Modeling time-dependent mechanical behavior of hard rock considering excavation-induced damage and complex 3D stress states

To investigate the long-term stability of deep rocks,a three-dimensional(3D)time-dependent model that accounts for excavation-induced damage and complex stress state is developed.This model comprises three main components:a 3D viscoplastic isotropic constitutive relation that considers excavation damage and complex stress state,a quantitative relationship between critical irreversible deformation and complex stress state,and evolution characteristics of strength parameters.The proposed model is implemented in a self-developed numerical code,i.e.CASRock.The reliability of the model is validated through experiments.It is indicated that the time-dependent fracturing potential index(xTFPI)at a given time during the attenuation creep stage shows a negative correlation with the extent of excavationinduced damage.The time-dependent fracturing process of rock demonstrates a distinct interval effect of the intermediate principal stress,thereby highlighting the 3D stress-dependent characteristic of the model.Finally,the influence of excavation-induced damage and intermediate principal stress on the time-dependent fracturing characteristics of the surrounding rocks around the tunnel is discussed.

International study of the Complex Stress Reaction Syndrome:Implications for transdiagnostic clinical practice

BACKGROUND The debate regarding diagnostic classification systems in psychiatry(categorial vs dimensional systems)has essential implications for the diagnosis,prevention and treatment of stress reactions.We previously found a unique pattern of stress reaction in a study executed during the coronavirus disease 2019 pandemic using large representative samples in two countries,and termed it the Complex Stress Reaction Syndrome(CSRS).AIM To investigate CSRS,Type A(psychiatric symptoms,spanning anxiety,depression,stress symptoms,and posttraumatic stress disorder(PTSD)),with or without long-coronavirus disease(COVID)residuals(CSRS,Type B,neuropsychiatric symptoms spanning cognitive deficits and fatigue,excluding systemic symptoms).Our two-tailed hypothesis was that CSRS is a condition related to an unrecognized type of stress reaction in daily life in the general population(Type A)or that it is related to the severe acute respiratory syndrome coronavirus 2 infection and its long-COVID residuals(Type B).METHODS 977 individuals in four continents(North America,Europe,Australia and the Middle East)completed the online study questionnaire in six languages using the Qualtrics platform.The study was managed by six teams in six countries that promoted the study on social media.The questionnaire assessed anxiety,depression,stress symptoms and PTSD(CSRS,Type A),cognitive deficits and fatigue(CSRS,Type B).The data were analyzed using Proportion Analyses,Multivariate Analysis of Co-Variance(MANCOVA),linear regression analyses and validated clinical cutoff points.RESULTS The results of the Proportion Analyses showed that the prevalence of 4 symptoms spanning anxiety,depression,stress symptoms,and PTSD was significantly higher than the most prevalent combinations of fewer symptoms across 4 continents,age groups,and gender.This supports the transdiagnostic argument embedded in the CSRS(Type A).The same pattern of results was found in infected/recovered individuals.The prevalence of the 4 psychiatric symptoms combination was significantly greater than that of 5 and 6 symptoms,when adding cognitive deficits and fatigue,respectively.MANCOVA showed a significant three-way interaction(age×gender×continent).Further analyses showed that the sources of this three-way interaction were threefold relating to two sub-populations at-risk:(1)Individuals that self-identified as non-binary gender scored significantly higher on all 4 psychiatric symptoms of the CSRS,Type A at young age groups(<50 years old)in North America compared to(self-identified)women and men located in the 4 continents studied,and to other ages across the adult life span;and(2)This pattern of results(CSRS,Type A)was found also in women at young ages(<40 years old)in North America who scored higher compared to men and women in other continents and other ages.Linear regression analyses confirmed the MANCOVA results.CONCLUSION These results show a combined mental health risk factor related to stress reactivity,suggesting that the CSRS is sensitive to populations at risk and may be applied to future identification of other vulnerable sub-populations.It also supports the transdiagnostic approach for more accurate prevention and treatment.Time will tell if such transdiagnostic syndromes will be part of the discussions on the next revisions of the traditional classification systems or whether the crisis in psychiatry further evolves.

