Frattura ed Integrità Strutturale 2021-12-27T14:49:46+00:00 Francesco Iacoviello Open Journal Systems <p>Frattura ed Integrità Strutturale (Fracture and Structural Integrity) is the International Journal of the Italian Group of Fracture (ISSN 1971-8993). It is an open-access journal published online every three months (January, April, July, October). <br />Frattura ed Integrità Strutturale encompasses the broad topic of structural integrity, which is based on the mechanics of fatigue and fracture and is concerned with the reliability and effectiveness of structural components. The aim of the Journal is to promote works and researches on fracture phenomena, as well as the development of new materials and new standards for structural integrity assessment. The Journal is interdisciplinary and accepts contributions from engineers, metallurgists, materials scientists, physicists, chemists, and mathematicians. The Journal is completely free of charge, both for Readers and for Authors (no APC).</p> <p><strong>More details:</strong></p> <p>- The Journal is financially supported by the <a href="">Italian Group of Fracture (IGF)</a> and by crowdfunding. It is completely free of charge both for readers and for authors. Neither processing charges nor submission charges are required.</p> <p>- Papers can be published only after a preliminary plagiarism/autoplagiarism check and a blind peer-review process (two reviewers, at least). More than one reviewing rounds are possible.</p> <p>- The Journal is well indexed (e.g., Scopus, since 2012, and WoS, since 2015).</p> <p>- All the papers are published with their Visual Abstracts (2 minutes max videos with the "cores" of the papers). All the Visual Abstracts are available both in a dedicated <a href="">YouTube channel</a> and in an "on demand" page (<a href="">LINK</a>). All the issues are also published in a browsable version (<a href="">LINK</a>).</p> The critical influence of some “tiny” geometrical details on the stress field in a Brazilian Disc with a central notch of finite width and length 2021-11-22T17:28:25+00:00 Stavros K Kourkoulis Christos Markides Ermioni Pasiou Andronikos Loukidis Dimos Triantis <p>The role of some geometrical characteristics of the notches ma­chined in circular discs, in order to determine the mode-I fracture tough­ness of brittle materials, is discussed. The study is implemented both analyti­cally and numerically. For the analytic study advantage is taken of a recently intro­duced solution for the stress- and displacement-fields developed in a finite disc with a central notch of finite width and length and rounded corners. The vari­ation of the stresses along strategic loci and the deformation of the peri­me­ter of the notch obtained analytically are used for the calibration/validation of a flexible nu­mer­ical model, which is then used for a parametric investiga­tion of the role of geometrical features of the notched disc (thickness of the disc, length and width of the notch, radius of the rounded corners of the notch). It is con­cluded that the role of the width of the notch is of critical im­port­ance. Both the ana­lytic and the numerical studies indicate definitely that ignoring the ac­curate geo­metric shape of the notch leads to erroneous results concerning the actual stress field around the crown of the notch. Therefore, it is possible that misleading values of the fracture toughness of the material of the disc may be obtained.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Stavros K Kourkoulis, Christos Markides, Ermioni Pasiou, Andronikos Loukidis, Dimos Triantis Novel 2D strain-rate-dependent lamina-based and RVE/phase-based progressive fatigue damage criteria for randomly loaded multi-layer fiber-reinforced composites 2021-11-22T16:29:56+00:00 M. Shariyat <p>Two implicit progressive fatigue damage models that rely on new equivalent-damage and equivalent-stress criteria are presented for the prediction of various failure modes of the composites. The criteria are coupled with lamina-based and representative-volume-element-based damage progression approaches. The common concepts of residual strength and residual stiffness are revisited and modified. A fatigue life assessment algorithm that incorporates the strain-rate-dependence of the fatigue strengths and stiffnesses, and random and asynchronous changes of the stress components, distinct mean values, and phase shifts of the stress components is employed. New ideas and new post-processing procedures are employed in the current research. It is the first time that the significant impacts of the strain-rate-dependence of the properties of the composites on stress and fatigue life analyses are investigated. Results of the proposed fatigue criteria are first implemented to a composite plate with a complex lamination scheme under a random transverse load and the predicted fatigue lives are verified by the experimental results. Then, these criteria are implemented to a composite chassis frame of an SUV car under realistic random road inputs and the theoretical results are verified by the experimental results. Results confirm the significant role of the strain-rate-dependence effects on the fatigue lives.