Papers by Keyword: Curvature Radius

Abstract: This paper presents a methodology for pencil-cutting regions detection in five axis NC machining of free-form surfaces. The local interference of surface occurs when the radius of the local surface curvature is smaller than that of the cutter. It is a time-consuming work to calculate the free-form surface curvature by differential geometry, so the arc radius is used to approximately compute the curvature radius of the surface to judge the local interference. Computer implementation and practical examples are also presented in this paper.

Abstract: In this paper, a method for evaluating the curvature radius of conductive knitted fabrics was reported. Plain knitted fabrics were made by using conductive fibers on a hand-driven V-bed flat knitting machine. The needle movement and loop formation during the knitting action were recorded, and then these images were analyzed by using the image processing approach for obtaining the curvature radius of needle loop. Finally, the knitting actions of two conductive fibers under two conditions were evaluated.

Abstract: Stress gradient of a thin film along its thickness direction has important influence on performance of MEMS/NEMS devices. The measuring method based on curvature radius is a usual method for extracting film stress gradient. In this paper the error of the method has been analyzed using Finite Element Analysis software Coventorware, and the current theory has been modified according to FEA results to enhance its accuracy. Simulating results indicated that the accuracy of the method has been increased observably after correcting.

Abstract: In this article, the bending deformation of stainless steel fibers during knitting action was investigated. Two stainless steel fibers with different configurations were knitted into plain knitted fabrics on a flat knitting machine. During the knitting action, the formation of needle loops were recorded and analyzed by using the image processing approach. The curvature radius of the needle loop was examined and regressed with polynomial fitting. The experimental results indicate that stiffness is the main factor affecting the bending deformation. Yarn diameter and needle geometry are another two important factors influencing the bending deformation.

Abstract: The influence of radius ratio of cutting point and cutter on cutting force and stability during end milling process is presented in this paper. To derive motion equations, a 2 DOF mechanical model of end milling considering both regenerative and self-excited effects was established. Different ratio values during three milling conditions were analyzed. Cutting forces as well as stability under different radius ratios by changing curvature radius and cutter radius were elaborated respectively. The results show that when other parameters are set fixed, cutter with relative large radius has smaller cutting force and larger stable range. Cutters with same radius will overlap on cutting force when radius ratio is large enough even under different milling conditions. The proposed analysis on cutting force and stability can be used to determine the optimal parameters, such as cutter radius and spindle speed etc. to improve the accuracy and productivity.

Abstract: The curvature radius is a very important factor which influences the dynamic performance of the curved continuous long bridge badly. This paper based on the practical engineering, with large finite element program, established the curved continuous long bridge space finite element calculation model. Respectively by response spectrum method and the time-history response method, consider single-point excitation and multi-support excitation seismic action, Analyzes different radius of curvature in curved continuous long bridge self-vibration frequency, internal force and displacement on the differences, and given the internal relations between the difference and the curvature radius, offer some reasonable design reference suggestion for curved continuous long bridge of the radius of curvature.

Abstract: Based on fundamental theory and variational principle of thin-walled curved beam and taking into account of coupling effect of bend and shear lag, the paper mainly discusses the variation of curvature radius and the transverse distribution of load in order to analyze effect of shear lag in curved box girder. By means of variational method, the paper derivates the elastic differential equation and boundary conditions and gives numerical results of equations finally, results are obtained by the Galerkin method. It shows that the curvature radius and the transverse distribution of load in the shear lag of curved box girder is very important by comparing the calculating results.

Abstract: Single Point Incremental Forming (SPIF) is a novel sheet metal forming process. The formability (i.e. spif-ability) in this process is determined through Varying Wall Angle Conical Frustum (VWACF) test. In this paper, the effect of variation in the curvature radius, a geometrical parameter of test, on the test results is investigated. A series of VWACF tests with a variety of curvature radii is performed to quantify the said effect. It is found that the spif-ability increases with increasing of curvature radius. However, any variation in the curvature radius does not affect the spif-ability when the normalized curvature radius (i.e. curvature radius/tool radius) becomes higher than 9.

Abstract: CFRP (Carbon Fiber Reinforced Plastics) of the advanced composite materials as structural materials for vehicles, has a wide application in light weighs structural materials of airplanes, ships and automobiles because of high strength and stiffness. However, there is a design variable to be considered in practical application of the laminate composite material, that is, this material is vulnerable to transverse impact. This paper aims at evaluating the effects of curvature and oblique impact on the penetration characteristics of composite laminate shells. They are stacked to [02/902]S, [03/903]S and [02/903/0]S, [0/902/0]S and their interlaminar number two and four. Those specimens were prepared to varied curvature radius (R=100, 150, 200mm and ∞). They are cured by heating to the appropriate hardening temperature (130oC) by means of a heater at the vacuum bag of the autoclave. Test specimens were prepared with dimensions 100mm×140mm. When the specimen is subjected to transverse impact by a steel ball, the velocity of the steel ball was measured both before and after impact by determining the time for it to pass two ballistic-screen sensors located a known distance apart. In general, the critical penetration energy increased as the curvature increased, interface decreased and slope angle on the impact surface increased.