Dynamic failure of dry and fully saturated limestone samples based on incubation time concept

This paper outlines the results of experimental study of the dynamic rock failure based on the comparison of dry and saturated limestone samples obtained during the dynamic compression and split tests. The tests were performed using the Kolsky method and its modifications for dynamic splitting. The mechanical data(e.g. strength, time and energy characteristics) of this material at high strain rates are obtained. It is shown that these characteristics are sensitive to the strain rate. A unified interpretation of these rate effects, based on the structuraletemporal approach, is hereby presented. It is demonstrated that the temporal dependence of the dynamic compressive and split tensile strengths of dry and saturated limestone samples can be predicted by the incubation time criterion. Previously discovered possibilities to optimize(minimize) the energy input for the failure process is discussed in connection with industrial rock failure processes. It is shown that the optimal energy input value associated with critical load, which is required to initialize failure in the rock media, strongly depends on the incubation time and the impact duration. The optimal load shapes, which minimize the momentum for a single failure impact, are demonstrated. Through this investigation, a possible approach to reduce the specific energy required for rock cutting by means of high-frequency vibrations is also discussed.

Microscopic phase-field simulation for nucleation incubation time of Ni_(75)Al_xV_(25-x)alloy

With the microscopic phase-field dynamic model, the effects of temperature and concentration on the nucleation incubation time of Ni75AlxV25-x alloy were studied and the relation between the incubation time and precipitation mechanism was investigated by using the atomic occupation probability picture and average order parameter curve. The simulation results demonstrate that there exists the incubation time for different precipitation mechanisms~ such as non-classical nucleation, the mixed style of non-classical nucleation and spinodal decomposition, and spinodal ordering; and the incubation time shortens in turn for the three kinds of mechanisms. With the increase of Al content of Ni75AlxV25-x alloy, the incubation time of Llz phases shortens continuously and that of DOzz phases is prolonged. The effects of temperature on the incubation time of Llz and DOzz phases are accordant, i.e. the incuba- tion time is greatly prolonged with the temperature rising.

Incubation time fracture criterion for FEM simulations

The paper is discussing problems connected with embedment of the incubation time criterion for brittle fracture into finite element computational schemes. Incubation time fracture criterion is reviewed; practical questions of its numerical implementation are extensively discussed. Several examples of how the incubation time fracture criterion can be used as fracture condition in finite element computations are given. The examples include simulations of dynamic crack propagation and arrest, impact crater formation （i.e. fracture in initially intact media）, spall fracture in plates, propagation of cracks in pipelines. Applicability of the approach to model initiation, development and arrest of dynamic fracture is claimed.

Modeling of Incubation Time for Austenite to Ferrite Phase Transformation

On the basis of the classical nucleation theory, a new model of incubation time for austenite to ferrite transformation has been developed, in which the effect of deformation on austenite has been taken into consideration. To prove the precision of modeling, ferrite transformation starting temperature （Ar3） has been calculated using the Scheil＇s additivity rule, and the Ar3 values were measured using a Gleeble 1500 thermomechanical simulator. The Ar3 values provided by the modeling method coincide with the measured ones, indicating that the model is precise in oredicting the incubation time for austenite to ferrite transformation in hot deformed steels.

EFFECT OF AUSTENITE DEFORMATION ON ISOTHERMAL INCUBATION TIME OF PROEUTECTOID FERRITE NUCLEATION

A calculation method for the isothermal nucleation incubation time of pro-eutectoid ferrite formed from deformed austenite has been developed by introducing Feder's incubation time expression into the decomposition of deformed austenite.The effects of austenite deformation stored energy and austenite grain boundary energy change on the incubation time have been theoretically calculated and the rule of calculated results is consistent with that of experiments,this confirms that austenite deformation stored energy and the change of austenite grain boundary energy are the natural effect of austenite deformation on ferrite nucleation.

Evaluation of Energy Saving Operational Modes for Industrial Fracture Connected Processes on the Basis of Incubation Time Fracture Criterion

A problem for a central crack in a plate subjected to plane strain conditions is investigated. Mode I crack loading is created by a dynamic pressure pulse applied at a large distance from the crack. It was found that for a certain combination of amplitude and duration of the pulse applied, the energy transmitted to the sample has a strongly marked minimum, meaning that with the pulse amplitude or duration moving away from the optimal values, minimum energy required for initiation of crack growth increases rapidly. The results obtained indicate a possibility to optimise energy consumption of different industrial processes connected with fracture. Much could be gained in, for example, drilling or rock pounding where energy input accounts for the largest part of the process cost. Presumably further investigation of the effect observed can make it possible to predict optimal energy saving parameters, i.e. frequency and amplitude of impacts, for industrial devices, e.g. bores, grinding machines, and hence significantly reduce the process cost. The pre- diction can be given based on the parameters of the media fractured （material parameters, prevalent crack length and orientation, etc.）.