Analytical investigations of in situ stress inversion from borehole breakout geometries

This study aims to investigate the feasibility of deriving in situ horizontal stresses from the breakout width and depth using the analytical method.Twenty-three breakout data with different borehole sizes were collected and three failure criteria were studied.Based on the Kirsch equations,relatively accurate major horizontal stress(sH)estimations from known minor horizontal stress(sh)were achieved with percentage errors ranging from 0.33%to 44.08%using the breakout width.The Mogi-Coulomb failure criterion(average error:13.1%)outperformed modified Wiebols-Cook(average error:19.09%)and modified Lade(average error:18.09%)failure criteria.However,none of the tested constitutive models could yield reasonable sh predictions from known sH using the same approach due to the analytical expression of the redistributed stress and the nature of the constitutive models.In consideration of this issue,the horizontal stress ratio(sH/sh)is suggested as an alternative input,which could estimate both sH and sh with the same level of accuracy.Moreover,the estimation accuracies for both large-scale and laboratory-scale breakouts are comparable,suggesting the applicability of this approach across different breakout sizes.For breakout depth,conformal mapping and complex variable method were used to calculate the stress concentration around the breakout tip,allowing the expression of redistributed stresses using binomials composed of sH and sh.Nevertheless,analysis of the breakout depth stabilisation mechanism indicates that additional parameters are required to utilise normalised breakout depth for stress estimation compared to breakout width.These parameters are challenging to obtain,especially under field conditions,meaning utilising normalised breakout depth analytically in practical applications faces significant challenges and remains infeasible at this stage.Nonetheless,the normalised breakout depth should still be considered a critical input for any empirical and statistical stress estimation method given its significant correlation with horizontal stresses.The outcome of this paper is expected to contribute valuable insights into the breakout stabilisation mechanisms and estimation of in situ stress magnitudes based on borehole breakout geometries.

Stiffness Degradation of Undisturbed Saturated Soft Clay in the Yangtze Estuary Under Complex Stress Conditions

Stiffness degradation will occur due to the generation of accumulated pore pressure in saturated soft clays under cyclic loading. The soil static-dynamic multi-purpose triaxial and torsional shear apparatus in Dalian University of Technology was employed to perform different types of test on the saturated soft marine clay in the Yangtze Estuary. Undisturbed samples of the clay were subjected to undrained cyclic vertical and torsional coupling shear and cyclic torsional shear after three-directional anisotropic consolidation with different initial consolidation parameters. Investigated were the effects of the initial orientation angle of the major principal stress, initial ratio of deviatoric stress, initial coefficient of intermediate principal stress and continuous rotation of principal stress axes on the stiffness degradation. It is found that the degradation index decreases （or degradation degree increases） significantly with increasing initial orientation angle of the major principal stress and initial ratio of deviatoric stress. Compared with the effects of the initial orientation angle of the major principal stress and initial ratio of deviatoric stress, the effect of initial coefficient of intermediate principal stress is less evident and this trend is more clearly reflected by the results of the cyclic torsional shear tests than those of the cyclic coupling shear tests. At the same cycle number, the degradation index obtained from the cyclic torsional shear test is higher than that from the cyclic coupling shear test. The main reason is that the continuous rotation in principal stress directions during cyclic coupling shear damages the original structure of the soil more than the cyclic torsional shear does.Based on a series of experiments, a mathematical model for stiffness degradation is proposed and the relevant parameters are determined.

Effects of salt-alkali stress on active oxygen metabolism in roots of Spiraea × bumalda 'Gold Mound' and Spiraea × bumalda 'Gold Flame'

Under artificially-simulated complex salt-alkali stress, the levels of active oxygen metabolism in roots were studied using three-year-old cutting seedlings of Spiraea × bumalda ‘Gold Mound＇ and Spiraea × bumalda ‘Gold Flame＇. The present study aimed at exploring the antioxidant capacity in roots of spiraeas and revealing their adaptability to salt-alkali stress. Results indicate that the oxygen free radicals contents, electrolyte leakage rates and MDA contents in roots of Spiraea × bumalda ＇Gold Mound＇ and Spiraea × bumalda ＇Gold Flame＇ show an increasing tendency with the increases of the salinity and pH value, whereas the activities of superoxide dismutase （SOD）, peroxidase （POD） and catalase （CAT） all increased firstly and then decreased. With the increase in intensity of salt-alkali stress, the CAT activity in roots of Spiraea × bumalda ‘Gold Flame＇ is higher and the increasing extents in the oxygen free radicals contents, electrolyte leakage rates as well as MDA contents are lower compared with Spiraea × bumalda ‘Gold Mound＇, indicating that Spiraea × bumalda ‘Gold Flame＇ has a stronger antioxidant capacity.

