The mechanical reliability of silicon dies is affected by the defects introduced by surface grinding and edge dicing. The ring-on-ring and the four-point-bend test have been used in this study to separate the distribution in strength for these two types of defect. At low probabilities of failure, it is the “strength” of the edge defects that dominate the reliability. However, if the edges of the die are only lightly stressed compared with the surface, edge defects are unlikely to cause fracture. In this case the use of the four-point-bend test, which is sensitive to both edge and surface defects, will result in an underestimate of the reliability and if only one test is to be performed the ring-on-ring test is preferable to the four-point-bend test. Generally, for a full reliability estimate, the distributions of both types of defect need to be determined.
To investigate the restraint effect of reinforcing bar on the expansion induced by alkali-silica reaction (ASR), and assess the mechanical behavior of reinforced concrete (RC) structure damaged by ASR, pullout tests of specimens with different ASR expansion were conducted. Accelerated ASR tests of specimens with diameters of 12 mm, 16 mm, and 20mm were conducted to qualify the restraint effect of reinforcing bar. Pullout tests were used to investigate the relationship between nominal bond strength and ASR expansion. Test results show that ASR expansion decreases with the increase of the rebar diameter. Nominal bond strength of specimens increased initially to attain their peak at 14 days, approximately with the expansion of 0.035%. After that, the nominal bond strength decreased near-linearly with the increment of the expansion. A simplified ASR expansion model integrated with the poro-mechanical model was adopted to analyze the restraint effect. The verification of the proposed method was conducted by comparing the analytically predicted results with the test data. The results show that the proposed method could accurately predict both the ASR expansion and bond strength.
To investigate the mechanical properties of dowel action under fatigue loads, 3 reinforced concrete specimens with different bar diameters (12 mm, 20 mm, and 25 mm) were subjected to the fatigue loading and were designed to investigate the attenuation character of dowel action and the fatigue failure modes. e load transfer mechanism of the bond was analyzed based on the 3D relative motions between reinforcing bars and subgrade concrete. Fatigue damage effects were considered in the model. A deterioration coefficient based on the deformation path was defined to represent the accumulation of fatigue damage. Verification of the model was conducted by comparing the analysis results with experimental data obtained in this study and from the literature, and satisfactory agreement was obtained.
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