JP5210100B2 - Impact fracture prediction method - Google Patents
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- JP5210100B2 JP5210100B2 JP2008237772A JP2008237772A JP5210100B2 JP 5210100 B2 JP5210100 B2 JP 5210100B2 JP 2008237772 A JP2008237772 A JP 2008237772A JP 2008237772 A JP2008237772 A JP 2008237772A JP 5210100 B2 JP5210100 B2 JP 5210100B2
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Description
本発明は、精度の高い樹脂成形品の衝撃破壊予測方法に関する。 The present invention relates to an impact fracture prediction method for a resin molded product with high accuracy.
樹脂は粘弾性体であり、早く変形すればするほど硬くなり脆性的なる性質を持つ。樹脂はこの性質を持っているために、シミュレーションの際に変形の際の歪み速度がわからないと正確な破断歪みが予想できない。 The resin is a viscoelastic body and has the property of becoming harder and more brittle as it is deformed faster. Since the resin has this property, an accurate fracture strain cannot be predicted unless the strain rate at the time of deformation is known during simulation.
また、成形された樹脂成形品は、流動方向と異なる方向では強度及び破断に至る歪みが異なる性質を持っている。このため、樹脂成形品においては、衝撃シミュレーション結果における最大発生歪み以外の部位から破断する場合がある。そこで、樹脂製品の異方性を考慮した樹脂製品の衝撃破壊予測方法が知られている（特許文献１）。 In addition, the molded resin molded product has properties that the strength and strain leading to breakage are different in a direction different from the flow direction. For this reason, in a resin molded product, it may fracture | rupture from parts other than the largest generation | occurrence | production distortion in an impact simulation result. Therefore, a method for predicting the impact fracture of a resin product in consideration of the anisotropy of the resin product is known (Patent Document 1).
特許文献１によると、樹脂成形品の異方性を考慮する際、流動方向ならびに流動直角方向の平均値を用いて解析精度を高めている。しかしながら、入力物性が平均値であるため、実際の破損歪許容値よりも流動方向では低く、流動直角方向では、高い値での判定となり、誤った判断を行う可能性が高い。
According to
また、所定形状の樹脂成形品を用いた実試験結果と、衝撃シミュレーションの結果とを比較して、両者の変形挙動が一致する場合の破壊判定値を採用する方法が知られている（特許文献２）。この特許文献２に記載の方法では、実試験を実施しなければ判定が行えない。 Also, a method is known in which the actual test result using a resin molded product of a predetermined shape is compared with the result of an impact simulation, and the failure determination value is adopted when the deformation behaviors of both match (Patent Document) 2). In the method described in Patent Document 2, determination cannot be made unless an actual test is performed.
また、樹脂成形品の衝撃シミュレーションを実施するに際し必要とされる樹脂材料が破壊する歪みの値を、実際の樹脂成形品の歪み速度に合わせた引張試験を行わなくても算出でき、さらに、２回から３回の少ない衝撃シミュレーションをするだけで、破壊に至る実験条件の予想を容易に算出できる技術が開示されている（特許文献３）。特許文献３においては、樹脂の歪み速度に対する特性と、実験条件に依存する衝撃シミュレーション結果を方程式化することを工夫したため、今までほとんど不可能だった精度の高い破壊が発生する実験条件の予測ができるとされている。 In addition, the value of the strain that the resin material required for performing the impact simulation of the resin molded product breaks can be calculated without performing a tensile test in accordance with the strain rate of the actual resin molded product. A technique is disclosed in which the prediction of experimental conditions leading to fracture can be easily calculated by performing only a few impact simulations three to three times (Patent Document 3). In Patent Document 3, since the characteristic of the strain rate of the resin and the impact simulation result depending on the experimental conditions are devised, prediction of the experimental conditions in which high-accuracy fracture that has been almost impossible until now occurs. It is supposed to be possible.
しかしながら、上記特許文献３の衝撃シミュレーションにおける破壊判定方法であっても、判定結果と実験結果が異なる場合があり、さらなる改善が求められている。なお、上記特許文献では、樹脂成形品に加わる歪み速度の経時的変化を考慮していない。 However, even with the fracture determination method in the impact simulation of Patent Document 3, the determination result may be different from the experimental result, and further improvement is required. In the above-mentioned patent document, a change with time of strain rate applied to the resin molded product is not taken into consideration.
本発明は以上のような目的を解決するためになされたものであり、その目的は、樹脂成形品に衝撃が加わる場合の、より正確な衝撃破壊予測方法を提供することにある。 The present invention has been made to solve the above-described object, and an object of the present invention is to provide a more accurate method for predicting impact fracture when an impact is applied to a resin molded product.
本発明者らは、上記課題を解決するために鋭意研究を重ねた。その結果、従来の樹脂成形品の衝撃破壊予測方法で行った予測と、実際の衝撃実験結果と、が異なる場合の多くは、樹脂成形品に衝撃を与えた際に、樹脂成形品に加わる歪み速度の経時的変化を考慮すれば、予測と実験結果とが一致することを見出し、本発明を完成するに至った。より具体的には、本発明は以下のものを提供する。 The inventors of the present invention have made extensive studies to solve the above problems. As a result, in many cases where the prediction made using the conventional method for predicting impact destruction of resin molded products differs from the actual impact test results, distortion applied to the resin molded product when an impact is applied to the resin molded product Considering the change in speed over time, the present inventors have found that the prediction and the experimental result agree with each other and have completed the present invention. More specifically, the present invention provides the following.