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 M. Shariyat Influence of the interphase between laser-cladded metal layer and steel substrate on fatigue propagation of a short edge crack 2021-11-24T07:30:45+00:00 Lucie Malikova Pavel Doubek Petr Miarka Stanislav Seitl <p>Laser cladding is a relatively new technology how to combine properties of various materials. Thus, bi-material interfaces are presented in real structures and can affect the fatigue crack propagation. A cracked bar subjected to pure tensile loading is numerically simulated in this work in order to analyze the effect of the interphase layer between the cladded metal layer and the steel substrate on crack growth in the surface layer. Particularly, the influence of various Young’s modulus of the interphase on the stable/unstable edge crack propagation is assessed. Moreover, the number of cycles necessary for achievement of the defined critical crack length is calculated and it is summarized that knowledge of elastic properties of the thin interphase is crucial for fracture and fatigue analyses.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Lucie Malikova, Pavel Doubek, Petr Miarka, Stanislav Seitl Crack paths in multiaxial fatigue of C45 steel specimens and correlation of lifetime with the thermal energy dissipation 2021-11-25T13:19:21+00:00 Daniele Rigon Filippo Berto Giovanni Meneghetti <p>The work reports the observed fatigue damage of C45 steel specimens tested in a previous work under multiaxial loading conditions and its relationship with the thermal energy dissipation which has been used in the last decades to estimate the uniaxial fatigue behavior of metals. For this purpose, fatigue data relevant to thin-walled samples made of quenched and tempered C45 steel tested under completely reversed combined axial and torsional cyclic loadings with different biaxiality ratios and phase-shift angles have been analysed. The analyses of crack paths at the initiation point of failure were performed after a 50% stiffness loss that corresponded to a crack size ranging from 7 to 15 mm; afterwards, the characteristic crack paths of each loading condition were analysed by using a digital microscope to identify the orientation of the crack initiation plane. After having broken all fatigue tested specimens under static tensile loading, the fracture surfaces were inspected close to the crack initiation point using a digital microscope. Despite the stress states and fatigue damage mechanisms dependent on the load condition, the Q parameter applied to the present experimental results proved to correlate all multiaxial fatigue test results in a single fatigue scatter band.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Daniele Rigon, Filippo Berto, Giovanni Meneghetti Damage Detection in Structural Health Monitoring using Hybrid Convolution Neural Network and Recurrent Neural Network 2021-11-03T14:27:34+00:00 Thanh Bui-Tien Dung Bui-Ngoc Hieu Nguyen-Tran Lan Nguyen-Ngoc Hoa Tran-Ngoc Hung Tran-Viet <p>The process of damage identification in Structural Health Monitoring (SHM) gives us a lot of practical information about the current status of the inspected structure. The target of the process is to detect damage status by processing data collected from sensors, followed by identifying the difference between the damaged and the undamaged states. Different machine learning techniques have been applied to attempt to extract features or knowledge from vibration data, however, they need to learn prior knowledge about the factors affecting the structure. In this paper, a novel method of structural damage detection is proposed using convolution neural network and recurrent neural network. A convolution neural network is used to extract deep features while recurrent neural network is trained to learn the long-term historical dependency in time series data. This method with combining two types of features increases discrimination ability when compares with it to deep features only. Finally, the neural network is applied to categorize the time series into two states - undamaged and damaged. The accuracy of the proposed method was tested on a benchmark dataset of Z24-bridge (Switzerland). The result shows that the hybrid method provides a high level of accuracy in damage identification of the tested structure.