Experiences of Fatigue at Sea—A Comparative Study in European and Chinese Shipping Industry

Fatigue has negative impacts on the general working population as well as on seafarers. In order to study seafarers’ fatigue, a questionnaire-base survey was conducted to gain information about potential risk factors for fatigue and construct indexes indicating fatigue. The study applies T-test to compare strata of seafarers to analyse work and sleep patterns in global seafaring. Qualitative analysis are also employed to explore the impacts of fatigue on seafarer’s occupational health and safety.

Comparative Analysis of Facility Present Condition of Selected Schools and Hospitals in Rivers State, Nigeria

This article investigates the comparative analysis of the facility present condition (FPC) of selected health and educational buildings in Rivers State. State funded hospitals and schools (14 functional out of 23 general hospitals and 2 out of 3 tertiary schools) were selected for the study. The general hospital is a secondary health facility designed to bring health care services close to citizens especially those in rural communities. These facilities were inherited from the colonial masters in 1960. An assessment visit in2016 found the 23 general hospitals completely dilapidated and abandoned. However, rehabilitation intervention was carried out by the government in 2020. This scenario was quite different with the schools. Thus, this study is to increase the awareness of facility operators on building maintenance. A purposive sampling technique was used in selecting the hospitals and schools, while simple random sampling was adopted for questionnaire distribution to 300 respondents. The instrument reliability and validity were ascertained using Cronbach Alpha and face validity. The instrument obtained information about the status of the facility present condition. SPSS and Microsoft Xlstat were used to obtain the mean and frequency distribution of the responses. Comparative analysis was conducted to understand the FPC of the schools and hospitals. Z-test was deployed to ascertain if there was a significant difference in the FPC between the two institutions. Checklist was adopted to confirm the findings. The result from the survey showed that schools have better FPC than hospitals.

Test and Analysis of the Sound Insulation Performance of Four Types of Timber Structure Floors under Jumping Excitation

To improve the impact sound insulation performance of building floors and meet the objective requirements for living comfort of residents,in this article,three kinds of elastic cushion materials,Portuguese cork board,BGL insulation sound insulation foam board,and EPP polypropylene plastic foam board,are applied to the sound insulation of a light frame wood floor structure of the same bedroom and compared to the ordinary floor.This study uses the transfer function method and transient excitation method to measure the sound insulation,damping ratio,and elastic modulus of materials,as well as the sound insulation of the floor under the jumping excitation method of daily behavior.Through comparative analysis,the results and factors of improving the sound insulation performance of the floor are obtained,according to which three types of elastic cushion materials and the floor covering composed of them have higher vibration and noise reduction performance.Among them,the overall sound insulation performance of BGL board floor is the highest,followed by EPP board and cork board floor,and ordinary OSB floor is the lowest.Under the jumping excitation method,three floating floors can improve the impact sound insulation performance of the middle and low-frequency bands.

Fatigue Test of Homemade Z Direction Steel Welded T Tubular Joints

This paper introduces the process and result of fatigue test of steel (Z direction steel) welded T tubular joints used in offshore engineering. Detailed measurement of stress concentration factor, stress distribution, fatigue life and crack development has been performed. Through analysis, an empirical formula of stress concentration factor for T tubular joints, fatigue S-N curve and crack propagation rule are obtained.

Finite element simulation and optimal analysis of surfacing on steel orthotropic bridge deck

To analyze the stress state of steel orthotropic deck pavement and provide reference for the design of the overlay, the inner stress state and strain distribution of surfacing under the load of the deformation of the whole bridge structure and tyre load are analyzed by the finite element method of submodeling. Influence of surfacing modulus on the strain state of the overlay is analyzed for the purpose of the optimal design of the overlay structure. Analysis results show that the deformation of the whole bridge structure has no evident influence on the stress state of the overlay. The key factor of the overlay design is the transverse tensile strain in the overlay above the upper edge of web plate of rib. The stress state of the overlay is influenced evidently by the modulus of rigidity transform overlay. And the stress state of the overlay can be optimized and lowered by increasing the modulus and thickness of rigidity transform overlay, The fatigue test has been done to evaluate the fatigue performance and modulus of different deck pavement materials such as epoxy asphalt, SBS modified asphalt, rosphalt asphalt which can provide reference for deck pavement structure design.

