A three-dimensional (3D) numerical manifold formulation with continuous nodal gradients (H8-CNS) is presented for dynamic analysis of saturated elasto-plastic porous media based on the three-variable (u−w−p) formulation. Using meshes of 8-node hexahedra as mathematical patches, the skeleton displacement (u) and fluid velocity (w) interpolations are constructed with a constrained and ortho-normalized

This paper proposes a simple yet efficient mortar-type method to couple independent finite element subdomains with intersecting interfaces. In this method, we split the subdomain interfaces into several contact patches. Different patches are allowed to have the same master/slave nodes. To eliminate the over-constrained behavior that often occurs in conventional mortar methods, we divide the constraint

This paper presents a deep learning-based de-homogenization method for structural compliance minimization. By using a convolutional neural network to parameterize the mapping from a set of lamination parameters on a coarse mesh to a one-scale design on a fine mesh, we avoid solving the least square problems associated with traditional de-homogenization approaches and save time correspondingly. To train

Hierarchical computational methods for multiscale mechanics such as the FE2 and FE-FFT methods are generally accompanied by high computational costs. Data-driven approaches are able to speed the process up significantly by enabling to incorporate the effective micromechanical response in macroscale simulations without the need of performing additional computations at each Gauss point explicitly. Traditionally

This study focuses on the development of a complementary fatigue crack-tip evaluation approach with multiscale optical techniques with different resolutions. A middle tension (MT) specimen, of aluminium alloy AA6082-T6, was prepared and submitted to a cyclic fatigue loading to generate a fatigue crack. Then, it was statically loaded under a uniaxial tensile condition, and two non-contact full-field

This paper discusses suitable strain and stress low-cycle fatigue (LCF) parameters for Alloy 738LC, a Ni-based superalloy, under tension–torsion loading at 1173 K. Tension–torsion proportional LCF tests were performed using the superalloy at two strain rates. Five strain and four stress parameters were applied to estimate LCF life at the two strain rates. Suitable strain parameters for multiaxial LCF

In this paper, the thermo-mechanical coupling fatigue experiments of NiTi shape memory alloy (SMA) micro-tubes involving one-way shape memory effect (OWSME) are first carried out under the uniaxial and multiaxial stress-controlled cyclic loadings with some specific loading paths and stress levels. Experimental results show that the OWSME cyclic degradation and fatigue lives of NiTi alloy micro-tubes

This study proposes a Bayesian inference-based decision framework to quantify the physical uncertainty based on fatigue life tests on maraging steel according to post-processing treatments and build orientations. Uncertainty quantification of fatigue life models is performed to determine the most suitable models for the metal additive manufacturing process by employing Bayesian inference. To select

Three-dimensional (3D) printing of continuous fiber-reinforced composites (FRCs) and automated fiber placement (AFP) technology have enabled the fabrication of variable stiffness composites (VSCs), a kind of advanced composite materials reinforced by curvilinear fibers, which have been demonstrated with superior global mechanical properties. However, the fracture behaviors, an indispensable factor

The conventional gradient enhanced plasticity model uses a nonlocal gradient regularization to avoid mesh sensitivity issues present in the continuum-based local plasticity models. These conventional gradient plasticity models are found to manifest spurious spreading of localization zone during the post-peak regime, leading to non-physical structural and fracture response. Therefore, in the present

It is challenging to simulate large-scale or fine-resolution multivariate three-dimensional (3D) cross-correlated conditional random fields because of computational issues such as inverting, storing or Cholesky decomposition of large correlation matrices. Recently, an efficient univariate 3D conditional random field simulation method was developed based on the separability assumption of the autocorrelation

A crack terminating at an arbitrary angle to the interface between two neo-Hookean sheets is investigated under plane stress conditions using finite deformation theory. The asymptotic crack-tip deformation and stress fields are analyzed as a function of the ratio of the moduli and the angle of the crack relative to the interface. Full-field numerical calculations and experimental studies validate the

Power law distributed fluctuations are known to accompany terminal failure in disordered brittle solids. The associated intermittent scale-free behavior is of interest from the fundamental point of view as it emerges universally from an intricate interplay of threshold-type nonlinearity, quenched disorder, and long-range interactions. We use the simplest mean-field description of such systems to show

