I. I. Cuesta

• University of Burgos

Prediction of hydrogen embrittlement requires a robust modelling approach and this will foster the safe adoption of hydrogen as a clean energy vector. A generalised computational model for hydrogen embrittlement is here presented, based on a phase field description of fracture. In combination with Part I of this work, which describes the process of...

Hydrogen threatens the structural integrity of metals and thus predicting hydrogen-material interactions is key to unlocking the role of hydrogen in the energy transition. Quantifying the interplay between material deformation and hydrogen diffusion ahead of cracks and other stress concentrators is key to the prediction and prevention of hydrogen-a...

Additive Manufacturing (AM) appears as a very interesting alternative to conventional production routes for alloys and metals, thanks to the fact that at the end of printing, the final product is obtained directly. The present article looks for the inclusion of duplex stainless steel 2205 (DSS-2205) in the commercial catalog of steels utilized in p...

In order to ensure casting simulation plausibility, as requested in wind certifications, its default mechanical property prediction is evaluated based on results tested from wind structural castings made in furan no-bake resin systems. Through a standard definition of pre-process parameters and the default post-process provided by commercial softwa...

Additive manufacturing (AM) of metallic materials is increasingly being adopted in numerous sectors, such as biomedicine, aerospace or automotive industries, due to its versatility in the creation of complex geometries and the minimisation of material waste when compared to traditional subtractive methods. In order to ensure a reliable operation of...

Ti-6Al-4V is a titanium alloy with excellent properties for lightweight applications and its production through Additive Manufacturing processes is attractive for different industrial sectors. In this work, the influence of mechanical properties on the notch fracture resistance of Ti-6Al-4V produced by Selective Laser Melting is numerically investi...

The influence of internal hydrogen on the mechanical behavior of the 42CrMo4 steel grade has been evaluated by means of internal pressure fracture tests performed on hydrogen precharged notched cylindrical specimens. The notched cylindrical specimens were precharged in a 1M H2SO4 solution + 0.25 g/l As2O3 for 3h and 1.2 mA/cm². Thereupon, hydraulic...

Structural components design in the wind sector is based on international guidelines that in some cases could be ambiguous and excessively conservative. This article reviews the state of the art regarding allowable data of material that must be provided during the different design steps of large structural castings for gearboxes in the wind sector....

Ti-6Al-4V is a titanium alloy with excellent properties for lightweight applications and its production through Additive Manufacturing processes is attractive for different industrial sectors. In this work, the influence of mechanical properties on the notch fracture resistance of Ti-6Al-4V produced by Selective Laser Melting is numerically investi...

Fatigue crack propagation initiated from internal defects is a typical mechanism observed in high cycle fatigue (HCF) and very high cycle fatigue (VHCF) of cylindrical tensile specimens subjected to uniaxial cyclic loads. To study the fatigue crack propagation of these embedded cracks by means of a fracture mechanics approach, solutions for the Str...

Hot Isostatic Pressing (HIP) is a thermomechanical post-processing technique widely used in Additive Manufacturing parts to reduce internal defects, such as entrapped-gas-pores or lack-of-fusion, which have a great influence on the mechanical and fatigue properties of the material. In this paper, the effect of a non-conventional HIP-cycle on the fa...

The fatigue crack growth in round bars initiated from internal defects leads to the formation of a circular crack pattern usually so-called fish-eye. This failure mechanism is found in the current additive manufacturing techniques in which internal defects, such as pores or lack of fusion, are the main cause of fatigue crack initiation. Moreover, t...

In this paper, stress-intensity factor solutions are presented for an embedded elliptical crack in a round bar subjected to tensile load. The stress-intensity factors (SIF) are presented in a tabulated form and were obtained from three-dimensional finite-element analyses of this crack configuration. The solutions provide the stress-intensity factor...

Hydrogen assisted fracture near welds is the result of a combination of microstructural changes and the accumulation of hydrogen. With the aim of predicting local hydrogen concentrations, hydrogen redistribution near a crack tip is simulated using a Boundary Layer approach and diffusion modelling is modified by trapping phenomena. The simulated non...

The determination of residual stress distributions in cold-formed members is revisited considering both experimental and numerical methodologies. Destructive, semi-destructive and non-destructive techniques are reviewed with special emphasis on sectioning, hole drilling and X-ray diffraction; the particularities of each procedure on cold-formed sec...

