Isothermal Tests Research Articles

Characteristics of common pathogens of urogenital tract among outpatients in Shanghai, China from 2016 to 2021.

Ureaplasma urealyticum, Chlamydia trachomatis, and Neisseria gonorrhoeae are the prevalent causes of several genital diseases worldwide; however, their characteristics in different genders have not been well documented in Shanghai. The aim of this study is to describe the prevalence of common pathogens among outpatients, considering variations by gender and age. From January 1, 2016, to December 31, 2021, the urogenital swabs of 16216 outpatients aged 3-95 years from two general hospitals in Shanghai were collected. All participants' swabs were investigated for U. urealyticum, C. trachomatis, and N. gonorrhoeae by isothermal RNA-based simultaneous amplification and testing. The basic information of all participants was also recorded, including age and gender. The chi-square test was used to compare the prevalence between different genders, age groups, and infection patterns. There were 5,744 patients (35.42%) with positive samples whose ages ranged from 7 to 80 years (33.23 ± 8.63 years), and 62.14% of them were women. The most common pathogen detected was U. urealyticum (85.08%). The highest prevalence rate of all three pathogens was found in patients aged ≤ 20 years (40.53%, 95% confidence intervals [CI]: 33.80%-47.63%). The prevalent rate of U. urealyticum was higher in men (33.36%, 95% CI: 32.19%-34.55%). The overall prevalence rates of U. urealyticum, C. trachomatis, and N. gonorrhoeae were 30.14% (95% CI: 29.44%-30.85%), 6.00% (95% CI: 5.64%-6.38%), and 2.10% (95% CI: 1.89%-2.33%). Ureaplasma urealyticum was the most prevalent pathogen in the population, and its prevalence decreased with age. Young men aged ≤ 20 years were more frequently infected. Regular screening for sexually transmitted pathogens in different genders and age groups are warranted, particularly in young men.

Kinetic Analysis of the Reaction between Tannic Acid (TA) and L-Lysine Diisocyanate (LDI) Systems

The kinetics of the synthesis of green polyurethane from the reaction between tannic acid (TA) and L-lysine diisocyanate (LDI) were investigated using the differential scanning calorimeter (DSC) technique and dynamic rheological tests. The evaluation of the reaction behavior of the prepared samples was carried out using nonisothermal conditions at dynamic heating rates of 5, 10, 15, and 20°C/min. The evolution of the activation energy with conversion was computed through the five isoconversional methods of Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose (KAS), the Ozawa-Flynn-Wall method (OFW), Friedman (FR), Starink, and Vyazovkin. The average activation energy calculated from these methods was estimated at 46.5, 46.8, 47.2, 47.3, and 51.4 KJ/mol, respectively. The preexponential factor was evaluated at 5.04 × 10 5 1/s. The overall reaction order ( n + m ) was also found to be around 1.8912. The results of the combination of the model-free method and model-fitting approach exhibited that the reaction mechanism was an autocatalytic type, implying the autocatalytic effect of the urethane groups formed during the reaction. The obtained kinetic for TA/LDI was verified through its good agreement with the experimental data. Moreover, the results found from the isothermal rheological test show that with increasing temperature, the gelation time decreases.

Isothermal oxidation of additively manufactured and cast 4822 TiAl alloys at 760, 815 and 871 °C

The goal of this study was to compare the oxidation behavior of two additively manufactured 48–2–2 TiAl alloys (with banded and not banded microstructures) with a conventionally cast one at 760, 815 and 871 °C. The study focused on the transition from the incubation stage of oxidation to the break-away oxidation that was observed during isothermal oxidation tests. Detailed high resolution STEM investigations were performed to characterize the microstructure, chemistry and phase composition of the oxidation products formed at various stages of oxidation at 760 °C.

