An Adjustable Double-sided Bending Mechanism

For the current bending industry needs to achieve bending different thickness,different specifications and double-sided bending production,an automatic adjustable double-sided bending method is proposed. The main steps of this method are as follows: First,the structure model is established according to the bending process requirements; Then,the PLC control system and the robot system are developed; Finally,the digital bending programming of the man-machine interface is carried out. It is proved by practices that the double-sided bending mechanism,control system and robot system are applied to the bending system which improves the bending forming quality,forming precision and processing efficiency. It promotes the rapid development of bending industry and the application prospect is very broad.     

Bending loss of elliptical-hole core circular-hole holey fibers bent in arbitrary bending directions

A holey fiber having a core with an elliptical-hole lattice structure, which is referred to as an elliptical-hole core circular-hole holey fiber (EC-CHF), can be easily designed as a single-polarization fiber by using the fundamental space-filling modes of the core and cladding lattices. However, because the guided mode in an EC-CHF has a polarization that arises from the large geometric anisotropy of the core lattice, the influence of the bending direction on the bending loss is a crucial issue for the practical implementation of EC-CHFs. Here, the bending losses of an EC-CHF bent in arbitrary angular orientations with respect to the core cross section are calculated numerically using the equivalent anisotropic step-index circular fiber model for a real EC-CHF, and the influence of the bending direction of the fiber on the bending loss is discussed.     

Fatigue of structures and secondary bending in structural elements

Secondary bending occurs in structural elements with geometric eccentricities when the element is loaded in tension. Eccentricities are present in lap joints, but also in plates with a locally increased thickness. Due to the eccentricities out-of-plane displacements occur with local bending as a result. This secondary bending phenomenon is unfavourable for the fatigue properties of a structure. In the paper secondary bending is analyzed with FE calculations and also with a neutral line model. A bending factor is defined as the ratio of the bending stress and the nominally applied tensile stress. Numerical data are presented for riveted joints and for an open hole with a reinforced edge around the hole. Stress concentrations are significantly enlarged by the bending stress. This problem should be considered for designing against fatigue, but secondary bending has received limited attention so far.     

Application of a Genetic Algorithm to Computer-aided Bending Sequence Planning

Optimal design of the bending sequence is a key link in sheet metal free bending sequence planning,and it has an important influence on simplifying operation and guaranteeing bending precision. Bending sequence must meet the requirements for not only no collision interference of the work piece and the mold,but also working efficiency and working precision,so bending point choice,molds select,turnover and turn round of sheet metal must be considered in each bending step. In this paper,a genetic algorithm is used to design bending sequence. The interference identification is used to determine coding,exchange and mutation of the genetic algorithm. The genetic algorithm is developed to calculate the current optimal feasible solution of the bending sequence,and then the influence of initial population and evolution generations of this method on the result is analyzed by example verifications. The results prove that a global optimal solution can be obtained while the bending point number was less than 10,and optimal bending sequence which is similar to the global optimal solution can be calculated while the bending point number was more than 10. The results converge gradually to the global optimal solution with the increase of the initial population and evolution generations. As to 18 points bending work-piece,with the initial population size 150 and the evolution generations 100,we can obtain the satisfying solution.     

磨具弯曲成形法非球面研磨的研磨模型

磨具弯曲成形法是加工光学非球面零件的新方法,是线接触研磨过程.给出了弯曲成形法研磨的原理,基于Preston方程,限定磨具弯曲成形法特定研磨条件,分析了加工面上的任意一点的压力函数和相对速度函数,推导了磨具弯曲成形法研磨材料去除量函数表达式,推导了研磨作用时间函数.该研磨模型为磨具弯曲成形法研磨实践提供了理论依据.     

复杂空间弯管三维自由弯曲成形有限元模拟及试验

目的以一复杂空间弯管为例,开展三维自由弯曲成形实验研究。方法首先提出三维自由弯曲成形工艺解析方法,然后通过有限元模拟与实际试验相结合的方法进行研究。结果有限元模拟所得到的弯管与CAD模型相比,弯曲半径偏差值不超过2%,吻合度较高。实际成形出的弯管与CAD模型对比显示,第1个弯曲段的实际弯曲半径为118 mm,设计值为120 mm,实际值与设计值偏差1.67%;第2个弯曲段的实际弯曲半径为133 mm,设计值为130 mm,实际值与设计值偏差2.30%,2个弯曲半径的偏差值均不超过3%。结论验证了三维自由弯曲成形工艺解析方法的可靠性,有限元模拟较好地指导了实际成形试验。     

