Advanced Materials Research Vols. 875-877

Abstract: This paper investigates the effect of process parameters such as Blank Holder Force (BHF) and Feed Rate, on the spring back behavior of a polymer metal laminate (PML) system comprised of aluminum and polypropylene. Specimens were formed over a hemispherical punch in stamp forming process. A novel real time strain measuring system, ARAMIS, was employed to capture the strain evolution during forming. The results of this work indicate that both BHF and feed-rate exert influence in PML spring back behavior. Fundamental correlation between strain evolution during spring back and the shape of the finished part will be presented. A major finding from this work is that aluminum dominates the spring back behavior of PML in stamp forming.

Abstract: Keywords: electrical contact lubricant contact resistance sliding wear Abstract. The contacts must be reliable in the required life time under practical application. Reliability means that the contact resistance can maintain low and stable. Au-plated contact pairs have been used widely for weak current connectors due to its well electrical and anti-corrosion performance. The high price of gold forces manufacturers to reduce the thickness of Au-plated while maintaining well performance. Increasing thin of Au plating causes the microporosity to increase rapidly, which has harmful effect on the performance of connectors. Appropriate lubricant coated on contact pair is a solution to improve the contact property. This paper focuses on sliding contact performance of gold plated contact pairs coupon with 0.25 m thickness and lubricated with water based lubricant named lub-E under damp heat and corrosion environment respectively. The contact pairs are also exposed in damp heat, corrosion environment respectively to evaluate the anti contamination property. The sliding experiment is conducted at frequency of 1Hz, amplitude of 1cm, and load of 0.5N, 1.0N and 1.5N. Contact resistance data is gotten in every sliding cycle at the condition of DC current 100mA and limited voltage 1.0V. Scanning electron microscopy (SEM) is used to observe the sliding track morphology and X-ray energy dispersive spectroscopy (EDS) is used to analyze the element.

Abstract: Fretting is one of the main reasons for electric contact failure. Metal contact pairs have long been used, generally with the structure of copper alloy base, Ni interlayer and surface noble metal (such as gold) plating. The influences of plating material and plating thickness on fretting property have been researched deeply, meanwhile, new materials have been tried. In this paper, a new conductive material, silver conducting adhesive is used as the surface coating of contact pair, and a series of tests have been done to study the performance of fretting wear by compare with the coupons without silver conducting adhesive. The results show that the use of silver conductive adhesive improves the fretting property of electrical contacts, especially with small normal force.

Abstract: Natural rivers are characterized by continuous variations in bed topography, especially along curved reaches. High resolution topographic data are necessary to analyze the mutual interactions between the downstream flow and the cross-stream flow, which determine the distribution of the bed-shear stress along the channel. Because of the difficulty in acquiring good and accurate data in rivers, the major part of studies have been conducted in laboratory flumes. This paper reports on a laboratory study in which the automatic digital photogrammetric survey was applied to derive the high-resolution Digital Surface Model (DSM) of the bed topography in a large amplitude meandering flume. In order to assess the advantages of the procedure, the bed profiles obtained by the DSM have been compared with those obtained using a servo-controlled vertical profiler (PV09) has been operated and discussed.

Abstract: The paper deals with the study of dominant frequencies of an Impact-Echo method response signal obtained from a reinforced concrete beam with a steel rod diameter of 8 mm. Tension pulse was produced in axis of the rod at one end and detected in axis at opposite end of rod. Dominant frequencies of the response signal will be the main criterions for the reinforced concrete rebar corrosion progress. The article presents the results of measurements obtained after 12 months controlled degradation in aqueous NaCl solution. The results were compared with measurements of electrical resistance of reinforcing steel by using the Thomson double bridge.

Abstract: Roll forming is a well known bending process and sheet metals can only be machined into two-dimensional surfaces in traditional roll forming. While with more and more personalized demands, three-dimensional surfaces are widely required. Thus, flexible rollers are used to achieve three-dimensional surfaces. And in order to optimize experimental parameters and to predict experimental results, finite element method (FEM) is developed. In this paper the set-up of flexible roll-forming is described and the process of roll forming is simulated. Then the influences of forming parameters, such as the thickness and the roll velocity, on forming quality of the sheet metal in roll forming process are discussed. The results show that the analysis of flexible roller parameters is practical for the continuous and efficient forming of three-dimensional surfaces.

Abstract: The usage of softer systems in automotive bumper is a growing trend currently especially to serve the pedestrians safety function. The term softer here does refer to the bumper system’s dynamic behavior rather than its material’s flexure or tension modules. However, the usage of such softer systems would raise issues of structural integrity of the bumper during crash. There is a strong drive currently to adopt materials such as glass mat thermoplastic (GMT), high-strength sheet molding compound (SMC) for the bumper material and plastic polypropylene (PEP) for the bumper holders [1, 2, 3] in this regard. While both the GMT and SMC do enhance the pedestrian safety condition, they both show plastic deformation at crash, even in low-speed scenarios [2, 3]. The PEP holders react only as shock absorbers and act like mechanical fuses to be destroyed in car crash, preventing the main bumper from being damaged [4]. In this paper, we propose a remedy for this problem by changing the common system that the GMT and SMC materials are usually fitted at. We propose coating the bumper beam with a Rubber padding layer that eliminates the plastic strain at low-speed crash. We also examine the behavior of the PEP during such crash scenarios. We present here the results of a low-speed head-on automotive-pedestrian crash simulation scenario for these material models, using the explicit dynamics finite element code LS-DYNA within ANSYS integration setting. A simplified parameterized finite element model of the Ford Crown Victoria car’s bumper form is used in several crash simulations that are carried out to test the validity of this modified bumper system. Based on the results of these tests, we show that, applying the Rubber coating material for the GMT and SMC bumper beams eliminates the plastic stains at low-speed crash.

Abstract: Searching for quick methods to assess the material usefulness for constructing machine components working at elevated temperatures and variable stresses is accompanied with development of devices facilitating such testing. The paper presents construction of a device, that enables carrying out the standard creep tests (PN-EN ISO 204) and the dedicated tests with the programmed low-cycle loads and the different profiles for temperature and stress changes. The basic parameters of the device are described and the examples of the programmed strength testings are given.

Abstract: The electrically controlled birefringence of nematic liquid crystal BL-009 was measured by polarized interference method. The influence of LC absorption effect, the birefringence variation, is discussed in this paper. The experiments results showed the influence to birefringence is big in infrared region. Not only the birefringence value is greatly different with that of unconsidering absorption effect, but also the gradient changing of birefringence curves is obvious. Furthermore, the electrically controlled birefringences of two conditions are compared when the absorption coefficients of ordinary light and the extraordinary light are nearly same and greatly different. The analysis demonstrated the approximate method of absorption coefficient is feasible.

Abstract: The interactions of different kind of synthetic meshes with tissuses and influence of low-intensive laser irradiation – LILI was studied in experiment. Vistar white rats were used. For morphological investigations light and scanning electron microscopy – SEM. SEM revealed the complex structure of synthetic meshes `especially of PTFE mesh. Light-optical studies have shown that the implantation of meshes cause, in the early period of observation, moderate inflammatory reaction. LILI help in reducing of the alterative inflammation phase and leads to concluding with formation of soft connective tissue capsule on the surface of the mesh.