Application of a Modified Arrhenius Equation to Describe the Time-Temperature Equivalence in Relaxation Analysis of Metal Seals

For the application of the time-temperature superposition principle a suitable relation is needed to describe the time-temperature shift factor a. Therefore, the Arrhenius equation is widely used due to its simple form and often leads to suitable results. Where, the Arrhenius equation presents a linear relation for the temperature-dependent shift factor in logarithmic scale ln（α） with the absolute inverse temperature （1/θ）. However, in cases with a large temperature range which eventually include more complex reaction processes, the functional relation between ln（α） and （1/θ） is nonlinear in the ＇Arrhenius plot＇. In those cases, the monotone change of the nonlinear range in the ＇Arrhenius plot＇ can be interpreted as a transient range between two approximately linear or constant regions. An extended application of the modified Arrhenius equation from Nakamura （1989） is presented in this study for this transient range. The introduced method was applied to describe the time-temperature equivalence in the relaxation analysis of restoring seal force of metal seals, which are used in lid-systems of transport and interim storage casks for radioactive materials. But, the method is widely valid and can be used for different objectives which are characterized by thermorheologically simple behavior with nonlinear sensitivity to inverse temperature.

A new flow stress model based on Arrhenius equation to track hardening and softening behaviors of Ti6Al4V alloy

The conventional Arrhenius-type model was adopted to identify the deformation characteristic of Ti6 A14 V(TC4) titanium alloy based on the stress-strain curves of isothermal compression test. A new flow stress model based on Arrhenius equation was proposed for TC4,which is composed of peak flow stress(PFS) prediction and strain compensation. The predicted PFS is set as a reference to derive the flow stress model at any strain ranging from approximately 0 to 0.7. The predictability and efficiency among the proposed model, conventional model,and an existing physical-based model of TC4 were comparatively evaluated. It is found that the newly proposed model can simultaneously track the hardening and softening behaviors of TC4 through a single expression while the other existing models are only valid in the softening region.Besides, the wider application range and acceptable accuracy of the new model have been achieved by fewer material constants with much-simplified modeling procedure than the other models.

Arrhenius relationship and two-step scheme in AF hyperdynamics simulation of diffusion of Mg/Zn interface

The accelerating factor （AF） method is a simple and appropriate way to investigate the atomic long-time deep diffusion at solid-solid interface. In the framework of AF hyperdynamics （HD） simulation, the relationship between the diffusion coefficient along the direction of z-axis which is normal to the Mg/Zn interface and temperature was investigated, and the AF＇s impact on the diffusion constant （D0） and activation energy （Q^＊） was studied. Then, two steps were taken to simulate the atomic diffusion process and the formation of new phases： one for acceleration and the other for equilibration. The results show that： the Arrhenius equation works well for the description of Dz with different accelerating factors; the AF has no effect on the diffusion constant Do in the case of no phase transition; and the relationship between Q＊ and Q conforms to Q^＊=Q/A. Then, the new Arrhenius equation for AFHD is successfully constructed as Dz=Doexp[-Q/（ART）]. Meanwhile, the authentic equilibrium conformations at any dynamic moment can only be reproduced by the equilibration simulation of the HD-simulated configurations. Key words： accelerating factor method; Arrhenius equation; two-steps scheme; Mg/Zn interface; hyperdynamic simulation

Prediction of Hot Deformation Behavior of 7Mo Super Austenitic Stainless Steel Based on Back Propagation Neural Network

The hot compression tests of 7Mo super austenitic stainless(SASS)were conducted to obtain flow curves at the temperature of 1000-1200℃and strain rate of 0.001 s^(-1)to 1 s^(-1).To predict the non-linear hot deformation behaviors of the steel,back propagation-artificial neural network(BP-ANN)with 16×8×8 hidden layer neurons was proposed.The predictability of the ANN model is evaluated according to the distribution of mean absolute error(MAE)and relative error.The relative error of 85%data for the BP-ANN model is among±5%while only 42.5%data predicted by the Arrhenius constitutive equation is in this range.Especially,at high strain rate and low temperature,the MAE of the ANN model is 2.49%,which has decreases for 18.78%,compared with conventional Arrhenius constitutive equation.

