EP0612275A1 - Ameliorations apportees a la resistance a la fatigue de pieces decoupees - Google Patents

Ameliorations apportees a la resistance a la fatigue de pieces decoupees

Info

Publication number
EP0612275A1
EP0612275A1 EP92923501A EP92923501A EP0612275A1 EP 0612275 A1 EP0612275 A1 EP 0612275A1 EP 92923501 A EP92923501 A EP 92923501A EP 92923501 A EP92923501 A EP 92923501A EP 0612275 A1 EP0612275 A1 EP 0612275A1
Authority
EP
European Patent Office
Prior art keywords
hole
sheet
holes
stress
indentation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP92923501A
Other languages
German (de)
English (en)
Other versions
EP0612275A4 (fr
Inventor
Albert Koon-Siu Wong
Nikolas Rajic
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Commonwealth of Australia
Original Assignee
Commonwealth of Australia
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Commonwealth of Australia filed Critical Commonwealth of Australia
Publication of EP0612275A1 publication Critical patent/EP0612275A1/fr
Publication of EP0612275A4 publication Critical patent/EP0612275A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P9/00—Treating or finishing surfaces mechanically, with or without calibrating, primarily to resist wear or impact, e.g. smoothing or roughening turbine blades or bearings; Features of such surfaces not otherwise provided for, their treatment being unspecified
    • B23P9/02—Treating or finishing by applying pressure, e.g. knurling
    • B23P9/025—Treating or finishing by applying pressure, e.g. knurling to inner walls of holes by using axially moving tools
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D28/00—Shaping by press-cutting; Perforating
    • B21D28/24—Perforating, i.e. punching holes

