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141.
《工程(英文)》2017,3(6):806-816
The synergistic use of partially encased concrete and composite girders with corrugated steel webs (CGCSWs) has been proposed to avoid the buckling of corrugated steel webs and compression steel flanges under large combined shear force and bending moment in the hogging area. First, model tests were carried out on two specimens with different shear spans to investigate the mechanical behavior, including the load-carrying capacity, failure modes, flexural and shear stress distribution, and development of concrete cracking. Experimental results show that the interaction of shear force and bending moment causes the failure of specimens. The bending-to-shear ratio does not affect the shear stiffness of a composite girder in the elastic stage when concrete cracking does not exist, but significantly influences the shear stiffness after concrete cracking. In addition, composite sections in the elastic stage satisfy the assumption of the plane section under combined shear force and bending moment. However, after concrete cracking in the tension field, the normal stresses of a corrugated web in the tension area become small due to the “accordion effect,” with almost zero stress at the flat panels but recognizable stress at the inclined panels. Second, three-dimensional finite-element (FE) models considering material and geometric nonlinearity were built and validated by experiments, and parametric analyses were conducted on composite girders with different lengths and heights to determine their load-carrying capacity when subjected to combined loads. Finally, an interaction formula with respect to shear and flexural strength is offered on the basis of experimental and numerical results in order to evaluate the load-carrying capacity of such composite structures, thereby providing a reference for the design of partially encased composite girders with corrugated steel webs (PECGCSWs) under combined flexural and shear loads. 相似文献
142.
以碳纤维和铜纤维为原料制备了三维四层深交联机织物,并将酚醛树脂和其他填料组成树脂体系,然后将二者进行复合成型,制成三维深交联摩擦材料。通过改变织物纬向的铜纤维含量及位置获得四种深交联机织摩擦材料,探究不同位置和含量的铜纤维对摩擦材料纬向弯曲性能的影响。结果表明:摩擦材料的弯曲性能随着铜纤维含量的增加而减小;当铜纤维处在摩擦材料预制体中间层时,会降低复合材料的弯曲性能。材料的破坏模式具体表现为树脂基体的碎裂,以及纤维的抽拔及断裂。 相似文献
143.
铝合金异形截面管件是实现汽车结构轻量化的有效途径之一,其成形工艺是先将铝合金管材经过数控弯曲获得轴线形状,然后进行内高压成形。弯曲产生的回弹、截面畸变及起皱等缺陷会影响后续内高压成形的质量。本工作通过建立管材塑性弯曲的理论模型和材料模型,计算任意弯曲角度的卸载回弹量,在弯曲过程考虑回弹量补偿,有效避免了内高压成形时的咬边缺陷。通过改善芯轴条件,使用带有一个芯球的芯轴,使截面不圆度由7.55%降低至1.43%,避免了弯曲件在内高压成形时发生破裂。同时对弯曲产生皱纹的管件进行内高压成形,证实了内高压成形过程不能够消除管件在弯曲过程形成的起皱。通过工艺实验研制出6063铝合金异形截面管件,获得了无缺陷的成形件。对47个内高压成形件进行尺寸精度测量,最大尺寸偏差为1.08mm(1.63%),尺寸和精度符合设计要求。 相似文献
144.
对玻璃纤维增强环氧乙烯基酯树脂基复合材料在温湿环境下进行了人工紫外加速老化实验,并进行了拉伸、弯曲等试验,分析了试件紫外老化后的质量损失率、巴氏硬度、弯曲破坏形态以及力学性能的演变规律,并利用SEM观察了试样表面老化前后的形貌变化.研究表明:紫外线照射后试样的表面泛黄,且随照射时间的延长颜色不断加深;试样拉伸和弯曲性能以及巴氏硬度在紫外老化前期有所上升,160 h后开始下降;质量损失率随着紫外光照射时间的延长而逐渐增大;紫外老化后试件的弯曲破坏过程与未老化试件一致;随着老化周期的增加,孔隙量和韧性发白光带数量增加,呈现出明显的片层状海浪花样. 相似文献
145.
《Mauerwerk》2018,22(3):162-174
This paper deals with the design of basement walls subjected to lateral earth pressure. The current simplified calculation method according to DIN EN 1996‐3/NA only covers active earth pressure, which is the lower limiting value of the earth pressure. Designing according to DIN EN 1996‐1‐1/NA, higher coefficients of earth pressure (like earth pressure at rest) can be considered, with an additional verification of the shear resistance being necessary. This paper presents a theoretical model, which forms the basis for an analytical derivation of the loadbearing capacity, and explains the required minimum values of the acting normal force to ensure sufficient resistance to cover bending and shear. Based on these results, a simplified equation is proposed for the determination of the required minimum normal force, based on the design according to DIN EN 1996‐3/NA and providing identical values in case of an earth pressure coefficient of 1/3. The required minimum load resulting from this approach fulfils the described requirement to cover bending and shear. The presented solution is verified and the conditions for application are defined. Finally, the minimum required normal forces are evaluated and tabulated for common cases relevant to building practice. 相似文献
146.
