Frattura ed Integrità Strutturale 2020-04-02T13:02:17+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).&nbsp;<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.</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 also available in a dedicated <a href="">YouTube channel</a>.&nbsp; All the issues are also published in a browsable version. All the issue in browsable version are also published in a dedicated website (<a href="">LINK</a>).</p> Building crack monitoring based on digital image processing 2020-04-02T12:59:48+00:00 Yanyan Xu Yanxia Cai Dandan Li Tierui Zhang <p>Building crack monitoring is of great value to the judgment of building safety. In this study, the digital image processing technology was studied and applied to the monitoring of building cracks. Crack images were collected by CCD camera, and then operations such as graying, correction, denoising and segmentation were carried out to obtain clear crack images. The obtained images are processed morphologically to further improve the quality. Finally, the width and length of cracks are calculated. In the case analysis, the results of 15 cracks measured by microscope were taken as the standards and compared with the calculated results. The results showed that the results calculated in this study and the manual measurement results differed little, and the average error of the width and length is 0.021 mm and 0.024 mm respectively, which suggested that the method proposed had high reliability. The findings of this study provides a new idea for the further development of building crack monitoring field, which is conducive to the accurate assessment of building safety.</p> 2020-03-31T07:30:21+00:00 Copyright (c) 2020 Yanyan Xu, Yanxia Cai, Dandan Li, Tierui Zhang Finte element modeling of the behavior of polymethyl-methacrylate (PMMA) during high pressure torsion process. 2020-04-02T13:00:12+00:00 Ahmed Drai Benaoumeur Aour Naima Belayachi Abderrahim Talha Noureddine Benseddiq <p>High Pressure Torsion (HPT) is a highly effective super-plastic deformation process for obtaining nano-materials with high performance mechanical properties. In view of its optimization, it is of paramount importance to evaluate the relations between the behavior of the material under the effects of different processing parameters. In this context, this work aims to highlight the plastic strain distribution in the deformed material as a function of the hydrostatic pressure, the torsion angle and the temperature of the material applied during the process. A typical amorphous polymer (Polymethyl-Methacrylate: PMMA) has been tested. Firstly, in order to identify the material parameters of a phenomenological elasto-viscoplastic model compression tests at different temperatures and strain rates have been carried out. Then, the distributions of the effective plastic strain, the equivalent plastic strain rate and the hydrostatic stress were analyzed using finite elements method. Recommendations on process conditions were proclaimed at the end of this work according to the obtained numerical results.</p> 2020-03-31T07:28:33+00:00 Copyright (c) 2020 Ahmed DRAI, Benaoumeur AOUR, Naima BELAYACHI , Abderrahim TALHA, Noureddine BENSEDDIQ Crack growth rate prediction based on damage accumulation functions for creep-fatigue interaction 2020-04-02T13:00:36+00:00 Andrey Tumanov V.N. Shlyannikov A.P. Zakharov <p>The present study is concerned with formulation of a model for the creep–fatigue crack growth rate prediction on the base of fracture damage zone concepts. It is supposed that crack growth rate can be determined by integration of damage accumulation rate equations into the fracture process zone for low-cycle fatigue and creep loading independently. In the case of low-cycle fatigue loading the damage accumulation function proposed by Ye and Wang was used as well as a classical Kachanov-Rabotnov power law was employment for the creep damage accumulation characterization. Fracture process zone size is calculated on the base of the nonlinear stress intensity factors concept proposed by Shlyannikov. The background for the proposed general model of crack growth rate under creep and fatigue interaction is given in order to comparison with the experimental data. Experimental study of crack growth rate under creep and fatigue interaction is performed for compact tension specimen made from 20CrMoV5. Crack growth rate carried out at the elevated temperature of 550°C according to ASTM E2760 standard. The predictions of the crack growth rate were compared with the experimental data for the 20CrMoV5 steel obtained at an elevated temperature, and the agreement was found to be satisfactory.</p> 2020-03-22T15:39:13+00:00 Copyright (c) 2020 Andrey Tumanov, V.N. Shlyannikov, A.P. Zakharov Optimization design based approach for the determination and minimization of the displacement under tensile load in hybrid composite joint 2020-04-02T13:01:00+00:00 Sahli Abderahmane Fouzia Merabbi Abdelkader Lousdad Abdelkader Megueni <p>C</p> <p>Composite materials are most often used for lengthier and thin structures susceptible to buckle. The optimization is often carried out taking into consideration the resistance to buckling and tensile loads for minimum displacement i.e maximization of the tensile load for composite assembly joint. It well known that nowadays that composite material in structural mechanics is widely used in many industrial sectors such as in aerospace and aeronautic, automobile, marine&nbsp; industries as well as in and civil engineering. Composite materials are attractive due to their advantages and performance i.e: lighter weights, high resistance to thermal and mechanical loads, resistance to corrosion and wear.</p> <p>In this paper an investigation is focused on the problem of hybrid assembly joint (bolted –bonded) composite structures. The aim is the optimization of the main influencing parameters.</p> <p>A bonded assembly has only one advantage which is its lightness; on the other hand bolted assembly has the inconvenient of increasing the weight of the structure and stress concentrators. In practice certain structural designs require the use of hybrid assembly for safety and reliability. The objective of this study is to optimize the influencing factors using both Genetic Algorithm and design of experiments for high mechanical performance of hybrid composite assembly.