Experimental characterization and viscoelastic modeling for thermo-mechanical creep of 1-3 piezocomposites

2019 ◽  
Vol 30 (7) ◽  
pp. 1018-1030 ◽  
Author(s):  
Ratnadeep Pramanik ◽  
Arunachalakasi Arockiarajan
Keyword(s):  
Creep Strain ◽  
Elevated Temperatures ◽  
Viscoelastic Model ◽  
Thermal Loads ◽  
Fiber Volume ◽  
Fractal Derivative ◽  
Model Predictions ◽  
Overall Performance ◽  
Mechanical Creep ◽  
Viscoelastic Modeling

1-3 piezocomposites are often subjected to mechanical pre-stress under elevated temperatures in naval and offshore applications, actuators, and so on, where the presence of the ductile epoxy matrix causes considerable creep in the system. This deteriorates the system efficiency and its overall performance. To address this issue, experiments are performed to capture the electromechanical response for thermo-mechanical creep of 1-3 piezocomposites for different fiber volume fractions under various thermal loads, wherein mechanical depolarization is observed. The piezo-coupling coefficient is observed to degrade. Higher thermal loads resulted in an increase in creep strain coupled with a decrease in creep polarization. A Kelvin–Voigt fractal derivative viscoelastic model is used to capture the creep strain. The creep strain is decomposed into ferroelastic and anelastic parts. The evolution of creep polarization is obtained using the ferroelastic component of the creep strain. The model predictions are found to be in agreement with the experimental observations.

scholarly journals Prediction of creep behavior of laminated woven fabric with adhesive interlining under low stress in the bias direction

2016 ◽  
Vol 87 (3) ◽  
pp. 285-295 ◽  
Author(s):  
Masayuki Takatera ◽  
Ken Ishizawa ◽  
KyoungOk Kim
Keyword(s):  
Creep Strain ◽  
Creep Behavior ◽  
Viscoelastic Model ◽  
Element Model ◽  
Woven Fabric ◽  
Creep Model ◽  
Creep Tests ◽  
Viscoelastic Models ◽  
Experimental Creep ◽  
The Face

The effect of adhesive interlining on the creep behavior of a woven fabric in the bias direction was investigated. Three-element viscoelastic models were used to approximate the creep behavior of a face fabric and adhesive interlining. The creep model of a laminated fabric comprised a six-element model in which two three-element models are connected in parallel with the three-element model. Creep tests were carried out using face fabrics, adhesive interlinings, and their laminated fabrics without and with bonding adhesive interlining by hanging samples in the 45° bias direction under their own weight for 7 days. Creep strains of face fabrics bonded with adhesive interlining were found to be weaker than those of the face fabrics. The creep behavior for the face and interlining fabrics could be approximated using the three-element viscoelastic model with appropriate parameters. The experimental creep behavior of a laminated fabric without bonding was similar to the theoretical behavior. However, the experimental creep of laminated fabrics with bonding interlining was less than the calculated creep, owing to the increase in stiffness due to the adhesive. By revising the six-element model with the strains just after hanging and for 2 days, it was possible to predict the creep strain over 7 days.

scholarly journals High temperature bi-axial low cycle fatigue behaviour of railway wheel steel

2019 ◽  
Vol 300 ◽  
pp. 07001
Author(s):  
Dimitrios Nikas ◽  
Johan Ahlström
Keyword(s):  
Elevated Temperatures ◽  
Low Cycle Fatigue ◽  
Carbon Steels ◽  
Uniaxial Loading ◽  
Dynamic Strain ◽  
Thermal Loads ◽  
Cycle Fatigue ◽  
Dynamic Strain Ageing ◽  
Proportional Loading ◽  
Biaxial Tests

