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Using the Stress Concentration Factor in Determining the Fracture Toughness 用应力集中系数测定断裂韧性
IF 0.7 4区 工程技术 Q4 Physics and Astronomy Pub Date : 2022-10-21 DOI: 10.5755/j02.mech.31226
Goksel Saracoglu
This paper offers the use of stress concentration factor in determining the critical fracture stress and fracture toughness of polymeric composite materials at various crack length ratios. The stress intensity factor has been turned into a function of the stress concentration factor derived from the maximum stress occurring at the notch tip and the tip stress generated by the force applied to the sample. This conversion allowed the use of a fixed theoretical radius (1.2732 mm) instead of the actual radius of the notch or crack. On the edge cracked three-point bending and tensile samples, the specified method detects the three point bending fracture stresses with a maximum error rate of 1.2%. This study also establishes a relationship between the clamped end and the pin-loaded tensile specimens and states that the underlying mechanism of the stress intensity factor of the clamped end tensile specimen is based on the normalization of the stress intensity factor of the pin-loaded conditions with the geometric correction factor.
本文提出了应力集中因子在确定聚合物复合材料在不同裂纹长度比下的临界断裂应力和断裂韧性方面的应用。应力强度因子已转化为应力集中因子的函数,该应力集中系数源自在缺口尖端处发生的最大应力和由施加到样品的力产生的尖端应力。这种转换允许使用固定的理论半径(1.2732毫米),而不是缺口或裂纹的实际半径。在边缘裂纹的三点弯曲和拉伸样品上,规定的方法检测三点弯曲断裂应力,最大误差率为1.2%。本研究还建立了夹持端和销加载拉伸试样之间的关系,并指出夹持端拉伸试样应力强度因子的潜在机制是基于销加载应力强度因数的归一化具有几何校正因子的条件。
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引用次数: 0
Numerical Modelling of Moisture Transport Between Two Enclosures Connected by a Tube 用管子连接的两个外壳间水分传输的数值模拟
IF 0.7 4区 工程技术 Q4 Physics and Astronomy Pub Date : 2022-10-21 DOI: 10.5755/j02.mech.32166
Z. Staliulionis, G. Miliauskas, S. Mohanty, J. Hattel
The electronics is protected using plastic or metallic enclosures. Although, the electronics is protected by the enclosures from the surrounding environment, the moisture can still enter the enclosure via gasket, plastic enclosure walls, cable feedthroughs. The moisture existing inside enclosure may condense on PCBA or components due to a temperature changes or different temperature levels and can lead to a moisture-related failures. The temperature in the enclosure is also very dependent on the location and the heating of electronic components. Furthermore, the electronics can be mounted nearby to other heating or cooling components in the complex mechanical systems, such as water pump or water meter. The paper concerns the complex transient heat and mass transfer processes between two connected enclosures with one being warm and another cold. The objective of the paper is to develop an in-house code based on the RC approach for predicting and studying the temperature and moisture behaviour inside two connected enclosures. The developed RC model combines one-dimensional description and lumped analysis for heat and mass transport. The modelling of temperature and moisture response is carried out under non-isothermal B3 STANAG ambient conditions. Moreover, the effect of different material of warm enclosure and the heating are considered.
电子设备使用塑料或金属外壳保护。虽然,电子设备受到外壳的保护,免受周围环境的影响,但水分仍然可以通过垫圈,塑料外壳壁,电缆馈线进入外壳。由于温度变化或不同的温度水平,外壳内部存在的水分可能会凝结在PCBA或组件上,并可能导致与水分相关的故障。外壳内的温度也非常依赖于电子元件的位置和加热。此外,电子设备可以安装在复杂机械系统(如水泵或水表)的其他加热或冷却部件附近。本文研究了两个相连的冷热壳体之间复杂的瞬态传热传质过程。本文的目的是开发一个基于RC方法的内部代码,用于预测和研究两个连接的外壳内的温度和湿度行为。所建立的钢筋混凝土模型结合了一维描述和热量和质量传递的集中分析。在非等温B3 STANAG环境条件下进行了温度和湿度响应的建模。此外,还考虑了不同保温材料对保温效果的影响。
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引用次数: 0
Effects of Addition of Glass Fibers and SiC Particles on the Mechanical and Machinability Behaviours of Areca Fine Fiber-Reinforced Phenol Formaldehyde Composite 添加玻璃纤维和SiC颗粒对槟榔细纤维增强酚醛复合材料力学性能和切削性能的影响
IF 0.7 4区 工程技术 Q4 Physics and Astronomy Pub Date : 2022-08-30 DOI: 10.5755/j02.mech.25443
Athijayamani Athijayamani, P. Muthusamy, Sidhardhan Susaiyappan
In the present experimental study the effects of addition of Glass Fibers (GFs) and Silicon Carbide (SiC) particles on the mechanical and machinability behaviors of Areca Fine Fiber (AFF)-reinforced Phenol Formaldehyde (PF) composites were evaluated in three stages. Composites were prepared by hand lay-up technique at room temperature. From the first stage, it is observed that the 20AFF/20GF/PF hybrid composites give better mechanical properties than the other hybrid composites followed by the 10AFF/30GF/PF hybrid composite. The results of second stage revealed that the AFF/GF/SiC/PF hybrid composites exhibited the highest values of mechanical properties after addition of the 6% of SiC particles. From third stage, it is observed that the cutting speed is most significant process parameter during drilling of the 20AFF/20GF/6SiC/PF hybrid composite, followed by feed rate.
