Self‐Toughening and Self‐Reinforcing Injection‐Molded Isotactic Polypropylene via Midfrequency Vibration Field

The effect of vibration frequency on the mechanical properties of general grade polypropylene (PP) prepared by two types of vibration injection molding (VIM) was investigated. With the application of vibration injection molding, the mechanical properties of isotactic PP are improved. The yield strength was upgraded with the increment of vibration frequency and a peak occurs at a particular frequency for each VIM. The elongation at break was also raised by increased vibration frequency, and the vibration frequency also improves impact strength. Self‐reinforcing and self‐toughening polypropylene molded parts were found at high vibration frequency. The wide angle X‐ray diffraction (WAXD) curves and scanning electronic micrograph (SEM) micrographs have shown that, in the vibration field, the enhancement of mechanical properties can be attributed to the occurrence of a γ‐phase crystalline structure and a more pronounced elongation in shape than obtained by conventional injection moldings. In addition, smaller crystals of the β‐phase crystal form improve toughness.     

Rational Profiling of Reinforced Rotating Disks

The problem of rational profiling of thermoelastic three-layered reinforced rotating disks of gas turbines is formulated. The conditions of equal-stressed reinforcement of the midlayer and the condition of equal-strength binder of the reinforced layer or external isotropic layers are used as criteria for rational designing. An iterative method is proposed for solving such problems. The problem of rational profiling of disks with radial and radially circumferential reinforcements, on condition that the fibers of the radial family are equally stressed, is solved analytically. The calculation results for B-Al and B-Ti disks, obtained by using both the criteria of rational design, are given for plane-parallel and 3D reinforcements. It is shown that, at an equal load-carrying capacity, the weight of such disks can be 30-60% smaller than that of reinforced disks of constant thickness, or, at an equal weight, they can have a considerably higher load-carrying capacity. The criterion of equal-stressed reinforcement, as a rule, is more efficient than the condition of equal-strength binder.     

Stability and initial postbuckling behavior of anisotropic cylindrical shells under external pressure

A solution is obtained to describe the stability and initial postbuckling behavior of cylindrical shells made of composites with one plane of symmetry. The solution is based on the Donnell-Mushtari-Vlasov nonlinear theory of anisotropic shells and Koiter’s theory of buckling and postbuckling behavior. Calculated results are presented for boron plastic shells with reinforcement of different types under external pressure. It is shown that the conventional model of a composite as an orthotropic material is erroneous for many types of reinforcement __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 3, pp. 86–103, March 2007.     

Recent progress in electrospun nanofibers: Reinforcement effect and mechanical performance

Composite materials are becoming increasingly important as structural materials for aeronautical and space engineering, naval, automotive, and civil engineering, sporting goods, and other consumer products. Fiber‐based reinforcement represents one of the most effective manufacturing strategies for enhancing the mechanical strength and other properties of composite materials. Electrospinning has gained widespread interest in the last two decades because of its ability to fabricate continuous ultrafine nanofibers with unique characteristics. The impact of electrospinning on fiber synthesis and processing, characterization, and applications in drug delivery, nanofiltration, tissue scaffolding, and electronics has been extensively studied in the past. In this article, the authors have focused on a comprehensive review of the mechanical performance and properties of electrospun nanofibers as potential reinforcements as well as their advanced nanocomposites. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1171–1212     

Ni-W-Co/SiC复合材料磨损特性与磨损机制

研究了ＳｉＣ颗粒和ＳｉＣ晶须为复合第二相的Ｎｉ－Ｗ－Ｃｏ合金基复合材料的磨损特性和磨损机制．结果表明,复合相含量、几何特性及载荷和滑动速度对复合材料的耐磨性影响很大．其原因在于ＳｉＣ颗粒与ＳｉＣ晶须以不同的形式发生流失．     

含筋率和弹着点对钢筋混凝土抗侵彻性能的影响

阐述了侵彻钢筋混凝土几种常用的建模方法,选用AUTODYN中的Lagrange算法,对已有的动能弹侵彻钢筋混凝土问题进行了计算,计算结果与试验数据符合较好。使用此方法,分析了含筋率和配筋方式对钢筋混凝土靶抗侵彻性能的影响,以及弹着点对动能弹侵彻性能的影响。研究表明,钢筋越粗或者钢筋编织越密,即含筋率越高,钢筋混凝土靶板的抗侵彻能力越强,尤其对于动能弹直径大于靶板中钢筋间距的情况,效果明显;另外,弹着点对动能弹侵彻能力有较大影响。 更多还原     

锈胀开裂后变形钢筋与混凝土粘结性能实验研究

为研究锈胀开裂对变形钢筋与混凝土间粘结性能的影响,开展了电化学快速锈蚀内贴应变片钢筋混凝土试件的拔出实验,得到了不同位置处钢筋的应变,进而推导了钢筋与混凝土不同位置处的粘结应力,分析了锈胀裂缝宽度对钢筋与混凝土间不同位置处粘结应力的影响。实验研究表明:粘结试件中的钢筋应变对锈胀裂缝宽度的敏感性大;对于锈胀裂缝较小的试件,其粘结应力峰值接近加载端,而对于锈胀裂缝较大的试件,粘结应力峰值更靠近自由端。     

Viscoplastic deformation of reinforced plates with varying thickness under explosive loads

The problem of viscoplastic bending of reinforced plates with varying thickness is formulated. An original method for the integration of this initial-boundary-value problem is developed. The numerical solution is compared with an analytical solution obtained with a rigid-plastic model of an isotropic circular plate. The efficiency of the method is demonstrated by analyzing the inelastic dynamics of reinforced plates with constant and varying thickness. It is shown that the maximum residual deflections of plates can be reduced severalfold by means of rational profiling and reinforcement __________ Translated from Prikladnaya Mekhanika, Vol. 44, No. 2, pp. 85–98, February 2008.     

爆炸载荷下RC单向简支板的能量法优化设计

由钢筋混凝土(RC)板的抗力-位移(R-y)曲线特性可知,曲线下方面积代表板在爆炸载荷作用下可能吸收的能量. 对爆炸载荷作用下RC板的R-y曲线采用双折线模型,计算不同配筋率的R-y曲线下方面积,面积最大时的配筋率即可定义为相应设计的最佳配筋率.考虑材料非线性及高应变率对混凝土和钢筋强度的影响,采用分层法迭代求解抗力-挠度(R-y)曲线. 研究结果可供受爆炸载荷的RC板优化设计借鉴.     

腹筋对连续深梁剪切破坏影响的有限元分析

我国现行混凝土结构设计规范关于腹筋对深梁抗剪承载力影响的考虑,主要基于简支深梁的试验数据和计算模型,相关规定对于连续深梁的适用性有待验证。腹筋对连续深梁抗剪性能的影响机理十分复杂,系统的试验研究较少,试验结果比较分散。为了弥补试验研究的不足,采用非线性有限元方法模拟钢筋混凝土连续深梁的受力性能。利用已有的试验数据,验证了基于ATENA软件建立的有限元模型,并以此为基础,对以腹筋配筋率和剪跨比为变量的64根连续深梁进行分析,研究腹筋对连续深梁受剪承载力的影响。有限元分析结果与规范公式和压杆-拉杆模型(STM)及最新提出的三参数机动法(3PKT)的比较表明,中国规范高估了水平腹筋对构件受剪承载力的贡献,STM和3PKT方法也存在各自的不足。