JP2013186102A - Prediction method and prediction system of fracture strain of welding part, and method for manufacturing member including welding part - Google Patents

Prediction method and prediction system of fracture strain of welding part, and method for manufacturing member including welding part Download PDF

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JP2013186102A
JP2013186102A JP2012054118A JP2012054118A JP2013186102A JP 2013186102 A JP2013186102 A JP 2013186102A JP 2012054118 A JP2012054118 A JP 2012054118A JP 2012054118 A JP2012054118 A JP 2012054118A JP 2013186102 A JP2013186102 A JP 2013186102A
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JP5742755B2 (en
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Hideki Ueda
秀樹 上田
Eisuke Nakayama
英介 中山
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Nippon Steel Corp
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Abstract

PROBLEM TO BE SOLVED: To provide a method for predicting fracture strain of a welding part, capable of accurately predicting the fracture strain of a member composed of a steel type whose fracture strain is not still derived without performing a local fracture strain deriving process.SOLUTION: A fracture strain prediction method includes: a master curve determination step for collecting fracture strains of a plurality of steel types whose fracture strains are previously calculated in each material parameter specified by chemical components of each steel type and determining an approximate master curve of fracture strains from distribution of fracture strains; a material parameter calculation step for calculating a material parameter of a steel type to be evaluated by chemical components of the steel type to be evaluated; and a fracture strain calculation step for calculating fracture strain of the steel type to be evaluated by using the approximate master curve determined by the master curve determination step and the material parameter of the steel type to be evaluated which is calculated by the material parameter calculation step.

Description

本発明は、有限要素法解析(Finite Element Method解析、以下「FEM解析」という場合がある。)を用いた溶接部の破断ひずみの予測方法に関する。   The present invention relates to a method for predicting a fracture strain of a weld using a finite element method analysis (Finite Element Method analysis, hereinafter sometimes referred to as “FEM analysis”).

溶接、特にスポット溶接は、自動車組立工程における鋼板の接合方法として広く用いられている。スポット溶接で組み立てた部材においては、溶接ナゲット径や打点位置が適切でない場合、衝突変形中に溶接部が破断してエネルギー吸収性能の低下を招くことがある。部材の衝突エネルギー吸収性能の評価にはFEM解析が多用されているが、解析精度の向上にはスポット溶接部の破断を考慮することが重要であり、破断の発生を防ぐためのナゲット径、打点間隔の検討を可能にする方法が求められている。また、これらの検討は機械的特性が異なる多種の鋼板を対象に実施できることが望ましい。   Welding, particularly spot welding, is widely used as a method for joining steel plates in an automobile assembly process. In a member assembled by spot welding, if the welding nugget diameter and the spot position are not appropriate, the welded portion may break during collision deformation, leading to a decrease in energy absorption performance. FEM analysis is frequently used to evaluate the impact energy absorption performance of members, but it is important to consider the fracture of spot welds in order to improve the accuracy of analysis, and the nugget diameter and striking point to prevent the occurrence of fracture There is a need for a method that allows consideration of the interval. Moreover, it is desirable that these studies can be performed on various types of steel plates having different mechanical characteristics.

特許文献1、非特許文献1には、FEM解析により、スポット溶接部の母材及び/又は熱影響部(Heat Affected Zone、以下、「HAZ」という場合がある。)の破断判定値である破断ひずみを計算し、要素サイズを定めた要素サイズパラメータと破断ひずみとの関係を求め、この関係により所定の要素サイズパラメータの値から母材及び/又はHAZの破断ひずみを求める方法が開示されている。かかる技術によれば、解析モデルの形状及び/又はスポット溶接部のナゲット径、解析モデルの要素サイズに関係なく、要素のひずみに関する破断の判定基準を得ることができ、部材のスポット溶接部破断予測を精度良く行うことができる、とされている。   In Patent Document 1 and Non-Patent Document 1, the fracture determination value of the base material and / or heat affected zone (Heat Affected Zone, hereinafter sometimes referred to as “HAZ”) of the spot welded portion is obtained by FEM analysis. A method is disclosed in which a strain is calculated, a relationship between an element size parameter that defines an element size and a fracture strain is obtained, and a fracture strain of a base material and / or HAZ is obtained from a value of a predetermined element size parameter based on this relationship. . According to such a technique, it is possible to obtain a fracture criterion related to the strain of an element regardless of the shape of the analysis model and / or the nugget diameter of the spot weld and the element size of the analysis model, and predict the spot weld fracture of a member. Can be performed with high accuracy.

また、非特許文献2には、超小型試験片を用いた引張試験によりスポット溶接部の溶接金属部分、HAZ部分、母材部分それぞれの応力−歪み、引張強さ、破断伸び、破断絞りを個別かつ定量的に測定する方法や、その応力−歪み関係と破断絞りとから超小型試験片の引張試験を模擬したFEM解析によって各部位の局所的な破断ひずみを導出する方法が開示されている。かかる技術によれば、局所的な破断ひずみをスポット溶接部の各部位の破断基準としてFEM解析を行い、スポット溶接部の継手強度と破断部位とを高精度に予測することができる、とされている。   In Non-Patent Document 2, the stress-strain, tensile strength, breaking elongation, and drawing restriction of each of the weld metal part, HAZ part, and base metal part of the spot welded part are individually determined by a tensile test using an ultra-small test piece. In addition, a method of quantitatively measuring and a method of deriving a local breaking strain of each part by FEM analysis simulating a tensile test of a micro test piece from the stress-strain relationship and the fracture drawing are disclosed. According to such a technique, FEM analysis is performed using local fracture strain as a fracture criterion for each part of the spot welded part, and joint strength and fractured part of the spot welded part can be predicted with high accuracy. Yes.

特開2008−107322号公報JP 2008-107322 A

上田ら、自動車技術会論文集、Vol. 41、No. 4、(2010)、817-822Ueda et al., Automobile Engineering Society Proceedings, Vol. 41, No. 4, (2010), 817-822 中山ら、自動車技術会論文集、Vol. 36、No. 1、(2005)、205-210Nakayama et al., Automobile Engineering Society Proceedings, Vol. 36, No. 1, (2005), 205-210

特許文献1、非特許文献1に記載の技術では、スポット溶接継手の引張試験結果とFEM解析結果とから破断ひずみを求めている。具体的には、試験結果の最大荷重とFEM解析結果の荷重とが一致した変位での相当塑性歪みを破断ひずみとして算出する。したがって、この方法ではスポット溶接継手の引張試験結果と整合性を取りながら破断ひずみを求めるため、スポット溶接継手の引張試験条件を対象にした破断予測には適していない。また、板の平面方向のみを考慮した二次元的なシェル要素でモデルを作成するため、板厚方向への亀裂進展等、詳細な破断因子の検討をすることができない。   In the techniques described in Patent Document 1 and Non-Patent Document 1, the fracture strain is obtained from the tensile test result and the FEM analysis result of the spot welded joint. Specifically, the equivalent plastic strain at the displacement in which the maximum load of the test result matches the load of the FEM analysis result is calculated as the fracture strain. Accordingly, this method is not suitable for fracture prediction for the spot test joint tensile test conditions because the fracture strain is obtained while maintaining consistency with the spot weld joint tensile test result. In addition, since a model is created with a two-dimensional shell element considering only the plane direction of the plate, it is not possible to examine detailed fracture factors such as crack growth in the plate thickness direction.