（１） シミュレーションによる樹脂成形品の衝撃破壊予測方法であって、該樹脂で作製した樹脂試験片を用い、歪み速度毎における応力−歪み曲線から得られる、破断歪み−歪み速度の関係式導出工程と、前記樹脂成形品の所定の位置に所定の条件で衝撃を与えた際の、前記樹脂成形品における所定の部分の経時的な発生歪みをシミュレーションする第１のシミュレーションと、前記樹脂成形品の所定の位置に所定の条件で衝撃を与えた際の、前記樹脂成形品における所定の部分の経時的な歪み速度をシミュレーションし、前記経時的な歪み速度を、前記関係式に代入することによって、経時的な破断歪みをシミュレーションする第２のシミュレーションと、前記第１及び第２のシミュレーション結果を用いて、経時的に前記発生歪みと前記破断歪みとを比較し、前記発生歪みが前記破断歪みを超える場合に、前記樹脂成形品の破壊を判定する比較判定工程と、を備える衝撃破壊予測方法。 (1) A method for predicting an impact fracture of a resin molded product by simulation, the step of deriving a relational expression of fracture strain-strain rate obtained from a stress-strain curve for each strain rate using a resin test piece made of the resin A first simulation for simulating the strain generated over time in a predetermined portion of the resin molded product when an impact is applied to a predetermined position of the resin molded product under a predetermined condition; By simulating the strain rate over time of a predetermined part in the resin molded article when an impact is applied to a predetermined position under a predetermined condition, and substituting the strain rate over time into the relational expression, Using the second simulation for simulating the fracture strain over time and the results of the first and second simulations, the generated strain and the previous Comparing the break strain, when the generated distortion exceeds the break strain, impact fracture prediction method and a comparison determination step of determining fracture of the resin molded article.
（２） 前記所定の位置が、最大歪み発生部分である（１）に記載の衝撃破壊予測方法。 (2) The impact fracture prediction method according to (1), wherein the predetermined position is a maximum strain occurrence portion.
（３） 前記樹脂試験片が、ウエルド部分を有する試験片であり、前記関係式導出工程が、前記ウエルド部分の破断歪み−歪み速度の関係式導出工程であり、前記所定の位置が、ウエルド部分である（１）に記載の衝撃破壊予測方法。 (3) The resin test piece is a test piece having a weld portion, and the relational expression derivation step is a relational expression derivation process of a fracture strain-strain rate of the weld portion, and the predetermined position is a weld portion. The impact fracture prediction method according to (1).
（４） 前記関係式導出工程が、前記樹脂成形品の樹脂流動方向に対して直行する方向に沿う部分の破断歪み−歪み速度の関係式導出工程であり、前記所定の位置が、前記成形品の樹脂流動方向に対して直行する方向に沿う部分である（１）に記載の衝撃破壊予測方法。 (4) The relational expression derivation step is a relational expression derivation step of a fracture strain-strain rate of a portion along a direction orthogonal to the resin flow direction of the resin molded product, and the predetermined position is the molded product The impact fracture prediction method according to (1), which is a portion along a direction perpendicular to the resin flow direction.
本発明によれば、樹脂成形品に衝撃を与えた際に、樹脂成形品に加わる歪み速度、発生歪み等の経時変化を考慮することで、極めて正確に樹脂成形品の衝撃破壊を予測することができる。 According to the present invention, when an impact is applied to a resin molded product, it is possible to predict the impact fracture of the resin molded product very accurately by taking into account changes over time such as strain rate applied to the resin molded product and generated strain. Can do.
以下、本発明の一実施形態について詳細に説明するが、本発明は、以下の実施形態に何ら限定されるものではなく、本発明の目的の範囲内において、適宜変更を加えて実施することができる。 Hereinafter, an embodiment of the present invention will be described in detail. However, the present invention is not limited to the following embodiment, and may be implemented with appropriate modifications within the scope of the object of the present invention. it can.
＜関係式導出工程＞
関係式導出工程とは、先ず、歪み速度毎における応力−歪み曲線を得た後、応力−歪み曲線から得られる破断点での破断歪みと、破断点における歪み速度との間の関係式（関係方程式）を導出する工程である。具体的な関係式導出の一例については、実施例にて詳述する。
<Relationship derivation process>
The relational expression derivation step is to first obtain a stress-strain curve for each strain rate, and then a relational expression (relationship between the strain at the break point obtained from the stress-strain curve and the strain rate at the break point) This is a step of deriving an equation. An example of deriving a specific relational expression will be described in detail in Examples.
歪み速度毎における応力−歪み曲線を得る際に実験する歪み速度は、樹脂成形品に衝撃が与えられた際に、樹脂成形品に加わる歪み速度程度であることが好ましい。より正確な関係方程式を得ることができるからである。 It is preferable that the strain rate to be tested when obtaining a stress-strain curve for each strain rate is about the strain rate applied to the resin molded product when an impact is applied to the resin molded product. This is because a more accurate relational equation can be obtained.
関係方程式の傾きは樹脂の種類等によって異なる。本発明の衝撃破壊予測方法は、どのような樹脂であっても衝撃破壊を予測することが可能であるが、歪み速度の違いによって破断歪みが経時的に大きく変わるようなものであっても好ましく予測できるのが本発明の衝撃破壊予測方法の特徴である。本発明の衝撃破壊予測方法を用いれば、歪み速度が１０倍になったときに、破断歪みが５割以上減少するものでも好ましく衝撃破壊予測を行うことができる。 The slope of the relational equation varies depending on the type of resin. The impact fracture prediction method of the present invention is capable of predicting impact fracture with any resin, but it is preferable that the fracture strain greatly changes with time due to the difference in strain rate. What can be predicted is the feature of the impact fracture prediction method of the present invention. When the impact fracture prediction method of the present invention is used, even when the strain rate is increased by 10 times, even if the fracture strain is reduced by 50% or more, impact fracture prediction can be preferably performed.
