JP2015161598A - Calculation method of fracture limit line of weld part, calculation system and manufacturing method of member having weld part - Google Patents
Calculation method of fracture limit line of weld part, calculation system and manufacturing method of member having weld part Download PDFInfo
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本発明は、有限要素法解析（Finite Element Method解析。以下において「ＦＥＭ解析」ということがある。）を用いた溶接部の破断限界線の算出方法、該算出方法を実施可能な算出システム、及び、溶接部を備えた部材を、上記算出方法を用いて製造する方法に関する。 The present invention relates to a method for calculating a fracture limit line of a weld using a finite element method analysis (Finite Element Method analysis, hereinafter sometimes referred to as “FEM analysis”), a calculation system capable of performing the calculation method, and Further, the present invention relates to a method for manufacturing a member including a welded portion using the above calculation method.
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。また、近年は、片側アクセス、連続溶接が可能なレーザ溶接が注目されており、自動車部材の接合方法として実用化が進んでいる。部材の衝突エネルギー吸収性能の評価に多用されているＦＥＭ解析の解析精度の向上には、これら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溶接条件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. In recent years, laser welding capable of one-sided access and continuous welding has attracted attention, and is being put to practical use as a method for joining automobile members. In order to improve the analysis accuracy of FEM analysis, which is often used for evaluating the impact energy absorption performance of members, it is important to consider the fracture of these welds, and it is possible to examine welding conditions to prevent the occurrence of fracture There is a need for a way to make it. Moreover, it is desirable that these studies can be performed on various types of steel plates having different mechanical characteristics.
非特許文献１や非特許文献２には、平行部が平滑形状の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、溶接熱影響部（Heat Affected Zone。以下において「ＨＡＺ部分」ということがある。）、及び、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（以下において、平滑形状の試験片で導出した破断ひずみを「平滑破断ひずみ」、切欠付き形状の試験片で導出した破断ひずみを「切欠破断ひずみ」ということがある。）を導出する方法が開示されている。また、平滑破断ひずみ及び切欠破断ひずみを累乗関数で近似し破断限界線（応力三軸度をパラメータにした破断ひずみ）を構築する方法も開示されている。かかる技術によれば、破断限界線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、溶接部にかかる負荷モードがそれぞれ異なる複数のスポット溶接継手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 1 and Non-Patent Document 2, a weld metal part of a spot welded part and a heat affected zone (Heat Affected Zone. And a method of individually and quantitatively measuring the stress-strain, tensile strength, elongation at break, and fracture drawing of each base material part, and the stress-strain relationship and the fracture drawing. Local fracture strain of each part by FEM analysis simulating the tensile test of ultra-small test piece (hereinafter referred to as “smooth break strain”, which is derived from a smooth-shaped test piece, and derived from a test piece having a notched shape. A method for deriving the rupture strain that has been obtained is sometimes referred to as “notch rupture strain”. Also disclosed is a method of approximating smooth breaking strain and notch breaking strain by a power function and constructing a breaking limit line (breaking strain with stress triaxiality as a parameter). According to such a technique, FEM analysis is performed using the fracture limit line as a fracture criterion for each part of the spot welded part, and the joint strength and fractured part of a plurality of spot welded joints with different load modes applied to the welded part are accurately determined. It can be predicted.
非特許文献１や非特許文献２に記載の技術では、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、及び、詳細な破断因子の検討が可能である。これらの技術では、溶接手法により破断ひずみが異なる場合があるため、溶接手法毎に平滑形状及び切欠付き形状の超小型試験片の引張試験結果とＦＥＭ解析結果から平滑破断ひずみ及び切欠破断ひずみを求めている。また、平滑破断ひずみ及び切欠破断ひずみを累乗関数で近似し破断限界線を求めている（以下、この処理を「破断限界線導出プロセス」という場合がある。）。しかしながら、破断限界線が未導出である鋼種及び溶接条件からなる継手を対象に破断予測ＦＥＭ解析を行う場合、当該鋼種について、事前に破断限界線導出プロセスが必要となり、破断限界線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。 With the techniques described in Non-Patent Document 1 and Non-Patent Document 2, it is possible to predict the fracture with respect to the tensile test conditions of the spot welded joint and to examine the detailed fracture factor. In these technologies, the fracture strain may vary depending on the welding method. Therefore, the smooth fracture strain and the notch fracture strain are obtained from the tensile test results and FEM analysis results of the smooth and notched micro test pieces for each welding method. ing. In addition, the smooth fracture strain and the notch fracture strain are approximated by a power function to obtain a fracture limit line (hereinafter, this process may be referred to as a “break limit line derivation process”). However, when performing fracture prediction FEM analysis for joints consisting of steel grades and welding conditions for which the fracture limit line has not yet been derived, a fracture limit line derivation process is required in advance for the steel type, and the increase in the fracture limit line derivation process Was a problem requiring work time and human labor.
そこで本発明は、破断限界線が未導出である溶接手法を用いる継手について、破断限界線導出プロセスを行わずに破断限界線を精度良く算出することが可能な、溶接部の破断限界線の算出方法、当該算出方法を実施可能な算出システム、及び、当該算出方法を用いる、溶接部を備えた部材の製造方法を提供することを課題とする。 Accordingly, the present invention provides a calculation of the fracture limit line of a welded portion that can accurately calculate the fracture limit line without performing the fracture limit line derivation process for a joint using a welding technique in which the fracture limit line has not been derived. It is an object of the present invention to provide a method, a calculation system capable of performing the calculation method, and a method for manufacturing a member including a welded portion using the calculation method.
上記課題を解決するために、同一鋼種のスポット溶接部及びレーザ溶接部を対象に、あらかじめ、破断限界線を導出して破断限界線基準データとする。図１に、例として引張強さ５９０ＭＰａ級鋼板の、スポット溶接部及びレーザ溶接部の破断限界線を示す。一般に、破断ひずみは応力三軸度が大きいほど低下し、図１に示すように破断ひずみと応力三軸度は負の相関を示す。そこで、破断限界線は下記式（１）で表される累乗関数で近似ができる。本発明者らが鋭意研究した結果、
（ａ）スポット溶接部破断限界線を式（１）とした場合、レーザ溶接部破断限界線の式（２）は式（３）に置き換えることができること、
（ｂ）式（１）を式（３）に変換するための変換係数ａｔ及びｂｔは、スポット溶接部硬さＨｖ（ｓｐｏｔ）とレーザ溶接部硬さＨｖ（ｌａｓｅｒ）との比ＲＨｖ（＝Ｈｖ（ｌａｓｅｒ）／Ｈｖ（ｓｐｏｔ））に対して図２及び図３に示す関係が成り立つこと、
（ｃ）式（４）及び（５）を用いてＲＨｖから変換係数ａｔ及びｂｔを算出できること、
を知見した。また、スポット溶接部とレーザ溶接部の硬さは、化学成分から炭素当量を用いて近似的に算出することができる。これにより、レーザ溶接部破断限界線が未導出である鋼種であっても、スポット溶接部破断限界線が導出済みで化学成分が判明していれば、これを用いてレーザ溶接部破断限界線を容易に求めることができる。
εｐ ＝ ａｓ・σｔｒｉａｘ＾ｂｓ （１）
εｐ ＝ ａｌ・σｔｒｉａｘ＾ｂｌ （２）
εｐ ＝ ａｓ・ａｔ・σｔｒｉａｘ＾（ｂｓ・ｂｔ） （３）
ａｔ ＝ ｐ１・ＲＨｖ ＋ ｐ２ （４）
ｂｔ ＝ ｐ３・ＲＨｖ ＋ ｐ４ （５）
式（１）〜（５）において、εｐは破断ひずみ、σｔｒｉａｘは応力三軸度（０．８＜σｔｒｉａｘ＜２．０）、ａｓ、ｂｓ、ａｌ、及び、ｂｌは鋼種・部位毎に異なる係数、ａｔ及びｂｔは鋼種・部位毎に異なる変換係数であり、ｐ１、ｐ２、ｐ３、及び、ｐ４はパラメータである。
本発明は、上記知見に基づいてなされたものである。本発明について以下に説明する。
In order to solve the above-mentioned problem, a fracture limit line is derived in advance for the spot welded portion and laser welded portion of the same steel type, and used as the fracture limit line reference data. FIG. 1 shows, as an example, the fracture limit lines of a spot welded portion and a laser welded portion of a steel plate having a tensile strength of 590 MPa. Generally, the breaking strain decreases as the stress triaxiality increases, and the breaking strain and the stress triaxiality have a negative correlation as shown in FIG. Therefore, the fracture limit line can be approximated by a power function represented by the following formula (1). As a result of intensive studies by the inventors,
(A) When the spot weld limit line is defined as equation (1), equation (2) of the laser weld fracture limit line can be replaced with equation (3).
(B) transform coefficients a t and b t for converting formula (1) into equation (3), the ratio RHv spot weld hardness Hv and (spot) and the laser weld hardness Hv (laser) ( = Hv (laser) / Hv (spot)), the relationship shown in FIGS.
(C) Equation (4) and (5) can be calculated transformation coefficients a t and b t from RHv using,
I found out. Moreover, the hardness of a spot welded part and a laser welded part can be calculated approximately using a carbon equivalent from a chemical component. As a result, even if the steel weld breakage limit line has not yet been derived, if the spot weld breakage limit line has already been derived and the chemical composition is known, the laser weld breakage limit line can be determined using this. It can be easily obtained.
ε p = a s · σ triax ^ b s (1)
ε p = a l · σ triax ^ b l (2)
ε p = a s · a t · σ triax ^ (b s · b t ) (3)
a t = p1 · RHv + p2 (4)
b t = p3 · RHv + p4 (5)
In the formula (1) ~ (5), ε p is the strain at break, sigma TRIAX stress three Jikudo (0.8 <σ triax <2.0) , a s, b s, a l, and, b l is different coefficient for each steel type, site, a t and b t are different conversion factor for each steel type, site, p1, p2, p3, and, p4 are parameters.
The present invention has been made based on the above findings. The present invention will be described below.
