جستجوی مقالات مرتبط با کلیدواژه « associated flow rule » در نشریات گروه « فنی و مهندسی »

Following the recent work of the authors in development and numerical verification of a new kinematic approach of the limit analysis for surface footings on non-associative materials, a practical procedure is proposed to utilize the theory. It is known that both the peak friction angle and dilation angle depend on the sand density as well as the stress level, which was not the concern of the former work.In the current work, a practical procedure is established to provide a better estimate of the bearing capacity of surface footings on sand which is often non-associative. This practical procedure is based on the results obtained theoretically and requires the density index and the critical state friction angle of the sand. The proposed practical procedure is a simple iterative computational procedure which relates the density index of the sand, stress level, dilation angle, peak friction angle and eventually the bearing capacity. The procedure is described and verified among available footing load test data.

One of the new research fields in plasticity is related to choosing a proper non-associated flow rule (NAFR), instead of the associated one (AFR), to predict the experimental results more accurately. The idea of the current research is derived from combining von Mises and Tresca criteria in the places of yield and plastic potential surfaces in rate-independent plasticity. This idea is implemented using backward Euler method in non-linear finite element simulation. The results are compared with the experimental data for an internally pressurized thick-walled cylinder and it is demonstrates that, using the proposed NAFR in rate-independent plasticity, the experimental results could be predicted more accurately. Finally, it can be said that the current research confirms the results of the previous works on rate-dependent plasticity (viscoplasticity) in steady state conditions.

This paper developed a new elastoplastic model for coarse-grained soils. Plastic potential surface was established by solving a differential dilatancy equation, which is obtained via the triaxial test results. This model obeys a non-associated flow rule; therefore, the yield surface is not consistent with the plastic potential surface. Expression of the yield surface was established similar to the plastic potential surface, but its shape is influenced not only by the stress ratio η, but the mean stress p. A unified hardening parameter that is independent of stress path is adopted, so that negative dilatancy and positive dilatancy properties of coarse-grained soils could both be described. In this research, elastoplastic formula of the proposed model is deduced. This model was also evaluated with several groups of test results under different stress paths (i.e. conventional triaxial tests, constant mean stress test and constant stress ratio test, etc.). Results showed that model predictions agree well with the test results.