樹脂成形品に含まれる樹脂としては、例えば、ポリエチレン、ポリプロピレン、ポリスチレン、ＡＢＳ、ポリ塩化ビニル、ポリアミド、ポリアセタール、ポリカーボネート、変性ポリフェニレンエーテル、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリフェニレンスルフィド、ポリイミド、ポリアミドイミド、ポリアリレート、ポリサルフォン、ポリエーテルサルフォン、ポリエーテルエーテルケトン、液晶ポリマー、ポリテトラフルオロエチレン、熱可塑性エラストマー等の様々な樹脂又はこれらの樹脂混合物を挙げることができる。さらには、これらの樹脂又は樹脂混合物に充填材、難燃剤、安定剤等の添加剤を添加した樹脂組成物に用いることができる。 Examples of the resin contained in the resin molded product include polyethylene, polypropylene, polystyrene, ABS, polyvinyl chloride, polyamide, polyacetal, polycarbonate, modified polyphenylene ether, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polyimide, polyamideimide, poly Examples include various resins such as arylate, polysulfone, polyethersulfone, polyetheretherketone, liquid crystal polymer, polytetrafluoroethylene, and thermoplastic elastomer, or a mixture of these resins. Furthermore, it can use for the resin composition which added additives, such as a filler, a flame retardant, and a stabilizer, to these resin or resin mixture.
樹脂成形品に衝撃が与えられた際に、樹脂成形品に加えられる歪み速度は一定でなく、経時的に変化している。本発明の衝撃破壊予測方法では、この経時変化を考慮することが本発明の特徴である。即ち、発生歪み、破断歪み、又は歪み速度が経時的に大きく変化するような樹脂を含む樹脂成形品であっても正確に予測できることが本発明の特徴であり、上記のように経時変化が大きくなる樹脂としては例えば、ポリアセタール、ポリブチレンテレフタレート、ポリフェニレンスルフィド等が挙げられる。 When an impact is applied to the resin molded product, the strain rate applied to the resin molded product is not constant and changes over time. In the impact fracture prediction method of the present invention, it is a feature of the present invention that this change with time is taken into account. That is, it is a feature of the present invention that even a resin molded product containing a resin whose generated strain, fracture strain, or strain rate changes greatly with time can be accurately predicted. Examples of the resin include polyacetal, polybutylene terephthalate, polyphenylene sulfide, and the like.
また、ウエルド部、樹脂流動方向と直行する方向、樹脂流動方向に沿う方向等、同じ樹脂成形品であっても、衝撃が与えられる位置によって、破断歪み等は異なる。したがって、これらの強度が異なる部分毎に関係式を求めることで、より正確な樹脂成形品の衝撃破壊予測を行うことができる。特にウエルド部等の樹脂成形品の中でも弱い部分では、衝撃が与えられた際、時間毎にその部分で発生する歪み速度の変化が大きい。さらに、これらの部分では破断歪みが小さい。したがって、従来のような経時的に発生する歪み、歪み速度等を考慮しない方法では、これらの部分の破断を正確に予測することは極めて困難である。本発明の衝撃破壊予測であれば、樹脂成形品に対して衝撃が与えられた際に発生する歪み、歪み速度等の経時的変化も考慮して予測を行うため、このような樹脂成形品中の部分も含めてシミュレーションを行うことができるため、非常に正確に破断、破壊形態を予測することができる。 Even in the same resin molded product, such as a weld part, a direction perpendicular to the resin flow direction, and a direction along the resin flow direction, the fracture strain and the like vary depending on the position where the impact is applied. Therefore, by obtaining a relational expression for each part having different strengths, it is possible to predict the impact fracture of the resin molded product more accurately. In particular, in a weak part of a resin molded product such as a weld part, when an impact is applied, a change in strain rate generated in the part with time is large. Furthermore, the fracture strain is small in these portions. Therefore, it is extremely difficult to accurately predict the breakage of these portions by a conventional method that does not take into account the strain generated at time, the strain rate, and the like. In the case of the impact fracture prediction of the present invention, since prediction is performed in consideration of changes over time such as strain and strain rate generated when an impact is applied to the resin molded product, Since the simulation including this part can be performed, the fracture and fracture mode can be predicted very accurately.
＜第１のシミュレーション＞
第１のシミュレーションとは、樹脂成形品の所定の位置に所定の条件で衝撃を与えた際の樹脂成形品の所定の部分の経時的な発生歪みをシミュレーションする工程である。樹脂成形品に衝撃を与えた際に、樹脂成形品の所定の部分の経時的な発生歪みの変化をシミュレーションすることで、後述する比較判断工程において、正確な衝撃破壊の予測を行うことができる。具体的な第１のシミュレーションの一例については、実施例にて詳述する。
<First simulation>
The first simulation is a step of simulating the strain generated over time of a predetermined portion of the resin molded product when an impact is applied to a predetermined position of the resin molded product under a predetermined condition. When a shock is applied to a resin molded product, the change in strain generated over time in a predetermined portion of the resin molded product is simulated, so that accurate impact fracture prediction can be performed in the comparative judgment process described later. . A specific example of the first simulation will be described in detail in Examples.
上記の第１のシミュレーションを行うためのソフトウエアとしては、例えば、ＬＳ−ＤＹＮＡ、ＲＡＤＩＯＳＳ、ＭＡＳＹＭＯ、ＭＳＣ．ｄｙｔｏｒａｎ、ＰＡＭ−ＣＬＡＳＨ等が挙げられるが、本発明の目的に適うものであれば特に限定されず、いかなるソフトウエアも用いることができる。 Examples of software for performing the first simulation include LS-DYNA, RADIUS, MASYMO, MSC. dytoran, PAM-CLASH, etc., but any software can be used without particular limitation as long as it meets the object of the present invention.
「衝撃破壊」とは、荷重が継続的、繰り返し負荷されて破壊する疲労破壊等とは異なり、衝撃が与えられた後、およそ１秒以内に破壊するものをいう。「衝撃」とは、樹脂成形品に対して急激に加わる力のことである。衝撃は一軸衝撃でも多軸衝撃でもよいが、本発明の効果が顕著に現れるのは多軸衝撃である。本発明の衝撃破壊予測方法であれば、様々な方向に力が加わったとしても、複数の関係方程式を用いることで対応することができるからである。 “Impact failure” refers to a material that breaks within about 1 second after an impact is applied, unlike a fatigue failure in which a load is continuously and repeatedly loaded to break. “Impact” is a force that is suddenly applied to the resin molded product. Although the impact may be a uniaxial impact or a multiaxial impact, it is the multiaxial impact that the effect of the present invention appears remarkably. This is because the impact fracture prediction method according to the present invention can cope with a force applied in various directions by using a plurality of relational equations.