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、溶接部の破断限界線の算出方法であって、あらかじめ破断限界線導出プロセスによりスポット溶接部の破断限界線及びレーザ溶接部の破断限界線が導出されている金属材料について、下記式（１）で表されるスポット溶接部の破断限界線の構成式、及び、下記式（２）で表されるレーザ溶接部の破断限界線の構成式を準備するとともに、下記式（２）の表現を変更した下記式（３）でレーザ溶接部の破断限界線の構成式を表現する破断限界線構成式準備工程と、下記式（１）で用いられる係数ａｓ及びｂｓと、下記式（２）で用いられる係数ａｌ及びｂｌから、下記式（３）で用いられる変換係数ａｔ及びｂｔを算出する変換係数算出工程と、スポット溶接部硬さ及びレーザ溶接部硬さの比ＲＨｖを算出する第１硬さ比算出工程と、該第１硬さ比算出工程で算出したＲＨｖ及び変換係数ａｔを用いて、下記式（４）で表される変換係数ａｔの算出式におけるパラメータｐ１及びｐ２を算出する第１パラメータ算出工程と、第１硬さ比算出工程で算出したＲＨｖ及び変換係数ｂｔを用いて、下記式（５）で表される変換係数ｂｔの算出式におけるパラメータｐ３及びｐ４を算出する第２パラメータ算出工程と、レーザ溶接部の破断限界線の構成式が未導出である金属材料の化学成分を用いて、該金属材料のスポット溶接部硬さ及びレーザ溶接部硬さの比ＲＨｖを算出する第２硬さ比算出工程と、該第２硬さ比算出工程で算出されたＲＨｖを下記式（４）へと代入することにより、レーザ溶接部の破断限界線の構成式で用いる変換係数ａｔを算出する変換係数ａｔ算出工程と、第２硬さ比算出工程で算出されたＲＨｖを下記式（５）へと代入することにより、レーザ溶接部の破断限界線の構成式で用いる変換係数ｂｔを算出する変換係数ｂｔ算出工程と、あらかじめ破断限界線導出プロセスにより導出されている、下記式（１）で表されるスポット溶接部の破断限界線構成式で用いられる係数ａｓ及びｂｓと、変換係数ａｔ算出工程で算出された変換係数ａｔと、変換係数ｂｔ算出工程で算出された変換係数ｂｔとを、下記式（３）へと代入することにより、レーザ溶接部の破断限界線の構成式を導出するレーザ溶接部破断限界線構成式導出工程と、を有する、溶接部の破断限界線の算出方法である。
εｐ ＝ ａｓ・σｔｒｉａｘ＾ｂｓ （１）
εｐ ＝ ａｌ・σｔｒｉａｘ＾ｂｌ （２）
εｐ ＝ ａｓ・ａｔ・σｔｒｉａｘ＾（ｂｓ・ｂｔ） （３）
ａｔ ＝ ｐ１・ＲＨｖ ＋ ｐ２ （４）
ｂｔ ＝ ｐ３・ＲＨｖ ＋ ｐ４ （５）
上記式（１）〜（５）において、εｐは破断ひずみ、σｔｒｉａｘは応力三軸度（０．８＜σｔｒｉａｘ＜２．０）、ａｓ、ｂｓ、ａｌ、及び、ｂｌは鋼種・部位毎に異なる係数、ａｔ及びｂｔは鋼種・部位毎に異なる変換係数であり、ｐ１、ｐ２、ｐ３、及び、ｐ４はパラメータである。
A first aspect of the present invention is a method for calculating a fracture limit line of a welded part used when predicting fracture of a welded part by a finite element method analysis, wherein a spot welded part is obtained in advance by a fracture limit line derivation process. For the metal material from which the fracture limit line of the laser beam and the fracture limit line of the laser weld are derived, the structural formula of the fracture limit line of the spot welded part represented by the following formula (1) and the formula (2) Rupture limit line configuration expressing the rupture limit line constitutive equation of the laser welded portion by preparing the constitutive equation of the rupture limit line of the laser welded portion and changing the expression of the following formula (2) to the following equation (3) and wherein preparing step, the coefficients a s and b s used in the following formula (1), the coefficients a l and b l is used by the following formula (2), and transform coefficients a t used by the following formula (3) and conversion coefficient calculation step of calculating a b t, With a first hardness ratio calculating step of calculating a ratio RHv pot weld hardness and the laser weld hardness, the RHv and transform coefficients a t calculated by the first hardness ratio calculating step, the following formula ( using a first parameter calculating step of calculating the parameters p1 and p2 in the equation for calculating the transform coefficients a t represented by 4), the RHv and transform coefficients b t calculated by the first hardness ratio calculating step, the following formula A second parameter calculation step of calculating parameters p3 and p4 in the calculation formula of the conversion coefficient b t represented by (5), and chemical components of the metal material from which the constitutive formula of the fracture limit line of the laser weld is not derived. The second hardness ratio calculating step of calculating the ratio RHv of the spot welded portion hardness and the laser welded portion hardness of the metal material, and the RHv calculated in the second hardness ratio calculating step are expressed by the following formula ( Substituting into 4) A conversion coefficient a t calculation step of calculating a conversion coefficient a t used in the construction type of weld fracture limit line, by the RHv calculated by the second hardness ratio calculating step is substituted into the following formula (5) a conversion coefficient b t calculation step of calculating a conversion coefficient b t used in the construction type of fracture limit line of the laser welding portions are derived by pre-fracture limit line derivation process, the spot represented by the following formula (1) and the coefficient a s and b s used in fracture limit line structure type welding unit, a conversion coefficient a t calculated by the conversion factor a t calculation step, a conversion coefficient b t calculated by the conversion coefficient b t calculation step Substituting into the following formula (3) to derive a constitutive equation for the laser welding portion fracture limit line, and a laser welding portion fracture limit line constitutive equation derivation step, Is the method.
ε p = a s · σ triax ^ b s (1)
ε p = a l · σ triax ^ b l (2)
ε p = a s · a t · σ triax ^ (b s · b t ) (3)
a t = p1 · RHv + p2 (4)
b t = p3 · RHv + p4 (5)
In the above formulas (1) to (5), ε p is the breaking strain, σ triax is the stress triaxiality (0.8 <σ triax <2.0), a s , b s , a l , and b l coefficients different for each steel type, site, a t and b t are different conversion factor for each steel type, site, p1, p2, p3, and, p4 are parameters.
ここに、本発明の第１の態様及び以下に示す本発明の他の態様（以下において、これらをまとめて「本発明」ということがある。）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（スポット溶接の場合はナゲット部分、レーザ溶接の場合は溶接ビード部分）、ＨＡＺ部分、母材部分に大別することができる。また、「破断限界線」とは、平滑破断ひずみ及び切欠破断ひずみを累乗関数で近似し導出されたものであり、例えば、溶接部における母材部分の破断限界線、ＨＡＺ部分の破断限界線、溶接金属部分の破断限界線等を挙げることができる。本発明における「破断限界線」は、シーム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。また、本発明において、「化学成分」とは、溶接される金属材料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。 Here, in the first aspect of the present invention and the other aspects of the present invention described below (hereinafter, these may be collectively referred to as “the present invention”), the “welded portion” particularly refers to a steel material. It is preferably a welded portion, and can be roughly divided into a weld metal portion (a nugget portion in the case of spot welding, a weld bead portion in the case of laser welding), a HAZ portion, and a base material portion. Further, the “breaking limit line” is derived by approximating a smooth breaking strain and a notch breaking strain by a power function, for example, a breaking limit line of a base material part in a welded part, a breaking limit line of a HAZ part, Examples include the fracture limit line of the weld metal portion. The “break limit line” in the present invention is a reference value for fracture determination that can also be applied to a welded portion in other welding means such as seam welding. Further, in the present invention, the “chemical component” can include the mass% concentration, molar concentration, volume% concentration, composition ratio, etc. of the component contained in the metal material to be welded.
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、溶接部の破断限界線を算出するシステムであって、上記破断限界線は破断限界線構成式で近似され、入出力部と、金属材料の破断限界線構成式を蓄積したデータベースと、変換係数算出式作成部と、破断限界線変換部とを有し、上記変換係数算出式作成部は、データベースから選択された、スポット溶接部破断限界線構成式の係数及びレーザ溶接部破断限界線構成式の係数を用いて、スポット溶接部破断限界線構成式からレーザ溶接部破断限界線構成式を導出する際に用いられる変換係数を算出する第１変換係数算出部と、スポット溶接部硬さとレーザ溶接部硬さとの比ＲＨｖを算出する第１硬さ比算出部と、算出されたＲＨｖ及び変換係数を用いて、ＲＨｖと変換係数との関係式で用いられるパラメータを算出するパラメータ算出部と、を有し、上記破断限界線変換部は、レーザ溶接部の破断限界線構成式が未導出である金属材料の化学成分を用いて、該金属材料のスポット溶接部硬さとレーザ溶接部硬さとの比ＲＨｖを算出する第２硬さ比算出部と、該第２硬さ比算出部で算出されたＲＨｖを、ＲＨｖと変換係数との上記関係式へと代入することにより、レーザ溶接部の破断限界線構成式で用いられる変換係数を算出する第２変換係数算出部と、あらかじめ破断限界線導出プロセスにより導出されているスポット溶接部の破断限界線構成式で用いられる係数と、上記第２変換係数算出部で算出された変換係数とを用いるレーザ溶接部の破断限界線構成式を導出するレーザ溶接部破断限界線構成式導出部と、を有する、溶接部の破断限界線の算出システムである。 A second aspect of the present invention is a system for calculating a fracture limit line of a welded part, which is used when performing fracture prediction of a welded part by a finite element method analysis, wherein the fracture limit line has a fracture limit line configuration. It is approximated by an equation, and has an input / output unit, a database that accumulates fracture limit line constitutive formulas of metal materials, a conversion coefficient calculation formula creation unit, and a fracture limit line conversion unit, and the conversion coefficient calculation formula creation unit is Using the coefficient of the spot weld fracture limit line constitutive formula and the coefficient of the laser weld fracture limit line constitutive formula selected from the database, the laser weld fracture limit line constitutive formula is converted from the spot weld fracture limit line constitutive formula. A first conversion coefficient calculation unit that calculates a conversion coefficient used when deriving, a first hardness ratio calculation unit that calculates a ratio RHv between spot welded portion hardness and laser welded portion hardness, and calculated RHv and conversion Use coefficient A parameter calculation unit that calculates a parameter used in a relational expression between RHv and a conversion coefficient, and the fracture limit line conversion unit is formed of a metal material for which a fracture limit line constitutive equation of a laser weld is not derived. Using the chemical component, the second hardness ratio calculation unit for calculating the ratio RHv of the spot weld hardness and the laser weld hardness of the metal material, and the RHv calculated by the second hardness ratio calculation unit, By substituting RHv and the conversion coefficient into the above relational expression, the second conversion coefficient calculation unit for calculating the conversion coefficient used in the fracture limit line constitutive equation of the laser welded part and the fracture limit line derivation process in advance are derived. The laser weld breakage limit that derives the break limit line composition of the laser weld using the coefficients used in the break limit line construction of the spot welded part and the conversion coefficient calculated by the second conversion coefficient calculator It has a linear structure type deriving portion, a calculation system of the welded portion of the fracture limit line.
