EP1714717A1 - Method of predicting damage of dies - Google Patents
Method of predicting damage of dies Download PDFInfo
- Publication number
- EP1714717A1 EP1714717A1 EP06008110A EP06008110A EP1714717A1 EP 1714717 A1 EP1714717 A1 EP 1714717A1 EP 06008110 A EP06008110 A EP 06008110A EP 06008110 A EP06008110 A EP 06008110A EP 1714717 A1 EP1714717 A1 EP 1714717A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- die
- formula
- dies
- brittle fracture
- predicting
- 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.)
- Granted
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J13/00—Details of machines for forging, pressing, or hammering
- B21J13/02—Dies or mountings therefor
Definitions
- the present invention concerns a method of predicting damages of dies. More specifically, the invention concerns predicting damages in dies for plastic processing of metals, typically, forging dies by predicting "great crack” damage caused by brittle fracture which dominates die lives, and utilizing the results for die design including choice of materials, hardness thereof and determining the die configuration so as to establish countermeasures for prolongation of die lives.
- Fracture factors causing damage of forging dies during using are four, namely, "great crack” or static brittle fracture, plastic flow, abrasion and low cycle fatigue destruction.
- the brittle fracture is a sudden phenomenon occurring at an initial stage before substantial use of the die, and also called “initial crack", which is a fatal damage.
- methods of predicting damage of dies proposed so far are not effective for this kind of brittle fracture.
- Cockroft's formula Oyane's formula and Ayada's formula, which have been acknowledged. These formulae are, however, not applicable to the brittle fracture.
- formula or formulae which enable effective prediction of damage of dies caused by brittle fracture.
- the object of the present invention is to provide a method of predicting damage of dies enabling design of improved dies by predicting brittle fracture which give, among various factors causing damage to forging die, fatal influence to die lives.
- the method according to the invention achieving the above-mentioned object is a method of predicting "great crack" by brittle fracture which dominates the lives of dies for plastic processing of metals to contribute to die design including choice of materials, hardness and configuration of the die.
- the method of predicting damages of dies according to the invention is characterized in that the die design is carried out by choosing the condition that none of the predicted values of brittle fracture, F c1 to F c3 , calculated by the formulae 1 to 3 below exceed the critical values determined on the basis of the material used.
- the method of predicting damages of dies according to the invention may exhibit the performance to the dies for forming. It will be, however, applicable to other dies such as those for die-casting, which are used under similar environment of high temperature and high stress. Through the prediction of damages of dies desired properties of die materials may be known as a matter of course and the indices for developing the die materials can be obtained. Thus, the invention may contribute to development of alloy technologies.
- SKD61 one of the steels for hot processing tools, was used as the die material and the hardness was adjusted to be HRC 46, 49 or 52.
- JIS No.4 tensile test pieces were prepared and some of them were subjected to machining to provide surrounding V-shaped notches of depth 50%. The shapes and dimensions of the test pieces are shown in Fig. 1 (smooth surface), Fig. 2 (notch angle 30°), Fig. 3 (90°) and Fig. 4 (120°). Curvature of the bottom of the notches is 0.2mm.
- the test pieces were subjected to tensile tests to determine mean normal stress ( ⁇ m ) at which fracture occurs and at the same time whether the fracture is ductile fracture or brittle fracture was recorded.
- the equivalent stress ( ⁇ eq ) and the maximum principal stress ( ⁇ 1max ) were calculated.
- Fig. 5 By plotting the mean normal stress ( ⁇ m ) in correspondence of the equivalent stress ( ⁇ eq ) there was obtained Fig. 5, by plotting the mean normal stress ( ⁇ m ) in correspondence of the maximum principal stress ( ⁇ 1max ), Fig. 6, and plotting the maximum principal stress ( ⁇ 1max ) in correspondence of the equivalent stress ( ⁇ eq ), Fig. 7, respectively.
- the prediction of die life according to the present invention was carried out in regard to a ring-die, a die for limiting the outer surface of the work forged by a punch and a counter punch from top and bottom used for hot forging a final gear, an automobile part, having the cross section shown in Fig. 8.
