EXPERIENCE WITH THERMOMECHANICAL FATIGUE UNDER SERVICE-TYPE LOADING

The thermomechanical fatigue behaviour of different high temperature alloys has been investigated and is under investigation respectively. The creep-fatigue behaviour of heat resistant steels was investigated by long-term service-type strain cycling tests simulating thermomechanical fatigue (TMF-) loading conditions at the heated surface of e.g. turbine rotors. Single-stage as well as three-stage cycles leads to similar results at the application of the damage accumulation rule. Life prediction which simulates typical combinations of cold starts, warm starts and hot starts has been established successfully for isothermal service-type loading and will be exceeded for thermomechanical loading. Long-term thermomechanical fatigue testing of Thermal Barrier Coating systems show typical delamination damage. An advanced TMF cruciform testing system enables complex multiaxial loading.

Symptom experience in patients with cancer-related fatigue:A systematic review and meta-synthesis

To understand the real experiences of patients with cancer-related fatigue and to promote quality of life,the researchers used computer searches of PubMed,EMbase,CINAHL,PsycINFO,Web of Science,and China National Knowledge Infrastructure,China Biology Medicine disc,Wanfang Data,China Science and Technology Journal Database for relevant qualitative studies from the inception to November 1,2021.The results showed that a total of 16 papers were included,and 57 outcomes were distilled into 9 categories,which were pooled into four integrated outcomes,such as somatic,psychological and social support and so on.It is concluded that patients with cancer-related fatigue are not only in the midst of multidimensional,unspeakable somatic experiences,and complex psychological experiences,they are also hindered in coping with fatigue symptom and social life.Therefore,healthcare professionals should provide health interventions and psychological support to those patients whenever possible.

Fatigue behavior of basalt-aramid and basalt-carbon hybrid fiber reinforced polymer sheets

In order to study the fatigue failure mode and fatigue life laws of basalt-aramid and basalt-carbon hybrid fiber reinforced polymer （ FRP ） sheets, fatigue experiments are carried out, considering two hybrid ratios of 1 ： 1 and 2：1 under different stress levels from 0.6 to 0.95. The results show that fractures occur first in carbon fibers or aramid fibers for the specimens with hybrid ratio of 1： 1, namely B1A1 and B1C1, while a fracture occurs first in basalt fibers for the specimens with a hybrid ratio of 2： 1, namely B2A1 and B2C1. The fatigue lives of the hybrid FRP sheets increase with the improvement of the content of carbon fibers or aramid fibers, and the influence of the carbon fibers content improvement to fatigue life is more significant. The fatigue performance of B2A1 is relatively worse, while the fatigue performance of B1C1 and B2C1 is relatively better. Finally, a new fatigue stiffness degradation model with dual variables and double inflection points is presented, which is applicable to both hybrid and normal FRP sheets.

PRE-CORROSION FATIGUE NOTCH FACTOR

The notched and smooth specimens of aluminum alloy LC4CS soaked in EXCO solution for different time are tested under the constant amplitude cyclic loading to obtain S-N curves and fatigue notch factors with different pre-corrosion time. By analyzing the corrosion process of LC4CS specimens in EXCO solution, the influ- ence mechanism of corrosion on fatigue notch factor is expounded. Then, a two-parameter model used to describe the change of corrosion fatigue notch factor with time is established and verified by experiment. The results show that the pre-corrosion fatigue notch factor of LC4CS material decreases at first and then increases with the increasing pre-corrosion time. The inflection point appears at the beginning of denudation stage.

Effect of ultrasonic peening treatment on the fatigue behaviors of a magnesium alloy up to very high cycle regime

Ultrasonic fatigue tests are performed on a magnesium alloy with and without ultrasonic peening treatment(UPT).Surface enhancement layer leads to the complete change of crack initiation sites.However,crack initiation mechanism keeps the same and results in a single-faceted morphology at crack initiation site.Microcracks initiate as Mode Ⅱ crack within the original grain,but deflect to Mode I crack outside of the original cracked grain.A threshold SIF value is proposed to evaluate the retarding effect of grain boundary on microcrack propagation.Outside of the original cracked grain,Mode I crack propagation below the threshold ΔK_(σ-th) is responsible for the formation of fine granular area(FGA,a nano-grain layer).Based on the Numerous Cyclic Pressing(NCP) model,it is proposed that crack type should be another necessary condition for the formation of FGA.