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Thanh Bui-Tien, Dung Bui-Ngoc, Hieu Nguyen-Tran, Lan Nguyen-Ngoc, Hoa Tran-Ngoc, Hung Tran-Viet Numerical study of TRIP transformation in 35NCD16 steel-effects of plate orientation and some criteria 2021-12-01T06:26:13+00:00 Mounir Gaci Fedaoui Kamel Lazhar Baroura Amar Talhi <p>This study aims to analyze the effect of thermo mechanical coupling damage in the presence of a phase change (austenite/martensite) in 35NCD16 steel. The impact of increasing mechanical traction load, accompanied by a martensitic transformation on the scale of a single grain with boundary has been studied. The prediction transformation of induced plasticity (TRIP) was evaluated by taking into account the following parameters: twenty shear directions of the martensitic plates, two values of the shear deformation of the martensitic plates, energetic and thermodynamics criteria for getting in order the transformation of the martensitic plates, elastoplastic behavior of the two areas in the first case (martensitic plate and grain boundary) and elastic behavior for the grain boundary in the second case. The numerical calculation is carried out using the finite element method (FEM), implemented in the Zebulon calculation code. The developed approach is validated using the available experimental results reported in the literature. The numerical results showed that the estimation of TRIP given by the energetics criteria with the values of the shear deformation (<em>γ<sub>0</sub> </em>= 0.16) are closer to the experiment results.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Mounir Gaci, Fedaoui Kamel, Lazhar Baroura, Amar Talhi Self-healing mortar using different types, content, and concentrations of bacteria to repair cracks. 2021-10-29T05:28:42+00:00 Mohamed Ahmed Refat El-Mahdy Ahmed ELShami Mohamed Yousry Elshikh Seleem Saleh Elsayed Ahmad <p>The creation of cracks, which are the most common cause of structural failure, has a significant impact on the structure's strength and durability. As a result, effective repair and maintenance are vital and unavoidable for treating any of these issues. Self-healing mortar holds promising benefits for reducing the cost of repair as cracks are autonomously repaired without any human intervention. This study investigated the effect of bacteria type, bacteria content, bacteria concentration, and nutrient type on the properties of the self-healing mortar. Three types of bacteria, Bacillus sphaericus, Bacillus Megaterium, and Bacillus subtilis encapsulated in calcium alginate beads, were introduced into the mortar. Two concentrations of bacteria, 2× 10<sup>8</sup> and&nbsp;&nbsp; 2× 10<sup>9</sup> Colony Forming Units per milliliter, and different percentages of bacteria of cement weight were selected for the study. In addition, calcium lactate and calcium acetate were used at 0.5% of cement weight as nutrition for bacteria. Tests were performed for compressive strength, bending strength, SEM, EDX, and TGA/DTG. The results show a significant development in the mechanical behaviour of mortar, especially with Bacillus Megaterium using a 2.5% bacterial proportion with a concentration 2× 10<sup>9</sup> CFU/ml. This can be related to the filling of voids and cracks in microbial mortar by calcite, which was confirmed by SEM and EDX.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Mohamed.A.R. Elmahdy, A.A. ELShami, El-Shikh M. Yousry, Seleem S. E. Ahmad A probabilistic fatigue crack growth life approach to the definition of inspection intervals for railway axles 2021-11-22T12:38:34+00:00 C. Mallor S. Calvo J.L. Nuñez R. Rodriguez-Barrachina A. Landaberea <p>Different options that rely on fracture mechanics are currently used in engineering during the design and assessment of components. One of the most important aspects is the time taken for a crack to extend to its critical size. If this time is long enough, a design concept based on inspection intervals can be applied, as is it the case of a railway axle component. To define inspection intervals that ensure the continuous and safe operation of a damage-tolerant railway axle, a reliable estimation of its fatigue crack growth life is required. Due to the uncertainties involved in the fatigue process, inspections must be devised not only considering the uncertainties in the performance of the inspection technique, but also based on a probabilistic lifespan prediction. From this premise, this paper presents a procedure for determination of inspection intervals that uses a conservative fatigue crack growth life estimation based on the lifespan probability distribution. A practical example to illustrate the reliability-based inspection planning methodology in a railway axle under random bending loading is given. The inspection intervals are further assessed in terms of overall probability of detecting cracks in successive inspections and in terms of probability of failure, considering the probability of detection curve of the non-destructive testing technique. The procedure developed provides recommendation for the definition of inspection intervals and associated inspection techniques.