Definitions

  • the invention is in relation to a method of improving the fatigue life of holes and areas which are to be cut out and in particular holes and cut-out portions in structures which are subjected to fatigue loading for example aerospace and aircraft applications.
  • the present invention also provides an apparatus for improving the fatigue life of holes and cut out areas.
  • holes are made to house the fastening means, such as rivets or bolts.
  • fastening means such as rivets or bolts.
  • holes are a source of localised weakness in the metal sheet or plate which* can lead to failure of the particular sheet or plate due to the formation and propagation of cracks from the hole.
  • the tubular sleeve may be removed.
  • the expanded tubular sleeve cannot be reused and is discarded after forming one hole. Due to the high manufacturing tolerances required for the production of such sleeves, their unit cost is high, and in cases where a large number is required (as in the case of a typical aircraft), the process becomes extremely costly to implement. Costs aside, there are further physical problems with the cold-working method. Whilst the cold-working method provides the desirable compressive stress around the hole, the compressive stress is not evenly distributed because of the split in the sleeve.
  • Another disadvantage of this method is that in using a tapered mandrel, a residual stress distribution which is non-symmetrical about the mid-plane of the material is created thus inducing a bending moment which, particularly in the case of thin sheets (generally less than 2.3 mm), causes local buckling of the material. Furthermore, the lack of out-of-plane constraints on the material during the expansion process often leaves a raised region at the periphery of the hole.
  • Another form of treatment commonly used on holes in aircraft manufacture is ring pad or stress coining. In the case of ring pad coining, a thin groove is formed which is spaced from and around an existing aperture in the structural member.
  • U.S. 3,110,086 to Austin Phillips granted 12 November, 1963 discloses a ring pad coining method.
  • the groove is formed by stamping, thereby cold-working the material and creating a residual compressive stress around the exterior of the hole.
  • the object of the present invention is to increase the fatigue life of the structural members containing holes and cut out portions but without some of the disadvantages of the prior art.
  • the present invention provides a method of improving the fatigue resistance of holes and cut out portions formed in material sheets wherein at least one area on at least one sheet where a hole is to be formed or a portion is to be cut out is compressed, most preferably forming an indentation, on at least one side and, preferably both sides, of the at least one sheet prior to the formation of the hole or the portion being cut out.
  • the compressive stress is created prior to the formation of the hole or the portion being cut out.
  • the method of the invention provides significantly improved fatigue life of holes in components. Preliminary tests illustrate at least a ten-fold increase in fatigue life of open holes. Furthermore, the method of the invention can be effectively used in relatively thin sheets since the undesirable effects of the prior art methods such as sheet buckling or peripheral deformations are significantly reduced. Similarly, by the same underlying physical principle, the fatigue life of cut out portions in which the stress critical locations have been treated by the invention will improve.
  • the method of the invention would be useful in any application where the fatigue resistance of the structure and containing a hole or holes is to be improved.
  • the method of the invention has general application in the manufacture of aircraft and aerospace equipment, where the fatigue resistance of the highly stressed structures and components thereof including the joining holes and stress critical locations, is of primary importance. Additionally, the method greatly enhances the fatigue resistance of a structure containing a hole or holes without additional weight which is most desirable in the aerospace and aircraft industries. It is also envisaged that the process will be useful in other applications such as in the manufacture of ships and other high performance (and highly stressed) vehicles and also in the manufacture of highly stressed process vessels and containers which have to withstand high pressures.
  • the method of the present invention can be used to enhance the fatigue resistance in thin sheets containing a hole or holes, the method can be used in any high performance and lightweight applications, for example, sports equipment such as tennis and squash racquet frames and motor sport structures.
  • the method of the invention can be applied to any material which exhibits an elasto-plastic stress-strain relationship, that is most metals and alloys for example, those of aluminium and steel.
  • the area on the sheet where the hole is to be formed is compressed from both sides by mandrels, thus most preferably forming indentations on both sides of the sheet.
  • the mandrels may be of any cross- sectional shape, i.e. square, hexagonal, round etc. and as such, the resulting hole formed may equally be of any shape.
  • the mandrels, apart from being flat or chamfered, may also be shaped in order to provide a countersink for the various types of fasteners.
  • the hole can be formed by any conventional method including drilling.
  • drilling one of the mandrels can be removed and the other can then be forced through to shear away the material and form the hole.
  • cut out portions once the stress critical locations have been compressed and most preferably indentations have been formed by the compression, the portion is then cut out as normal.
  • Figure 1 A sheet which requires a hole such that it can be fastened to another structure or sheet.
  • Figure 2 The same sheet as in Figure 1 with optional clamps applied to the sheet.
  • Figure 3 The mandrels in action around the sheet.
  • Figure 4 Optional step wherein one of the mandrels forms the hole.
  • Figure 5 The completed hole.
  • Figure 6 A pretreated (dimpled) sheet with mandrels being aligned for pre-hole compression.
  • Figure 7 A pretreated (pilot hole) sheet with mandrels being aligned for pre-hole compression.
  • Figure 8 An oversized hole compared to the indentations / mandrel size.
  • Figure 9 An undersized hole compared to the indentations / mandrel size.
  • Figure 10 Indented area to be cut out.
  • Figure 11 Cut out area.
  • Figure 12 A graph of the first set of comparative results between drilling, prior art cold working and the present invention.
  • Figure 13 A graph of another set of comparative results between drilling, prior art cold working and the present invention.
  • Figure 14 An illustration of the specimen used in the comparative examples of Figure 13.
  • sheet 10 which requires a hole 20 to be formed therein is clamped by clamps 11 in the vicinity of where the hole is to be made.
  • the holes 13 provided in clamps 11 outline the portion of the sheet 10, where the hole 20 is to be formed.
  • mandrels 12 which are guided by clamps 11 commence their compression and indentation on sheet 10. The top mandrel acting downwardly and the bottom mandrel acting upwardly in the direction of the arrows. It has been discovered that the degree of fatigue life improvement generally increases with an increase in indentation depth. Whilst this could also be true for the prior art methods, excessive indentation for the coining techniques, as previously stated, can lead to hole closure or even complete punch-out.