Squat,Stoop,or Semi-squat:A Comparative Experiment on Lifting Technique

There are actually no sufficient data for lifting technique assessment.A laboratory study was undertaken to determine the effect of 3 regular lifting techniques on erector muscle activation,cardiovascular strain and subjective response.Thirty student volunteers participated in the study,and were required to lift a weight with different techniques.Stoop-,squat-,semi-squat-lifting resulted in 3,2 and 1 time of the highest percentage of the maximum voluntary electrical activation(MVE%) respectively.In the same order,the lowest median frequency(MF) existed 1,1 and 2 times.Muscle fatigue was 4 times in squat,36 in semi-squat and 43 in stoop lifting.Heart rate was the highest in squat and lowest in stoop respectively,with a middle level in semi-squat lifting.It may be recommended to adopt mainly the semi-squat technique for daily lifting works.For heavy lifting,it should use the squat technique.Stoop lifting may also be used alternatively but for light things.

Study on Hydrogen Environment Fatigue Test System and Correlative Fatigue Test of Hydrogen Storage Vessel

A 70 MPa hydrogen environment fatigue test system has been designed and applied in the manufacture of a hydrogen storage vessel. The key equipment is a 80 MPa flat steel ribbon wound high pressure hydrogen storage vessel. A reasonable stress distribution has been realized, which is low stress on the liner of the pressure vessel and even stress on the flat ribbon layers. This optimal stress distribution is achieved through the adjustment of the prestress in flat steel ribbons. A control system for the fatigue test system has also been designed. It consists of a double control model, manual control and automatic control, to satisfy different experiment requirements. The system is the only one which can be used in the real hydrogen environmental fatigue test system in China. An experiment for a 70 MPa onboard composite material hydrogen vessel has been carried out on the system. The experimental results from this test are in close agreement with the practical operating conditions.

Influencing factors of fatigue in young and middle-aged patients with coronary heart disease:a cross-sectional study

Objective:To examine the present state of fatigue in young and middle-aged patients with coronary heart disease(CHD)and to identify the elements that may be affecting it.Methods:From December 2020 to June 2021,240 young and middle-aged patients with CHD who were being treated in the cardiology department of a tertiary care hospital in Suzhou were chosen using a convenience sampling method in order to gather data on the patients’sociodemographic status,fatigue,social support,and stress.Results:Of the 240 disseminated questionnaires,220 valid responses were returned,resulting in an effective recovery rate of 91.67%.The frequency of exhaustion was 51.8%,and the fatigue score was(5.27±2.77).The stress score was(11.15±3.36),while the overall social support score was(39.13±4.72).Binary logistic regression analysis indicated that age,exercise,staying up late,stress,social support,high-sensitivity troponin T,high-density lipoprotein,and ejection fraction were independent risk factors for fatigue in young and middle-aged patients with CHD(P<0.05).Conclusions:Fatigue is more prevalent in young and middle-aged patients with CHD.Clinical nurses can create a unique management plan for patients based on their lifestyle and behavioral patterns,stress levels,social support,and clinical signs to reduce fatigue.

Application of ultrasonic fatigue technology in very-high-cycle fatigue testing of aviation gas turbine engine blade materials:A review

The need for very-high-cycle fatigue(VHCF)testing up to 1010cycles of aviation gas turbine engine blade materials under combined mechanical loads and complex environments has encouraged the development of VHCF testing instrumentation and technology.This article begins with a comprehensive review of the existing available techniques that enable VHCF testing.Recent advances in ultrasonic fatigue testing(UFT)techniques are highlighted,containing their new capabilities and methods for single load,multiaxial load,variable amplitude fatigue,and combined cycle fatigue.New techniques for conducting UFT in high-temperature,humid environments,and corrosive environments are summarized.These developments in mechanical loading and environmental building techniques provide the possibility of laboratory construction for real service conditions of blade materials.New techniques that can be used for in situ monitoring of VHCF damage are summarized.Key issues in the UFT field are presented,and countermeasures are collated.Finally,the existing problems and future trends in the field are briefly described.

Microstructure features induced by fatigue crack initiation up to very-high-cycle regime for an additively manufactured aluminium alloy

Fatigue failure can still occur beyond 107 cycles,i.e.very-high-cycle fatigue(VHCF),in many metallic materials,such as aluminium alloys and high-strength steels.For VHCF of high-strength steels,a fine granular area(FGA)surrounding an inclusion is commonly identified as the characteristic region of crack initiation on the fracture surface.However,no such FGA feature and related crack initiation behaviour were observed in VHCF of conventionally cast or wrought aluminium alloys.Here,we first reported the distinct mechanisms of crack initiation and early growth,namely the microstructure feature and the role of FGA in VHCF performance for an additively manufactured(AM)AlSi10Mg alloy.The AM pores play a key role in fatigue crack initiation similar to that of the inclusions in high-strength steels,resulting in almost identical FGA behaviour for different materials under a range of mean stress with a stress ratio at R<0 or R>0.The profile microstructure of FGA is identified as a nanograin layer with Si rearrangement and grain boundary transition.This process consumes a large amount of cyclic plastic energy making FGA undertake a vast majority of VHCF life.These results will deepen the understanding of VHCF nature and shed light on crack initiation mechanism of other aluminium and AM alloys.

