X型方钢管节点平面内受弯性能研究

为考察X型方钢管节点在平面内弯矩作用下的静力性能,通过ABAQUS进行建模及非线性有限元计算,结合验证性试验,对节点的破坏模式、应变强度发展过程、极限承载力进行研究,并讨论轴力和平面内弯矩联合作用对节点极限承载力的影响．结果表明：节点在平面内弯矩作用下,发生弦杆受拉侧鼓凸,受压侧凹陷,腹杆受拉侧焊缝被拉开;节点弦杆最先进入塑性,最终由于塑性变形过大而导致试件破坏;试件极限承载力随着届值的增大而增大;在轴力和平面内弯矩联合作用下,节点的受弯极限承载下降．     

造纸机用铸铁烘缸缸体设计计算的探讨

对于烘缸缸体的设计计算,过去是按内压作用下的圆柱壳计算,为考虑其他载荷影响引入一个修正系数.但是这样做忽略了不同烘缸尺寸及不同荷载工作条件下的应力状态.分析了烘缸缸体设计过程中,不同的荷载作用下的应力计算方法,并给出了综合应力计算公式,该公式可用于烘缸缸体设计计算.     

复合载荷下周向裂纹厚壁圆筒的极限载荷研究

根据Mises屈服准则在中性轴假设,周向、径向应力常数假设条件下,推导出了含等深周向裂纹厚壁圆筒在受内压、轴向力和弯矩复合载荷下的近似极限载荷公式。对典型参数下理想弹塑性材料模型进行了有限元分析,有限元验证表明文中建立的模型是偏保守的。1.32≤k≤2.00时推荐了计算厚壁圆筒极限载荷的周向、径向应力的取值。     

高压断路器壳体应力分析

以高压断路器壳体为研究对象,运用应变电测方法在壳体的关键部位贴应变片,进行最高测试压力为4 MPa的常温水压实验,测试关键部位应力分布情况.通过ANSYS 10.0建立相同尺寸壳体的计算模型,研究壳体在0.8 MPa工作压力下沿0°内截面、90°外截面和壳体相贯线截面的应力分布状态,并与实验结果进行比较.结果表明,用ANSYS 10.0分析壳体的应力分布可行,壳体0°截面的最大应力出现在肩部的内壁,为圆筒薄膜应力的2倍;壳体的最大应力为圆筒薄膜应力的3倍.     

Ф3660铸铁烘缸疲劳分析

对Ф3660烘缸在线压载荷作用下的受力做了有限元应力计算,获得了该烘缸在动静载荷作用下最大平均应力和交变应力幅,并在分析灰口铸铁烘缸疲劳特性的基础上对该烘缸进行了疲劳分析.     

曲轴假缺陷磁痕现象探讨

曲轴是内燃机中重要的零件,它的作用是输出内燃机扭矩并驱动内燃机自身的辅助运动机构.在工作过程中,曲轴受到内燃机燃气压力和机件运动的惯性力及力矩(扭矩和弯矩),及摩擦阻力、摩擦阻力矩和对外输出功率时的阻力矩的作用,在这些周期性变化载荷的作用下,曲轴各部分产生弯曲,扭转、拉压、冲击等复杂交变的应力和变形,同时在高速条件下工作,也造成曲轴自身扭转振动和弯曲振动,而引起附加交变的应力与变形的产生.     

含未焊透缺陷工业管道的强度分析与安全评定

文章采用分析设计方法对2条被《在用工业管道定期检验规程》定级为4级的含未焊透缺陷判废工业管道进行了有限元强度数值计算,同时,利用基于内压／弯矩／扭矩复杂载荷作用下的含未焊透缺陷压力管道安全评定方法对其进行了安全评价。通过强度校核和安全评定结果表明：在低应力情况下,上述4级未焊透缺陷不影响管道的安全运行,指出了《在用压力管道定期检验规程》安全状况等级划分方法的保守性,对于最大限度地发挥在用工业管道的使用效能、提高安全监管的科学性和有效性具有重要意义。图11表7参8     

外压斜锥壳设计方法的研究

GB150中规定,当外压锥壳为偏心锥壳时,参照正锥壳的设计计算方法.在对此方法研究分析后发现,等效后的正锥壳承压能力要比实际的斜锥壳降低很多,从而造成斜锥的设计壁厚偏大.文中运用ANSYS软件,首先对圆筒和正锥壳进行屈曲分析,与理论计算方法得出的临界压力值对比,证明有限元方法得出的临界压力值与理论计算相符;然后对外压斜锥壳进行分析,找到一种与外压斜锥承压能力相接近的正锥,即斜锥等同不同锥角的正锥.等效后的正锥与原来斜锥的承压能力相近,从而对原有的斜锥壳设计方法加以改进.     