One of the most important aspects in railway operation is the interaction between rail and wheel. Railway wheels are commonly made from medium carbon steels (∼ 0.55 wt.% C), heat treated to a near pearlitic microstructure with some 5–10% pro-eutectoid ferrite. During the operation of freight trains, where block brakes are used, high thermal loads are evolved because of recurring braking and occasional slippage. Thus the combination of mechanical and thermal loads leads to changes in the mechanical properties of the material. The focus of the current investigation is to evaluate the mechanical behaviour of wheel material (UIC ER7T) subjected to non-proportional biaxial fatigue loading, as this simulates the actual working conditions in a better way than uniaxial loading. Axial-torsional low cycle fatigue tests were performed at room temperature and elevated temperatures using thin walled specimens to study the cyclic stress-strain properties of this material. The results showed large influence of temperature on the ratcheting behaviour of the material. Biaxial non-proportional loading gave much higher strain hardening as compared to uniaxial loading. Hardening due to dynamic strain ageing can be seen in the biaxial tests at temperatures around 300°C.

Effect of Hydrogen on Creep Behavior of a Vanadium-Modified CRMO Steel and its Continuum Damage Analysis

2018 ◽  
Author(s):  
Yu Zhou ◽  
Xuedong Chen ◽  
Zhichao Fan ◽  
Peng Xu ◽  
Xiaoliang Liu
Keyword(s):  
Constitutive Model ◽  
Creep Strain ◽  
Creep Behavior ◽  
Hydrogen Pressure ◽  
Damage Mechanics ◽  
Elevated Temperatures ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Methane Pressure ◽  
Crmo Steel

Creep properties both in hot hydrogen and in air of a vanadium-modified CrMo steel 2.25Cr1Mo0.25V, widely used in hydroprocessing reactors in petrochemical industry, were investigated to determine the effect of hydrogen on high-temperature creep behavior of the low-alloy ferritic steel. The minimum creep strain rate in hydrogen is higher than that in air, whereas the creep strain at failure in hydrogen is relatively smaller. Many tiny spherical cavities are dispersively distributed in the ruptured specimen under hydrogen, which has relatively higher Vickers hardness. Based on the thermodynamics theory, the pressure of methane generated by the so-called “methane reaction” in the vanadium-modified CrMo steel can be calculated by using corresponding thermodynamic data, assuming that methane can reach its equilibrium state during cavitation. Meanwhile, a creep constitutive model based on continuum damage mechanics (CDM) was proposed, taking methane pressure into consideration. The results show that methane pressure increases nonlinearly with increase of hydrogen pressure while it decreases gradually with increase of temperature. The constitutive model considering the damage induced by methane pressure can be used to predict the effect of hydrogen pressure and temperature on creep life, indicating that the influence of hydrogen at elevated temperatures becomes smaller when increasing temperature or decreasing hydrogen pressure.

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.

Characterization of Hybrid Joining Techniques for FRP/Steel-Structures under Combined Mechanical and Thermal Loading

2017 ◽  
Vol 742 ◽  
pp. 358-365
Author(s):  
Marvin Hoepfner ◽  
Torben Becker ◽  
Daniel Huelsbusch ◽  
Frank Walther
Keyword(s):  
Thermal Loading ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Measurement Techniques ◽  
Acoustic Emissions ◽  
Steel Structures ◽  
Shear Stresses ◽  
Thermal Loads ◽  
Simultaneous Application ◽  
Hybrid Joining

In order to optimize the design of vibrating screening machines and realize significant weight reductions, the use of hybrid structures is gaining importance. In this context, the joining of FRP and steel and their interactions due to different material properties were investigated. Therefore, quasi-static tests with combined mechanical and thermal loads were carried out. To realize the simultaneous application of physical measurement techniques, e.g. optical and acoustic measurements, and thermal loads, short-wave infrared emitter technique was used instead of thermal chambers. Thus, the mechanical characteristics and acoustic emissions could be determined and assessed. The results show different structural mechanisms of hybrid joining at room and elevated temperatures. The characteristics of failure modes, shear stresses, strains and acoustic emissions could be correlated to determine the damage developments and mechanisms.

