. It is found that the FE approach used in this paper has the ability to predict HMA dynamic modulus across a range of temperatures and loading frequencies. The FE prediction of the E* was compared with a recently developed discrete element modelling approach and found the E* prediction from these two approaches to be very similar.

scholarly journals Finite Element Modeling of FRP-Strengthened RC Beam under Sustained Load

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Shiyong Jiang ◽  
Weilai Yao ◽  
Jin Chen ◽  
Tao Cai
Keyword(s):  
Finite Element ◽  
Field Performance ◽  
Adhesive Layer ◽  
Aging Effect ◽  
Time Dependent ◽  
Sustained Load ◽  
Fe Model ◽  
Rc Beam ◽  
Long Term Behavior

External bonding of FRP laminates to the tension soffit of concrete members has become a popular method for flexural strengthening. However, the long-term field performance of FRP-strengthened RC members under service conditions is still a concern, and more work needs to be done. Based on concrete smeared-crack approach, this paper presents a finite-element (FE) model for predicting long-term behavior of FRP-strengthened RC beam, which considers the time-dependent properties of all components including the aging effect of concrete. According to the comparison between theoretical predictions and test results, the validity of the FE model is verified. The interfacial edge stresses in adhesive layer were determined through appropriate mesh refinement near the plate end, and their time-dependent characteristics were investigated. The results show that creep of concrete and epoxy resin cause significant variations of the edge stresses with time. According to the research in this paper, the FE approach is found to be able to properly simulate the long-term behavior of the FRP-strengthened beam and help us better understand the complex changes in the stress state occurring over time.

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