一方、非特許文献2に記載の技術では、特許文献1や非特許文献1に記載の技術とは異なり、スポット溶接継手の引張試験条件を対象にした破断予測と、詳細な破断因子の検討が可能である。しかしながら、鋼種により破断ひずみが異なる場合があり、鋼種毎に超小型試験片の引張試験結果とFEM解析結果から局所的な破断ひずみを求めている(以下、この処理を「局所的破断ひずみ導出プロセス」という場合がある。)。したがって、破断ひずみが未導出である鋼種からなる部材を対象に破断予測FEM解析を行う場合、当該鋼種について、事前に局所的破断ひずみ導出プロセスが必要となる。局所的破断ひずみ導出プロセスの増加は、作業時間と人的労力を要し問題であった。   On the other hand, the technique described in Non-Patent Document 2 differs from the techniques described in Patent Document 1 and Non-Patent Document 1 in that it predicts breakage for tensile test conditions of spot welded joints and examines detailed breakage factors. Is possible. However, the fracture strain may vary depending on the steel type, and the local fracture strain is obtained from the tensile test result and FEM analysis result of the ultra-small specimen for each steel type (hereinafter, this process is referred to as “local fracture strain derivation process”). "). Therefore, when the fracture prediction FEM analysis is performed on a member made of a steel type for which the fracture strain has not been derived, a local fracture strain deriving process is required for the steel type in advance. The increase in the local fracture strain derivation process has been a problem requiring work time and human labor.

そこで本発明は、破断ひずみが未導出である鋼種からなる部材について、局所的破断ひずみ導出プロセスを行わずに破断ひずみを精度良く予測することが可能な、溶接部の破断ひずみの予測方法、予測システム、及び当該破断ひずみの予測方法や予測システムを用いてFEM解析を行い、解析結果に基づいて、溶接部を備えた部材を製造する方法を提供することを課題とする。   Therefore, the present invention provides a method for predicting a fracture strain of a welded portion, which can accurately predict a fracture strain without performing a local fracture strain derivation process for a member made of a steel type from which a fracture strain has not been derived. It is an object of the present invention to provide a method of manufacturing a member having a welded portion based on the analysis result by performing FEM analysis using the system and the fracture strain prediction method and prediction system.

本発明者が鋭意研究したところ、代表的な母材強度クラスの鋼種を対象に、あらかじめ、破断ひずみを複数導出して破断ひずみ基準データとし、且つ、これらを各鋼種の化学成分に基づいて算出したパラメータで整理することにより、破断ひずみ基準データと各鋼種の当該パラメータとの関係が、累乗近似等のマスターカーブで近似できることを知見した。これにより、破断ひずみが未導出である鋼種であっても、当該鋼種の化学成分が分かっていれば、マスターカーブを用いて容易に破断ひずみを予測することができる。   As a result of extensive research by the inventor of the present invention, a plurality of fracture strains are derived in advance for representative steel grades of the base metal strength class and used as fracture strain reference data, and these are calculated based on the chemical composition of each steel grade. It was found that the relationship between the fracture strain reference data and the relevant parameter of each steel type can be approximated by a master curve such as a power approximation by organizing with the obtained parameters. Thereby, even if it is the steel grade from which the fracture | rupture distortion | strain has not been derived | led-out, if the chemical component of the said steel grade is known, a fracture | rupture distortion | strain can be easily estimated using a master curve.

本発明は、上記知見に基づいてなされたものである。すなわち、
本発明の第1の態様は、有限要素法解析により溶接部の破断予測を実施する際に用いられる、破断ひずみの予測方法であって、あらかじめ破断ひずみが算出された複数の鋼種について、該破断ひずみを、該鋼種の化学成分により特定される材質パラメータ毎にまとめ、該破断ひずみの分布から破断ひずみの近似マスターカーブを決定する、マスターカーブ決定工程と、評価対象となる鋼種の化学成分により、該評価対象となる鋼種の材質パラメータを算出する、材質パラメータ算出工程と、マスターカーブ決定工程により決定された近似マスターカーブと材質パラメータ算出工程により算出された評価対象となる鋼種の材質パラメータとを用いて、該評価対象となる鋼種の破断ひずみを算出する、破断ひずみ算出工程とを備える、破断ひずみの予測方法である。
The present invention has been made based on the above findings. That is,
A first aspect of the present invention is a method for predicting fracture strain used when carrying out fracture prediction of a welded portion by finite element method analysis, and for a plurality of steel types whose fracture strain is calculated in advance, the fracture Summarize the strain for each material parameter specified by the chemical composition of the steel grade, determine the approximate master curve of the fracture strain from the fracture strain distribution, and the master curve determination step and the chemical composition of the steel grade to be evaluated, Using the material parameter calculation step for calculating the material parameter of the steel type to be evaluated, the approximate master curve determined by the master curve determination step, and the material parameter of the steel type to be evaluated calculated by the material parameter calculation step And a fracture strain calculating step for calculating a fracture strain of the steel type to be evaluated. It is a prediction method.

本発明において、「溶接部」とは、特に鋼材の溶接部分とすることが好ましく、溶接金属部分(或いはナゲット部分)、HAZ部分、母材部分に大別することができる。「破断ひずみ」とは、従来においては局所的破断ひずみ導出プロセスにより導出されていたものであり、例えば、溶接部における母材部分の破断ひずみ、HAZ部分の破断ひずみ、溶接金属部分の破断ひずみ等を挙げることができる。また、特許文献1、非特許文献1に記載の「破断ひずみ」はスポット溶接部に限定したものであるが、本発明における「破断ひずみ」とはレーザ溶接等のその他溶接手段における溶接部にも適用可能な破断判定の基準値である。「あらかじめ破断ひずみが導出された複数の鋼種」とは、例えば、局所的破断ひずみ導出プロセスによって破断ひずみが既知である複数の鋼種を意味する。「近似マスターカーブ」とは、破断ひずみと材質パラメータとの関係を示す近似曲線を意味する。尚、本発明において「近似マスターカーブ」は直線(一次関数)で示されるものであってもよい。「材質パラメータ」とは、破断ひずみと相関関係のある、鋼種の化学成分により設定されたパラメータをいい、詳しくは後述する。尚、本発明において、「化学成分」とは、鋼種に含まれる成分の質量%濃度やモル濃度、体積%濃度や組成比等を挙げることができる。   In the present invention, the “welded part” is particularly preferably a welded part of steel material, and can be roughly divided into a welded metal part (or nugget part), a HAZ part, and a base material part. The “breaking strain” is conventionally derived by a local breaking strain deriving process. For example, the breaking strain of the base metal portion in the welded portion, the breaking strain of the HAZ portion, the breaking strain of the weld metal portion, etc. Can be mentioned. In addition, the “breaking strain” described in Patent Document 1 and Non-Patent Document 1 is limited to a spot welded portion, but the “breaking strain” in the present invention is also applied to a welded portion in other welding means such as laser welding. It is a reference value for applicable break determination. “A plurality of steel types whose fracture strain has been derived in advance” means, for example, a plurality of steel types whose fracture strain is known by a local fracture strain deriving process. The “approximate master curve” means an approximate curve indicating the relationship between fracture strain and material parameters. In the present invention, the “approximate master curve” may be a straight line (linear function). “Material parameter” refers to a parameter set by the chemical composition of the steel type, which has a correlation with the fracture strain, and will be described in detail later. In the present invention, examples of the “chemical component” include mass% concentration, molar concentration, volume% concentration, composition ratio, and the like of the component contained in the steel type.

本発明の第1の態様において、溶接部が、複数の異なる鋼種を接合した溶接部である場合、破断ひずみの予測に用いられる材質パラメータが、溶接部におけるそれぞれの鋼種の体積比と化学成分とにより特定・算出されることが好ましい。   In the first aspect of the present invention, when the welded portion is a welded portion obtained by joining a plurality of different steel types, the material parameters used for predicting the breaking strain are the volume ratio and chemical composition of each steel type in the welded portion. Is preferably specified and calculated by

本発明の第2の態様は、有限要素法解析により溶接部の破断予測を実施する際に用いられる、破断ひずみの予測システムであって、複数の鋼種の破断ひずみを蓄積したデータベースと、データベースから選択された複数の破断ひずみを、化学成分により特定される材質パラメータ毎にまとめ、該破断ひずみの分布から破断ひずみの近似マスターカーブを決定する、マスターカーブ決定手段と、評価対象となる鋼種の化学成分により、該評価対象となる鋼種の材質パラメータを算出する、材質パラメータ算出手段と、マスターカーブ決定手段により決定された近似マスターカーブと材質パラメータ算出手段により算出された評価対象となる鋼種の材質パラメータとを用いて、該評価対象となる鋼種の破断ひずみを算出する、破断ひずみ算出手段とを備える、破断ひずみの予測システムである。   The second aspect of the present invention is a fracture strain prediction system used when carrying out fracture prediction of a welded portion by finite element method analysis, a database storing fracture strains of a plurality of steel types, and a database. A master curve determining means for collecting a plurality of selected fracture strains for each material parameter specified by a chemical component and determining an approximate master curve of the fracture strain from the fracture strain distribution, and a chemistry of a steel type to be evaluated The material parameter of the steel type to be evaluated calculated by the material parameter calculation means, the approximate master curve determined by the master curve determination means, and the material parameter calculation means for calculating the material parameter of the steel type to be evaluated by the component Rupture strain calculating means for calculating the rupture strain of the steel type to be evaluated It comprises a prediction system for strain at break.