Effect of intermediate principal stress on strength of soft rock under complex stress states

A series of numerical simulations of conventional and true triaxial tests for soft rock materials using the three-dimensional finite difference code FLAC3D were presented. A hexahedral element and a strain hardening/softening constitutive model based on the unified strength theory(UST) were used to simulate both the consolidated-undrained(CU) triaxial and the consolidated-drained(CD) true triaxial tests. Based on the results of the true triaxial tests simulation, the effect of the intermediate principal stress on the strength of soft rock was investigated. Finally, an example of an axial compression test for a hard rock pillar with a soft rock interlayer was analyzed using the two-dimensional finite difference code FLAC. The CD true triaxial test simulations for diatomaceous soft rock suggest the peak and residual strengths increase by 30% when the effect of the intermediate principal stress is taken into account. The axial compression for a rock pillar indicated the peak and residual strengths increase six-fold when the soft rock interlayer approached the vertical and the effect of the intermediate principal stress is taken into account.

Complex posttraumatic stress disorder: The need to consolidate a distinct clinical syndrome or to reevaluate features of psychiatric disorders following interpersona trauma?

Complex posttraumatic stress disorder(Complex PTSD)has been recently proposed as a distinct clinical entity in the WHO International Classification of Diseases,11^(th) version, due to be published, two decades after its first initiation. It is described as an enhanced version of the current definition of PTSD, with clinical features of PTSD plus three additional clusters of symptoms namely emotional dysregulation, negative self-cognitions and interpersonal hardship, thus resembling the clinical features commonly encountered in borderline personality disorder(BPD). Complex PTSD is related to complex trauma which is defined by its threatening and entrapping context, generally interpersonal in nature. In this manuscript, we review the current findings related to traumatic events predisposing the above-mentioned disorders as well as the biological correlates surrounding them, along with their clinical features. Furthermore, we suggest that besides the present distinct clinical diagnoses(PTSD; Complex PTSD; BPD), there is a cluster of these comorbid disorders, that follow a continuum of trauma and biological severity on a spectrum of common or similar clinical features and should be treated as such. More studies are needed to confirm or reject this hypothesis, particularly in clinical terms and how they correlate to clinical entities' biological background, endorsing a shift from the phenomenologically only classification of psychiatric disorders towards a more biologically validated classification.

Analysis of the stress intensity factor of welded joints under prior corrosion and complex stress fields

Taking cruciform welded joints under different corrosion degrees, together with 45° inclined angle and full penetration load-carrying fillet, as the research object, the stress intensity factor of a quarter-circular comer crack of welded joints is calculated based on FRANC3D with ABAQUS. Effects of different corrosion pit sizes, crack aspect ratios, and crack depths on stress intensity factor are analyzed. The results show that pit depth plays a major role in stress intensity factor, while the effect of pit radius is relatively small. The cracking modes of the surface and the deepest point are mode I, and mixed modes I and II, respectively. Effects of pit depths, crack aspect ratios, and crack depths on the stress intensity factor at the surface point are greater than at the deepest point.

Local Shear Stresses Elicit Different Mechanical Response and Gene Expression from Complex Stresses

It is well established that living cells and tissues respond to mechanical forces such as flow-related shear stresses in blood or interstitial space and complex tractional stresses at cell-matrix contacts and cell-cell contacts.However,how different modes of forces impact mechanical and biological responses is elusive.Here we describe a strategy of using the three-dimensional magnetic twisting cytometry(3D MTC)technology to apply forces in any desired directions to the same living cell.We reveal that for a fixed stress amplitude and frequency,a live cell exhibits mechanical anisotropy and responds to a local shear stress differently from responding to a local complex stress by stretching chromatin and upregulating gene transcription to different levels,extending our previous finding on force-induced direct gene activation.This finding highlights the importance of force modes in impacting cellular mechanical and biological responses in living cells and tissues and may have implications in tissue patterning and embryonic development.

Effect of Complex Preparation on the Hemorheological Indexes of Heat Stress Piglets

In the study, heat stress environment was simulated by artificial climate cabin to establish the heat stress model of piglets. A total of 64 2-month-old Chinese miniature pigs used for test were sdected and randomly divided into control group, heat stress group, complex preparation extract I treatment group and complex preparation extract II treatment group. Hematocrit was analyzed by Wintrobe test, meanwhile, the hemorheological indexes such as whole blood viscosity were analyzed by the automated analysis system of hemorrheology. In order to study the dynamic changes of complex preparation on the hemorheologieal indexes of heat stress piglets. The results showed that the piglets whole blood viscosity at high shear rate on the 10~ days in heat stress group was significantly highe~ than that in control group （P 〈 0.05） ; erythrocyte deformation indexes on the 6th and 10th days in heat stress group were significantly lower than that in control group （P 〈 0.05） ; hematocfit on the 1＂, 3＇~, 6~h and 10＇h days in heat stress group was significantly higher than that in control group （P 〈 0.05）. Hemorhealogieal inde- xes of the piglets in treatment group adding with complex preparation had been significantly restored, the effect on the 10th day after the stress was the most significant （P 〈 0.05）. The test results indicated that heat stress showed some significant influences on the health of piglets. Complex preparation could reduce the physiological damage causing by heat stress, and the effect of complex preparation II was better than that of complex preparation I.