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 C. Mallor, S. Calvo, J.L. Nuñez, R. Rodriguez-Barrachina, A. Landaberea Damage accumulation near the cold-expanded hole due to high-cycle fatigue by crack compliance method 2021-10-19T08:15:05+00:00 Sviatoslav Eleonsky Yuri Matvienko Vladimir Pisarev Michael Zajtsev <p>The novel destructive method is implemented for quantitative assessment of fatigue damage accumulation in the stress concentration zone accompanied by residual stress due to cold expansion of the through-thickness hole. Damage accumulation is reached by preliminary cyclic loading of plane specimens with cold-expanded holes. Narrow notches, emanating from the hole edge at different stages of high-cycle fatigue, serve to manifest a damage level. These notches are inserted without applying external load. Deformation response to local material removing, caused by pure residual stress influence, is measured by electronic speckle pattern interferometry (ESPI) in terms of in-plane displacement components. Normalized values of the notch mouth open displacement (NMOD), in-plane displacement component at the initial point of the notch acting in the notch direction (<em>U</em><sub>0</sub>)<strong>, </strong>in-plane displacement component at the final point of the notch acting in the notch direction (<em>U</em><sub>1</sub>) and the stress intensity factor (SIF) are used as current damage indicators. Numerical integration of curves, describing an evolution of each fracture mechanics parameter over lifetime, produces the damage accumulation function in an explicit form. It is established that all four fracture mechanics parameters give very close results.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Sviatoslav Eleonsky, Yuri Matvienko , Vladimir Pisarev, Michael Zajtsev Methodology of hydrogen embrittlement study of long-term operated natural gas distribution pipeline steels caused by hydrogen transport 2021-10-17T17:24:11+00:00 Hryhoriy Nykyforchyn Olha Zvirko Myroslava Hredil Halyna Krechkovska Oleksandr Tsyrulnyk Oleksandra Student Leonid Unigovskyi <p>A methodology of experimental research on hydrogen embrittlement of pipe carbon steels due to the transportation of hydrogen or its mixture with natural gas by a long-term operated gas distribution network is presented. The importance of comparative assessments of the steel in the as-received and operated states basing on the properties that characterize plasticity, resistance to brittle fracture and hydrogen assisted cracking is accentuated. Two main methodological peculiarities are pointed out, (i) testing specimens should be cut out in the transverse direction relative to the pipe axis; (ii) strength and plasticity characteristics should be determined using flat tensile specimens with the smallest possible thickness of the working part. The determination of hydrogen concentration in metal, metallographic and fractographic analyses have been supplemented the study. The effectiveness of the proposed methodology has been illustrated by the example of the steel research after its 52-year operation.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Hryhoriy Nykyforchyn, Olha Zvirko, Myroslava Hredil, Halyna Krechkovska, Oleksandr Tsyrulnyk, Oleksandra Student, Leonid Unigovskyi Effect of varying silica-limestone sand fines on the physical-mechanical performance of concrete 2021-12-05T17:01:30+00:00 Tarek Djedid Mohammed Mani Abdelkader Ouakouak Abdelhamid Guettala <p>The use of crushed limestone sand in the concrete industry will be quite possible and imperative for environmental reasons. Many researchers around the world have found that concrete based on 50% substitution of river sand by limestone sand gives better physico-mechanical characteristics. The main objective of this investigation is to search for an optimal percentage of silica-limestone fines resulting from the substitution of half in quantity of alluvial sand by crushed limestone sand in ordinary concrete. The proportions of fines that were tested in this work are 6%, 8%, 10%, 12% and 14%.