“Viscosity is the most ubiquitous dissipative mechanical behavior” (Maugin, 1999). Despite its ubiquity, even for those systems where the mechanisms causing viscous and other forms of dissipation are known there are only a few quantitative models that extract the macroscopic rheological response from these microscopic mechanisms. One such mechanism is the stochastic breaking and forming of bonds which

Constitutive modeling of dielectric elastomers has been of long standing interest in mechanics. Over the last two decades rigorous constitutive models have been developed that couple the electrical response of these polymers with large deformations characteristic of soft solids. A drawback of these models is that unlike classic models of rubber elasticity they do not consider the coupled electromechanical

Fatigue tests were conducted under constant amplitude loading with a stress ratio of R=-1 to evaluate the effect of defect/inclusion on fatigue life of welding martensitic stainless steel (13Cr-5Ni) and KSFA90 steel (manufactured for crankshaft). An analysis based on the combined areaeff of defect/inclusion and linear elastic fracture mechanics (LEFM), was performed. The results indicate that defect/inclusion

A crack growth model for assessing the lifetime and short fatigue crack growth of ductile cast iron materials is proposed. The model bases on the assumption that the crack advance per cycle correlates with the cyclic crack tip opening displacement. Intergranular embrittlement at medium temperatures is accounted for as a temperature and strain rate dependent crack accelerating mechanism. The model is

High-frequency-mechanical-impact (HFMI) is a post-weld treatment for improving the fatigue strength of welded structures, by introducing compressive residual stresses, localized strain hardening and enlarged weld toe radii. The Peak Stress Method (PSM) is extended for the first time to the fatigue strength assessment of HFMI treated steel joints, by means of a dedicated analysis procedure and new fatigue

The present investigation is concerned with the high-cycle axial fatigue behaviour of a third generation Al-steel butt weld made by Hybrid Metal Extrusion & Bonding (HYB). In this particular weld, metallurgical bonding is achieved by a combination of microscale mechanical interlocking and intermetallic compound (IMC) formation, where the IMC layer is in the sub-micrometre range (<1µm). During high-cycle

Given an unstructured mesh consisting of quadrilaterals and triangles (we allow both planar and non-planar meshes of arbitrary topology), we present the construction of quadratic splines of mixed smoothness — C1 smooth away from the unstructured regions of T and C0 smooth otherwise. The splines have several useful B-spline-like properties – partition of unity, non-negativity, local support and linear

We investigate volume-element sampling strategies for the stochastic homogenization of particle-reinforced composites and show, via computational experiments, that an improper treatment of particles intersecting the boundary of the computational cell may affect the accuracy of the computed effective properties. Motivated by recent results on a superior convergence rate of the systematic error for periodized

This work presents a novel approach for defect based fatigue failure characterization using artificial intelligence (AI). An artificial neural network (ANN) is trained on experimentally determined data that is highly relevant in terms of fatigue. Load stress, hardness and killer defect size are the three main parameters defined as input arguments. Fatigue testing either reveals failure or non-failure

When they are damaged or injured, soft biological tissues are able to self-repair and heal. Mechanics is critical during the healing process, as the damaged extracellular matrix (ECM) tends to be replaced with a new undamaged ECM supporting homeostatic stresses. Computational modeling has been commonly used to simulate the healing process. However, there is a pressing need to have a unified thermodynamics

The thermal barrier coatings (TBCs) are serviced in elevated thermal conditions characterized by chemo-thermo-mechanical (C-T-M) failure mechanism and multiscale failure modes. In the present work, isothermal, cyclic thermal and mechanical induced spalling tests were carried out. Since the contribution of aluminum migration in TBCs damage evolution and failure was confirmed, the C-T-M life prediction

A polyacrylamide hydrogel exhibits near-perfect elasticity: its stress-stretch curve is rate-independent and has negligible hysteresis. The near-perfect elasticity results from the large amount of water between the polymer chains. Water has low viscosity and lubricates polymer chains. Here we report that the polyacrylamide hydrogel exhibits rate-dependent toughness when the polymer chains are long