Complex Post Traumatic Stress Disorder (PTSD) in Defilement: Case Report

We report a case of the debilitating and lifelong complex post traumatic stress disorder. Data on rape/defilement-related complex post traumatic stress disorder (PTSD) is rare due to low reporting rates and misdiagnosis in Kenya. Childhood complex PTSD is compounded by its symptomatic overlap with rape trauma syndrome (RTS) and attention deficit hyperactivity disorder (ADHD). This case demonstrated the difficulties involved in making the correct diagnosis while at the same time it brought to the fore clearly the features of complex PTSD as opposed to ordinary PTSD. Strengths in management depended on making appropriate diagnosis based on concerted efforts by clinicians, comprehensive care, team work, sensitivity to age and sex, winning trust of the child and the care taker among others and bearing in mind the in-ward handling of the trauma by the rape/defilement victims. This case shared a lot with other cases of complex PTSD in its presentation, course of illness, diagnosis and response to management protocol instituted yielding positive results. Using the lessons learnt from this case, her response was satisfactory based on her improved social and occupational functioning. The patient continues to respond well to treatment to date, bearing in mind that her presentation and age within a dysfunctional family background did not offer good prognosis, especially if the management and social support system will not be steadfast and innovative.

ANALYSIS OF COMPLEX STRESS INTENSITIES FOR CRACKED LAMINATES

Classical plate theory has been used to find out interfacial stress intensity factors in composite laminates. By using a well-known relation between the crack-tip energy release rate and the complex stress intensity factor. a closed-form solution for complex. Stress intensity in terms of external loading and a mode mix parameter for fairly. general composite laminates is given. Then a procedure for determining this mode mix. parameter is presented. followed by numerical results for some laminates. Small scale contact condition is expressed in terms of external loading In particular, a symmetric property of interfacial toughness curye is proven. Finally. the accuracy of failure load predicled by elininating oscllation index is discussed. and an example is presented to show the validity and limitation of β=0 approximation.

Critical Cyclic Stress Ratio of Undisturbed Saturated Soft Clay in the Yangtze Estuary under Complex Stress Conditions

There exists a critical cyclic stress ratio when sand or clay is subjected to cyclic loading. It is an index dis-tinguishing stable state or failure state. The soil static and dynamic universal triaxial and torsional shear apparatus de-veloped by Dalian University of Technology in China was employed to perform different types of tests on saturated soft marine clay in the Yangtze estuary. Undisturbed samples were subjected to undrained cyclic vertical and torsional coupling shear and cyclic torsional shear after three-directional anisotropic consolidation with different initial consoli-dation parameters. The effects of initial orientation angle of major principal stress, initial ratio of deviatoric stress,initial coefficient of intermediate principal stress and stress mode of cyclic shear on the critical cyclic stress ratio wereinvestigated. It is found that the critical cyclic stress ratio decreases significantly with increasing initial orientation angle of major principal stress and initial ratio of deviatoric stress. Compared with the effects of the initial orientationangle of major principal stress and initial ratio of deviatoric stress, the effect of initial coefficient of intermediate prin-cipal stress is less evident. Under the same consolidation condition, the critical cyclic stress ratio from the cyclic cou-pling shear test is lower than that from the cyclic torsional shear test, indicating that the stress mode of cyclic shear has an obvious effect on the critical cyclic stress ratio. The main reason is that the continuous rotation in principal stressdirections during cyclic coupling shear damages the original structure of soil more than the cyclic torsional shear does.