- a used die made of SKD61 steel was inspected and it was found that crack of the ring-die occurred from the outer surface.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Forging (AREA)
Abstract
σm: mean normal stress loaded to the tensile side of the
die
σeq : Von Misese's equivalent stress
σ1max : maximum principal stress
Description
- The present invention concerns a method of predicting damages of dies. More specifically, the invention concerns predicting damages in dies for plastic processing of metals, typically, forging dies by predicting "great crack" damage caused by brittle fracture which dominates die lives, and utilizing the results for die design including choice of materials, hardness thereof and determining the die configuration so as to establish countermeasures for prolongation of die lives.
- At manufacturing and application of forging dies various methods of predicting damages in dies have been developed and utilized for enabling manufacture of dies of longer lives. As the method of prediction it is generally employed to calculate temperature and stress distribution in a die by finite element analysis and then substitute the calculated values for constitutive equations to predict low cycle fatigue lives and abrasion. For example,
Japanese Patent Disclosure No. 2002-321032 - Fracture factors causing damage of forging dies during using are four, namely, "great crack" or static brittle fracture, plastic flow, abrasion and low cycle fatigue destruction. The brittle fracture is a sudden phenomenon occurring at an initial stage before substantial use of the die, and also called "initial crack", which is a fatal damage. However, methods of predicting damage of dies proposed so far are not effective for this kind of brittle fracture. As to ductile fracture there has been proposed Cockroft's formula, Oyane's formula and Ayada's formula, which have been acknowledged. These formulae are, however, not applicable to the brittle fracture. Thus, there has been demand for formula or formulae which enable effective prediction of damage of dies caused by brittle fracture.
- The object of the present invention is to provide a method of predicting damage of dies enabling design of improved dies by predicting brittle fracture which give, among various factors causing damage to forging die, fatal influence to die lives.
- The method according to the invention achieving the above-mentioned object is a method of predicting "great crack" by brittle fracture which dominates the lives of dies for plastic processing of metals to contribute to die design including choice of materials, hardness and configuration of the die. The method of predicting damages of dies according to the invention is characterized in that the die design is carried out by choosing the condition that none of the predicted values of brittle fracture, Fc1 to Fc3, calculated by the formulae 1 to 3 below exceed the critical values determined on the basis of the material used.
- σm: mean normal stress loaded to the tensile side of the
die - σeq: Von Misese's equivalent stress
- σ1max: maximum principal stress
-
- Fig. 1 is a plan view illustrating the shape and dimension of a smooth test piece of the tensile test pieces prepared for constructing database of the material properties prior to conducting the present invention;
- Fig. 2 is a plan view like Fig. 1 illustrating the shape and dimension of the test piece having a surrounding V-notch with notch angle of 30°;
- Fig. 3 is a plan view like a part of Fig. 2 illustrating the detail of the notched part of the test piece with notch angle of 90°;
- Fig. 4 is a plan view like a part of Fig. 3 illustrating the detail of the notched part of the test piece with notch angle of 120°;
- Fig. 5 is a graph obtained by plotting mean normal stress (σm) corresponding to equivalent stress (σeq) based on the data given by tensile tests in working example of the present invention;
- Fig. 6 is a graph obtained by plotting mean normal stress (σm) corresponding to maximum principal stress (σ1max) based on the data given by tensile tests in working example of the present invention;
- Fig. 7 is a graph obtained by plotting maximum principal stress (σ1max) corresponding to equivalent stress (σeq) based on the data given by tensile tests in working example of the present invention;
- Fig. 8 is a section view illustrating the shape of a ring-die and a work used at hot forging a final gear (an automobile part);
- Fig. 8 is data of a working example and a computer graphics (hereinafter referred to as "CG") obtained by FEM analysis showing distribution of the critical values Fc1 of brittle fracture in a ring-die before improvement by the invention;
- Fig 10 is a CG like Fig. 9 showing distribution of the critical values Fc2 of brittle fracture in a ring-die before improvement by the invention;
- Fig 11 is a CG like Fig. 9 showing distribution of the critical values Fc3 of brittle fracture in a ring-die before improvement by the invention;
- Fig 12 is a CG like Fig. 9 showing distribution of the critical values Fc1 of brittle fracture in a ring-die after improvement by the invention;
- Fig 13 is a CG like Fig. 9 showing distribution of the critical values Fc2 of brittle fracture in a ring-die before improvement by the invention;
- Fig 14 is a CG like Fig. 9 showing distribution of the critical values Fc3 of brittle fracture in a ring-die before improvement by the invention;
-
- All the dominating factors are considered in the above formulae 1 to 3. In practical use of these formulae an improved formula or formulae (such as those with adjusted coefficients) may be found by experience. They will give the same effect as those discussed above, and thus the invention includes the embodiments using such formulae.
