Occupational safety and health conditions of forestry workers in Turkey

The safety and health conditions of forestry workers in Turkey were surveyed, as there are currently no statistics on these topics despite the occurrence of accidents and health problems caused by forestry work. We used a questionnaire that inquired about safety and health conditions, job satisfaction, and cumulative fatigue symptoms of forestry workers. Of the respondents, 24% experienced accidents during work, many of which consisted of cuts by chain saws or axes. Also, most respondents indicated that they did not use any personal protective equipment (PPE), although the use of PPE is strongly recommended to avoid fatal or serious accidents. With respect to job satisfaction, 43% of the respondents were dissatisfied with their job mainly because of the low salary and heavy work. Marital status, educational background and period of employment had the potential to greatly affect job satisfaction. As a result of research using the Cumulative Fatigue Symptoms Index (CFSI), mental, physical and social aspects of cumulative fatigue were recognized in the respondents. Furthermore, it can be concluded that job dissatisfaction negatively affected the incidence of cumulative fatigue in forestry workers, and that taking measures to enhance job satisfaction among forestry workers would improve their quality of life through lessening of cumulative fatigue. It should also be noted that sustainable forestry and environmental protection were the greatest concerns beyond salary and insurance among the respondents.     

Fatigue life of structural plywood under two-stage panel shear load: a new cumulative fatigue damage theory

The fatigue life of structural plywood under two-stage panel shear load was experimentally examined. Two experimental conditions were determined for two-stage fatigue of plywood specimen: one used variable applied stress and the other used variable stress, loading waveform, and loading frequency, because fatigue life of wood composite under constant load depended on loading waveform and loading frequency as well as stress level. The most famous cumulative fatigue damage theory is the Palmgren-Miner rule, which is the summation of the ratio of the applied loading cycle to the fatigue life under each loading stage. However, the applicability of this rule to the two-stage fatigue of wood composites has not been investigated. It was first demonstrated in this study that the fatigue life of the plywood specimen reached in the two-stage fatigue test did not obey the Palmgren-Miner rule. Here, we propose the new cumulative fatigue damage model by modification of the Palmgren-Miner rule on the basis of the assumption that fatigue damage accumulates with loading cycle on a logarithmic scale. The newly proposed model was in good agreement with the fatigue life reached in the two-stage fatigue test.     

农用无人机气流扰动翼疲劳有限元分析

对农用无人机气流扰动翼进行动力学分析,针对气流扰动翼疲劳寿命难以估计这一问题,利用UG三维软件建立了气流扰动翼有限元模型,并利用ANSYS Fluent流体模块设置了大气湍流模型参数,得到了气流扰动翼表面的力分布数据.农用无人机气流扰动翼疲劳有限元仿真结果为:疲劳危险点在气流扰动翼与机体连接处以及起飞和降落中,气流扰动...     

不同运动状态下鳙幼鱼的游泳特性研究

为了探究鱼类反复运动疲劳后游泳能力和游泳行为的变化,以鳙(Aristichthys nobilis)幼鱼为研究对象,利用环形水槽实验装置,采用流速递增法,通过LoliTrack视频软件分析鱼类游泳行为,研究不同运动状态下鳙幼鱼的游泳特性变化情况。结果表明,鳙幼鱼疲劳前耗氧率随游泳速度的增大显著增加,且临界游泳速度恢复过程中最大耗氧率小于突进游泳速度恢复过程中最大耗氧率。视频分析显示,摆尾频率与游泳速度呈线性正相关关系。同时发现,在2组反复疲劳运动状态下,连续进行2次临界游泳速度测定过程中,鳙幼鱼频繁使用爆发-滑行游泳行为,而在经过突进游泳速度测试后转入临界游泳速度测定过程中,实验鱼并未使用这一游泳行为。经过一次临界游泳速度测试后,第二次临界游泳速度显著大于突进游泳速度测试后的临界游泳速度(P0.05),第一次突进游泳速度与第二次突进游泳速度无显著差异(P0.05)。无氧运动消耗导致鳙幼鱼有氧运动能力显著下降,而有氧运动消耗过程对无氧运动能力无显著影响。     

