PROJECT PLAN

Improving Reliability by Reducing the Sensitivity to Variations in the Tolerance of

Critical Geometrical Parameters

Student Number

Name

MSc Programme

Supervisor

Date

Department of Mechanical Engineering and Mathematical Sciences

2012-2013

Project Plan

1.0 INTRODUCTION

Modern engineering is characterized by an increased requirement for geometrical parameters in manufacturing quality surfaces of parts, accuracy of the size, shape deviations i.e. their waviness and roughness. These parameters define the contact deformation and stiffness of joints, characterized by friction and wear surfaces, sealing compounds, bonding strength and coating etc (O'Conner & Kleyner, 2012, pp. 9). It is necessary to ensure not only the specified surface quality requirements, but also the stability of which is determined by the parameters of the stochastic characteristics of the geometry of work-piece surface allowed under the law on distribution.

Formation of stochastic characteristics dimensional accuracy of the machined surface is well known. At the same time, the use of a similar approach for the study received roughness and waviness of the surface during mechanical treatment has not received proper distribution (Todinov, 2005, pp. 11). This is due to the fact that the measurement of roughness parameters is required to provide much more accurate determination of size which increases the complexity of this approach. Often, it is used to calculate the surface roughness of the expectation model, which does not take into account the stochastic nature of the formation of microgeometry. Capabilities of modern computers allow us to investigate the stochastic characteristics of the surface microgeometry items until the receipt of distribution functions of parameters.

2.0 OVERALL AIMS OF THE PROJECT

The following are the major aims of the project:

A compilation of generic principles and techniques for the achievement of robust designs; characterised by a small sensitivity to variations of critical geometrical parameters.

Generating insight into the influence of the variation of geometrical parameters on reliability of components and assemblies.

New designs characterised by a small sensitivity to variations of critical geometrical parameters.

3.0 LITERATURE REVIEW

Researchers explain the status of the problem of forecasting the geometric parameters of surface quality of parts. Analysis of the existing algorithms and models to predict the geometric parameters of the surface showed that the research in this area is insufficient for reliable design technology. According to O'Conner & Kleyner (2012), the geometric parameters such as outside diameter, the diameter of bottom of the base circles and step shrink differently, however, take the same contraction coefficient for all parameters having no specific expressions. During the cooling process of the plastic parts contractions occur moulding and post-moulding, due to crystallization, the relaxation of the material volume, and therefore the thermal shrinkage of the thermoplastic material and the mould. For example, plastics such as acetal and nylon have from four to five times a thermal expansion coefficient higher than that of steel.

Todinov (2005) addresses the issue of contractions and how different products plastic mold removed after the shrinking process continues although at a lower rate. Moreover, it leaves open the issue of the coefficients of involvement in the dimensions of the plastic parts and merely gives the percentages of contraction ...