  • the mandrels 12 may then be removed and the hole 20 is formed by conventional methods such as drilling and the like. Alternatively, as is illustrated in Figure 4, only one of the mandrels 12 is removed and the other remaining mandrel stamps out the reduced section 14 to form the hole 20.
  • the restraining means or clamps 11 are not an essential part of the process, the use thereof further enhances the fatigue life by virtue of restricting any out-of-plane deformations thereby creating a greater region of residual stress than otherwise possible.
  • this restraining procedure results in the structure containing the hole or holes being relatively free from the distortions which are an undesirable by-product of the prior art cold expansion methods.
  • two sheets can be processed simultaneously, wherein as is illustrated in Figures 1-5, instead of item 10 being one sheet, item 10 is two separate sheets (not shown).
  • Mandrels 12 can then compress and most preferably form indentations on the two sheets simultaneously on a single side. Similarly, the mandrels 12 would be able to shear away the material (from both sheets) to form the holes in each sheet.
  • Figure 6 illustrates a sheet 10 which requires a hole 20 to be formed.
  • the sheet is preferably provided with location means (15,16).
  • the location means 15 is in the form of a dimple.
  • Figure 6 illustrates pre-hole indentation from only one side occurs prior to forming the hole.
  • the dimple 15 cooperates with protrusion 17 on the mandrel 12.
  • the provision of the location means 15 and cooperating protrusion 17 on the mandrel 12 assists in ensuring that the indentation is correctly positioned and that the hole area has been pretreated as required.
  • Figure 7 illustrates another form of location means 16 which is in the form of a pilot hole.
  • Figure 7 illustrates pre-hole indentation from both sides of the sheet 10.
  • pilot hole is just a location means to cooperate with and to assist in the centring of the mandrels and is not the actual fastening hole.
  • the pilot hole 16 (as do the dimples 15) assists in ensuring that the indentations are in the correct hole area and in the case of double-sided indentations, the indentations formed on both sides are correctly aligned.
  • the drill or punch size in order to form the hole would generally be the same size as the indentations formed, improved fatigue resistant results are also observed wherein the indentation is smaller or larger than the final hole size.
  • Figure 8 wherein the final hole 20 is larger than the indentations (shown in dotted lines).
  • the hole will be formed by drilling or by using a larger punch / mandrel than the indenting mandrels.
  • Figure 9 illustrates the situation wherein the final hole 20 is smaller than the indentations 18. Similarly, the hole is formed by drilling or by using a smaller punch / mandrel than the indenting mandrels. Additionally, whilst Figures 6 to 9 do not illustrate this feature, it is generally preferred that the sheet 10 be retained in position, by clamps or the like during the indentation and punching / drilling steps as was shown in Figures 2 to 4.
  • Figures 10 and 11 illustrate the application of the present invention to areas which are to be cut out.
  • Figure 10 illustrates sheet 110 wherein area 120 is to be cut out.
  • stress-critical locations of the area to be cut out are indented 121 in a similar manner as described and discussed in Figures 1 to 9 above.
  • the area is cut out using conventional techniques resulting in the cut out area 120 as illustrated in Figure 11.
  • the results of the tests are shown in Figures 12 and 13.
  • the results shown in Figure 12 were preliminary tests comparing the three processes, that is, drilled, cold-worked and the process of the present invention. All of the samples were the same, being dog-boned shaped specimens made from Aluminium 2024.
  • the dog-bone specimen used in these tests, (the results of which are illustrated in Figure 12) were substantially square in shape, wherein the specimen resembled a capital "I".
  • the hole was formed in the narrow portion of the dog-bone.
  • the cross-section in the relevant hole area of the samples was 41.5 mm x 1.6 mm. Each of the holes formed were 4 mm in diameter.
  • the prior art "drilled” method involved drilling the hole in the sample to 4 mm.
  • the 4 mm holes formed in the prior art "cold expanded” specimens were made using the Fatigue Technology Inc. (FTI) cold expansion process.
  • FTI Fatigue Technology Inc.
  • the specimens made by the present invention were compressed and indented by two mandrels (4 mm in diameter), each with a 25 kN load applied thereto, positioned on either side of the samples and guided by clamps which were holding the samples. The hole was punched using one of the mandrels. It should be noted that the indentation depths (and loading) vary with the type of material and hole size.
  • specimens produced by the method of the present invention began failing at the specimen edges (at the top and bottom portions of the dog-bone) and not the hole. Thus, the true lives of the holes produced by the method of the present invention is assumed to be higher than shown. On reviewing Figure 12, it can be seen that specimens produced by the present invention could withstand over double the number of cycles for a particular stress than the "cold expanded" holes and over ten times the number of cycles that a drilled hole could withstand.
  • FIG. 14 illustrates the sample used in the further tests.
  • the sample made of Aluminium 2024 had dimensions 175 x 60 x 1.6 mm wherein an arc of radius 85 mm was removed from each of the long sides of the sample, resulting in a smooth dog- bone shaped specimen.
  • the narrowest portion of the dog-bone was 45 mm.
  • the 4 mm hole was formed and centred at the narrowest portion.
  • the "drilled" and “cold expanded” specimens were made using the same processes as in the preliminary tests.
  • the specimens made by the present invention were compressed and indented by two mandrels (4 mm) each with a 16 kN load applied thereto, positioned on either side of the samples and guided by clamps which were holding the samples.
  • the specimens produced by the present invention failed at the specimen edges. However, where in the preliminary tests the specimens failed near the fixed end portions, the specimens of the subsequent tests failed closer to the neck or narrowest portion of sample.
  • the present invention also provides an apparatus for improving the fatigue resistance of holes and cut out portions in material sheets comprising a means for compressing and indenting at least one side of the sheet, preferably both sides.
  • the apparatus may also comprise restraining means or clamps to retain the sheet in position.
  • Mandrels are preferably used to compress and indent the sheet. Furthermore, one or both of the mandrels may be capable of stamping out the hole after indentation.
  • the present invention is a preventative manufacturing method which can be used when manufacturing structures which are prone to fatigue failures such as aircraft and other high performance and highly stressed components.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Forging (AREA)
  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
  • Shaping Metal By Deep-Drawing, Or The Like (AREA)
  • Pressure Welding/Diffusion-Bonding (AREA)
  • Drilling And Boring (AREA)

