The Dynamic Data System (DDS) methodology has been successfully used for machine tool structural analysis. In this paper, the digital filtering technique is proposed to reduce the adequate order of the Autoregressive Moving Average Vector (ARMAV) moel to overcome the difficulty in higher order modeling.
A model for analysing temperatures in free oblique cutting with sharp cutting tools is developed by utilising a recent solution for temperature distributions on a rectangular heat source moving obliquely on a semi-infinite conducting medium. The source obliquities introduced at the shear and rake planes by the tool obliquity are identified and a procedure is developed to compute the temperature distributions and heat partition coefficients at the shear and rake planes. For mild steel cut by a H.S.S. tool, the mean tool-chip interface temperature estimated by the new model is in close agreement with that measured by the tool-work thermocouple method. It is noted that the introduction of tool obliquity results in temperature and heat partition coefficient distributions which are essentially similar to those obtained in orthogonal cutting. The mean tool-chip interface temperature is found to decrease with increasing tool obliquity.
By the mapping method the relevant planes and straight lines of a cutting tool can be mapped on a projection plane, and then all the angles of the cutting tool in both tool-in-hand and tool-in-use systems can be determined by a simple plane geometric procedure. The advantage of this method is that the effects of various parameters concerning the structure, mounting and motion of a cutting tool on its geometric angles can be intuitively shown. This will make it easier to synthesize and optimize these parameters from the point of view of cutting performance. Furthermore, it is possible to use this method for man-machine interaction in CAD and CAM of complicated cutting tools.
This paper studies the conditions for the superplasticity of two CuZn alloys. Tests have been made with commercial HPb 59-1 brass bar and H62 brass bar, which were machined into tensile specimens. Then the specimens were subjected to heat treatment in order to meet the requirement of fine microstructure for superplasticity. Tensile tests have been carried out at different temperatures and tensile rates on a mechanically-operated high-temperature material testing machine.
Closed die cold forging is an important industrial metal forming process used extensively in the manufacture of headed fasteners. In this paper an upper bound solution is presented based on observed velocity fields resulting from the deformation of initially cylindrical workpieces within hexagonal and square dies. The influence of workpiece aspect ratio, forging loads and friction conditions on the fill-out of the hexagonal and square dies is examined. It is shown that at high die fill-out, friction conditions and workpiece aspect ratio have little influence on the forging pressure ratio. The surface stress state, produced by relative movement between workpiece and punch/die, is examined with the aid of microhardness measurements.
Cracks which progress across the vertical and horizontal plane section of forging dies appear to be caused by stress concentration. This paper reports an investigation into the relationship between the working pressure and the induced stresses distribution of the die during the process.
Large deformation behaviour of aluminium and low carbon steel short cylinders of various diameters and height to diameter ratios, loaded axially in a simple compression test without using any lubricant, is examined. Typical histories of deformation of the cylindrical surface and the end face are presented with a view to studying the nature and the extent of free surface barreling, its folding into the end face and effects of specimen size thereon. The results reveal that the profile of a deforming specimen can sensibly be approximated by an arc of a circle only after the onset of folding.
Experiments have been carried out on lead and copper cylindrical billets using simple extrusion forging dies under quasi-static and dynamic conditions to produce boss and flange type components. It was observed that during the initial stages of the deformation process, the flow pattern of the metal is significantly different to what is normally assumed in theoretically analysing the process. The profile of the flange becomes very much tapered and the height of the boss obtainable is dependent on the boss to billet dimensional ratio.
The authors aim to improve the reliability and speed of workpiece shape prediction for electrochemical machining. A review of some previous mathematical modelling work is followed by a resume of the Boundary Element Method. Linear and quadratic elements are used herein to represent the boundaries and, because the workpiece shape changes as machining progresses, an automatic re-noding procedure is adopted after each iteration. The effect of element and time step size on the accuracy of the workpiece profile is studied, accuracy being measured by comparing converged parts of the workpiece shape with exact equilibrium solutions. The paper reveals considerable promise for boundary element simulation particularly when it is reasonable to assume that homogeneous physical conditions exist in the inter-electrode zone.
Models available in the literature for the prediction of shear angle, φ, during longitudinal turning with constant underformed chip thickness do not apply for the case of accelerated cutting (i.e. facing and taper turning).
