The phenomenon of fatigue in gears at the tooth root can be a cause of catastrophic failure if not detected in time. Where traditional low-frequency vibration may help in detecting a well-developed crack or a completely failed tooth, a system for early detection of the nucleation and initial propagation of a fatigue crack can be of great use in condition monitoring. Acoustic emission is a poten...

We have performed atomic simulations of crack propagation along a weak interface joining two harmonic crystals. The simulations show that a mode II shear dominated crack can accelerate to the Rayleigh wave speed and then nucleate an intersonic daughter that travels at the longitudinal wave speed. This contradicts the general belief that a crack can travel no faster than the Rayleigh speed.

The characterization of critical levels of microstructural damage that can lead to fatigue-crack propagation under high-cycle fatigue loading conditions is a major concern for the aircraft industry with respect to the structural integrity of turbine engine components. The extremely high cyclic frequencies characteristic of in-flight loading spectra necessitate that a damage-tolerant design appr...

In the lattice structure considered here, crack propagation is caused by feeding waves, carrying energy to the crack front, and accompanied by dissipative waves carrying a part of this energy away from the front (the di4erence is spent on the bond disintegration). The feeding waves di4er by their wavenumber. A zero feeding wavenumber corresponds to a macrolevel-associated solution with the clas...

Reinforced concrete is a composite material consisting in a rebar embedded in a concrete matrix. The structural equilibrium depends of the quality of bond between the two materials as well as the intrinsic quality of each of the components. When the structure is submitted to heating, cracking can occur due to the difference in thermal expansion properties between the two materials. In the prese...

We deal with the Ambrosio-Tortorelli approximation of the well-known Mumford-Shah functional to model quasi-static crack propagation in brittle materials. We employ anisotropic mesh adaptation to efficiently capture the crack path. Aim of this work is to investigate the numerical sensitivity of the crack behavior to the parameters involved in both the physical model and in the adaptive procedure.

Intersonic crack growth has been studied using an interfacial fracture model in which an additional material phase within a bonding layer is proposed to describe the failure behavior of the interface. In this material phase, a strain gradient based damage model is applied with a built-in cohesive law, which is governed by an material intrinsic length scale that bridges the mechanisms that opera...

Cracking in Silicon solar cells is an important factor for the electrical power-loss of photovoltaic modules. Simple geometrical criteria identifying the amount of inactive cell areas depending on the position of cracks with respect to the main electric conductors have been proposed in the literature to predict worst case scenarios. Here we present an experimental study based on the electrolumi...

This paper studies the failure mechanisms and the reliability of the chip-metallization of a new power module using a copper clip soldered on the top side of the chip, instead of aluminum wire bonds. Both power cycling tests and thermo-mechanical Finite Elements simulations are performed. This study takes advantages of the numerical simulations to analyze in details plastic strains and crack gr...

Understanding sub-Rayleigh-to-intersonic transition of mode II cracks is a fundamental problem in fracture mechanics with important practical implications for earthquake dynamics and seismic radiation. In the Burridge–Andrews mechanism, an intersonic daughter crack nucleates, for sufficiently high prestress, at the shear stress peak traveling with the shear wave speed in front of the main crack...