Investigation on the Adhesion Phenomena and Hysteresis Effect of Solid Materials in Intimate Contact

• Main Authors: Kuang-Chung Wu, 吳光中
• Other Authors: Hsien-I You
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/85148830649293741842

博士 === 中興大學 === 機械工程學系所 === 95 === The adhesion phenomena of molecular force between contact surfaces for solid materials in intimate contact are investigated. Firstly, the adhesion strength of coated films is examined in this work. Protective films made of Al2O3 ceramic oxide are deposited by sol-gel spin coating on the substrates of 440C stainless steel. The effects of substrate surface roughness and film hardening temperature on the coating characteristics are investigated. The adhesion strength of the film-substrate system is assessed by measuring the adhesion using a contact angle analyzer. Comparisons are made between the adhesion results and the critical loads obtained by scratch test. The wear resistance to sliding contact is represented by the wear weight loss of the coated film determined in a pin-on-disk test. The experimental results show that the ceramic films coated on smoother metallic surface strengthen the adhesive bonding between the substrate and the deposited film. The films coated on the smooth substrate and hardened at some high sintering temperature are experimentally determined to have high wear resistance to sliding contact. Secondly, the JKR contact theory is employed to study the adhesion phenomena between two solid materials in intimate contact. The elastic contact modulus and the work of adhesion of solid materials are obtained during adhesion tests by utilizing a micro force-deflection measuring apparatus. Six of the plastic materials, including POM, PA, PET, PVC, PP, and UHMWPE are used to evaluate the adhesion effect implied by the JKR theory. Comparison is made between surface energy obtained from the adhesion tests with that by a dynamic contact angle analyzer. Results show that the load/deflection data in the loading phase are in good agreement with the predictions of JKR equation, and the experimental data of unloading phase deviate significantly from the JKR theory. The phenomena of adhesion hysteresis in loading tests are responsible for these results due to the effects of molecular reconstruction on solid surfaces in contact. The work of adhesions, and hence surface energies of plastic materials, calculated by the best fitting of JKR equation with the experimental data in the loading phase, agree satisfactorily in a comparable manner with that obtained using the contact angle analyzer.