Optimization of Bacterial Doses and Incubation Time on Bio-Ehanol Fermentation of Nipah （Nypa fruticans） for Biofuel Energy

Nipah （Nypafruticans） is a species of palm trees that grows in mangroves environment near the sea shore. Nipah is potential to produce biofuel energy. The purposes of this research were 1） to determine the optimum bacterial concentration for fermentation to produce high concentration of bio-ethanol, and 2） to determine the optimum incubation time for fermentation to produce high concentration of bio-ethanol. The research had been conducted from June until November 2009 using nipah sap as the substrate and Saceharomyces cerevisiae as a fermentation starter. The experimental design used was a randomized block design （RBD）. Factors tested were starter concentration （5%, 7.5%, 10%） and incubation time （2, 4, 6 days）. The variables observed were concentration of reducing sugar, total microorganism （CFU/mL）, and bio-ethanol production. The results showed that the highest yield of bio-ethanol （8.98%） was produced with 7.5% of starter concentration and 6 days of incubation time.

Incubation time approach in rock fracture dynamics

The paper is summarizing latest results connected with application of the incubation time approach to problems of dynamic fracture of rock materials. Incubation time based fracture criteria for intact media and media with cracks are discussed. Available experimental data on high rate fracture of different rock materials and incubation time based fracture criteria are used in order to evaluate critical parameters of causing fracture in these materials. Previously discovered possibility to optimize (minimize) energy input for fracture is discussed in connection to industrial rock fracture processes. It is shown that optimal value of momentum associated with critical load in order to initialize fracture in rock media does strongly depend on the incubation time and the impact duration. Existence of optimal load shapes minimizing momentum for a single fracturing impact or a sequence of periodic fracturing impacts is demonstrated.

Effects of Temperature on Determination of Protein Concentration with Coomassie Brilliant Blue Method

[Objective] This study aimed to investigate the effects of temperature on determination of protein concentration with Coomassie Brilliant Blue method,thus proving advice and guidance for accurate determination of protein concentration.[Method] With Coomassie Brilliant Blue method,the concentrations of different bovine serum albumin samples were determined under different temperatures and incubation time.[Result] According to the standard curve,when the determination range of protein concentration was 0-100 mg/ml,the determined protein concentration was relatively stable after incubation at 20 ℃ for 20-30 min.Furthermore,the determination result of higher protein concentration with Coomassie Brilliant Blue method was less affected by various factors.[Conclusion] In determination of protein concentration with Coomassie Brilliant Blue method,temperature,sample concentration and incubation time were important factors affecting the accuracy of experimental results.

Effects of Heating Rate on the Process Parameters of Superplastic Forming for Zr_(55)Cu_(30)Al_(10)Ni_5

We investigated the effects of heating rate on the process parameters of superplastic forming for Zr55Cu30Al10Ni5 by differential scanning calorimetry. The continuous heating and isothermal annealing analyses suggested that the temperatures of glass transition and onset crystallization are heating rate-dependent in the supercooled liquid region. Then, the time-temperature-transformation diagram under different heating rates indicates that increasing the heating rate can lead to an increase of the incubation time at the same anneal temperature in the supercooled liquid region. Based on the Arrhenius relationship, we discovered that the incubation time increases by 1.08-1.11 times with double increase of the heating rate at the same anneal temperature, and then verified it by the data of literatures and the experimental results. The obtained curve of the max available incubation time reveals that the incubation time at a certain anneal temperature in the supercooled liquid region is not infinite, and will increase with increasing heating rate until this temperature shifts out of the supercooled liquid region because of exceeding critical heating rate. It is concluded that heating rate must be an important processing parameter of superplastic forming for Zr55Cu30Al10Ni5.

CRACK PROPAGATION IN THE POWER-LAW NONLINEARVISCOELASTIC MATERIAL

An analysis on crack creep propagation problem of power-law nonlinear viscoelastic materials is presented. The Creep incompressilility assumption is used Tosimulate fracture behavior of craze region. it is assumed that in the .fracture processzone near the crack tip, the cohesive stress fo acts upon the crack surfaces and resistscrack opening. Through a perturbation method i. e., by superposing the Mode-Iapplied force onto a referential uniform stress state, which has a trivial solution and gives no effect on the solution of the original problem, the nonlinear viscoelasticproblem is reduced to linear problem. For weak nonlinear materials, for which thepower-law index n=1, the expressions of stress and crack surface displacement arederived. Then, the fracture process zone local energy criterion is proposed and basedon which the formulas of crucking incubation time t. and crack slow propagationvelocity a are derired.