含凹陷海底管道安全评价与屈曲机理研究现状

凹陷是海底管道受到外部挤压或碰撞而产生的几何缺陷,是造成海底管道失效的主要原因之一。为了提供一定的海底管道设计、制造、安装及运行监测的参考依据,文中从安全评价方法与屈曲机理两方面总结了近年来国内外的研究进展,阐述了基于深度和应变模型的纯凹陷和含其它缺陷凹陷的评估方法,介绍了含凹陷海底管道在纯外压、纯弯矩和内压+弯矩载荷作用下的屈曲机理研究现状。在此基础上,提出目前研究还不够全面,并指出可以考虑基于应变、应力的双重准则和其他缺陷的具体影响,以及国内安全性评价准则建立的必要性;同时提出多种载荷作用下的屈曲机理研究是今后发展的趋势。     

φ3660铸铁烘缸疲劳分析

对φ3660烘缸在线压载荷作用下的受力做了有限元应力计算，获得了该烘缸在动静载荷作用下最大平均应力和交变应力幅，并在分析灰口铸铁烘缸疲劳特性的基础上对该烘缸进行了疲劳分析。     

从力学性质测试与感官鉴定分析加热方式对马铃薯组织结构的影响

马铃薯片分别以沸水、蒸汽和微波三种方式加热一段时间后,测其中心温度,并经力学性质测试和感官鉴定两种方法对其组织结构变化进行评价。实验发现不论哪种加热方式,两种评价结果都存在着相互对应的关系;薯片组织结构变化的程度,并不完全取决于加热后食品中心达到的温度,而主要与加热方式和加热速率有关。     

Effect of adhesive type and glue-line thickness on the fatigue strength of mortise and tenon furniture joints

The fatigue strength of rectangular mortise and tenon rubberwood furniture joints made from polyvinyl-acetate (PVAc) and urea-formaldehyde (UF) adhesives were compared. The results showed that the allowable design stress for PVAc adhesive joints could be set at 30 % of its ultimate bending moment as compared to 25 % for the UF adhesive joint. Further, PVAc adhesive joints have large working tolerances for glue-line thicknesses which make it suitable for mass production furniture manufacturing.     

三维编织复合材料缝合连接设计及破坏机制

 针对三维编织复合材料的缝合连接设计问题,在研究制造工艺基础上,建立缝合连接的强度校核和参数设计公式,绘制连接部件的内力响应。对不同搭接长度和缝合密度的三维编织缝合连接复合材料试件进行拉伸试验,发现缝合连接接头主要发生3种形式的破坏:在搭接的一端或两端整体断裂;搭接缝合区分层断裂;缝合区中部分分层、部分整体断裂。机制分析表明,断裂模式主要受缝合参数的影响,也与内力分配和是否存在应力集中有关,实际应用中可以根据情况采用不同的连接形式。     

An investigation into the reaction behavior of tubular braids due to internal pressure

Braiding has many applications in different industries as an internal pressurized cylinder. In these conditions, a sustainable structure without any wrinkling and unevenness is quite necessary. Using thin wall structures with closed ends and under internal pressures as a braid is addressed in the present study. With the use of a silicon vessel as the core, the braids with different angles and weavings were produced. They were exposed to internal pressure from zero to failure point. All stages of change in the shapes of the samples were recorded by a camera and the pressure–diameter results were extracted in 10 s once. In this research, the authors elaborate on the theory of stress and wrinkling moment created in these braids under internal pressure, and then they develop a new testing method by which they compare the obtained results with the theory. Following that, the relationship between the angle and failure pressure is investigated to determine the best braid angle in braiding used as thin wall structures. In the braid angle of ± 55°, all the forces created in braid due to internal pressure are along with strands direction and the increase in the cylinder diameter of the braid has been completely controlled depending on strands’ elongation. The rate of diameter increase in the angles of less than ± 55° is fast, especially in pressures close to failure pressure. However, in the bigger angles, the elongation or, in other words, the diameter decrease is observed in braiding.     