Virtual vibration test rig for fatigue analysis of dozer push arms

To obtain accurate fatigue life results for construction machinery components,acquiring load spectra is crucial,as their authenticity and validity directly determine the precision of the analysis.In working conditions,component attitudes change continuously,but they remain static on the vibration test rig(VTR),so the acquired target signals should match with the actual component attitudes in the driving signal generation.This paper proposes an efficient and economical simulation-based virtual VTR for fatigue analysis of dozers.First,the relationship between the push arm rotation angle and the cylinder stroke is established,since the cylinder strokes can be measured easily in data acquisition experiments.Second,load decomposition is used to determine the attitude relationship between virtual VTR conditions and actual conditions,and target signals are calculated based on this attitude relationship and measured data.According to the system's frequency response function,the driving signals are iterated until the system's response signals converge with the target signals.Finally,the iteratively obtained load spectra are utilized for fatigue life analysis.The results show that the virtual VTR can effectively and accurately obtain the results of fatigue analysis and has engineering application significance.

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.

Combinatorial Method with Static Analysis for Source Code Security in Web Applications

Security weaknesses in web applications deployed in cloud architectures can seriously affect its data confidentiality and integrity.The construction of the procedure utilized in the static analysis tools of source code security differs and therefore each tool finds a different number of each weakness type for which it is designed.To utilize the possible synergies different static analysis tools may process,this work uses a new method to combine several source codes aiming to investigate how to increase the performance of security weakness detection while reducing the number of false positives.Specifically,five static analysis tools will be combined with the designed method to study their behavior using an updated benchmark for OWASP Top Ten Security Weaknesses(OWASP TTSW).The method selects specific metrics to rank the tools for different criticality levels of web applications considering different weights in the ratios.The findings show that simply including more tools in a combination is not synonymous with better results;it depends on the specific tools included in the combination due to their different designs and techniques.

基于AquiferTest的抽水试验参数计算方法分析

抽水试验是水文地质勘查中最常用的水文地质试验,通过抽水试验,可准确计算水文地质参数。本文根据在河南豫东地区进行的抽水试验,分别用AquiferTest软件计算抽水试验参数和人工求参,进而进行对比分析得出:传统的人工求参,计算结果较为准确,可靠,但因人而异,有不唯一性;用AquiferTest软件计算抽水试验参数,规范、可比性好。本文最后还对参数取值问题进行了分析对比。

Comparative in-vitro analysis of different brands of paracetamol tablets available in Nepal

Objective:To examine the physico-chemical parameters of commercially available local and multinational brands of paracetamol tablets in Nepal.Methods:Different five paracetamol brands were explored by testing various parameters according to standard methods.The studied parameters included weight variation,friability,disintegration,dissolution and assay.The limits of the official test were referenced from official guidelines of Indian Pharmacopoeia(IP)and British Pharmacopoeia(BP).All brands were tested according to their pharmacopoeial claim and methods for these tests were successfully conducted to find out their qualities.Those methods were economic and authentic.Results:Requirements of weight variation and friability value were complied by all brands.Fifteen minutes of disintegration time were also complied by all the brands according to the BP/IP recommendation for uncoated tablets.All brands showed not less than 80%drug release in 45 min as per BP and not less than 85%in 30 min as per IP.Content of each brand was found to be within the range of 95%-105%.The present findings suggested that about every paracetamol brand which was accessible in Nepali market encountering the IP/BP requirements.Conclusions:Although the physico-chemical examinations such as weight variation,friability,disintegration,dissolution and assay were detected varying brand wise,but were found interior to defined limits.Being an over-the-counter drug,the consumption of paracetamol is too high.Therefore,it is important for each brand to be genuine,good manufactured and well marketed.So,additional exploration over the quality of paracetamol is compulsory for safe human consumption.

Mn25Al7钢焊接接头的疲劳性能试验研究

Mn25Al7钢是一种新型的轻质高强船用钢,目前针对Mn25Al7钢的疲劳性能尚未开展相关试验研究。本文对Mn25Al7钢的母材、对接焊接接头及T型焊接接头等典型节点进行疲劳试验研究,分别基于名义应力方法和热点应力方法拟合得到典型节点疲劳等级曲线,并与现有规范的疲劳等级曲线进行对比分析。对三种试样的断口形貌进行观测,分析其裂纹扩展规律和断裂机理。试验结果表明:Mn25Al7钢母材疲劳寿命高于按规范设计的普通钢材;规范低估了母材和磨平焊趾的对接焊缝接头疲劳寿命,但能较好地评估T型焊缝接头的疲劳寿命。通过对比分析三种试件的损伤速率差别,进一步对断口形貌进行了系统分析,发现初始裂纹源和焊接残留物会造成疲劳强度的降低。本研究可为船用高强钢的疲劳寿命预测提供理论依据和试验支撑。