本発明の第３の態様は、上記本発明の第１の態様に係る溶接部の破断限界線の算出方法により算出された破断限界線を用いて有限要素法解析を行い、その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有する、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 a fracture limit line calculated by the method for calculating a fracture limit line of a weld according to the first aspect of the present invention, and based on the analysis result. Determining the plate assembly of the member, the size and / or welding position of the welded portion, and welding the member according to the determined plate assembly, the size of the welded portion and / or the welding position. It is a manufacturing method of the member provided.
本発明においては、破断限界線の変換係数を、溶接対象金属材料の化学成分から計算した硬さを用いて算出する。これにより、破断限界線が未導出であるレーザ溶接部の破断限界線を算出・予測する場合であっても、溶接対象である金属材料の化学成分を特定し、スポット溶接部破断限界線が導出済みであれば変換係数を用いてレーザ溶接部破断限界線を容易に算出・予測することができる。したがって、本発明によれば、破断限界線が未導出である鋼種からなる部材に対しても、破断限界線導出プロセスを行わずに破断限界線を精度良く算出することが可能な、溶接部の破断限界線の算出方法を提供することができる。また、本発明によれば、この算出方法を実施可能な算出システム、及び、当該算出方法を用いる、溶接部を備えた部材の製造方法を提供することができる。 In the present invention, the conversion coefficient of the fracture limit line is calculated using the hardness calculated from the chemical component of the metal material to be welded. As a result, even when calculating and predicting the fracture limit line of a laser weld that has not yet been broken, the chemical composition of the metal material to be welded is identified, and the spot weld break line is derived. If completed, the laser weld fracture limit line can be easily calculated and predicted using the conversion coefficient. Therefore, according to the present invention, it is possible to accurately calculate the fracture limit line without performing the fracture limit line derivation process even for members made of steel types for which the fracture limit line has not been derived. A method for calculating the fracture limit line can be provided. Moreover, according to this invention, the manufacturing system which can implement this calculation method, and the manufacturing method of the member provided with the welding part which uses the said calculation method can be provided.
１．本発明完成までの経緯
上記非特許文献１及び２によれば、平滑形状及び切欠付き形状の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平滑破断ひずみ及び切欠破断ひずみと定義できる。同様に、破断限界の応力三軸度も定義できる。また、このプロセスを溶接金属部分、ＨＡＺ部分、及び、母材部分毎に行うことで、各部位（溶接金属部分、ＨＡＺ部分、及び、母材部分。以下において同じ。）での平滑破断ひずみ及び切欠破断ひずみと破断限界の応力三軸度を導出することができる。そして、破断ひずみと応力三軸度との関係を累乗関数で近似することにより、各部位の破断限界線を構築することができる。
1. Background to the completion of the present invention According to Non-Patent Documents 1 and 2 above, the cross-sectional area of the test part of the FEM analysis result simulating the tensile test of a smooth test piece and a notched micro test piece is the actual value of the fracture test piece. Can be defined as the local smooth fracture strain and notch fracture strain of the specimen. Similarly, the stress triaxiality at the breaking limit can be defined. In addition, by performing this process for each weld metal part, HAZ part, and base material part, the smooth fracture strain at each part (weld metal part, HAZ part, and base material part; the same applies hereinafter) and The notch breaking strain and the stress triaxiality at the breaking limit can be derived. And the fracture limit line of each part can be constructed by approximating the relation between the fracture strain and the stress triaxiality by a power function.
図１は、スポット溶接部及びレーザ溶接部の破断ひずみと応力三軸度との関係を示す図である。図１に示したように、破断限界線の破断ひずみは、スポット溶接部のものよりもレーザ溶接部のものの方が応力三軸度の影響が小さく、増大傾向を示す。そのため、破断限界線の係数ａ及びｂは、スポット溶接部のものよりもレーザ溶接部のものの方が大きくなると考えられる。また、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。また、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、上記式（４）及び式（５）を用いることで、スポット溶接部破断限界線の構成式（上記式（１））をレーザ溶接部破断限界線の構成式（上記式（３））に変換する変換係数ａｔ及びｂｔを算出できることを知見した。 FIG. 1 is a diagram showing the relationship between fracture strain and stress triaxiality of spot welds and laser welds. As shown in FIG. 1, the fracture strain of the fracture limit line is less affected by the stress triaxiality in the laser welded part than in the spot welded part, and shows an increasing tendency. Therefore, it is considered that the coefficients a and b of the fracture limit line are larger in the laser welded part than in the spot welded part. In addition, 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 welded portion hardness. Thus, in steel materials, it is considered that there is a correlation between chemical components and mechanical properties. Moreover, 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, by using the above formulas (4) and (5), the constitutive formula of the spot welded portion fracture limit line (above formula (1)) is replaced by the constitutive formula of the laser weld zone fracture limit line (above formula (3)). It was found that can calculate the transform coefficients a t and b t are converted to.
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、レーザ溶接部の破断部位（例えば、溶接ビード部分）に係る破断限界線について、式（２）及び（３）を用いることで、スポット溶接部破断限界線の構成式（式（１））から変換するための変換係数ａｔ及びｂｔを算出し、当該鋼種のレーザ溶接部の破断部位に係る破断限界線を適切に導出・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 formula (2) and (3) are used for the fracture limit line relating to the fracture site (for example, the weld bead portion) of the laser welded portion, thereby constructing the constitutive formula of the spot weld zone fracture limit line ( calculating a conversion coefficient a t and b t for converting from the formula (1)), a fracture limit line of the fracture site of laser welds of the steel species can be properly derive and predict.
以下、本発明の実施形態について詳述する。なお、以下の説明では、金属材料が鋼板であり、その溶接金属部分の破断限界線を算出する場合を主に例示するが、本発明は以下に説明する形態に限定されない。 Hereinafter, embodiments of the present invention will be described in detail. In addition, in the following description, although the metal material is a steel plate and the case where the fracture limit line of the weld metal part is calculated is mainly illustrated, the present invention is not limited to the form described below.
２．溶接部の破断限界線の算出方法
本発明の第１実施形態に係る溶接部の破断限界線の算出方法Ｓ１０（以下において、単に「算出方法Ｓ１０」という。）を図４に示す。図４に示すように、算出方法Ｓ１０は、破断限界線構成式準備工程Ｓ１と、変換係数算出工程Ｓ２と、第１硬さ比算出工程Ｓ３と、第１パラメータ算出工程Ｓ４と、第２パラメータ算出工程Ｓ５と、第２硬さ比算出工程Ｓ６と、変換係数ａｔ算出工程Ｓ７と、変換係数ｂｔ算出工程Ｓ８と、レーザ溶接部破断限界線構成式導出工程Ｓ９と、を有している。以下の説明では、破断限界線導出プロセスによってスポット溶接部の破断限界線構成式が既知である鋼種として母材強度クラス５９０ＭＰａ級鋼板を用い、レーザ溶接部の破断限界線構成式を決定した例を示す。
2. Calculation Method of Fracture Limit Line of Welded Portion A fracture limit line calculation method S10 (hereinafter simply referred to as “calculation method S10”) according to the first embodiment of the present invention is shown in FIG. As shown in FIG. 4, the calculation method S10 includes a fracture limit line constitutive equation preparation step S1, a conversion coefficient calculation step S2, a first hardness ratio calculation step S3, a first parameter calculation step S4, and a second parameter. a calculation step S5, the second hardness ratio calculating step S6, the conversion coefficient a t calculation step S7, the conversion coefficient b t calculating step S8, has a laser weld fracture limit line structure formula deriving step S9, the Yes. In the following explanation, an example in which the base metal strength class 590 MPa class steel plate is used as the steel type for which the fracture limit line constitutive equation of the spot weld is known by the fracture limit derivation process and the fracture limit line constitutive equation of the laser weld is determined. Show.
２．１．破断限界線構成式準備工程Ｓ１
破断限界線構成式準備工程Ｓ１は、あらかじめ破断限界線導出プロセスによりスポット溶接部の破断限界線及びレーザ溶接部の破断限界線が導出されている鋼種について、上記式（１）で表されるスポット溶接部の破断限界線の構成式、及び、上記式（２）で表されるレーザ溶接部の破断限界線の構成式を準備するとともに、上記式（２）の表現を変更した上記式（３）でレーザ溶接部の破断限界線の構成式を表現する工程である。
2.1. Break limit line constitutive equation preparation step S1
The fracture limit line constitutive equation preparation step S1 is a spot represented by the above formula (1) for a steel type in which the fracture limit line of a spot weld and the fracture limit line of a laser weld are derived in advance by a fracture limit line derivation process. The above formula (3) is prepared by preparing the constitutive equation of the fracture limit line of the welded portion and the constitutive formula of the fracture limit line of the laser welded portion represented by the above formula (2) and changing the expression of the above formula (2). ) To express the constitutive equation of the fracture limit line of the laser weld.