在本实验研究中,分三个阶段评估了玻璃纤维(GFs)和碳化硅(SiC)颗粒的添加对槟榔细纤维(AFF)增强酚醛树脂(PF)复合材料力学和机械加工性能的影响。在室温下采用手工叠层技术制备了复合材料。从第一阶段开始,观察到20AFF/20GF/PF杂化复合材料比其他杂化复合材料具有更好的机械性能,其次是10AFF/30GF/PF共混复合材料。第二阶段的结果表明,添加6%的SiC颗粒后,AFF/GF/SiC/PF杂化复合材料的力学性能最高。从第三阶段开始,观察到切削速度是20AFF/20GF/6SiC/PF复合材料钻孔过程中最重要的工艺参数,其次是进给速度。
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引用次数: 0
Research on Tribological Features of Brake Friction Materials - Com-parison of the Results Obtained with the Pin-On-Disc and Ball-Cratering Methods 制动器摩擦材料摩擦学特性研究——销盘法与球磨法结果比较
IF 0.7 4区 工程技术 Q4 Physics and Astronomy Pub Date : 2022-08-30 DOI: 10.5755/j02.mech.31673
A. Borawski, D. Szpica, G. Mieczkowski
Brakes are one of the most important systems in each vehicle. For this reason, numerous studies are carried out in many scientific institutions that allow for better understanding of friction and wear phenomenon. Therefore, the correctness of the obtained results is of great importance. Hence, the choice of the research method is not without significance. In this paper, it was decided to check how the choice of the method will affect the quality of the obtained results. The chosen methods were Ball-cratering and Pin-on-disc. Six groups of samples taken from three different types of pads were tested. The pads were both brand new and used. The analysis of the results was performed using the chi-square concordance test. It was established that at the significance level of 0.95, the choice of the research method was not statistically significant. Both methods provide similar high-quality results.
刹车是每辆车中最重要的系统之一。由于这个原因,许多科学机构进行了大量的研究,以便更好地理解摩擦和磨损现象。因此,所得结果的正确性非常重要。因此,研究方法的选择并非没有意义。在本文中,决定检查方法的选择将如何影响所得结果的质量。选择球孔法和针盘法。从三种不同类型的卫生巾中抽取了六组样本进行了测试。这些垫子都是全新的,而且是用过的。采用卡方一致性检验对结果进行分析。在0.95的显著性水平下,研究方法的选择不具有统计学意义。两种方法都提供了类似的高质量结果。
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引用次数: 1
Optimization of Anti-Impact Energy Absorption Structure of Hydraulic Support 液压支架抗冲击吸能结构优化
IF 0.7 4区 工程技术 Q4 Physics and Astronomy Pub Date : 2022-08-30 DOI: 10.5755/j02.mech.32032
Qiang Zhang, Bao-Gui Li, Runxin Zhang
Rock bursts are a frequent occurrence in deep coal mining, and reducing the risk of rock bursts is necessary for the safe and efficient mining of coal. As honeycomb structures have good impact resistance, the design suggests that a honeycomb structure is adopted in the roof. A mechanical model of the hydraulic support is established, and the influence of geometric parameters on the impact resistance of the honeycomb structure is studied. Finally, the orthogonal test method was used to analyze the influence and weight of the geometric parameters on the anti-impact performance of the honeycomb structure with hydraulic leg stress and roof displacement as the evaluation indexes. This paper provides a new design idea for the research and development of an impact resistance hydraulic support in the underground coal mine, which is significant in ensuring coal mine safety.