「所定の位置」とは、実際に樹脂成形品に対して、衝撃がかかる位置である。本発明は、樹脂成形品に衝撃を与えた際に破壊するか否かを予測する方法であるから、予測の段階でも、実際に樹脂成形品に対して衝撃が与えられる位置と同じ位置で、シミュレーションを行う必要があるからである。 The “predetermined position” is a position where an impact is actually applied to the resin molded product. Since the present invention is a method for predicting whether or not the resin molded product is destroyed when an impact is applied, even at the prediction stage, at the same position as the position where the impact is actually applied to the resin molded product, This is because it is necessary to perform a simulation.
「所定の条件」とは、実際に樹脂成形品に対して、衝撃がかかる時の衝撃の条件であり、具体的な条件としては、衝突速度、落下高さ、衝突エネルギー等を挙げることができるが、数値化できるものであれば特に限定されない。本発明の衝撃破壊予測方法は、様々な条件の衝撃に対して、樹脂成形品が破壊するか否かの予測を正確に行うことができるが、一瞬で、樹脂成形品が破壊してしまうような強い衝撃条件では、発生歪み、歪み速度等の経時的変化を考慮する必要はあまりない。本発明の効果がより顕著に現れる「所定の条件」、即ち発生歪み、歪み速度等の経時的な変化を考慮しなければ、樹脂成形品に対して衝撃が与えられた際に破壊するか否かを正確に予測することができないような、所定の条件での衝撃とは、樹脂成形品に対して衝撃を与えた後１×１０−４秒から１秒以内に樹脂成形品が破壊してしまう条件である。 “Predetermined conditions” are the conditions of impact when an impact is actually applied to a resin molded product, and specific conditions can include impact speed, drop height, impact energy, and the like. However, there is no particular limitation as long as it can be quantified. The impact fracture prediction method of the present invention can accurately predict whether or not a resin molded product will be destroyed in response to impacts of various conditions. However, the resin molded product may be destroyed in an instant. Under strong impact conditions, it is not necessary to take into account changes over time such as generated strain and strain rate. If the “predetermined conditions” in which the effect of the present invention appears more prominently, that is, changes over time such as generated strain and strain rate, are not taken into consideration, whether or not the resin molded product is destroyed when an impact is applied. The impact under a predetermined condition that cannot be accurately predicted is that the resin molded product is destroyed within 1 second from 1 × 10 −4 seconds after the impact is applied to the resin molded product. This is a condition.
「樹脂成形品の所定の部分」とは、樹脂成形品において破壊するか否かを予測したい部分であれば、その場所は特に限定されない。しかし、本発明は樹脂成形品に対して衝撃が与えられた際に破壊するか否かを正確に予測できる方法である。上記の通り同じ樹脂成形品であっても、樹脂成形品内の位置によって破断に至るために必要な歪み速度は異なる。したがって、所定の関係方程式を用いる部分毎に、最大歪み発生部分の経時的な発生歪みをシミュレーションすることで、樹脂成形品に対して、所定の条件の衝撃を与えた場合に、樹脂成形品が破壊するか否かを正確に予測することができる。これらの部分の中で最も歪む部分が破壊しなければ、樹脂成形品も破壊しないからである。 The “predetermined portion of the resin molded product” is not particularly limited as long as it is a portion where it is desired to predict whether or not the resin molded product will be destroyed. However, the present invention is a method that can accurately predict whether or not a resin molded product will be destroyed when an impact is applied. Even if it is the same resin molded product as described above, the strain rate required to reach breakage differs depending on the position in the resin molded product. Therefore, by simulating the strain generated over time of the maximum strain generation part for each part using a predetermined relational equation, when the resin molded product is given an impact under a predetermined condition, the resin molded product Whether or not to destroy can be accurately predicted. This is because if the most distorted portion of these portions is not destroyed, the resin molded product is not destroyed.
「経時的な発生歪み」とは、樹脂成形品の所定の部分の発生歪みの時間変化である。経時的なシミュレーションを行うことで、本発明の効果である高い正確性を持つ衝撃破壊予測を実現する。従来の方法では、樹脂が衝撃を受けた際の歪み速度を一定と考えるため、発生歪みも一定、破断歪みも一定として考える。しかし、本発明では下記の通り、樹脂成形品が衝撃を受けた際の歪み速度、発生歪み、破断歪みの時間変化を考慮するため、極めて正確に樹脂成形品の衝撃破壊予測を行うことができる。 “Generated strain over time” is a time change of generated strain of a predetermined portion of a resin molded product. By performing the simulation over time, the impact fracture prediction with high accuracy which is the effect of the present invention is realized. In the conventional method, since the strain rate when the resin is impacted is considered to be constant, the generated strain is also assumed to be constant and the fracture strain is also assumed to be constant. However, in the present invention, as described below, since the time change of the strain rate, the generated strain, and the fracture strain when the resin molded product receives an impact is taken into account, the impact fracture prediction of the resin molded product can be performed very accurately. .