盾构隧道衬砌整环力学机理模型

目前未见有普遍适用的理论公式来表征盾构隧道衬砌结构参数的内在联系。该文首先提出了用“代表性区段”体现整环结构弯曲刚度特征的思想,然后建立了通缝和错缝条件下管片环拼装力学机理模型,接着运用力学模型推导出弯曲刚度有效率和弯矩提高率等参数的取值公式和相互关系式,最后验证了公式的正确性。研究表明:力学模型能够推导出弯曲刚度有效率、管片体弯矩提高率、管片接头弯矩减少率、衬砌结构参数之间的关系公式;管片接头弯矩减小率未必等于管片体弯矩提高率,表明传统采用单一弯矩提高率值的做法不够科学;匀质圆环法还能给出环间接头径向最大剪力取值,并且其结果较为可靠;参数取值公式中有两个重要的中间参数,与环向相对刚度和径向相对刚度具有相似性,应予重视。参数取值理论公式的提出,对揭示盾构隧道整环拼装内在力学本质有着重要价值。     

利用振动模态分析确定对称复合层板结构的材料特性

针对周边简支和周边固支含弯曲·扭曲耦合的对称复合材料层板,本文首先推导了利用振动模态分析进行层板５个弯曲刚度常数评价的理论公式,并利用振动测试得到的有限个离散点的挠度信息对振动模态进行近似处理,最后利用最小二乘法求解层板的弯曲刚度。在数值算例中,本文对两种边界条件下三种对称复合材料层板的弯曲刚度进行了评价,同时考察了测试点数目对弯曲刚度常数评价误差的影响。     

Bending impact on the performance of a flexible Li4Ti5O12-based all-solid-state thin-film battery

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.     

面内弯矩作用下弯管应力高次解

该文采用应变分析和能量法得出了面内弯矩作用下弯管环向和轴向应力的解析解,并提出了高次解的求解方法。该方法的计算结果与其他各种解析解的结果进行比较表明:该文提出的方法能得到更精确的结果,并适用于所有弯曲系数的弯管。该方法可用于计算弯管在面内闭合弯矩和面内张开弯矩下的应力。     

板料激光成形的正交实验设计与量纲分析

激光弯曲是一种利用激光加热来实现构件的柔性成形技术。利用正交实验研究各可控因素对弯曲角度的影响,通过量纲分析建立数学模型,根据正交实验数据对数学模型的相应参数进行回归求解。研究结果表明,利用正交实验可对激光成形的工艺参数进行全面评估;利用量纲分析法仿真复杂的激光弯曲过程是简便有效的。     

土木工程用CFRP筋弯折抗拉性能

针对碳纤维增强复合材料(CFRP)筋应用于土木工程过程中的弯折抗拉性能,开发了新型的抗拉强度测试技术对CFRP筋材真实抗拉强度进行了实测。利用模型试验对不同弯折角度下CFRP筋的弯折抗拉强度进行了测试,获得了CFRP筋应用于土木工程时对应弯折状态下的弯折抗拉强度折减系数,并拟合出该系数的经验公式。结果表明: 现有的CFRP筋材抗拉强度测试技术的测试结果明显偏低,新开发的测试技术较之提高的幅度超过9%;给出的计算公式能预测不同折角下弯折抗拉强度的折减系数,当折角达到3°时,CFRP筋弯折抗拉强度较直线状态下降了18.9%。 因此,在实际工程应用过程中,即使发生较小角度的弯折,也需考虑弯折对CFRP筋抗拉性能的折减。     

Estimation of bending resistance of Ionic Polymer Metal Composite (IPMC) actuator following variable parameters pseudo-rigid body model

In this article bending resistance of IPMC has been estimated following a newly proposed variable parameters pseudo-rigid body model. First an experiment is conducted to study the voltage versus bending characteristics of IPMC and based on the experimental data the IPMC has been modeled through the proposed technique. Simulation has been performed and estimation of bending resistance has been made based on experimental results. It is observed that bending resistance of IPMC increases with input voltages although the changes remain insignificant after certain range.     

