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An Almen round is a thin round disk used to quantify the intensity of a
The Almen round is a circular cutting from an original Almen strip normally in material
In the endeavor to standardize the parameters, the clamping down of the Almen rounds follows a strict geometry. The clamping head fixes the Almen round in correct manner, thus important for all related procedure. When working with the monitoring
Other than the Almen strip method with the two steps: 1. Processing with holder and 2. Measuring with gage, the Almen round technique combines those activities. The specimen holder is complemented with a measuring system, e.g. a distance sensor system of various kinds to complete the monitoring sensor. While bombarded by shot, the captured Almen round gets bent towards the direction of the attack. The linear transformation gets converted into an electric signal sent to a processing unit. With calibration discs, errors will be minimalized. For the offline measuring of an individual round, the online monitoring sensor or an appropriate device will also be used.
File:Online monitoring sensor with mounting fixture.jpg, Online monitoring sensor with mounting fixture
File:Almen graph.jpg, Automatically created diagram with final result shown
Many so called "critical parts""Critical parts"
Retrieved 23 January 2013 require a test run with dummy parts. Therefore the Almen round is captured in a special mount that can be screwed or glued onto the dummy or even on a real part. In such a case an online monitoring is not possible, the specimens must get removed and then measured separately with the monitoring sensor. In this case, only the arc height can be traced. So this application should be in combination with a parallel running online process.
shot peening
Shot peening is a cold working process used to produce a compressive residual stress layer and modify the mechanical properties of metals and composites. It entails striking a surface with shot (round metallic, glass, or ceramic particles) with ...
process. Developed in 1994 by Rudolf Bosshard in Switzerland, it is a modification of the Almen strip An Almen strip is a thin strip of SAE 1070 steel used to quantify the intensity of a shot peening process.
Developed and patented by John O. Almen, the strip was originally supported by 2 knife edges; later improvements see it being supported on ...
method, which is used worldwide as a surface treatment testing method in the field of shot peening. The basic principle is the same, but due to the simple shape and minimized size, the Almen round is more suitable for automated processing and installation on dummy rigs. Also instead of the Almen block according SAE
SAE or Sae may refer to:
Science and technology
:
* Selective area epitaxy, local growth of epitaxial layer through a patterned dielectric mask deposited on a semiconductor substrate
* Serious adverse event, in a clinical trial
* Simultaneous Auth ...
J442, here a matching device is used and if connected to electronic processing unit, the Almen value according AMS-S-13165 (predecessor MIL-S-13165 Rev.C) can be evaluated in one run.
Test specimen
The Almen round is a circular cutting from an original Almen strip normally in material SAE 1070
SAE or Sae may refer to:
Science and technology
:
* Selective area epitaxy, local growth of epitaxial layer through a patterned dielectric mask deposited on a semiconductor substrate
* Serious adverse event, in a clinical trial
* Simultaneous Auth ...
. It can be either of a "A", "C" or "N" type offered in various quality grades. The standard strip allows the splitting into four pieces rounds, which have a diameter of 18.7 mm, by either waterjet or laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...
technique. Therefore, the spaces are maintained in respect of material and thickness. The flatness test to follow is simple and imprecise pieces can be eliminated.
Specimen holder
In the endeavor to standardize the parameters, the clamping down of the Almen rounds follows a strict geometry. The clamping head fixes the Almen round in correct manner, thus important for all related procedure. When working with the monitoring sensor
A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon.
In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...
, the specimen is preloaded to increase overall accuracy.
Measuring technique
Other than the Almen strip method with the two steps: 1. Processing with holder and 2. Measuring with gage, the Almen round technique combines those activities. The specimen holder is complemented with a measuring system, e.g. a distance sensor system of various kinds to complete the monitoring sensor. While bombarded by shot, the captured Almen round gets bent towards the direction of the attack. The linear transformation gets converted into an electric signal sent to a processing unit. With calibration discs, errors will be minimalized. For the offline measuring of an individual round, the online monitoring sensor or an appropriate device will also be used.
Signal processing
Thus the equipment is designed for direct exposure to the shot stream, the deformation of the round can be monitored online and directly converted into the Almen standard arc high definition (SAE J443) either in mm or inches. Such a process time will be in the range of less than 5 to 40 seconds. If on screen, the graph shows the basis for the calculation algorithm, also the essential point in mm or inches that is the output information equivalent to the original Almen round definition.Advanced application
Many so called "critical parts"Retrieved 23 January 2013 require a test run with dummy parts. Therefore the Almen round is captured in a special mount that can be screwed or glued onto the dummy or even on a real part. In such a case an online monitoring is not possible, the specimens must get removed and then measured separately with the monitoring sensor. In this case, only the arc height can be traced. So this application should be in combination with a parallel running online process.
Field of application
The Almen round can be utilized inaircraft
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...
and automotive industry
The automotive industry comprises a wide range of company, companies and organizations involved in the design, Business development, development, manufacturing, marketing, and selling of motor vehicles. It is one of the world's largest industry ...
, research and subcontracting peening enterprises.
Application restriction
As the Almen strip principle has been established in 1942 and international standardization has reached a top-level. The strip work routine is a fixed procedure in practical peening technology. The Almen round principle is more accurate and offers a considerable working time reduction. But as there is no international approved standardization, this technique will be used for special applications only.References
Notes
Bibliography
* Bosshard, R., "Online Monitoring with Almen Rounds". In: Rautaray, S. K. and Sharma, M. C. ''Shot Peening and Blast Cleaning'' (1996). Department of Mechanical Engineering. MACT-Bhopal. pp. 37–44. * Sharma, M. C. and Deo, H. (2003). "Virtues & Limitations of Almen Round". In: L. Wagner. ''Shot Peening ICSP8''. WILEY-VCH pp. 83–88. . * Bosshard, R. "High-Tech Contour Evaluation of ALMEN Test Plates". ''Metal Finishing News'' March 2011, Vol. 12, pp. 60–61 *External links
* http://www.osk-kiefer.de/download/buchteile/files/en/v3/28-definition_of_shot_peening_control_and_parameters.pdf{{dead link, date=July 2017 , bot=InternetArchiveBot , fix-attempted=yes * https://web.archive.org/web/20130222062820/http://www.shotpeener.com/learning/almen_test.php Shot peening Measurement