Showing papers in "Materials and Manufacturing Processes in 1986"
TL;DR: In this article, a quantitative model considering signal attenuation and tool flank wear is proposed to describe the influence of machining process parameters on the level of acoustic emission (AE) generation.
Abstract: A quantitative model considering signal attenuation and tool flank wear is proposed to describe the influence of machining process parameters on the level of acoustic emission (AE) generation. The AE sensitivities to width of cut, feed rate, and hardness of material in three-dimensional cutting are experimentally studied. The application of AE signal analysis to chip formation detection, providing information for process control in unattended machining, is described.
28 citations
TL;DR: In this paper, the same 3-D solid model and finite element modeling tools used by the designer, coupled with powerful analysis simulation tools to predict the transient nonlinear heat transfer and plastic material flow found in many manufacturing processes, are used to explore alternative processing plans, evaluate trade-offs and even influence the design to produce superior products.
Abstract: As America refocuses its attention on the factory, design and manufacturing engineers must work together closely to design the appropriate products, and matching production process in a team effort. By building off the designer's CAE tools that predict product performance, the manufacturing engineer is today able to simulate the proposed production process. Process simulations for the following manufacturing processes are available or being developed: ▪Forging, ▪Machining, ▪Injection Molding, ▪Die Casting, ▪Investment Casting, ▪Metal Forming, ▪Heat Treating, ▪Assembly Tolerancing By utilizing the same 3-D solid model and finite element modeling tools used by the designer, coupled to powerful analysis simulation tools to predict the transient nonlinear heat transfer and plastic material flow found in many manufacturing processes, the manufacturing engineer is able to explore alternative processing plans, evaluate trade-offs and even influence the design to produce superior products. Process simula...
26 citations
TL;DR: In this article, a theoretical model for the nucleation of microcellular foams in thermoplastic polymers has been developed and experimentally confirmed, which explains the effect of various additives and processing conditions on the number of bubble nucleated.
Abstract: Microcellular polymer foams exhibit greatly improved mechanical properties compared to standard foams due to the formers' small bubble size. Typical microcellular foams have bubbles with diameters on the order of 10 microns and volume reductions of 30 to 40%. The presence of these bubbles acts to increase the impact strength of a microfoamed structure to six or seven times that of solid parts of the same linear dimensions due to crack blunting and increased craze initiation in the cell walls. The first step in designing techniques to manufacture parts of microcellular foam is a complete understanding of the bubble nucleation process. To this end, a theoretical model for the nucleation of microcellular foams in thermoplastic polymers has been developed and experimentally confirmed. This model explains the effect of various additives and processing conditions on the number of bubble nucleated. At levels of secondary constituents below their solubility limits, an increase in the concentration of the...
23 citations
TL;DR: In this article, a remeshing program based on the area-weighted-average technique was developed and tested by simulating forging of the flange-hub shape, and detailed deformation characteristics for the different preform shapes under the two frictional conditions were obtained.
Abstract: Axisymmetric forging of powdered-metal preforms was analyzed by the finite element method neglecting the effect of temperature on deformation. A remeshing program based on the area-weighted-average technique was developed and tested by simulating forging of the flange-hub shape. Then the analysis was performed for forging of a pulley blank. The detailed deformation characteristics for the different preform shapes under the two frictional conditions were obtained. A comparison between the prediction and the experiment regarding proper preform design to forge defect-free pulley blank demonstrates that the finite element analysis is useful for further developments in preform design in powdered-metal forging.
16 citations
TL;DR: The Cranfield Unit for Precision Engineering (CUPE) specializes in the design, development, and construction of advanced, high precision CNC machines of many types as discussed by the authors, including diamond turning machines.
Abstract: The Cranfield Unit for Precision Engineering (CUPE) specializes in the design, development, and construction of advanced, high precision CNC machines of many types. Two years ago, the British Science & Engineering Research Council (SERC) commissioned CUPE to develop and commission an ultra-precision CNC diamond turning machine for the manufacture of X-ray telescope mirrors up to 1400 mm in diameter and 600 mm in axial length. This vertical axis machine incorporates many novel design and manufacturing features. This paper describes the design and manufacturing philosophies and techniques used in bringing it to its present successful level of development.
