SAE ARP 7488-2018 Peening Design and Process Control Guidelines.pdf

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1、 _ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising ther

2、efrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2018 SAE International All rights reserved. No part of this

3、publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-49

4、70 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/standards.sae.org/ARP7488 AEROSPACE RECOMMENDED PRACTICE ARP7488 Issued 2018-01 Peening Design and Process Contr

5、ol Guidelines RATIONALE ARP7488 was previously a part of AMS2430. It was determined that it should be an Aerospace Recommended Practice. 1. SCOPE This Aerospace Recommended Practice (ARP) describes design and processing considerations for the peening process when AMS2430 or AMS2432 are specified. 2.

6、 REFERENCES 2.1 Applicable Documents The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of co

7、nflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 2.1.1 SAE Publications Available from SAE International, 400

8、Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or +1 724-776-4970 (outside USA), www.sae.org. AMS2430 Automatic Shot Peening AMS2431 Peening Media General Requirements SAE J2441 Shot Peening 3. GUIDELINES For design guidance to the purchaser or the cognizant

9、 engineering organization, the following information is provided. The peening process should be considered in the overall process planning for each individual part. The peening operation should be in the proper sequential order so subsequent processes do not negate the peening affects. Secondly, the

10、 peening process itself should be designed to assure proper peening of all required areas. Consulting with a peening processor may provide insight of manufacturing design and limitation considerations. The part cleaning method, type of equipment and controls, intensity verification areas and methods

11、, coverage inspection method, post-peening cleaning method, and preservation and shipping method should be provided. The purchaser or the cognizant engineering organization should communicate if the peening process and control procedures and/or sample peened parts for each part number need to be app

12、roved prior to production peening by the processor. SAE INTERNATIONAL ARP7488 Page 2 of 7 3.1 Typical Depth of Compressive Stress Table 1 shows typical depths of compressive stress for peened components. Many factors will affect the actual compressive stress depth such as material type, part hardnes

13、s, and peening media size, and type. Measurement of compressive depth can be performed by destructive analysis of actual parts or coupons of the same material heat treated to the hardness as the actual part. Table 1 - Approximate depth of compressive stress Material Intensity, inch (mm) 0.008N (0.20

14、N) 0.008A (0.20A) 0.008C (0.20C) Compressive Stress Depth, inch (mm) Aluminum 0.003 (0.08) 0.010 (0.25) 0.027 (0.69) Titanium 0.002 (0.05) 0.007 (0.18) 0.018 (0.46) Steel less than 200 ksi (1379 MPa) tensile strength 0.003 (0.08) 0.008 (0.20) 0.025 (0.64) Steel 200 ksi (1379 MPa) tensile strength an

15、d greater 0.002 (0.05) 0.005 (0.13) 0.015 (0.38) Nickel alloys 0.002 (0.05) 0.006 (0.15) 0.020 (0.51) 3.2 Intensity considerations Tables 2 and 3 shows typical intensity values of various materials and thicknesses. Table 2 - Media size and intensity guidelines for various materials Material Thicknes

16、s 0.090 to 0.375 inch (2.29 to 9.52 mm) Material Thickness Over 0.375 inch (9.52 mm) Material Media Size Intensity, inch (mm) -0.002A (-0.05A) +0.005A (+0.13A) Media Size Intensity, inch (mm) -0.002A (-0.05A) +0.005A (+0.13A) Titanium Alloys 110 minimum 0.008A (0.20A) 110 minimum 0.008A (0.20A) Stee

17、l, tensile strength less than 200 ksi (less than 1379 MPa) 170 minimum 0.010A (0.25A) 230 minimum 0.012A (0.30A) Steel, tensile strength 200 ksi and above (1379 MPa and above) 170 minimum 0.010A (0.25A) 230 minimum 0.014A (0.36A) Aluminum 170 minimum 0.008A (0.20A) 230 minimum 0.012A (0.30A) Notes:

18、1.Media sizes listed in Table 8 are for ASR (cast steel shot, regular) and ASH (cast steel shot, hard). 2.For material thickness under 0.090 inch (2.29 mm), see 3.4.4 SAE INTERNATIONAL ARP7488 Page 3 of 7 Table 3 - Media size and intensity for holes under 0.750 inch (19.05 mm) Material Media Size In

