WEAR AND ITS COMPETING FAILURE MODE FACTORS OF COMPONENTS

The analysis of all the desired contributing factors is necessary to predict the result of a single wear and its competing failure mechanism, but several sources of deterioration may combine to complicate what might otherwise be a straightforward solution. The main multiple factors that influence wear and its competing failure modes are as follows:

-          Metallurgical variable (Hardness, toughness, constitution and microstructure, chemical composition)

-          Service Variables (Contacting materials, pressure, speed, temperature, surface finish)

-          Other factors (Lubrication, corrosion, vibration)

It is actually impossible to generalize about a material’s suitability, such as to say a certain composition is the most wear and its competing failure resistant, without considering factors such as service conditions. For example, two materials, one of which is clearly superior to the other for a specific application, may undergo a complete reversal in wear resistance from only slight changes in service conditions. Although strength, hardness and ductility or toughness are important, wear resistance cannot always be associated with any one property. Wear resistance generally does not increase directly with tensile strength or hardness; however, if other factors are relatively constant, hardness values provide an approximate guide to relative wear behavior among different metal. This is especially true for metal – to – metal sliding and abrasive applications.

In the cases, where other factors may vary, it will be necessary to consider other factors such as service, environmental and manufacturing conditions that combines to produce maximum achievable wear and competing failure resistance (like corrosion, temperature, fatigue, vibration and temperature resistance).  As long as these conditions continue to vary, wear resistance and its competing failure resistance is also bound to vary. It will therefore be necessary to optimize all the operating conditions of the technological system in order to make the wear and its competing failure resistant values constant for a specific period of time. The technological system condition of this case includes the followings:

-          Metallurgical Conditions

-          Surface Coating Deposition Conditions

-          Surface Finish Conditions

-          Service Conditions

-          Monitoring Conditions

-          Maintenance Conditions

Multiple regression models is used to relate the technological operating conditions with component surface quality conditions, which helps to select the significant surface quality parameters, manufacturing processes and to determine maximum achievable reliability and life-time. The highest surface quality factor value by any of the technological process is selected for the optimization of the system.

The selected optimization process will ultimately serve as the optimum baseline for all the operating conditions of the technological system. The optimization of a component surface finish condition provides the optimum surface quality, optimum process condition, selects the desired number of parameters and factors as well as determines their optimum values. The multiple surface quality parameters of hard-alloy coating are selected as surface hardness, surface roughness, surface wavelength, surface stress and kinematic coefficient for maximum achievable reliability. The optimum multiple quality values can be integrated together to form a single quality and reliability factor, which can be used to construct wear failure/wear resistant mechanism and other  competing failure mechanism or its failure resistance mechanism. Technological inheritance technique is used to plot the mechanism diagram, predict the time of failure, diagnose failures, and determine maximum achievable reliability, reliability growth/degradation, life-time and life cycle cost.

http://www.integrated-consultancy.com/