２．２．変換係数算出工程Ｓ２
変換係数算出工程Ｓ２は、上記工程Ｓ１で準備した上記式（１）で用いられている係数ａｓ及びｂｓと、上記式（２）で用いられている係数ａｌ及びｂｌから、上記式（３）で用いられる変換係数ａｔ及びｂｔを算出する工程である。
2.2. Conversion coefficient calculation step S2
The conversion coefficient calculation step S2 uses the coefficients a s and b s used in the equation (1) prepared in the step S1 and the coefficients a l and b l used in the equation (2). This is a step of calculating conversion coefficients a t and b t used in equation (3).
２．３．第１硬さ比算出工程Ｓ３
第１硬さ比算出工程Ｓ３は、スポット溶接部硬さＨｖ（ｓｐｏｔ）とレーザ溶接部硬さＨｖ（ｌａｓｅｒ）との比ＲＨｖ（＝Ｈｖ（ｌａｓｅｒ）／Ｈｖ（ｓｐｏｔ））を算出する工程である。ＲＨｖは、スポット溶接部硬さＨｖ（ｓｐｏｔ）及びレーザ溶接部硬さＨｖ（ｌａｓｅｒ）の測定結果から算出することができる。このほか、スポット溶接部硬さＨｖ（ｓｐｏｔ）及びレーザ溶接部硬さＨｖ（ｌａｓｅｒ）は、直接測定する以外にも鋼種の化学成分から炭素当量を用いて近似的に求める方法もある。以下にその一例を示す。
鋼種の化学成分から炭素当量の式を用いて、スポット溶接部の硬さ及びレーザ溶接部の硬さをそれぞれ計算する。スポット溶接部硬さの炭素当量の構成式は、例えば式（６）で表すことができ、レーザ溶接部硬さの炭素当量の構成式は、例えば式（７）で表すことができる。なお、式（６）は「及川初彦、他４名、「自動車用高強度鋼板のスポット溶接性」、新日鐵技法、第３８５号、（２００６）、ｐ．３６−４１」に記載されており、式（７）は「N.J. den Uijl et al.、Welding in the World、Vol.52、Issue11-12、(2008)、p.18-29」に記載されている。
Ｃｅｑ（ｓｐｏｔ）＝Ｃ＋Ｓｉ／９０＋（Ｍｎ＋Ｃｒ）／１００＋１．５Ｐ＋３Ｓ（６）
Ｃｅｑ（ｌａｓｅｒ）＝Ｃ＋Ｓｉ／７７＋Ｍｎ／２１＋Ｃｒ／２８＋Ｍｏ／３０ （７）
2.3. First hardness ratio calculation step S3
The first hardness ratio calculating step S3 is a step of calculating a ratio RHv (= Hv (laser) / Hv (spot)) between the spot welded portion hardness Hv (spot) and the laser welded portion hardness Hv (laser). is there. RHv can be calculated from the measurement results of spot weld hardness Hv (spot) and laser weld hardness Hv (laser). Besides, the spot welded portion hardness Hv (spot) and the laser welded portion hardness Hv (laser) can be obtained approximately by using carbon equivalents from the chemical components of the steel type, in addition to direct measurement. An example is shown below.
The hardness of the spot welded part and the hardness of the laser welded part are calculated from the chemical composition of the steel type using the carbon equivalent formula. The carbon equivalent constitutive formula of the spot weld hardness can be expressed by, for example, formula (6), and the carbon equivalent constitutive formula of the laser weld hardness can be expressed by, for example, formula (7). Formula (6) is “Hatsuhiko Oikawa, 4 others,“ Spot weldability of high strength steel sheets for automobiles ”, Nippon Steel Technology, No. 385, (2006), p. 36-41 ”, and Equation (7) is described in“ NJ den Uijl et al., Welding in the World, Vol. 52, Issue 11-12, (2008), p. 18-29 ”. Yes.
Ceq (spot) = C + Si / 90 + (Mn + Cr) /100+1.5P+3S (6)
Ceq (laser) = C + Si / 77 + Mn / 21 + Cr / 28 + Mo / 30 (7)
図５は２７０ＭＰａ級〜９８０ＭＰａ級鋼板を対象にした溶接部硬さと炭素当量の分布を示した図である。本例では、スポット溶接部は式（８）、レーザ溶接部は式（９）で示す曲線関数で近似が可能である。そこで、式（８）及び式（９）を用いて炭素当量からスポット溶接部硬さＨｖ（ｓｐｏｔ）及びレーザ溶接部硬さＨｖ（ｌａｓｅｒ）をそれぞれ求め、ＲＨｖ（＝Ｈｖ（ｌａｓｅｒ）／Ｈｖ（ｓｐｏｔ））を計算することができる。式（８）及び式（９）において、ｈ１、ｈ２、ｈ３、及び、ｈ４はパラメータである。
Ｈｖ（ｓｐｏｔ）＝ｌｏｇｅ（Ｃｅｑ（ｓｐｏｔ）／ｈ１）／ｈ２ （８）
Ｈｖ（ｌａｓｅｒ）＝（Ｃｅｑ（ｌａｓｅｒ）＋ｈ３）／ｈ４ （９）
FIG. 5 is a diagram showing the distribution of weld hardness and carbon equivalent for 270 MPa class to 980 MPa class steel sheets. In this example, the spot welded portion can be approximated by a curve function represented by equation (8), and the laser welded portion can be approximated by a curve function represented by equation (9). Therefore, using Equation (8) and Equation (9), the spot weld hardness Hv (spot) and the laser weld hardness Hv (laser) are obtained from the carbon equivalent, respectively, and RHv (= Hv (laser) / Hv ( spot)) can be calculated. In Formula (8) and Formula (9), h1, h2, h3, and h4 are parameters.
Hv (spot) = log e (Ceq (spot) / h1) / h2 (8)
Hv (laser) = (Ceq (laser) + h3) / h4 (9)
２．４．第１パラメータ算出工程Ｓ４
第１パラメータ算出工程Ｓ４は、上記工程Ｓ３で算出したＲＨｖ、及び、上記工程Ｓ２で算出した変換係数ａｔを用いて、上記式（４）で表される変換係数ａｔの算出式におけるパラメータｐ１及びｐ２を算出する工程である。変換係数ａｔとＲＨｖとの間には図２に示す関係が成り立つので、図２に記載した直線から、パラメータｐ１及びｐ２を算出することができる。
2.4. First parameter calculation step S4
The first parameter calculation step S4 are, RHV calculated at step S3, and, using a conversion coefficient a t calculated at step S2, parameters in equation for calculating transform coefficients a t represented by the above formula (4) This is a step of calculating p1 and p2. Since between the transform coefficients a t and RHv established relationship shown in FIG. 2, the straight line described in FIG. 2, it is possible to calculate the parameters p1 and p2.
２．５．第２パラメータ算出工程Ｓ５
第２パラメータ算出工程Ｓ５は、上記工程Ｓ３で算出したＲＨｖ、及び、上記工程Ｓ２で算出した変換係数ｂｔを用いて、上記式（５）で表される変換係数ｂｔの算出式におけるパラメータｐ３及びｐ４を算出する工程である。変換係数ｂｔとＲＨｖとの間には図３に示す関係が成り立つので、図３に記載した直線から、パラメータｐ３及びｐ４を算出することができる。
2.5. Second parameter calculation step S5
The second parameter calculation step S5 uses the RHv calculated in the step S3 and the conversion coefficient b t calculated in the step S2, and the parameters in the calculation formula of the conversion coefficient b t expressed by the above formula (5) This is a step of calculating p3 and p4. Since the relationship shown in FIG. 3 is established between the conversion coefficient b t and RHv, the parameters p3 and p4 can be calculated from the straight line shown in FIG.
２．６．第２硬さ比算出工程Ｓ６
第２硬さ比算出工程Ｓ６は、レーザ溶接部の破断限界線の構成式が未導出である鋼種の化学成分を用いて、該鋼種の、スポット溶接部硬さＨｖ（ｓｐｏｔ）とレーザ溶接部硬さＨｖ（ｌａｓｅｒ）との比ＲＨｖ（＝Ｈｖ（ｌａｓｅｒ）／Ｈｖ（ｓｐｏｔ））を算出する工程である。工程Ｓ６では、例えば、鋼種の化学成分（Ｃ、Ｓｉ、Ｍｎ、Ｐ、Ｓ、Ｃｒ、Ｍｏ）から、上記式（６）及び式（７）を用いてスポット溶接部の炭素当量Ｃｅｑ（ｓｐｏｔ）及びレーザ溶接部の炭素当量Ｃｅｑ（ｌａｓｅｒ）を求める。次に、上記式（８）及び式（９）を用いてスポット溶接部硬さＨｖ（ｓｐｏｔ）及びレーザ溶接部硬さＨｖ（ｌａｓｅｒ）をそれぞれ求めることにより、ＲＨｖ（＝Ｈｖ（ｌａｓｅｒ）／Ｈｖ（ｓｐｏｔ））を算出することができる。
2.6. Second hardness ratio calculation step S6
The second hardness ratio calculation step S6 uses the chemical composition of the steel type from which the constitutive equation of the fracture limit line of the laser welded part has not been derived, and the spot welded part hardness Hv (spot) of the steel type and the laser welded part. This is a step of calculating a ratio RHv (= Hv (laser) / Hv (spot)) with the hardness Hv (laser). In step S6, for example, from the chemical components (C, Si, Mn, P, S, Cr, Mo) of the steel type, the carbon equivalent Ceq (spot) of the spot welded part using the above formula (6) and formula (7). And the carbon equivalent Ceq (laser) of the laser weld is determined. Next, the spot welded portion hardness Hv (spot) and the laser welded portion hardness Hv (laser) are obtained using the above formulas (8) and (9), respectively, so that RHv (= Hv (laser) / Hv (Spot)) can be calculated.
２．７．変換係数ａｔ算出工程Ｓ７
変換係数ａｔ算出工程Ｓ７は、上記工程Ｓ６で算出されたＲＨｖを上記式（４）へと代入することにより、レーザ溶接部の破断限界線の構成式で用いる変換係数ａｔを算出する工程である。
2.7. Transform coefficients a t calculation step S7
Transform coefficients a t calculation step S7, by substituting the RHv calculated in the step S6 and the above formula (4), a step of calculating a conversion coefficient a t used in the construction type of fracture limit line of the laser welding unit It is.