接触状态下男上装基础版型对人体压力分布的有限元模型

为对男上装基础版型与人体接触状态下的压力分布进行仿真与分析,采用三维人体测量技术获取人体和服装的点云数据,通过逆向工程软件建立人体与服装的几何模型,运用有限元软件进行有限元网格划分,建立人体与服装在接触状态下的有限元模型并进行仿真计算。由仿真结果得出基础版型与人体之间的压力及位移的分布状况：肩部中点的压力值为2.012 ～4.134 kPa,胸点与背部点压力值为0 ～ 1.101 kPa,肩颈点与肩点压力值为0 ～2.012 kPa;而实测肩部中点压力值为3.14 ～ 3.20 kPa,胸点压力值为0.73 ～ 0.81 kPa,肩颈点压力值为0.54 ～0.61 kPa,肩点压力值为1.19 ～1.23 kPa,背部点压力值为0.61 ～0.75 kPa;经对比实验验证所建立的有限元模型是合理且有效的。     

自动清洗强化斜齿扭带的工程应用研究

自动清洗强化斜齿扭带，其原理是在扭带表面上按一定规律排列不对称斜齿，使被导向的传热流体对扭带的不对称反作用力形成一个旋转力矩。解决了现有的塑料扭带不能用于低流速传热设备的自动清洗问题。试验结果表明，与现有光滑扭带相比，斜齿型扭带自转清洗力矩增大了2倍多、传热系数平均提高了30％，即使6m长传热管、4管程的传热设备的阻力也只有0．15MPa左右，仍然在一般的工程许可的范围内，具有广阔的应用前景。     

Numerical simulation of stress distribution in heterogeneous solids during high pressure processing

It is generally assumed that the internal stress distribution in foods under high pressure processing (HPP) is uniform, which may not be true for solid foods with hard inclusions, like meats with bones or for particulate foods. Our objective was to simulate the internal stress distribution during HPP of a model heterogeneous solid food made with a gel and a wood inclusion and determine how mechanical properties affect the internal stress distribution. It was determined that hydrostatic pressure decreased and shear stress was generated at the interface between the soft solid and the hard inclusion. The differences in pressure and shear stresses increased as the shear modulus of the soft solid increased. Our studies suggest that a better understanding of the mechanical properties that affect the development of the internal stress field is needed, since they could affect the achieved microbial inactivation levels at different locations in HPP solid foods.     

High pressure/thermal treatment effects on the texture of beef muscle

The effects of high pressure (to 800 MPa) applied at different temperatures (20-70 °C) for 20 min on beef post-rigor longissimus dorsi texture were studied. Texture profile analysis showed that when heated at ambient pressure there was the expected increase in hardness with increasing temperature and when pressure was applied at room temperature there was again the expected increase in hardness with increasing pressure. Similar results to those found at ambient temperature were found when pressure was applied at 40 °C. However, at higher temperatures, 60 and 70 °C it was found that pressures of 200 MPa caused large and significant decreases in hardness. The results found for hardness were mirrored by those for gumminess and chewiness. To further understand the changes in texture observed, intact beef longissimus dorsi samples and extracted myofibrils were both subjected to differential scanning calorimetry after being subjected to the same pressure/temperature regimes. As expected collagen was reasonably inert to pressure and only at temperatures of 60-70 °C was it denatured/unfolded. However, myosin was relatively easily unfolded by both pressure and temperature and when pressure denatured a new and modified structure was formed of low thermal stability. Although this new structure had low thermal stability at ambient pressure it still formed in both the meat and myofibrils when pressure was applied at 60 °C. It seems unlikely that structurally induced changes can be a major cause of the significant loss of hardness observed when beef is treated at high temperature (60-70 °C) and 200 MPa and it is suggested that accelerated proteolysis under these conditions is the major cause.