Microstructure evolution and Zener-Hollomon parameter analysis as-extruded 7005 aluminum alloy during hot deformation

Isothermal compression tests were carried out on as-extruded 7005 aluminum alloy at a temperature range of 300–550 ℃, a strain rate ranging from 0.001 to 1 s−1, and a strain of 1.2. QFormUK was used to simulate the strain distribution during the high-temperature compression and investigating the microstructure evolution, it was found that the strain near the anvil was approximately 0.7, indicating a hard-to-deform area, the strain in the central region of the specimen reached 1.4, indicating a uniform deformation zone, and the strain near the side of the specimen was approximately 1.0, indicating a zone with free deformation. When the processing temperature ranged from 400 to 450 ℃, the main softening mechanism of the alloy was dynamic recovery (DRV), dynamic recrystallization (DRX) became the primary deformation mechanism at 500 ℃. It is worth noting that research into the relationship between lnZ value and microstructure evolution has shown that the grain structure with an lnZ value of 36.6 is mainly dynamic recovery. As the lnZ value decreases, the high-temperature softening mechanism of the alloy shifts from dynamic recovery to DRX. The lower the lnZ value, the more likely DRX is to occur. Furthermore, the lnZ parameter was introduced into a simulation software to analyze the microstructure and it was found to serve as an equivalent parameter for investigating microstructures in uniform deformation zones.

Recrystallization behavior of an Al-Zn-Mg-Cu alloy during hot deformation and subsequent heat treatment

The presence of excessive residual recrystallization structure in the aero-structural part of the Al-Zn-Mg-Cu alloy negatively affects its strength and stress corrosion resistance. To achieve higher service performance, it is significant to reveal the recrystallization behavior of the Al-Zn-Mg-Cu alloy during hot working and subsequent heat treatment. In this work, the isothermal compression tests of an Al-Zn-Mg-Cu alloy were performed at the temperature range 300–450 °C and strain rate range 0.01–10 s−1. The subsequent heat treatment of the deformed specimens was conducted. The microstructure was characterized by EBSD and XRD techniques. The natural logarithm of Zener-Hollomon parameter (lnZ) was introduced, which increases with the increasing strain rate and decreasing temperature. During hot deformation, CDRX was identified to be the predominant DRX mechanism at high lnZ values, the corresponding recrystallization volume fraction was approximately 15 %. However, at low lnZ values, DDRX becomes the dominant mechanism, the corresponding recrystallization volume fraction was only around 5 %. Moreover, a kinetics analysis was conducted using a low proportion DRX model coupled with lnZ. By comparing the results obtained from finite element simulations with experimental findings, this model was proved to accurately predict the volume fraction of DRX during hot deformation. During the heat treatment process, due to the substantial storage of deformation energy, a significant portion (up to 84.5 %) of SRX was observed under high lnZ conditions. As the lnZ value decreases, the SRX weakens. This weakening is significant enough that under high temperature and low strain rate, the occurrence of SRX becomes extremely unlikely, which can be attributed to the low storage of deformation energy.

Enhancing biochar structure and removal efficiency of ammonium and microalgae in wastewater treatment through combined biological and thermal treatments

This study explored the efficiency of biological pre-treatment combined with thermal treatment to produce biochars, called E-biochars, for the removal of ammonium and microalgae without using chemical pre-treatment. The aim was to develop an environmentally sustainable approach for large-scale biochar production with high efficiency in wastewater treatment. The biological pre-treatment involved incubating the sawdust with Bacillus subtilis for 14 to 20 days and then subjected to pre-treatment at low temperatures (250-350 °C). This process broke down cellulose and altered its lignocellulosic structure, improving the biochar's morphology by leading to a more anisotropic pore structure. The thermal pre-treatment after that will help to open a broader range of pore sizes, spanning from macropores to micro-pores in the 1 μm to 5 μm dimension range. These alterations facilitated the efficient removal of ammonium and microalgae during adsorption experiments. The findings fit the Langmuir and the Freundlich models, according to the isotherm test of NH4+ and microalgae (R2 = 0.92÷0.99). The E-biochar termed EBH20, composted with Bacillus subtilis for 20 days at 350 °C, performed best, with Qmax equal to 40.2 mg/ g NH4+ under neutral conditions (pH = 7). Interestingly, the co-occurrence of ammonium and microalgae enhanced the removal of these contaminants. The interaction between microalgae cells and ammonium facilitated ammonium adsorption onto biochar and microalgae. The column breakthrough curves under NH4+ and NH4+ mixed microalgae adsorption were predicted using the Thomas model with the high agreement (R2 = 0.91÷0.99) for ammonium but for algae between prediction and running experimental column data.