Effects of loading condition on very-high-cycle fatigue behaviour and dominant variable analysis

The specimens of a high carbon chromium steel were quenched and tempered at 150℃, 180℃ and 300℃. Such specimens were tested via rotating bending and a push-pull type of axial loading to investigate the influences of loading condition on the behaviour of very-high-cycle fatigue （VHCF）. Experimental results show the different influences of inclusion size on the fa- tigue life for the two loading conditions. Predominant factors and mechanism for the fine-granular-area （FGA） of crack origin were discussed. In addition, a reliability analysis based on a modified Tanaka-Mura model was carried out to evaluate the sen- sitivity of inclusion size, stress, and AKFGA to the life of VHCF crack initiation.

高压涡轮盘螺栓孔疲劳模拟件设计及试验

航空发动机关键件采用模拟件开展试验可在一定程度上替代真实结构试验,从而大幅节省试验周期和成本。为满足某型发动机高压涡轮盘定寿需求,减少真实轮盘低循环疲劳的试验成本,本文采用考虑应力梯度影响的结构特征模拟件设计方法,设计了该发动机高压涡轮盘螺栓孔部位的结构特征模拟件,开展了特征模拟件及轮盘真实结构的低循环疲劳试验;对于模拟件试验结果,应用统计学方法得到了具有一定置信度和可靠度的模拟件寿命和分散度,采用该分散度计算得到的模拟件安全循环寿命和轮盘实际试验结果相比,模拟件安全循环寿命小于轮盘实际低循环疲劳寿命,误差为14.69%,该螺栓孔模拟件设计及低循环疲劳试验研究可用于指导实际轮盘的定寿工作,具有一定的工程参考价值。

表面肌电测试技术在研究生实验教学中的应用

利用表面肌电测试技术测量肌肉疲劳,开设研究型实验教学项目,让学生充分发挥主观能动性,独立设计实验方案,独立判断实验方案的合理性,以及运用基本实验技能进行实验操作和数据分析,熟练掌握表面肌电测试方法。该实验教学项目充实了兵器专业研究生的实验教学内容,能够培养学生的科学思维、创新精神和具体实验技能,为学生今后的科研和工作提供必要的实验手段。

卒中后疲劳患者疲劳体验及应对策略的质性研究

目的深入了解卒中后疲劳患者疲劳体验及应对策略,为制定针对性护理方案提供参考。方法采用描述性质性研究,按照目的抽样法选取16例卒中后疲劳患者进行半结构访谈,运用主题分析法对访谈资料进行分析与整理。结果卒中后疲劳患者疲劳体验共提炼出4个主题:卒中后疲劳特征、日常生活陷入紊乱状态、与他人讨论疲劳的反馈、渴望获得支持与理解。疲劳应对策略共提炼出2个主题:努力克服及适应疲劳、逃避或放弃应对疲劳。结论医护人员应重视卒中后疲劳患者的疲劳筛查与评估,鼓励患者正确应对疲劳,并采取多渠道的综合干预策略,缓解患者的疲劳症状。

卒中后疲劳患者疲劳体验质性研究的Meta整合

背景既往研究显示,脑卒中患者卒中后疲劳(PSF)发生率高达25%~85%,持续不断的疲乏感严重影响患者日常生活和康复进程,因此亟需了解此类患者的心理体验和需求,但既往已进行的单一的质性研究结果可能不具有代表性。目的系统评价和整合卒中后疲劳患者疲劳体验的质性研究,为构建PSF患者疲劳管理策略提供依据。方法计算机检索PsycINFO、PubMed、Web of Science、CINAHL、Cochrane Library、Scopus、澳大利亚安娜布里格斯研究所(JBI)循证卫生保健数据库及中国知网、万方数据知识服务平台、维普网、中国生物医学文献数据库,搜集与PSF患者疲劳体验相关的质性研究。检索时限为建库至2023-07-05。采用澳大利亚JBI循证卫生保健中心质性研究质量评价标准(2016)进行质量评价,并采用汇集性整合的方法进行Meta整合。结果共纳入10篇文献,提炼出22个主要结果,归纳为8个类别,综合为4个整合结果:对PSF的认知严重匮乏;存在错综复杂的负性身心体验;PSF的自我调适方式多样;存在多种PSF康复需求。结论PSF患者对疲劳认知不足且存在明显负性身心体验,因此应早期识别和筛查PSF患者,强化对患者的疲劳教育并为其制订个性化疲劳管理策略,同时应重视发挥社区和家庭在PSF患者疲劳管理中的作用,使其与医护人员一同为PSF患者提供良好的康复环境。

