arXiv subjects

Roshan Philip Saji

Publications and source records attributed to Roshan Philip Saji.

3 recordsLinked to original sources

arXiv2026

BRIDGE: Bridging Routine Inputs and Digital modelling for Geotechnical Engineering

The mechanical properties needed for geotechnical design require laboratory tests and are thus available for far fewer field samples than routinely measured basic (index) properties which are available for nearly every sample. We term this difference as the characterization gap. Purely data-driven models do not explicitly enforce physical laws and may be unreliable beyond their training domain, while direct constitutive calibration preserves physical consistency but requires advanced laboratory data and expert judgment. We therefore propose BRIDGE (Bridging Routine Inputs and Digital modelling for Geotechnical Engineering) a modular framework that predicts mechanical properties from routinely available basic properties. BRIDGE screens the dataset for outliers and non-physical responses, bins the retained samples into Cells, and selects a small calibration dataset from each Cell, while the remaining samples are used for validation. A mechanical model is then calibrated for each calibration sample, and the converged calibrations collectively define the mechanical surrogate of the Cell together with its parameter ranges and the corresponding predictive envelope in the mechanical property space. A Cell is validated when most validation samples fall within this envelope, whereupon the surrogate can predict the mechanical property ranges of new samples whose basic properties lie within the Cell. In this work, we adopt a finite element implementation of the Extended Cam-Clay (ECC) constitutive model as the mechanical model, whose four parameters are calibrated in a multi-stage process. Applied to the Tokyo-CLAY/14/67760 database, BRIDGE predicts the mechanical properties of an entire Cell from calibrations of just 10 to 20% of its samples. Finally, since the mechanical model, the binning criteria, and the sampling method are components of BRIDGE, the framework is easily extensible.

cs.CE↗

arXiv2025

Modified non-local damage model: resolving spurious damage evolution

Accurate prediction of damage and fracture evolution is critical for the safety design and preventive maintenance of engineering structures, however existing computational methods face significant limitations. On one hand, discrete damage and phase-field models are often computationally prohibitive for real world applications and they are less generalizable across different material classes. On the other hand, conventional gradient damage models which are based on phenomenological laws, though more computationally efficient, they suffer from unrealistic widening of the damage-band as damage progresses. This paper presents a modified non-local gradient damage model (MNLD) that overcomes these shortcomings by introducing modifications to the stress degradation function and forcing term in the Helmholtz free energy expression. These two modifications ensure that as damage approaches its maximum value, both the thermodynamic damage driving force for damage vanishes and the evolution of the forcing term decays. Consequently, the damage band retains a non-growing constant width throughout its evolution. The proposed approach builds on insights gained from two intermediate models, which addressed the necessary conditions separately before integrating them into a unified formulation. Numerical validation is performed on several 1D and 2D benchmark problems, demonstrating that the proposed model can reliably produce fixed-width damage bands. The proposed approach can be implemented within existing gradient damage-based finite element frameworks with minimal implementation changes. The results highlight the potential of this approach to resolve the decades-long challenge of spurious widening in gradient damage models, offering an effective and practical solution for engineering applications.

physics.comp-ph↗

arXiv2024

A new unified arc-length method for damage mechanics problems

The numerical solution of continuum damage mechanics (CDM) problems suffers from convergence-related challenges during the material softening stage, and consequently existing iterative solvers are subject to a trade-off between computational expense and solution accuracy. In this work, we present a novel unified arc-length (UAL) method, and we derive the formulation of the analytical tangent matrix and governing system of equations for both local and non-local gradient damage problems. Unlike existing versions of arc-length solvers that monolithically scale the external force vector, the proposed method treats the latter as an independent variable and determines the position of the system on the equilibrium path based on all the nodal variations of the external force vector. This approach renders the proposed solver substantially more efficient and robust than existing solvers used in CDM problems. We demonstrate the considerable advantages of the proposed algorithm through several benchmark 1D problems with sharp snap-backs and 2D examples under various boundary conditions and loading scenarios. The proposed UAL approach exhibits a superior ability of overcoming critical increments along the equilibrium path. Moreover, in the presented examples, the proposed UAL method is 1-2 orders of magnitude faster than force-controlled arc-length and monolithic Newton-Raphson solvers.

cs.CE↗