Hot deformation characteristics and microstructural evolution of Ti-900 alloy

Hot deformation behaviour of Ti-900 (Ti-6.5Al-3.2Mo-1.8Zr-0.25Si) alloy has been analyzed by conducting an isothermal hot compression test at 850 °C to 1050 °C temperatures and strain rates between 0.001 s−1 to 10 s−1. The effect of strain rates and deformation temperature on flow stress is investigated. The processing maps are constructed, and constitutive equations are studied to understand the formability of the novel titanium alloy in the different temperatures and strain rates regimes. Results suggest that temperatures and strain rates between 880 °C to 950 °C and 0.001 s−1 to 0.01 s−1 are the optimal processing window for this alloy. The kinetic rate equation indicates that the apparent activation energy for deformation is 531 kJ/mol in the α + β region. Post deformation microstructure formation is also studied.

Effect of non-isothermal adsorption model on gas diffusion in coal particle

Gas diffusion is of great importance for coalbed methane (CBM) recovery and CO2 storage in coal seam. Most of the existing models of gas diffusion in coal particles are derived under isothermal conditions, while the coupled effect between gas adsorption/desorption and temperature variation is often neglected. The effect of accurate non-isothermal adsorption model on gas diffusion simulation also needs further study. In this work, isothermal adsorption tests of CO2 in anthracite/bitumite particles at different temperatures are conducted. The fitting results of Langmuir/Freundlich adsorption models are analyzed and the optimal non-isothermal adsorption models for anthracite/bitumite are obtained respectively. Non-isothermal desorption-diffusion tests of CO2 in anthracite/bitumite particles are carried out and corresponding non-isothermal desorption-diffusion model is also proposed, based on which the effect of non-isothermal adsorption model on gas diffusion in coal is numerically analyzed comprehensively. The results show that the non-isothermal Langmuir/Freundlich adsorption models are optimal for anthracite/bitumite respectively. Based on the optimal adsorption models, simulated gas diffusion amounts agree well with the experimental results and consistent diffusion coefficients can be back calculated. For sub-optimal adsorption model with R2 > 0.9, its deviation from adsorption data would significantly affect the accuracy of gas desorption-diffusion simulation. Moreover, if ‘diffusion ratio’ is taken as evaluation index, the inaccurate diffusion amount caused by inaccurate adsorption model in numerical simulation may be ignored, and the diffusion coefficient determined by ‘diffusion ratio’ would deviate from the true value.

The Preparation and Properties of Ni2Al3 Intermetallic Compound Coating

In this work, a Ni2Al3 intermetallic compound coating was prepared on 45 # steel by combining methods of low-pressure cold spray and heat treatment. Firstly, powders mixed with Ni powders, Al powders, and Al2O3 powders as a mass ratio of 20:6:4 were sprayed on surface of 45 # steel by low-pressure cold spraying technology to prepare a Ni-Al pre-coating. Subsequently, the pre-coating was annealed at 570 °C in an argon atmosphere for 12 h to obtain the Ni2Al3 intermetallic compound coating. The composite coating was characterized using TEM, SEM, and XRD. High temperature oxidation performance of the composite coating was analyzed by isothermal oxidation tests conducted at 600 °C in air atmosphere for 96 h. The results show that the composite coating is composed of Ni2Al3 phase. Under a high-temperature oxidation environment, a protective oxide film composed by Al2O3 and NiO was formed on the coating surface, which resulting in a superior high-temperature oxidation resistance compared to 15CrMo heat-resistant steel. The mechanism of the Ni2Al3 coating resistance to high-temperature oxidation is that an oxide film mainly composed of Al2O3 and NiO formed on the surface during the high-temperature oxidation process; this oxide film can effectively resist oxidation and protect the substrate material from oxidation at a high temperature of 600 °C.