本発明の第3の態様は、本発明の第1の態様に係る破断ひずみの予測方法により予測された破断ひずみを用いて有限要素法解析を行い、解析結果に基づいて部材の板組み、溶接部の大きさ及び/又は溶接位置を決定し、該決定された板組み、溶接部の大きさ及び/又は溶接位置にしたがって部材を溶接する工程を備える、溶接部を備えた部材の製造方法である。   According to a third aspect of the present invention, a finite element method analysis is performed using the fracture strain predicted by the fracture strain prediction method according to the first aspect of the present invention. A method for manufacturing a member having a welded portion, comprising: determining a size and / or a welding position of the portion, and welding the member according to the determined plate assembly, the size and / or the welding position of the welded portion. is there.

本発明においては、破断ひずみと鋼種の材質パラメータとの関係を、近似マスターカーブとして数式化する。これにより、破断ひずみが未導出である鋼種の破断ひずみを算出・予測する場合であっても、鋼種の材質パラメータを特定すれば近似マスターカーブを用いて破断ひずみを容易に算出・予測することができる。すなわち、本発明によれば、破断ひずみが未導出である鋼種からなる部材に対しても、局所的破断ひずみ導出プロセスを行わずに破断ひずみを精度良く予測することが可能な、溶接部の破断ひずみの予測方法、予測システム、及び当該破断ひずみの予測方法や予測システムを用いて、溶接部を備えた部材を製造する方法を提供することができる。   In the present invention, the relationship between the breaking strain and the material parameter of the steel type is expressed as an approximate master curve. As a result, even when the fracture strain of a steel grade for which the fracture strain has not been derived is calculated and predicted, if the material parameters of the steel grade are specified, the fracture strain can be easily calculated and predicted using an approximate master curve. it can. That is, according to the present invention, it is possible to accurately predict the fracture strain without performing a local fracture strain derivation process even for a member made of a steel type from which the fracture strain has not yet been derived. It is possible to provide a method for manufacturing a member having a welded portion using a strain prediction method, a prediction system, and a fracture strain prediction method or prediction system.

本発明に係る破断ひずみの予測方法の一例を示す図である。It is a figure which shows an example of the prediction method of the fracture | rupture distortion which concerns on this invention. 溶接金属の破断ひずみと材質パラメータParamPEwmとの関係を示す図である。It is a figure which shows the relationship between the fracture strain of a weld metal, and the material parameter ParamPEwm. HAZの破断ひずみと材質パラメータParamPEhazとの関係を示す図である。It is a figure which shows the relationship between the fracture | rupture distortion | strain of HAZ, and the material parameter ParamPEhaz. 母材の破断ひずみと材質パラメータParamPEbmとの関係を示す図である。It is a figure which shows the relationship between the fracture | rupture distortion of a base material, and the material parameter ParamPEbm. スポット溶接継手引張試験条件のFEM解析において、本発明に係る破断ひずみの予測方法を適用した例を説明するための図である。It is a figure for demonstrating the example which applied the prediction method of the fracture | rupture distortion based on this invention in the FEM analysis of spot-welded joint tension test conditions. スポット溶接継手引張試験条件のFEM解析において、本発明に係る破断ひずみの予測方法を適用した解析結果の例を説明するための図である。It is a figure for demonstrating the example of the analysis result which applied the prediction method of the fracture | rupture distortion which concerns on this invention in the FEM analysis of spot-welded joint tension test conditions. レーザ溶接継手引張試験条件のFEM解析において、本発明に係る破断ひずみの予測方法を適用した解析結果の例を説明するための図である。It is a figure for demonstrating the example of the analysis result which applied the prediction method of the fracture | rupture distortion based on this invention in the FEM analysis of a laser-welded joint tension test condition. レーザ溶接継手引張試験条件のFEM解析において、本発明に係る破断ひずみの予測方法を適用した解析結果の例を説明するための図である。It is a figure for demonstrating the example of the analysis result which applied the prediction method of the fracture | rupture distortion based on this invention in the FEM analysis of a laser-welded joint tension test condition. 本発明に係る破断ひずみの予測システムの一例を示す図である。It is a figure which shows an example of the prediction system of the fracture | rupture distortion which concerns on this invention.

1.本発明完成までの経緯
上記非特許文献2によれば、超小型試験片の引張試験を模擬したFEM解析結果の試験部断面積が破断試験片での実測値に達したときの最大相当塑性ひずみを、その試験片の局所的な破断ひずみと定義できる。また、このプロセスを溶接金属、HAZ、母材毎に行うことで、各部位での破断ひずみを導出することができる。
1. Background to the completion of the present invention According to Non-Patent Document 2, the maximum equivalent plastic strain when the cross-sectional area of the test part of the FEM analysis result simulating the tensile test of a micro test specimen reaches the actual measurement value of the fracture test specimen. Can be defined as the local breaking strain of the specimen. Further, by performing this process for each weld metal, HAZ, and base material, it is possible to derive the fracture strain at each part.

鉄鋼材料では、炭素以外の元素の影響力を炭素量に換算した炭素当量という指標があり、鉄鋼材料の引張強さに対応したもの、溶接部硬さに対応したもの等がある。このように、鉄鋼材料では、化学成分と機械的特性との間に相関性があると考えられている。一方、引張試験において、破断試験片の断面積は破断絞りに換算される。破断絞りは機械的特性の一つであるため、本発明者らは、破断絞り及びそれから導出される破断ひずみと化学成分との間にも相関性があると考えた。そこで、非特許文献3(山内ら、住友金属、Vol. 33、No. 4、(1989)、109-120)に記載の下記式(1)で表される炭素当量に、非特許文献4(N. J. den Uijlら、Welding Research Abroad、Vol. 55、(2009)、1-12)に記載のP及びSの影響度合いを追加した下記式(2)をベースにして、炭素以外の元素の割合を最小二乗法により適正化を図り、材質パラメータとして設定したところ、当該材質パラメータと破断ひずみとの関係が累乗曲線等のマスターカーブで近似できることを知見した。
Ceq=C+Si/90+(Mn+Cr)/100 …(1)
Ceq=C+Si/90+(Mn+Cr)/100+1.5P+3S …(2)
In steel materials, there is an index called carbon equivalent in which the influence of elements other than carbon is converted into carbon content, and there are materials corresponding to the tensile strength of steel materials and materials corresponding to the hardness of welds. Thus, in steel materials, it is considered that there is a correlation between chemical components and mechanical properties. On the other hand, in the tensile test, the cross-sectional area of the fracture test piece is converted into a fracture drawing. Since the fracture drawing is one of the mechanical properties, the present inventors considered that there is also a correlation between the fracture drawing and the fracture strain derived therefrom and the chemical composition. Therefore, in the carbon equivalent represented by the following formula (1) described in Non-Patent Document 3 (Yamauchi et al., Sumitomo Metals, Vol. 33, No. 4, (1989), 109-120), Non-Patent Document 4 ( NJ den Uijl et al., Welding Research Abroad, Vol. 55, (2009), 1-12), based on the following formula (2) to which the degree of influence of P and S is added, As a result of optimization by the least square method and setting as a material parameter, it was found that the relationship between the material parameter and the fracture strain can be approximated by a master curve such as a power curve.
Ceq = C + Si / 90 + (Mn + Cr) / 100 (1)
Ceq = C + Si / 90 + (Mn + Cr) /100+1.5P+3S (2)

本発明は上記知見に基づいてなされたものである。すなわち、本発明においては、溶接部の破断部位(例えば、溶接金属部分、HAZ部分、母材部分)に係る破断ひずみについて、材質パラメータとして鋼種の化学成分を用いることで、当該材質パラメータと破断ひずみとの関係を近似マスターカーブで表すことができ、当該近似マスターカーブを用いることにより、破断ひずみが未導出である鋼種に対しても、当該鋼種の化学成分を特定するだけで、当該鋼種の溶接部の破断部位に係る破断ひずみを適切に導出・予測することができる。   The present invention has been made based on the above findings. That is, in the present invention, the chemical parameters of the steel type are used as material parameters for the fracture strains related to fracture sites (for example, weld metal portions, HAZ portions, and base metal portions) of the welded portion. Can be expressed by an approximate master curve, and by using the approximate master curve, welding of the steel type can be performed only by specifying the chemical composition of the steel type even for a steel type for which the fracture strain has not been derived. It is possible to appropriately derive and predict the breaking strain related to the breaking portion of the part.