Effects of complex salvia miltiorrhiza on blood coagulation, inflammation, oxidative stress and endothelial index in patients with acute pancreatitis

Objective: To investigate the effects of complex salvia miltiorrhiza on blood coagulation, inflammation, oxidative stress and endothelial index in patients with acute pancreatitis. Methods: A total of 122 patients with acute pancreatitis admitted to digestive system department in our hospital from April 2016 to November 2017 were randomly divided into control group (n=61) and observation group (n=61), the control group was treated with ulinastatin and the observation group was treated with complex salvia miltiorrhiza injection on the basis of the control group. The levels of coagulation, inflammation, oxidative stress and endothelial markers were compared between the two groups. Results: After treatment, the levels of APTT and PT in the two groups were significantly higher than those before treatment, while the levels of DD were significantly lower than those before treatment, and the levels of APTT and PT [(38.19±7.05) s,(17.60±3.68) s] in the observation group were significantly higher than those in the control group, while the levels of DD [(0.51±0.10) mg/L] in the observation group were significantly lower than those in the control group;the levels of CRP, PCT and TNF-α in the two groups were significantly lower than those before treatment, and the levels of CRP, PCT and TNF-α [(29.10±4.76) mg/L, (0.59±0.17) μg/L, (57.28±10.61) ng/L] in the observation group were significantly lower than those in the control group;the levels of SOD in the two groups were significantly higher than those before treatment, but MDA was significantly lower than that before treatment, and the level of SOD [(179.10±4.76) U/mL] in the observation group was significantly higher than that in the control group after treatment, while the level of MDA [(1.97±0.55) mmol/mL] in the observation group was significantly lower than that in the control group after treatment;the levels of NO in the two groups were significantly higher than those before treatment, while the levels of ET and vWF were significantly lower than those before treatment, and the levels of NO [(10.56±1.17) U/mL] in the observation group were significantly higher than those in the control group after treatment, while the levels of ET and vWF [(105.83±5.20) pg/mL, (102.47±16.91)%] in the observation group were significantly lower than those in the control group after treatment. Conclusions:Complex salvia miltiorrhiza injection can improve the blood coagulation function, alleviate inflammation, enhance antioxidant function and vascular endothelial function in patients with acute pancreatitis, which has clinical value of promotion.

Complex post-traumatic stress disorder

Complex post-traumatic stress disorder(complex PTSD)is a severe mental disorder that emerges in response to traumatic life events.Complex PTSD is characterised by three core post-traumatic symptom clusters,along with chronic and pervasive disturbances in emotion regulation,identity,and relationships.

An Automatic Classification Grading of Spinach Seedlings Water Stress Based on N-MobileNetXt

To solve inefficient water stress classification of spinach seedlings under complex background,this study proposed an automatic classification method for the water stress level of spinach seedlings based on the N-MobileNetXt(NCAM+MobileNetXt)network.Firstly,this study recon-structed the Sandglass Block to effectively increase the model accuracy;secondly,this study introduced the group convolution module and a two-dimensional adaptive average pool,which can significantly compress the model parameters and enhance the model robustness separately;finally,this study innovatively proposed the Normalization-based Channel Attention Module(NCAM)to enhance the image features obviously.The experimental results showed that the classification accuracy of N-MobileNetXt model for spinach seedlings under the natural environment reached 90.35%,and the number of parameters was decreased by 66%compared with the original MobileNetXt model.The N-MobileNetXt model was superior to other net-work models such as ShuffleNet and GhostNet in terms of parameters and accuracy of identification.It can provide a theoretical basis and technical support for automatic irrigation.

盐碱胁迫下2,4-表油菜素内酯和褪黑素对百合幼苗光合生理的影响

以‘西伯利亚’百合种球为试材,采用室内盆栽试验的方法,研究了中度(150 mmol·L^(-1))盐碱胁迫下叶施2,4-表油菜素内酯(EBR)、褪黑素(MT)及其复合处理对百合幼苗生长、光合和叶绿素荧光参数、离子转运及抗氧化系统的影响,以期为二者缓解百合盐碱胁迫提供参考依据。结果表明:盐碱胁迫下百合株高、叶表面积以及生物量显著下降,施用EBR和/或MT可以缓解百合受到的生长抑制。150 mmol·L^(-1)盐碱胁迫下,与喷施清水对照(CK)处理相比,EBR+MT处理的SPAD值增加37.2%,百合地上部和地下部N含量分别增加83.6%和40.7%,叶绿素荧光参数中PSⅡ最大光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)和光化学淬灭系数(qP)分别增加14.6%、42.9%和50.0%,而非光化学淬灭系数(NPQ)下降9.2%,净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)分别增加56.3%、29.7%和42.7%,胞间二氧化碳(Ci)下降19.3%。150 mmol·L^(-1)盐碱胁迫下,百合地上部和地下部Na^(+)含量增加,而K^(+)含量下降,EBR+MT处理后百合地上部和地下部K^(+)/Na^(+)值分别增加110.9%和98.8%;同时,施用EBR和/或MT处理能够促进百合Cu/Zn-SOD、POD以及CAT基因的表达,激活抗氧化酶SOD、POD以及CAT活性。综上所述,施用EBR和/或MT处理均能够不同程度的提高百合SPAD值,减缓盐碱胁迫对PSⅡ光系统的抑制,维持植物体内Na^(+)和K^(+)的平衡,激活SOD、POD和CAT等抗氧化酶基因表达并提高酶活性,促进百合株高和生物量的增加,其中以复合喷施EBR+MT处理下百合幼苗的抗盐碱性效果更好。