</p> <p>The obtained results revealed that concrete based on silica-limestone sand and containing 14% of the same type of fines strongly improves the different mechanical strengths and participates in the reduction of 10% and 13%, of the coefficient of capillary absorption and of the porosity accessible to water, respectively, compared to the control concrete. In addition, good statistical relationships between the studied parameters were also found</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Tarek Djedid, Mohammed Mani, Abdelkader Ouakouak, Abdelhamid Guettala Finite element modeling of flexural behavior of reinforced concrete beams externally strengthened with CFRP sheets 2021-10-10T14:48:10+00:00 Mahmoud Madqour Khalid Fawzi Hilal Hassan <p>In this research, the finite element method is used to develop a numerical model to analyse the effect of the external strengthening of reinforced concrete beams by using carbon Fiber Reinforced Polymer (CFRP) sheets. A finite element model has been developed to investigate the behavior of RC beams strengthened with CFRP sheets by testing nineteen externally simple R.C. beams, tested under a four-point load setup until failure. Various CFRP systems were used to strengthen the specimens.&nbsp; The numerical results using the (ANSYS workbench v.19.1) were calibrated and validated with the experimental results.&nbsp; The research results indicate a significant improvement in the structural behavior of the specimens strengthened using CFRP sheet systems. Then the validated model investigated the effect of the width of CFRP sheets, no of layers, and CFRP size on the behavior of strengthened R.C. beams. Results of this numerical investigation show the effectiveness of increase CFRP width to improve the flexural capacity of R.C. beams. An increase in the flexural capacity up to 100 % compared to the control beam.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Mahmoud Madqour, Khalid Fawzi, Hilal Hassan Fatigue strength evaluation of PPGF35 by energy approach during mechanical tests 2021-10-20T17:06:46+00:00 Giacomo Risitano <p>Thanks to the progress of research on thermoplastic materials, the properties of composite materials have improved considerably.</p> <p>The aim of this study is the evaluation of fatigue strength of glass-fibre-reinforced polypropylene composite (PPGF35) by applying both the Risitano Thermographic Method (RTM) and the new Static Thermographic Method (STM).</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Giacomo Risitano Ductile fracture modeling of metallic materials: a short review 2021-10-04T04:11:40+00:00 Riccardo Fincato Seiichiro Tsutsumi <p>Since the end of the last century a lot of research on ductile damaging and fracture process has been carried out. The interest and the attention on the topic are due to several aspects. The margin to reduce the costs of production or maintenance can be still improved by a better knowledge of the ductile failure, leading to the necessity to overcome traditional approaches. New materials or technologies introduced in the industrial market require new strategies and approaches to model the metal behavior. In particular, the increase of the computational power together with the use of finite elements (FE), extended finite elements (X-FE), discrete elements (DE) methods need the formulation of constitutive models capable of describing accurately the physical phenomenon of the damaging process. Therefore, the recent development of novel constitutive models and damage criteria. This work offers an overview on the current state of the art in non-linear deformation and damaging process reviewing the main constitutive models and their numerical applications.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Riccardo Fincato, Seiichiro Tsutsumi Mode I stress intensity factor with various crack types 2021-11-23T17:45:26+00:00 Ehab Samir Mohamed Mohamed Soliman <p>Presence of cracks in mechanical components needs much attention, where the stress field is affected by cracks and the propagation of cracks may be occurred causing the damage. The objective of this paper is to present an investigation of crack type effect on crack severity in a finite plate. Three cases of cracked plate with three different types of cracks are assumed in this work, i.e., single edge crack, center crack and double edge crack. 2D numerical models of cases of cracked plate are established in finite element analysis (FEA), ANSYS software by adopting PLANE 183 element. Values of FEA mode I stress intensity factor SIF and Von-Mises stress at crack apex are determined for cases of cracked plate under tensile stress with different values. To identify the crack severity, the comparison of FEA results for different cracked cases is made. The comparison showed that, single edge cracked plate (SECP) has the maximum values of mode I SIF and Von-Mises stress at crack apex, i.e. the greatest crack severity is considered. Also, values of FEA Von-Mises stress at crack apex for center cracked plate (CCP) are moderate and for double edge cracked plate (DECP) are the minimum. Besides, in case of high crack lengths, it is found that, FEA results of mode I SIF in case of (CCP) are higher than those of in case of (DECP). Consequently, crack severity is considered as moderate in case of (CCP) and the minimum in case of (DECP). Empirical formulas are used to approximately estimate mode I SIF for all the case studies of cracked plate in this study and the results are compared to those of FEA. A good agreement between analytical and FEA results has been showed by this comparison.