樹脂成形品では、その材料が樹脂であることによって、樹脂成形品の衝撃の際に受ける歪み速度が経時的に大きく異なる。衝撃の際に受ける歪み速度が経時的に変化すると、破断歪みも経時的に変化する。破断歪みが経時的に変化し、発生歪みが経時的に変化することで、この破断歪み又は発生歪みの経時的変化が大きい時間範囲では、発生歪みの値が破断歪みより大きくなりやすい。発生歪みが破断歪みを超えることは樹脂成形品が破断することを意味する。したがって、本発明の衝撃破壊予測方法は、上記のような発生歪みと破断歪みとの経時的な変化を考慮することで、より正確に樹脂成形品が衝撃を受けた際に破壊するか否かを判定することができる。 In the resin molded product, since the material thereof is a resin, the strain rate applied upon impact of the resin molded product varies greatly with time. When the strain rate applied during impact changes with time, the fracture strain also changes with time. Since the breaking strain changes with time and the generated strain changes with time, the value of the generated strain is likely to be larger than the breaking strain in a time range in which the breaking strain or the change with time of the generated strain is large. When the generated strain exceeds the breaking strain, it means that the resin molded product is broken. Therefore, the impact fracture prediction method of the present invention takes into account the change over time between the generated strain and the fracture strain as described above, so that whether or not the resin molded product breaks more accurately when impacted. Can be determined.
樹脂成形品に衝撃を与えた際に歪み速度が経時的に変化すると、その変化とともに発生歪みが短い時間で大きく変化するような、発生歪みが歪み速度の影響を受けやすい性質を持つ樹脂からなる樹脂成形品に、本発明の衝撃破壊予測方法は好ましく用いることができる。歪み速度の変化により、発生歪みが大きく変化すれば、発生歪みが大きくなったところで、発生歪みの値が破断歪みの値を超えやすいからである。 When the strain rate changes over time when an impact is applied to the resin molded product, the generated strain is made of a resin having a property that the generated strain is easily affected by the strain rate so that the generated strain changes greatly in a short time. The impact fracture prediction method of the present invention can be preferably used for a resin molded product. This is because if the generated strain changes greatly due to the change in strain rate, the generated strain value tends to exceed the fracture strain value when the generated strain increases.
「発生歪みが短い時間で大きく変化」とは、従来での静的解析では判定できない領域であり、経時的変化の中に０．０１秒当たり１％以上発生歪みが変化するような変化を含むものをいう。本発明の衝撃破壊予測方法であれば、このように発生歪みが大きく変化する樹脂成形品であっても、正確に衝撃破壊予測を行うことができる。 “Generated strain changes greatly in a short time” is an area that cannot be determined by conventional static analysis, and includes changes in which the generated strain changes by 1% or more per 0.01 seconds. Say things. With the impact fracture prediction method of the present invention, it is possible to accurately perform impact fracture prediction even for a resin molded product in which the generated strain greatly changes.
＜第２シミュレーション＞
第２のシミュレーションとは、樹脂成形品の所定の位置に所定の条件で衝撃を与えた際の樹脂成形品の所定の部分の経時的な歪み速度をシミュレーションし、その経時的な歪み速度を、上述の関係方程式に代入することによって、経時的な破断歪みをシミュレーションする工程である。樹脂成形品に衝撃を与えた際に、樹脂成形品の所定の部分の経時的な破断歪みの変化をシミュレーションすることで、後述する比較判断工程において、正確な衝撃破壊の予測を行うことができる。なお、具体的な第２のシミュレーションの一例については、実施例にて詳述する。
<Second simulation>
The second simulation is to simulate the strain rate over time of a predetermined part of the resin molded product when an impact is applied to a predetermined position of the resin molded product under a predetermined condition. This is a process of simulating fracture strain over time by substituting into the above relational equation. By simulating the change in fracture strain over time of a predetermined part of the resin molded product when an impact is applied to the resin molded product, it is possible to accurately predict the impact fracture in the comparative judgment process described later. . A specific example of the second simulation will be described in detail in Examples.
シミュレーションに使用可能なソフトウエア、「所定の位置」、「所定の条件」の用語については第１シミュレーションで説明したものと同様である。 Software that can be used for the simulation, and the terms “predetermined position” and “predetermined condition” are the same as those described in the first simulation.
「樹脂成形品の所定の部分」とは、樹脂成形品において破壊するか否かを予測したい部分であれば、その場所は特に限定されない。しかし、本発明は樹脂成形品に対して衝撃が与えられた際に破壊するか否かを正確に予測できる方法である。上記の通り同じ樹脂成形品であっても、樹脂成形品内の位置によって、所定の歪み速度での破断歪みは異なる。したがって、所定の関係方程式を用いる部分毎に、最大歪み発生部分の経時的な破断歪みをシミュレーションすることで、樹脂成形品に対して、所定の条件の衝撃を与えた場合に、樹脂成形品が破壊するか否かを正確に予測することができる。これらの部分の中で最も歪む部分が破壊しなければ、樹脂成形品も破壊しないからである。 The “predetermined portion of the resin molded product” is not particularly limited as long as it is a portion where it is desired to predict whether or not the resin molded product will be destroyed. However, the present invention is a method that can accurately predict whether or not a resin molded product will be destroyed when an impact is applied. Even if it is the same resin molded product as described above, the breaking strain at a predetermined strain rate differs depending on the position in the resin molded product. Therefore, for each part using a predetermined relational equation, by simulating the rupture strain over time of the maximum strain occurrence part, the resin molded product is Whether or not to destroy can be accurately predicted. This is because if the most distorted portion of these portions is not destroyed, the resin molded product is not destroyed.
「経時的な破断歪み」とは、樹脂成形品の所定の部分の破断歪みの経時変化である。経時的なシミュレーションを行うことで、本発明の効果である高い正確性を持つ衝撃破壊予測を実現する。従来の方法では、樹脂が衝撃を受けた際の歪み速度を一定と考えるため、発生歪みも一定、破断歪みも一定として考える。しかし、本発明では下記の通り、樹脂成形品が衝撃を受けた際の歪み速度、発生歪み、破断歪みの時間変化を考慮するため、極めて正確に樹脂成形品の衝撃破壊予測を行うことができる。 The “breaking strain with time” is a change with time of the breaking strain of a predetermined part of the resin molded product. By performing the simulation over time, the impact fracture prediction with high accuracy which is the effect of the present invention is realized. In the conventional method, since the strain rate when the resin is impacted is considered to be constant, the generated strain is also assumed to be constant and the fracture strain is also assumed to be constant. However, in the present invention, as described below, since the time change of the strain rate, the generated strain, and the fracture strain when the resin molded product receives an impact is taken into account, the impact fracture prediction of the resin molded product can be performed very accurately. .