２．８．変換係数ｂｔ算出工程Ｓ８
変換係数ｂｔ算出工程Ｓ８は、上記工程Ｓ６で算出されたＲＨｖを上記式（５）へと代入することにより、レーザ溶接部の破断限界線の構成式で用いる変換係数ｂｔを算出する工程である。
2.8. Conversion coefficient b t calculation step S8
The conversion coefficient b t calculation step S8 is a step of calculating the conversion coefficient b t used in the constitutive equation of the fracture limit line of the laser weld by substituting the RHv calculated in the above step S6 into the above equation (5). It is.
２．９．レーザ溶接部破断限界線構成式導出工程Ｓ９
レーザ溶接部破断限界線構成式導出工程Ｓ９は、あらかじめ破断限界線導出プロセスにより導出されている、上記式（１）で表されるスポット溶接部の破断限界線構成式で用いられる係数ａｓ及びｂｓと、上記工程Ｓ７で算出された変換係数ａｔと、上記工程Ｓ８で算出された変換係数ｂｔとを、上記式（３）へと代入することにより、破断限界線構成式が導出されていなかった鋼種の、レーザ溶接部の破断限界線構成式を導出する工程である。
2.9. Laser weld fracture limit line constitutive equation derivation step S9
The laser weld fracture limit line constitutive equation derivation step S9 is performed in advance by the fracture limit line derivation process, and the coefficient a s used in the fracture limit line constitutive equation of the spot weld portion expressed by the above formula (1) and and b s, a conversion coefficient a t calculated in the step S7, and a conversion coefficient b t calculated in the step S8, by substituting into the equation (3), deriving the fracture limit line structure formula This is a step of deriving the fracture limit line constitutive equation of the laser weld of the steel type that has not been performed.
以上説明したように、上記工程Ｓ１〜工程Ｓ９を有する本発明に係る溶接部の破断限界線の算出方法では、破断限界線構成式で用いられる変換係数ａｔ及びｂｔを、溶接対象鋼種の化学成分から計算した硬さを用いて算出する。これにより、破断限界線が未導出であるレーザ溶接部の破断限界線を算出・予測する場合であっても、溶接対象である鋼種の化学成分を特定することにより硬さを算出して変換係数ａｔ及びｂｔを特定し、特定した変換係数ａｔ及びｂｔと、既知のスポット溶接部破断限界線における係数ａｓ及びｂｓとを用いて、レーザ溶接部の破断限界線を容易に算出・予測することができる。本発明によれば、レーザ溶接部の破断限界線が未導出である鋼種からなる部材に対しても、破断限界線導出プロセスを行わずにレーザ溶接部破断限界線を精度良く算出することが可能である。 As described above, in the above step S1~ step S9 calculation method fracture limit line of the weld according to the present invention having the transform coefficients a t and b t is used in fracture limit line configuration type, the welded steel species Calculated using hardness calculated from chemical components. As a result, even when calculating and predicting the fracture limit line of a laser weld where the fracture limit line has not been derived, the hardness is calculated by specifying the chemical composition of the steel type to be welded, and the conversion coefficient identify a t and b t, and identified transform coefficients a t and b t, by using the coefficients a s and b s in the known spot weld fracture limit line, easily fracture limit line of the laser welding unit It can be calculated and predicted. According to the present invention, it is possible to calculate the laser weld fracture limit line with high accuracy without performing the fracture limit line derivation process even for members made of steel types for which the fracture limit line of the laser weld has not been derived. It is.
３．溶接部の破断限界線の算出システム
本発明の第２実施形態に係る破断ひずみの算出システム１０（以下、単に「算出システム１０」という。）を図６に示す。図６に示すように、算出システム１０は、スポット溶接部破断限界線及びレーザ溶接部破断限界線を蓄積したデータベース１と、変換係数算出式作成部２と、破断限界線変換部３と、入出力部４と、を備えている。
3. Calculation System for Fracture Limit Line of Welded Section FIG. 6 shows a fracture strain calculation system 10 (hereinafter simply referred to as “calculation system 10”) according to the second embodiment of the present invention. As shown in FIG. 6, the calculation system 10 includes a database 1 in which spot weld boundary fracture limit lines and laser weld fracture limit lines are accumulated, a conversion coefficient calculation formula creation unit 2, a fracture limit line conversion unit 3, And an output unit 4.
データベース１には、ある鋼種について過去に導出したスポット溶接部破断限界線及びレーザ溶接部破断限界線のデータが蓄積されている。算出システム１０において、データベース１の形態は特に限定されない。 The database 1 stores data on spot weld fracture limit lines and laser weld fracture limit lines derived in the past for a certain steel type. In the calculation system 10, the form of the database 1 is not particularly limited.
変換係数算出式作成部２は、データベース１から選択されたスポット溶接部破断限界線の構成式の係数ａｓ及びｂｓとレーザ溶接部破断限界線の構成式の係数ａｌ及びｂｌから変換係数ａｔ及びｂｔを算出し、次に、スポット溶接部硬さとレーザ溶接部硬さとの比ＲＨｖを算出し、変換係数ａｔ及びｂｔとＲＨｖから上記式（４）及び式（５）のパラメータｐ１〜ｐ４を算出する部位である。すなわち、算出システム１０における変換係数算出式作成部２は、第１変換係数算出部、第１硬さ比算出部、及び、パラメータ算出部として機能する。ここで、第１変換係数算出部は、上記工程Ｓ２を実施可能な部位であり、データベース１から選択されたスポット溶接部破断限界線の構成式の係数ａｓ及びｂｓとレーザ溶接部破断限界線の構成式の係数ａｌ及びｂｌから変換係数ａｔ及びｂｔを算出する部位である。また、第１硬さ比算出部は、上記工程Ｓ３を実施可能な部位であり、スポット溶接部硬さとレーザ溶接部硬さとの比ＲＨｖを算出する部位である。また、パラメータ算出部は、上記工程Ｓ４及び工程Ｓ５を実施可能な部位であり、算出したＲＨｖ及び変換係数ａｔを用いて、上記式（４）で表される変換係数ａｔの算出式におけるパラメータｐ１及びｐ２を算出し、算出したＲＨｖ及び変換係数ｂｔを用いて、上記式（５）で表される変換係数ｂｔの算出式におけるパラメータｐ３及びｐ４を算出する部位である。
変換係数算出式作成部２は、上記工程Ｓ１〜工程Ｓ５を実行可能な手段であればよく、例えば、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適宜用いることができる。変換係数算出式作成部２では、データベース１に記録された破断限界線の構成式の各係数が、対応する溶接手法（スポット溶接及びレーザ溶接）の溶接金属部硬さとともに入力され、表計算ソフトウェアによって、破断限界線構成式の変換係数ａｔ及びｂｔの算出式である上記式（４）及び式（５）が決定される。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 conversion coefficient calculation formula creation unit 2 converts from the coefficients a s and b s of the constitutive formula of the spot weld fracture limit line selected from the database 1 and the coefficients a l and b l of the constitutive formula of the laser weld fracture limit line. calculating the coefficients a t and b t, then calculates the ratio RHV the spot weld hardness and the laser weld hardness, transform coefficients a t and b t and the equation from the RHV (4) and (5) This is a part for calculating the parameters p1 to p4. That is, the conversion coefficient calculation formula creation unit 2 in the calculation system 10 functions as a first conversion coefficient calculation unit, a first hardness ratio calculation unit, and a parameter calculation unit. Here, the first conversion coefficient calculation unit is a part where the above-described step S2 can be performed, and the coefficients a s and b s of the constitutive equation of the spot weld fracture limit line selected from the database 1 and the laser weld fracture limit This is a part for calculating conversion coefficients a t and b t from the coefficients a l and b l of the line constitutive equation. The first hardness ratio calculation part is a part where the above-described step S3 can be performed, and a part for calculating the ratio RHv between the spot welded part hardness and the laser welded part hardness. The parameter calculation unit, in the step S4, and is a step S5 and enabling site, using the calculated RHv and transform coefficients a t, equation for calculating the transform coefficients a t represented by the above formula (4) This is a part where the parameters p1 and p2 are calculated, and the parameters p3 and p4 in the calculation formula of the conversion coefficient b t expressed by the above equation (5) are calculated using the calculated RHv and the conversion coefficient b t .
The conversion coefficient calculation formula creation unit 2 may be any means capable of executing the above-described steps S1 to S5. For example, a known arithmetic device in which spreadsheet software or the like is installed can be used as appropriate. In the conversion coefficient calculation formula creation unit 2, each coefficient of the constitutive formula of the fracture limit line recorded in the database 1 is input together with the weld metal hardness of the corresponding welding technique (spot welding and laser welding), and a spreadsheet software Accordingly, the above equation is the equation for calculating the transform coefficients a t and b t of fracture limit line configuration (4) and (5) is determined. The specific calculation contents are as described above, and the description is omitted here.