The effects of laser shock peening (LSP) on the fatigue life of AA7075-T651 were investigated. The combined influence of surface imperfections (i.e. pits and intermetallics), compressive residual stresses (CRS) and the applied stress on crack initiation sites (surface or subsurface) and the associated fatigue life were investigated. Critical surface imperfections were found to significantly reduce

In this investigation, the fatigue and crack growth behavior of the ductile cast iron material (DCI) GJS-500 was experimentally characterized by performing isothermal low cycle fatigue (LCF) tests, out-of-phase thermomechanical fatigue (OPTMF) tests as well as low cycle fatigue tests combined with the replica testing method (LCF-R) within the temperature range RT–500 °C. The studied material exhibits

In many applications, glass fabrics are subject to cyclic forces. Here we show that a glass fabric can tear under a much lower cyclic force than monotonic force. For samples of a given width, a threshold force exists below which the fabric does not tear under cyclic load, and a critical force exists at which the fabric tears under monotonic load. For example, for 80 mm wide sample, the threshold force

The Eshelby formalism for an inclusion in a solid is of significant theoretical and practical implications in mechanics and other fields of heterogeneous media. Eshelby’s finding that a uniform eigenstrain prescribed in a solitary ellipsoidal inclusion in an infinite isotropic medium results in a uniform elastic strain field in the inclusion leads to the conjecture that the ellipsoid is the only inclusion

Deep learning-based reduced order models (DL-ROMs) have been recently proposed to overcome common limitations shared by conventional reduced order models (ROMs) – built, e.g., through proper orthogonal decomposition (POD) – when applied to nonlinear time-dependent parametrized partial differential equations (PDEs). These might be related to (i) the need to deal with projections onto high dimensional

This paper investigates the effect of loading history on cyclic deformation and fatigue behaviour of 7075-T651 aluminium alloy subjected to two-step loading. High-low and low-high sequences, encompassing both symmetrical and asymmetrical steps, are performed under strain-controlled mode for different loading scenarios. An elastic-plastic constitutive model is developed using the finite element method

In this study, high cycle fatigue behavior of friction stir welded aluminum 2024 alloy was investigated at different mean stresses. Complexity in the microstructure and tensile residual stress in the weld zone had a significant impact on the fatigue behavior of the welded joints. Apparent increase in mean stresses due to tensile residual stresses, decreased the fatigue lives of the welded joints. Increase

The cyclic behavior and microstructure evolution of Ti-6Al-4V-0.55Fe alloy were investigated with three different total strain amplitudes. A slight softening was occurred with Δεt/2 = 1.20%, and the alloy mainly suffered α recrystallization. Besides, a gentle softening can be observed with Δεt/2 = 1.60%, which led to more substructure deformation. Furthermore, a sudden drop of the stress amplitude

In this study, the high-cycle and very-high-cycle fatigue properties of carbon fiber reinforced plastic (CFRP)-aramid honeycomb sandwich structure, which is a commonly used structure in aviation industry, are examined under two different core directions using the ultrasonic three-point bending fatigue test. Further, the fatigue failure modes and damage mechanism of the structure are revealed. The results

Strain softening is responsible for mesh dependence in numerical analyses concerning a vast variety of fields such as solid mechanics, dynamics, biomechanics and geomechanics. Therefore, numerical methods that regularize strain localization are paramount in the analysis and design of engineering products and systems. In this paper we revisit the elasto-viscoplastic, strain-softening, strain-rate hardening

Many-query problems – arising from, e.g., uncertainty quantification, Bayesian inversion, Bayesian optimal experimental design, and optimization under uncertainty – require numerous evaluations of a parameter-to-output map. These evaluations become prohibitive if this parametric map is high-dimensional and involves expensive solution of partial differential equations (PDEs). To tackle this challenge

Cauchy-elastic solids include hyper-elasticity and a subset of elastic materials for which the stress does not follow from a scalar strain potential. More in general, hypo-elastic materials are only defined incrementally and comprise Cauchy-elasticity. Infringement of the hyper-elastic ‘dogma’ is so far unattempted and normally believed to be impossible, as it apparently violates thermodynamics, because