以下、実施形態に係る本発明について詳述する。   Hereinafter, the present invention according to the embodiment will be described in detail.

2.スポット溶接部の破断ひずみの予測方法
第1実施形態に係る本発明の破断ひずみの予測方法S10(以下、単に「予測方法S10」という。)を図1に示す。図1に示すように、予測方法S10は、あらかじめ破断ひずみが導出された複数の鋼種について、当該破断ひずみを、鋼種の化学成分により特定される材質パラメータ毎にまとめ、破断ひずみの分布から破断ひずみの近似マスターカーブを決定する、マスターカーブ決定工程S1と、評価対象となる鋼種の化学成分により、評価対象となる鋼種の材質パラメータを算出する、材質パラメータ算出工程S2と、マスターカーブ決定工程S1により決定された近似マスターカーブ、及び、材質パラメータ算出工程S2により算出された評価対象となる鋼種の材質パラメータを用いて、当該評価対象となる鋼種の破断ひずみを算出する、破断ひずみ算出工程S3とを備えている。
2. Method for Predicting Breaking Strain of Spot Welded Section FIG. 1 shows a breaking strain prediction method S10 (hereinafter simply referred to as “prediction method S10”) according to the first embodiment of the present invention. As shown in FIG. 1, the prediction method S10 summarizes the breaking strain for each material parameter specified by the chemical component of the steel type for a plurality of steel types for which the breaking strain has been derived in advance, and determines the breaking strain from the distribution of the breaking strain. The master curve determination step S1 for determining the approximate master curve of the material, the material parameter calculation step S2 for calculating the material parameter of the steel type to be evaluated by the chemical component of the steel type to be evaluated, and the master curve determination step S1 Using the determined approximate master curve and the material parameter of the steel type to be evaluated calculated in the material parameter calculating step S2, the fracture strain calculating step S3 for calculating the breaking strain of the steel type to be evaluated I have.

2.1.マスターカーブ決定工程S1(工程S1)
工程S1は、あらかじめ破断ひずみが導出された複数の鋼種について、当該破断ひずみを、鋼種の化学成分により特定される材質パラメータ毎にまとめ、破断ひずみの分布から破断ひずみの近似マスターカーブを決定する工程である。以下、工程S1の具体例として、局所的破断ひずみ導出プロセスによって破断ひずみが既知である複数の鋼種として母材強度クラス270MPa級〜980MPa級の鋼板及び1500MPa級の熱間プレス鋼板を用い、近似マスターカーブを決定した例を示す。
2.1. Master curve determination step S1 (step S1)
Step S1 is a step of determining the approximate master curve of the fracture strain from the distribution of the fracture strain by collecting the fracture strain for each material parameter specified by the chemical component of the steel grade for a plurality of steel types for which the fracture strain has been derived in advance. It is. Hereinafter, as a specific example of the step S1, using a steel material of a base material strength class of 270 MPa class to 980 MPa class and a hot pressed steel sheet of 1500 MPa class as a plurality of steel types whose fracture strain is known by a local fracture strain derivation process, an approximate master An example in which a curve is determined is shown.

溶接金属部分、HAZ部分、母材部分の各部位の破断ひずみの分布については、まず、式(2)で算出した炭素当量を材質パラメータとして整理し、破断ひずみの分布を近似する累乗曲線から算出した近似破断ひずみと、局所的破断ひずみ導出プロセスで求めた破断ひずみとの誤差を判定し、最小二乗法で適正化を図り、炭素以外の元素の割合をそれぞれ決定する。その結果、溶接金属部分の破断ひずみの分布については材質パラメータParamPEwm、HAZ部分の破断ひずみの分布については材質パラメータParamPEhaz、母材の破断ひずみの分布については材質パラメータParamPEbmで各々整理することができる。   Regarding the fracture strain distribution of each part of the weld metal part, HAZ part, and base metal part, first, the carbon equivalent calculated by Equation (2) is arranged as a material parameter, and calculated from a power curve that approximates the fracture strain distribution. The error between the calculated approximate breaking strain and the breaking strain obtained in the local breaking strain derivation process is determined, optimization is performed by the least square method, and the ratio of elements other than carbon is determined. As a result, the distribution of fracture strain in the weld metal portion can be arranged by the material parameter ParamPEwm, the distribution of fracture strain in the HAZ portion by the material parameter ParamPEhaz, and the distribution of fracture strain of the base material by the material parameter ParamPEbm.

ParamPEwm、ParamPEhaz、ParamPEbmは、化学成分により特定される材質パラメータであり、それぞれ、下記式(3)〜(5)を用いて算出することができる。
ParamPEwm=C+a×Si+b×Mn+c×Cr+d×P+e×S …(3)
ParamPEhaz=C+a×Si+b×Mn+c×Cr+d×P+e×S …(4)
ParamPEbm=C+a×Si+b×Mn+c×Cr+d×P+e×S …(5)
ParamPEwm, ParamPEhaz, ParamPEbm are material parameters specified by chemical components, and can be calculated using the following equations (3) to (5), respectively.
ParamPEwm = C + a 3 × Si + b 3 × Mn + c 3 × Cr + d 3 × P + e 3 × S (3)
ParamPEhaz = C + a 4 × Si + b 4 × Mn + c 4 × Cr + d 4 × P + e 4 × S (4)
ParamPEbm = C + a 5 × Si + b 5 × Mn + c 5 × Cr + d 5 × P + e 5 × S (5)

上記式(3)〜(5)において、a、b、c、d、e、a、b、c、d、e、a、b、c、d、eは定数であり、具体的にはa、a、a=0.0〜0.2、b、b、b=0.0〜0.1、c、c、c=0.0〜0.01、d、d、d=0.0〜10.0、e、e、e=0.0〜20.0である。これらの定数の導出方法としては、上記した通り、破断ひずみの分布が累乗近似等の近似曲線に沿うよう、最小二乗法を用いて適宜決定することができる。 In the above formulas (3) to (5), a 3 , b 3 , c 3 , d 3 , e 3 , a 4 , b 4 , c 4 , d 4 , e 4 , a 5 , b 5 , c 5 , d 5 and e 5 are constants, specifically, a 3 , a 4 , a 5 = 0.0 to 0.2, b 3 , b 4 , b 5 = 0.0 to 0.1, c 3 , C 4 , c 5 = 0.0 to 0.01, d 3 , d 4 , d 5 = 0.0 to 10.0, e 3 , e 4 , e 5 = 0.0 to 20.0. . As a method for deriving these constants, as described above, the constant can be appropriately determined by using the least square method so that the distribution of fracture strain follows an approximate curve such as a power approximation.

