in Vol. 6 - January Issue - Year 2005
Hands-on Training at the MFN Shot Peening Workshop & Trade Show 2004 in Singapore
MFN Trainer Peter Beckmerhagen explaining the Ervin Tester
Hands-on Training on the Almen Gage
Training on the Sieve Analyser by Giovanni Gregorat
"The workshop is informative and the speakers are knowledgeable. Such a training can be recommended to anyone involved in shot peening!" Mr. Choy Hon Yin Head, Cleaning/NDT/Inspection Deputy Manager Production Singapore Aero Engine Services Private Limited (SAESL)
For the 4th time in as many years, the Asian MFN Shot Peening Workshop & Trade Show was held at the Hilton Hotel in Singapore from the 10th to the 12th of November 2004. The fact that there were a total of 63 participants at this event shows that the shot peening industry in this region can support a yearly event of this nature and size. In addition to the different FAA accepted courses, MFN also focused on expanding its hands-on training.
A total of 14 nationalities were represented at this event. Most of the companies came from the aviation industries, but also from the oil refining industries and the metal preparation industries. Over half of the participants who enrolled for one of the FAA accepted shot peening courses have taken the optional examination.
13 companies displayed their products and technology at the trade show. MFN decided to intensify its hands-on training during this particular workshop. So different equipment and devices such as Ervin tester, flap peening, sieve analysis, Almen gages and an Almen software were introduced to the students.
Hands-on Ervin Tester
The Ervin Tester is welcomed at the MFN workshop for the first time this year. Students are able to see how coverage develops and how to establish a saturation curve while physically touching and examining the strips during different stages. For those among our readers who may not be familiar with this miniature wheel-peening machine the following brief introduction is offered.
The Ervin Test Machine is a great tool for analyzing peening media for durability and the efficiency of transferred kinetic energy. It allows one to compare different media under controlled conditions.
The machine consists of a wheel with two blades, a target and re-circulating device, each of which rotate at different speeds around a common centerline. With a weight of only 80 kg and requiring a relatively small workspace (dimensions of 80 x 80 x 60 cm) it fits on almost every workbench.
The test media remains in the machine for a predetermined number of cycles and durability is simply determined by the number of passes against the target that are required to reduce the media to an unusable size. Since the completion of such a test is very time consuming (between 1 and 8 hours depending upon the durability of the media that is being tested) it focuses on the effectiveness of kinetic energy. However, the students are theoretically acquainted with the entire procedure.
The test machine is equipped with a peening attachment that enables one to mount an Almen test strip and expose it to the shot stream in the chamber. During the presentation Almen A strips are exposed to 0.5 and 0.8 mm peening media at different exposure times. A complete saturation curve is established so the students can see the different arc heights and varied percent of coverage reached at different exposure times. Two different media sizes are purposely chosen to demonstrate the significant influence of the shot size on the intensity and surface roughness.
The machine comes also with a frequency inverter allowing for a change in shot velocity, which in turn allows even more opportunities to duplicate the characteristics of production machines. Only 250 grams of media are needed for a test to accurately predict effects whereas in a production environment you would normally need many tons of media.
The Ervin Test Machine (named after the developer) is a simple portable piece of equipment that helps to demonstrate the fundamentals of shot peening being taught in the basic course. The training is designed to give students a practical knowledge of how media properties such as hardness, size, density and durability interact and determine the efficiency of energy transfer and consequently the economy of the Shot Peening process itself.
Hands-on Flap Peening
MFN is able to demonstrate the method for choosing a rotation speed (RPM) on a flap peening device that would yield a given intensity on the Almen gage. After peening a specimen it is possible to show the similarity to specimens that had been peened in the Ervin tester. The visual difference is the shot size. This is demonstrated with the Ervin test as well as with two different shot sizes.
The next step shows how easily an aluminum extrusion is saturation peened. One of the attendees is given the chance to feel the tool at work and to realise how the flap finds the correct height almost by itself. It also highlights how the flap sounds when correctly applied or not. Using some pre-stress one can use the flap for forming or straightening a part. That is done by taking two sections of an aircraft quality aluminum alloy 2024 T3511extrusion angle and clamping them together using a small metal block in the center to create an elastically curved section. It is proven by releasing them and they are fixed back to back without spacing. Then they are again clamped and flap peened. On release it is shown that placing them back to back the procedure has given the angle a curve, even working against the stiffening leg.
An addition is a rotor with a Scoth-brite pad that improves the surface finish of the formed part without loosing the shape. This is important as it shows that after applying the peening one can smooth the surface and still retain the fatigue benefits.
Hands-on Training for Sieve Analyzer
Since sieve analysis is a very important part of checking the quality of new or used media for shot peening, MFN likes to demonstrate the performance of a sieve analysis hands-on during its workshops. One can only begin a particle size distribution analysis after properly collecting, preparing and sizing a sample. The test sieves have to be selected with mesh openings that reveal particle distribution at critical sizes. These are usually stated in a product specification or determined by material processing requirements. The trainer shows how to stack the sieves on top of each other, how to weigh the sample material, set the proper length of time to agitate the material, etc.. Finally, after the test is completed it is illustrated how to calculate and record the cumulative percentages as required. Most industries set up their specifications by the percentage of material retained on a particular sieve. Some industries, however, use the percentage passing through a particular sieve for analysis.
MFN is aware of the fact that hands-on training alone does not make a good shot peening training. Much more the whole "package" counts. The right mixture between theoretical lessons, guest speaker presentations from the industries and practical demonstrations will guarantee that a student can benefit the utmost from such a workshop. The complete MFN team is continuously trying to improve the training with every event organized.