Recalcitrant carbon controls the magnitude of soil organic matter mineralization in temperate forests of northern China

Background: The large potential of the soil organic carbon(SOC) pool to sequester CO2from the atmosphere could greatly ameliorate the effect of future climate change. However, the quantity of carbon stored in terrestrial soils largely depends upon the magnitude of SOC mineralization. SOC mineralization constitutes an important part of the carbon cycle, and is driven by many biophysical variables, such as temperature and moisture.Methods: Soil samples of a pine forest, an oak forest, and a pine and oak mixed forest were incubated for 387 days under conditions with six temperature settings(5 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C) and three levels of soil moisture content(SMC, 30%, 60%, 90%). The instantaneous rate of mineralized SOC was periodically and automatically measured using a Li-Cor CO2analyzer. Based on the measured amount of mineralized SOC,carbon fractions were estimated separately via first-order kinetic one-and two-compartment models.Results: During the 387 day incubation experiment, accumulative mineralized carbon ranged from 22.89 mg carbon(C) ·g-1SOC at 30 °C and 30% SMC for the mixed forest to 109.20 mg C·g-1SOC at 15 °C and 90% SMC for the oak forest. Mineralized recalcitrant carbon varied from 18.48 mg C·g-1SOC at 30 °C and 30% SMC for the mixed forest to 104.98 mg C·g-1SOC at 15 °C and 90% SMC for the oak forest, and contributed at least 80% to total mineralized carbon.Conclusions: Based on the results of this experiment, the soil organic matter of the pure broadleaved forest is more vulnerable to soil microbial degradation in northern China; most of the amount of the mineralized SOC derived from the recalcitrant carbon pool. Labile carbon fraction constitutes on average 0.4% of SOC across the three forest types and was rapidly digested by soil microbes in the early incubation stage. SOC mineralization markedly increased with soil moisture content, and correlated parabolically to temperature with the highest value at 15 °C. No significant interaction was detected among these variables in the present study.

Modeling of Austenite Decomposition in Low Si-Mn TRIP Steel During Cooling

Transformation behavior in low carbon Si Mn TRIP steel was investigated by means of microstructural ob servation and computer modelling. A transformation model in which transformation is controlled by carbon diffusion was suggested, which well described the volume fractional change of ferrite, pearlite, and bainite during continuous cooling. The influence of Si content and austenite grain size was thoroughly investigated. The calculated results indicated that Si retards pearlite transformation, accelerates polygonal ferrite transformation, refines the austenite grain, and increases the ferrite transformation rate.

Effects of sugarcane residue biochar and P fertilizer on P availability and its fractions in a calcareous clay loam soil

Biochar has the potential to affect the cycle of phosphorus(P),but the underlying mechanisms of its effects remain poorly understood in calcareous soils.Our understanding of the effects of biochar is limited in calcareous soils during incubation.Therefore,this study was conducted to investigate how the availability and mineral fractions of P change after the addition of combined biochar and P fertilizer during incubation in calcareous soil.Sugarcane residue(raw SR)and biochar(400℃for 2 h)were added to soils treated with 50 mg kg−1 of P,in the form of Ca(H_(2)PO_(4))_(2)·H_(2)O,at 0.5 and 1%(w/w).The soils were incubated at 25±1℃for 120 days.Available P(Olsen P)contents and mineral P fractions were measured after various incubation times(7,30,90,and 120 days).Biochar addition remarkably increased the amount of available P when compared with the raw SR treatment and the control condition(P<0.05).After 30 days of incubation,the amount of available P in the soils decreased and remained unchanged thereafter.The results indicated that the addition of 50 mg kg−1 of P as fertilizer significantly augmented the labile P and P associated with Fe and Al in all the treatments at all incubation times(P<0.05).In comparison with P treated with raw SR,P associated with Fe and Al was significantly enhanced after biochar addition(P<0.05).Significant correlations were found for available P with labile P and P associated with Fe and Al.We found that biochar addition could increase available pools,thus improving available P concentrations at various incubation times.Therefore,we conclude that sugarcane residue biochar can enhance the available P in calcareous soils.

Relationship between Hydrogen Diffusion and Blistering Nucleation and Growth

The formation condition of hydrogen blister in 18Ni maraging steel without any inner or external stress was investigated. The results show that the critical diffusible hydrogen concentration of a blister forming is about 1.4×10^-5 , which is corresponding to the current density of 30 mA/cm^2 during cathodic charging in a sodium hydroxide solution. For a 0.1 cm thick sample, no matter the current density is equal to or much larger than the critical value, it spends at least about 132 h to form a hydrogen blister when hydrogen charging in single direction. It is approxi- mately equal to the time for hydrogen atom to diffuse throughout the sample, which exactly depends on the hydrogen diffusion coefficient and the penetration depth. The very first clear suggestion was reported that the incubation period for hydrogen blister nucleation was necessary. According to the Fick＇s laws, calculations show that the normalized hydrogen concentration in the escaping surface almost reaches 0.96 times of the charging surface, which means that the diffusion almost reaches a dynamic balance. A model was illustrated to describe the competitive relationship between hydrogen diffusion and blister formation.