Observations on Arrhenius Degradation of Lithium-Ion Capacitors

Earlier research determined that lithium-ion capacitor (LIC) cycle life degradation can be accelerated by elevated temperature. LIC cycle life degradation can be described by an Arrhenius equation. This study performed cycle life testing at a constant temperature but varied cycle current. The results were described by an Arrhenius equation relying upon the number of cycles and a constant, which was determined by cycle current. Using mathematical derivations and experimental results, the researchers quantified the effects of activation energy and temperature upon this constant. Because cell temperature is nearly constant during cycles, it was deduced that elevated cycle current decreases activation energy. This lower activation energy then accelerates degradation. Thus this research demonstrates that cycle current ages LICs through its effects on their activation energies.

A Model for Temperature Infl uence on Concrete Hydration Exothermic Rate (Part one: Theory and Experiment)

Recent achievements in concrete hydration exothermic models based on Arrhenius equation have improved computation accuracy for mass concrete temperature field. But the properties of the activation energy and the gas constant （Ea/R） have not been well studied yet. From the latest experiments it is shown that Ea/R obviously changes with the hydration degree without fixed form. In this paper, the relationship between hydration degree and Ea/R is studied and a new hydration exothermic model is proposed. With those achievements, the mass concrete temperature field with arbitrary boundary condition can be calculated more precisely.

Promote the conductivity of solid polymer electrolyte at room temperature by constructing a dual range ionic conduction path

Poly(ethylene oxide)(PEO)is a classic matrix model for solid polymer electrolyte which can not only dissociate lithium-ions(Li^(+)),but also can conduct Li^(+) through segmental motion in long-range.However,the crystal aggregation state of PEO restricts the conduction of Li^(+) especially at room temperature.In this work,an amorphous polymer electrolyte with ethylene oxide(EO)and propylene oxide(PO)block structure(B-PEG@DMC)synthesized by the transesterification is firstly obtained,showing an ionic conductivity value of 1.1×10^(5) S/cm at room temperature(25℃).According to the molecular dynamics(MD)simulation,the PO segments would lead to an inconsecutive and hampered conduction of Li^(+),which is not beneficial to the short range conduction of Li^(+).Thus the effect of transformation of aggregation state on the improveme nt of ionic conductivity is not eno ugh,it is n ecessary to further consider the differe nt coupled behaviours of EO and PO segments with Li^(+).In this way,we blend this amorphous polymer(B-PEG@DMC)with PEO to obtain a dual range ionic conductive solid polymer electrolyte(D-SPE)with further improved ionic conductivity promoted by constructing a dual range fast ionic conduction,which eventually shows a further improved ionic conductivity value of 2.3×10^(5) S/cm at room temperature.

Temperature Sensitivity of Nitrogen Dynamics of Agricultural Soils of the United States

Soil temperature controls gaseous nitrogen losses through nitrous oxide (N2O) and ammonia (NH3) fluxes. Eight surface soils from agricultural fields across the United States were incubated at 10°C, 20°C, and 30°C, and N2O and NH3 flux were measured twice a week for 91 and 47 d, respectively. Changes in cumulative N2O and NH3 flux and net N mineralization at three temperatures were fitted to calculate Q10 using the Arrhenius equation. For the majority of soils, Q10 values for the N2O loss ranged between 0.23 and 2.14, except for Blackville, North Carolina (11.4) and Jackson, Tennessee (10.1). For NH3 flux, Q10 values ranged from 0.63 (Frenchville, Maine) to 1.24 (North Bend, Nebraska). Net soil N mineralization-Q10 ranged from 0.96 to 1.00. Distribution of soil organic carbon and total soil N can explain the variability of Q10 for N2O loss. Understanding the Q10 variability of soil N dynamics will help us to predict the N loss.