破断限界線変換部３は、レーザ溶接部の破断限界線を導出する対象となる鋼種の化学成分からスポット溶接部硬さとレーザ溶接部硬さとの比ＲＨｖを算出し、算出したＲＨｖを上記式（４）及び式（５）へとそれぞれ代入して変換係数ａｔ及びｂｔを算出することにより、レーザ溶接部の破断限界線を算出する部位である。すなわち、算出システム１０における破断限界線変換部３は、第２硬さ比算出部、第２変換係数算出部、及び、レーザ溶接部破断限界線構成式導出部として機能する。ここで、第２硬さ比算出部は、上記工程Ｓ６を実施可能な部位であり、レーザ溶接部の破断限界線の構成式が未導出である鋼種の化学成分を用いて、該鋼種に関する、スポット溶接部硬さＨｖ（ｓｐｏｔ）とレーザ溶接部硬さＨｖ（ｌａｓｅｒ）との比ＲＨｖ（＝Ｈｖ（ｌａｓｅｒ）／Ｈｖ（ｓｐｏｔ））を算出する部位である。また、第２変換係数算出部は、上記工程Ｓ７及び工程Ｓ８を実施可能な部位であり、第２硬さ比算出部で算出されたＲＨｖを上記式（４）へと代入することにより、レーザ溶接部の破断限界線の構成式で用いる変換係数ａｔを算出し、第２硬さ比算出部で算出されたＲＨｖを上記式（５）へと代入することにより、レーザ溶接部の破断限界線の構成式で用いる変換係数ｂｔを算出する部位である。また、レーザ溶接部破断限界線構成式導出部は、上記工程Ｓ９を実施可能な部位であり、あらかじめ破断限界線導出プロセスにより導出されている、上記式（１）で表されるスポット溶接部の破断限界線構成式で用いられる係数ａｓ及びｂｓと、変換係数ａｔ算出部で算出された変換係数ａｔと、変換係数ｂｔ算出部で算出された変換係数ｂｔとを、上記式（３）へと代入することにより、破断限界線構成式が導出されていなかった鋼種の、レーザ溶接部の破断限界線構成式を導出する部位である。
破断限界線変換部３は、上記工程Ｓ６〜工程Ｓ９を実行可能な手段であればよく、例えば、変換係数算出式作成部２と同様に、公知の演算装置を適宜用いることができる。破断限界線変換部３では、上記式（６）及び式（７）へ化学成分がパラメータ値として代入されることにより炭素当量が算出され、上記式（８）及び式（９）へ炭素当量がパラメータ値として代入されることによりスポット溶接部硬さ及びレーザ溶接部硬さが算出される。また、上記式（４）及び式（５）へ比ＲＨｖがパラメータ値として代入されることにより変換係数ａｔ及びｂｔが算出され、破断限界線導出プロセスで導出済みの評価対象鋼種のスポット溶接部破断限界線の係数ａｓ及びｂｓと、変換係数ａｔ及びｂｔとを上記式（３）へ代入することにより、レーザ溶接部破断限界線の構成式（式（２））が導出される。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 fracture limit line conversion unit 3 calculates a ratio RHv between the spot welded portion hardness and the laser welded portion hardness from the chemical composition of the steel type that is a target for deriving the fracture limit line of the laser welded portion, and calculates the calculated RHv by the above formula ( 4) and by calculating the transform coefficients a t and b t are substituted respectively into equation (5), a portion for calculating a fracture limit line of the laser welding unit. That is, the fracture limit line conversion unit 3 in the calculation system 10 functions as a second hardness ratio calculation unit, a second conversion coefficient calculation unit, and a laser welding part fracture limit line constitutive equation derivation unit. Here, the second hardness ratio calculation part is a part capable of performing the above-described step S6, using the chemical component of the steel type from which the constitutive equation of the fracture limit line of the laser welded part has not been derived, This is a part for calculating a ratio RHv (= Hv (laser) / Hv (spot)) between the spot welded portion hardness Hv (spot) and the laser welded portion hardness Hv (laser). The second conversion coefficient calculation unit is a part capable of performing the steps S7 and S8, and by substituting the RHv calculated by the second hardness ratio calculation unit into the equation (4), the laser calculating a conversion coefficient a t used in the construction type of weld fracture limit line, by the RHv calculated by the second hardness ratio calculator assigns to the above formula (5), the breaking limit of the laser weld This is a part for calculating the conversion coefficient b t used in the line constitutive equation. The laser weld fracture limit line constitutive equation derivation unit is a part where the step S9 can be performed, and is a spot welded part represented by the above formula (1) derived in advance by the fracture limit line derivation process. and the coefficient a s and b s used in fracture limit line configuration type, a conversion coefficient a t calculated by the conversion factor a t calculating section, and a conversion coefficient b t calculated by the conversion coefficient b t calculating section, the By substituting into equation (3), this is a part for deriving the fracture limit line constitutive equation of the laser weld of the steel type for which the fracture limit constitutive equation has not been derived.
The break limit line conversion unit 3 may be any means capable of executing the above steps S6 to S9. For example, as with the conversion coefficient calculation formula creation unit 2, a known arithmetic device can be used as appropriate. In the fracture limit line conversion unit 3, a carbon equivalent is calculated by substituting a chemical component as a parameter value into the above formulas (6) and (7), and the carbon equivalent is converted into the above formulas (8) and (9). By substituting as parameter values, spot weld hardness and laser weld hardness are calculated. Further, the formula (4) and (5) to the ratio RHv conversion coefficients a t and b t by being substituted is calculated as the parameter value, deriving already evaluated grades of spot welding fracture limit line derivation process By substituting the coefficients a s and b s of the fracture limit line and the conversion coefficients a t and b t into the above equation (3), a constitutive equation for the laser weld fracture limit line (equation (2)) is derived. Is done. The specific calculation contents are as described above, and the description is omitted here.
このように、算出システム１０は、算出方法Ｓ１０における準備工程Ｓ１で用いるデータを蓄積したデータベース１と、変換係数算出工程Ｓ２、第１硬さ比算出工程Ｓ３、第１パラメータ算出工程Ｓ４、及び、第２パラメータ算出工程Ｓ５を実施可能な変換係数算出式作成部２と、第２硬さ比算出工程Ｓ６、変換係数ａｔ算出工程Ｓ７、変換係数ｂｔ算出工程Ｓ８、及び、レーザ溶接部破断限界線構成式導出工程Ｓ９を実施可能な破断限界線変換部３を有しているので、算出方法Ｓ１０を実施することができる。したがって、かかる形態とすることにより、本発明によれば、破断限界線が未導出である鋼種について、高精度の破断限界線を算出することが可能な、算出システム１０を提供することができる。 Thus, the calculation system 10 includes the database 1 in which the data used in the preparation step S1 in the calculation method S10, the conversion coefficient calculation step S2, the first hardness ratio calculation step S3, the first parameter calculation step S4, and a conversion factor calculating equation generating unit 2 capable of performing a second parameter calculating step S5, the second hardness ratio calculating step S6, the conversion coefficient a t calculation step S7, the transform coefficients b t calculation step S8, and the laser welds breaking Since it has the fracture | rupture limit line conversion part 3 which can perform limit line constitutive equation derivation | leading-out process S9, calculation method S10 can be implemented. Therefore, according to the present invention, according to the present invention, it is possible to provide the calculation system 10 capable of calculating the fracture limit line with high accuracy for the steel type from which the fracture limit line has not been derived.
算出システム１０に関する上記説明では、それぞれ別々の、変換係数算出式作成部２、及び、破断限界線変換部３を有している形態を例示したが、本発明の第２実施形態に係る溶接部の破断限界線の算出システムは当該形態に限定されない。一の演算装置を変換係数算出式作成部２、及び、破断限界線変換部３として機能させても良い。 In the said description regarding the calculation system 10, although the form which has the conversion coefficient calculation formula preparation part 2 and the fracture | rupture limit line conversion part 3 which were respectively different was illustrated, the welding part which concerns on 2nd Embodiment of this invention. The fracture limit line calculation system is not limited to this form. One arithmetic unit may function as the conversion coefficient calculation formula creation unit 2 and the break limit line conversion unit 3.
４．溶接部を備えた部材の製造方法
本発明の第３実施形態に係る溶接部を備えた部材の製造方法（以下において、「本発明の製造方法」ということがある。）は、本発明の第１実施形態に係る溶接部の破断限界線の算出方法により算出された破断限界線を用いて有限要素法解析を行い、その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、このようにして決定された板組み、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有している。
4). Manufacturing method of member provided with welded portion A manufacturing method of a member provided with a welded portion according to the third embodiment of the present invention (hereinafter, also referred to as “manufacturing method of the present invention”) is the first of the present invention. The finite element method analysis is performed using the fracture limit line calculated by the calculation method of the fracture limit line of the weld according to the embodiment, and the plate assembly of the member, the size of the weld and / or the The welding position is determined, and the member is welded according to the plate assembly determined in this way, the size of the welded portion, and / or the welding position.
本発明の製造方法では、例えば、算出方法Ｓ１０により算出された破断限界線を用いて有限要素法解析を行い、その解析結果に基づいて継手の板組み、溶接ビードの幅、及び／又は、間隔を決定する。そして、決定された板組み、溶接ビードの幅、及び／又は、間隔にしたがって部材をレーザ溶接することで、レーザ溶接部を備えた継手を製造する形態、とすることができる。本発明の製造方法によれば、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により、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になる。 In the manufacturing method of the present invention, for example, the finite element method analysis is performed using the fracture limit line calculated by the calculation method S10, and based on the analysis result, the joint plate assembly, the weld bead width, and / or the interval To decide. And it can be set as the form which manufactures the joint provided with the laser welding part by carrying out laser welding of the member according to the determined board assembly, the width | variety of a welding bead, and / or a space | interval. According to the manufacturing method of the present invention, 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 welding portion breakage during collision deformation of the automobile and appropriately absorb energy.
本発明に関する上記説明では、主に、本発明が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ない。例えば、あらかじめ破断限界線導出プロセスにより、上記式（２）で表されるレーザ溶接部の破断限界線構成式が導出されている一方、スポット溶接部等のその他溶接手段により溶接された部位の破断限界線構成式が導出されていない場合には、上記式（１）を用いて上記式（２）を導出する上記説明の考え方を、上記式（２）を用いて上記式（１）を導出するように変換するほかは、上記形態と同様の手順により、レーザ溶接部の破断限界線構成式を用いて、破断限界線構成式を導出することができる。また、上記説明では、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について主に言及したが、本発明は当該形態に限定されない。チタンやアルミニウム等、他の金属材料で構成され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 regarding the present invention, the mode in which the present invention is applied to the analysis of laser welds is mainly exemplified, but the present invention is not limited to this mode. For example, the fracture limit line constitutive equation of the laser welded part represented by the above formula (2) is derived in advance by the fracture limit line derivation process, while the fracture of the part welded by other welding means such as a spot welded part When the limit line constitutive equation has not been derived, the above-described concept of deriving the above equation (2) using the above equation (1) is derived using the above equation (2). Except for conversion as described above, the fracture limit line constitutive equation can be derived using the fracture limit line constitutive equation of the laser welded portion by the same procedure as in the above embodiment. Moreover, in the said description, although mentioned mainly about the form applied when this invention uses steel materials as welding material, this invention is not limited to the said form. The present invention can be applied even when analyzing a welded member made of another metal material such as titanium or aluminum.