Dynamic recrystallization behavior of a newly developed Ni-Fe based superalloy during hot deformation

The dynamic recrystallization (DRX) behavior of a newly developed Ni-Fe based superalloy was investigated by isothermal compression tests performed at a wide temperature range of 950 to 1200 °C with a strain rate range from 0.01 to 10 s−1 under a true strain of 0.916. The electron backscatter diffraction (EBSD) technique was employed to investigate the effect of strain rate and temperature on the microstructure evolution. The results revealed that the size and volume fraction of DRX grains increased with increasing the temperature. The volume fraction of DRX grains first decreased and then increased with increasing the strain rate during the hot deformation. The preferred orientation of the overall grains changed from <001>//CD to <110>//CD with increasing the strain rate during the deformation at 950 °C, while the preferred orientation of overall grains consistently maintained as <001>//CD during the deformation at 1200 °C. DDRX was the dominant mechanism during the deformation, while CDRX was proved to be an assistant mechanism and was promoted with increasing the strain rate.

Modeling the hot deformation behavior of micro-alloyed steel in the single and two-phase fields

Continuous casting is a well-established process to produce steel slabs. However, the surfaces of the slabs may crack during processing. The occurrence of cracks is related to different phenomena, i.e., ferrite formation, presence of precipitates, and microstructural modifications during manufacturing processing. In the present work, we developed a physically based mesoscale model to describe the plastic deformation of micro-alloyed steel in the single and two-phase fields, as well as the microstructure evolution. We implemented a dislocation density-based constitutive model to calculate the strain hardening and the stress softening produced by dynamic recovery using the Kocks-Mecking (KM) formalism for the austenite and ferrite. We coupled the KM model with the Johnson-Mehl-Avrami-Kolmogorov model to consider the dynamic recrystallization of the austenitic phase. The nucleation and growth of the recrystallized grains, driven by the stored energy, compete with the annihilation of dislocations due to dynamic recovery. In the two-phase domain, the iso-work condition for the load partition is implemented. We calculated the ferrite volume fraction by fitting the data obtained using JmatPro software. Moreover, an Arrhenius-type equation correlates the yield stress to the Zener-Hollomon parameter. We validated the model with isothermal uniaxial compression tests of microalloyed steel over the temperature range of 650 °C-1100 °C and strain rates of 10−2 s−1 and 10−3 s−1 using a Gleeble® 3800 thermomechanical simulator.

Intragranular ferrite nucleation on MX carbonitrides and dislocations

The competing mechanisms of ferrite nucleation on (Ti,V)(C,N) MX carbonitrides and dislocations, as well as their dependence on deformation, are investigated experimentally by thermo-mechanical treatments and via simulation. The impact of recrystallization and the resulting austenite grain size on intragranular ferrite nucleation is evaluated. The austenite-to-ferrite transformation temperatures, affected by different microstructures, are examined by isothermal uniaxial single-hit compression tests on a dilatometer DIL 805 and compared to thermal treatments without deformation. Different resulting microstructures are analyzed by using optical light microscopy. The experimental data is used for the validation of thermo-kinetic simulations with the mean-field modeling software MatCalc using the implemented models for the austenite grain evolution, the on-particle nucleation of ferrite on the surface of MX particles, the dislocation density evolution, and recrystallization.

