JP2011083813A - Analysis method for flange cracking - Google Patents
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本発明は、金属板をプレス成形することにより自動車部品その他のプレス成形品を設計・製造するに当たり、フランジ割れを回避する形状や成形条件を事前評価するために用いられるフランジ割れの分析方法に関するものである。 TECHNICAL FIELD The present invention relates to a flange crack analysis method used for pre-evaluating shapes and molding conditions to avoid flange cracks when designing and manufacturing automobile parts and other press-molded products by press-molding metal plates. It is.
自動車部品等の多くは金属板をプレス成形することにより製造されているが、部品形状、材質、成形条件などによってはプレス成形を行う際に割れが発生することがある。実際に部品をプレス成形しながら部品形状や成形条件を修正して行く旧来の方法は、金型の修正などに多くの時間とコストが必要である。そこで近年においては、コンピュータ上でプレス成形品の成形データを有限要素法により数値解析し、実物を用いた試行錯誤をなくす技術（例えば特許文献１）が開発されている。 Many automobile parts and the like are manufactured by press-molding a metal plate, but cracking may occur during press-molding depending on the part shape, material, molding conditions, and the like. The conventional method of correcting the part shape and molding conditions while actually press-molding the part requires a lot of time and cost for correcting the mold. Thus, in recent years, a technique (for example, Patent Document 1) has been developed that numerically analyzes molding data of a press-molded product on a computer by a finite element method to eliminate trial and error using the actual product.
プレス成形時に発生する欠陥のうち、絞り加工やフォーム加工などを行う際に面内において発生する割れについては、板厚減少率評価方法や成形限界図（ＦＬＤ）による評価方法が有効とされている。しかしエッジ部の割れについて既存の評価方法を適用しても、エッジ面の性状などの影響が大きく、実用できるほどの精度を確保することができない。特に金属板を湾曲した立体形状にプレス成形する場合には、湾曲の内側面において大きな引張応力が発生するためにフランジ割れと呼ばれる割れが発生し易い。この傾向は延性に乏しい高強度鋼板をプレス成形する場合に顕著である。そこでフランジ割れの予測分析を正確に行う技術が求められているが、未だ実用レベルに到達していないのが実情である。 Of the defects that occur during press forming, cracks that occur in-plane when drawing or foaming are carried out are evaluated by the plate thickness reduction rate evaluation method and the forming limit diagram (FLD) evaluation method. . However, even if an existing evaluation method is applied to the cracking of the edge portion, the influence of the properties of the edge surface is large, and it is not possible to ensure the accuracy to be practical. In particular, when a metal plate is press-formed into a curved solid shape, a large tensile stress is generated on the inner surface of the curve, so that a crack called a flange crack is likely to occur. This tendency is remarkable when a high-strength steel sheet having poor ductility is press-formed. Therefore, there is a need for a technique that accurately performs flange crack prediction analysis, but the actual situation is that it has not yet reached a practical level.
成形データを有限要素法により数値解析し、この成形データ中から成形品のエッジ部を検出し、検出されたエッジ部における最大主歪値を求めれば、フランジ割れが発生する点を求めることはできる。しかしその最大主歪値を単純に材料の破断限界歪値と比較しても、実際にどの程度のフランジ割れが発生するか、あるいは発生しないのかを特定することはできない。本発明者等の研究によれば、フランジ割れの発生状況を予測するには、エッジ部における最大主歪値だけではなく、その周辺の歪勾配を考慮する必要がある。しかしこれまでその具体的な演算をコンピュータ上で自動的に行わせるための技術は開発されていない。 If the molding data is numerically analyzed by the finite element method, the edge portion of the molded product is detected from the molding data, and the maximum principal strain value at the detected edge portion is obtained, the point where the flange crack occurs can be obtained. . However, even if the maximum principal strain value is simply compared with the fracture limit strain value of the material, it cannot be specified how much flange cracking actually occurs or does not occur. According to the study by the present inventors, in order to predict the occurrence of flange cracks, it is necessary to consider not only the maximum principal strain value at the edge portion but also the strain gradient around it. However, until now, no technology has been developed for automatically performing the specific calculation on the computer.
