Applied Mechanics and Materials Vols. 37-38

Abstract: It is inefficient and complicate to detect geometric errors of a heavy machine tool with large scale dimensions by using traditional laser interferometer. With the development of the laser tracker convenient for measuring large scale dimension, the accuracy of the laser tracker can meet the accuracy requirements for geometric error measurement of heavy machine tools. In this paper a method of using laser tracker for detecting and identifying the error of a heavy NC boring and milling machine tool is introduced. The measuring experiment demonstrates that this new method can improve the measurement efficiency.

Abstract: In order to detect the distance automatically, a distance detect system was established. It applied methods such as how to obtain the laser center, how to obtain the three-dimensional information, and so on. First, set the width threshold and depth threshold to locate the laser, then searched the follow laser in a nearby region, and found the laser center by geometric methods. Second, reconstructed the laser center, transformed the data coordinate, converted the data into plane, finally computed the distance by geometric and statistics methods. Experimental results show the laser center data are continuous, noiseless. The precision of the step height is 50μm.

Abstract: This paper proposes a new kind of detection method based on CCD to measure geometry sizes and roundness error of chain board of roller chain. Image is collected, and is input into computer, then is processed by a series of steps such as grey level transformation, image smoothness, lower filtration, and threshold value selection, etc. The measurement of the geometric parameters and the roundness error relies on the image contour. Roundness error is evaluated by Minimum Region Law. The diameter of the holes and the distance between the axes of two holes are calculated and measured by self-developed program. Roundness error of chain board is less than 8μm, and the distance error between the axes of two holes is 9μm. The diameters of the holes are 4.467mm and 4.461mm respectively. The reasons of measurement error are also analyzed. Theory analyses and experiment show that it is feasible to measure the geometric sizes and roundness error of roller chain by this method, which is both efficient and practicable.

Abstract: In this paper, the sensing block method proposed by Tanimura etc. which would be used to measure the dynamic force, was discussed numerically by LS-DYNA finite element. The influence of reflected stress waves from the base block were analyzed when the sensing projection was in a larger size range. The result shows that it can’t measure the dynamic load accurately with increasing the size of sensing projection. Furthermore, an improved method was developed and discussed with its application in the large-scale device for measurement of the dynamic load.

Abstract: Wrinkling and tearing are the main failure modes in sheet-metal forming. Wrinkle may occur at the start of a punch stroke if the blank-holder force (BHF) is too low, and tearing may occur at the end of a stroke if the BHF is too high. The BHF is important for deep-drawing because of an effective way to promote deep formability sheet metal. They can be reduced or eliminated by manipulating a suitable BHF during sheet-metal forming. This paper presented an attempt to determine the effect of variable BHF on the tearing and wrinkling and investigated using 08Al sheet metal. The experiment show that tearing and wrinkling can be eliminated and the quality of deep drawing of rectangle parts can be improved using variable BHF.

Abstract: To improve inclination error evaluation of planar lines, chaos optimization is proposed to evaluate the minimum zone error in this paper. The evolutional optimum model and the calculation process are introduced. By using the properties of ergodicity, stochastic property, and “regularity” of chaos, the efficiency of chaos optimization algorithm (COA) is much higher than some stochastic algorithms such as simulated anneal algorithm (SAA) and genetic algorithm (GA) when COA is used to a kind of continuous problems. The chaos optimization algorithm can improve the efficiency of searching in the whole field by gradually shrinking the area of optimization variable. Finally, the control experiment results evaluated by different method such as the Least Square, Simplex search, Powell optimum methods and GA, indicate that the proposed method does provide better accuracy on inclination error evaluation.

Abstract: Tension control is widely used in industrial production. This paper gives one tension control method using MRF damper as the actuator. The principle of the tension generation is introduced. Through analysis and numerical simulation, the main influence factor of tension changing is obtained. The result of simulation shows that the influence factor of the tension includes the excitation electric current of the MRF damper, the radius of a wheel, rotate speed, the fluctuation of the rotate, etc. These factors present strongly nonlinearity. Through controlling the excitation electric current of MRF damper, the fluctuation of tension can be controlled to decrease.

Abstract: The combined three-section crossbeam is an important component in the heavy gantry CNC milling-lathing machine tool and the dynamic characteristics are key precision factors for the machine tool. Three sections of the combined crossbeam are bolted by large industrial bolts and the influence of bolted joints should be evaluated in the dynamic analysis of the combined crossbeam. The dynamic characteristics of the combined three-section crossbeam were extracted by the modal experiment. The FEM of the monolithic crossbeam was modeled to analyze the dynamic characteristic parameters. The comparison of the analysis result and experimental result were shown. The experimental result matched well with the FEM of the monolithic crossbeam without bolted joints. As a result, the influence of the bolted joints could be ignorable in dynamic characteristic for the combined three-section crossbeam.

Abstract: Cu thin films were prepared by DC magnetron sputtering on Si substrate, and the resistivities change by adjusting its sputtering parameters. It is found that the changes of the sputtering power and substrate temperature and working pressure can affect significantly the Cu film resistivity (ρ). The Cu films resistivity decreases with the increasing of sputtering power. As the substrate temperature “structure zone model” effect, the Cu film resistivity decreases when the substrate temperature was less than 150°C. The resistivities (ρ) begin to increase gradually at various temperatures ranging from 150°C to 300°C, but the rate of increase is not significant. The resistivity abnormal increases when the substrate temperature was 400°C. The Cu films resistivity increases with argon working gas pressure ranging from 0.15 Pa to 2 Pa.

Abstract: The effect of various micro isosceles-trapezoid grooves on improvement of tribological performance is discussed. It is accomplished through the CFD-approach where the momentum and continuity equations are solved separately, one of low Reynolds turbulence models-Abid index and SIMPLE algorithm in theory of Control Volume Method are adopted. For different width and depth of micro isosceles-trapezoid grooves, the load supporting capacity of oil-film are compared. The results show that the widths has more influence than the depths on hydrodynamic lubrication, and relative parameters change monotonously with the depth of micro-groove. The effect of texturing arc-grooves on improvement of tribological properties is conspicuous if w₁ = 40μm, w₂ = 10μm and h_p = 10μm for micro isosceles-trapezoid grooves.