VOL. 6 November ISSUE YEAR 2005
MFN Trainer Column
in Vol. 6 - November Issue - Year 2005
Shot Peening and the Design Engineering Process
MFN Trainer Markus Halder
This column is a regular feature and is written by one of our MFN trainers. Readers are invited to send comments or questions to firstname.lastname@example.org. For more information about the trainers, see www.mfn.li link workshops.
by Markus Halder, Official MFN Trainer
First of all I would like to thank MFN for the integration into the trainer team and the interest in my work in the field of shot peening and optimisation of component parts. I am looking forward to working together with a motivated and qualified team.
The Metal Finishing News is more than a professional journal for insiders – in addition the industry gets the possibility to share information about new technologies and applications on a modern market. It gives the opportunity to get in contact with specialists and partners from research and economy and to reach the responsible person for complex tasks and individual problems.
The demand for high loaded component parts increases and as a result there are new challenges for the design engineers. The selection of the material and combination of manufacturing technologies should guarantee a durability of the components for as long as possible and a decrease in the production costs. To assure a certain fatigue limit the designers integrate safety factors into the construction of component parts. Hereby they try to balance oscillations of quality - even caused by production tolerances. These safety factors may cause oversized units and therefore an unwanted larger self-weight. A well directed shot peening operation not only improves the component properties of the units, it also allows optimisation of their dimensions.
For over a hundred years the positive influences of shot peening on the surface of dynamic and static loaded components have been well known. Through shooting of ball-shaped shot the surface gets deformed and compressed. The result is a residual compressive stress layer that defuses the risk of breakage caused by changing cross-sections like cut-ins or cranks on shafts, axles or similar components. and unload the edge layer while operating. Furthermore the particular surface topography with its random roughness profile creates a better lubrication and quietness especially for gears. The plastic deformation of the surface causes an increase of the hardness that leads to a higher resistance against galling.
The edge layers of the work pieces which are responsible for fatigue are influenced by the shot peening-operation to the best advantage. The fatigue resistance of units which are stressed due to vibration and shock is improved. E.g. the durability can be advanced by a factor of 100 by shot peening. It is also successfully applied in case of stress corrosion cracking, fretting corrosion, erosion-corrosion and abrasion or the combination of these.
However, which possibilities are available for the designer to integrate shot peening into the sequence of production? Often it happens that one gets confronted with specifications that are not backed up by research. Sometimes design engineers are helpless and create a shot peening process “blind” without knowing the exact effects - one is sure that there has to be an improvement in behaviour of fatigue limit – but an optimisation with a systematic procedure is not carried out. In complex assemblies there is little space so the designer is restricted with the dimensioning. The component requirements and the claim of their reliability increase steadily; partly through increasing loads or higher frequencies and cycles.
To create an adapted unit that conforms to the higher requirements it is necessary to examine the material, all operations and specifications of the integrated manufacturing technologies - shot peening included - and their effects on durability and fatigue strength.
The MFN Magazine represents an open interface created by specialists and gives everyone the opportunity to get professional care.
Author: Markus Halder