Investigation of Hydrous Pyrolysis on Type-Ⅱ Kerogen-bearing Source Rocks from Iran and its Application in Geochemical and Kinetic Analyses of Hydrocarbon Products

Hydrous pyrolysis(HP)practiced on type-Ⅱ kerogen-bearing oil shale samples from the Sargelu Formation in the Ghali-Kuh Area,western Iran,using a specially designed apparatus was performed at different temperatures(250-350℃),with hydrocarbon generation evaluated at each temperature.For comparison,the samples subjected to Rock-Eval pyrolysis before proceeding to HP resulted in T_(max)=418℃,HI=102,and TOC=4.33%,indicating immaturity and hence remarkable hydrocarbon(especially oil)generation potential,making them appropriate for HP.Moreover,the samples were deposited in a low-energy reductive marine environment,with maximum oil and gas generation(739 mg and 348 mg out of50 g of rock sample,respectively)observed at 330℃ and 350℃,respectively.The oil generated at 330℃ was subjected to gas chromatography(GC)and isotopic analyses to assess hydrocarbon quality and composition.The hydrocarbon generation data was devised to estimate kinetic indices of the Arrhenius equation and to investigate the gas-oil ratio(GOR)and overall conversion yield.Based on the producible hydrocarbon quantity and quality,the findings contribute to the economic assessment of oil shales across the study area.The developed kinetic model indicates the history of hydrocarbon generation and organic matter(OM)maturity.

Dielectric properties and relaxation dynamics in PbF_2-TeO_2-B_2_O3-Eu_2O_3 glasses

Frequency and temperature dependent dielectric dispersion of 20PbF2？20TeO2？（60？x）B2O3？xEu2O3（x=0 to 2.5, mole fraction, %） glasses prepared by the melt？quenching technique were investigated in the frequency range 1 Hz？10 MHz and temperature range 313？773 K. Dielectric relaxation dynamics was analyzed based on the electric modulus behavior. Dielectric losses （tanδ） are found to be negligibly small in the temperature range 313？523 K, proving good thermal stability of the glasses. The present Eu2O3-doped oxyfluroborate glasses showed low dielectric loss at higher frequency and lower temperature, proving their suitability for nonlinear optical materials.

Application of time-temperature superposition method in thermal aging life prediction of shipboard cables

The life of shipboard cables will decrease due to the complex aging processes. In terms of the safety perspective, remaining life prediction of the cable is essential to maintain a reliable operation. In this paper, firstly, based on Arrhenius equation, residual life of new styrene-butadiene cable is calculated; result indicates that the degradation rate which changes with time is proportional to thermal temperature. Then second order dynamic model is adopted into the residual life prediction, combined with the time-temperature superposition method(TTSP), and a new residual life model is proposed. According to the accelerated thermal aging experiment data and Arrhenius equation, TTSP method demonstrates to be an efficient way for life prediction, and life at normal temperature can be estimated by this model. In order to monitor the state of styrene-butadiene cable more accurately, an improved residual life model based on equivalent environment temperature of cable is proposed, and life of cable under real operation is analyzed. Result indicates that this model is credible and reliable, and it provides an important theoretical base for residual life of cables.

Experiment research on mechanical behavior of the aluminum laminate in the low-high temperature

Aluminum laminate is one kind of the rigidizable composite materials and plays an important role in construction of the inflatable space structure(ISS),which has potential application in space in the future.But the study of the predecessors mainly focuses on the research of the mechanical behavior in the room temperature,for this reason,mechanical properties of the aluminum laminate in low-high temperature have been studied in this paper.The failure mechanism of the aluminum laminate is also analyzed in the microscopic view by JCXA-T33 electron probe.The results show uhat the temperature has significant influence on the strength and Young's modulus of the aluminum laminate.With the increase of temperature,both the strength and Young's modulus of the aluminum laminate decrease.A model between Young's modulus of the aluminum laminate and temperatures is obtained by using Arrhenius equation.The predicted values by the model agree well with the experiment values.

The Application of Maturity Method on Whitetopping Construction

The primary objective of this study was to assess the use of the maturity method to determine the joint sawing window and the traffic opening time on whitetopping construction in Korea. To determine joint sawing time, it was necessary to find the minimum strength not to cause raveling and to identify the time to the occurrence of drying shrinkage. This study found that the minimum compressive strength for joint sawing was 4.41MPa （45kg/cm2） and drying shrinkage occurred just after the concrete temperature reached at the peak. To develop the relationship between compressive strength and maturity values, thermachron i-buttons were inserted into the top and mid-depth of the fresh concrete in the test slabs. The results of the laboratory tests indicated that the Arrhenius equation better fitted the relationship between the compressive strength and maturity values than did the Nurse-Saul equation. However, the Nurse-Saul function estimated in-place strength quite well in this study. Therefore, the Nurse-Saul equation was used to determine the joint sawing window and the traffic opening time for whitetopping construction.