従って本発明の目的は上記した従来の問題点を解決し、フランジ割れの発生状況をコンピュータ上で正確に予測させることができるフランジ割れの分析方法を提供することである。 Accordingly, an object of the present invention is to provide a flange crack analysis method capable of solving the above-described conventional problems and accurately predicting the occurrence of flange cracks on a computer.
上記の課題を解決するためになされた本発明は、有限要素法によりプレス成形工程を数値解析して成形データを取り出し、この成形データ中から成形品のエッジ部を検出し、検出されたエッジ部について主歪の値が最大となる要素と、その最大の最大主歪値を生ずる要素を基準要素として、任意の方向に隣接する要素列を要素選択アルゴリズムに基づいて自動的に特定し、特定された要素列の各要素が持つ最大主歪値から歪分布及びその勾配を演算し、前記最大主歪値とこれらの歪分布及び歪勾配とに基づいてエッジ部に生ずるフランジ割れを分析することを特徴とするものである。尚、最大主歪とは、ある要素の中で一番歪が大きい方向の歪のことをいう。 The present invention made to solve the above-mentioned problems is a numerical analysis of the press molding process by a finite element method to extract molding data, detect the edge of the molded product from this molding data, and detect the detected edge With the element having the largest principal distortion value and the element that produces the largest maximum principal distortion value as the reference element, the element sequence adjacent in any direction is automatically identified based on the element selection algorithm. The strain distribution and the gradient thereof are calculated from the maximum principal strain value of each element in the element row, and the flange crack generated in the edge portion is analyzed based on the maximum principal strain value and the strain distribution and strain gradient. It is a feature. The maximum principal strain means a strain in a direction in which the strain is the largest among certain elements.
なお要素選択アルゴリズムは、請求項２のように、基準要素のエッジ部に沿った辺の中点を通りエッジ部に垂直な平面と交差する同一基準要素の辺を特定し、抽出された辺を共有する隣接要素を抽出し、この辺の中点を通りこの辺に垂直な平面と交差する同一要素の辺を特定するステップを繰り返して要素列を特定するものとすることができる。 The element selection algorithm specifies the side of the same reference element that passes through the midpoint of the side along the edge portion of the reference element and intersects the plane perpendicular to the edge portion, as in claim 2, and extracts the extracted side. The element sequence can be specified by repeating the step of extracting the adjacent elements to be shared and specifying the side of the same element that passes through the midpoint of the side and intersects the plane perpendicular to the side.
また要素選択アルゴリズムは、請求項３のように、基準要素のエッジ部に沿った辺の中点を通りエッジ部に垂直な平面と２点以上で交差し、かつ各要素の重心からこの平面に降ろした垂線が同一要素内でこの平面と交わる要素を選択して要素列を特定するものとすることができる。 The element selection algorithm, as in claim 3, crosses a plane perpendicular to the edge portion through the midpoint of the side along the edge portion of the reference element at two or more points, and from the center of gravity of each element to this plane. It is possible to specify an element row by selecting an element in which the dropped perpendicular intersects this plane within the same element.
さらに要素選択アルゴリズムは、請求項４のように、基準要素のエッジ部に沿った辺とは異なる辺と辺を共有する複数の隣接要素のうち、最大主歪値が最大の隣接要素を抽出し、この辺とは異なる辺と辺を共有する複数の隣接要素のうち、最大主歪値が最大の隣接要素を抽出するステップを繰り返して要素列を特定するものとすることができる。 Further, the element selection algorithm extracts an adjacent element having a maximum maximum principal strain value from a plurality of adjacent elements sharing a side with a side different from the side along the edge portion of the reference element. The element sequence can be specified by repeating the step of extracting the adjacent element having the maximum maximum principal distortion value from among the plurality of adjacent elements sharing the side and the side different from the side.