樹脂成形品に衝撃を与えた際に歪み速度が経時的に変化すると、その変化とともに破断歪みが大きく変化するような、破断歪みが歪み速度の影響を受けやすい性質を持つ樹脂からなる樹脂成形品に、本発明の衝撃破壊予測方法は好ましく用いることができる。歪み速度の経時変化により、破断歪みが短い時間で大きく変化すれば、破断歪みが急激に小さくなったところで、破断歪みの値は、発生歪みの値を下回りやすいからである。 A resin molded product made of a resin that has a property in which the breaking strain is easily affected by the strain rate, such that if the strain rate changes over time when an impact is applied to the resin molded product, the breaking strain changes with the change. In addition, the impact fracture prediction method of the present invention can be preferably used. This is because if the breaking strain changes greatly in a short time due to the change in strain rate over time, the value of the breaking strain tends to be lower than the value of the generated strain when the breaking strain rapidly decreases.
「破断歪みが短い時間で大きく変化」とは、経時的変化の中に１秒当たり１００％以上破断歪みが変化するような変化を含むものをいう。本発明の衝撃破壊予測方法であれば、このように破断歪みが大きく変化する樹脂成形品であっても正確に衝撃破壊予測を行うことができる。 The phrase “breaking strain greatly changes in a short time” means that the change over time includes a change in which the breaking strain changes by 100% or more per second. With the impact fracture prediction method of the present invention, it is possible to accurately perform impact fracture prediction even for a resin molded product in which the fracture strain changes greatly.
本発明は、破断歪みの値と発生歪みの値とが、近い値で経時的に変化していくような場合にも、衝撃破壊の予測を正確に行うことができることが特徴の一つである。破断歪みと発生歪みとが、近い値で経時的に変化していけば、破断歪みが小さくなり同時に発生歪みが大きくなった時点で、これらが小さな変化であったとしても破断しやすいからである。このような破断は、樹脂が衝撃を受けた際の歪み速度を一定と考え、発生歪みも一定、破断歪みも一定として考える従来の方法では、破断を正確に予測することは難しいが、本発明の衝撃破壊予測方法は、発生歪み、破断歪み等の経時的変化も考慮して、衝撃破壊予測を行うため、正確に予測することができる。 One feature of the present invention is that it is possible to accurately predict impact fracture even when the value of fracture strain and the value of generated strain change over time at close values. . This is because if the breaking strain and the generated strain change over time at close values, the fracture strain becomes small and at the same time when the generated strain increases, it is easy to break even if these are small changes. . It is difficult to accurately predict the rupture in the conventional method in which the strain rate when the resin is subjected to an impact is assumed to be constant, the generated strain is constant, and the rupture strain is also constant. This impact fracture prediction method performs impact fracture prediction in consideration of changes over time such as generated strain and fracture strain, so that it can be accurately predicted.
「近い値で経時的に変化」とは、衝撃後１秒以内における破断歪みの最小値と発生歪みの最大値との差が１０％以下のものをいう。このような場合であっても上記の通り本発明の衝撃破壊予測方法であれば正確に予測することができる。 “Change over time at a close value” means that the difference between the minimum value of fracture strain and the maximum value of strain generated within 1 second after impact is 10% or less. Even in such a case, as described above, the impact fracture prediction method of the present invention can be accurately predicted.
樹脂成形品のウエルド部は、他の部分と比較して破断歪みが小さいので、破断歪みの値と発生歪みの値とが、近い値で経時的に変化していく傾向にある。したがって、ウエルド部を有する樹脂成形品は、従来の方法では、正確に衝撃破壊予測を行うことは難しいが、本発明の方法を用いれば正確に予測を行うことができる。 Since the welded portion of the resin molded product has a smaller breaking strain than other portions, the value of the breaking strain and the value of the generated strain tend to change over time at a close value. Therefore, it is difficult to accurately predict impact fracture of a resin molded product having a weld part by the conventional method, but it is possible to accurately predict by using the method of the present invention.
また、樹脂成形品の樹脂流動方向に対して直行する方向に沿う部分も、ウエルド部と同様に、他の部分と比較して破断歪みが小さいが、本発明の衝撃破壊予測方法であれば正確に予測することができる。 In addition, the portion along the direction perpendicular to the resin flow direction of the resin molded product also has a smaller fracture strain than the other portions, like the weld portion. However, the impact fracture prediction method of the present invention is accurate. Can be predicted.
＜比較判定工程＞
比較判定工程とは、第１及び第２のシミュレーション結果を用いて、経時的に発生歪みと破断歪みと、を比較し、発生歪みが破断歪みを超える場合に、樹脂成形品の破壊を判定する工程である。本発明の衝撃破壊予測方法は、発生歪みの経時的な変化と破断歪みの経時的な変化とを比較して予測するため、樹脂成形品が破断するか否か、破断する場合にはいつ破断するのかを正確に予測することができる。なお、具体的な比較判定工程についての一例は、実施例にて詳述する。
<Comparison judgment process>
The comparison determination step uses the first and second simulation results to compare the generated strain with the rupture strain over time, and when the generated strain exceeds the rupture strain, determine the destruction of the resin molded product. It is a process. The impact fracture prediction method of the present invention predicts by comparing the change over time in the generated strain and the change over time in the fracture strain, so whether or not the resin molded product breaks, It is possible to predict exactly what will be done. In addition, an example about a specific comparison determination process is explained in full detail in an Example.