Comparison of flow behaviors of near beta Ti-55511 alloy during hot compression based on SCA and BPANN models

The flow behavior of Ti-55511 alloy was studied by hot compression tests at temperatures of 973−1123 K and strain rates of 0.01−10 s^(−1).Strain-compensated Arrhenius(SCA)and back-propagation artificial neural network(BPANN)methods were selected to model the constitutive relationship,and the models were further evaluated by statistical analysis and cross-validation.The stress−strain data extended by two models were implanted into finite element to simulate hot compression test.The results indicate that the flow stress is sensitive to deformation temperature and strain rate,and increases with increasing strain rate and decreasing temperature.Both the SCA model fitted by quintic polynomial and the BPANN model with 12 neurons can describe the flow behaviors,but the fitting accuracy of BPANN is higher than that of SCA.Sixteen cross-validation tests also confirm that the BPANN model has high prediction accuracy.Both models are effective and feasible in simulation,but BPANN model is superior in accuracy.

Variation of activation energy determined by a modified Arrhenius approach:Roles of dynamic recrystallization on the hot deformation of Ni-based superalloy

The hot deformation behaviors of Ni18 Cr9 Co9 Fe5 Nb3 Mo superalloy were explored in the formation temperature range free ofγ’phase with various strain rates applied.The hot deformation behaviors are initially modeled with Arrhenius equation which gives an average activation energy of 581.1 kJ mol^(-1).A modified Arrhenius approach,including the updated Zener-Hollomon parameter is proposed to consider the change of activation ene rgy under different deformation conditions which turns out a relatively accurate computation for activation energy of hot deformation,i.e.,the standard variance for modified model calculated in the covered deformation condition is just 35.4%of that for Arrhenius equation.The modified model also proposes a map for activation ene rgy which ranges from 571.5-589.0 kJ mol^(-1)for various deformation conditions.Microstructural features of the representative superalloy specimens were characterized by electron backscattered diffraction(EBSD)techniques in order to clarify the influence of activation energy on the microstructural formation.It is found that the Ni-based superalloy samples with higher activation energy are promoted by the degree of dynamic recrystallization which suggests that the rise in activation energy gives either a better recrystallization rate or finer grains.

Phase separation time/temperature dependence of thermoplastics-modified thermosetting systems

The cure-induced phase separation processes of various thermoplastics(TP)-modified thermosetting systems which show upper critical solution temperature(UCST)or lower critical solution temperature(LCST)were studied with emphasis on the temperature dependency of the phase separation time and its potential application in the cure time-temperature processing window.We found that the phase separation time/temperature relationship follows the simple Arrhenius equation.The cure-induced phase separation activation energy E_(a)(ps)generated from the linear fitting of the Arrhenius equation is irrelevant to the detection means of phase separation time.We also found that E_(a)(ps)is insensitive to TP content,TP molecular weight and curing rate,but it changes with the cure reaction kinetics and the chemical environment of the systems.With the established phase separation time-temperature dependence relation,we can easily establish the whole cure time-temperature transformation(TTT)diagram with morphology information which is a useful map for the TP/TS composites processing industry.

Constitutive Model for F45V Microalloyed Forging Steel at High Temperature

Isothermal hot compression experiments of F45V, a microalloyed steel, were performed on a Gleeble-1500 thermo-mechanical simulator at temperatures of 950--1200 ;C and strain rate of 0.01--10 s -1. Based on the experi- mental flow stress curves, a constitutive model that was expressed by the hyperbolic laws in an Arrhenius-type equa- tion was established, and the material parameters of the model were expressed as 6th order polynomial form of strain. Standard statistical parameters such as correlation coefficient and average absolute relative error were em- ployed to quantify the predictability of the model. They were found to be 0. 995 and 4.34% respectively. The results show that the established constitutive mode[ can predict the magnitude and tendency of flow stress with the increase of deformation accurately, and can be used for the numerical simulation of hot forging process of the F45V steel.