Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

Here the possibility of developing a better three dimensional model for rubber when Hencky strain is written as an explicit function of the Cauchy stress is examined. Based on the experimental evidence, vulcanized unfilled rubber is assumed to be isotropic, incompressible, and deforming from a stress-free reference configuration. Vulcanized unfilled rubber undergoes strain-induced crystallization when uniaxial stretch exceeds 2. Therefore, in this study, a non-dissipative model is sought for rubber only till the von Mises stress is below a critical value. Using the biaxial response reported in Kawabata et al. (1981), the material functions are arrived adopting Rivlin and Saunders methodology. The material constants in the determined material functions are found using biaxial tests for four other experimental studies on rubber reported in the literature. The ability of the arrived constitutive model to describe the uniaxial and equal biaxial response of the same rubber is evaluated. The proposed model is benchmarked with established models in the classical framework. Among the models studied the proposed model performed as well as the other models for Kawabata et al. data set and marginally better than the other models for the remaining four experimental data sets. However, while the proposed model performance does not critically depend on the experiments used to deduce the material parameters, for the other models the material parameters need to be found from fixed biaxial experiments for better performance. © 2020 Elsevier Ltd

Department of Civil Engineering

World University root node

International Journal of Engineering Science

Modeling the non-dissipative response of vulcanized unfilled rubber

The validity of some of the assumptions made during systematic development of constitutive relation – homogeneity, isotropy, and non-dissipative response – is examined experimentally by testing plain concrete cylinders in the circumferential displacement controlled uniaxial compression tests. The tested cylinders indicate that the surface strains are not uniform and that the principal direction of the strain varies with the magnitude of the applied load. Hence, these cylinders are either deforming from a stressed state or anisotropic or both. The percentage dissipation computed as the area between the loading and unloading curves normalized using the area under the unloading curve is less than 10 percent up to 90 percent of the peak load. Therefore the mechanical response of concrete can be considered as non-dissipative. Assuming that the magnitude of the residual stresses present in the concrete panels would be small compared to the stresses arising due to the applied load, these residual stresses are ignored. Consequently, using the implicit constitutive theory framework for isotropic and compressible materials undergoing a non-dissipative process from a stress-free reference configuration, a three-dimensional constitutive relation for plain concrete is proposed. The material parameters in the proposed model are estimated from the uniaxial compression test and equal biaxial compression test. These parameters are expressed using initial Young's modulus, initial Poisson's ratio, maximum uniaxial compressive stress, the axial and transverse strain corresponding to the maximum uniaxial compressive stress, maximum equal biaxial compressive stress and the equal biaxial strain corresponding to maximum equal biaxial compressive stress. The ability of the proposed model to capture the response of various grade and type of concrete in ten biaxial experiments reported in the literature is examined. It is found that despite the limiting assumptions, the compression-compression, compression-tension and tension-tension stress strain response of the concrete in these ten experiments are adequately captured by the proposed model with mean R 2 value of 0.94. © 2019 Elsevier Ltd

Construction and Building Materials

A three dimensional constitutive model for plain cement concrete

A methodology for obtaining implicit constitutive representations involving the Cauchy stress and the Hencky strain for isotropic materials undergoing a non-dissipative process is developed. Using this methodology, a general constitutive representation for a subclass of implicit models relating the Cauchy stress and the Hencky strain is obtained for an isotropic material with no internal constraints. It is shown that even for this subclass, unlike classical Green elasticity, one has to specify three potentials to relate the Cauchy stress and the Hencky strain. Then, a procedure to obtain implicit constitutive representations for isotropic materials with internal constraints is presented. As an illustration, it is shown that for incompressible materials the Cauchy stress and the Hencky strain could be related through a single potential. Finally, constitutive approximations are obtained when the displacement gradient is small. © 2017, Springer International Publishing AG.