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Ehab Samir Mohamed Mohamed Soliman Analysis of workability, mechanical strength and durability by the FT-IR method of concrete based on silica-limestone sand preserved in aggressive environments 2021-11-24T05:15:06+00:00 Hima Abdelkader Tarek Djedid Mohammed Mani Abdelhamid Guettala <p>The interest of using combined sand of equal percentage of silica and limestone becomes evident in the formulation of compacted concrete in several previous works around the world, due to the formidable percentage of fines that improves the compactness and increases various mechanical resistances, which produces a more durable construction against different probable aggressions.</p> <p>This paper examines the effect of using this type of sand on workability, compressive strength, flexural strength, and splitting tensile strength. A durability test was consulted using infrared spectroscopy to assess diverse types of hydration products formed. Found results clearly show the advantages of using sand with silica and limestone grains (50/50)% in ordinary concrete infected by aggressive water. There is also an improvement in compactness, different mechanical resistances, and a reduction in the formation of harmful hydration products.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Hima Abdelkader, Tarek Djedid, Mohammed Mani, Abdelhamid Guettala Optimization of a reinforced concrete structure subjected to dynamic wind action 2021-11-02T17:16:58+00:00 Jherbyson Brito Letícia Miguel <p>This work proposes a methodology to optimize a reinforced<br>concrete structure. For this, the Whale Optimization Algorithm (WOA)<br>algorithm was used, an algorithm from the group of metaheuristic<br>algorithms, which presents an easy computational implementation. As a<br>study object, a frame structure adapted from a real reinforced concrete<br>building was used, subjected to the dynamic action of artificially generated<br>synoptic wind. The objective function is to reduce the volume of concrete<br>of the structure. For that, the dimensions of the cross-sections were used as<br>design variables, and the maximum displacement at the top imposed by the<br>ASCE / SEI 7-10 standard as a lateral constraint, as well as the maximum<br>story drift between floors. In addition to this structural optimization, it was<br>also proposed the use and optimization of Tuned Mass Dampers (TMD), in<br>different quantities, positions and parameters, improving the dynamic<br>response of the reinforced concrete building. The results show that for this<br>situation it was possible to reduce the concrete volume of the structure by<br>approximately 24%, respecting the maximum limit of displacement at the<br>top required by the standard.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Jherbyson Brito, Letícia Miguel 3D crack identification using the Nelder-Mead Simplex algorithm combined with a random generation of crack positions 2021-10-20T03:29:47+00:00 Nasreddine Amoura Hocine Kebir Abdelouahab Benzerdjeb <p>In this paper, we present a scheme for cracks identification in three-dimensional linear elastic mechanical components. The scheme uses a boundary element method for solving the forward problem and the Nelder-Mead simplex numerical optimization algorithm coupled with a low discrepancy sequence in order to identify an embedded crack. The crack detection process is achieved through minimizing an objective function defined as the difference between measured strains and computed ones, at some specific sensors on the domain boundaries. Through the optimization procedure, the crack surface is modelled by geometrical parameters, which serve as identity variables. Numerical simulations are conducted to determine the identity parameters of an embedded elliptical crack, with measures randomly perturbed and the residual norm regularized in order to provide an efficient and numerically stable solution to measurement noise. The accuracy of this method is investigated in the identification of cracks over two examples. Through the treated examples, we showed that the method exhibits good stability with respect to measurement noise and convergent results could be achieved without restrictions on the selected initial values of the crack parameters.