一种新的金刚石绳锯系统的开发及其在建筑施工中的应用效果

根据绳锯系统的开发及其在建筑施工中的应用,着重对该资料在设备开发、绳锯系统的改进设计、新绳锯的试验及其应用效果等方面作详细介绍.研究指出,新的绳锯系统具有设备重量轻、体积小、便于操作且绳锯消耗低、噪音小、污染少的优势.     

The diameter of Hanoi graphs

Many questions regarding the Tower of Hanoi problem have been posed and answered during the years. Variants of the classical puzzle, such as allowing more than 3 pegs, and imposing limitations on the possible moves among the pegs, raised the analogous questions for those variants. One such question is: given a variant, and a certain number of disks, find a pair of disk arrangements such that the minimal number of moves required for changing from the first to the second is maximal over all pairs. One of the main results of the paper is identifying these for the Cyclic_h variants—the variants with h pegs arranged along a uni-directional circle—to be the pairs of perfect configurations where the destination peg is right before the source peg.     

The role of hemodynamics in the development of the outflow tract of the heart

The question whether, and if so to what extent, hemodynamic forces and mechanical stimuli do modulate the morphogenesis of the vascular system is a century-old problem. It is important especially in the outflow tract where a spiraling septum develops in and after a strong bend in the tube. Spiraling patterns of the flow in bends are well known. Of the mechanical stimuli that can potentially exert an effect on morphogenesis, wall shear stress is the most likely candidate; a number of genes that are expressed in the cardiovascular system have shear-stress responsive elements in their regulatory units. Recent investigations have clearly shown that the disturbance of normal hemodynamic conditions results in maldevelopment of the heart. However, an experimental model alone is necessary, but not sufficient to identify the intermediate steps of the interaction between blood flow and tissue remodeling in the developing cardiovascular system, certainly at Reynolds numbers and Dean numbers that are very small. Therefore, a model with a simple geometry has been created, using the ComFlo software: a fully 3D computational fluid-dynamics code that solves the Navier-Stokes equations on a Cartesian grid. A first assessment of the possible influence of a strong curvature, with biological realistic dimensions, was made using steady-flow conditions. Since both the Reynolds number and the Womersley number (indicating the influence of the pulsatility on the velocity profile of the flow) are extremely low, it is likely that these flow patterns do not differ significantly from those under pulsatile conditions. A first assessment of the effects of the strong curvature on the flow under the given circumstances showed only very small secondary velocities and negligible heterogeneity of the wall shear stress, even in the presence of a strong secondary flow pattern in the inlet of the tube.     

Experimental investigation and simulation of machining thin-walled workpieces

An enhanced simulation model is presented in this paper to predict form deviations in end milling processes of thin-walled structures. The calculation of tool engagement is based on level curves representing surface geometry of the workpiece and the NC code driven sweep volume. To consider influences of force-induced deflections resulting in static form errors on machined surface of the workpiece, a model for superposed stresses is enclosed. Derived from the tool engagement, the cutting force is predicted using a parametric force model. The experimental investigations within the measuring of static and dynamic form errors during processing and afterwards are shown and measurement results are compared with results of the cutting simulation to verify the proposed method. The presented achievements are deduced from research activities aiming at an increased understanding of shape deviation induced by interactions between tool, workpiece and clamping device during machining.     

The influence of the cutting tool microgeometry on the machinability of hardened AISI 4140 steel

The aim of this work is to define the cutting conditions that allow the dry drilling of carbon fiber reinforced epoxy (CFRE) composite materials taking into consideration the quality of the drilled holes (the exit delamination factor and the cylindricity error) and the optimum combination of drilling parameters. A further aim is to use grey relational analysis to improve the quality of the drilled holes. The machining parameters were measured according to 3³ full factorial parameter designs (27 experiments with independent process variables). The experiments were carried out under various cutting parameters with different spindle speeds and feed rates. Drilling tests were done using WC carbide, high-speed steel (HSS), and TiN-coated carbide drills. The experiment design was accomplished by application of the statistical analysis of variance (ANOVA). Results show that the thrust force is mainly influenced by the tool materials and the feed rate, which has a strong influence on the exit delamination factor. On the other hand, the spindle speed particularly affects the cylindricity error of the holes. Correlations were established between spindle speed/feed rate and the various machining parameters so as to optimize cutting conditions. These correlations were found by quadratic regression using response surface methodology (RSM). Finally, tests were carried out to check the concordance of experimental results.     

Development of an advanced micro-positioning system for increasing operation accuracy: consideration of high pressure sealing

This paper presents the development of a micro-positioning system for the increase of operation accuracy of machine tools. A highly dynamic piezo-actuated micropump coupled with a hydraulic cylinder transforms small strokes of the piezoelectric actuator into a continuous piston movement. Fast-switching active valves direct the volume flow. Crucial for the functionality of the pump module is the sealing function of the membrane to isolate the piezoelectric actuator unit against high pressure fluid. Therefore, the requirements for foil membrane selection are investigated by means of a developed test bench. It is demonstrated that a successful test of foil membrane materials provides a closer insight into the entire valve characteristics.     

Condition based maintenance planning of highly productive machine tools

The competitiveness of producing enterprises in high-wage countries is extremely dependent on the productivity of the production line. Consequently, the availability of machines displays an essential index. The aim of the research project ??Make-it?? (Condition Based Maintenance Planning of Highly Productive Machine Tools) was to improve the availability of machine tools. Therefore, within this joint project, new methods and approaches for condition based maintenance were investigated. Thereby, an important objective was to develop an innovative maintenance algorithm which enables to calculate the most cost-effective maintenance times based on a continuous prognosis of the remaining life time, maintenance costs, and potential failure costs. This paper describes the results of the developed maintenance approach. Within this paper, the fundamental mathematical foundations of the innovative, cost-oriented maintenance algorithm and the use of the data of machine condition are presented in the first part. Moreover, the implementation of the algorithm in a computerized maintenance management system is described. The validation of the cost-oriented maintenance planning by means of event-oriented simulation will also be part of this paper.     

Process stabilization with an adaptronic spindle system

For economical reasons it is necessary to reduce the machining time and to increase the process automation. This leads to the need for fast machine tools with high process stability in order to enhance the material removal rate. However, the machine often does not limit the process stability but the tool because of its compliance. This paper presents a new possibility of expanding the stable process range of long and slender end mills with an adaptronic spindle system. The system is able to position the spindle dynamically in the range of microns with three piezo actuators. In order to disturb the regenerative effect, which leads to an instable process, the chip thickness is modulated by a dynamic spindle actuation. This is realized by a superposition of vibrations of the tool in feed direction. In milling tests the degree of stabilization is verified for different superpositions. Hence, the stable process range could be improved for spindle speeds up to 5,000?rpm.