BOOKS and CONFERENCE PROCEEDINGS
on SHOT PEENING and BLAST CLEANING
Shot Peening - Theory and Applications $ 70.00 USD
Edited by: John Eckersley and Jack Champaigne
- 1. Influence of Shot Peening on Material Properties and the Controlled Shot Peening of Turbine Blades
- by: C. Verpoort and C. Gerdes
- Abstract: The change of surface properties and the metallurgical processes during shot peening treatment are studied in some detail. In addition, the influence of shot peening on the fatigue strength is explained using an Austenitic steel and a ferritic 12% chromium steel as examples. The aim of the work was to investigate shot peening parameters which influence the fatigue strength of components. The presented results should lead to a better understanding of the metallurgical processes during shot peening and should thus allow the choice of the optimum peening parameters. It will also be demonstrated, how shot peening can be integrated into the production process of components and which measures, concerning the peening parameters and the quality control, have to be taken into account. New methods of quality assessment will be introduced.
- 2. X-Ray Diffraction Stress Measurement on Various Shot Peened Components
- by: E.B.S. Pardue and L.A Lowery
- Abstract: The x-ray diffraction technique is especially applicable to measuring stresses in shot peened components. This technique gives absolute stress values over thin sections which allows stress versus depth to be measured. The aerospace industry has used this technique in numerous applications. This paper presents cases in which: (1) nontraditional media have been used for shot peening, (2) subsurface stresses after peening were compared to different coverageís and (3) stress and peak width were used to assess the most effective peening depth.
- 3. X-Ray Diffraction Characterization of Residual Stresses Produced by Shot Peening
- by: Paul S. Prevey
- Abstract: A brief overview of the theory and practice of x-ray diffraction residual stress measurement as applied to shot peened materials is presented. The unique ability of x- ray diffraction methods to determine both the macroscopic residual stress and the depth and magnitude of the cold worked layer produced by shot peening is described. The need to obtain a complete description of the subsurface residual stress distribution, in order to accurately characterize the residual stress distribution produced by shot peening, is emphasized. Non-destructive surface residual stress measurements are shown to generally be inadequate to reliably characterize the residual stresses produced by shot peening. Practical applications of x-ray diffraction methods for quality control testing are considered. Examples are presented for steel and nickel base alloys.
- 4. Strain Tensor Determination Using Neutron Diffraction
- by: H.G. Priesmeyer and J. Schroder
- Abstract: The tensor which describes the three-dimensional state of deformation caused by residual stress can be determined in a nondestructive way by neutron diffraction. The mathematical tools to derive principal strains and their directions from experimental data are described and used to evaluate a pilot experiment.
- 5. Stain Determination in a Friction-welded Sample Using Non-destructive Neutron Diffraction
- by:H.G. Priesmeyer and J. Schroder
- Abstract: Neutrons can penetrate thick layers of many engineering materials and therefore provide a useful technique to investigate internal strains reproduced by lattice deformations in a nondestructive way. The method uses high-resolution neutron diffractometry to determine lattice parameter variations, etc.
- 6. Measurement of Residual Stress Distribution by the Incremental Hole- Drilling Method
- by: A. Niku-Lari, J. Lu and J.F. Flavenot
- Abstract: The hole-drilling method is widely used for the measurement of residual stresses in mechanical components. Recent developments have shown that strains measured on the surface during an incremental drilling can be related to residual-stress distribution. Researchers, internationally, have proposed different methods of calibration which lead to results of varying degree of accuracy.
- 7. Shot Peening Process Controls Ensure Repeatable Results
- by: John Eckersley
- Abstract: Shot peening is a cold working process applied to the surface of metal parts to increase their resistance to fatigue, fretting fatigue, stress corrosion cracking, corrosion fatigue and various other tensile stress related metal failures. Shot peening has also been used effectively to form aerodynamic curvatures into large sculptured panels such as aircraft wing skins, some over 90 feet long. In all cases, the effectiveness of the process is due to the introduction of residual compressive stresses into the surface of the parts. When a metal surface in indented, a residual compressive stress is induced as a subsurface material attempts to push out the indentation and restore the surface to its former condition. Shot peening, by bombarding the surface with millions of tiny spheres of steel, glass or ceramic, totally covers the surface with indentations, creating an even layer of compressive stress that is at its maximum just below the surface and is at least equal to 50% of the ultimate tensile strength of the metal.
