By taking Local indention effect and foam core strength into account in the overall deflection process, a novel theoretical model is investigated to predict the large deflection with Local indentation of sandwich beam under quasi-static lateral loading. The theoretical and numerical models of lateral crushing force and total plastic energy are proposed and the theoretical results agree well with numerical and experimental results of previous researches. The results conclude that Local indention phase plays an important role in initial collapse deflection of sandwich beam when maximum deflection is greater than face sheets thickness. In addition, the theoretical results with and without Local indention phase of total plastic energy are compared and it shows that total plastic energy of sandwich beam will be overestimated if Local indention phase is neglected. The present analytical model can predict the large deflection behavior with Local indention of sandwich beam reasonably.

In this paper, we analyze the effect of stress-fiber inclusion on the stiffness of an actin random network. We use a discrete random network model to analyze the elastic response of this system in terms of apparent Young’ s modulus. First, we showed that for a flat-ended cylindrical indenter the total indentation force has a linear relation with the indentation depth and the indenter radius. Using this relation, we concluded that the stiffening effect of the stress-fiber on the fibrous network has a range of effectivity and surprisingly, the stiffening is not maximum when the stress-fiber is straight below the indenter but when it is a certain distance from it. These results shed light on some aspects of the widely used AFM stiffness measurements of cells.

indentation forming is an internal tube forming process in which a mandrel with a diameter slightly larger than that of the tube is pressed inside the tube and in so doing, creates the internal profile. Forming forces have a significant effect on the spring back, residual stress, quality of the inner surface, quality of tube dimensions, and tool wear. In this study, the forming process of CK45 steel tube by carbide tungsten tool in the presence of ultrasonic vibration has been simulated and the effect of ultrasonic on the forming mechanism has been investigated by introducing two regimes according to the forming conditions. The effects of tool feed-speed and amplitude of vibration on forming force reduction have been investigated. According to the simulation results, the main reason for the force reduction in the presence of longitudinal tube ultrasonic vibration is the intermittent phenomenon which is the continuous or impulsive regime. The critical amplitude which determines the borderline of continuous and impulsive regimes is obtained 38μ m by the simulation of the process. The maximum force reduction obtained in continuous regime is 64. 2% at the critical amplitude. The simulation results are consistent well with the previous experimental data.

The objective of the present work is to investigate indentation in polymers and hyperelastic materials. Both experiments and numerical analysis have been carried out. Two different sports floorings were selected to test, monolayer rubber and two layer polyurethane (PU)/polyvinylchloride (PVC). To determine the value of hardness and indentation depth of indenter in the materials, experimental study was carried out according to quality standard test for sports flooring. The numerical analysis was also conducted by Abaqus software using simulation of experimental testing conditions, selection of the best hyperelastic model and comparison of the results to experimental test in order to ascertain the efficiency and accuracy of each simulation step. The accuracy of the results has been shown by comparision of experiments with numerical results. For the first sample, indentation depth was 0.575 mm (based on experimental result) and Yeoh’s model was employed to simulate with the error of 4.3%. The indentation depth and error (by selection of reduced polynomial form of order two models) were 0.425 mm and 0.94% for the second sample (PU/PVC), respectively. In addition, hardness was decreased from 78.1 to 75.3 when the thickness of rubber sports flooring was increased from 2.5 to 5 mm. In general, it can be concluded that the hardness values of polymers depend on their thickness, and on the other hand the indenter shape has an influence on indentation depth and force-displacement curves as well.