【博士論文】学術データベース

博士論文 / Adhesive Strength Evaluation Method Focusing on the Intensity of Singular Stress Field to Minimize Bend Effect for Single Lap Joint 特異応力場の強さに注目した接着強度評価法と単純重ね合わせ継手の曲がりの影響の解消

著者

書誌事項

タイトル

Adhesive Strength Evaluation Method Focusing on the Intensity of Singular Stress Field to Minimize Bend Effect for Single Lap Joint

タイトル別名

特異応力場の強さに注目した接着強度評価法と単純重ね合わせ継手の曲がりの影響の解消

著者名

Li Rong

学位授与大学

九州工業大学 (大学ID:0071) (CAT機関ID:KI000844)

取得学位

博士(工学)

学位授与番号

甲工第432号

学位授与年月日

2017-03-24

注記・抄録

Adhesively bonded joints are economical, practical and easy to make; thus they have been widely used in a variety of industries. The testing method for the adhesive strength of lap joint is standardized by Japanese Industrial Standards (JIS). However, the debonding strength is affected by the specimen dimension and difficult to be applied to other geometries. Compared with double lap joint, single lap joint can be used conveniently. However, the experimental results show that the strength of double lap joint is nearly twice larger than the one of single lap joint. Therefore, it is necessary to find a suitable evaluation method for lap joint testing. The single lap joint testing should be done under pure shear loading, but pure shear testing is difficult to be realized in the experiment. Due to the bend deformation of single lap joint during testing, the peeling force is applied to the adhesive region. Then the intensity of singular stress field (ISSF) at the interface corner is affected by the peeling force due to the deformation. This research concentrated on the adhesive strength evaluation method to minimize the ISSF for single lap joint. This thesis is composed of total 7 chapters and organized as follows. Chapter 1 gives the introduction of the applications of adhesive bonded structures in numerous industrial sectors, such as integrated circuit (IC) technology, automobile industry and aircraft industry. The application and importance of adhesively bonded structure were investigated. Then the research purpose of this thesis is introduced, focusing on the evaluation method to minimize the ISSF for single lap joint. In order to clarify this research clearly, the studies of the research on the singularity in the adhesively bonded joints are reviewed in chapter 2. It is found that there are no results about the convenient evaluation method to minimize the ISSF for single lap joint. Since the ISSF of butt joint can be obtained conveniently by using the analysis method presented in previous studies, the debonding strength of butt joint is investigated in chapter 3. First, a homogeneous and flawless elastic adhesive layer is assumed to evaluate the butt joint strength for carbon steel/epoxy resin, aluminum/araldite, and brass/solder. It is found that the adhesive strength is always expressed as the critical ISSF. Next, a small fictitious interface edge crack is assumed at the adhesive layer to consider the singular stress field including crack. Then the debonding strength is also found to be controlled by the critical ISSF of the fictitious crack. A suitable dimension of the fictitious crack is discussed to predict the strength for adhesive joints accurately and conveniently. In chapter 4, a convenient analysis method for the ISSF of lap joint is proposed. Since the singular stress field of lap joint is complex than butt joint, the method in chapter 3 cannot be applied to the lap joint analysis directly. The same FEM mesh pattern is applied to unknown problems and reference problems. Then, it is found that the ISSF is obtained accurately by focusing on the FEM stress at the adhesive corner. Although the singular stress is controlled by two factors for lap joints, it can be expressed almost in the same way as butt joint even if the adhesive geometries are widely changed. Therefore, the ISSF of lap joints as well as butt joints can be obtained conveniently by using the analysis method presented in this chapter. The usefulness of the present solution is verified by comparing with the results of the conventional method. In chapter 5, the debonding criterion of single lap joint is investigated in terms of the critical ISSF Kσc by using the analysis method presented in chapter 4. In this chapter, the value of Kσc is investigated based on the experimental results. The results show that the adhesive strength can be evaluated as c Kσc =const when the debonding fracture occurs (except for the specimen with very short adhesive length). Chapter 6 shows the adhesive strength evaluation method to minimize bend effect for single lap joint. Here, the evaluation method is investigated in terms of the ISSF appearing at the interface corner. The results show that the ISSF decreases with increasing the adherend thickness. The minimum ISSF can be obtained when the adherend thickness 1 t is large enough, and the deformation angle at the interface corner is smallest when adherend thickness 1 t is large enough. In addition, the equivalent conditions of strength for single lap joint and double lap joint are investigated in terms of the ISSF. It is found that the strength of single lap joint with 1 t =7mm is nearly equal to that of double lap joint with 1 t =1.5mm (JIS) since the ISSFs of single lap joint and double lap joint are nearly the same. For the same reason, the strength of single lap joint is nearly equal to that of double lap joint when 1 t ≥25mm. In the last chapter of this thesis, chapter 7, main conclusions of this study are summarized.

九州工業大学博士学位論文 学位記番号:工博甲第432号 学位授与年月日:平成29年3月24日

1 Introduction| 2 Literature review on the adhesively bonded joints| 3 Debonding strength evaluation for butt joint in terms of the intensity of singular stress at the interface corner with and without fictitious crack| 4 Convenient analysis method for the intensity of singular stress field (ISSF) of lap joint| 5 Debonding criterion for single lap joint in terms of the ISSF| 6 Adhesive strength evaluation method focusing on the ISSF to minimize bend effect for single lap joint| 7 Conclusions

平成28年度

九州工業大学博士学位論文(要旨)学位記番号:工博甲第432号 学位授与年月日:平成29年3月24日

キーワード

Fracture Mechanics, Adhesively bonded joints, Intensity of singular stress field, Interfaces, Strength evaluation

各種コード

NII論文ID(NAID)

500001055001

NII著者ID(NRID)
  • 8000001173696
本文言語コード

eng

データ提供元

機関リポジトリ / NDLデジタルコレクション

外部リンク

博士論文 / 九州工業大学 / 工学

博士論文 / 九州工業大学

博士論文 / 工学

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