围缘扁钢加强的开圆孔无限平板应力解析算法

为了研究围缘扁钢加强的开圆孔无限平板应力解析计算方法,近似认为围缘扁钢区域的平均应力处于广义平面应力状态。运用复变函数论的方法,将应力函数表示为两个待定的解析函数;列出围缘扁钢的边界条件、围缘扁钢与平板之间的应力连接条件和位移连接条件,求出应力函数,根据求出的应力函数便可求出应力。为了描述围缘扁钢减缓孔口应力集中的效果,提出围缘扁钢加强系数的定义。算例计算表明:本文提出的解析算法计算结果与有限元法计算结果吻合良好,围缘扁钢加强的开圆孔无限平板应力普遍小于开圆孔无限平板应力,围缘扁钢加强效果明显;相同体积的加强构件,围缘扁钢的加强效果优于环形加厚板。

复合材料复杂环境效应加速试验设计及评估方法

目的指导复合材料在复杂湿热环境下环境适应性摸底与评价试验的开展,分析评估复合材料在复杂综合应力下的激活能参数。方法分析装备全寿命周期复杂自然环境剖面及各环境因素影响效应,确定复合材料各工作阶段敏感应力类型及条件,基于应力加速模型及累积损伤等原理,制定复合材料复杂环境效应综合加速试验剖面。构建复合材料复杂环境条件下的动力学模型,并提出相应参数估计方法。开展复合材料加速试验,并基于实测数据开展复合材料性能退化建模与评估。结果分析了复合材料全寿命周期环境影响因素及环境效应,明确了各工作阶段敏感应力主要有温度、湿度、太阳辐照、温度交变、振动以及冲击等。依据实际环境数据,设计并开展了3组不同湿热条件(80℃/75%RH、80℃/85%RH、80℃/95%RH)的综合试验,收集得到复合材料拉伸强度、拉剪强度、径向弯曲强度以及纬向弯曲强度等4种性能指标的试验数据。试验数据表明,拉剪强度(最大相对退化速率为0.1773/循环)、径向弯曲强度(最大相对退化速率为0.1292/循环)以及纬向弯曲强度(最大相对退化速率为0.2610/循环)等性能参数可用于产品退化建模与评估。通过参数估计,进一步确定了退化速率与湿热应力的关系,并针对当前试验提供了改进依据。结论复杂环境效应综合加速试验对装备复合材料产品经历复杂环境条件的模拟效果和加速效果较好,试验可实施性较强。提出的改进广义Eyring模型可涵盖温度应力与湿热应力的加速效应,并综合考虑多种应力的相互作用,通过少量组合试验便可量化评估激活能等参数。所建模型指出当前基于激活能参考值(Ea=0.7eV)试验方案可由不同温度应力的综合试验数据进一步修正与优化,且所提试验与分析方法主要针对大部分树脂基复合材料产品,并可依据需要推广至电子产品、机电产品等试验对象。

矿物掺合料对复合胶凝材料浆体静态屈服应力的影响

复合胶凝材料浆体的静态屈服应力可用于表征浆体内部微观结构建立的特性,且对新拌水泥基材料的施工与3D打印过程有很大影响。本文研究了矿物掺合料的种类和掺量对复合胶凝材料浆体静态屈服应力变化规律的影响。研究发现,矿物掺合料的细度增大使颗粒表面的水膜层厚度减小,导致浆体的静态屈服应力增大。复合胶凝材料浆体的静态屈服应力在加水搅拌后的一段时间内缓慢增加,浆体结构建立速率较小。在加水搅拌后大约1.5 h,复合胶凝材料浆体的静态屈服应力迅速增大,表明浆体内部结构的连接程度已接近不可破坏的程度,浆体开始凝结,向固体状态转变。