14 citations
TL;DR: In this paper, the effects of die width and reduction on the closing of a void were investigated. But the authors focused on the first two factors and reported the results of a study on the effects.
Abstract: In the manufacturing of heavy forgings, one of the most important aspects of the process is the consolidation of internal voids which result from the ingotmaking process. To insure a good quality finished product, these voids must be closed by proper choice of forging practices - including such factors as die geometry* amount of reduction, reduction speed, and workpiece temperature. This paper focuses on the first two of these factors and reports the results of a study on the effects of die width and reduction on the closing of a void. The deformation state in the cross-section of an ingot is predicted using a two-dimensional elastic-plastic finite element code for large strain, large deformation analysis. Simulations of forging with no void present are reported and compared with results from plasticine experiments. The effects of die width and amount of reduction on the internal deformation state are examined. A single internal void is then modeled in the same geometry ingot as a smooth cavity a...
12 citations
TL;DR: In this paper, a finite element formulation for deformation of porous materials including compressibility of the material and the effect of temperature was developed and applied to the problem of plane-strain compression of sintered iron-powder bars.
Abstract: The finite element formulation for deformation of porous materials including compressibility of the material and the effect of temperature was developed and applied to the problem of plane-strain compression of sintered iron-powder bars. The formulation employed a phenomenological approach for the deformation analysis. A simple linear relationship between the thermal conductivities of the powdered metal and the base metal was derived and used as a first approximation for temperature calculations. The computed results are compared with experimental values in terms of macroscopic densification and forging pressures. Also, the predicted relative density distribution was compared with the experimental hardness distribution. The results show that the finite element analysis simulates the compression process well and predicts the sites of fracture during deformation.
9 citations
TL;DR: In this paper, the various sources of tool path error are discussed as functions of machine tool positioning errors and cutting force errors which are characterized as static, dynamic and stochastic.
Abstract: Thin rib machining of electronic components or airframe structures can benefit from high speed machining for burr free cutting, improved surface quality and increased metal removal rate. It is suggested that the use of a magnetic bearing spindle can not only successfully provide the benefits of high speed machining but, more importantly, minimize tool path errors. In this paper the various sources of tool path error are discussed as functions of machine tool positioning errors and cutting force errors which are characterized as static, dynamic and stochastic. The operation of high speed magnetic bearing spindles is described and a control scheme whereby the spindle may be translated and tilted for minimizing tool path errors is discussed. This overall research activity is a cooperative effort between the University of Maryland, Cincinnati Milacron, Magnetic Bearings, Inc., The Uestinghouse Corporation, and The National Bureau of Standards.
6 citations
TL;DR: In this paper, a finite element method (FEM) mesh is produced for the pattern of the part, using geometric modeling techniques to reduce the size of the heat transfer problem by replacing the FEM mesh in the mold material by appropriate boundary conditions on the surface of the casting.
Abstract: A comprehensive technique is described for performing the simulation of the solidification of foundry castings. A finite element method (FEM) mesh is produced for the pattern of the part, using geometric modeling techniques. Results are presented to demonstrate selection rules for the mesh size. The size of the heat transfer problem is reduced by replacing the FEM mesh in the mold material by appropriate boundary conditions on the surface of the casting. The boundary conditions are found automatically by a program which relates local surface curvature on the part to a pre-calculated library of solutions. Methods for ensuring that all of the latent heat of fusion is included are presented, and comparisons are made between different solution methods.
6 citations
TL;DR: In this paper, the authors presented the solutions to the stochastic differential equations which mathematically represent the machine tool workpiece system in BTA deep hole machining, assuming an appropriate model for the tool-workpiece interaction, and the machine-tool work-piece system.
Abstract: This paper presents the solutions to the stochastic differential equations which mathematically represent the machine tool workpiece system in BTA deep hole machining. The stochastic differential equations are derived assuming an appropriate model for the tool-workpiece interaction, and the machine tool work-piece system. The solutions to the non-parametric inhomogeneous differential equations are obtained using the Fokker-Planck equations. Based on these solutions, the true motion of the tool tip has been described using the maximum, average, and minimum error curves. Also, using the statistical description of the true motion, equations are derived which mathematically describe the CLA and RMS value of the surface produced. Based on these results, it is seen that the CLA and RMS value of the given surface vary 1n a given band depending upon certain machining paraj meters. The measurement of the surface texture of the specimens shows that the experimentally measured CLA values agree reasonably we...