さらに要素選択アルゴリズムは、請求項５のように、基準要素のエッジ部方向に沿った要素を抽出するステップを繰り返して要素列を特定し、それぞれの要素から基準要素のエッジ部に沿ったエッジ部分の節点について、その節点間の変位を時系列的に抽出することにより歪を抽出することができる。 Further, the element selection algorithm repeats the step of extracting elements along the edge portion direction of the reference element to specify an element row, and the edge portion along the edge portion of the reference element from each element. The distortion can be extracted by extracting the displacement between the nodes in time series.
本発明によれば、有限要素法によりプレス成形工程を数値解析して得られたプレス成形品の成形データから、最大主歪値を生ずる要素を抽出してその最大主歪値が材料の破断限界歪値を超えているか否かを判断するだけではなく、抽出された基準要素からエッジ部方向の歪勾配と、エッジ部に垂直方向の歪勾配、またはエッジ部と任意の方向の歪勾配を演算し、前記最大主歪値とこれらの歪勾配とに基づいてエッジ部に生ずるフランジ割れを分析する。このため、後述するようにフランジ割れの発生状況を正確に分析することができる。 According to the present invention, the element that produces the maximum principal strain value is extracted from the molding data of the press-molded product obtained by numerical analysis of the press molding process by the finite element method, and the maximum principal strain value is the fracture limit of the material. In addition to determining whether or not the strain value is exceeded, calculate the strain gradient in the edge direction and the strain gradient in the direction perpendicular to the edge portion, or the strain gradient in the edge portion and any direction from the extracted reference element Then, the flange crack generated in the edge portion is analyzed based on the maximum principal strain value and the strain gradient. For this reason, the generation | occurrence | production state of a flange crack can be accurately analyzed so that it may mention later.
また、エッジ部を構成する要素は従来手法により成形データ中から容易に特定することができるが、基準要素からエッジ部に垂直方向に隣接する要素を順次選択することは従来は人手に拠らざるを得なかった。しかし本発明によれば、基準要素からエッジ部に垂直方向に隣接する要素を要素選択アルゴリズムに基づいて自動的に特定し、特定された要素列の各要素が持つ最大主歪値からエッジ部に垂直方向、または任意の方向の歪勾配を演算することができるので自動的に演算を行わせることが可能となり、予測分析をより短時間で行うことが可能となる。その具体的内容は、後述する。 In addition, the elements constituting the edge portion can be easily specified from the molding data by the conventional method, but selecting the elements adjacent to the edge portion in the vertical direction from the reference element in the past is not manually performed. Did not get. However, according to the present invention, the element that is adjacent to the edge portion in the vertical direction from the reference element is automatically specified based on the element selection algorithm, and the maximum principal strain value of each element of the specified element row is changed to the edge portion. Since the distortion gradient in the vertical direction or an arbitrary direction can be calculated, the calculation can be automatically performed, and the prediction analysis can be performed in a shorter time. The specific contents will be described later.
以下に本発明の実施形態を説明するが、それに先立ってフランジ割れが発生し易い伸びフランジ成形を説明する。
図１に示すように台形に打ち抜かれた金属板を、平面視すると湾曲しており、断面形状がハット状である湾曲立体形状にプレス成形すると、湾曲の内側のフランジ面には均一伸びを越える大きな伸びが生じる。このようなプレス成形を伸びフランジ成形という。このような伸びフランジ成形を行うと特に内側フランジのエッジ部において大きな引張応力が発生し、フランジ割れが発生し易くなる。このフランジ割れを予測するため、本発明では図２に示す手順を実行する。
In the following, embodiments of the present invention will be described. Prior to that, stretch flange molding in which flange cracking is likely to occur will be described.
As shown in FIG. 1, when a metal plate punched in a trapezoidal shape is curved when viewed in plan, and is press-molded into a curved solid shape having a hat-like cross-sectional shape, the flange surface inside the curve exceeds the uniform elongation. Large elongation occurs. Such press molding is called stretch flange molding. When such stretch flange molding is performed, a large tensile stress is generated particularly at the edge portion of the inner flange, and a flange crack is likely to occur. In order to predict this flange crack, the present invention executes the procedure shown in FIG.