このように、新たに材質パラメータを設定した場合、図2〜4に示すように、溶接金属部分の破断ひずみ(CrPEwm)と材質パラメータParamPEwmとの関係についてはマスターカーブMwmにより近似することができ、HAZ部分の破断ひずみ(CrPEhaz)と材質パラメータParamPEhazとの関係についてはマスターカーブMhazにより近似することができ、母材部の破断ひずみ(CrPEbm)と材質パラメータParamPEbmとの関係についてはマスターカーブMbmにより近似することができる。近似マスターカーブは公知の表計算ソフトウェア等を用いて決定することができる。図2〜4におけるマスターカーブMwm、Mhaz、Mbmを数式化すると、具体的には下記式(6)〜(8)となる。
Mwm: CrPEwm = 0.4714×ParamPEwm−0.3206 …(6)
Mhaz: CrPEhaz = 0.566×ParamPEhaz−0.2671 …(7)
Mbm: CrPEbm = 0.3973×ParamPEbm−0.5155 …(8)
Thus, when a new material parameter is set, as shown in FIGS. 2 to 4, the relationship between the fracture strain (CrPEwm) of the weld metal part and the material parameter ParamPEwm can be approximated by the master curve Mwm, The relationship between the fracture strain (CrPEhaz) of the HAZ part and the material parameter ParamPEhaz can be approximated by the master curve Mhaz, and the relationship between the fracture strain (CrPEbm) of the base material portion and the material parameter ParamPEbm is approximated by the master curve Mbm. can do. The approximate master curve can be determined using known spreadsheet software or the like. When formulating the master curves Mwm, Mhaz, and Mbm in FIGS. 2 to 4, specifically, the following equations (6) to (8) are obtained.
Mwm: CrPEwm = 0.4714 × ParamPEwm− 0.3206 (6)
Mhaz: CrPEhaz = 0.566 x ParamPEhaz -0.2671 (7)
Mbm: CrPEbm = 0.3973 × ParamPEbm− 0.5155 (8)

2.2.材質パラメータ算出工程(工程S2)
工程S2は、評価対象となる鋼種(すなわち、破断ひずみが未導出である鋼種)について、その化学成分により材質パラメータを算出する工程である。具体的には、評価対象種の化学成分の含有量(質量%)を特定したうえで、例えば、上記式(3)〜(5)を用いて評価対象鋼種に係る材質パラメータParamPEwm、ParamPEhaz、ParamPEbmをそれぞれ算出する。また、本発明は、異なる材質の鋼種を接合した溶接金属にも適用することができる。この場合、複数の異なる鋼種を接合したスポット溶接継手における溶接金属の材質パラメータParamPEwmmixは、下記式(9)に示すように溶接金属部におけるそれぞれの鋼種の体積比を材質パラメータに乗じて算出されることが好ましい。尚、評価対象種の化学成分の含有量(質量%)については、評価対象種に係る文献データ又は鋼材の材質情報を記載したミルシートのデータ等から特定することができる。
ParamPEwmmix=ParamPWwm×(V/Vmix)+ParamPWwm×(V/Vmix)…(9)
(式(9)において、ParamPWwm:鋼種aの材質パラメータ、V:溶接金属部における鋼種aの体積、ParamPWwm:鋼種bの材質パラメータ、V:溶接金属部における鋼種bの体積、Vmix:溶接金属部の全体の体積である。)
2.2. Material parameter calculation step (step S2)
Step S2 is a step of calculating a material parameter based on the chemical composition of a steel type to be evaluated (that is, a steel type for which fracture strain has not been derived). Specifically, after specifying the content (mass%) of the chemical component of the evaluation target species, for example, the material parameters ParamPEwm, ParamPEhaz, ParamPEbm according to the evaluation target steel type using the above formulas (3) to (5). Are calculated respectively. Moreover, this invention is applicable also to the weld metal which joined the steel type of a different material. In this case, the material parameter ParamPEwm mix of the weld metal in the spot welded joint obtained by joining a plurality of different steel types is calculated by multiplying the material parameter by the volume ratio of each steel type in the weld metal part as shown in the following formula (9). It is preferable. In addition, about content (mass%) of the chemical component of an evaluation object seed | species, it can identify from the data of the mill sheet | seat etc. which described the literature data concerning the evaluation object seed | species, or the material information of steel materials.
ParamPEwm mix = ParamPWwm a × (V a / V mix) + ParamPWwm b × (V b / V mix) ... (9)
(In Formula (9), ParamPWwm a : Material parameter of steel type a, V a : Volume of steel type a in weld metal part, ParamPWwm b : Material parameter of steel type b, V b : Volume of steel type b in weld metal part, V mix : The total volume of the weld metal part.)

2.3.破断ひずみ算出工程S3(工程S3)
工程S3は、工程S1により決定された近似マスターカーブと、工程S2により算出された評価対象となる鋼種の材質パラメータとを用いて、当該評価対象となる鋼種の破断ひずみを算出する工程である。具体的には、例えば、工程S2により算出された材質パラメータParamPEwm、ParamPEhaz、ParamPEbmの値を、上記式(6)〜(8)にそれぞれ代入することにより、破断ひずみCrPEwm、CrPEhaz、CrPEbmを算出することができる。算出された破断ひずみは、それぞれ、溶接金属部分における破断ひずみの予測値、HAZ部分における破断ひずみの予測値、母材部分における破断ひずみの予測値とすることができる。
2.3. Breaking strain calculation step S3 (step S3)
Step S3 is a step of calculating the fracture strain of the steel type to be evaluated using the approximate master curve determined in step S1 and the material parameter of the steel type to be evaluated calculated in step S2. Specifically, for example, the fracture strains CrPEwm, CrPEhaz, and CrPEbm are calculated by substituting the values of the material parameters ParamPEwm, ParamPEhaz, and ParamPEbm calculated in step S2 into the above formulas (6) to (8), respectively. be able to. The calculated fracture strain can be a predicted value of fracture strain in the weld metal portion, a predicted value of fracture strain in the HAZ portion, and a predicted value of fracture strain in the base material portion, respectively.

以上のように、予測方法S10においては、工程S1〜工程S3を経ることにより、破断ひずみが未導出である鋼種における溶接部について、破断ひずみを精度良く予測することが可能となる。   As described above, in the prediction method S10, the fracture strain can be accurately predicted for the welded portion in the steel type from which the fracture strain has not been derived by performing steps S1 to S3.

図5に、スポット溶接継手引張試験条件のFEM解析における、本発明の予測方法の適用例を示す。ここでは、比較のため従来例も併せて示した。(a)は評価対象のスポット溶接継手である。(b)に示す従来技術は、評価対象の継手と同条件で溶接したスポット溶接部から採取した超小型試験片の引張試験とそれを模擬したFEM解析により破断ひずみを導出する。引張試験では、スポット溶接作業と超小型試験片の加工作業が必要となり、FEM解析では、解析メッシュと材料特性データの作成、境界条件の設定等の一連の解析作業が必要となる。また、1つの鋼種に対して、通常、溶接金属部分、HAZ部分、母材部分の3部位を対象にした引張試験とFEM解析を実施するため、作業時間と人的労力を要することとなる。一方、(c)に示すように本発明の予測方法を用いれば、材料パラメータの算出と近似マスターカーブによる破断ひずみの算出という机上作業のみで、精度よく破断ひずみを予測することができる。また、材料の化学成分に基づいた予測方法であるため、材料の強化機構や化学成分のマイナーチェンジにも臨機応変に対応することができ、高精度に破断ひずみを予測できる。(d)はスポット溶接継手引張試験条件のFEM解析に係るメッシュデータであり、z軸方向に対して1/2対称形でモデル化をしている。(e)はスポット溶接部分周辺の拡大図である。材料特性データと破断ひずみは、溶接金属部分11、HAZ部分12、母材部分13にそれぞれ設定する。   FIG. 5 shows an application example of the prediction method of the present invention in FEM analysis of spot weld joint tensile test conditions. Here, a conventional example is also shown for comparison. (A) is a spot welded joint to be evaluated. In the prior art shown in (b), fracture strain is derived by a tensile test of a micro test piece taken from a spot welded portion welded under the same conditions as a joint to be evaluated and FEM analysis simulating it. In the tensile test, a spot welding work and a micro work piece processing work are required, and in the FEM analysis, a series of analysis work such as creation of analysis mesh and material property data, setting of boundary conditions, and the like are required. In addition, since a tensile test and FEM analysis are usually performed on one steel type for three parts, that is, a weld metal part, a HAZ part, and a base material part, work time and human labor are required. On the other hand, if the prediction method of the present invention is used as shown in (c), the fracture strain can be accurately predicted only by the desk work of calculating the material parameter and calculating the fracture strain by the approximate master curve. In addition, since the prediction method is based on the chemical composition of the material, it is possible to cope with minor changes in the material strengthening mechanism and chemical composition, and the fracture strain can be predicted with high accuracy. (D) is mesh data related to the FEM analysis of the spot weld joint tensile test condition, and is modeled in a ½ symmetry with respect to the z-axis direction. (E) is an enlarged view around a spot welded portion. The material characteristic data and the fracture strain are set in the weld metal portion 11, the HAZ portion 12, and the base material portion 13, respectively.