A linear theory for bending stress-strain analysis of a beam with an edge crack

In this paper, a new linear theory for bending stress-strain analysis of a cracked beam has been developed. A displacement field has been suggested for the beam strain and stress calculations. The bending differential equation for the beam has been written using equilibrium equations. The required constant for this model is also obtained from fracture mechanics. The bending equation has been solved for a simply supported beam with rectangular cross-section and the results are compared with finite element and empirical results. There is an excellent agreement between theoretical results and those obtained by numerical and empirical methods. The model developed in this research is a simple and precise approximation of the behavior of the cracked beams in bending.     

基于长冲程振动台导轨弯曲校正的低频振动传感器校准方法

针对长冲程振动台的导轨弯曲对于基于振动台的低频振动传感器灵敏度幅值校准的影响,采用机器视觉方法测量导轨弯曲。通过建立校正模型消除导轨弯曲的影响,以提高灵敏度幅值的校准精度。导轨弯曲测量结果表明,被校振动传感器的负载越大,导轨弯曲越大,对灵敏度幅值校准的影响越大。与地球重力法的对比试验表明,在0.04～2 Hz范围内弯曲校正后的灵敏度幅值校准精度提升了一个数量级。     

Light propagation in curved silver nanowire plasmonic waveguides

Plasmonic waveguides made of metal nanowires (NWs) possess significant potential for applications in integrated photonic and electronic devices. Energy loss induced by bending of a NW during light propagation is critical in affecting its performance as a plasmonic waveguide. We report the characterization of the pure bending loss in curved crystalline silver NW plasmonic waveguides by decoupling the energy loss caused by bending and propagation. The energy attenuation coefficiency due purely to bending was also determined, which exhibited an exponential relationship with the bending radius. Finite-difference-time-domain (FDTD) methods were utilized for theoretical simulations, which matched the experimental results well.     

Characteristic analysis of nanosilicon rectangular waveguides for planar light-wave circuits of high integration

When a full-vectorial finite-difference method is used, rectangular Si waveguides can be characterized for planar light-wave circuits of high integration. The single-mode condition for a rectangular Si waveguide is obtained first. The birefringence, which can be adjusted by modifying the thickness of the cladding layer, is also studied. For a nano-Si rectangular waveguide the pure bending loss is very small even for an ultrasmall bending radius (e.g., a few micrometers), and the transition loss becomes dominant. The width and height are optimized to minimize the bending radius for the requirement that the bending loss is smaller than 0.1 dB. Finally the coupling between two parallel straight waveguides is analyzed, and it is shown that there is an optimal width for the maximal coupling length.     

Analytical Solution for an Orthotropic Elastic Plate Containing Cracks

The problem of estimating the bending stress distribution in the neighborhood of a crack located on a single line in an orthotropic elastic plate of constant thickness subjected to bending moment or twisting moment is examined. Using classical plate theory and integral transform techniques, the general formulae for the bending moment and twisting moment in an elastic plate containing cracks located on a single line are derived. The solution is obtained in a closed form for the case in which there is a single crack in an infinite plate and the results are compared with those obtained from the literature.     

Realization of an on-line fiber-optic bending loss measurement system

In this paper, an on-line bending loss measurement system is studied and realized. To avoid complicated calculation of fiber bending loss, we propose a simplified theoretical model for on-line evaluation. A specific fiber adaptor is developed for light signal feeding and picking up through a free space optical fiber coupling technique. Relevant factors, including free space fiber misalignment, are considered. The signal-to-noise ratio of the whole system is improved by optimizing the spatial perturbation length of the fiber and the deformation of the bending fiber. The use of an on-line monitoring technique for measuring the bending loss of optical fibers is presented in this paper. With this technique, manufacturing efficiency can be improved, and the cost of maintaining fiber quality control can be reduced.     

Effect of reinforcing layer on shape fixity and time-dependent deployment in shape-memory polymer textile composites

The purpose of the present study is to model shape fixity and time-dependent deployment in shape-memory polymer composites (SMPCs) and to evaluate the effect of textiles’ tensile and bending moduli on these properties. We constructed an SMPC model by combining SMP layers and a reinforcing layer. We also considered the thermo-viscoelasticity of SMP and the difference in values between the tensile and bending moduli of the reinforcing layer. Employing this model, we simulated deployment under pure bending conditions. Comparison with experimental results confirmed that our proposed model is able to simulate shape fixity and time-dependent deployment in SMPCs. We also confirmed that the bending modulus is an important factor for shape fixity and time-dependent deployment, whereas the tensile modulus has nothing to do with these properties.