Sustainable concrete made with wastewater from different stages of filtration

Reusing natural resources in concrete to create sustainable and environmentally friendly structures becomes more important as the demand for concrete increases annually and as the population grows. Among available resources, wastewater can be an alternative, although its use in concrete needs to be fully explored. In this feasibility study, the micro and macrostructural characteristics of concrete made with wastewater at three different levels of filtration were investigated and the results were compared to the control batch made with potable water. A series of compression tests at six different ages of 1, 7, 14, 28, 56, and 90 days along with water absorption tests, isothermal calorimetry tests, and SEM/EDS tests were performed in this research. The relations between compressive strength and age were determined for different specimens. Results showed that the change in the compressive strength of specimens made with wastewater compared with the control batch was less than 7 % on average. It was shown that the lowest and the highest values of water absorption were for the least and most considered filtration levels of the wastewater. The isothermal calorimetry tests revealed a difference of about 4 % at the heat flow’s main exothermic peak between the specimens. Furthermore, isothermal calorimetry and water absorption tests showed a correlation between hydration and water absorption. The SEM tests showed that the specimens made with the least filtration level of wastewater had a denser structure with fewer pores. Results of the compression tests, water absorption experiments and microstructural properties are shown to be consistent with the SEM findings. In general, this study demonstrates that wastewater can be a sustainable alternative to potable water for concrete construction. No significant differences were observed between the test results of specimens made with wastewater and those made with potable water.

Efficient Adsorption of Ammonia by Surface-Modified Activated Carbon Fiber Mesh.

In view of the characteristics and risks of ammonia, its removal is important for industrial production and environmental safety. In this study, viscose-based activated carbon fiber (ACF) was used as a substrate and chemically modified by nitric acid impregnation to enhance the adsorption capacity of the adsorbent for ammonia. A series of modified ACF-based adsorbents were prepared and characterized using BET, FTIR, XPS, and Boehm titration. Isotherm tests (293.15 K, 303.15 K, 313.15 K) and dynamic adsorption experiments were performed. The characterization results showed that impregnation with low concentrations of nitric acid not only increased the surface acidic functional group content but also increased the specific surface area, while impregnation with high concentrations of nitric acid could be able to decrease the specific surface area. ACF-N-6 significantly increased the surface functional group content without destroying the physical structure of the activated carbon fibers. The experimental results showed that the highest adsorption of ammonia by ACFs was 14.08 mmol-L-1 (ACF-N-6) at 293 K, and the adsorption capacity was increased by 165% compared with that of ACF-raw; by fitting the adsorption isotherm and calculating the equivalent heat of adsorption and thermodynamic parameters using the Langmuir-Freundlich model, the adsorption process could be found to exist simultaneously. Regarding physical adsorption and chemical adsorption, the results of the correlation analysis showed that the ammonia adsorption performance was strongly correlated with the carboxyl group content and positively correlated with the relative humidity (RH) of the inlet gas. This study contributes to the development of an efficient ammonia adsorption system with important applications in industrial production and environmental safety.

MMT and ZrO2 jointly regulate the pore size of graphene oxide-based composite aerogel materials to improve the selective removal ability of Cu(II)

In this study, based on the cross-linking effect of Ca(II) and Sodium Alginate (SA), the basic skeleton was established with the accumulation of nanosheets of Graphene oxide (GO) and Montmorillonite (MMT), and the Zirconia (ZrO2) nanoparticles were further loaded on it to successfully prepare GMZ. Selective removal of hydrated copper ions from complex wastewater systems was achieved by increasing the cross-linking density within the aerogel spheres as well as by providing binding sites for metal ions to functionalize the aerogel into a controlled slit pore structure. The system adsorption experiments showed that Cu(II) was selectively eliminated by GMZ, with a maximum removal rate of 97.35% and a distribution coefficient of 26.33 L g−1. Adsorption kinetics and isothermal adsorption tests demonstrated that it was a multi-molecular layer chemical adsorption process (155.712 mg g−1), which was stronger than the previous similar adsorption materials. SEM morphology analysis confirmed that the aerogel was endowed with controllable slit pores. FT-IR and XPS verified the synergistic effects of ion exchange, high electrostatic force, and complexation, which contributed to the remarkable adsorption performance of GMZ. In case of adsorbing Cu(II) on GO, the roles of MMT, ZrO2, and SA were also confirmed using Density Functional Theory (DFT). In summary, GMZ had infinitely feasibility that Cu(II) was selectively removed from complicated wastewater systems.