- 8. Shot Flow Rate Monitors and Controls: (If you canít monitor it, you canít control it)
- by: Jack Champaigne
- Abstract: The shot peening process relies on multiple impacts of spherical media to a surface to achieve residual compressive surface stress. The flow rate of the media times the exposure time determines the number of impacts in a given surface area. To achieve consistent peening performance it is therefore necessary to continuously monitor the media delivery system. This can be achieved with inductive sensors for ferrous media or capacitive sensors for non-ferrous media. Beyond providing a consistent process, these devices will also promote process optimization whereby desired intensity and coverage can be maintained and productivity can be enhanced. The ability to accurately determine media flow rates then leads to the ability to accurately control the flow rate. Screw conveyers, miniature belt conveyors, pneumatically controlled grit valves, and magnetic valves can be employed.
- 9. The Shot Peener Library
- by: Jack Champaigne
- Abstract: The Shot Peener Library was established in 1986. At the same time The Shot Peener International Newsletter was first published. These services were intended to provide the shot peening industry a means of accruing and promoting knowledge relating to the impact surface treatments of shot peening, blast cleaning and paint stripping. By the end of 1990 the library had acquired over 1,000 articles on peening, fatigue, stress corrosion, etc. The newsletter circulation had risen to over 3,000 subscribers in over 50 countries, demonstrating the need to knowledge distribution.
- 10. The Role of Robotics in Computerized Shot Peening
- by: Bruce DeClark
- Abstract: The use of computer-controlled robotic shot peening has increased substantially in recent years. This is particularly true in the area of improving the performance of highly stresses parts. Jet engine manufacturers are relying increasingly on robotic peening for life enhancement of critical components. The current trend in the design of high-performance fuel-efficient gas turbine engines is to incorporate improved, lighter materials for increasingly stringent operating conditions. To meet the performance requirements now demanded of these materials, almost all gas turbine engines rely heavily on proper shot peening technology to greatly enhance the fatigue life of the engine components. In many cases, the complex shape and precise peening requirements of these components virtually eliminate conventional peening methods. Automotive companies are continuing to appreciate the benefits computer controlled shot peening offers for their highly stresses drive train components.
- 11. Shot Blasting Systems
- by: Thomas A. Briere
- In recent years, shot blast cleaning systems have replace other mechanical or chemical metal surface preparation processes. This is especially true where specification call for cleaning, descaling, paint removal, deburring, coating surface preparation or achieving certain cosmetic goals. Some of the processes replaced by shot blasting include wire brushing or grinding the surface manually, manual or automatic sanding, chemical dip tanks, and chemical etching systems. shot blast systems have been successful in these applications because of the speed at which the tasks are completed, with minimal manpower requirements. In general, shot blast systems are much less expensive to operate than alternate methods.
- 12. The Case for Ceramic Shot
- by: H. Barzoukas and G. Fernandez
- Abstract: Ceramic shot was introduced in 1981. Since then, its use has been developing, particularly on materials such as stainless steel and non ferrous alloys, for example aluminum and titanium alloys in the aerospace industry. The peening properties of the shot stem from the chemical and physical characteristics of the ceramic material. Consolidated experimental and industrial data show that ceramic shot presents a very low breakage. Because of its density, the Almen intensities obtained with ceramic are intermediate to those obtained with steel shot or glass beads. Surface finishing benefits from the low breakage and non polluting characteristics. Two studies on fatigue strength are referred to: one deals with titanium alloy parts and the other with hard steel.
- 13. A Concept for Preventing Repeated Weld Repairs of Bridge Structures
- by: W.H. Welsch
- Abstract: Recent studies and publication have discussed methods of improving fatigue life in welded structures. The writer investigates the mechanism for fatigue failures in weldments as well as the data supporting various post weld failures. The paper will deal in depth with the control of these processes and how to achieve consistent improvements in post weld treatments.
- 14. High Technology Shot Peening for the Automotive Industry
- by: Robert P. Graibay and Syndey L. Terry
- Abstract: The purpose of this paper is to present a technical overview of the shot peening process, comparing the conventional ìcontrolledî process to the state-of -the-art precision shot peening. The fatigue strength/host benefits as well as the challenges and obstacles to reproducibility are examined in light of high production automotive volumes. Examples of applications where precision shot peening can most effectively be utilized to increase the strength/weight design characteristics of automotive components are provided.
