Effect of PyC interface phase on the cyclic ablation resistance and flexural properties of two-dimensional Cf/HfC composites

Composites based on hafnium carbide and reinforced with continuous naked carbon fiber with and without PyC interface were prepared at low temperature by precursor infiltration and pyrolysis and chemical vapor deposition method. The microstructure, mechanical property, cyclic ablation and fiber bundle push-in tests of the composites were investigated. The results show that after three times ablation cycles, the bending strength of samples without PyC interface decreased by 63.6 %; the bending strength of samples with PyC interface only decreased by 37.8 %. The force displacement curve of the samples with PyC interface presented a well pseudoplastic deformation state. The mechanical behavior difference of two kinds of composites was due to crucial function of PyC interface phase including protection of fiber and weakening of fiber/matrix interface.     

Additive manufacturing of zirconia ceramics by material jetting

The possibility of additive manufacturing of ceramics has been reported widely in scientific literature. This study investigates the potential of direct inkjet printing or material jetting of 3Y-TZP ceramics by assessing the microstructure and mechanical properties of the sintered printed parts. The technique allows to print in layers of 10.5 μm, with an as-printed green density of 58 % and nearly fully sintered density of 6.03 ± 0.1 g/cm³ (99.7 % TD). The dimensions of the green and sintered parts were highly accurate but showed an anisotropic roughness in function of the building direction, mainly due to the support structures. The biaxial bending and 4-point bending strength of the sintered material was found to be substantially higher in the XY direction than in the building (Z) direction. SEM and X-Ray computed tomography revealed the presence of delamination cracks, agglomerates and spherical pores, which were identified as fracture origins on fractured surfaces.     

沥青混凝土小梁弯曲断裂的数值模拟

应用有限元软件RFPA,建立不同级配的混合料模型,模拟沥青混凝土小梁的抗弯拉性能,并实现了对材料变形、微破裂到宏观破坏全过程模拟。通过研究不同级配混合料的弯曲断裂,对沥青混凝土小梁裂缝的形成过程及其走向有了更深入的认识。结果表明,数值模拟是研究沥青混合料性能试验的有效手段,通过模拟得知,骨架密实型的沥青混凝土抵抗变形能力最好;产生的裂缝全为绕集料扩展。     

简析圆形断面材料在矫直过程中的弹塑性弯曲变形

圆形断面材料,尤其是薄壁管,在矫直过程中经常出现压扁和压纹现象,本文就矫直过程中的圆形断面睦成一个连续弯曲的梁,精确给出了反弯矫直过程中试件的曲率、弯矩、变莆能、挠度以及压扁率与塑性层深度系数的关系,说明试件在矫直机上进行弹塑性弯曲矫直时,塑性层深度系数的造字以是矫直得以顺利进行,并最终实现矫直的关键,为矫直机的改造与发展指明了方向。     

M401主减速机齿轮故障分析处理

文章对M401挤压造粒机组主减速机齿轮故障原因进行了分析,阐述了故障修复具体措施的实施情况与原理,并应用齿轮强度理论对主减速机调速齿轮进行了强度校核。通过该机组修复后的运行实践,说明了修复方案是可行的。     

均布压力作用下厚壁圆管弯矩计算方法的探讨

建立了厚壁圆管弯矩计算公式，通过分析的均布压力作用下厚壁圆管与薄壁圆管压力相对误差，给出了厚壁圆管与薄壁圆管分类原则，了解和掌握这一原则对工程师大有禅益。     

Analysis of rectangular laminated composite plates via FSDT meshless method

A meshless approach based on the reproducing kernel particle method is developed for the flexural, free vibration and buckling analysis of laminated composite plates. In this approach, the first-order shear deformation theory (FSDT) is employed and the displacement shape functions are constructed using the reproducing kernel approximation satisfying the consistency conditions. The essential boundary conditions are enforced by a singular kernel method. Numerical examples involving various boundary conditions are solved to demonstrate the validity of the proposed method. Comparison of results with the exact and other known solutions in the literature suggests that the meshless approach yields an effective solution method for laminated composite plates.     

折剪机床设计及关键零件的有限元分析

介绍了在小型折弯、剪切两用机床设计：干发中，采用了连杆增力机构和齿轮同步机构，实现了在小缸径单杆液压缸驱动下的增力和滑块运动的同步性。在SolidWorks中建立零件的三维模型，用COSMOSXpress对关键零件进行有限元分析，并根据分析结果优化了零件结构。     

Modulus of elasticity and yield bending stress of coating lubrotec 19985 produced by the metal spraying process

Round bars of 13.6 mm diameter made from low alloy steel were sprayed by hard-coating Lubrotec 19985 under the following spraying parameters: the rotation speed varied from 500 to 900 rpm, the feeding speed from 0.1 to 1.0 mm/rev, and the nozzle tip distance from 100 to 200 mm; the sprayed bars were then subjected to bending test. Depending on the thickness of the produced coating, the modulus of elasticity and yield bending stress of the coating were calculated by applying the bending deflection formula and an equivalent cross-sectional area technique, respectively. The results obtained indicated that the thickness, hardness, yield bending stress, and modulus of the elasticity of coating were varied with the variation in spraying parameters. The optimum spraying parameter was a rotation speed of 700 r.p.m, a nozzle tip distance of 200 mm, and a feed rate of 0.1 mm/rev. This optimum parameter produced an acceptable thickness of 1.14 mm, a hardness of 148 HV, a bending stress of 404.9 MPa, and a modulus of elasticity of 91.47 GPa. The results obtained can also help determine the modulus of elasticity and yield bending stress of the various coating materials when a coated round bar is subjected to the bending test. This paper was recommended for publication in revised form by Associate Editor Youngseog Lee Nabil B. Sada was awarded the B.Sc. degree in Mechanical Engineering in 1969, from Baghdad University, Iraq, and Ph.D. degree in Mechanical Engineering in 1980, from Queen’s University of Belfast, United Kingdom. From 1981 to 1989, Dr. Nabil was a Researcher and Lecturer at State Enterprise for Mechanical Industries, and at the Department of Mechanical Engineering at Al-Mostansyria University in Iraq. From 1994 to 1998, he was a Professor at Department of Mechanical Engineering, Al-Tahadi University, Libya. From 1999 to 2008, he was a Professor at the Department of Mechanical Engineering at Al-Balqa’ Applied University, and at Tafila Technical University, Jordan. Currently, he is a researcher in Canada. Mohammed Al-Nawafleh received his B.S. and M.S degrees in Mechanical Engineering from Leningrad Ins-titute of Textile and Light Industry in 1989. He then received his Ph.D. degree from Sankt-Petersburg State University of Technology and Design, Russia in 1993. From 1997 to 2005, Dr. Nawafleh was a Professor at the Department of Mechanical Engineering at Al-Balqa’ Applied University in Jordan. From 2005 to 2008, he was a Professor at the Department of Mechanical Engineering at Tafila Technical University. Currently, he is a Professor at the Department of Civil Engineering at Al-Hussein Bin Talal University, Jordan.