まず、対象部品である成形品の形状を有限要素法により多数の要素の集合体として表現し、プレス成形シミュレーションを行って成形解析（ステップ１）を行う。この成形解析は特許文献１にも記載されている既存の技術である。この成形解析によって、成形の各段階における成形データが取得される。成形データには各要素の形状及び歪のデータが含まれている。本発明はフランジ割れを予測分析することを目的とするため、成形データから成形品のフランジのエッジ部を検出する（ステップ２）。エッジ部の検出は、隣接する要素を持たない要素を選択する方法によってコンピュータ上で自動的に行うことができる。 First, the shape of the molded product that is the target part is expressed as an aggregate of a large number of elements by the finite element method, and press molding simulation is performed to perform molding analysis (step 1). This molding analysis is an existing technique described in Patent Document 1. Molding data at each stage of molding is acquired by this molding analysis. The molding data includes shape and strain data of each element. Since the present invention aims to predict and analyze flange cracks, the edge of the flange of the molded product is detected from the molding data (step 2). The edge portion can be automatically detected on a computer by a method of selecting an element that does not have an adjacent element.
次に、検出されたエッジ部について最大主歪値を検出する（ステップ３）。これはエッジ部を構成する各要素が持つ最大主歪値のうちの最大値を求めることにより容易に実行できる。従来はこのようにして求めたエッジ部の最大主歪値を材料の破断限界歪値と比較してフランジ割れを予測していたのであるが、その予測精度が悪く実用性がないことは前述したとおりである。 Next, the maximum principal distortion value is detected for the detected edge portion (step 3). This can be easily performed by obtaining the maximum value among the maximum principal strain values of the elements constituting the edge portion. In the past, flange cracks were predicted by comparing the maximum principal strain value of the edge portion thus determined with the fracture limit strain value of the material, but it was mentioned above that the prediction accuracy was poor and there was no practicality. It is as follows.
そこで本発明では、最大主歪値を生ずる要素を基準要素とするエッジ部方向の歪勾配と、この基準要素からエッジ部に垂直方向の歪勾配、またはエッジ部に対し任意の方向のひずみ勾配とを演算（ステップ４）し、前記最大主歪値とこれらの歪勾配とに基づいてフランジ割れを予測分析（ステップ５）することとした。歪勾配がフランジ割れに及ぼす影響は、次の通りである。 Therefore, in the present invention, the strain gradient in the edge direction with the element that generates the maximum principal strain value as the reference element, and the strain gradient in the direction perpendicular to the edge portion from this reference element, or the strain gradient in any direction with respect to the edge portion, Was calculated (step 4), and the flange crack was predicted and analyzed (step 5) based on the maximum principal strain value and the strain gradient. The effect of strain gradient on flange cracking is as follows.
まず最大主歪値を生ずる要素を基準要素とするエッジ部方向の歪勾配については、その値が大きいほどエッジ上の特定ポイント（基準要素の位置）に引張応力が集中していることを意味するものであるから、エッジ部方向の歪勾配が大きいほどフランジ割れが生じ易いといえる。これに対してエッジ部に垂直方向または任意の方向の歪勾配については、歪勾配が大きいほどフランジ割れが生じにくくなる。エッジ部に垂直方向または任意の方向の歪勾配が大きいということは、エッジ部から僅かに内側では急速に歪が小さくなることを意味するから、仮にエッジ部においてミクロ的なフランジ割れが発生しても、それ以上進展しない。 First, for the strain gradient in the edge direction with the element that produces the maximum principal strain value as the reference element, the larger the value, the more concentrated the tensile stress is at a specific point (position of the reference element) on the edge. Therefore, it can be said that the larger the strain gradient in the edge portion direction, the easier the flange cracking occurs. On the other hand, regarding the strain gradient in the direction perpendicular to the edge portion or in an arbitrary direction, the greater the strain gradient, the less likely the flange cracks to occur. The fact that the strain gradient in the direction perpendicular to the edge or in any direction is large means that the strain rapidly decreases slightly inside the edge, so that micro-flange cracking occurs at the edge. But no further progress.