19、tensity inch (mm) Aluminum Alloys: Holes Under 0.735 inch (18.67 mm) diameter 70 minimum 0.010N minimum (0.25N minimum) All Alloys except Aluminum: Holes Under 0.750 inch (19.05 mm) diameter 70 minimum 0.010N minimum (0.25N minimum) Notes: 1. Media sizes listed in Table 9 are for ASR (cast steel sho

20、t, regular) and ASH (cast steel shot, hard). 2. For material thickness under 0.090 inch (2.29 mm), see 3.4.4 3.3 Peening media size for peening materials For applications not covered in Tables 2 and 3, materials should not be peened with media smaller for the intensities shown in Table 4 except when

21、 shielded areas are involved. Table 4 - Minimum recommended media sizes Intensity inch (mm) Peening Media1 0.012A (0.30A) ASR or ASH-280 AWCR, AWS, or AWCH-28 AGB (0.039 - 0.028 inch diameter) AZB (0.033 inch nominal diameter) 0.016A (0.40A) ASR or ASH-390 AWCR, AWS, or AWCH-41 AGB (0.056 - 0.039 in

22、ch diameter) AZB (0.046 inch nominal diameter) 0.020A (0.50A) ASR or ASH-550 AWCR, AWS, or AWCH-54 AGB (0.079 - 0.056 inch diameter) Notes: 1. See AMS2431 for definitions. 3.4 Peening Areas The engineering drawing typically designates areas to be peened. If the drawing is not specific to all areas o

23、f the part, each individual area should be addressed and instructions provided by the purchaser to the processor. 3.4.1 Areas not requiring peening and not required to be masked should be considered optional. 3.4.2 Areas specified not to be peened may either be masked from the peening stream or they

24、 may be peened if subsequent machining operations remove the effects of peening on such areas. When it is impractical to mask or protect areas designated to be free from peening, sufficient stock should be provided in these areas for subsequent removal of affected material for compliance with dimens

25、ional requirements of the applicable drawing. The control of stock removal should be specified in the post-peening process planning. 3.4.3 Shielded or partially shielded areas, walls of deep recesses, or other areas less accessible to the maximum effect of the blast stream will receive less peening

26、as to intensity and coverage than more exposed or more favorably oriented areas, and may therefore require additional peening or repositioning of the part to achieve correct peening in these areas. Use of special nozzle equipment or employment of deflector peening operations may be useful in diminis

27、hing the amount of additional peening. 3.4.4 The peening of very thin, under 0.090 inch (2.29 mm), or small sections to high intensities should be avoided because of the distortion and high residual tensile stresses in the core material that may result from such peening. The peening intensity used f

28、or thin sections should be such that the cross-sectional area under compressive stress should not exceed 10 percent of the total cross-sectional part width. SAE INTERNATIONAL ARP7488 Page 4 of 7 3.5 Pre-peening Part Considerations 3.5.1 Parts should be provided to the peening processor by the purcha

29、ser in a condition prepared and ready for the peening process. The planned sequence of operations should result in parts provided to the processor that are free of grease, dirt, oil, corrosion, burrs, sharp edges, mechanical damage and corrosion-preventive coatings such as anodic coatings, plating,

30、or paint. All burrs should be removed, and edges and corners to be peened should be rounded prior to peening to prevent material rollover. All heat treatment and non-destructive testing should be completed prior to peening. The part should be provided to the processor with all part dimensions and fi

31、nish requirements met. 3.5.2 The part drawing or process planning should provide instructions for masking all required areas to protect them from peening or possible damage (e.g., to prevent warpage on thin sections). Consideration must be made to extend masking beyond features such as threads (espe

32、cially threads without thread relief) to protect them from peening damage. 3.5.3 Peening Equipment The peening designer should take into consideration the type of machine being used to peen the part and the geometry of the part. The type of machine will dictate how the peening of the part geometry w