This paper focuses on the relationship between the fatigue performance and the presence of process or corrosion related defects for a 316L stainless steel manufactured by Laser Powder Bed Fusion. The fatigue responses of three batches (polished, pre-corroded and with an Electric Discharge Machined (EDM) defect) were investigated. A good correlation between Murakami’s area parameter and the fatigue

Though modeling material cyclic plasticity in a probabilistic way can yield a more accurate result than deterministic modelling method, it is quite hard to perform uncertainty quantification for all the material parameters. In this paper, Sobol’s global sensitivity analysis is applied to cyclic plasticity model to investigate how the variation of these parameters affect fatigue reliability evaluation

We present a projection-based model reduction formulation for parametrized time-dependent nonlinear partial differential equations (PDEs). Our approach builds on the following ingredients: reduced bases (RB), which provide rapidly convergent approximations of the parameter-temporal solution manifold; reduced quadrature (RQ) rules, which provide hyperreduction of the nonlinear residual; and the dual-weighted

Under fatigue-loading, short-fiber reinforced thermoplastic materials typically show a progressive degradation of the stiffness tensor. The stiffness degradation prior to failure is of primary interest from an engineering perspective, as it determines when fatigue cracks nucleate. Efficient modeling of this fatigue stage allows the engineer to monitor the fatigue-process prior to failure and design

The hump formation mechanism has not been fully understood so far, mainly because of two difficulties in analysis. The first one is how to find the most important external characteristic factor inducing humps, and the other is how to avoid too many assumptions when analysing the change in the runner’s capacity for work (the direct use of Euler’s formula makes too many assumptions). This paper proposes

Novel destructive method is implemented for quantitative assessment of fatigue damage accumulation in the stress concentration zone near the cold-expanded hole, which is characterized by residual stress influence. Damage accumulation is reached by preliminary push-pull loading of plane specimens with cold-expanded holes. Artificially introduced narrow notches, emanating from the hole edge at different

In this paper, we present an isogeometric analysis for studying the dynamical behavior of inextensible vesicles under an external fluid flow with inertial forces. We consider a phase-field model Aland, et al. (2014) for the coupled fluid–vesicle problem which enforces global area and volume constraints using a Lagrange multiplier method and employs an extra equation for enforcing local inextensibility

We address numerical solvers for a poromechanics model particularly adapted for soft materials, as it generally respects thermodynamics principles and energy balance. Considering the multi-physics nature of the problem, which involves solid and fluid species, interacting on the basis of mass balance and momentum conservation, we decide to adopt a solution strategy of the discrete problem based on iterative

This study presents a new methodology for estimating the effective properties of solids containing cracks along the inter-granular boundaries, using analytical developments and numerical simulations. The latter are based on the generation of virtual microstructures of such type obtained by superimposing a Voronoï tessellation modeling the granular network with a random dispersion of overlapping spheres

Owing to the recoverable nature of noncovalent interactions, laminated nanocomposites dominated by noncovalent interfaces can deform inelastically and generate large relative sliding between building bricks under external loading, which not only contributes to outstanding mechanical properties at the macroscale but also induces coordinated deformation behavior over several hierarchical length scales

Hydrogen precharged specimens were tested in a disc-on-disc tribometer to study the early stages of crack formation that, with cycling, eventually generate WEC or WSF. Specimens whose contact surface was intact were analysed and at subsurface numerous small transgranular cracks were found, as well as sequences of unlinked voids. Premature WEC with fine cracks and little microstructural alteration volume

Molecular dynamics (MD) of polycarbonate is used to understand the molecular bases of ratcheting and sensitivity to variation in polymer chain lengths. We find that ratcheting is almost insensitive to molecular weight in mono-disperse systems, but not in poly-disperse systems. MD-to-continuum measures show that molecular motions of short chains in poly-dispersed systems are distinct from longer-sized

An empirical bi-parametric model based on the Vickers hardness HV and a proper microstructural length parameter, l, was proposed to estimate the fully reversed threshold-Stress Intensity Factor for long cracks of wrought and additively manufactured (AM) alloys. In this paper, the model has been extended to positive load ratios (R ≅ 0 and ≅ 0.5). Afterwards, experimental results generated from testing