- 15. Application of Rotary Peening in Aircraft Maintenance
- by: Douglas Earl
- Abstract: Shot peening with the 3M Roto Peen method provides the ability to obtain the benefits of conventional shot peening techniques, but with a more-compact and more- easily used system than those usually associated with this process. The portability and simplicity of this system have led to its wide use in both aircraft maintenance and manufacturing areas. The 3M Roto Peen system consists of tungsten-carbide shot adhered to a rotating flap. The motion of the flap propels the shot into the workpiece producing beneficial surface compressive stresses. The 3M Roto Peen system can be used by adapting powered tools that are generally available in most manufacturing and maintenance settings.
- 16. Shot Peening Plays a Vital Roll in Rejuvenation of Aging Aircraft
- by: John Eckersley
- Abstract: Aircraft Components design engineers are very well aware of the benefits of surface residual compressive stresses on new parts as a means of retarding or even preventing catastrophic failures from fatigue, fretting fatigue, corrosion fatigue and stress corrosion cracking. Each of these failure modes depends on the presence of surface tensile stresses either residual or applied but, in service, usually both. It has been common practice, on parts for jet engines, propellers and landing gear, to reintroduce surface compressive stresses at overhaul intervals. Thousands of such parts are shot peened every day for rejuvenation purposes. airframe parts present a different problem since they are not normally dismantled at overhaul and it is precisely these parts that come to mind when we consider ìaging aircraftî. Airframe components, whether they are steel, aluminum or titanium, can be rejuvenated by the introduction or restoration of surface residual compressive stresses, in most cases without requiring dismantling from the aircraft. This paper also reviews practical methods of shot peening aircraft structures ìin situî, using inert media, under fully controlled conditions of Almen intensity, coverage, angle of impingement, media recovery, etc. Examples of actual applications on commercial and military aircraft are covered in detail, including offsetting the debiting effects of exfoliation corrosion. Peen forming of wing skins on aircraft is also addresses.
- 17. An Evaluation of Nickel-aluminum Coatings Fabricated with the Plasma- Spray Process
- by: D. Varacalle, J. Knibloe, V. Smith-Wackerle, J. Walter and G. Iron
- Abstract: As part of an investigation of the dynamics that occur in the plasma-spray process, an experimental study of the plasma spraying of nickel-aluminum powder was conducted. The coating experiments used typical process parameters that were varied in a Taguchi fractional factorial design parametric study. Operating parameters were varied around the typical spray parameters in a systematic design of experiments to display the range of plasma-processing conditions and their effect on the resultant coating. Parameters varied include the working gas mixture, power, powder injection location, spray distance, traverse rate, and powder feed rate. Typical operating conditions for the torch of this study were 35 V, 800 A, 100 standard ft3/h (scfh) argon primary gas flow, 47 scfh helium secondary gas flow, and 7 lb/h powder feedrate. These parameter settings were used with a 3-in. spray distance and a gun traverse rate of 20 in/sec. The statistical scheme varied around these monomial parameter settings. The coatings were fabricated with ten passes, which yielded relatively even were characterized by hardness tests, optical metallography, and x-ray diffraction. Coating qualities are discussed with respect to thickness, hardness, porosity, and phase content.
- 18. Shot Peening to Prevent Stress-Corrosion Cracking of Nuclear Stream Generator Tubes by:
- Stanford P. Hellman
- Abstract: The steam generator tubing in nuclear power plants forms part of the primary pressure boundary between the highly radioactive primary water and the non-radioactive water in the steam cycle. In approximately 15 nuclear plants in the US and others overseas, all Alloy-600 steam generator tubing is susceptible to primary water stress corrosion cracking (PWSCC). this cracking occurs at the transition zone where the tubing is roll expanded into the tubesheet and is caused by a combination of properties which include the operating environment, tube material properties and a tensile stress on the inner diameter of the tubing. Laboratory testing and field experience have shown that shot peening the inner surface of the tubing to impart a layer of uniform compressive stress is effective in preventing the initiation of new cracks.
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Revised: 6/02
