Study of Interaction between Crack Opening Displacement and Diffraction Waves in Mortar

• Main Authors: Hu, Meng-Tzong, 胡盟宗
• Other Authors: Y.C.Lin
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/60283929471693129715

碩士 === 國立中興大學 === 土木工程學系 === 86 === In this thesis, experimental studies are carried out to investigate the interaction of diffraction waves with crack opening displacements in mortar. With great potential, the impact-generated stress waves and time-of-flight technique can be used to determine the depth of surface-opening cracks in concrete structures. The objectives of the studies are to verify the accuracy of the time-of-flight technique and to answer a question about how wide the crack opening displacement should be for diffraction waves able to propagate across. The experimental idea proposed in the studies has never seen in literature on the technology of concrete. To reduce experimental variables, the specimen used in the studies is made of mortar. The specimen is cracked vertically by displacement control. A relationship between the crack opening displacement and the depth is established. The crack depth of the cracked specimen is then determined by the time-of-flight diffraction technique. Results obtained from experimental studies show that diffraction waves are generated in the area where particles are partly separated and partly bonded. A crack width of 0.015 mm is obtained for diffraction waves able to propagate across the crack. In addition, a normal incident stress wave can penetrate a crack when the crack width is less than 0.057 mm.