Creep-Environment Interactions of Alloy 617 at Elevated Temperature

2008 ◽  
Author(s):  
Daejong Kim ◽  
Changheui Jang ◽  
Woo Seog Ryu
Keyword(s):  
High Temperature ◽  
Creep Strain ◽  
Elevated Temperatures ◽  
Extended Period ◽  
Nickel Base Superalloy ◽  
Environment Interaction ◽  
Creep Tests ◽  
Alloy 617 ◽  
Creep Properties ◽  
Deformation Properties

Creep behavior and degradation of creep properties of high-temperature materials often limit the lives of components and structures designed to operate for extended period under stress at elevated temperatures. A nickel-base superalloy, Alloy 617 in particular which is considered as a prospective material for hot gas duct and intermediate heat exchanger in very high temperature gas cooled reactor, was studied for creep properties. Creep tests were carried out under various sustained tensile loadings in air and helium environments at temperature of 800°C, 900°C, and 1000°C. Times for 1% creep strain and creep rupture were taken from the short-term creep tests within 1000 hours. Effect of creep-environment interaction on creep strain and changes in viscous deformation properties by dynamic recrystallization were discussed.

Ultrasonic Assessment of Interfacial Oxidation Damage in Ceramic Matrix Composites

1993 ◽  
Vol 115 (3) ◽  
pp. 237-243 ◽  
Author(s):  
Y. C. Chu ◽  
S. I. Rokhlin ◽  
G. Y. Baaklini
Keyword(s):  
Elevated Temperatures ◽  
Volume Fraction ◽  
Micromechanical Model ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Fiber Direction ◽  
Matrix Composites ◽  
Fiber Volume ◽  
Ultrasonic Methods ◽  
Oxidation Damage

A new approach to characterizing oxidation damage in ceramic matrix composites using ultrasonic techniques is proposed. In this approach the elastic constants of the composite are determined nondestructively by measuring the angular dependence of both longitudinal and transverse wave velocities. A micromechanical model for composites with anisotropic constituents is used to find the anisotropic properties of an effective fiber which is a combination of the fiber and the interface. Interfacial properties are extracted from the properties of this effective fiber by analyzing the difference between effective and actual fiber properties. Unidirectional [0]28 SiC/Si3N4 composites with 30 percent fiber volume fraction and 30 percent matrix porosity are used. The samples are exposed in a flowing oxygen environment at elevated temperatures, up to 1400°C, for 100 hours and then measured by ultrasonic methods at room temperature. The Young’s modulus in the fiber direction of the sample oxidized at 600° C decreased significantly but it was unchanged for samples oxidized at temperatures above 1200° C. The transverse moduli obtained from ultrasonic measurements decrease continuously up to 1200°C. The shear stiffnesses show behavior similar to the transverse moduli. The effective elastic moduli of the interfacial carbon coating are determined from the experimental data and their change due to thermal oxidation is discussed.

Study on Relationship Between Dislocation Density and Creep Strain Rate of Single Crystal Ni Based Superalloy for Gas Turbines Using the Discrete Cosine Transform

2021 ◽  
Author(s):  
Hideo Hiraguchi
Keyword(s):  
Dislocation Density ◽  
Strain Rate ◽  
Single Crystal ◽  
Creep Strain ◽  
Discrete Cosine Transform ◽  
Gas Turbines ◽  
Elevated Temperatures ◽  
Creep Strain Rate ◽  
Cosine Transform ◽  
Term Creep

