Di-Chen Xiao

Computer aided modelling of the human spine

Abstract The human spine is the main structure to support human body weight and external loads, to allow the torso to reach to a variety of positions and to protect the spinal nervous system. Lumbar back pain and disorders may be related to spinal curvature and disc pressure, and it is an ultimate objective of the work reported here to include consideration of these issues in computer aided ergonomics design systems for evaluating a wide range of situations including manual handling and car seat design. Several methods from structural analysis have previously been used to model the human spine, principally lever and beam structures, but these have frequently shown discrepancies when compared with experimental data. As an alternative, an arch representation for the spine is considered here and allows the establishment of a criterion for the failure of the spine that may be useful in determining absolute maximum loading conditions. However, the main interest is in submaximal loading conditions where damage or discomfort are the concerns rather than fracture. It is proposed that the location of the thrust line in relation to the centre-line of the spine is a useful predictor, and optimization techniques have been developed to find the ‘best-fitting’ thrust line for the statically indeterminate structure. Further work is concerned with adding muscle and ligament forces to the loading system of the model, extension of the two-dimensional model into three dimensions, validation against experimental data and integration with the SAMMIE computer aided ergonomics design system.

Laser cladding of lead bronze

The monotectic alloy of Pb and Cu poses particular problems in laser cladding due to the separation of the alloy constituents with widely different melting points. This system was clad by laser and the results for a variety of operating conditions are illustrated.The effects of process parameters on Pb segregation, Fe inclusions from the substrate and porosity are examined and described with reference to the solidification mechanism.By varying the composition of the powder feed into the laser generated melt pool patterned claddings were produced. The metallurgy of such clads is discussed.The monotectic alloy of Pb and Cu poses particular problems in laser cladding due to the separation of the alloy constituents with widely different melting points. This system was clad by laser and the results for a variety of operating conditions are illustrated.The effects of process parameters on Pb segregation, Fe inclusions from the substrate and porosity are examined and described with reference to the solidification mechanism.By varying the composition of the powder feed into the laser generated melt pool patterned claddings were produced. The metallurgy of such clads is discussed.

Spine modelling and ‘safe to use’ equipment design

Computer human modelling has for sometime been developed and used but even the most sophisticated commercially available human modelling packages do not have an effective spine model. Although some packages have a geometric representation of the spine, they have no analytic or design application functionality. On the other hand back pain and back injuries are well-known to be a major problem and lead to substantial costs to manufacturing industry through enforced absenteeism. The main objective is to provide an answer to the need for a design tool which can consider the range of postures and predict the loads that will be imposed on the spine.

Laser Cladding of Low Melting Point Alloys

Laser cladding has been used for some years as a commercial hardfacing method [1]. The two main laser cladding (and alloying) techniques are: i) Preplaced powder [2]. Here powder is preplaced on the substrate with a binding agent to “stick” the powder into place until it is melted by the laser. The whole process is normally shrouded in an inert gas such as argon. Unfortunately there is only a small operating region of process parameters where low dilution and a good fusion bond are possible. ii) Blown powder [3]. Blown powder has a much larger operating region than preplaeed powder. Powder is blown directly into a laser generated meltpool as it scans across the surface of the substrate. The powder melts and a clad track is built up. Complete coverage is achieved by overlapping the tracks. .

A Method for the Design of Forming Cutters for Machining Modified Involute Helical Gears

A method using contact curve principle for the design of forming cutters for machining modified involute helical gears is introduced in this paper. Equations for calculation of the cutter profile from the given modified involute tooth profile of the gear are derived. The amount of modification on standard involute can be provided in a mathematical function form or as a set of discrete values.