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Nasreddine Amoura, Hocine Kebir; Abdelouahab Benzerdjeb A nonlinear concrete damaged plasticity model for simulation reinforced concrete structures using ABAQUS 2021-09-12T20:29:45+00:00 Cuong Le Thanh Hoang-Le Minh Thanh Sang-To <p>The reinforced concrete structure is typical and widely used in many fields. The behavior of concrete is nonlinear and complex. Especially, when cracks/crushings occurred in softening phase. Thus, It is important to find a damaged model of concrete with high reliability in the numerical simulation. The nonlinear behavior of concrete is the most feature used in the simulation. This characteristic is expressed through the parameters defining the yield surface, the flow potential, and the nonlinear relationship of stress-strain in the cases of tension and compression. This paper introduces a damaged concrete model that applies to the simulation of reinforced concrete structures. The reinforced concrete beam and flat slab are selected as examples to evaluate the reliability of the model presented. Through the results achieved, the model used in this paper shows high reliability and can be used to simulate more complex reinforced concrete structures.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Cuong Le Thanh, Hoang-Le Minh, Thanh Sang-To Cracking Patterns of Brittle Hemispherical Domes: an Experimental Study 2021-10-30T06:42:52+00:00 Siwen Cao Andras A. Sipos <p>Crack formation in hemispherical domes is a distinguished problem in structural mechanics. The safety of cracked domes has a long track record; the evolution of the cracking pattern received less attention. Here, we report displacement-controlled loading tests of brittle hemispherical dome specimens, including the evolution of the meridional cracking pattern. The 27 investigated specimens, 20 cm in diameter, were prepared in 3D printed molds, and their material is one of the three mixtures of gypsum and cement. We find that neither the (limited) tensile strength nor the exact value of the thickness significantly affects the statistical description of the cracking pattern, i.e., the cracking phenomenon is robust. The maximal number of the meridional cracks never exceeds seven before the fragments’ disintegration (collapse). We find that the size distribution of the fragments exhibits a lognormal distribution. The evolution is reflected in the load-displacement diagrams recorded in the test, too, as significant drops in the force are accompanied by an emergence of one or more new cracks, reflecting the brittle nature of the phenomenon. A simple, stochastic fragmentation model, in which a segment is fragmented at either in the middle or at the fourth point, fairly recovers the observed size distribution.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Siwen Cao, Andras A. Sipos Elastic-plastic fracture analysis of anisotropy effect on AA2050-T84 alloy at different temperatures: A Numerical Study 2021-09-04T05:54:53+00:00 Krishnaraja Kodancha Nagaraj Ekabote P P Revankar <p>The third generation Al-Li alloy AA2050-T84 is widely used in aircraft applications due to its lightweight and significant mechanical properties. The anisotropic variations of tensile and compression properties of this alloy at various temperatures are substantial. In this work, the variations of the J-integral, CTOD, and Plastic Zone Size (PZS) due to anisotropy of a 4-inch thick AA2050-T84 plate at ambient and cryogenic temperatures were studied numerically by using Compact Tension (C(T)) specimen. The material anisotropy resulted in fracture and constraint parameter variation for Mode-I constant load. Numerical results indicated a decrease in crack driving forces and a constraint parameter with the decrease in temperature at the plate surface and central location. Plate surface locations appear to be isotropic for both temperatures under elastic-plastic fracture analyses as crack driving forces were almost identical. The temperature effect is more on constraint as the normalized PZS values at ambient temperature have been twice that of cryogenic temperature. The isotropic behavior of a plate under sub-zero temperature makes the plate suitable for cryogenic temperature applications.