実施例を参照しつつ、本発明の算出方法についてさらに説明を続ける。 The calculation method of the present invention will be further described with reference to the examples.
上述の工程Ｓ１〜工程Ｓ５を行うことにより、上記式（４）及び式（５）のパラメータ（ｐ１、ｐ２、ｐ３、ｐ４）を得た。 The parameters (p1, p2, p3, p4) of the above formulas (4) and (5) were obtained by performing the above-described steps S1 to S5.
レーザ溶接部の破断限界線構成式が特定されていない金属材料の化学成分（質量％）は、以下の通りであった。
Ｃ：０．０８質量％
Ｓｉ：０．０５質量％
Ｍｎ：２．４３質量％
Ｐ：０．００９質量％
Ｓ：０．００１質量％
Ｃｒ：０．０２質量％
Ｍｏ：０．０１質量％
The chemical composition (mass%) of the metal material for which the fracture limit line constitutive equation of the laser welded part is not specified was as follows.
C: 0.08 mass%
Si: 0.05 mass%
Mn: 2.43 mass%
P: 0.009 mass%
S: 0.001 mass%
Cr: 0.02 mass%
Mo: 0.01% by mass
上記化学成分を、上記式（６）及び式（７）へと代入することにより、スポット溶接部炭素当量Ｃｅｑ（ｓｐｏｔ）及びレーザ溶接部炭素当量Ｃｅｑ（ｌａｓｅｒ）を算出した。算出されたスポット溶接部炭素当量は、Ｃｅｑ（ｓｐｏｔ）＝０．１１８であり、レーザ溶接部炭素当量は、Ｃｅｑ（ｌａｓｅｒ）＝０．１９３であった。次に、算出された炭素当量を上記式（８）及び式（９）へと代入することにより、スポット溶接部硬さＨｖ（ｓｐｏｔ）及びレーザ溶接部硬さＨｖ（ｌａｓｅｒ）を算出した。算出されたスポット溶接部硬さは、Ｈｖ（ｓｐｏｔ）＝３５９．５であり、レーザ溶接部硬さは、Ｈｖ（ｌａｓｅｒ）＝３２３．７であった。次に、これらの値を用いて、硬さ比ＲＨｖ（＝Ｈｖ（ｌａｓｅｒ）／Ｈｖ（ｓｐｏｔ））を計算した。計算された硬さ比は、ＲＨｖ＝０．９００４であった。このようにして得られたＲＨｖを上記式（４）及び式（５）へとそれぞれ代入することにより、変換係数ａｔ及びｂｔを算出した。算出された変換係数は、ａｔ＝１．０４３、ｂｔ＝０．８７４であった。次に、予め破断限界線導出プロセスで導出済みの評価対象鋼種のスポット溶接部破断限界線構成式から得られる係数ａｓ及びｂｓと、上記手順で算出した変換係数ａｔ及びｂｔを式（３）へと代入することにより、レーザ溶接部の破断限界線構成式を求めた。 By substituting the chemical components into the above formulas (6) and (7), the spot weld carbon equivalent Ceq (spot) and the laser weld carbon equivalent Ceq (laser) were calculated. The calculated spot weld carbon equivalent was Ceq (spot) = 0.118, and the laser weld carbon equivalent was Ceq (laser) = 0.193. Next, the spot welded portion hardness Hv (spot) and the laser welded portion hardness Hv (laser) were calculated by substituting the calculated carbon equivalent into the above formulas (8) and (9). The calculated spot weld hardness was Hv (spot) = 359.5, and the laser weld hardness was Hv (laser) = 323.7. Next, the hardness ratio RHv (= Hv (laser) / Hv (spot)) was calculated using these values. The calculated hardness ratio was RHv = 0.9004. The conversion coefficients at and bt were calculated by substituting the RHv thus obtained into the above formulas (4) and (5), respectively. The calculated conversion coefficients were at = 1.043 and bt = 0.874. Next, the coefficients as and bs obtained from the spot weld zone fracture limit line constitutive equation of the steel type to be evaluated that has been derived in the fracture limit line derivation process in advance, and the conversion coefficients at and bt calculated by the above procedure into formula (3) By substituting, the fracture limit line constitutive equation of the laser weld was obtained.
本発明の算出方法によりレーザ溶接部の破断限界線構成式を算出した金属材料は、引張強さ５９０ＭＰａ級、ヤング率２０６ＧＰａ、ポアソン比０．３の鋼種であった。この鋼種の真応力と塑性ひずみとの関係を図７に示す。図７に示した材料特性データと破断限界線データを、図８（ａ）及び図８（ｂ）に示すレーザ溶接継手の引張試験モデルに適用し、ＦＥＭ解析を行った。図８において、（ａ）は引張せん断に用いる継手Ｔ、（ｂ）はＬ字引張に用いる継手Ｌを示す。また、図８（ｃ）は溶接金属部分を示す図であり、１１に母材部分、１２にＨＡＺ部分、１３に溶接金属部分の真応力と塑性ひずみとの関係をそれぞれ設定する。また、図９（ａ）は継手Ｔの破断形態の解析結果を示す図であり、図９（ｂ）は継手Ｌの破断形態の解析結果を示す図である。図９（ｃ）に解析結果と試験結果の最大荷重の比較を示す。ＦＥＭ解析結果は、何れの継手においても試験結果と良好に対応した。すなわち、本発明によれば、レーザ破断限界線未導出の鋼種についても、破断限界線導出プロセスを省略して、破断限界線を精度よく算出できることが分かった。 The metal material for which the fracture limit line constitutive equation of the laser weld was calculated by the calculation method of the present invention was a steel type having a tensile strength of 590 MPa class, Young's modulus of 206 GPa, and Poisson's ratio of 0.3. The relationship between the true stress and the plastic strain of this steel type is shown in FIG. The material property data and fracture limit line data shown in FIG. 7 were applied to the tensile test model of the laser welded joint shown in FIGS. 8A and 8B, and FEM analysis was performed. In FIG. 8, (a) shows the joint T used for tensile shear, and (b) shows the joint L used for L-shaped tension. FIG. 8C is a view showing a weld metal portion, in which 11 is a base material portion, 12 is a HAZ portion, and 13 is a relationship between the true stress and plastic strain of the weld metal portion. FIG. 9A is a diagram showing an analysis result of the fracture mode of the joint T, and FIG. 9B is a diagram showing an analysis result of the fracture mode of the joint L. FIG. 9C shows a comparison of the maximum load between the analysis result and the test result. The FEM analysis results corresponded well with the test results in any joint. That is, according to the present invention, it was found that the fracture limit line can be calculated with high accuracy by omitting the fracture limit line derivation process even for the steel type from which the laser fracture limit line 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限界線を、精度良く算出することができる。これにより、ＦＥＭ解析の際、個別に破断限界線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。本発明により算出された破断限界線は、例えば、レーザ溶接継手の板組みや溶接ビード幅を検討するための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 limit line of the welding part used at the time of FEM analysis of the various members provided with the welding part can be calculated with sufficient precision. As a result, it is not necessary to perform the process of deriving the fracture limit line individually during the FEM analysis, and labor can be reduced. The break limit line calculated by the present invention can be used, for example, in the FEM analysis for studying the plate assembly and weld bead width of the laser welded joint, and the result is reflected in the vehicle member design. Can do.