- By predicting the damages of dies it will be possible to establish effective countermeasures to the brittle fracture (so-called "great crack" or "initial crack"), to which, though it is an important factor, no conventional method of predicting damages has not been confronted. Those skilled in the art will be able to manufacture the optimum die by constructing databases in regard to the respective steels with reference to the working examples described below, by choosing the condition where all the predicted brittle fracture values Fc1 to Fc3 do not reach the critical limits, and by designing the dies. If the dies enjoy prolonged lives it will contribute to decrease in processing costs of various forged products through not only reducing the die cost itself but also saving time and labor for exchanging the worn dies.
- The method of predicting damages of dies according to the invention may exhibit the performance to the dies for forming. It will be, however, applicable to other dies such as those for die-casting, which are used under similar environment of high temperature and high stress. Through the prediction of damages of dies desired properties of die materials may be known as a matter of course and the indices for developing the die materials can be obtained. Thus, the invention may contribute to development of alloy technologies.
- SKD61, one of the steels for hot processing tools, was used as the die material and the hardness was adjusted to be HRC 46, 49 or 52. JIS No.4 tensile test pieces were prepared and some of them were subjected to machining to provide surrounding V-shaped notches of depth 50%. The shapes and dimensions of the test pieces are shown in Fig. 1 (smooth surface), Fig. 2 (
notch angle 30°), Fig. 3 (90°) and Fig. 4 (120°). Curvature of the bottom of the notches is 0.2mm. - The test pieces were subjected to tensile tests to determine mean normal stress (σm) at which fracture occurs and at the same time whether the fracture is ductile fracture or brittle fracture was recorded. The equivalent stress (σeq) and the maximum principal stress (σ1max) were calculated. By plotting the mean normal stress (σm) in correspondence of the equivalent stress (σeq) there was obtained Fig. 5, by plotting the mean normal stress (σm) in correspondence of the maximum principal stress (σ1max), Fig. 6, and plotting the maximum principal stress (σ1max) in correspondence of the equivalent stress (σeq), Fig. 7, respectively.
-
- The prediction of die life according to the present invention was carried out in regard to a ring-die, a die for limiting the outer surface of the work forged by a punch and a counter punch from top and bottom used for hot forging a final gear, an automobile part, having the cross section shown in Fig. 8. A used die made of SKD61 steel was inspected and it was found that crack of the ring-die occurred from the outer surface.
-
- All the CG's showed that in some parts of outer surface of the ring-die Fc1 to Fc3 exceed the critical values. The fact agrees with the results of the above inspection.
- Then, supposing the cases where the outer diameter of the ring-die is increased to prevent the brittle fracture, the computer simulation was carried out again. Three CG's as mentioned below were obtained. The CG's showed that there existed no longer the parts where the Fc1 to Fc1 exceeded the critical values.
