A novel concept for the manufacture of individual sapphire-metallic hip joint endoprostheses.

At the present time, artificial joints made with metallic, ceramic, metal-polymeric or ceramicpolymeric friction pairs substituting for the natural biomechanic articulations "head of the hip joint-acetabulum" are widely used for endoprosthetic operations on hip joints. Experience gained in the course of more than 2000 operations has shown that along with the advantageous properties of modern endoprosthetic constructions made of metal, ceramics and polymers, they have certain drawbacks. Among them are insufficient biological inertness and susceptibility to excessive wear of the friction pair components. In addition, as a result of wear of the hinge friction pair, toxic and oncologically dangerous products of degradation accumulate in the different organs and tissues. This in turn results in severe complications and demands correspondingly complicated corrective intervention, often leading to worse disability than that which the original operation was designed to cure. The aim of the study reported here was the development and clinical validation of a highly effective and long-lived hip joint endoprosthesis with a sapphire head whose wear capacity is superior to all others. The endoprosthesis consists of a metallic pedicle, a dismountable articulation (metallic necklayer of supramolecular polyethylene-sapphire head) and an acetabular cup. The endoprostheses with the sapphire head proved themselves positively in clinical trials and are considered to be highly promising for future applications

Simulation of effects of metal phase in a diamond grain and bonding type on temperature in diamond grinding

Manufacturing diamond wheels on various bonds is a relatively high-cost process, requiring high labour and high consumption of expensive diamond grains but yielding relatively low productivity. With better knowledge of the various factors involved in the sintering process, the most efficient combinations can be found, leading to higher productivity. Currently, there are no scientifically based recommendations for the choice of the rational combinations of strength, brand of grain, graininess and concentration with the physical–mechanical properties of bonds. The aim of this research is the development of a technique for the theoretical definition of an optimal combination of strength properties of diamond grains and bond to provide maximum retention of diamond grain integrity during the process of diamond wheel manufacture. This is investigated using 3D simulations of the deflected mode of the sintering area of the wheel's diamond bearing layer

Mathematical simulation of motion of working medium at finishing-grinding treatment in the oscillating reservoir

The results of mathematical simulation have been carried out for the pattern of working medium motion providing the technological process of finishing–grinding treatment in an oscillating reservoir. With use of physics laws, it is ascertained and grounded that the flow of granules at the plane wall of reservoir is travelling oppositely to the source of vibrations, whereas the granules are drifting on the cycloid–trochoid trajectories from the wall of reservoir, where the looped displacement is maximal, to the center of reservoir in which the shift of granules is reduced to minimum because of damping and dissipation effect. The received theoretical regulations have a fundamental nature and can be used at the account of technological parameters of designed vibration machines

Optimisation of the Explosive Compaction Process for Powder-In- Tube MgB 2 Superconductors Using Numerical Simulations

High quality, ex-situ powder-in-tube (PIT) Introduction Nowadays, superconductivity has a significant impact on many technological sectors, for example in the production of electric motors and magnetic sensors as well as in the energy transmission and storage technology. Superconducting wires and tapes are the key product for the adoption of this high technology, but the selection of a suitable superconducting material is not an easy task. MgB 2 is in general a low cost superconductor compared to other ceramic high T c materials, with a transition temperature near the liquid hydrogen boiling point. It has been estimated that approximately 15% of the generated electricity is dissipated during power transportation. In that respect, MgB 2 can be used for the construction of zero loss superconducting transmission lines, where liquid hydrogen may serve as refrigeration medium. The production of wires, coils and tapes requires forming at very high pressures due to the poor formability of the extremely hard ceramic superconductors. For this reason, the powder-in-tube (PIT) explosive compaction technique is considered to be a very promising powder metallurgy forming process for the fabrication of near full density MgB 2 superconductors as given in The present work is concerned with the optimization of the explosive compaction process, incorporating MgB 2 powders. The optimization is performed on an LS-DYNA numerical simulation model of the explosive compaction, where the external diameter of the tube and the dimensions (length and diameter) of the explosive surrounding of the PIT are used as input parameters. The peak pressure, peak maximum principal stress, porosity, uniformity of the tube radius, and mass of the explosive, are the corresponding simulation outputs, with the porosity being the most important parameter to optimize, since it is directly related to the interparticle bonding of the compact which affects the critical current density of the superconductor. Numerical Simulation of Explosively Densified PIT MgB Powders The shock consolidation process of the superconducting powders is numerically simulated using the LSDYNA finite element code. Since the PIT sample deformation during explosive loading is considered to be axisymmetric, a quarter 3D explicit finite element model is developed which is sufficient to accurately simulate the compaction procedure reducing this way the computational time. The finite element model mesh together with the corresponding experimental setup are demonstrated i

Improving the Design of Diamond Wheel for High-Speed Grinding

Grinding at high speeds is a complex process requiring specific tools for successful use. Rotational stresses during high-speed grinding can lead to failure if the wheel is not correctly designed. These results are extremely difficult to be obtained during a large number of field experiments due to the high cost of testing equipment. So, the article describes ways of improving the integrity of the body of the diamond grinding wheel for high-speed regimes using analytical approaches and finite element method

Developing manufacturing control software: A survey and critique

The complexity and diversity of manufacturing software and the need to adapt this software to the frequent changes in the production requirements necessitate the use of a systematic approach to developing this software. The software life-cycle model (Royce, 1970) that consists of specifying the requirements of a software system, designing, implementing, testing, and evolving this software can be followed when developing large portions of manufacturing software. However, the presence of hardware devices in these systems and the high costs of acquiring and operating hardware devices further complicate the manufacturing software development process and require that the functionality of this software be extended to incorporate simulation and prototyping.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45542/1/10696_2005_Article_BF01328739.pd