１…データベース
２…変換係数算出式作成部
３…破断限界線変換部
４…入出力部
１０…溶接部の破断限界線の算出システム
１１…母材部分
１２…ＨＡＺ部分
１３…溶接金属部分
DESCRIPTION OF SYMBOLS 1 ... Database 2 ... Conversion coefficient calculation formula preparation part 3 ... Breaking limit line conversion part 4 ... Input-output part 10 ... Calculation system of the fracture limit line of a welding part 11 ... Base material part 12 ... HAZ part 13 ... Weld metal part
Claims (3)
あらかじめ破断限界線導出プロセスによりスポット溶接部の破断限界線及びレーザ溶接部の破断限界線が導出されている金属材料について、下記式（１）で表されるスポット溶接部の破断限界線の構成式、及び、下記式（２）で表されるレーザ溶接部の破断限界線の構成式を準備するとともに、下記式（２）の表現を変更した下記式（３）でレーザ溶接部の破断限界線の構成式を表現する、破断限界線構成式準備工程と、
下記式（１）で用いられる係数ａｓ及びｂｓと、下記式（２）で用いられる係数ａｌ及びｂｌから、下記式（３）で用いられる変換係数ａｔ及びｂｔを算出する、変換係数算出工程と、
スポット溶接部硬さ及びレーザ溶接部硬さの比ＲＨｖを算出する、第１硬さ比算出工程と、
算出した前記ＲＨｖ及び前記変換係数ａｔを用いて、下記式（４）で表される変換係数ａｔの算出式におけるパラメータｐ１及びｐ２を算出する、第１パラメータ算出工程と、
算出した前記ＲＨｖ及び前記変換係数ｂｔを用いて、下記式（５）で表される変換係数ｂｔの算出式におけるパラメータｐ３及びｐ４を算出する、第２パラメータ算出工程と、
レーザ溶接部の破断限界線の構成式が未導出である金属材料の化学成分を用いて、該金属材料のスポット溶接部硬さ及びレーザ溶接部硬さの比ＲＨｖを算出する、第２硬さ比算出工程と、
前記第２硬さ比算出工程で算出された前記ＲＨｖを下記式（４）へと代入することにより、レーザ溶接部の破断限界線の構成式で用いる変換係数ａｔを算出する、変換係数ａｔ算出工程と、
前記第２硬さ比算出工程で算出された前記ＲＨｖを下記式（５）へと代入することにより、レーザ溶接部の破断限界線の構成式で用いる変換係数ｂｔを算出する、変換係数ｂｔ算出工程と、
あらかじめ破断限界線導出プロセスにより導出されている、下記式（１）で表されるスポット溶接部の破断限界線構成式で用いられる係数ａｓ及びｂｓと、前記変換係数ａｔ算出工程で算出された変換係数ａｔと、前記変換係数ｂｔ算出工程で算出された変換係数ｂｔとを、下記式（３）へと代入することにより、レーザ溶接部の破断限界線の構成式を導出する、レーザ溶接部破断限界線構成式導出工程と、
を有する、溶接部の破断限界線の算出方法。
εｐ＝ａｓ・σｔｒｉａｘ＾ｂｓ （１）
εｐ＝ａｌ・σｔｒｉａｘ＾ｂｌ （２）
εｐ＝ａｓ・ａｔ・σｔｒｉａｘ＾（ｂｓ・ｂｔ） （３）
ａｔ＝ｐ１・ＲＨｖ＋ｐ２ （４）
ｂｔ＝ｐ３・ＲＨｖ＋ｐ４ （５）
前記式（１）〜（５）において、εｐは破断ひずみ、σｔｒｉａｘは応力三軸度（０．８＜σｔｒｉａｘ＜２．０）、ａｓ、ｂｓ、ａｌ、及び、ｂｌは鋼種・部位毎に異なる係数、ａｔ及びｂｔは鋼種・部位毎に異なる変換係数であり、ｐ１、ｐ２、ｐ３、及び、ｐ４はパラメータである。 A method for calculating a fracture limit line of a welded portion used when carrying out fracture prediction of a welded portion by a finite element method analysis,
Constituent formula of the fracture limit line of the spot welded part represented by the following formula (1) for a metal material in which the fracture limit line of the spot welded part and the fracture limit line of the laser welded part are derived in advance by the process of deriving the fracture limit line In addition, a constitutive equation for the fracture limit line of the laser welded part represented by the following formula (2) is prepared, and the fracture limit line for the laser welded part is expressed by the following formula (3) in which the expression of the following formula (2) is changed. Fracture limit line constitutive formula preparation process expressing the constitutive formula of
And the coefficient a s and b s used in the following formula (1), the coefficients a l and b l is used by the following formula (2), to calculate the transform coefficients a t and b t is used by the following formula (3) Conversion coefficient calculation step;
A first hardness ratio calculating step of calculating a ratio RHv of spot weld hardness and laser weld hardness;
Calculated using the RHv and the transform coefficients a t, calculates the parameters p1 and p2 in the equation for calculating the transform coefficients a t represented by the following formula (4), a first parameter calculating step,
A second parameter calculating step of calculating parameters p3 and p4 in a calculation formula of conversion coefficient b t represented by the following formula (5) using the calculated RHv and the conversion coefficient b t ;
A second hardness for calculating a ratio RHv of the spot welded portion hardness and the laser welded portion hardness of the metal material using a chemical component of the metal material for which the constitutive equation of the fracture limit line of the laser welded portion has not been derived. A ratio calculating step;
By substituting the RHv calculated in the second hardness ratio calculating step into the following formula (4), a conversion coefficient a t used in the constitutive expression of the fracture limit line of the laser weld is calculated. t calculation step;
By substituting the RHv calculated in the second hardness ratio calculation step into the following formula (5), a conversion coefficient b t used in the constitutive expression of the fracture limit line of the laser weld is calculated. t calculation step;
It is derived by pre-fracture limit line derivation process, and the coefficient a s and b s used in fracture limit line structure formula of the spot welds of the following formula (1), calculated by the conversion factor a t calculation step deriving a transform coefficient a t that is, a conversion coefficient b t the calculated conversion coefficient b t calculation step, by substituting into the following equation (3), the constitutive equation of the fracture limit line of the laser welding unit The laser welding part fracture limit line constitutive equation derivation step,
The calculation method of the fracture | rupture limit line of a welding part which has these.
ε p = a s · σ triax ^ b s (1)
ε p = a l · σ triax ^ b l (2)
ε p = a s · a t · σ triax ^ (b s · b t) (3)
a t = p1 · RHv + p2 (4)
b t = p3 · RHv + p4 (5)
In the above formulas (1) to (5), ε p is the strain at break, σ triax is the stress triaxiality (0.8 <σ triax <2.0), a s , b s , a l , and b l coefficients different for each steel type, site, a t and b t are different conversion factor for each steel type, site, p1, p2, p3, and, p4 are parameters.
前記破断限界線は、破断限界線構成式で近似され、
入出力部と、
金属材料の破断限界線構成式を蓄積したデータベースと、
変換係数算出式作成部と、
破断限界線変換部と、を有し、
前記変換係数算出式作成部は、
前記データベースから選択された、スポット溶接部破断限界線構成式の係数及びレーザ溶接部破断限界線構成式の係数を用いて、スポット溶接部破断限界線構成式からレーザ溶接部破断限界線構成式を導出する際に用いられる変換係数を算出する、第１変換係数算出部と、
スポット溶接部硬さとレーザ溶接部硬さとの比ＲＨｖを算出する第１硬さ比算出部と、
算出された前記ＲＨｖ及び前記変換係数を用いて、前記ＲＨｖと前記変換係数との関係式で用いられるパラメータを算出するパラメータ算出部と、を有し、
前記破断限界線変換部は、
レーザ溶接部の破断限界線構成式が未導出である金属材料の化学成分を用いて、該金属材料のスポット溶接部硬さとレーザ溶接部硬さとの比ＲＨｖを算出する、第２硬さ比算出部と、
前記第２硬さ比算出部で算出された前記ＲＨｖを、前記ＲＨｖと前記変換係数との前記関係式へと代入することにより、レーザ溶接部の破断限界線構成式で用いられる変換係数を算出する、第２変換係数算出部と、
あらかじめ破断限界線導出プロセスにより導出されているスポット溶接部の破断限界線構成式で用いられる係数と、前記第２変換係数算出部で算出された変換係数とを用いるレーザ溶接部の破断限界線構成式を導出する、レーザ溶接部破断限界線構成式導出部と、
を有する、溶接部の破断限界線の算出システム。 A system for calculating a fracture limit line of a weld used for carrying out a fracture prediction of a weld by a finite element method analysis,
The break limit line is approximated by a break limit line constitutive equation,
An input / output unit;
A database of rupture limit line constitutive equations for metal materials,
A conversion coefficient calculation formula creation unit;
Breaking limit line conversion section,
The conversion coefficient calculation formula creation unit
Using the coefficient of the spot weld fracture limit line constitutive formula and the coefficient of the laser weld fracture limit line constitutive formula selected from the database, the laser weld fracture limit line constitutive formula is calculated from the spot weld fracture limit line constitutive formula. A first conversion coefficient calculation unit for calculating a conversion coefficient used for deriving;
A first hardness ratio calculation unit for calculating a ratio RHv between the spot weld hardness and the laser weld hardness;
A parameter calculation unit that calculates a parameter used in a relational expression between the RHv and the conversion coefficient, using the calculated RHv and the conversion coefficient;
The breaking limit line conversion part is
Second hardness ratio calculation that calculates the ratio RHv between the spot welded portion hardness and the laser welded portion hardness of the metal material using the chemical component of the metal material for which the fracture limit line constitutive equation of the laser welded portion has not been derived. And
By substituting the RHv calculated by the second hardness ratio calculation section into the relational expression between the RHv and the conversion coefficient, the conversion coefficient used in the fracture limit line constitutive equation of the laser weld is calculated. A second conversion coefficient calculation unit;
Fracture limit line configuration of a laser weld using a coefficient used in the fracture limit line constitutive equation of the spot welded portion derived in advance by a fracture limit line derivation process and the conversion coefficient calculated by the second conversion coefficient calculating portion Deriving the equation, laser weld fracture limit line constitutive equation derivation unit,
A calculation system for a fracture limit line of a welded portion.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2017062205A (en) * | 2015-09-25 | 2017-03-30 | 新日鐵住金株式会社 | Calculation method of deformation resistance curve in weld zone, manufacturing method of component including weld zone, program, and computer readable-recording medium having program recorded thereon |
| JP2017062206A (en) * | 2015-09-25 | 2017-03-30 | 新日鐵住金株式会社 | Derivation method of fracture limit line in weld zone, manufacturing method of component including weld zone, program, and computer readable-recording medium having program recorded thereon |
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| US20030234239A1 (en) * | 2002-02-20 | 2003-12-25 | Hsu-Tung Lee | Method and system for assessing quality of spot welds |
| JP2005326401A (en) * | 2004-04-13 | 2005-11-24 | Nippon Steel Corp | Device, method, computer program for predicting rapture of spot welding part, and computer-readable recording medium |
| JP2007304005A (en) * | 2006-05-12 | 2007-11-22 | Nippon Steel Corp | Device, method, computer program for predicting rupture of spot welding part, and computer-readable recording medium |
| JP2009265028A (en) * | 2008-04-28 | 2009-11-12 | Nippon Steel Corp | Method and device for predicting breaking, and program and recording medium therefor |
| JP2013186102A (en) * | 2012-03-12 | 2013-09-19 | Nippon Steel & Sumitomo Metal | Prediction method and prediction system of fracture strain of welding part, and method for manufacturing member including welding part |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US20030234239A1 (en) * | 2002-02-20 | 2003-12-25 | Hsu-Tung Lee | Method and system for assessing quality of spot welds |
| JP2005326401A (en) * | 2004-04-13 | 2005-11-24 | Nippon Steel Corp | Device, method, computer program for predicting rapture of spot welding part, and computer-readable recording medium |
| JP2007304005A (en) * | 2006-05-12 | 2007-11-22 | Nippon Steel Corp | Device, method, computer program for predicting rupture of spot welding part, and computer-readable recording medium |
| JP2009265028A (en) * | 2008-04-28 | 2009-11-12 | Nippon Steel Corp | Method and device for predicting breaking, and program and recording medium therefor |
| JP2013186102A (en) * | 2012-03-12 | 2013-09-19 | Nippon Steel & Sumitomo Metal | Prediction method and prediction system of fracture strain of welding part, and method for manufacturing member including welding part |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2017062205A (en) * | 2015-09-25 | 2017-03-30 | 新日鐵住金株式会社 | Calculation method of deformation resistance curve in weld zone, manufacturing method of component including weld zone, program, and computer readable-recording medium having program recorded thereon |
| JP2017062206A (en) * | 2015-09-25 | 2017-03-30 | 新日鐵住金株式会社 | Derivation method of fracture limit line in weld zone, manufacturing method of component including weld zone, program, and computer readable-recording medium having program recorded thereon |
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| JP6277779B2 (en) | 2018-02-14 |
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