一种在线快速图像抖动消除方法及其在疲劳试验中的应用

提出一种基于先验信息的直方图匹配算法,以实现疲劳试验中试件观测图像抖动的在线快速消除。首先,根据灰度阈值对基准帧图像和目标帧图像计数统计形成直方图;其次,采用傅里叶变换将直方图变换为频域信息,并根据先验信息确定偏移阈值,进行互相关分析从而获得互相关数组;最后,选取互相关数组中的最大值,并根据最大值位置确定目标帧图像的抖动量,进行图像抖动的消除。基于先验信息的互相关频域分析极大地降低了计算量,从而使得本研究方法可以实现高分辨率图像中抖动的在线快速消除。试验结果表明,对于分辨率为4096×3000的图像,在保持抖动消除效果不变的情况下,本研究算法与传统方法相比,计算效率提高了3倍,能满足疲劳试验中试件观测的试验应用需求。

重载铁路桥梁体外预应力筋加固性能研究

运营提载会导致重载铁路桥梁损伤累积和刚度退化加剧,对重载铁路预应力混凝土桥梁进行加固可以改善桥梁的受力状况,提高桥梁承载能力。为了研究重载铁路桥梁体外预应力筋加固的性能,分别制作重载铁路24 m超低高度预应力混凝土梁的未加固足尺试验模型与体外预应力筋加固足尺试验模型,并开展200万次疲劳试验与疲劳后静力试验。建立未加固预应力混凝土梁与体外预应力筋加固预应力混凝土梁的精细化有限元模型,通过试验与有限元分析,研究加固前后重载铁路预应力混凝土梁的静力与疲劳性能,揭示加固前后梁体挠度和应力变化规律,并分析不同轴重列车作用下加固预应力混凝土梁的力学性能。研究结果表明:重载铁路桥梁外加预应力筋的加固效果良好,疲劳试验中加固梁刚度退化幅度、跨中挠度、梁内预应力筋应力、梁底及下翼缘混凝土应力显著比未加固梁的小;在33 t轴重列车与1.2倍中等荷载(ZH)轴重作用下,外加预应力筋加固的24 m超低高度预应力混凝土梁的适应性良好,预应力混凝土梁挠度与应力响应均符合规范要求。研究结果可为重载铁路桥梁的设计、养护、维护与加固提供基础与参考。

姿控推力室隔热框断裂故障分析及改进

针对某姿控动力系统推力室在力学环境试验过程中发生的隔热框断裂故障,对故障部位进行断口分析和结构强度分析,发现在高量级随机振动条件下隔热框支撑肋根部存在严重的应力集中,导致发生疲劳断裂。通过改进隔热框支撑肋结构,经强度分析和推力室力学环境试验验证,隔热框未再发生类似故障,表明改进措施方案可靠有效。

大型铺管船托管架疲劳损伤实时监测应用与研究

托管架长期承受着交变载荷的作用,结构疲劳破坏问题不容忽视。为此,本文分别基于波浪谱和监测数据对托管架的疲劳问题进行研究。通过计算结果的对比分析,发现基于波浪谱的疲劳损伤计算,由于波浪荷载的随机性很强,导致计算结果偏于保守,适用于设计阶段结构的疲劳寿命预报评估;而基于实时监测数据的疲劳损伤计算,数据相对更加准确,适用于实时评估结构当前的疲劳损伤情况,并依此提出适当的维修和保养建议。

单点系泊液滑环驱动臂设计与验证

驱动臂是驱动液滑环与浮式生产储油轮(floating production storage and offloading,FPSO)之间发生相对转动的重要连接组件,避免连接传递偏心荷载引发密封失效是该装置的设计关键。依托南海奋进号FPSO液滑环的国产化项目,本文设计了一种多点铰接形式的柔性连接驱动臂,通过有限元分析校核了驱动臂设计结构的静态强度和疲劳强度。通过开展驱动臂的动态摇摆与旋转试验,验证了往复摆动工况下驱动臂的驱动功能与载荷传递性能,为FPSO单点系泊液滑环的国产化提供了重要参考。