Abstract

L'invention concerne un procédé d'amélioration de la résistance à la fatigue de pièces trouées et découpées dans une tôle. Selon ce procédé, au minimum sur une zone de la tôle où un trou doit être fait ou une découpe réalisée, la tôle est comprimée de préférence en créant des entailles dues à ladite compression, sur au moins un côté et de préférence sur les deux côtés de la tôle. Le procédé est applicable de manière générale, mais il est particulièrement utile là où la tôle doit être utilisée dans des conditions de charge et de contraintes importantes, telles que dans les avions. L'invention concerne également un appareil améliorant la résistance à la fatigue des zones trouées et découpées dans la matière.
EP92923501A 1991-11-12 1992-11-12 Ameliorations apportees a la resistance a la fatigue de pieces decoupees. Withdrawn EP0612275A4 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
AUPK945591 1991-11-12
AU9455/91 1991-11-12
AUPL470392 1992-09-14
AU4703/92 1992-09-14
PCT/AU1992/000614 WO1993009890A1 (fr) 1991-11-12 1992-11-12 Ameliorations apportees a la resistance a la fatigue de pieces decoupees

Publications (2)

Publication Number Publication Date
EP0612275A1 true EP0612275A1 (fr) 1994-08-31
EP0612275A4 EP0612275A4 (fr) 1995-02-15

Family

ID=25644153

Family Applications (1)

Application Number Title Priority Date Filing Date
EP92923501A Withdrawn EP0612275A4 (fr) 1991-11-12 1992-11-12 Ameliorations apportees a la resistance a la fatigue de pieces decoupees.

Country Status (4)

Country Link
EP (1) EP0612275A4 (fr)
JP (1) JPH07500773A (fr)
CA (1) CA2121120A1 (fr)
WO (1) WO1993009890A1 (fr)

Families Citing this family (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6711928B1 (en) 1998-03-17 2004-03-30 Stresswave, Inc. Method and apparatus for producing beneficial stresses around apertures, and improved fatigue life products made by the method
US6230537B1 (en) 1998-03-17 2001-05-15 Stresswave, Inc. Method and apparatus for producing beneficial stresses around apertures by use of focused stress waves, and improved fatigue life products made by the method
EP1064118B1 (fr) 1998-03-17 2006-05-24 Stresswave, Inc. Procede et appareil de production de contraintes avantageuses autour d'ouvertures par l'emploi d'ondes d'effort focalisees
US7047786B2 (en) * 1998-03-17 2006-05-23 Stresswave, Inc. Method and apparatus for improving the fatigue life of components and structures
BR0108257A (pt) 2000-02-09 2003-03-05 Stresswave Inc Ferramental para trabalhar uma estrutura para aumentar a resistência à fadiga em uma localização selecionada na mencionada estrutura, método para trabalhar uma porção limìtrofe de material em uma estrutura, junta, método para fabricar uma junta aparelho para trabalhar a frio uma peça de trabalho, método para fabricar uma peça de trabalho para ter uma estrutura com maior vida sem fadiga, placa metálica, método para fazer uma parte de metal espessa, artigo de fabricação, e, parte acabada
WO2002024372A1 (fr) * 2000-09-22 2002-03-28 Stresswave, Inc. Procede et appareil pouvant ameliorer la duree de vie en fatigue de composants et de structures
JP2002240574A (ja) * 2001-02-21 2002-08-28 Unipres Corp エンジンマウント用ブラケット
US6698268B2 (en) 2002-03-18 2004-03-02 The Boeing Company Passive-adaptive indentor for stress wave cold working
JP5237032B2 (ja) 2008-09-29 2013-07-17 三菱重工業株式会社 金属部材製造方法、圧子及び金属部材製造装置
CN104117569A (zh) * 2014-07-02 2014-10-29 苏州市辰希特钣金制品有限公司 钣金双面冲孔装置
CN104148483A (zh) * 2014-07-21 2014-11-19 苏州璟瑜自动化科技有限公司 钣金双面冲孔装置
CN104148481A (zh) * 2014-07-21 2014-11-19 苏州璟瑜自动化科技有限公司 基于光电感应定位的冲孔装置
CN104148486A (zh) * 2014-07-21 2014-11-19 苏州璟瑜自动化科技有限公司 钣金冲孔头装置
FR3028780B1 (fr) * 2014-11-26 2017-03-24 Airbus Operations Sas Dispositif d'indentation de type aveugle pour ameliorer la tenue en fatigue d'un alesage
CN105710193A (zh) * 2014-12-03 2016-06-29 无锡市赛能微电机有限公司 微电机安装板的冲孔装置
CN105710196A (zh) * 2014-12-03 2016-06-29 无锡市赛能微电机有限公司 带裂纹反馈的微电机支架板的加工装置及方法
CN105710649A (zh) * 2014-12-03 2016-06-29 无锡市赛能微电机有限公司 基于阻抗检测与定位的电机架板的冲孔加工装置
US20160361753A1 (en) * 2015-06-11 2016-12-15 Ford Motor Company Method of tuning panels for commonality of self-piercing rivet/die and robot combinations
CN104923615A (zh) * 2015-06-22 2015-09-23 苏州璟瑜自动化科技有限公司 带双面冲孔与厚度检测的冲孔装置
CN104923619A (zh) * 2015-06-23 2015-09-23 苏州璟瑜自动化科技有限公司 基于钣金阻抗与光电传感定位的冲孔装置
CN104923627A (zh) * 2015-06-24 2015-09-23 苏州璟瑜自动化科技有限公司 带双面冲孔与厚度检测的冲孔装置及其方法
CN104923634A (zh) * 2015-06-24 2015-09-23 苏州璟瑜自动化科技有限公司 带光电定位与裂纹检测的钣金冲孔装置及其方法
KR20210117433A (ko) * 2020-03-19 2021-09-29 경북대학교 산학협력단 압흔을 이용한 미세 슬릿 가공방법
CN111975284B (zh) * 2020-08-20 2021-06-08 东风商用车有限公司 一种用于提高金属板材孔端疲劳强度的挤压模具及方法

