Studying Formability Limits By Combining Conventional and Incremental Sheet Forming Process

In this work it is assessed the potential of combining conventional and incremental sheet forming processes in a same sheet of metal.This so-called hybrid forming approach is performed through the manufacture of a pre-forming by conventional forming,followed by incremental sheet forming.The main objective is analyzing strain evolution.The pre-forming induced in the conventional forming stage will determine the strain paths,directly influencing the strains produced by the incremental process.To conduct the study,in the conventional processes,strains were imposed in three different ways with distinct true strains.At the incremental stage,the pyramid strategy was adopted with differ-ent wall slopes.From the experiments,the true strains and the final geometries were analyzed.Numerical simulation was also employed for the sake of comparison and correlation with the measured data.It could be observed that single-stretch pre-strain was directly proportional to the maximum incremental strains achieved,whereas samples subjected to biaxial pre-strain influenced the formability according to the degree of pre-strain applied.Pre-strain driven by the prior deep-drawing operation did not result,in this particular geometry,in increased formability.     

基于薄板变形的机器人柔顺触觉传感器研究

针对机器人抓握处于重力场中的等截面均质杆件，设计了一种基于薄板变形的柔顺触觉传感器。在传感器中，利用金属弹性薄板做弹性元件，应变片做触觉敏感单元，实现对物体的长度和质量的感知。在传感器的表面封装电流变流体实现了软／硬抓握。采用合理结构，使被抓物体横截面尺寸不受金属弹性薄板尺寸的限制，并保证金属薄板不被破坏．另外，着重给出了金属薄板的边界条件为一对边固定支撑，另一对边简单支撑的情况下传感器的测量原理。最后将传感器安装在机器人平行抓握手爪上，进行了抓握试验。实验表明，这种触觉传感器测量精度比较高，范围广，耐用性好。     

Dynamic deformation behavior of aluminum alloys under high strain rate compressive/tensile loading

Mechanical properties of the materials used for transportations and industrial machinery under high strain rate loading conditions such as seismic loading are required to provide appropriate safety assessment to these mechanical structures. The Split Hopkinson Pressure Bar (SHPB) technique with a special experimental apparatus can be used to obtain the material behavior under high strain rate loading conditions. In this paper, dynamic deformation behaviors of the aluminum alloys such as A12024-T4, A16061T-6 and A17075-T6 under both high strain rate compressive and tensile loading conditions are determined using the SHPB technique.     

Modelling of inelastic bending of a metal sheet with thermal coupling

The modelling and numerical analysis of inelastic bending of a metal sheet are presented. The distribution strains and stresses are found for slow and fast bending while taking into account the geometrical and material non-linearities. The constitutive relation of Klepaczko, (Int. J. Plast. 17 (2001) 87, Comput. Methods Appl. Mech. Eng. 175 (1999) 19) was used which includes strain hardening, strain rate sensitivity and temperature effect in material behaviour. The large strains are assumed under plane strain conditions. The results with complete thermal coupling are compared with solutions obtained in the isothermal conditions of bending.     

基于多层前向神经网络的应力传感器故障诊断

文中采用多层前向神经网络（BP网）建立数学模型,在此基础上对应变片传感器进行故障诊断。     

Elastic recovery of a scratch in a polymeric surface: experiments and analysis

A scratch may be regarded as a tangential indentation. Hence standard indentation laws can be used to analyse the geometry of the scratches left by a moving tip on the surface of a viscoelastic viscoplastic body such as a commercial grade of cast polymethylmethacrylate (PMMA). This paper presents experimental results and an analysis of the elastic recovery of a scratch after contact with a tip. The experimental data were obtained with a new scratch apparatus fitted with a built-in microscope, which allows in situ analysis of the contact area and the groove left on the surface. The elastic plastic total penetration depth h_ep is split into its plastic part h_p and elastic part h_e. In the case of full plasticity around the tip during scratching, which for an elastic plastic material implies a sufficiently high value of the contact strain, the elastic law describes the depth relaxation and experimental data agree with the analysis. In the case of a purely elastic response of the material, corresponding to low values of the contact strain, the rear contact radius is equal to the front contact radius. At intermediate levels of strain, an analysis of the elastic recovery must take into account the contribution of the plastic term to the elastic plastic response of the material.     

Microstructure development during constant-force drawing of poly(ethylene terephthalate) film

Structure development in PET film during high strain-rate, constant-force (CF) deformation in the temperature range 80–96°C is compared with structure development during lower strain rate, constant-extension-rate (CER) deformation in a similar temperature range. The higher (maximum) strain rates involved in CF drawing mean that much of the deformation takes place in a regime where the time available for orientational relaxation and crystallization is short. This results in high levels of ‘non-crystalline orientation' and low levels of crystallinity compared to structures obtained from CER drawing. In CER drawing, due to the lower strain rates, the degree of crystallinity always has time to reach pseudo-equilibrium values corresponding to a given level of non-crystalline orientation, and the amount of orientational relaxation occurring during drawing has the dominant influence on structure development. In CF drawing, pseudo-equilibrium crystallinity values are not reached, except when the deformation approaches the tail-end of the strain-rate spectrum. The results also provide confirmation that microstructure data obtained from rapidly quenched samples are consistent with microstructure data obtained from real-time experiments.     

山东省果树害虫的发生现状与防治

山东省果树害虫约４００种,重要害虫９０余种,主要类群是蚜虫、叶螨、蚧虫、叶蝉金龟食心虫、卷叶潜的、蛀木害虫等,通过植物检疫、农业、生物、农药等综合防治措施可有效地控制其发生危害。     

Design optimization of semiconductor piezoresistors with Schottky diode contacts

A modeling theory is developed to predict the performance of piezoresistors which incorporate Schottky diode electrical contacts. This new theory allows the design of high performance gauges which can be fabricated using Non-Lithographically-Based Microfabrication (NLBM) techniques. These semiconductor piezoresistors can be designed in customizable sizes and fabricated in parallel in order to integrate position sensing into MEMS flexural positioners. Customizable sensing for nanopositioning platforms will enable advances in a range of nano-scale fabrication and metrology applications. A semiconductor piezoresistor with Schottky diode contacts was fabricated and attached to a titanium flexure. This device is shown to match predicted electrical performance within about 8% and to show a gauge factor of 116, within 2% of the predicted value. Optimized performance limits for Schottky diode semiconductor piezoresistors are identified to be about 127 dB full noise dynamic range for a quarter bridge over a 10 kHz sensor bandwidth on a 600 μm width titanium flexure, making them ideal for sensing on meso-/micro-scale flexural positioners. Methods are suggested for achieving the performance limits indicated above and the impact of these methods on the sensor dynamic range are studied.     

互补偿型光纤双向应变-位移点式传感器

在互补偿型光纤双向应变-位移传感器中，耦合器将光分束到粘贴于拉敏区或压敏区的两根光纤，且调制光由两探测器测量。通过引入拉敏光纤和压敏光纤的自相对损耗，可有效消除光纤应变-位移传感器中光源功率波动所引起的误差。微位移架上的位移实验表明标准误差是-0．16mm。