4 citations
TL;DR: Several parallel paths are being pursued in the further development of grinding processes on the one hand, since higher material removal rates are to be realized, machines of greater rigidity with more efficient drives and tools are required On the other hand, increasing demands are placed on the quality of machined parts as discussed by the authors.
Abstract: Several parallel paths are being pursued in the further development of grinding processes On the one hand, since higher material removal rates are to be realized, machines of greater rigidity with more efficient drives and tools are required On the other hand, increasing demands are placed on the quality of machined parts One trend is towards the utilization of super hard abrasives such as cubic boron nitride (CBN) Advantages of this grinding material as opposed to the conventional corundum are significantly greater hardness and, therefore, longer profile life, higher material removal rates, and lower grinding temperatures One disadvantage is the price of the tool, which is several magnitudes higher than for corundum Considering the high initial costs for CBN cutting material, destruction of the wheel caused by faulty operation of the machine or undue allowance must have the aim of transferring supervision and control tasks from the operator to the machine control Fundamental for this conc
TL;DR: A general method for the design, analysis and optimization of mechanical press linkages, where the linkage type must be identified, and geometrically proportioned to approximately satisfy the mecnanical requirements.
Abstract: This paper presents a general method for the design, analysis and optimization of mechanical press linkages. In order to use the method, the linkage type must be identified, and geometrically proportioned to approximately satisfy the mecnanical requirements. Next, system equations must be derived for that linkage, which describe input/output relationships for displacement and force. Upon completing these two steps (which typically must be done in any case), the method can then be employed to optimize that linkage for the particular application.
TL;DR: In this article, the design, development, and application of ultra-precision CNC machines for the single point diamond turning of non-conventional metal optical components (Al, Ge, etc.) was described.
Abstract: The design, development, and application of ultra-precision CNC machines for the single point diamond turning of non-conventional metal optical components (Al, Ge, etc. ) the diamond grinding of ferrite and, other ceramic components for magnetic disc flying heads, etc. is described. In both cases, tolerances on workpieces in the order of ± 0·1 μm were specified and achieved, together with the overriding need to minimize degenerated surface layers, i.e. surface damage. The effects of chip formation at low depths of cut are discussed. The factors affecting the depths of “damaged layers” formed in turning and grinding are mentioned. Typical advanced technology components for which ultra-precision diamond turning or grinding are widely used are: Convex mirrors for high output C02 laser resonators X-ray mirrors infrared lenses in germanium for thermal imaging systems scanners for laser printers. and drums for copiers elliptical mirrors for YAG laser beam collectors spherical bearing surfaces in beryll...
TL;DR: In this article, a new model for predicting forming limits for strain rate sensitive materials relying on the above work and the approach of Marciniak was presented and the results obtained are found to be in close agreement with experimental values.
Abstract: Rao and Chaturvedi [18] had presented an analysis to consider the effect of thickness on the forming limit diagrams through a correction in the MK model taking into consideration the influence of the triaxial stress state in the neck. This model predicted results closely matching the experimental values for Aluminium which is not sensitive to strain rate. This paper presents a new model for predicting forming limits for strain rate sensitive materials relying on the above work and the approach of Marciniak. Kuczynski and Pokara [13]. The results obtained are found to be in close agreement with experimental values (Pig. 4). The model has also been used to analyse the influence of various material property parameters and thickness on forming limits and these are also found to be in good agreement with reported experimental results. The model has also been extended to predict forming limits under a two stage strain path and the results have been compared with the experimental results of Ishigaki [8]...
TL;DR: In this paper, a computer model is developed to simulate the electro-magnetic and heat-transfer behaviors of the taper heating process, and a feasibility study of two induction furnace designs is presented.
Abstract: A computer model is developed to simulate the electro-magnetic and the heat-transfer behaviors of the taper heating process. The computer-aided tool can provide the necessary information for design and operation of induction furnaces for taper heating required for isothermal extrusion. A feasibility study of two induction furnace designs is presented. Computer results indicate that the three-zone type furnace can provide the desired taper temperature profiles for the aluminum and the titanium alloys considered. Applications of the computer tool to other types of induction heaters are also discussed.