基于ANSYS的谷物联合收割机设计与分析

以谷物联合收割机为研究对象,通过对收割机使用过程中的秸秆还田过程进行分析介绍,得出收割机刀辊的使用寿命是影响收割机使用性能的关键因素.对收割机刀辊结构进行受力分析,结合刀辊的使用工况,利用ANSYS技术进行刀辊疲劳寿命计算.计算分析表明:随着刀辊转速的不断增加,刀辊的损伤系数不断增加,造成剩余安全系数降低,影响使用过程...     

驾驶员疲劳状况检测中眼睛定位方法的比较与分析

驾驶员行车中大约90％的信息是从视觉得到的,因此测量眼睛闭合、眼睛运动或眼睛生理特性来监视驾驶疲劳对研究行车安全是很重要的。在检测定位人脸的基础上,提出对驾驶员眼睛定位和特征提取的方法,制定眼睛模板,对单位时间内眼睛闭合时间、睁闭的次数进行统计,然后根据试验结果比较分析各类不同的定位眼睛方法的优劣,为研发机动车驾驶员疲劳状况监测系统提供准确可靠的依据。     

疲劳驾驶监测的研究进展

介绍疲劳驾驶特征表现的产生原因以及对该问题的研究现状,并对其中几种具有代表性的疲劳状态监测方法进行了评述;提出应用信息融合技术将多种监测方法进行有机结合的方法,其是对驾驶员疲劳状态监测的发展趋势;指出驾驶员疲劳状态监测及预警装置的非接触性、车栽性和实时性研究是未来发展的方向。     

索承式桥梁吊索钢丝腐蚀疲劳寿命评估

根据吊索镀锌钢丝腐蚀疲劳破坏特点,把镀锌钢丝腐蚀疲劳纹形成和扩展过程分解成镀锌层腐蚀失效、蚀坑萌生、蚀坑形成、短裂纹扩展、长裂纹扩展和断裂破坏等阶段,建立各阶段时间表达式,得到镀锌钢丝疲劳寿命表达式,提出基于断裂力学的吊索钢丝腐蚀疲劳寿命评估研究结果方法。通过算例分析复杂运营条件下腐蚀环境和应力幅等因素对吊索钢丝腐蚀疲劳寿命的影响,研究结果表明：吊索钢丝腐蚀疲劳寿命主要由钢丝镀锌层腐蚀、蚀坑发展和短裂纹扩展等3个阶段组成,为了准确地评估吊索腐蚀疲劳寿命,需要掌握大桥的运营环境和交通荷载。     

深水网箱浮架结构的失效及疲劳性能分析

为了分析台风海况环境与系泊载荷导致深水网箱局部崩塌的现象,分析网箱部件长期承受波浪交变载荷作用而导致的疲劳破坏问题,该文自主开发网箱浮架试样的加工方法,并进行浮架管材的性能参数测定,进一步采用等效载荷有限元模拟、全场景有限元模拟与力学试验对比验证,结合有限元结构仿真分析网箱浮架的失效及疲劳情况。结果表明,网箱浮架承受拉伸及弯曲载荷时弹性变形至塑性变形的临界屈服强度为22.12和30.58 MPa;浮架应力集中及疲劳关键节点主要为焊接点、系泊点、管材联接及工字架装配边缘区域,塑性区扩展至表面且断裂伸长率大于340.18%时发生结构断裂;浮架单点系泊及均布载荷40 kN时的低周疲劳寿命为734次应力循环,主要是由于此时的结构应力大于疲劳极限3.38 MPa导致疲劳寿命减小。增大系泊面积和工字架数量、减少焊接接头、降低联接管材的SDR系数可有效提高网箱浮架的可靠性能。研究结果可为长期和极限作业环境下网箱结构的优化设计提供参考。