このように、フランジ割れは、エッジ部の最大主歪値と、エッジ部方向の歪勾配と、エッジ部に垂直方向または任意の方向の歪勾配とを考慮することによって、単にエッジ部の最大主歪値のみを考慮していた従来法よりも、予測精度を高めることが可能となる。例えば、成形データ中のエッジ部の最大主歪値が材料の破断限界歪値を超えていなくても、エッジ部方向の歪勾配が急峻であれば、ミクロ的には材料の破断限界歪値を超える最大主歪値に達する点が存在する可能性がある。また成形データ中のエッジ部の最大主歪値が材料の破断限界歪値を超えていても、エッジ部に垂直方向または任意の方向の歪勾配が急峻であれば、問題となるようなフランジ割れが発生しない可能性がある。 In this way, the flange crack is simply determined by considering the maximum principal strain value of the edge portion, the strain gradient in the direction of the edge portion, and the strain gradient in the direction perpendicular to the edge portion or in an arbitrary direction. The prediction accuracy can be improved as compared with the conventional method in which only the distortion value is considered. For example, even if the maximum principal strain value of the edge part in the molding data does not exceed the fracture limit strain value of the material, if the strain gradient in the edge direction is steep, the fracture limit strain value of the material is microscopically. There may be points that reach a maximum principal strain value that exceeds. Even if the maximum principal strain value of the edge portion in the molding data exceeds the fracture limit strain value of the material, if the strain gradient in the direction perpendicular to the edge portion or in any direction is steep, a flange crack that causes a problem May not occur.
上記の理由により、本発明では最大主歪値を生ずる要素を基準要素とするエッジ部方向の歪勾配と、この基準要素からエッジ部に垂直方向または任意の方向の歪勾配とを演算するのであるが、エッジ部方向の歪勾配は、エッジ部を構成する各要素の歪値から簡単に演算できるのに対して、基準要素からエッジ部に垂直方向または任意の方向の歪勾配を自動的に演算することは容易ではない。その理由は、有限要素法においてメッシュ切りされた要素は必ずしも碁盤の目のように整列しているのではなく、湾曲形状の部品においては要素の形状も台形状や三角形状をなしているため、基準要素からエッジ部に垂直方向または任意の方向の線を引いただけでは、選択すべき要素を一義的に決定できない場合があるからである。エッジ部に垂直方向または任意の方向の歪勾配を自動的に演算させるためには、どの要素を選択するかを明確化しておく必要がある。 For the above reasons, in the present invention, the strain gradient in the edge direction with the element that produces the maximum principal strain value as the reference element and the strain gradient in the direction perpendicular to the edge portion or in an arbitrary direction are calculated from this reference element. However, while the strain gradient in the edge direction can be easily calculated from the strain value of each element that constitutes the edge portion, the strain gradient in the vertical direction or arbitrary direction from the reference element is automatically calculated. It is not easy to do. The reason is that the elements cut by mesh in the finite element method are not necessarily aligned like a grid, but in curved parts, the shape of the elements is also trapezoidal or triangular, This is because the element to be selected may not be uniquely determined only by drawing a line in the vertical direction or an arbitrary direction from the reference element to the edge portion. In order to automatically calculate the distortion gradient in the vertical direction or arbitrary direction in the edge portion, it is necessary to clarify which element is selected.