Claims (2)
- A method of predicting damage of dies used for plastic processing of metallic materials by predicting "great crack" caused by brittle fracture dominating the die lives so as to contribute to die design including choice of die materials, hardness of the material and determination of die shape, which comprises carrying out the die design by selecting the conditions that none of the anticipated brittle fracture values Fc1 to Fc3 calculated by the formulae below exceed the critical values depending on the materials:
where,σm: mean normal stress loaded to the tensile side of the
dieσeq : Von Misese's equivalent stressσ1max : maximum principal stress. - The method of predicting damage of die according to claim 1, wherein the material of the die is SKD61 steel and Fc1=0.7, Fc2=0.5 and Fc3=1.25.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2005120660A JP4556753B2 (en) | 2005-04-19 | 2005-04-19 | Mold damage prediction method |
Publications (2)
Publication Number | Publication Date |
---|---|
EP1714717A1 true EP1714717A1 (en) | 2006-10-25 |
EP1714717B1 EP1714717B1 (en) | 2008-04-02 |
Family
ID=36648542
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP06008110A Active EP1714717B1 (en) | 2005-04-19 | 2006-04-19 | Method of predicting damage of dies |
Country Status (4)
Country | Link |
---|---|
US (1) | US20060230881A1 (en) |
EP (1) | EP1714717B1 (en) |
JP (1) | JP4556753B2 (en) |
DE (1) | DE602006000842T2 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP6232934B2 (en) * | 2013-10-31 | 2017-11-22 | 新日鐵住金株式会社 | Material characteristic acquisition method and apparatus, program, and recording medium |
KR101867728B1 (en) * | 2016-12-21 | 2018-06-14 | 주식회사 포스코 | Mold design method |
JP6414770B1 (en) * | 2017-03-24 | 2018-10-31 | 日立金属株式会社 | Mold life prediction method |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2000246394A (en) * | 1999-03-02 | 2000-09-12 | Hitachi Metals Ltd | Life predicting method of die |
JP2002001475A (en) * | 2000-06-23 | 2002-01-08 | Toyota Motor Corp | Designing method for forging process |
JP2002321032A (en) * | 2001-04-27 | 2002-11-05 | Toyota Motor Corp | Metal die wear loss estimation apparatus, metal die wear loss estimation method, metal die wear loss estimation program, metal die life estimation apparatus, metal die life estimation method, metal die life estimation program, metal die wear loss detection apparatus and metal die life detection apparatus |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3848453A (en) * | 1970-08-04 | 1974-11-19 | Alusuisse | Die for shaping metals |
US4131596A (en) * | 1977-08-22 | 1978-12-26 | Logic Devices, Inc. | Sensing system and method for plastic injection molding |
US4574633A (en) * | 1983-02-04 | 1986-03-11 | Citizen Watch Company Limited | Apparatus for detecting tool damage in automatically controlled machine tool |
JPS63216942A (en) * | 1987-03-05 | 1988-09-09 | Sumitomo Electric Ind Ltd | Tool for warm and hot forgings |
JP3250696B2 (en) * | 1993-12-27 | 2002-01-28 | 本田技研工業株式会社 | Mold manufacturing method |
JP3800261B2 (en) * | 1996-12-13 | 2006-07-26 | 日立金属株式会社 | Method for predicting mold life and method for predicting optimum physical properties of mold material using the same |
US6572796B1 (en) * | 2000-10-27 | 2003-06-03 | General Electric Company | Method of predicting optimal injection molding cycle time |
JP2006326606A (en) * | 2005-05-23 | 2006-12-07 | Daido Steel Co Ltd | Method for predicting service life of metal die |
-
2005
- 2005-04-19 JP JP2005120660A patent/JP4556753B2/en not_active Expired - Fee Related
-
2006
- 2006-04-19 US US11/406,379 patent/US20060230881A1/en not_active Abandoned
- 2006-04-19 EP EP06008110A patent/EP1714717B1/en active Active
- 2006-04-19 DE DE602006000842T patent/DE602006000842T2/en not_active Expired - Fee Related
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2000246394A (en) * | 1999-03-02 | 2000-09-12 | Hitachi Metals Ltd | Life predicting method of die |
JP2002001475A (en) * | 2000-06-23 | 2002-01-08 | Toyota Motor Corp | Designing method for forging process |
JP2002321032A (en) * | 2001-04-27 | 2002-11-05 | Toyota Motor Corp | Metal die wear loss estimation apparatus, metal die wear loss estimation method, metal die wear loss estimation program, metal die life estimation apparatus, metal die life estimation method, metal die life estimation program, metal die wear loss detection apparatus and metal die life detection apparatus |
Non-Patent Citations (4)
Title |
---|
KIM ET AL: "Estimation of die service life against plastic deformation and wear during hot forging processes", JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, ELSEVIER, AMSTERDAM, NL, vol. 166, no. 3, 20 August 2005 (2005-08-20), pages 372 - 380, XP005023923, ISSN: 0924-0136 * |