TL;DR: In this article, the prevailing state of stress, temperature and time in powder metallurgy processes are investigated, since these dictate densification mechanism(s), and hence microstructure and properties.
Abstract: Powder metallurgy is a source of new and viable near or net shape manufacturing processes, with compelling economic and technical advantages over conventional ingot metallurgy practice. Selected commercial methods are considered, namely pressing and sintering, injection molding, powder preform working and direct powder consolidation. Particular attention is directed to the prevailing state of stress, temperature and time in each mode, since these dictate densification mechanism(s), and hence microstructure and properties.
TL;DR: In this paper, the welding of aluminium using laser beam technology, verifying only the feasibility of the joint from metallurgic and mechanical points of view, was presented, and the results showed that the high level of specific power and the restricted area involved put laser technology in the position of being one of the most interesting technologies for welding of aluminum.
Abstract: The physio-chemical characteristics of aluminium are cause of considerable difficulties in the welding of this material. Even if the technological level reached with traditional technologies for some types of alloy makes it possible to obtain joints with structures meeting or exceeding required standards, the high amount of heat involved and the high coefficient of expansion of the material are- cause of considerable distortions in the manufacturing process.The greater the concentration of energy (with consequent high work speeds), the greater the geometrical distortion of the workpiece. The high level of specific power and the restricted area involved put laser technology in the position of being one of the most interesting technologies for the welding of aluminium.In the present research, the aim has been to approach the welding of aluminium using laser beam technology, verifying only the feasibility of the joint from metallurgic and mechanical points of view. Subsequently, in relation to the r...
TL;DR: In this paper, a laser rheology processing (LRP) machine is proposed, where lasers are used as a fabrication tool and rheological powder as input are used, and merits, feasibility, results of a fundamental experiment, and conceptual design of an LRP machine are discussed.
Abstract: Great advances have been made in laser technology in recent years. Near net shape manufacturing technology, on the other hand, has attracted attention to the products of expensive and difficult-to-machine materials. It is in this context Laser Rheology Processing (LRP) is proposed, where lasers as a fabrication tool and rheological powder as input are used. In this paper, merits, feasibility, results of a fundamental experiment, and conceptual design of an LRP machine are discussed.
TL;DR: Two convenient and meaningful variables, exergy and entropy, can be used for modelling such systems and prove that the previous investigations into the surfaces participating in surface interfaces may contribute general solutions to this subject.
Abstract: In this investigation, a new concept of surface interfaces in engineering systems is proposed. Various surface interfaces have been examined in order to reveal the physical meaning and importance of combining elements. Two convenient and meaningful variables, exergy and entropy, can be used for modelling such systems. The statistical nature of these variables prove that the previous investigations into the surfaces participating in surface interfaces may contribute general solutions to this subject.
TL;DR: The basic tools of optics consist of a classical family containing lenses, scales, interferometers, and the myriad of instruments that make use of them as discussed by the authors, and their usefulness has been greatly enhanced recently by the addition of lasers as a light source, electronic detectors as replacement for the human eye, and computers to rapidly process results.
Abstract: The basic tools of optics consist of a classical family containing lenses, scales, interferometers, and the myriad of instruments that make use of them. Their usefulness has been greatly enhanced recently by the addition of lasers as a light source, electronic detectors as replacement for the human eye, and computers to rapidly process results. A new tool has been the introduction of optical fibers — which is beginning to establish a new family.
TL;DR: In this paper, the effects of machining on the topographical, the mechanical/physical and the metallurgical properties of the surface and subsurface layer for the face milling operation using tungsten carbide cutting tools is discussed.
Abstract: With the rapid developments taking place in the electrical and electronic industries, soft magnetic materials are finding increasing application. Degradation of machined surfaces due to the mechanisms of surface formation when machining under geometrically defined cutting conditions lead to a corresponding deterioration in the magnetic properties of soft magnetic nickel-iron alloys. Graphical simulation techniques have been applied in order to study the interactive mechanics associated with the single point machining operation. Both the outcome of this simulation as well as the conclusions of experimental investigations into the milling of the soft magnetic nickel-iron alloy MUMETALL are the subject of this paper. The influence of machining on the topographical, the mechanical/ physical and the metallurgical properties of the surface and subsurface layer for the face milling operation using tungsten carbide cutting tools is discussed.