図6に、実際に本発明に係る予測方法を適用した試験結果として、スポット溶接継手引張試験条件のFEM解析における、本発明の予測方法を適用した解析結果の例を示す。図6(f)は図5(d)のメッシュデータを用いたFEM解析の結果である。図6(g)、(h)、(i)、(j)は破断過程を示した解析結果で、溶接部近傍要素の相当塑性ひずみが破断ひずみに到達して、その要素を削除した状態である。本例では市販汎用ソルバAbaqusのDamage機能を適用して破断した要素を削除して剛性低下を模擬しているが、同等の機能を持つ他のソルバを用いても良い。(g)は変位4.5mm、(h)は変位6mm、(i)は変位7.5mm、(j)は変位9mmにおける解析結果で、破断起点と最大荷重時の変形形態を確認することができる。図6(k)は試験結果とFEM解析結果で、荷重の履歴を比較している。FEM解析結果は破断なしの従来手法と本発明による破断考慮手法でも比較している。この結果から明らかなように、破断なしの従来手法は最大荷重を試験結果より大きく見積ってしまうが、本発明による破断考慮手法は最大荷重が試験結果と一致している。よって本発明に係る予測方法は、破断の起点となる部位と破断経路を適切に検討し、破断による荷重低下を低減するための板組み、溶接部分の大きさ、溶接位置等の検討に活用することができる。   FIG. 6 shows an example of an analysis result obtained by applying the prediction method of the present invention in the FEM analysis under the spot weld joint tensile test condition as a test result of actually applying the prediction method according to the present invention. FIG. 6 (f) shows the result of FEM analysis using the mesh data of FIG. 5 (d). FIGS. 6 (g), (h), (i), and (j) are analysis results showing the fracture process. In the state where the equivalent plastic strain of the element near the weld reaches the fracture strain and the element is deleted. is there. In this example, the damage function is simulated by applying the damage function of the commercially available general-purpose solver Abaqus to delete the fractured element. However, other solvers having equivalent functions may be used. (G) is the displacement 4.5 mm, (h) is the displacement 6 mm, (i) is the displacement 7.5 mm, (j) is the analysis result at the displacement 9 mm. it can. FIG. 6 (k) compares the load history with the test results and the FEM analysis results. The FEM analysis results are also compared between the conventional method without fracture and the fracture consideration method according to the present invention. As is clear from this result, the conventional method without fracture estimates the maximum load larger than the test result, but the fracture consideration method according to the present invention matches the test load with the maximum load. Therefore, the prediction method according to the present invention appropriately examines the site and the fracture path that are the starting point of fracture, and is used to examine the plate assembly, the size of the welded portion, the welding position, etc. for reducing the load drop due to fracture. be able to.

図7、図8に、実際に本発明に係る予測方法を適用した試験結果として、レーザ溶接継手引張試験条件のFEM解析における、本発明の予測方法を適用した解析結果の例を示す。図7(l)はレーザ溶接継手引張試験条件のFEM解析に係るメッシュデータであり、z軸方向に対して1/2対称形でモデル化をしている。図7(m)はレーザ溶接部分周辺の拡大図である。図5(c)で示す方法で求めた破断ひずみと材料特性データは、溶接金属14、HAZ15、母材16にそれぞれ設定する。   7 and 8 show examples of analysis results obtained by applying the prediction method of the present invention in FEM analysis of laser weld joint tensile test conditions as test results of actually applying the prediction method according to the present invention. FIG. 7 (l) is mesh data related to FEM analysis under the laser weld joint tensile test condition, and is modeled in a ½ symmetry with respect to the z-axis direction. FIG. 7 (m) is an enlarged view around the laser welding portion. The fracture strain and material property data obtained by the method shown in FIG. 5C are set for the weld metal 14, the HAZ 15, and the base material 16, respectively.

図8(n)は、図7のメッシュデータを用いたFEM解析の結果である。図8(o)、(p)、(q)、(r)は破断過程を示した解析結果で、溶接部近傍要素の相当塑性ひずみが破断ひずみに到達して、その要素を削除した状態である。(o)は変位13mm、(p)は変位14mm、(q)は変位15mm、(r)は変位17mmにおける解析結果で、破断起点と最大荷重時の変形形態を確認することができる。図8(s)は試験結果とFEM解析結果で、荷重の履歴を比較している。FEM解析結果は破断なしの従来手法と本発明による破断考慮手法でも比較している。破断なしの従来手法は最大荷重を試験結果より大きく見積ってしまうが、本発明による破断考慮手法は最大荷重が試験結果と一致している。これらにより、本発明をレーザ溶接部の解析に適用した場合においても、破断の起点となる部位と破断経路を適切に検討し、破断による荷重低下を低減するための板組み、溶接金属位置と幅の検討等に活用することができる。   FIG. 8 (n) shows the result of FEM analysis using the mesh data of FIG. FIGS. 8 (o), (p), (q), and (r) are analysis results showing the fracture process. In the state where the equivalent plastic strain of the element in the vicinity of the weld reaches the fracture strain and the element is deleted. is there. (O) is the displacement 13 mm, (p) is the displacement 14 mm, (q) is the displacement 15 mm, (r) is the analysis result at the displacement 17 mm, and it is possible to confirm the fracture starting point and the deformation mode at the maximum load. FIG. 8 (s) shows the test results and the FEM analysis results, comparing the load histories. The FEM analysis results are also compared between the conventional method without fracture and the fracture consideration method according to the present invention. Although the conventional method without fracture estimates the maximum load larger than the test result, the fracture consideration method according to the present invention matches the test load with the maximum load. As a result, even when the present invention is applied to the analysis of laser welds, a plate assembly for reducing the load drop due to fracture, the position and width of the weld metal, by appropriately examining the site and path of fracture It can be used for studying

3.スポット溶接部の破断ひずみの予測システム
第2実施形態に係る本発明の破断ひずみの予測システム10(以下、単に「予測システム10」という。)を図9に示す。図9に示すように、予測システム10は、複数の鋼種の破断ひずみを蓄積したデータベース1と、データベース1から選択された複数の破断ひずみを、化学成分により特定される材質パラメータ毎にまとめ、該破断ひずみの分布から破断ひずみの近似マスターカーブを決定する、マスターカーブ決定手段2と、評価対象となる鋼種の化学成分により、該評価対象となる鋼種の材質パラメータを算出する、材質パラメータ算出手段3と、マスターカーブ決定手段2により決定された近似マスターカーブと、材質パラメータ算出手段3により算出された評価対象となる鋼種の材質パラメータとを用いて、評価対象となる鋼種の破断ひずみを算出する、破断ひずみ算出手段4とを備えている。
3. FIG. 9 shows a fracture strain prediction system 10 (hereinafter simply referred to as “prediction system 10”) according to the second embodiment of the present invention. As shown in FIG. 9, the prediction system 10 summarizes the database 1 in which the fracture strains of a plurality of steel types are accumulated, and the plurality of fracture strains selected from the database 1 for each material parameter specified by the chemical component, The master curve determining means 2 for determining an approximate master curve of the fracture strain from the fracture strain distribution, and the material parameter calculating means 3 for calculating the material parameter of the steel type to be evaluated by the chemical component of the steel type to be evaluated. And using the approximate master curve determined by the master curve determining means 2 and the material parameters of the steel type to be evaluated calculated by the material parameter calculating means 3, the fracture strain of the steel type to be evaluated is calculated. Breaking strain calculating means 4.