PATENT ABSTRACTS OF JAPAN vol. 2000, no. 12 3 January 2001 (2001-01-03) * |
PATENT ABSTRACTS OF JAPAN vol. 2002, no. 05 3 May 2002 (2002-05-03) * |
PATENT ABSTRACTS OF JAPAN vol. 2003, no. 03 5 May 2003 (2003-05-05) * |
Also Published As
Publication number | Publication date |
---|---|
JP4556753B2 (en) | 2010-10-06 |
JP2006297429A (en) | 2006-11-02 |
DE602006000842T2 (en) | 2009-05-20 |
DE602006000842D1 (en) | 2008-05-15 |
US20060230881A1 (en) | 2006-10-19 |
EP1714717B1 (en) | 2008-04-02 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
Toenshoff et al. | Basics of cutting and abrasive processes | |
Vollertsen et al. | Size effects in manufacturing of metallic components | |
El-Axir | A method of modeling residual stress distribution in turning for different materials | |
Kalpakjian | Manufacturing processes for engineering materials | |
Parrington | Fractography of metals and plastics | |
Basak et al. | Numerical prediction of sheared edge profiles in sheet metal trimming using ductile fracture modeling | |
JP2009061477A (en) | Method for estimating stretch flange crack in thin plate press forming simulation | |
Sachnik et al. | Burr-free cutting edges by notch-shear cutting | |
Buchkremer et al. | Compilation of a thermodynamics based process signature for the formation of residual surface stresses in metal cutting | |
Hambli | BLANKSOFT: a code for sheet metal blanking processes optimization | |
Mkaddem et al. | Experimental approach and RSM procedure on the examination of springback in wiping-die bending processes | |
EP1714717B1 (en) | Method of predicting damage of dies | |
US20060260722A1 (en) | Method of predicting die lives | |
Pätzold et al. | Reducing the shear affected zone to improve the edge formability using a two-stage shear cutting simulation | |
Comaneci et al. | Damaging prediction of difficult-to-work aluminum alloys during equal channel angular pressing | |
Behrens et al. | Advanced finite element analysis of die wear in sheet-bulk metal forming processes | |
Zhao et al. | An improved ductile fracture criterion for fine-blanking process | |
Gautam et al. | Analysis of springback variation in V bending | |
Kim et al. | Simulation of shear fracture in sheet metal forming of thick plates under triaxial stress states | |
Hilditch et al. | Development of the sheared edge in the trimming of steel and light metal sheet: Part 2—Mechanisms and modeling | |
Gu et al. | A practical methodology to evaluate and predict edge cracking for advanced high-strength steel | |
EP1726381A1 (en) | Method for predicting damage of dies | |
Hambli et al. | Finite element prediction of blanking tool cost caused by wear | |
Tian et al. | Influencing factors of global and local deformation in hot compression | |
Abd AL-Kareem Ahmed et al. | Improvement of forging die life by failure mechanism analysis |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TR |
|
AX | Request for extension of the european patent |
Extension state: AL BA HR MK YU |
|
17P | Request for examination filed |
Effective date: 20070417 |
|
AKX | Designation fees paid |
Designated state(s): DE FR GB IT |
|
GRAP | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOSNIGR1 |
|
GRAS | Grant fee paid |
Free format text: ORIGINAL CODE: EPIDOSNIGR3 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE FR GB IT |
|
REG | Reference to a national code |
Ref country code: GB Ref legal event code: FG4D |
|
RIN1 | Information on inventor provided before grant (corrected) |
Inventor name: ITOH, SHIGEKAZU,C/O DAIDO STEEL CO., LTD. Inventor name: YOSHIDA, HIROAKI,C/O DAIDO STEEL CO., LTD. |
|
REF | Corresponds to: |
Ref document number: 602006000842 Country of ref document: DE Date of ref document: 20080515 Kind code of ref document: P |
|
ET | Fr: translation filed | ||
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
26N | No opposition filed |
Effective date: 20090106 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20090429 Year of fee payment: 4 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 20090629 Year of fee payment: 4 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 20100419 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST Effective date: 20101230 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20101103 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20100419 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: IT Payment date: 20090430 Year of fee payment: 4 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20100430 |