岩爆是深部煤矿开采中的常见事故,降低岩爆风险是安全高效开采煤炭的必要条件。由于蜂窝结构具有良好的抗冲击性能,设计建议屋顶采用蜂窝结构。建立了液压支架的力学模型,研究了几何参数对蜂窝结构抗冲击性能的影响。最后,采用正交试验方法,以水工腿应力和顶板位移为评价指标,分析了几何参数对蜂窝结构抗冲击性能的影响和权重。本文为煤矿井下抗冲击液压支架的研制提供了一种新的设计思路,对保证煤矿安全具有重要意义。
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引用次数: 0
Development and Comparative Evaluation of Reduced-scale Krauss Friction Tester based on Similarity Theory 基于相似理论的克劳斯摩擦试验机研制与比较评价
IF 0.7 4区 工程技术 Q4 Physics and Astronomy Pub Date : 2022-08-30 DOI: 10.5755/j02.mech.32030
Zhenyu Wang, Jie Wang, Lining Wang, Yunhai Ma
Based on the similarity principle, the basic parameters of the reduced-scale Krauss tester were derived from the full-scale Krauss tester by using the dimensional analysis method. The main structure of the Krauss testing machine had been made, and some components and parts such as brake system, servo loading system and torque measuring system had been designed and manufactured. The same batch and molded NAO brake friction material had been rigorously evaluated on two Krauss testers following ECE R-90 procedure as per the ‘‘Economic Commission for Europe” (ECE) regulations and these parameters such as friction torque, brake pressure, friction coefficient, test temperature and time had been discussed. The results showed that the reduced-scale Krauss tester was faster response than that of the full-scale Krauss tester in the process of brake growth and brake release, the brake completion time was about 370 ms ahead of schedule. However, the full-scale Krauss tester had a slower response and the brake completion time delay was about 240 ms. During the entire test, the average coefficient of friction was closer and the relative error is 6.3%, and the maximum and minimum values of the friction coefficient appeared at the same brake sequence, test section and brake cycle. The test temperature had good linear correlation in the whole test process. The total test time for reduced-scale Krauss tester was about 4/5 of full-scale Krauss tester. In each test, if the same other conditions existed, the power cost of the reduced-scale Krauss tester is 20.79 % of the power cost of the full-scale Krauss tester when the ECE R-90 test program was executed. From the comparison of the main test indexes, the test data of the scaled Krauss test machine reflected the fluctuation and correlation of the test data of the full-scale Krauss test machine to a certain extent, providing a new test equipment for the brake friction material.
基于相似原理,利用量纲分析法,从全尺寸克劳斯试验装置中推导出缩小尺寸克劳斯试验装置的基本参数。制作了克劳斯试验机的主体结构,设计制造了制动系统、伺服加载系统和扭矩测量系统等零部件。根据“欧洲经济委员会”(ECE)规定,按照ECE R-90程序,在两台克劳斯测试机上严格评估了同一批次和成型的NAO制动摩擦材料,并讨论了摩擦扭矩、制动压力、摩擦系数、测试温度和时间等参数。结果表明,缩小尺寸的Krauss测定仪在制动增长和制动释放过程中的响应速度比全尺寸Krauss测定仪快,制动完成时间提前约370 ms。然而,全尺寸Krauss测试器的反应较慢,制动完成时间延迟约为240毫秒。在整个试验过程中,摩擦系数的平均值更接近,相对误差为6.3%,摩擦系数的最大值和最小值出现在相同的制动顺序、试验段和制动周期。试验温度在整个试验过程中具有良好的线性相关性。缩小尺寸Krauss测试仪的总测试时间约为全尺寸Krauss测试仪的4/5。在每次测试中,如果存在相同的其他条件,当ECE R-90测试程序执行时,缩小尺寸克劳斯测试仪的功率成本是全尺寸克劳斯测试仪功率成本的20.79%。从主要试验指标的对比来看,规模化克劳斯试验机的试验数据在一定程度上反映了全样机克劳斯试验机试验数据的波动性和相关性,为制动摩擦材料提供了一种新的试验设备。
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引用次数: 0
Robot Workspace Optimization based on Monte Carlo Method and Multi Island Genetic Algorithm 基于蒙特卡罗方法和多岛遗传算法的机器人工作空间优化
IF 0.7 4区 工程技术 Q4 Physics and Astronomy Pub Date : 2022-08-30 DOI: 10.5755/j02.mech.32035
Qingliang Zeng, Guangyu Zhou, Ji Shi, Yongqing Li, Yuanqiang Liu, Tianming Chen, Liang Wang
Workspace analysis is an indispensable part of robot research. The workspace volume is an important factor to measure the working ability of parallel robot. In order to maximize the workspace of parallel robot, this paper solves the workspace of robot by using Monte Carlo method, and obtains that the workspace volume is 2.142×106 mm3, which is optimized by the multi Island genetic algorithm in the global optimization algorithm. After optimization, the workspace volume increases to 8.25×106 mm3, the volume of workspace before and after optimization is increased by 3.85 times. The influence of various structural parameters of the parallel robot on the workspace volume is analyzed and studied. It is obtained that the rod length ratio of the connecting rod and the driving rod has the greatest influence on the workspace volume, followed by the ratio of the center angle of the long and short sides, and the radius of the moving platform has the least influence. Furthermore, the influence of single parameter on the workspace volume is analyzed. When other parameters remain unchanged, the maximum workspace volume can be achieved when the rod length ratio of connecting rod and driving rod is 1.25, or the ratio of center angle of long and short sides is 1.53.
