VOL. 11 May ISSUE YEAR 2010
in Vol. 11 - May Issue - Year 2010
Standards Keeping Pace With New Peening Developments
Peening has a heritage that dates back into medieval times, when sword smiths used impact technology in the form of hammers and anvils to improve the performance of their products. Through the industrial revolution the manipulation of the composition and treatment of metals brought greater improvements, usually on a "trial and error" basis.
The twentieth century saw metals and machines being placed under greater loads and multiple stress cycles in the pursuit of productivity and efficiency improvements. Fatigue became recognized as a common failure mode so interest developed in the means to prevent such failure. When in 1943 John Almen devised his now ubiquitous test to calibrate the intensity of the process, he did not "invent" shot peening but provided an important technological development in controlling it and providing repeatability. The Almen strip saturation curve standardized the method for determining the process intensity so that comparable results can be achieved on different machines in different locations.
Technical development has continued to accelerate into the twenty-first century, providing exciting new technology and an increasing range of applications. But the need to standardize new technologies is crucial to ensure that they are correctly applied and give predictable results. The SAE organization has taken the lead role to supporting industry with this standardization of materials and processes and continues to provide new standards for peening.
SAE J2597 Computer Generated Shot Peening Saturation Curves, was published in January 2010. This SAE Recommended Practice provides the means to ensure that software used to determine peening intensity will provide consistent results. At present a number of suppliers can provide such software but there has been no standard to ensure that the output figures are accurate and consistent between the various software packages. This standard does not seek to define the algorithm necessary to produce the saturation curve but provides a number of datasets of arc heights and exposure times. For each dataset the software must produce an intensity figure within a specified tolerance band in order to conform to the requirement. This standard provides both suppliers of the software and end-users with the confidence that their results are accurate and consistent with an approved standard.
Ultrasonically activated peening is a technology which is becoming widely used in manufacturing and maintenance, repair and overhaul (MRO). It can provide benefits in the controllability of the process and the resulting surface finish. There can also be a reduction in noise and the risk of contamination of the working environment and the part. Until now the use of the process has been as a result of agreement between users and the relevant engineering authority for the parts to be processed. So authorization of the process has been added to proprietary specifications or raised for specific applications. The Aerospace Materials Engineering Committee (AMEC) of the SAE has been working on a standard for this process and AMS2580, Shot Peening, Ultrasonically Activated, is the result. To support this process specification another standard, AMS2585, Peening Media, Ultrasonically Activated, is being produced. The final publication of these standards is eagerly anticipated.
AMS 2430, Shot peening, Automatic, is in the process of complete revision. Due to the importance of this widely used specification, great attention is being paid to ensuring that the new revision will provide the best current practice in shot peening.
A comprehensive new standard for Rotary Flap Peening of Metal Parts has been drafted and is subject to intensive review prior to publication. This standard will address the inadequate areas of the old MIL-R-81841 specification for flap peening; in particular it will bring the determination and verification of intensity more in-line with the current understanding of the process. It will also make use of the process easier with clearer instruction on setting tool speeds and requirements for hole peening. There will also be another new standard, Rotary Flap Peening Wheels, to better specify requirements for the flaps to be used.
Further information on the SAE and SAE standards can be found at www.sae.org.
For questions contact email@example.com
by Paul Huyton,
MFN Course Director World Wide
more information at www.mfn.li/trainers