そこで本発明では、エッジ部に垂直方向または任意の方向の歪勾配を演算するステップ中に、基準要素からエッジ部に垂直方向または任意の方向に隣接する要素列を自動的に特定できる要素選択アルゴリズムを組み込み、この要素選択アルゴリズムに基づいて特定された要素列の各要素が持つ歪値から、エッジ部に垂直方向または任意の方向の歪勾配を演算する。以下にこの要素選択アルゴリズムを具体的に説明する。また、併せてエッジ部方向の要素選択アルゴリズムについても具体的に説明する。 Therefore, in the present invention, an element selection algorithm capable of automatically specifying an element string adjacent to the edge portion in the vertical direction or in the arbitrary direction from the reference element during the step of calculating the distortion gradient in the vertical direction or arbitrary direction in the edge portion. Is calculated, and the distortion gradient in the vertical direction or arbitrary direction is calculated from the distortion value of each element of the element string specified based on this element selection algorithm. The element selection algorithm will be specifically described below. In addition, the element selection algorithm in the edge portion direction will be specifically described.
図３は第１の要素選択アルゴリズムの説明図である。このアルゴリズムでは、まず基準要素Ａのエッジ部に沿った辺ａの中点を通り，エッジ部に垂直な平面Ｐ１を仮想する。次にこの平面Ｐと交差する同一基準要素Ａの辺ｂを特定し、抽出された辺ｂを共有する隣接要素Ｂを抽出する。次に隣接要素Ｂの辺ｂの中点を通り、この辺ｂに垂直な平面Ｐ２と交差する同一要素の辺ｃを特定し、抽出された辺ｂを共有する隣接要素Ｃを抽出するステップを繰り返して要素列を特定して行く。このようにして選択された要素列の歪値から、最大主歪値を抽出し、エッジ部に垂直方向の歪勾配を演算することができる。この場合、最大主歪値の代わりに基準要素のエッジ部に沿った方向成分の歪値を使用してもよい。 FIG. 3 is an explanatory diagram of the first element selection algorithm. In this algorithm, first, a plane P1 that passes through the midpoint of the side a along the edge portion of the reference element A and is perpendicular to the edge portion is assumed. Next, the side b of the same reference element A that intersects the plane P is specified, and the adjacent element B that shares the extracted side b is extracted. Next, the step of identifying the side c of the same element that passes through the midpoint of the side b of the adjacent element B and intersects the plane P2 perpendicular to the side b, and extracting the adjacent element C that shares the extracted side b is repeated. And specify the element sequence. The maximum principal strain value can be extracted from the strain value of the element row selected in this way, and the strain gradient in the direction perpendicular to the edge portion can be calculated. In this case, the distortion value of the direction component along the edge portion of the reference element may be used instead of the maximum principal distortion value.
図４は第２の要素選択アルゴリズムの説明図である。このアルゴリズムでは、基準要素Ａのエッジ部に沿った辺ａの中点を通りエッジ部に垂直な平面Ｐ１を仮想する。そしてこの仮想した平面Ｐ１と２点以上で交差する要素を選択する。これによって要素Ａ，Ｂ，Ｃ，Ｄ，Ｅ，Ｆ・・・が選択される。しかし要素Ｄと要素Ｅのように、端部がこの平面Ｐ１とわずかに交差する要素については、何れを選択するかの基準を定めて置く必要がある。そこで、ここでは各要素の重心からこの平面Ｐ１に降ろした垂線Ｌが同一要素内でこの平面Ｐ１と交わる要素を選択するが、この基準を満たさない要素は選択から外す。この結果、要素Ｄは除外され要素Ｅが選択される。図４中には選択された要素に星印を付けた。 FIG. 4 is an explanatory diagram of the second element selection algorithm. In this algorithm, a plane P1 that passes through the midpoint of the side a along the edge of the reference element A and is perpendicular to the edge is assumed. Then, an element that intersects the virtual plane P1 at two or more points is selected. As a result, the elements A, B, C, D, E, F... Are selected. However, as for the element D and the element E, for the element whose end portion slightly intersects the plane P1, it is necessary to set a criterion for selecting which one. Therefore, here, an element is selected in which the perpendicular L drawn from the center of gravity of each element to the plane P1 intersects the plane P1 in the same element, but elements that do not satisfy this criterion are excluded from the selection. As a result, element D is excluded and element E is selected. In FIG. 4, the selected element is marked with an asterisk.