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Krishnaraja Kodancha, Nagaraj Ekabote, P P Revankar On the assessment of non-metallic inclusions by part 13 of API 579 -1/ASME FFS-1 2016 2021-09-29T16:49:46+00:00 Jorge Luis González-Velázquez Ehsan Entezari Jerzy A. Szpunar <p>Improvement of nondestructive inspection techniques has allowed more frequent detection of closely spaced zones of non-metallic inclusions in pressure vessels made of low carbon steel. In the present study, closely spaced inclusions in an in-service cylindrical horizontal pressure vessel were detected by Scan-C ultrasonic inspection and considered as laminations to be assessed by Part 13 of the API 579-1/ASME FFS-1 2016 standard. The outcoming results were considered as a rejection for Level 1 assessment, and a repair or replacement of the component was required, even though it retained a significant remaining strength. Thus, an alternative procedure to assess the mechanical integrity of pressure vessels containing zones of non-metallic inclusions is proposed by adopting some criteria of the API 579-1/ASME FFS-1 Part 13 standard procedure and taking into consideration the dimensions and grouping characteristics of the inclusion zones.&nbsp; &nbsp;</p> <p>&nbsp;</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Jorge Luis González-Velázquez, Ehsan Entezari, Jerzy A. Szpunar Numerical investigation of the cold-formed I-beams bending strength with different web shapes 2021-10-15T03:21:57+00:00 Nadia Kouider Yazid Hadidane Mohammed Benzerara <p>The wide use of cold-formed sections (CFS) in the field of steel constructions, favored by the multiple advantages they offer (lightness, ease of installation, etc.), has led us to reflect on a new process for manufacture of metal beams allowing the design of very large span hangars and a reduction in instability problems. This paper presents a study of the theoretical and numerical behavior of a large span CFS beam with different webs, a solid web, a triangular corrugated web, and a trapezoidal corrugated web. These beams are stressed by a concentrated bending load at mid-span. Numerical modeling was done using the finite element software ABAQUS. The results were validated with those theoretically found, based on the effective width method adopted in standard EN1993-1-3. The load capacity and failure modes of the beams were discussed. According to numerical and analytical analysis, corrugated web beams perform better than all other sections.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Nadia Kouider, Yazid Hadidane, Mohammed Benzerara Residual Force Method for damage identification in a laminated composite plate with different boundary conditions 2021-08-28T08:23:04+00:00 Amar Behtani Samir Tiachacht Tawfiq Khatir Samir Khatir Magd Abdel Wahab Brahim Benaissa <p>The strongest point about damage identification based on the dynamic measurements, is the ability perform structural health evaluation globally. Researchers in the last few years payed more attention to damage indicators based on modal analysis using either frequencies, mode shapes, or Frequency Response Functions (FRFs). This paper presents a new application of damage identification in a cross-ply (0°/90°/0°) laminated composite plate based on Force Residual Method (FRM) damage indicator. Considering single and multiple damages with different damage levels. As well as investigating the SSSS and CCCC boundary conditions effect on the estimation accuracy. Moreover, a white Gaussian noise is introduced to test the challenge the technique. The results show that the suggested FRM indicator provides accurate results under different boundary conditions. Favouring the SSSS boundary condition than the CCCC for 3% noise.</p> 2021-12-22T00:00:00+00:00 Copyright (c) 2021 Amar Behtani, Samir Tiachacht, Tawfiq Khatir, Samir Khatir, Magd Abdel Wahab, Brahim Benaissa Sensitivity analysis of the GTN damage parameters at different temperature for dynamic fracture propagation in X70 pipeline steel using neural network 2021-08-27T17:46:10+00:00 Abdelmoumin Ouladbrahim Idir Belaidi Samir Khatir Erica Magagnini Roberto Capozucca Magd Abdel Wahab <p>In this paper, the initial and maximum load was studied using the Finite Element Modeling (FEM) analysis during impact testing (CVN) of pipeline X70 steel. The Gurson-Tvergaard-Needleman (GTN) constitutive model has been used to simulate the growth of voids during deformation of pipeline steel at different temperatures. FEM simulations results used to study the sensitivity of the initial and maximum load with GTN parameters values proposed and the variation of temperatures.</p> <p>Finally, the applied artificial neural network (ANN) is used to predict the initial and maximum load for a given set of damage parameters X70 steel at different temperatures, based on the results obtained, the neural network is able to provide a satisfactory approximation of the load initiation and load maximum in impact testing of X70 Steel.</p> <p>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</p> 2021-09-25T00:00:00+00:00 Copyright (c) 2021 Abdelmoumin Ouladbrahim, Idir Belaidi , Samir Khatir , Erica Magagnini, Roberto Capozucca , Magd Abdel Wahab