Titanium alloys are widely employed in aerospace and automotive industries where lightweight applications are required. Additive Manufacturing (AM) processes have been proposed in order to reduce material waste and optimise mechanical properties. In addition, throughout these manufacturing processes and during service life, hydrogen uptake is expec...

In this paper Small Punch Tests (SPT) are used to determine the mechanical properties of the heat affected zone (HAZ) of CrMoV welded joints and to evaluate the embrittlement caused by the presence of internal hydrogen. Hydrogen permeation tests were carried out to determine the effective diffusion coefficients of the different regions of welded jo...

Thick adhesive layers have potential structural application in ship construction for the joining of a composite superstructure to a steel hull. The purpose of this study is to develop a mechanics model for the adhesive fracture of such lap joints under shear loading. Modified Thick-Adherend-Shear-Test (TAST) specimens made from a MMA-based adhesive...

There is a need for numerical models capable of predicting local accumulation of hydrogen near stress concentrators and crack tips to prevent and mitigate hydrogen assisted fracture in steels. The experimental characterisation of trapping parameters in metals, which is required for an accurate simulation of hydrogen transport, is usually performed...

There is a need for numerical models capable of predicting local accumulation of hydrogen near stress concentrators and crack tips to prevent and mitigate hydrogen assisted fracture in steels. The experimental characterisation of trapping parameters in metals, which is required for an accurate simulation of hydrogen transport, is usually performed...

Failures attributed to hydrogen embrittlement are a major concern for metals so a better understanding of damage micro-mechanisms and hydrogen diffusion within the metal is needed. Local concentrations depend on transport phenomena including trapping effects, which are usually characterised by a temperature-programmed desorption method often referr...

Failures attributed to hydrogen embrittlement are a major concern for metals so a better understanding of damage micro-mechanisms and hydrogen diffusion within the metal is needed. Local concentrations depend on transport phenomena including trapping effects, which are usually characterised by a temperature-programmed desorption method often referr...

The electrochemical permeation test is one of the most used methods for characterising hydrogen diffusion in metals. The flux of hydrogen atoms registered in the oxidation cell might be fitted to obtain apparent diffusivities. The magnitude of this coefficient has a decisive influence on the kinetics of fracture or fatigue phenomena assisted by hyd...

The electrochemical permeation test is one of the most used methods for characterising hydrogen diffusion in metals. The flux of hydrogen atoms registered in the oxidation cell might be fitted to obtain apparent diffusivities. The magnitude of this coefficient has a decisive influence on the kinetics of fracture or fatigue phenomena assisted by hyd...

The shear strength of a pre-cracked sandwich layer is predicted, assuming that the layer is linear elastic or elastic-plastic, with yielding characterized by either J2 plasticity theory or by a strip-yield model. The substrates are elastic and of dissimilar modulus to that of the layer. Two geometries are analysed: (i) a semi-infinite crack in a sa...

The shear strength of a pre-cracked sandwich layer is predicted, assuming that the layer is linear elastic or elastic-plastic, with yielding characterized by either J2 plasticity theory or by a strip-yield model. The substrates are elastic and of dissimilar modulus to that of the layer. Two geometries are analysed: (i) a semi-infinite crack in a sa...

Assuming that hydrogen enhances localised plasticity, as one of the leading mechanisms proposed in the literature, the void growth and coalescence are modified by local softening and ductile failure features depend on hydrogen accumulation. It is anticipated that strain rate plays an important role in hydrogen-informed void mechanisms, however, cou...

Additive manufacturing is becoming increasingly popular in academia and industry. Accordingly, there has been a growing interest in characterizing 3D printed samples to determine their structural integrity behaviour. We employ the Essential Work of Fracture (EWF) to investigate the mechanical response of polymer sheets obtained through additive man...

Additive manufacturing is becoming increasingly popular in academia and industry. Accordingly, there has been a growing interest in characterizing 3D printed samples to determine their structural integrity behaviour. We employ the Essential Work of Fracture (EWF) to investigate the mechanical response of polymer sheets obtained through additive man...

Due to an error introduced during the production process, Fig. 11 appeared incorrectly in the original publication of this article. It appears correctly here.