血液透析患者疲劳体验及管理质性研究的Meta整合

目的系统评价与整合血液透析患者疲劳体验及管理的质性研究。方法计算机检索Cochrane Library、Web of Science、PubMed、CINAHL、Embase、Scopus、CBM、知网、万方、维普数据库建库至2023年12月发表的关于血液透析患者疲劳体验或管理的质性研究,采用汇集性整合方法对结果进行Meta整合。结果共纳入9篇文献,提炼出38个结果,形成10个类别,汇总成4个整合结果:血液透析患者对疲劳的认知、疲劳产生的影响、患者自我管理策略、疲劳管理需求及挑战。结论血液透析患者疲劳管理存在认知缺乏、负性情绪影响、自我管理策略不全面、干预措施不精准等障碍,医疗机构应构建多样化管理策略并提供全面支持,完善患者自我管理策略,延长血液透析患者生存周期并提高其生活质量。

海洋食品酶解物改善精神疲劳功能性评价的综合实验设计

该文设计了以小鼠模型评价海洋食品酶解物对改善精神疲劳营养功能的创新性综合实验,以海参和牡蛎两种海洋生物资源为原料,通过酶解法制备了海参酶解物和牡蛎酶解物,测定了两种酶解物的氨基酸组成,探究了两种酶解物对皮质酮所致精神疲劳模型小鼠耐力、焦虑样行为、抑郁样行为以及神经递质水平的影响。结果表明海参酶解物和牡蛎酶解物均可显著提高精神疲劳小鼠的耐力表现,并改善焦虑样行为和抑郁情绪,其中,海参酶解物在改善焦虑样行为方面更显著,而牡蛎酶解物在改善抑郁情绪方面更显著。进一步研究发现两种酶解物通过调节神经递质水平改善精神疲劳。该综合实验结合了海洋生物资源精深加工技术、食品检验与分析、食品营养学、功能性食品等多领域实验技术,有助于提高学生的学习积极性、深化学生所学理论知识、培养其创新思维和实验技能。

基于品质因数的超声刀刀头疲劳振动评价研究

目的:针对超声刀刀头疲劳效能评价存在的难题,提出基于品质因数的超声刀刀头疲劳振动评价方法。方法:首先,搭建由电源模块、三轴移动模块、超声刀夹持模块和控制模块组成的可实现重复切割操作的超声刀疲劳试验台。其次,采用该试验台对10台某品牌超声刀实施疲劳试验,在疲劳试验的5个阶段(即未切割、500次切割后、1000次切割后、2000次切割后和3000次切割后)对超声刀刀头振动进行非接触式测量并计算其品质因数。最后,计算各阶段试验的平均切割速度和血管凝闭爆破压,以验证基于品质因数的超声刀刀头疲劳振动评价方法的有效性。结果:试验表明,品质因数指标能够有效地反映超声刀刀头的疲劳退化特征,而平均切割速度和血管凝闭爆破压由于测量过程中的不确定性因素不易控制,很难对超声刀刀头的疲劳退化水平进行有效评价。结论:提出的基于品质因数的评价方法可直接对超声刀刀头的疲劳振动进行精准量化评价。

名中医贾英杰运用“培本三法”辨治癌因性疲乏经验

癌因性疲乏作为癌症患者的高发生率伴随症状,目前西医尚缺乏有效的干预手段。基于癌症“正气内虚,毒瘀并存”的病因,贾英杰教授认为癌因性疲乏所以发病,盖因癌毒之“浊邪”胶聚于患者体内,阻碍患者气血运行,恶耗患者本元正气。治疗应重视培植本元,法当补益气血、滋补肝肾、健运脾胃。重视从气论治,调气运中,注重先天与后天之本,化生优质气血送达脏腑,改善患者脏腑虚损、气血双亏的状态。总结贾英杰教授临床用“培本三法”治疗癌因性疲乏的心得体会,结合医案分享重剂黄芪、川续断、白术等验药的具体应用,以期为此病提供诊疗思路借鉴。

胡作为教授治疗癌因性疲乏经验撷萃

癌因性疲乏是恶性肿瘤患者临床上较为常见的并发症,除疾病的影响外,放化疗等治疗手段施加也会加重癌因性疲乏的临床症状。癌因性疲乏发生主要责之脏腑虚损、气血不足、阴阳虚衰、瘀毒留滞,本虚标实为其根本病机。治疗上采取补气健脾以生化气血,调补脾肾以权衡阴阳,调畅气机以求通补气血,攻补兼施以治瘀毒留滞。从病因病机、辨证思路与治疗等方面总结胡作为教授在治疗癌因性疲乏方面的临证经验,将为临床治疗提供更多思路。