33、ill be performed with a number of part setups. Fixed nozzle or wheel machines provide line-of-sight media impingement with limitations to access to all surfaces of the part without multiple part setups and holding fixtures. Robotic machines provide line of sight media impingement for a wide variety

34、of geometries reducing multiple setups. Computer controlled and monitored machines offer the industrys best practice for process control. Computer-controlled peening equipment should be considered for use in maned flight vehicle components, components where peening is used as part of the design life

35、 of the component, and components that are considered critical to system success. 3.6 Process Development Each part will use a scrap part or representative fixture to support test strip holders at designated intensity verification locations. Effective peening requires that the specified intensity an

36、d coverage be achieved on critical areas as designated by the cognizant engineering authority, where high tensile stresses or stress ranges are most likely to cause fatigue or stress corrosion failures in service. The intensity verification locations are determined based on the criticality of the pa

37、rt, the propensity to cause fatigue or stress corrosion failure, and the type of equipment being used. Considerations affecting the quantity of verification locations include changes in media angle of impingement, stand-off distance, machine limitations, part setups, and part geometry. A minimum of

38、one intensity verification location is needed for each variation of machine settings, e.g., standoff distance, media flow, air pressure, impingement angle, in accordance with part setup. Efficient location of intensity verification test strips and holders may minimize process time and cost. 3.7 Peen

39、ing Media Size Selection In selecting peening media sizes, consideration should be given to the following factors: Shape of parts Size of fillets (small peening media needed to impact small fillets) Intensity desired (the size of peening media limits the intensity that can be obtained in a given pee

40、ning machine). Therefore, it may be necessary to use a larger peening media to obtain a higher intensity or to reduce intensity requirements when peening media must be small for consideration of fillet radii. Finish (at equal intensities larger peening media will produce a finer surface finish) Smal

41、l diameter media at high intensity on aluminum or magnesium alloy parts should be avoided due to the possibility of damaging or imbedding peening media particles on the part surface. SAE INTERNATIONAL ARP7488 Page 5 of 7 3.8 Peening Hard Materials Part surfaces with a hardness of 55 HRC or higher pe

42、ened with regular hardness peening media will look similar to a burnished or polished surface and require the use of an alternative visual inspection method in accordance with SAE J2277 in lieu of 10X magnification. It is recommended to use hard peening media for these types of parts. 3.9 Peening Tw

43、o or More Thicknesses When two or more thicknesses are present on the same part and one is over 0.375 inch (9.52 mm) and the other is equal to or less than 0.375 inch (9.52 mm), the following method should be employed. The thicker area should be peened using the correct peening media size and intens

44、ity for that thickness. The thinner areas should be masked at any outside corner where the change of cross-section occurs. Masking is not required on an inside radius. If the change of cross-section is gradual, the peening coverage should fade within 2.0 inches (51 mm) into the thinner area. The thi

45、nner areas should next be peened to the correct intensity and peening media size with no masking of thicker sections, except as required by the drawing. Full/complete coverage with this second media size and intensity is required for not less than a 2.0 inch (51 mm) overlap into the area previously

46、peened. 3.10 Peening Media Type Refer to AMS2430 to match the nominal media size when a variation of peening media type is desired. Conditioned cut wire of the same size and hardness is often used interchangeably when cast steel shot was specified and when allowed by drawing or specification due to

47、its superior durability and satisfactory results in most applications. Other media types will require other considerations due to media mass and cleaning differences from steel media. 3.11 Test Strips The following test strip types shown in Table 5 are a guide for the indicated media types. Table 5

48、- Media and test strip types Media Type Test Strip Type Metallic N, A, C Glass N Ceramic N, A 3.12 Post-peening Considerations 3.12.1 The post peen cleaning method should be provided to the processor. After peening and removal of protective masks, all peening media and fragments should be removed fr

49、om surfaces of parts by a method that will not erode or scratch surfaces. Aluminum alloy, magnesium alloy, corrosion resistant steel alloy, and titanium alloy parts peened with steel peening media or any media in an unlined steel cabinet may be contaminated by iron and may be cleaned by chemical methods to dissolve the iron. Alternatively, glass media should only be used for decontamination when approved by the cognizant engineering orga