Journal of Mechanical Working Technology最新文献

Preliminary machinability studies on the newly developed nickel-aluminide alloys are presented. Machining was conducted on a rigid, high-speed turning center using a variety of ceramic cutting tools, feed rates, depths of cut and cutting speeds. The results of these studies are presented.

It is observed that the optimum cutting for these alloys is very sensitive to the various combinations of the cutting parameters, and that the tool-life does not always decrease as the cutting speed increases, as might be expected. Rather, there are certain cutting speeds at which the tool life is significantly greater than the values for lower cutting speeds.

In this paper a numerical solution of strip rolling based on finite element method is presented. The material behavior in the form of a stress-strain curve obtained from a plane-strain compression test and measured interfacial velocities as prescribed boundary conditions are used as input data to the numerical model of strip rolling. Numerical results such as distributions of roll pressure, frictional stress, and coefficient of friction in the contact region are presented.

Utilizing inertial energy storage the homopolar generator (HPG) is capable of delivering multimegawatt, megampere current pulses into resistive or inductive loads with high efficiency. (1) Such HPG's have been used for many years as power supplies for research in pulsed processing of metal alloy components and systems. Most of these processes rely on extremely rapid thermal excursions in the workpiece(s) caused by resistive heating during the current pulse. A new application of pulsed HPG's that carries great promise is homopolar pulse consolidation (HPC) of powder metal alloys or components.(2) In HPC, powder metal constituents are loaded into a thermally and electrically insulated die, then precompacted to an initial pressure. the “rams” of the compaction press are also the electrodes for homopolar discharge current. While in single residency, the powder compact is heated uniformly by HPG discharge current, sintering occurs, and consolidation is accomplished by hydraulic control of the consolidation press. The process is completed in approximately one sec, with unaided cooling to room temperature on the order of 100 sec, depending on compact mass. Microstructural control is closely tied to beginning particle size and distribution. Traditionally unsinterable alloys have been consolidated using HPC. Novel intermetallic alloys and phases have been produced. Cermets and other composites can be produced, as long as the continuous matrix is conductive. New tooling designs allow for controlled atmospheres, near-net shapes, and automated manufacturing.

Model-based control method using second-order models may be insufficient for fast digital control of robots. Therefore, a model-based control using a third-order dynamic model is introduced. It is shown that this scheme may be implemented in real-time by means of an efficient recursive algorithm. The temporal arrangements of this algorithm are discussed and a controller implementation is proposed.

Geometric modeling systems are rapidly replacing manual drafting techniques for defining the geometry of mechanical parts and assemblies. This makes possible the development of a variety of software tools to aid the designer in effective representation and evaluation of mechanical systems and assemblies (MSA's). The long term goal of our research is to address the question: Can the given MSA be assembled automatically with the given facilities? In order to accomplish our goal we need to develop techniques to model the Mechanical System/Assembly (MSA) and the available facilities. In this paper, we address the first part of our goals and develop a methodology to automatically determine the assembly sequence from a 3-D solid modeler description of the assembly. Our approach consists of automatically determining a set of assembly operations, through a disassembly procedure, that lead to the given assembly (MSA). We use the Noodles Solid Modeler, that has been developed at Carnegie Mellon, to describe the assembly. We have implemented our algorithm to determine the disassembly sequence on a SUN workstation in C language. We also describe our initial implementation through an example.