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When operating within the environments rich with sodium chloride, steel bars of reinforced concrete structures are often subject to corrosion caused by surrounding erosive materials, and the associated rust expansion force due to corrosion takes a critical role in determining the durability of relevant reinforced concrete structures. By investigating the corrosion course of steel reinforcement with theory of elasticity, a numerical rust expansion model is established for the moment of concrete surface rupture based on non-uniform sin function. Cuboid reinforced concrete specimen with squared cross sections is tested to analyze the rust expansion when concrete cracks due to corrosive forces. The utility of the established expansion model is validated by numerical simulation with Abaqus through the comparison between the associated outcomes. The impacts of steel bar diameter and concrete cover thickness on the magnitude of rust expansion force are discussed.

Concrete cracking caused by corrosion of reinforcement could significantly shorten the durability of reinforced concrete structure. It remains critical to investigate the process and mechanism of the corrosion occurring to concrete reinforcement and establish the theoretical prediction model of concrete expansion force for the whole process of corrosion cracking of reinforcement. Under the premise of uniform corrosion of reinforcing steel bars, the elastic mechanics analysis method is adopted to analyze the entire process starting from the corrosion of steel bars to the cracking of concrete due to corrosion. A relationship model between the expansion force of corrosion of steel bars and the surface strain of concrete is established. On the cuboid reinforced concrete specimens with square cross-sections, accelerated corrosion tests are carried out to calibrate and verify the established model. The model can be able to estimate the real-time expansion force of reinforced concrete at any time of the whole process from the initiation of steel corrosion to the end of concrete cracking by measuring the surface strain of concrete. It could be useful for quantitative real-time monitoring of steel corrosion in concrete structures.

The mechanical behaviors of granular materials are governed by the grain properties and microstructure of the materials. We conducted experiments to study the force transmission in granular materials using plane strain tests. The large amount of nearly continuous displacement data provided by the advanced noncontact experimental technique of digital image correlation (DIC) has provided a means to quantify local displacements and strains at the particle level. The average strain of each particle could be calculated based on the DIC method, and the average stress could be obtained using Hooke's law. The relationship between the stress and particle force could be obtained based on basic Newtonian mechanics and the balance of linear momentum at the particle level. This methodology is introduced and validated. In the testing procedure, the system is tested in real 2D particle cases, and the contact forces and force chain are obtained and analyzed. The system has great potential for analyzing a real granular system and measuring the contact forces and force chain.

Aiming at the thermal mismatch caused by different Coefficients of Thermal Expansion(CTE)of each material in Chip on Board(COB),Digital Image Correlation(DIC)is used to measure the thermomechanical coupling effect in COB packaging structures,and effects of different type substrate are compared.The experiment results are compared with both the results of FEM simulations and the theoretical model.Experimental results reveal that DIC can successfully be applied to the analysis of the thermomechanical coupling effect and provide an availability consult to the design of MEMS apparatus.

The development and evolution of the force chain in a granular system is an important factor that affects the stability of granular systems. In this work, the displacement threshold (SC) and angle threshold (θd) are proposed, and a new method to predict the damage point in the force chain is introduced and verified. A two-dimensional steel ball particle system under concentrated loading is analyzed; during the deformation process, images are constantly recorded by a CCD camera. Based on the digital image correlation method, the displacement and movement direction of each particle in the steel ball particle system is analyzed, and a prediction analysis of the damage point in the force chains is performed.

Digital speckle correlation method (DSCM) is used to measure the thermomechanical coupling effect in COB packaging structures. CCD camera is applied to capture the speckle patterns of CMOS chip at different temperature fields. Analyzing the speckle patterns, the in-plane deformation of the CMOS chip is obtained. Based on the trigonometrical theory, out-plane displacement can be obtained by measuring of in-plane displacement, and then the elastic thermal stress of the chip is evaluated when the application of the temperature field is repeated. Experiment results are compared with both the results of FEM simulations and the theoretical model. There results are agreed well and it can be proved that DSCM can successfully be applied to analyze the thermomechanical coupling effect. The theoretical model was also verified by result of FEM simulations and experiment testing. Experiment results provide an availability consult to the design of MEMS apparatus.