| 号数 | ばね論文集 57 号（ 2012 年） |
| ページ数 | pp.17-24 |
| 種類 | 論文 |
| 論文名 | ばね鋼の遅れ破壊き裂進展の下限界応力拡大係数と遅れ破壊防止設計法 |
| Title | Threshold Stress Intensity Factor of Crack Propagation of Delayed Fracture for Spring Steel and Design Method for Preventing Delayed Fracture |
| 著者 | 後藤由利香1)，辻松栄治2)，丹下彰1) |
| Author | Yurika GOTO1), Eiji TSUJIMATSU2) and Akira TANGE1) |
| 抄録 | 近年，地球環境保全として，自動車用懸架ばねに対する軽量化ニーズが高まっており，ばねの高強度化がますます求められている．しかし，ばねの高強度化は遅れ破壊を誘発するもので，遅れ破壊を考慮した設計や防止方法の開発が緊急の課題となっている． そこで，ばねの遅れ破壊防止設計のために，破壊力学パラメータ，ばね鋼の遅れ破壊き裂進展の下限界応力拡大係数（以後KIHEとする），のデータベースを提供することとした．具体的には，WOL試験により，板ばね鋼として多用されるSUP9A，SUP10，SUP11，51CrMoV4におけるKIHEと硬さの関係を求めた．また，この有用性については，半円状人工切欠きを有する板状試験片を4点曲げ遅れ破壊試験することにより確認した．さらに，遅れ破壊防止技術として，ショットピーニングの遅れ破壊防止効果についても明らかにし，残留応力を考慮した遅れ破壊防止設計についても検討を行った．得られた遅れ破壊防止条件は，板ばねのみでなく，ばね鋼の遅れ破壊全般に適用可能である． " |
| Abstract | In recent years, there has been a growing need for weight reduction of automotive suspension springs for the purpose of global environment protection, and with this, high-strength springs have been increasingly required. However, delayed fracture is induced when springs become highly-strengthened. Therefore development of a design method considering delayed fracture and of prevention techniques is an urgent issue. In order to realize the design method for springs that prevents elayed fracture, this report provides the database of fracture mechanics parameters, i.e., threshold stress intensity factors of hydrogen embrittlement for spring steel (hereafter referred to as KIHE). To be specific, the relationship between KIHE and hardness of SUP9A, SUP10, SUP11 and 51CrMoV4 steels, which are frequently used for leaf springs, was examined by the Wedge Opening Loading (WOL) testing. To confirm the usefulness of the relationship, the delayed fracture testing by four-point bending was conducted on test specimens with a semicircular notch. Moreover, the effectiveness of shot peening to prevent delayed fracture, as a prevention technique, was also demonstrated, and the design method considering residual streess to prevent delayed fracture was studied as well. The acquired parameters for the prevention of delayed fracture can be applied not only to leaf spring steels, but also to spring steels in general. |
| 著者の所属 | 1）日本発条株式会社 2）株式会社スミハツ |
| Belonging | 1）NHK SPRING CO., LTD 2）SUMIHATSU CO., LTD |
| Key Words | Leaf spring, Hydrogen embrittlement, Threshold stress intensity factor, Residual stress |