In recent years, the pre-notched or pre-cracked small punch test (P-SPT) has been successfully used to estimate the fracture properties of metallic materials for cases in which there is not sufficient material to identify these properties from standard tests, such as CT or SENB specimens. The P-SPT basically consists of deforming a pre-notched mini...

The Hole-Drilling method is a semi-destructive technique useful for obtaining residual stress distributions by drilling and measuring relieved strains. The standard for this method, i.e., ASTM E837 – 13a, is based on the Integral Method and facilitates obtaining the coefficient matrices required to solve the inverse problem and to calculate the res...

In recent years, the pre-notched or pre-cracked small punch test (P-SPT) has been successfully used to estimate the fracture properties of metallic materials for cases in which there is not sufficient material to identify these properties from standard tests, such as CT or SENB specimens. The P-SPT basically consists of deforming a pre-notched mini...

The introduction of compressive residual stresses, e.g. by means of an autofrettage process, is a common strategy in industry for the improvement in fatigue life of high-pressure vessels. The application of autofrettage process in a vessel, storing hydrogen at 70 MPa, is evaluated here. Compressive stresses make difficult the entry of hydrogen in t...

Metals and alloys, especially high-strength steels and nickel-based alloys, are damaged by the phenomenon known as hydrogen embrittlement. Although these types of hydrogen-assisted fractures have been well documented, micro-mechanisms are not yet completely understood. Strain localization and decohesion seem to be usually accelerated by hydrogen, w...

With the increasing interest in the use of hydrogen as an energy carrier, a better understanding of hydrogen embrittlement affecting materials is required. In addition, hydrogen tanks suffer fatigue processes due to stress variation in filling and refuelling operations. In this context, in order to simulate hydrogen transport inside the material, a...

Ductile damage modeling within the Small Punch Test (SPT) is extensively investigated. The capabilities of the SPT to reliably estimate fracture and damage properties are thoroughly discussed and emphasis is placed on the use of notched specimens. First, different notch profiles are analyzed and constraint conditions quantified. The role of the not...

One important topic in the application of the Small Punch Test (SPT) is to analyse its viability for the determination of the fracture properties of a material. This article describes three different approaches using pre-notched SPT specimens (p-SPT): the first one is based on the concept of crack tip opening displacement (CTOD), the second is base...

The aim of this paper is to demonstrate the applicability of the Small Punch Test (SPT) in the mechanical characterization of polymers, following previous achievements in metallic materials. For this purpose, different polymers with a wide variation of tensile properties were examined. The applicability of this type of test to characterize polymeri...

The use of pre-cracked small punch creep test specimens (p-SPCT) is analyzed in this paper as an alternative method to obtain the Creep Crack Initiation (CCI) time in those cases where there is not enough material to use CT specimens. The material selected was an AZ31B magnesium alloy. The geometry of the specimens used was 10 × 10 mm square with a...

Simulations of Hydrogen Assisted Cracking (HAC) in metals and alloys include hydrogen concentration as a crucial variable. With this objective, phenomenological diffusion models that consider chemical potential gradients as the driving force for diffusion are described. Equations are then modified to include the influence of the stress-strain state...

In recent decades, one of the most widely used techniques to characterize the fracture properties of polymer sheets under plane stress conditions has been the essential work of fracture (EWF). This method allows the testing of different pre-cracked specimens although those most commonly tested are the deeply double edge notched tensile specimens (D...

In the present study, a new small punch test (SPT) methodology has been used to analyse the effect of hydrogen embrittlement on the tensile properties of three different grades of CrMoV steel: the base metal (CrMoV-1), weld metal (CrMoV-2) and this same weld metal subjected to an intermediate heat treatment (CrMoV-3). SPT results were compared with...

It is vital to control fatigue life in different industrial sectors, and to improve this, surface treatments are usually used. Some of the most important surface treatments are Shot Peening (SP), Laser Shock Peening (LSP) or Deep Rolling (DR), which are used to improve the surface properties and resistance to cyclic loading of the components. The i...

Modelling of hydrogen embrittlement in order to prevent engineering failures requires a characterization of transport phenomena in the bulk metallic as a first step. Interstitial solid state diffusion can be described as a random phenomenon, however there will be also some drift forces biasing this behaviour so a modification in Fick's laws is need...

