arXiv subjects

Angel Santarossa

Publications and source records attributed to Angel Santarossa.

6 recordsLinked to original sources

arXiv2025

Configurational forces explain echelon cracks in soft materials

Soft fracture in highly deformable solids involves both geometric and constitutive nonlinearities, necessitating advanced theoretical and computational frameworks for its accurate understanding. Tensile fractures subjected to mixed-mode loading deviate from their original planar shape, resulting in echelon crack patterns. When out-of-plane shear is superimposed, a crack front segments into an array of tilted facets. The physical interpretation of echelon cracks is only marginally understood, and it is customarily based on rather limited approaches based on Linear Elastic Fracture Mechanics. Here we investigate mixed-mode I + III fracture within the framework of configurational mechanics. Using the Configurational Force Method, implemented as a post-processing algorithm in a finite-element-based simulation, we compute the configurational forces acting at the crack tip of model fracture geometries prior to propagation. Configurational forces characterize both the magnitude and direction of propagation for maximal energy release rate. Our results reveal the complex interactions between tilted facets and their critical role in shaping the fracture morphology. We also examine the effects of facet coalescence-driven by the growth of the parent crack-where neighboring facets merge into a unified crack front. These findings provide new insights into fracture processes in soft, quasi-brittle materials under mixed-mode loading.

cond-mat.soft↗

arXiv2024

Enhanced Interlocking in Granular Jamming Grippers through Hard and Soft Particle Mixtures

We investigate the influence of particle stiffness on the grasping performance of granular grippers, a class of soft robotic effectors that utilize granular jamming for object manipulation. Through experimental analyses and X-ray imaging, we show that grippers with soft particles exhibit improved wrapping of the object after jamming, in contrast to grippers with rigid particles. This results in significantly increased holding force through the interlocking. The addition of a small proportion of rigid particles into a predominantly soft particle mixture maintains the improved wrapping but also significantly increases the maximum holding force. These results suggest a tunable approach to optimizing the design of granular grippers for improved performance in soft robotics applications.

cond-mat.soft↗

arXiv2024

Granular jamming gripper with integrated suction

Granular grippers can manipulate a wide variety of objects, but need to be pressed on the object to conform to it. If the object is placed on unstable ground, e.g., on sand or water, this step might cause the object to sink or move away from the gripper, hindering proper operation. We introduce a granular gripper with an integrated suction cup, where suction and jamming are controlled independently. We demonstrate the system's robust and enhanced gripping capabilities by comparing its grasping performance with a typical granular gripper design. We show that the proposed device can grip objects that are challenging for typical granular grippers, including those placed on unstable ground, as the suction cup stabilizes the object, allowing the gripper to conform.

cond-mat.soft↗

arXiv2023

Granular binary mixtures improve energy dissipation efficiency of granular dampers

Granular dampers are systems used to attenuate undesired vibrations produced by mechanical devices. They consist of cavities filled by granular particles. In this work, we consider a granular damper filled with a binary mixture of frictionless spherical particles of the same material but different size using numerical discrete element method simulations. We show that the damping efficiency is largely influenced by the composition of the binary mixture.

cond-mat.soft↗

arXiv2022

Effect of Particle Size on the Suction Mechanism in Granular Grippers

Granular grippers are highly adaptable end-effectors that exploit the reversible jamming transition of granular materials to hold and manipulate objects. Their holding force comes from the combination of three mechanisms: frictional forces, geometrical constraints, and suction effects. In this work, we experimentally study the effect of particle size on the suction mechanism. Through X-ray computed tomography, we show that small particles (average diameter d = 120 micrometers) achieve higher conformation around the object than larger particles (d = 4mm), thus allowing the formation of air-tight seals. When the gripper is pulled off, mimicking lifting of an object, vacuum pressure is generated in the sealed cavity at the interface gripper--object. If the particles used as filling material are too large, the gripper does not conform closely around the object, leaving gaps between the gripper's membrane and the object. These gaps prevent the formation of sealed vacuum cavities between the object and the gripper and in turn hinder the suction mechanism from operating.

cond-mat.soft↗

arXiv2022

Soft particles reinforce robotic grippers: Robotic grippers based on granular jamming of soft particles

Granular jamming has been identified as a fundamental mechanism for the operation of robotic grippers. In this work, we show, that soft particles like expanded polystyrene beads lead to significantly larger gripping forces in comparison to rigid particles. In contradiction to naive expectation, the combination of jamming and elasticity gives rise to very different properties of the jammed phase, compared to hard-particle systems. This may be of interest also beyond the application in robotic grippers.

cond-mat.soft↗