図５は第３の要素選択アルゴリズムの説明図である。このアルゴリズムでは、基準要素Ａのエッジ部に沿った辺ａとは異なる歪進展方向の辺と辺を共有する複数の隣接要素Ｂ１，Ｂ２，Ｂ３のうち、最大主歪値が最大の隣接要素Ｂ１を抽出し、この辺とは異なる辺と辺を共有する複数の隣接要素Ｃ１，Ｃ２，Ｃ３のうち、最大主歪値が最大の隣接要素Ｃ１を抽出するステップを繰り返して要素列を特定して行く。このアルゴリズムによれば、最大主歪値が最大の隣接要素を順次選択するため、部品の成形過程による歪進展方向が変化しても任意の方向への追従が可能となる。 FIG. 5 is an explanatory diagram of the third element selection algorithm. In this algorithm, among the plurality of adjacent elements B1, B2, and B3 that share a side in a strain propagation direction different from the side a along the edge portion of the reference element A, the adjacent element B1 having the maximum maximum main strain value. And the step of extracting the adjacent element C1 having the maximum maximum principal distortion value among the plurality of adjacent elements C1, C2, and C3 sharing the side and the side different from this side is repeated to specify the element string. . According to this algorithm, since adjacent elements having the maximum maximum principal strain value are sequentially selected, it is possible to follow in any direction even if the strain propagation direction changes due to the molding process of the part.
図６は第４の要素選択アルゴリズムの説明図である。このアルゴリズムでは、基準要素Ａのエッジ部に沿った辺ａの方向の要素をＢ１、Ｂ２の順に、及びＣ１、Ｃ２の順に抽出するステップを繰り返して要素列を特定し、それぞれの要素から基準要素のエッジ部に沿ったエッジ部分の節点ＮＢ１、ＮＢ２の順に、及びＮＣ１、ＮＣ２の順について、その節点間の変位を時系列的に抽出することにより歪を抽出する。 FIG. 6 is an explanatory diagram of the fourth element selection algorithm. In this algorithm, the element sequence is identified by repeating the steps of extracting elements in the direction of the side a along the edge portion of the reference element A in the order of B1, B2, and in the order of C1, C2, and the reference element is determined from each element. Distortion is extracted by extracting the displacement between the nodes in the order of the nodes NB1 and NB2 of the edge portion along the edge portion and the order of NC1 and NC2.
上記したように、本発明によれば、基準要素からエッジ部に垂直方向または任意の方向に隣接する要素を要素選択アルゴリズムに基づいて自動的に特定し、特定された要素列の各要素が持つ最大主歪値からエッジ部に垂直方向または任意の方向の歪勾配を演算することができる。従って従来のようにプレス成形品の成形データから、最大主歪値を生ずる要素を抽出してその最大主歪値が材料の破断限界歪値を超えているか否かを判断するだけではなく、抽出された基準要素からエッジ部方向の歪勾配と、エッジ部に垂直方向または任意の方向の歪勾配を演算し、前記最大主歪値とこれらの歪勾配とに基づいてエッジ部に生ずるフランジ割れを予測分析することができ、フランジ割れの発生状況を正確に予測分析することが可能となる。 As described above, according to the present invention, elements that are adjacent to the edge portion in the vertical direction or in an arbitrary direction from the reference element are automatically specified based on the element selection algorithm, and each element of the specified element row has A strain gradient in a direction perpendicular to the edge portion or an arbitrary direction can be calculated from the maximum principal strain value. Therefore, not only is it possible to extract the element that generates the maximum principal strain value from the molding data of the press-formed product as in the past, but to determine whether the maximum principal strain value exceeds the fracture limit strain value of the material. The distortion gradient in the edge portion direction and the distortion gradient in the direction perpendicular to the edge portion or in any direction are calculated from the reference element thus formed, and the flange crack generated in the edge portion based on the maximum principal strain value and these strain gradients is calculated. Predictive analysis can be performed, and the occurrence of flange cracks can be accurately predicted and analyzed.