本発明は、発生歪みの経時的な変化と破断歪みの経時的な変化とを比較して、発生歪みと破断歪みとが、最初に交わったときに樹脂成形品は破断することを判定する。本発明の衝撃破壊予測方法であれば、破断に至るまでの破断歪みと発生歪みと、を正確にシミュレーションでき、ウエルド部、樹脂成形品の樹脂流動方向に沿う部分、樹脂成形品の樹脂流動方向に対して直行する方向に沿う部分等の樹脂成形品の中で強度の異なる部分も考慮することが可能なので、樹脂成形品が破壊するまでに吸収するエネルギー量を正確に計算可能なため、樹脂成形品の破断形態も正確に予測することができる。 The present invention compares the change over time of the generated strain with the change over time of the breaking strain, and determines that the resin molded product breaks when the generated strain and the breaking strain first intersect. With the method for predicting impact fracture according to the present invention, it is possible to accurately simulate fracture strain and generation strain until rupture, weld portion, portion along the resin flow direction of the resin molded product, resin flow direction of the resin molded product. Since it is possible to consider parts with different strengths in the resin molded product such as the part along the direction perpendicular to the resin, it is possible to accurately calculate the amount of energy absorbed until the resin molded product breaks down. The fracture form of the molded product can also be accurately predicted.
以下に、実施例を挙げて本発明をさらに詳細に説明するが、本発明はこれらの実施例により限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
＜実施例１＞
［関係式導出工程］
ポリアセタール（ポリプラスチックス社製、「ジュラコン（登録商標）Ｍ９０−４４」）からなる樹脂成形品（長さ１７０ｍｍ×幅１０ｍｍ×厚さ４ｍｍ）、引張試験機（鷺宮製作所製、「計装化衝撃試験機ＴＳ−４０００」）を用いて、歪み速度毎の応力−歪み曲線を得た。得られた歪み速度毎の応力−歪み曲線を図１に示した。図１の応力−歪み曲線から歪み速度と破壊歪みの関係方程式を求めた。関係方程式は図２に示した。また、関係方程式以外の樹脂材料の物性は、弾性率４０００ＭＰａ、ポアソン比０．３５、密度１．４１×１０−９ｔｏｎ／ｍｍ３である。
<Example 1>
[Relationship derivation process]
Resin molded product (length 170mm x width 10mm x thickness 4mm) made of polyacetal (polyplastics, "Duracon (registered trademark) M90-44"), tensile tester (Miyanomiya Seisakusho, "instrumentation impact" Using a tester TS-4000 "), stress-strain curves for each strain rate were obtained. The obtained stress-strain curve for each strain rate is shown in FIG. A relational equation between the strain rate and the fracture strain was obtained from the stress-strain curve of FIG. The relational equation is shown in FIG. The physical properties of the resin material other than the relational equation are an elastic modulus of 4000 MPa, a Poisson's ratio of 0.35, and a density of 1.41 × 10 −9 ton / mm 3 .
［第１のシミュレーション］
図３に示すように、両側に錘（幅３０ｍｍ×高さ３０ｍｍ×厚み２０ｍｍ）を固定した曲げ試験片（長さ１００ｍｍ×幅６ｍｍ×厚さ４ｍｍ）を３ｍの高さから、白抜き矢印の方向に落下させる条件で、突起物（以後、ストライカー）に、樹脂成形品の中央部を衝突させた際の破断の有無及び時間について判定した。試験片材料はポリアセタールを用い、ソフトウエアはＬＳ−ＤＹＮＡ（ＬｉｖｅｒｍｏｒｅＳｏｆｔｗａｒｅＴｅｃｈｎｏｌｏｇｙ社製）を用いた。
[First simulation]
As shown in FIG. 3, a bending test piece (
具体的には、先ず、図３に示すように衝撃解析を行い、最も発生歪みの大きい箇所を求めた。最も発生歪みが大きいのは、樹脂成形品の中央部であった。樹脂成形品の中央部について、経時的な発生歪みをシミュレーションした。第１のシミュレーションの結果を図５中に点線で示した。 Specifically, first, an impact analysis was performed as shown in FIG. The greatest distortion occurred in the central part of the resin molded product. With respect to the central portion of the resin molded product, the strain generated over time was simulated. The result of the first simulation is indicated by a dotted line in FIG.
［第２のシミュレーション］
次いで、上記最大歪み発生部分の経時的な歪み速度をシミュレーションした。得られた結果を図４に示した。このシミュレーションにより得られた経時的な歪み速度を図２に示した関係方程式に代入し、経時的な破断歪みをシミュレーションした。この第２のシミュレーションの結果を図５実線で示した。
[Second simulation]
Next, the temporal strain rate of the maximum strain generation portion was simulated. The obtained results are shown in FIG. The temporal strain rate obtained by this simulation was substituted into the relational equation shown in FIG. 2, and the temporal fracture strain was simulated. The result of this second simulation is shown by the solid line in FIG.
［比較判定工程］
上記第１及び第２のシミュレーション結果を用いて、経時的に上記発生歪みと上記破断歪みとを比較し、上記発生歪みが上記破断歪みを超える場合に、上記樹脂成形品の破壊を判定した。判定結果を以下に示した。
[Comparison judgment process]
Using the first and second simulation results, the generated strain was compared with the breaking strain over time, and when the generated strain exceeded the breaking strain, the destruction of the resin molded product was determined. The determination results are shown below.
［判定結果］
衝撃から０．０００７５秒で破断することが予測され、実際にもこの点で破断することが確認できた。図４から明らかなように、破断するのは、歪み速度の経時的変化の大きい時間領域である。したがって、本発明のような、歪み速度、発生歪み、破断歪みについての経時的変化を考慮した方法でなければ、正確な樹脂成形品の衝撃破壊予測を行うことができないことが確認された。
[judgment result]
It was predicted to break at 0.00075 seconds from the impact, and it was confirmed that it actually breaks at this point. As apparent from FIG. 4, the fracture occurs in a time region where the strain rate changes with time. Therefore, it was confirmed that the impact fracture prediction of the resin molded product could not be performed accurately unless the method considering the change with time of the strain rate, the generated strain, and the fracture strain as in the present invention was taken into consideration.