Abstract The discrete cosine transform (DCT) is known to be able to express the relation curve between creep strain and time, or the relation curve between creep strain rate and time very well. Moreover, recently it has been found out that the DCT can draw electron density distribution maps of crystals. In addition, the DCT always passes through all the points measured at an equal interval in any continuous curves and its interpolated values between adjacent points are very reasonable. Furthermore, a new prediction method for long term creep curves from short term creep data by using the DCT was reported at TurboExpo2020. Up to the present, the strength of single crystal Nickel based superalloys for gas turbines at elevated temperatures has been advanced by controlling the interface dislocation density and the lattice misfit at the γ/γ’ interfaces. For this reason, it has to be understood how to evaluate a relationship between interface dislocation density and creep strain rate to develop more advanced single crystal Nickel based superalloys. Therefore, in this research it was studied how to evaluate the relationship between interface dislocation density and creep strain rate of a single crystal Nickel based superalloy for gas turbines by using the DCT. As a result, useful properties on the effective stress have been obtained from the coefficients of the DCT.

Hysteresis and Viscoelastic Modeling of a Piezo-Optic Voltage Sensor

2008 ◽  
Author(s):  
Charles E. Seeley ◽  
Glen Koste ◽  
Craig Stringer
Keyword(s):  
Viscoelastic Model ◽  
Voltage Sensor ◽  
Sensor Technology ◽  
Optical Wave ◽  
Viscoelastic Effects ◽  
Standard Linear Solid ◽  
Standard Linear ◽  
Optical Wave Guide ◽  
Electro Magnetic ◽  
Viscoelastic Modeling

There is growing interest in sensor technology that is immune to electro-magnetic interference. By nature, development of this technology covers multiple physical domains including electronics, optics, mechanics and materials. This paper discusses development of a mathematical model to compensate for the hysteresis and viscoelastic effects of a piezo-optic voltage sensor. The sensor utilizes piezoelectric fibers with interdigitated electrodes coupled to an optical wave guide via a dielectric matrix. The unknown voltage energizes the piezoelectric fibers to deform fiber Bragg gratings (FBGs) on the waveguide. Therefore, a measurable change in wavelength is related to the unknown voltage. The hysteresis model is based on Rayleigh’s Law of magnetization that is adapted for the coupled piezoelectric and optic response, and the viscoelastic model is based on the standard linear solid model using springs and dashpots in combination. Model results compare favorably with experimental results.

Effects of CO2 on Carbon Nanotube Formation from Thermal Decomposition of Ethylene

2015 ◽  
Vol 1747 ◽  
Author(s):  
Chuanwei Zhuo ◽  
Fariba Khanshan ◽  
Richard West ◽  
Henning Richter ◽  
Yiannis A. Levendis
Keyword(s):  
Thermal Decomposition ◽  
Gas Phase ◽  
Vapor Deposition ◽  
Elevated Temperatures ◽  
Chemical Vapor ◽  
Tubular Structures ◽  
Ethylene Decomposition ◽  
Model Predictions ◽  
Simulation Results

AbstractCatalytic chemical vapor deposition (CVD) is a popular method to synthesize carbon nanotubes (CNTs). At the presence of catalysts (usually trasition metals), the hydrocarbon feedstock decomposes controllably at elevated temperatures and can form tubular structures. It has been suggested that trace amounts of weak gas-phase oxidants, such as CO2, can enhance the CNT synthesis by extending the catatlyst life. It is not clear, however, how such additives affect the CVD reaction environment. In this study, ethylene gas was introduced to a preheated furnace/CVD reactor where meshes of stainless steel were placed. Therein ethylene was thermally decomposed in nitrogen mixed with different amounts of carbon dioxide. The meshes served as catalytic substrates for the CNT growth. The compositions of the ethylene pyrolyzates were analysed both with and without the presence of catalysts, to explore the possible contributions of CO2 addition to the CNT formation. The latter compositions were compared with kinetic model predictions of the thermal decomposition of ethylene. Both experimental and simulation results indicated that 1,3-butadiene (C4H6) was the most abundant hydrocarbon species of ethylene decomposition (at 800 °C) and that decomposition was inhibitted at the presence of CO2. A commesurate effect on CNT formation was observed experimentally, whereas the quality of CNTs got improved.

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