データベース1は、複数の鋼種について過去に導出した破断ひずみデータが記録されているものであれば、その形態は特に限定されるものではない。ここで、破断ひずみは鋼種の化学成分毎に整理して記録しておくとよい。   The form of the database 1 is not particularly limited as long as fracture strain data derived in the past for a plurality of steel types is recorded. Here, it is good to arrange and record the breaking strain for each chemical component of the steel type.

マスターカーブ決定手段2は、上記マスターカーブ決定工程S1を実行可能な手段であればよく、表計算ソフトウェア等がインストールされた公知の演算装置を用いることができる。マスターカーブ決定手段2においては、データベース1に記録された破断ひずみのうちの複数が、対応する材質パラメータとともに入力され、表計算ソフトウェアによって破断ひずみと材質パラメータとの関係が近似マスターカーブとして決定される。具体的な計算内容については上記した通りであり、ここでは説明を省略する。   The master curve determining means 2 may be any means capable of executing the master curve determining step S1, and a known arithmetic device in which spreadsheet software or the like is installed can be used. In the master curve determining means 2, a plurality of fracture strains recorded in the database 1 are input together with the corresponding material parameters, and the relationship between the fracture strain and the material parameters is determined as an approximate master curve by spreadsheet software. . The specific calculation contents are as described above, and the description is omitted here.

材質パラメータ算出手段3は、上記材質パラメータ算出工程S2を実行可能な手段であればよく、マスターカーブ決定手段2と同様、公知の演算装置を用いることができる。材質パラメータ算出手段3においては、評価対象の鋼種の化学成分が入力されることで、当該評価対象の鋼種に係る材質パラメータの値が算出される。具体的な計算内容については上記した通りであり、ここでは説明を省略する。   The material parameter calculation means 3 may be any means capable of executing the material parameter calculation step S <b> 2, and a known arithmetic device can be used as in the master curve determination means 2. In the material parameter calculation means 3, the value of the material parameter related to the steel type to be evaluated is calculated by inputting the chemical component of the steel type to be evaluated. The specific calculation contents are as described above, and the description is omitted here.

破断ひずみ算出手段4は、上記破断ひずみ算出工程S3を実行可能な手段であればよく、マスターカーブ決定手段2や材質パラメータ算出手段3と同様、公知の演算装置を用いることができる。破断ひずみ算出手段4においては、算出された材質パラメータ値が、近似マスターカーブに係る関数の材質パラメータ値として代入されることにより、破断ひずみが算出される。具体的な計算内容については上記した通りであり、ここでは説明を省略する。   The breaking strain calculating means 4 may be any means capable of executing the breaking strain calculating step S <b> 3, and a known arithmetic device can be used like the master curve determining means 2 and the material parameter calculating means 3. In the breaking strain calculation means 4, the breaking strain is calculated by substituting the calculated material parameter value as the material parameter value of the function related to the approximate master curve. The specific calculation contents are as described above, and the description is omitted here.

尚、本発明では、マスターカーブ決定手段2、材質パラメータ算出手段3、及び破断ひずみ算出手段4を別個とする必要はなく、すなわち、一の演算装置を当該手段2、3及び4として機能させてもよい。   In the present invention, the master curve determination means 2, the material parameter calculation means 3, and the fracture strain calculation means 4 do not need to be separately provided, that is, one arithmetic device functions as the means 2, 3 and 4. Also good.

以上のように、予測システム10においては、データベース1、マスターカーブ決定手段2、材質パラメータ算出手段3、及び破断ひずみ算出手段4を機能させて上記工程S1〜S3を実行することにより、破断ひずみが未導出である鋼種における溶接部について、破断ひずみを精度良く予測することができる。   As described above, in the prediction system 10, the database 1, the master curve determination unit 2, the material parameter calculation unit 3, and the fracture strain calculation unit 4 function to execute the above-described steps S1 to S3. The fracture strain can be accurately predicted for the welded portion in the steel type that has not been derived.

4.溶接部を備えた部材の製造方法
第3実施形態に係る本発明は、上記第1実施形態に係る本発明の破断ひずみの予測方法により予測された破断ひずみを用いて有限要素法解析を行い、解析結果に基づいて部材の板組み、溶接部の大きさ及び/又は溶接位置を決定し、該決定された板組み、溶接部の大きさ及び/又は溶接位置にしたがって部材を溶接する工程を備える、溶接部を備えた部材の製造方法である。例えば、上記第1実施形態に係る本発明の破断ひずみの予測方法により予測された破断ひずみを用いて有限要素法解析を行い、解析結果に基づいて継手の板組み、溶接ナゲット径の大きさ、及び/又は、打点間隔を決定し、該決定された板組み、溶接ナゲット径の大きさ、及び/又は、打点間隔にしたがって部材をスポット溶接することで、スポット溶接部を備えた継手を製造する形態が挙げられる。当該製造方法によれば、板組み、溶接部の大きさや溶接位置が適切とされた溶接部材を製造することができる。これを、例えば自動車部材等の設計に反映させることで、自動車の衝突変形中における溶接部破断を抑制し、適切にエネルギーを吸収することが可能な自動車構造部材を製造することが可能である。
4). The manufacturing method of the member provided with the welded portion The present invention according to the third embodiment performs a finite element method analysis using the fracture strain predicted by the fracture strain prediction method of the present invention according to the first embodiment, Determining the plate assembly of the member, the size and / or the welding position of the member based on the analysis result, and welding the member according to the determined plate assembly, the size and / or the welding position of the welded portion. A method for producing a member provided with a weld. For example, the finite element method analysis is performed using the fracture strain predicted by the fracture strain prediction method of the present invention according to the first embodiment, the joint plate assembly, the size of the weld nugget diameter based on the analysis result, And / or determining the spot spacing and spot welding the members in accordance with the determined plate assembly, the size of the weld nugget diameter, and / or the spot spacing to produce a joint with a spot weld. A form is mentioned. According to the manufacturing method, it is possible to manufacture a welding member in which the plate assembly, the size of the welded portion, and the welding position are appropriate. By reflecting this in the design of, for example, an automobile member or the like, it is possible to manufacture an automobile structural member that can suppress the fracture of a welded part during collision deformation of the automobile and can appropriately absorb energy.

上記説明においては、主に、本発明がスポット溶接部やレーザ溶接部の解析に適用される形態を例示したが、本発明は当該形態に限定されるものではない。その他溶接手段により溶接された部材を解析する場合においても、本発明を適用することが可能である。また、上記説明においては、本発明が溶接材料として鉄鋼材料を用いた場合に適用される形態を例示したが、本発明は当該形態に限定されるものではない。チタンやアルミニウム等のその他金属材料に係る溶接部材を解析する場合であっても、本発明を適用することができる。   In the above description, the embodiment in which the present invention is mainly applied to the analysis of the spot welded portion and the laser welded portion is exemplified, but the present invention is not limited to the embodiment. The present invention can also be applied when analyzing a member welded by other welding means. Moreover, in the said description, although the form applied when this invention uses steel materials as welding material was illustrated, this invention is not limited to the said form. The present invention can be applied even when analyzing a welding member related to other metal materials such as titanium and aluminum.

以下、実施例により、本発明に係る破断ひずみの予測方法について、より詳しく説明する。   Hereinafter, the method for predicting fracture strain according to the present invention will be described in more detail by way of examples.

マスターカーブ決定工程S1は、上記に説明した通りのものとし、近似マスターカーブとしてMwm、Mhaz、Mbmを得た。   The master curve determination step S1 is as described above, and Mwm, Mhaz, and Mbm are obtained as approximate master curves.