工作空间分析是机器人研究中不可或缺的一部分。工作空间体积是衡量并联机器人工作能力的重要因素。为了使并联机器人的工作空间最大化,本文采用蒙特卡罗方法对机器人的工作面积进行了求解,得到工作空间体积为2.142×106mm3,并采用全局优化算法中的多岛遗传算法进行了优化。优化后,工作空间体积增加到8.25×106mm3,优化前后的工作空间体积提高了3.85倍。分析研究了并联机器人的各种结构参数对工作空间体积的影响。结果表明,连杆和驱动杆的杆长比对工作空间体积的影响最大,其次是长边和短边的中心角比,移动平台的半径影响最小。此外,还分析了单个参数对工作空间体积的影响。在其他参数不变的情况下,当连杆与驱动杆的杆长比为1.25,或长边与短边的中心角比为1.53时,可以获得最大工作空间体积。
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引用次数: 1
Analysis of the Wall Force on the Bubble Collapse of the Benzamide Based on Molecular Dynamics Simulation 基于分子动力学模拟的苯甲酰胺气泡崩塌的壁力分析
IF 0.7 4区 工程技术 Q4 Physics and Astronomy Pub Date : 2022-08-30 DOI: 10.5755/j02.mech.29875
Wei Xu, Xiuli Wang, Jinhua Liu, Yuanyuan Zhao, Guohui Zhao, Wenzhuo Guo
The cavitation damage of the pollutant wall caused by shock wave and microjet in the process of bubble collapse has attracted widespread attention from scholars. However, many researches focus on bubble collapse from the macroscopic experimental point of view, the dynamics of which is still not clear. In this paper, it constructs bubbles with different radii, runs different models under different compressive strain rates, takes the pressure on the upper and lower walls of pollutants as the research target, and summarizes the influence of compressive strain rates, initial radius of bubbles and temperatures on the release pressure of bubble collapse on the pollutant wall. The results show that: as the initial radius of bubbles increase, the maximum pressure on the upper and lower walls of benzamide increases first and then decreases. The pressure release rate of bubble increases with the increase of the compressive strain rate. Based on the pressure on the upper and lower wall surfaces of the benzamide, the temperature and initial radius of the bubble have a large influence, and the influence of the compressive strain rate is small. Under the simulation conditions of the paper, when bubble collapse is used to release energy to treat pollutants, the recommended bubble radius is 10-15 Å. The paper not only reveals the influence of the initial radius of the bubble, the compressive strain rate and the temperature on the pressure released by the bubble collapse on the pollutant wall, but also provides theoretical guidance for the application of cavitation.