A compensatory control system for a moderately accurate cylindrical grinding machine was simulated to investigate the amount of possible improvement of the workpiece roundness for a plunge cylindrical chuck grinding operation. Parametric transfer functions of the drive system of the compensatory controller and of form accuracy were identified by employing an autoregressive moving average vector modeling methodology. It has been shown that the workpiece roundness can be improved up to 90 per cent by compensating the work spindle radial error motion at the grinding position.
Modelbases and product models are essential for integrated data processing in a company. Design data, process planning data and administrative data have to be put together to give a pool of information for one particular product. Therefore the existing CAD/CAM-systems have to be increased concerning their capabilities of storing and retrieving product information and their functional equipment and efficiency. The paper describes the concepts and first results of a methodbase system and the included product models.
The paper presents the results of studies of the stereometry of the cutting wedge of a new design of a turning tool without a nose and relations characterizing the geometry of the underformed chip. The main directions of the effect of stereometry of the tool called a single-edged turning tool on basic parameters of the state of the surface layer have been determined.
Forging spur gear forms in completely closed cavity dies is investigated by means of an upper bound analysis. A velocity field comprising three unit deformation regions is proposed. The tooth regions are approximated by prismatic rectangular sections. The effects of root diameter, number of teeth and workpiece/die interface friction, on flow and forging pressures, are determined.
Ultrasonic machining is used for machining hard and brittle materials. The mechanism of removal is complex but it is generally accepted that for non-porous materials the mostimportant constituent processes are the direct hammering of abrasives by the tool and high velocity impact of free moving abrasive particles on the work surface. This paper deals with a simple but effective approach using a profile relocation technique to study the relative role of the two processes. A mild steel tool was used with boron carbide abrasive to machine high speed steel, tungsten carbide and plate glass workpieces the design of which enables the two processes to be separated. Removal is found to be primarily by hammering.
The paper reports on an investigation into the various aspects of cold forging of iron powder preforms which have been compacted and sintered from atomised iron powder. The influence of particle size, compacting pressure, sintering temperature and forging parameters on relative density of the preform was investigated. Experiments were conducted and measurements were made on the development of barrelling and strain variations at the free surface. Cracks were also observed at the free surface of the perform. The deformation characteristics and fracture mechanism is discussed critically to illustrate the interaction of various parameters involved and the results are presented graphically.
Membranes for gas-solid separation were prepared by using short fibres as starting materials. A suitable viscosity and solid content for the coating suspension were determined to be 66–75 mPa·s and 10–12.5%, respectively. The observation by scanning electron microscopy shows that the short fibres cover the entire surface of the support uniformly. The filter resistance and the value of the fine particulate matter (VFPM2.5) were studied. The baseline filter resistance of the membrane (288.1 Pa) was lower than that of the membrane prepared by using alumina powder (366 Pa). The value of the fine particulate matter (VFPM2.5) was 60 μg/m3, which meets the emission standard of GB3095-2012 (35–75 μg/m3). These results demonstrated that the membrane prepared with short fibres shows higher filter efficiency and better regeneration performance.
A grinding wheel wear equation is identified by the GMDH (Group Method of Data Handling) algorithm with successive determination of polynomial trends containing interactive terms, considering chemical compositions and mechanical properties of work materials, abrasive grain, grain size, grade, wheel speed and feed. The established model enables the grinding to be predicted for all combinations of work materials, grinding wheels and grinding conditions, and serves as an aid in the optimization of the grinding process.
An upper-bound method is applied to determine the forging load and the deformed configurations during upset forging of elliptical disks. A simple kinematically admissible velocity field for three-dimensional deformation is presented which takes into account the lateral sidewise spread as well as the bulging along thickness. From the proposed velocity field the upper-bound load and the deformed configuration are determined by minimizing the total power consumption with respect to two chosen parameters. Experiments are carried out with annealed AISI 1015 steel billets at room temperature for different elliptical shapes and lubrication conditions. The theoretical predictions both in the forging load and the deformed configurations are in good agreement with the experimental results.
The hot and cold rolling and cold drawing processes are used in steel profile production to obtain special profiles with high levels of dimensional accuracy and quality. The wide range of applications and the variety of shapes lead to thousands of profiles. There is a need to classify and to codify shapes in order to reduce the time to design and to manufacture the profile tools. Pattern recognition has been used in this study and a method based on multiple circles-boundary intersection and form factor description is presented which is particularly suitable to steel profile production. The implementation of the method has shown that productivity is increased in the full design-through-manufacturing cycle. Furthermore, the computer aided retrieval of old shapes helps design standardization and reduces design proliferation and unnecessary part duplication.