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US2810191A (en) * 1956-06-25 1957-10-22 Hanna Engineering Works Method of prestressing metal plates
JPS56165527A (en) * 1980-05-26 1981-12-19 Toshiba Corp Coining method
JPH02151321A (ja) * 1988-12-05 1990-06-11 Nachi Fujikoshi Corp 金属材料の剪断加工方法
JPH02274414A (ja) * 1989-04-13 1990-11-08 Yutaka Giken Co Ltd 切断方法

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US3110086A (en) * 1960-02-15 1963-11-12 Douglas Aircraft Co Inc Coining structural parts
US3434327A (en) * 1966-11-01 1969-03-25 Mc Donnell Douglas Corp Stress coining
DE2549072C3 (de) * 1975-11-03 1982-05-27 Hillesheim, Hans, 6781 Höhfröschen Vorrichtung zur Herstellung von Durchbrüchen in Bandmaterial aus Metallblech
JPS52132490A (en) * 1976-04-30 1977-11-07 Yoshitaka Nakanishi Method of sinking counter sink in plate blank
US4711115A (en) * 1985-12-30 1987-12-08 Aluminum Company Of America Method for forming memory discs by forging

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Publication number Priority date Publication date Assignee Title
US2810191A (en) * 1956-06-25 1957-10-22 Hanna Engineering Works Method of prestressing metal plates
JPS56165527A (en) * 1980-05-26 1981-12-19 Toshiba Corp Coining method
JPH02151321A (ja) * 1988-12-05 1990-06-11 Nachi Fujikoshi Corp 金属材料の剪断加工方法
JPH02274414A (ja) * 1989-04-13 1990-11-08 Yutaka Giken Co Ltd 切断方法

Non-Patent Citations (4)

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Title
PATENT ABSTRACTS OF JAPAN vol. 14, no. 395 (M-1016) 27 August 1990 & JP-A-02 151 321 (NACHI) *
PATENT ABSTRACTS OF JAPAN vol. 15, no. 32 (M-1073) 25 January 1991 & JP-A-02 274 414 (YUTAKA) *
PATENT ABSTRACTS OF JAPAN vol. 6, no. 50 (M-120) 3 April 1982 & JP-A-56 165 527 (TOSHIBA) *
See also references of WO9309890A1 *

Also Published As

Publication number Publication date
JPH07500773A (ja) 1995-01-26
CA2121120A1 (fr) 1993-05-27
WO1993009890A1 (fr) 1993-05-27
EP0612275A4 (fr) 1995-02-15

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