气泡坍塌过程中冲击波和微射流对污染物壁的空化损伤引起了学者们的广泛关注。然而,许多研究都是从宏观实验的角度对气泡坍塌进行的,其动力学尚不清楚。本文构造了不同半径的气泡,在不同的压缩应变率下运行不同的模型,以污染物上下壁的压力为研究目标,总结了压缩应变率、气泡初始半径和温度对气泡坍塌对污染物壁释放压力的影响。结果表明:随着初始气泡半径的增大,苯甲酰胺上下壁的最大压力先增大后减小。气泡的压力释放速率随着压缩应变速率的增加而增加。基于苯甲酰胺上下壁面的压力,气泡的温度和初始半径影响较大,压缩应变速率的影响较小。在论文的模拟条件下,当利用气泡坍塌释放能量处理污染物时,建议的气泡半径为10-15Å。本文不仅揭示了气泡初始半径、压缩应变速率和温度对气泡坍塌对污染物壁释放压力的影响,而且为空化的应用提供了理论指导。
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引用次数: 0
A New Shear Locking-Free Quadrilateral Plate Element for Free Vibra-tion and Eigen-Buckling Analysis 一种用于自由振动和特征屈曲分析的新型剪切锁定自由四边形板单元
IF 0.7 4区 工程技术 Q4 Physics and Astronomy Pub Date : 2022-08-30 DOI: 10.5755/j02.mech.30331
Wei XiaXIANGng, Z. Yao, Lina He
A new plate element has been formulated by simply adding one degree of freedom for each node on the basis of the classical ACM element, based on a modified first-order shear deformation plate theory, which assumes that the plate deflection has bending and shearing components, with two rotations defined by differentiations of bending deflections. This new element, with 16 degrees of freedom, exhibits no locking effect, and is appropriate for both thin and thick plates. To assess the performance of the newly developed plate element, it has been applied to the prediction of natural frequencies and critical bucking loads of square plates with various thickness ratios and boundary conditions. Comparisons with available analytical and numerical solutions in open publication show that the new element leads to highly accurate solutions in free vibration and eigen-buckling analysis with good convergence, and can be competitive with existing plate elements.
在经典ACM单元的基础上,基于修正的一阶剪切变形板理论,假设板挠度具有弯曲和剪切分量,并通过弯曲挠度的微分定义两个旋转,通过简单地为每个节点增加一个自由度,从而建立了一个新的板单元。这种新元件具有16个自由度,无锁紧效应,适用于薄板和厚板。为了评估新开发的板单元的性能,将其应用于不同厚度比和边界条件下方形板的固有频率和临界屈曲载荷的预测。与已有的解析解和数值解的比较表明,新单元在自由振动和本征屈曲分析中具有较高的精度和较好的收敛性,可以与现有的板单元相媲美。
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引用次数: 0
Profile Design and Performance Research of Hydrogen Circulation Pump in Fuel Cell System 燃料电池系统氢循环泵外形设计及性能研究
IF 0.7 4区 工程技术 Q4 Physics and Astronomy Pub Date : 2022-08-30 DOI: 10.5755/j02.mech.31528
Huanle Zhai, Wei Li, Leilei Ji, M. Awais, Jiwei Li, Shuo Li
A general design formula for rotor profile is proposed based on conjugation theory and feasibly verified by using the four different design shapes. The overset mesh method and the realizable k-ε two-layer turbulence model are used for simulation calculation. The results stated that the average volume flow error of hydrogen medium and air medium is small, so an alternative experimental study has been carried out. By building a test system for experimental verification, it is found that the error between the simulation results and the experimental results is small at the low-pressure ratio and increases at the high-pressure ratio because the influence of the ambient temperature is not considered. The results further verified the reliability using the simulation calculation method. At last, the fluid characteristics of the two-tangent-arcs type, single-arc type, ellipse type, and quadratic-curve type rotors are evaluated. The result shows that the comprehensive performance of the single-arc type rotor is superlative as followed by the ellipse type rotor. However, the quadratic-curve rotor has the largest average flow but the worst flow stability and the two-tangent-arcs rotor shows the smallest average flow.
基于共轭理论,提出了转子型线的通用设计公式,并用四种不同的设计型线进行了可行性验证。采用复盖网格法和可实现的k-ε双层湍流模型进行仿真计算。结果表明,氢气介质和空气介质的平均体积流动误差较小,因此进行了替代实验研究。通过搭建测试系统进行实验验证,发现在低压比下,仿真结果与实验结果的误差较小,在高压比下,由于不考虑环境温度的影响,仿真结果与实验结果的误差增大。结果进一步验证了仿真计算方法的可靠性。最后,对两切弧型、单弧型、椭圆型和二次曲线型转子的流体特性进行了评价。结果表明,单圆弧型转子综合性能最好,其次是椭圆型转子。二次曲线转子的平均流量最大,但流动稳定性最差,两切弧转子的平均流量最小。
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引用次数: 3
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Mechanika
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