Matching design of thickness ratio to extend the lifespan of double-layered thermal-barrier coatings

The ceramic materials of advanced thermal-barrier coatings (TBCs) must be exposed to high temperatures (over 1200°C) over a long lifespan. To meet this requirement, researchers have recently developed phase-stable ceramic materials. However, most of the newly developed materials have low fracture toughness and are easily cracked. Double-layered TBCs (DL–TBCs) can potentially provide a fast route to engineering applications of ceramic materials. The present paper attempts to extend the lifespan of DL–TBCs by matching the thickness ratio of the top layer to the bottom layer. First, the lifespans of different DL–TBCs with equivalent thermal insulation were determined in an iso-thermal cyclic test. The lifespan increased and then decreased with increasing thickness ratio. The optimized matching design of the thickness ratio (approximately 2:3) more than doubled the lifespan. Subsequently, the failure mechanism of DL–TBCs with different thickness ratios was analyzed through simulations. Varying the thickness ratio changed the lifespan by influencing the cracking driving force. Finally, to optimize the double-layer structures, the structural evolution was characterized under thermal exposure. Sintering-induced stiffening largely increased the cracking driving force, posing a main failure threat. The simulation suggested that lowering the stiffening degree in the top layer can further extend the TBC lifespan.

Analysis of the cyclic strength of technical systems in conditions of complex operation loading

The main cyclic thermomechanical loads, as well as changeable in time vibration and aerohydrodynamic loadings accompanying them affect modern energy facilities, space, air, water and ground transport. At the same time the total number of loading cycles taking into account the duration of service turns out to be within in very wide limits. It is shown that a general spectrum of loads changing in time which affect the aforementioned objects is very complicated in terms of load levels, frequency ratios and time of their action. Taking into account a large variation of service impacts in the loading levels, frequency ratio and total number of loading cycles we performed a generalized analysis of the resistance to deformation, damage and fracture of high-loaded objects of modern technics. The results obtained revealed that in conditions of combined mechanical, vibration and aero-, gidro-, acoustic loadings the limit state (by criteria of cyclic strength using the rule of linear summation of damages expressed in deformation parameters) will be attained earlier, than that obtained only with allowance of the main thermomechanical loading. To substantiate the strength and service life of the objects under consideration, traditional standard and unified mechanical isothermal tests for static and cyclic loading are carried out to determine the basic characteristics of the mechanical properties of the material, as well as special mechanical programmed tests with variable modes that simulate complex processes of operational thermomechanical, vibration and aerohydrodynamic impacts. The results of testing are taken into account in computation and experimental estimations of the strength and the fatigue life for the corresponding spectra of operational loads. A refined verification calculation of the cyclic strength and durability is becoming increasingly relevant for modern machines and units operating under conditions of increasing speeds of movement, operating pressures with increased levels of pulsations, as well as in the occurrence of accompanying mechanical oscillations, vibrations and aerohydroacoustic impacts.

Simulation of the effect of nano-CaCO3 agglomeration on the hydration process and microstructural evolution of cement paste

