Abstract: Three kinds of typical concrete materials were tested involving cement concrete, steel fiber reinforced concrete and ferroconcrete. The 3-direction cutting forces acted on the diamond sawblade were measured with varied cutting speed, feed speed, depth of cut and diamond segments. The measurements show that during the whole cutting process, the curve of cutting forces fluctuate intensely, which indicate the differences of the cutting process of heterogeneous mixture of the
concrete. Because of the larger amplitude, the average values of cutting forces are much smaller than that of peak values. The cutting forces increase with the increase of feed speed, in reverse, decrease with the increasing of cutting speed. When the strength grades of the concrete materials are the same, the cutting forces of ferroconcrete and steel fiber reinforced concrete show the higher value than those of cement concrete. The cutting forces of sawblade with brone-cobalt based bond are greater than those of sawblade with cobalt based bond in sawing concrete process. Adding cobalt content in matrix, the cutting force can be decreased when sawing cement concrete. While sawing steel fiber concrete and ferroconcrete, the cutting forces can be decreased by reduction of cobalt content and increase of iron content in matrix.
Abstract: In this paper, a single-pulse discharge experimental device has been developed to study the mechanism of high speed small hole EDM drilling. It is found that the emulsion used in high speed small hole EDM drilling as dielectric fluid is easier to be broken down than the kerosene which is always used in the traditional EDM. The injection flushing is contributive to the ejection of molten material in the crater produced by discharge, and can greatly improve the evacuating condition.
Additionally, the effective quenching ability of emulsion and injection flushing can greatly reduce the necessary pulse interval and increase the effective pulse frequency.
Abstract: There is a bright future for hard cutting technique because of good machining flexibility, high efficiency, no pollution. This paper presents effect rules of cutting parameters (cutting speed, feed, depth of cutting) on integrality of machined surface (surface roughness, surface hardness, surface hardened depth, residual stresses, surface texture) based on orthogonalization test. Optimal cutting parameters are selected according to these rules. Surface roughness (Ra) is up to 0.6µm in terms of selected optimal cutting parameters.
Abstract: A theoretical model of two-dimensional active control for ambulance stretcher
suspension is proposed. The shaping filter equations of time domain are developed to provide optimal estimates of the disturbance dynamics. Numerical calculations are carried out to examine the effectiveness of proposed control scheme. It shows that the optimal control with disturbance feed-forwarded provides significant reduction of vertical and pitch vibration transmission compared with the passive stretcher suspension. The relative displacement and resonance peak values of vibration components in the sensitive frequency range of human body are effectively suppressed in comparison with that of the 1-DOF active control stretcher.
Abstract: ELID grinding is widely used as a high-productivity and super-precision grinding method for hard and brittle materials. It continues grinding stably with metal bonded diamond wheel due to its in-process dressing. Magnetorheological finishing (MRF) is a novel precision finishing process for hard and brittle materials. In this paper, ELID grinding and MRF are adopted to get high surface quality and remove subsurface damage of hard and brittle materials. The results show that this combination gives attention to both efficiency and quality and can be used to replace conventional optics manufacturing.
Abstract: In this paper, 3mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) and
TiN/3Y-TZP(adding TiN particles to 3Y-TZP) composites were fabricated by hot-pressing technique. Phase composition, microstructure and mechanical properties of the composites were investigated. It is shown that the flexural strength, fracture toughness and Vickers hardness of TiN/3Y-TZP was significantly improved by the addition of TiN particles compared with 3Y-TZP. The flexural strength of ZYT2 (20wt% TiN addition) is 1318 MPa. The fracture toughness of ZYT4 (40wt% TiN addition) is 16.8MPa·m1/2. The toughening and strengthening mechanisms were analyzed. The XRD results show that the additing of TiN can hinder the transformation from tetragonal phase to monoclinic phase of 3Y-TZP during fabrication process.
Abstract: STEP-NC is a new CAM/CNC interface and an extension of STEP into numerical control machining. It has been partly formed into draft international standard (ISO 14649) and is expected to replace ISO 6983 in the near future. In the first section of this paper, the STEP-NC data model is analyzed and those parts that are relevant to NC milling process are abstracted. Then issues involved in NC part machining based on STEP-NC paradigm are discussed including NC programming and the machine control. Based on the analysis, a prototype system is outlined and partly developed with libraries and software tools in ST-Developer environment to interpret the part program into internal data format and to assist the shop floor level planning. Finally the user interface of this system is introduced.
Abstract: A new model for predicting the small-crack growth rates is proposed under the constant amplitude loading. With the use of two important parameters, the transition crack length a0 and the barrier characteristic parameter d*, the new model can reflect the abnormal feature of small-crack growth. The effect of crack closure is considered in the model as well. The model is shown to provide a better correlation to the experimental results for the Ti-6Al-4V alloy under various stress levels at a stress ratio of R = 0.4.
Abstract: In this paper, on the basis of the conception of symmetric fuzzy number and linear
planning theory as well as the maximum-minimum and mean values of the measured cutting force, two fuzzy prediction models of cutting force uncertainty are constructed. The test results show that the proposed fuzzy models can validly predict the variation ranges of cutting force uncertainty for the given cutting conditions, and better express the uncertainty of cutting force than the empirical model from the least square regression.