In recent decades, one of the non-standard tests that has been consolidated as a viable alternative in those cases where there is not sufficient material to carry out standard tests is the small punch test. This test basically consists of deforming a miniature specimen using a high strength punch. It is possible for this miniature specimen to have...

En la actualidad existen diferentes técnicas numéricas con las que reproducir el comportamiento hasta fractura de una probeta o componente. Una de las más empleadas es el uso de modelos de daño dúctil que incluyan la nucleación, crecimiento y coalescencia de microhuecos. Dichos modelos están gobernados por una serie de parámetros que es necesario c...

The fracture characterization under plane-stress conditions in polymer sheets in recent decades has usually been done through the application of the essential work of fracture (EWF) method. However, when deeply double-edged, notched tensile standard specimens cannot be obtained, the use of alternative small pieces, such as prenotched miniature spec...

Nowadays, the small punch test is used successfully to characterize the mechanical behaviour of materials especially in those cases in which an insufficient amount of material is available to carry out standard tests. This test basically consists of deforming a miniature specimen whose edges are firmly gripped by a die. But, what happens if the lev...

The small punch test (SPT) is very convenient for estimating tensile mechanical properties, being the estimation of fracture toughness still a controversial subject of debate. One of the new strategies developed is the use of notched specimens. In this paper, two different grades of CrMoV steels were employed to analyse the evolution of the notch m...

Nowadays, there are standards for determining the creep-fracture properties of a material. However, a sufficient amount of material to be tested is usually required, something that is not always possible or convenient. In certain cases where not enough material is available for carrying out conventional tests to determine these properties of the ma...

This paper aims to implement control charts used in the statistical control of production processes as a new way to improve teaching, so that they can detect any differences in academic outcomes of students or in a subject with respect to its class planning. In particular, the steps to follow for the use of such control charts in monitoring the rat...

By means of the experimental analysis of two structural steels, one with a ductile behaviour and the other one with brittle behaviour, this paper compares the results obtained by means of small punch test (SPT) performed on notched samples with those obtained in standard fracture toughness tests, in order to obtain a relationship between them and t...

In recent years, the pre-notched or pre-cracked small punch test (P-SPT) has been successfully used to estimate the fracture properties of metallic materials in those cases where there is not enough material to identify these properties from standard tests, such as the CT or SENB specimens. The P-SPT basically consists of deforming a pre-notched mi...

Creep tests on a small scale have the potential to be used without significant removal of material or in areas where the available material is limited. In this paper an extension of the modified Monkman-Grant model for the prediction of the creep rupture time using Small Punch Creep Tests (SPCT) is investigated. This test basically consists of punc...

In this paper, the use of pre‐cracked small punch test (p‐SPT) miniature specimens to obtain the fracture parameters of a material is presented. The geometry of the specimens used was square of 10 × 10 mm with a thickness of 0.5 mm. An initial crack‐like notch was created in the SPT specimens by means of a laser micro‐cutting technique. In order to...

The use of stamped aluminium alloy components in the automotive industry is commonplace nowadays. To design these components correctly, it is necessary to know how the mechanical properties of sheet metals change when the material is deformed, generally under biaxial strain. In this paper, the influence of the pre-deformation on yield strength in a...

One of the requirements of the European Higher Education Space is the students individualized monitoring and continuous evaluation, which requires an increase in time devoted to teaching. A possible solution for better management of time is the integration of new technologies into teaching-learning processes. This article discusses the acceptance d...

The fatigue results of a high-pressure die cast of AZ91D magnesium alloy revealed the presence of different types of casting defects, which account for the large scattering in the number of cycles until failure. In this paper, this magnesium alloy has been analysed, and in an effort to reproduce the same surface and material conditions exhibited in...

Currently, learning objects are a mainstay in higher education. It is essential to establish uniform criteria of formats that are common to all the subjects included in a study plan, especially in interuniversity studies, in order to maximize the employability of said learning resources.

The parts and components manufactured by stamping processes are accompanied by high plastic strain levels that generate residual stress and changes in the mechanical behaviour of the material in areas of high strain. An accurate design of these components requires a thorough understanding of these initial plastic strains as a result of the stamping...

In a previous research paper, a new methodology was developed to estimate the fracture toughness of 15.5PH stainless steel, one that combines the Failure Assessment Diagram (FAD), a procedure for evaluating the structural integrity of cracked components, along with the load–displacement curve obtained from pre-cracked specimens using the Small Punc...