In this study, three-dimensional simulations of cement hydration are conducted to investigate the effect of nano-CaCO3 (NC) agglomeration on the hydration process and microstructural evolution of cement pastes (CPs). Few experimental studies have reported on the effect of NC agglomeration on the properties of CPs because the degree of NC agglomeration is difficult to control in experiments. Herein, NC agglomeration was first investigated in a simulation by assigning different contents of NC in water-filled voxels in a three-dimensional cement hydration and microstructure development model (CEMHYD3D). CPs containing 3 wt% NC with a water-to-cement ratio (w/c) of 0.3 were considered in the simulation. Four levels (1, 2, 3, and 4) of NC agglomeration were investigated by assigning 8.5, 13.7, 19.8, and 27 vol% of NC in a C–H voxel, respectively. Agglomeration level 0 refers to the condition in which no NC particles are deposited in a water-filled voxel. An isothermal calorimetry test was conducted to validate the simulation results obtained for plain CPs. A comparison of experimental data and simulation results in terms of heat flow rate and heat formation revealed that level 3 showed better agreement than the other levels. The effect of NC agglomeration on cement hydration was more evident in the early stages of the process than in the later stages. Lower levels of agglomeration resulted in a faster hydration rate, a higher degree of hydration (DOH), and higher C–S–H and CH contents at an early age. However, the addition of NC particles did not result in an increase in ultimate DOH.

Differential scanning calorimetry as a tool to assess the oxidation state of cold-pressed oils during shelf-life

AbstractCold-pressed oils are highly prone to the peroxidation process, which causes a rapid decline in quality. Thus, there is a need to develop instrumental methods instead of conventional chemical analysis consuming large quantities of harmful chemicals. Differential scanning calorimetry (DSC) is a valuable analytical tool for assessing the oxidative stability of oils. Cold-pressed flaxseed, camelina and hemp seed oils from different cultivars, which had been stored for six months in room conditions under natural light exposure, were tested. Chemical methods for measuring changes in oxidative stability during storage of oils included determination of peroxide value (PV), p-Anisidine value (p-AV), total oxidation value (TOTOX) value and acid value (AV). Parameters like oxidation induction time (OIT) in isothermal mode (120, 140 °C) and onset temperature (Ton) in non-isothermal mode (heating rate 2, 5 °C/min) were established from DSC curves. Data for OIT and Ton plotted against time showed a strong, significant (p ≤ 0.05) descending trend for all oils. However, flaxseed and hempseed oils revealed a more rapid deterioration during storage compared to camelina seed oils. All DSC results showed promising repeatability of the oxidative characteristics for three types of cold-pressed oils, regardless of their origins in different cultivars. However, the most suitable for monitoring the deteriorative changes in oils during storage was the isothermal test carried out at a temperature of 120 °C, for which the correlations with chemical indicators (PV, p-AV, TOTOX) were highly significant (p ≤ 0.0001). Linear discriminant analysis (LDA) based on the DSC results revealed, that the first discriminating function significantly separated the fresh oils from stored oils. The study showed that, based on a starting point defined for fresh oils, the DSC technique can be used to effectively and ecologically monitor the deterioration of oils by oxidation, instead of harmful chemical analyses.

Hot workability optimization of W400 non-oriented silicon steel

Isothermal compression tests of W400 non-oriented silicon steel are performed at 0.01 to 10 s−1 and 850 to 1150 °C on a Gleeble thermo-mechanical simulator. Each stress-strain curve shows monotonous but slow increase of flow stress blessed with increasing strain. By introducing temperature into the strain rate exponent in Z parameter and proposing the temperature boundary principle, a revised constitutive pattern is built with a view to quantify flow stress versus temperature and strain rate accurately. Numerous sub-grains and sub-grain boundaries (GBs) are detected in the deformed grains, confirming the distortion energy to be reduced by dynamic recovery and thus slowing down the monotonous increase of flow stresses. Unusual discontinuous dynamic recrystallization is activated when strain rate and temperature is relatively higher, as confirmed by the random orientations of recrystallized grains. Analyses of GB shape and intergranular misorientation prove that local strain due to weak dynamic recovery leads to GB bulging and sub-GB formation, and thus activates the unusual discontinuous dynamic recrystallization. The distribution maps of strain rate sensitivity coefficient are constructed when the strain are 0.2–0.8. Based on high strain rate sensitivity coefficient, low deformation resistance and high GB stability, workability parameters are optimized as: temperature 1000–1150 °C, strain rate 0.01 to 10−0.5 s−1 and strain ≤0.6.