Alfonso Sepúlveda Jan Speulmanns Philippe M. Vereecken 《Science and Technology of Advanced Materials》2018,19(1):454-464
The growing demand of flexible electronic devices is increasing the requirements of their power sources. The effect of bending in thin-film batteries is still not well understood. Here, we successfully developed a high active area flexible all-solid-state battery as a model system that consists of thin-film layers of Li4Ti5O12, LiPON, and Lithium deposited on a novel flexible ceramic substrate. A systematic study on the bending state and performance of the battery is presented. The battery withstands bending radii of at least 14 mm achieving 70% of the theoretical capacity. Here, we reveal that convex bending has a positive effect on battery capacity showing an average increase of 5.5%, whereas concave bending decreases the capacity by 4% in contrast with recent studies. We show that the change in capacity upon bending may well be associated to the Li-ion diffusion kinetic change through the electrode when different external forces are applied. Finally, an encapsulation scheme is presented allowing sufficient bending of the device and operation for at least 500 cycles in air. The results are meant to improve the understanding of the phenomena present in thin-film batteries while undergoing bending rather than showing improvements in battery performance and lifetime. 相似文献
147.
148.
林苏建 《河南工业大学学报(自然科学版)》1998,(4)
论述了粮食楼房仓中钢筋混凝土扁梁的设计及主要技术经济指标。应用钢筋砼扁梁结构可使建筑物在不增加层高的基础上提供更大的空间,以满足建筑的要求,且无特殊施工要求 相似文献
149.
Abstract— Coatings of indium tin oxide (ITO) nanoparticles on different flexible polymer substrates were investigated with respect to the achievable sheet resistance and their electrical behavior under oscillatory bending. As substrate materials, polyethyleneterephthalate (PET), polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), and polyimide (PI) were chosen, the surface resistances on the different polymer substrates were compared as a function of annealing temperature and surface topography. The surface topography, which has a strong influence on the surface resistance, was characterized by means of a white‐light confocal (WL‐CF) microscope. On the PET substrate, which exhibits the smoothest surface, the coating of ITO nanoparticles shows the lowest sheet resistance of 2 kΩ/□ for a layer thickness of 3 μm and an annealing temperature of 200°C. Furthermore, the electrical behavior of coatings of ITO nanoparticles under oscillatory bending was investigated using a special device. These coatings show a cyclic change of the conductivity which can be explained by an alternating compression and extension of crack flanks under the applied stress. Due to the growing number of cracks with increasing number of cycles, a decrease of the conductivity is observed in the bent state as well as in the balanced state. For a small bending radii, the decrease of the conductivity is stronger due to more cracks caused by the higher tensile stresses in the layer. The electrical behavior of the coatings of the annealed ITO nanoparticles on PET films under oscillatory bending was compared with commercially available sputtered ITO coatings. The annealed coatings of ITO nanoparticles demonstrate better electrical properties under oscillatory bending than coatings of sputtered ITO. The different electrical behavior under oscillatory bending can be related to differences in crack formation. 相似文献
150.
Kenichi Noguchi Yukihisa Matsuda Manabu Oishi Takaki Masaki Sadao Nakayama Masahiro Mizushina 《Journal of the American Ceramic Society》1990,73(9):2667-2676
Tensile strength of Y2 O3 -stabilized ZrO2 polycrystals (Y-TZP) was measured by a newly developed tensile testing method with a rectangular bar. The tensile strength of Y-TZP was lower than that of the three-point bend strength, and the shape of the tensile strength distribution was quite different from that of the three-point bend strength distribution. It was difficult to predict the distribution curve of the tensile strength using the data of the three-point bend strength by one-modal Weibull distribution. The distribution of the tensile strength was analyzed by two- or three-model Weibull distribution coupled with an analysis of fracture origins. The distribution curve of the three-point bend strength which was estimated by multimodal Weibull distribution agreed favorably with that of the measured three-point bend strength values. A two-modal Weibull distribution function was formulated approximately from the distributions of the tensile and three-point bend strengths, and the estimated two-modal Weibull distribution function for the four-point bend strength agreed well with the measured four-point bend strength. 相似文献