Nowadays, pre-cracked Small Punch Tests (P-SPT) are used in those cases where there is not enough material for conducting conventional tests. In this paper, P-SPT has been used to determine the fracture properties of the 15.5PH steel, using the micromechanical model, developed by Gurson-Tvergaard-Needleman (GTN). The effect of variation of damage p...

Small Punch Test (SPT) is a feasible alternative to determine the mechanical properties in those cases where there is not enough material for conducting conventional tests. Nowadays, there is a great interest in using this test on precracked specimens (P-SPT) in order to determine the fracture properties of the material, as well. In the case of duc...

Nowadays, there are standards for determining the mechanical and fracture properties of a material. However, these standards require a sufficient amount of material to be tested, something that is not always possible or convenient. In those cases where there is not enough material for conducting conventional tests to determine these properties of t...

In order to calculate the fatigue life of cylinders subjected to internal pressure using the fracture mechanics approach, the stress intensity factors (SIFs) for internal semi-elliptical cracks are needed. Nowadays, the most accurate procedure for fatigue life calculation consists in starting from a postulated internal semi-elliptical crack and upd...

The Failure Assessment Diagram (FAD) is a procedure for evaluating the structural integrity of cracked components. The component’s failure conditions (load and crack size) are based on the material fracture properties (Kmat) considering its plastic behavior. In this paper, a new methodology that combines the FAD approach and the load–displacement c...

In this paper, the modeling of a crack propagating through a finite element mesh under mixed-mode conditions was studied. The numerical procedure to perform automatically the crack propagation is widely explained. Crack tip stress intensity factors were estimated in order to determine the crack propagation direction, by using the maximum principal...

The objective of the final small punch test (SPT) is to determine the fracture properties of materials, such as fracture toughness, when not enough material is available for the conduct of conventional fracture tests. The damage model developed by Gurson, and subsequently modified by Tvergaard and Needleman (GTN), allows for the numerical simulatio...

The wire winding of high pressure vessels is a technique usually applied to introduce initial compressive stresses in the inner core of the vessel, with the aim to improve the fatigue life under cyclic pressure conditions. In this work, the procedure followed to calculate the number of design cycles is presented, using the fracture mechanics approa...

Photoelasticity has been used for decades in the experimental measurement of stresses and strains. As data-acquisition techniques only identify the differences between principal stresses and strains, stress-separation techniques exist to identify each of their values separately. A variety of techniques have been developed since the early days of ph...

In this work, pre-cracked Small Punch Test (SPTspecimens have been used with the aim to obtain the fracture properties of the 15.5PH high strength stainless steel. SPT is a mechanical testing method in which a small square or disk shaped sample is clamped in a die and punched until fracture with a spherical indenter. The methodology presented in th...

The small punch test (SPT) is very useful in those situations where it is necessary to use small volumes of material. The aim of this paper is to create and validate a methodology for the determination of the mechanical and damage properties of steels from the load-displacement curve obtained by means of SPTs. This methodology is based on the inver...

This paper is focused on determining the plastic collapse load of vessels which consist of an inner cylinder prestressed by a surrounding winding. This winding consists of a wire helically wound edge-to-edge in pretension in a number of layers around the outside of the inner cylinder. As a consequence, compression stresses are introduced in the cyl...

Superior. C/Villadiego s/n, 09007, Burgos. RESUMEN El presente trabajo tiene como objetivo principal la creación y validación de una metodología para la determinación de los parámetros elastoplásticos y de daño que definen el comportamiento del material, a partir de la interpretación y evaluación de la curva carga-desplazamiento obtenida en el ensa...

RESUMEN Con el objeto de utilizar el ensayo Small Punch (SPT) para obtener la tenacidad de un material en aquellos casos en los que no se disponga de cantidad suficiente como para poder determinar la misma mediante ensayos normalizados, en el presente trabajo se presenta el procedimiento utilizado para estimar el valor de la integral J de una probe...

RESUMEN El diagrama FAD (Failure Assessment Diagram) es un procedimiento para la evaluación de la integridad estructural de componentes fisurados. Las condiciones de fallo de la geometría, bajo unas condiciones de carga y fisura dadas, están basadas en las propiedades a fractura del material (K mat) teniendo en cuenta el comportamiento plástico del...