＜実施例２＞
ポリアセタールからなる樹脂成形品がウエルド部を有する以外は実施例１の関係式導出工程と同様の方法で、ウエルド部及びウエルドでない部分の関係方程式を求めた。これらの関係方程式を図６に示した。
<Example 2>
A relational equation between the weld part and the non-weld part was obtained in the same manner as in the relational expression derivation step of Example 1 except that the resin molded product made of polyacetal had a weld part. These relational equations are shown in FIG.
図７（ａ）に示すように、両側に穴のある板状の部品（以後、スナップフィット）を突起物のある相手部品（剛体）に５０ｍｍ／ｓｅｃの速度で、突起部が穴まで到達し、スナップフィットが組付けられる状態に至る条件にて破断有無及び時間について判定した。 As shown in FIG. 7 (a), a plate-like part having holes on both sides (hereinafter referred to as a snap fit) is made to a mating part with a protrusion (rigid body) at a speed of 50 mm / sec. Then, the presence / absence of breakage and the time were determined under the conditions leading to the state where the snap fit was assembled.
ウエルド部（図７（ｂ）にＢと示した部分）とそれ以外の部分の最大歪み発生箇所（図７（ａ）にＡと示した部分）とに分けて行った以外は、実施例１と同様に第１のシミュレーション、第２のシミュレーション、比較判定工程を行った。第１のシミュレーションの結果である経時的な発生歪みを図９に示し、経時的な歪み速度のシミュレーションを図８に示し、第２のシミュレーションの結果である経時的な破断歪みのシミュレーション結果を図９に示した。 Example 1 except that the weld portion (the portion indicated by B in FIG. 7B) and the maximum distortion occurrence portion (the portion indicated by A in FIG. 7A) of the other portions were separated. The first simulation, the second simulation, and the comparison determination step were performed in the same manner as described above. FIG. 9 shows the strain generated over time that is the result of the first simulation, FIG. 8 shows the simulation of the strain rate over time, and FIG. 8 shows the simulation result of the fracture strain over time that is the result of the second simulation. 9 shows.
最大歪み発生箇所では、発生歪みが破断歪みを超えることはなく、ウエルド部以外の部分は破断しないことが予測され、実際にも破断しないことが確認できた。一方ウエルド部では、衝撃後およそ０．４秒で破断することが予測され、実際にもこの点で破断することが確認できた。 At the location where the maximum strain was generated, the generated strain did not exceed the breaking strain, and it was predicted that portions other than the weld portion would not break, and it was confirmed that the portion would not actually break. On the other hand, the weld portion was predicted to break approximately 0.4 seconds after impact, and it was actually confirmed that the break occurred at this point.
図８から明らかなように、衝撃後０．４秒付近は歪み速度が経時的に大きく変化している時間領域である。したがって、本発明のような、歪み速度、発生歪み、破断歪みについての経時的変化を考慮した方法でなければ、正確な樹脂成形品の衝撃破壊予測を行うことができないことが確認された。 As is apparent from FIG. 8, the vicinity of 0.4 seconds after the impact is a time region in which the strain rate changes greatly with time. Therefore, it was confirmed that the impact fracture prediction of the resin molded product could not be performed accurately unless the method considering the change with time of the strain rate, the generated strain, and the fracture strain as in the present invention was taken into consideration.
Claims (4)
該樹脂で作製した樹脂試験片を用い、歪み速度毎における応力−歪み曲線から得られる、破断歪み−歪み速度の関係式導出工程と、
前記樹脂成形品の所定の位置に所定の条件で衝撃を与えた際の、前記樹脂成形品における所定の部分の経時的な発生歪みをシミュレーションする第１のシミュレーションと、
前記樹脂成形品の所定の位置に所定の条件で衝撃を与えた際の、前記樹脂成形品における所定の部分の経時的な歪み速度をシミュレーションし、前記経時的な歪み速度を、前記関係式に代入することによって、経時的な破断歪みをシミュレーションする第２のシミュレーションと、
前記第１及び第２のシミュレーション結果を用いて、経時的に前記発生歪みと前記破断歪みとを比較し、前記発生歪みが前記破断歪みを超える場合に、前記樹脂成形品の破壊を判定する比較判定工程と、を備える衝撃破壊予測方法。 A method of predicting impact fracture of a resin molded product by simulation,
Using a resin test piece made of the resin, a step of deriving a relational expression of breaking strain-strain rate obtained from a stress-strain curve for each strain rate;
A first simulation for simulating the strain generated over time of a predetermined portion of the resin molded product when an impact is applied to a predetermined position of the resin molded product under a predetermined condition;
Simulates the strain rate over time of a predetermined portion of the resin molded product when an impact is applied to a predetermined position of the resin molded product under a predetermined condition, and the strain rate over time is expressed by the relational expression. A second simulation that simulates the fracture strain over time by substituting;
Using the first and second simulation results, a comparison is made between the generated strain and the fracture strain over time, and when the generated strain exceeds the fracture strain, the resin molded product is determined to be destroyed. An impact fracture prediction method comprising: a determination step.
前記関係式導出工程が、前記ウエルド部分の破断歪み−歪み速度の関係式導出工程であり、
前記所定の位置が、ウエルド部分である請求項１に記載の衝撃破壊予測方法。 The resin test piece is a test piece having a weld portion;
The relational expression derivation step is a relational expression derivation step of fracture strain-strain rate of the weld part,
The impact fracture prediction method according to claim 1, wherein the predetermined position is a weld portion.
前記所定の位置が、前記樹脂成形品の樹脂流動方向に対して直行する方向に沿う部分である請求項１に記載の衝撃破壊予測方法。 The relational expression derivation step is a relational expression derivation step of the breaking strain-strain rate of the portion along the direction orthogonal to the resin flow direction of the resin molded product,
The method according to claim 1, wherein the predetermined position is a portion along a direction orthogonal to a resin flow direction of the resin molded product.
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