本発明の実施例として、図７に示すフランジ割れ評価エッジ部aを持つブランク板１を作成し、このブランク板１を図８に示すサイドベンド試験をシミュレートすることにより、フランジ割れの発生状況の分析を行った。 As an example of the present invention, a blank plate 1 having a flange crack evaluation edge portion a shown in FIG. 7 is prepared, and a side bend test shown in FIG. Was analyzed.
本実施例では、ブランク板１は、板厚１．６ｍｍ、引張強さ５９０ＭＰａ級冷延鋼板を用いて有限要素法により成形解析を実施した。有限要素法のソルバーには、市販のＦＥＭコードであるＬＳ−ＤＹＮＡを使用した。また、初期要素サイズは、３ｍｍとした。 In this example, the blank plate 1 was subjected to forming analysis by a finite element method using a cold-rolled steel plate having a thickness of 1.6 mm and a tensile strength of 590 MPa. For the finite element method solver, LS-DYNA, which is a commercially available FEM code, was used. The initial element size was 3 mm.
はじめに、サイドベンド試験の成形解析の結果を用いて、図３に示す第１の要素選択アルゴリズムによりひずみを抽出し、ひずみ分布及びひずみ勾配を算出した結果を図９、図１０、図１１に示す。図１０の結果は、実際のサイドベンド試験の結果と同様な結果を得ており、フランジ割れの発生状況を分析できる。 First, using the results of the molding analysis of the side bend test, the strain is extracted by the first element selection algorithm shown in FIG. 3, and the results of calculating the strain distribution and strain gradient are shown in FIG. 9, FIG. 10, and FIG. . The result of FIG. 10 has obtained the same result as the result of the actual side bend test, and the occurrence of flange cracks can be analyzed.
次に、前記サイドベンド試験の成形解析の結果を用いて、図４に示す第２の要素選択アルゴリズムによりひずみを抽出し、ひずみ分布及びひずみ勾配を算出した結果を図１２、図１０に示す。図１０の結果は、実際のサイドベンド試験の結果と同様な結果を得ており、フランジ割れの発生状況を分析できる。 Next, using the result of the molding analysis of the side bend test, the results of extracting the strain by the second element selection algorithm shown in FIG. 4 and calculating the strain distribution and strain gradient are shown in FIGS. The result of FIG. 10 has obtained the same result as the result of the actual side bend test, and the occurrence of flange cracks can be analyzed.
更に、前記サイドベンド試験の成形解析の結果を用いて、図５に示す第３の要素選択アルゴリズムによりひずみを抽出し、ひずみ分布及びひずみ勾配を算出した結果を図１３、図１０に示す。図１０の結果は、実際のサイドベンド試験の結果と同様な結果を得ており、フランジ割れの発生状況を分析できる。 Furthermore, using the result of the molding analysis of the side bend test, the strain is extracted by the third element selection algorithm shown in FIG. 5, and the results of calculating the strain distribution and strain gradient are shown in FIGS. The result of FIG. 10 has obtained the same result as the result of the actual side bend test, and the occurrence of flange cracks can be analyzed.
また、前記サイドベンド試験の成形解析の結果を用いて、図６に示す第４の要素選択アルゴリズムによりひずみを抽出し、ひずみ分布及びひずみ勾配を算出した結果を図１４、図１５、図１６に示す。図１５の結果は、実際のサイドベンド試験の結果と同様な結果を得ており、フランジ割れの発生状況を分析できる。 Moreover, using the result of the molding analysis of the side bend test, the strain is extracted by the fourth element selection algorithm shown in FIG. 6, and the results of calculating the strain distribution and strain gradient are shown in FIGS. Show. The result of FIG. 15 has obtained the same result as the result of the actual side bend test, and the occurrence of flange cracks can be analyzed.
Claims (5)
The element selection algorithm repeats the step of extracting elements along the edge direction of the reference element to identify the element sequence, and for each node of the edge portion along the edge of the reference element from each element, the nodes between the nodes are identified. 2. The flange crack analysis method according to claim 1, wherein the strain is extracted by extracting the displacement in time series.
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