螺栓连接波纹腹板钢梁疲劳性能试验与分析

对2根螺栓连接波纹腹板钢梁试件进行疲劳试验研究,获得了钢梁试件的疲劳性能指标以及失效破坏形态,分析了钢梁截面的应力分布以及循环荷载作用下的应力和刚度变化。汇总现有的焊接波纹腹板钢梁疲劳试验结果,比较分析了焊接钢梁与螺栓连接钢梁的疲劳寿命差异。采用有限元软件ABAQUS建立了螺栓连接波纹腹板钢梁的精细数值模型,根据疲劳试验结果验证了数值模型的准确性。利用经验证的数值模型,对疲劳破坏位置附近的应力分布进行有限元分析,结果表明螺栓孔边应力集中是疲劳裂纹萌生和引发疲劳破坏的主要原因。基于有限元分析结果,利用FE-Safe软件对螺栓连接波纹腹板钢梁试件的疲劳寿命进行分析,计算得到的疲劳寿命和疲劳破坏位置与试验结果吻合良好。

基于有限元分析的连续油管寿命研究及预测模型

目前针对连续油管的寿命预测研究较少,但在实际的生产中连续油管的突然失效会造成极大安全隐患,急需解决方案。针对此问题,本文使用有限元仿真方法,针对三种规格的CT80连续油管在不同工况下进行有限元分析,得到了连续油管的受力、形变和疲劳寿命。用疲劳试验对有限元分析进行验证,证明了有限元分析的疲劳寿命的准确性。将连续油管的直径、壁厚、内压、弯曲半径参数转化为外壁应变和环向应力,通过数据拟合建立了关于外壁应变、环向应力和疲劳寿命之间的全经验公式,得到连续油管疲劳寿命预测模型。并用试验得出的结果与疲劳寿命预测模型进行比较,误差较小,可用于CT80连续油管的疲劳寿命预测,最后通过疲劳试验得到了连续油管在二级加载下的疲劳寿命模型,该模型可预测油管在第二级载荷下的剩余疲劳寿命。

三种石英晶体谐振器频率测试方法对比分析研究

测试石英晶体谐振器频率的传统方法有间接计算法、信号源起振法和网络分析仪法,三种方法各有大的缺陷。根据石英晶体谐振器频率的特点,提出三种新的测试方法:示波器测试法、频率计测试法和频谱仪测试法。这三种方法在基本测试原理、设备配置要求、测试精度和适用环境等方面存在差异。对三种方法的优缺点进行了详细比较,并针对不同应用条件提出了选用建议:如果只单纯测量石英晶体谐振器频率,选用频谱仪测试法;如果需要测量频率的同时还需要知道频率的特性等内容,宜选用频率计测试法;示波器测试法则可用在对石英晶体谐振器频率定性的粗测。此外,还根据各自的优势探讨了仪器协作测试的可能性。

正交异性钢-钢纤维混凝土组合桥面板疲劳极限状态研究

为了解正交异性钢-钢纤维混凝土(Steel Fiber Reinforced Concrete,SFRC)组合桥面板的疲劳性能及失效机理,以川南城际铁路临港长江大桥为背景,设计、制作正交异性钢-SFRC组合桥面板足尺模型进行疲劳试验,采用ANSYS软件建立试件有限元模型,研究关键细节的疲劳应力和开裂等情况。基于有限元模型,分析不同设计参数(钢顶板厚度、栓钉布置、SFRC抗拉强度及层厚)下组合桥面板疲劳极限状态的失效模式,并提出了主要控制参数取值建议。结果表明:200万次疲劳加载后足尺模型的实测最大裂缝宽度为0.136 mm,出现在SFRC层上缘,钢结构未开裂,组合桥面板疲劳性能良好;组合桥面板疲劳极限状态主要由SFRC层开裂控制,钢顶板厚度、栓钉布置对组合桥面板疲劳性能的影响较小,SFRC抗拉强度和层厚对组合桥面板疲劳性能影响较大,为主要控制参数;在常规正交异性钢桥面板上铺设薄层(厚度不超过50 mm)SFRC时,SFRC抗拉强度不应小于5 MPa,在常规正交异性钢桥面板上铺设普通SFRC(钢纤维体积含量不高于1%,抗拉强度不高于3 MPa)时,SFRC层厚不宜低于100 mm。