評価対象となる鋼種の材質パラメータの算出にあたり、当該鋼種の化学成分を特定した。具体的には下記の通りである。
C:0.074質量%
Si:0.06質量%
Mn:2.34質量%
P:0.01質量%
S:0.001質量%
Cr:0.03質量%
In calculating the material parameters of the steel type to be evaluated, the chemical composition of the steel type was specified. Specifically, it is as follows.
C: 0.074 mass%
Si: 0.06 mass%
Mn: 2.34% by mass
P: 0.01% by mass
S: 0.001 mass%
Cr: 0.03 mass%

材質パラメータ算出工程S2は、上記特定した評価対象種の化学成分を、上記式(3)〜(5)に代入することにより行った。算出された材質パラメータは、ParamPEwm=0.1007、ParamPEhaz=0.1186、ParamPEbm=0.1463であった。   Material parameter calculation process S2 was performed by substituting the chemical component of the specified evaluation object species into the above formulas (3) to (5). The calculated material parameters were ParamPEwm = 0.007, ParamPEhaz = 0.1186, ParamPEbm = 0.1463.

破断ひずみ算出工程S3は、算出された評価対象となる鋼種の材質パラメータを、上記式(6)〜(8)に代入することにより行った。算出された破断ひずみは、CrPEwm=0.98、CrPEhaz=1.00、CrPEbm=1.07となった。
また、従来の方法により導出された破断ひずみは、CrPEwm=0.94、CrPEhaz=0.95、CrPEbm=1.08となった。
The fracture strain calculation step S3 was performed by substituting the calculated material parameters of the steel type to be evaluated into the above formulas (6) to (8). The calculated breaking strains were CrPEwm = 0.98, CrPEhaz = 1.00, and CrPEbm = 1.07.
Further, the fracture strains derived by the conventional method were CrPEwm = 0.94, CrPEhaz = 0.95, and CrPEbm = 1.08.

なお、ひずみの解析結果は要素サイズの影響を受け、ひずみが集中する部位においては一般的に要素サイズが大きくなる程ひずみは小さくなる。したがって、破断ひずみも要素サイズの影響を受け、上記の破断ひずみは一辺が0.05mmの六面体要素を対象にしたものである。   Note that the analysis result of the strain is affected by the element size, and generally in a region where the strain is concentrated, the strain decreases as the element size increases. Therefore, the breaking strain is also affected by the element size, and the above breaking strain is for a hexahedral element having a side of 0.05 mm.

実施例により算出された破断ひずみと、従来の方法(超小型試験片の引張試験とそれを模擬したFEM解析を用いた局所的破断ひずみ導出プロセス)により算出された破断ひずみとを比較したところ、実施例により算出された破断ひずみと従来の方法により算出された破断ひずみとがほぼ一致した。すなわち、本発明によれば、破断ひずみが未導出の鋼種についても、破断ひずみ導出プロセスを省略して、破断ひずみを精度よく予測できることが分かった。   When the fracture strain calculated according to the example was compared with the fracture strain calculated by the conventional method (a tensile test of a micro test piece and a local fracture strain derivation process using FEM analysis simulating it), The breaking strain calculated by the example and the breaking strain calculated by the conventional method almost coincided. That is, according to the present invention, it was found that the breaking strain derivation process can be omitted and the breaking strain can be accurately predicted even for a steel type from which the breaking strain has not been derived.

本発明によれば、溶接部を備えた各種部材のFEM解析時に用いられる溶接部の破断ひずみを、精度良く予測することができる。これにより、FEM解析の際、個別に局所的破断ひずみ導出プロセスを行う必要がなくなり、労力を低減することができる。本発明により予測された破断ひずみは、例えば、スポット溶接継手の板組みや溶接ナゲット径を検討するためのFEM解析の際に用いることができ、さらにその結果を自動車の部材設計に反映させることができる。   ADVANTAGE OF THE INVENTION According to this invention, the fracture | rupture distortion | strain of the welding part used at the time of FEM analysis of the various members provided with the welding part can be estimated with a sufficient precision. As a result, it is not necessary to perform a local fracture strain derivation process individually in the FEM analysis, and labor can be reduced. The fracture strain predicted according to the present invention can be used, for example, in FEM analysis for studying the plate assembly and weld nugget diameter of spot welded joints, and the results can be reflected in the design of automobile components. it can.

Claims (4)

有限要素法解析により溶接部の破断予測を実施する際に用いられる、破断ひずみの予測方法であって、
あらかじめ破断ひずみが算出された複数の鋼種について、該破断ひずみを、該鋼種の化学成分により特定される材質パラメータ毎にまとめ、該破断ひずみの分布から破断ひずみの近似マスターカーブを決定する、マスターカーブ決定工程と、
評価対象となる鋼種の化学成分により、該評価対象となる鋼種の材質パラメータを算出する、材質パラメータ算出工程と、
前記マスターカーブ決定工程により決定された前記近似マスターカーブと前記材質パラメータ算出工程により算出された前記評価対象となる鋼種の材質パラメータとを用いて、該評価対象となる鋼種の破断ひずみを算出する、破断ひずみ算出工程と、
を備える、破断ひずみの予測方法。
A prediction method of fracture strain used when carrying out fracture prediction of a welded part by finite element method analysis,
For a plurality of steel types for which the breaking strain is calculated in advance, the breaking strain is summarized for each material parameter specified by the chemical composition of the steel type, and an approximate master curve of the breaking strain is determined from the distribution of the breaking strain. A decision process;
A material parameter calculating step of calculating a material parameter of the steel type to be evaluated according to a chemical component of the steel type to be evaluated;
Using the approximate master curve determined by the master curve determination step and the material parameter of the steel type to be evaluated calculated by the material parameter calculation step, calculate the fracture strain of the steel type to be evaluated. Breaking strain calculation step;
A method for predicting breaking strain.
前記溶接部が、複数の異なる鋼種を接合した溶接部である場合において、前記破断ひずみの予測に用いられる前記材質パラメータが、溶接部におけるそれぞれの鋼種の体積比と化学成分とにより特定・算出されるものである、請求項1に記載の破断ひずみの予測方法。   When the welded portion is a welded portion obtained by joining a plurality of different steel types, the material parameters used for predicting the fracture strain are specified and calculated by the volume ratio and chemical composition of each steel type in the welded portion. The method for predicting fracture strain according to claim 1, wherein 有限要素法解析により溶接部の破断予測を実施する際に用いられる、破断ひずみの予測システムであって、
複数の鋼種の破断ひずみを蓄積したデータベースと、
前記データベースから選択された複数の前記破断ひずみを、化学成分により特定される材質パラメータ毎にまとめ、該破断ひずみの分布から破断ひずみの近似マスターカーブを決定する、マスターカーブ決定手段と、
評価対象となる鋼種の化学成分により、該評価対象となる鋼種の材質パラメータを算出する、材質パラメータ算出手段と、
前記マスターカーブ決定手段により決定された前記近似マスターカーブと前記材質パラメータ算出手段により算出された前記評価対象となる鋼種の材質パラメータとを用いて、該評価対象となる鋼種の破断ひずみを算出する、破断ひずみ算出手段と、
を備える、破断ひずみの予測システム。
A fracture strain prediction system used when carrying out fracture prediction of welds by finite element method analysis,
A database that accumulates fracture strains of multiple steel types;
A plurality of the breaking strains selected from the database for each material parameter specified by a chemical component, and determining an approximate master curve of the breaking strain from the breaking strain distribution;
A material parameter calculating means for calculating a material parameter of the steel type to be evaluated according to a chemical component of the steel type to be evaluated;
Using the approximate master curve determined by the master curve determining means and the material parameter of the steel type to be evaluated calculated by the material parameter calculating means, the fracture strain of the steel type to be evaluated is calculated. Breaking strain calculation means,
A fracture strain prediction system comprising:
請求項1に記載の破断ひずみの予測方法により予測された破断ひずみを用いて有限要素法解析を行い、解析結果に基づいて部材の板組み、溶接部の大きさ及び/又は溶接位置を決定し、該決定された板組み、溶接部の大きさ及び/又は溶接位置にしたがって部材を溶接する工程を備える、溶接部を備えた部材の製造方法。   A finite element method analysis is performed using the fracture strain predicted by the fracture strain prediction method according to claim 1, and the plate assembly of the member, the size of the weld and / or the welding position are determined based on the analysis result. The manufacturing method of the member provided with the welding part provided with the process of welding a member according to this determined board assembly, the magnitude | size and / or welding position of a welding part.
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