</p> 2020-03-22T15:38:02+00:00 Copyright (c) 2020 Sahli Abderahmane, Fouzia Merabbi, Abdelkader Lousdad, Abdelkader Megueni Multiple Crack Detection using Wavelet Transforms and Energy Signal Techniques 2020-04-02T13:01:24+00:00 Jalal Akbari Majid Ahmadifarid Abbas Kazemi Amiri <p>Wavelet transforms are efficient tools for structural health monitoring (SHM) and damage detection. However, these methods are encountered with some limitations in practice. Thus, signal energy analysis is used as an alternative technique for damage detection. In this paper, discrete wavelet transforms (DWT) and Teager energy operator (TEO) is applied to the curvature of the mode shapes of the beams, and the locations of the damages are identified. The results show that in comparison with the discrete wavelet transform, the signal energy operator has better performance. This superiority in detecting the damages, especially near the supports of the beam, is obvious and has enough sensitivities in low damage intensities. Additionally, the damage detection in the cases that the response data are noisy is investigated. For this purpose, by adding low-intensity noises to the curvature of the mode shapes, the abilities of the mentioned methods are evaluated. The results indicate that each method is not individually efficient in the detection of damages in noisy conditions, but the combination of them under noisy conditions is more reliable</p> 2020-03-22T15:36:55+00:00 Copyright (c) 2020 Jalal Akbari, Majid Ahmadifarid, Abbas Kazemi Amiri Initiation of hydrogen induced cracks at secondary phase particles 2020-04-02T13:01:48+00:00 Aurélie Laureys Margot Pinson Lisa Claeys Tim Deseranno Tom Depover Kim Verbeken <p><span lang="EN-US" style="margin: 0px; color: black; font-family: 'Garamond',serif; font-size: 12pt;">The goal of this work is to propose a general mechanism for hydrogen induced crack initiation in steels based on a microstructural study of multiple steel grades. Four types of steels with strongly varying microstructures are studied for this purpose, i.e. ultra low carbon (ULC) steel, TRIP (transformation induced plasticity) steel, Fe-C-Ti generic alloy, and pressure vessel steel. A strong dependency of the initiation of hydrogen induced cracks on the microstructural features in the materials is observed. By use of SEM-EBSD characterization, initiation is found to always occur at the hard secondary phase particles in the materials.</span></p> 2020-03-14T10:59:25+00:00 Copyright (c) 2020 Aurélie Laureys, margot Pinson, Lisa Claeys, tim Deseranno, tom Depover, Kim Verbeken Elastoplastic analysis of cracked Aluminum plates with a hybrid repair technique using the bonded composite patch and drilling hole in opening mode I 2020-04-02T13:02:17+00:00 Wahiba Nessrine Bouzitouna Wahid Oudad Mohamed Belhamiani Djamel Eddine Belhadri Leila Zouambi <p>The objective of this study is to analyze the performance of composite bonding repair, hole drilling and the combination of the two techniques (hybrid repairs) by tensile tests and to show the interest of a hybrid repair versus to other processes. These repair techniques can apply in different branches of engineering: mechanical, aerospace, civil, naval, etc. The finite element method with the ABAQUS code was used to model the mechanical behavior of the different repair techniques. The Notch Stress Intensity Factor (NSIF) is adopted to model the behavior of the cracked notch based on the volumetric method. The size of the plastic zone, the intensity of the normal σ<sub>yy</sub> stress, the peel stress and CTOD are combined to model the proposed technics repairs. Although the bonded composite is very strong, the application of a drilling hole results in additional energy absorption and reduces the level of the maximum normal stress by about 50% compared to a simple patch only. The use of a hybrid repair has a high resistance compared to other proposed methods, improves the mechanical strength and increases the life of the cracked structure compared to a single composite joint and a repair by drilling hole only.</p> 2020-03-05T04:00:52+00:00 Copyright (c) 2020 Mohamed Belhamiani, Wahiba Nessrine Bouzitouna, Wahid Oudad, Djamel Eddine Belhadri, Leila Zouambi Crack coalescence and strain accommodation in gypsum rock 2020-04-01T13:01:42+00:00 Chiara Caselle Sabrina Maria Rita Bonetto Daniele Costanzo <p>Gypsum is a soft rock with low strength and high propensity to plastic deformation. Its mechanical properties are relevant in a wide range of technical application (e.g. tunnel excavation, stability assessment of underground quarries, oil and gas accumulation). The micro-mechanisms involved in the deformation of gypsum rock have for long time interested the scientific world and are still not completely understood. The peculiar crystallographic structure of this bi-hydrate salt, with water molecules layered in the salt structure, favours the development of plastic structures in the rock.&nbsp;</p> <p>The present work proposes an experimental investigation of strain accommodation mechanisms in gypsum rock, reporting data referred to uniaxial and triaxial stress conditions. The rock strain was studied with a multiscale approach, with the comparison of results from DIC and microstructural analyses.</p> 2020-03-04T14:47:33+00:00 Copyright (c) 2020 Chiara Caselle, Sabrina Maria Rita Bonetto, Daniele Costanzo Effect of concrete cover thickness and main reinforcement ratio on flexural behavior of RC beams strengthened by NSM-GFRP bars 2020-04-01T13:02:06+00:00 Hesham EL-Emam Alaa El-Sisi Ramy Reda Mohamed Bneni Mohamed Seleem <p>Experimental and numerical programs were invoked to investigate the effect of concrete cover and area of main steel reinforcement on the flexural behavior of strengthened RC beams by near-surface mounted glass fiber reinforced polymeric (NSM GFRP) bars of different lengths. Nine beams divided into three main groups were tested under four-point bending. The three beams of the first group were strengthened by different lengths of GFRP bars and having a concrete cover of 50 mm, while the three beams in the second group were strengthened in a similar manner as those of the first group but the concrete cover was 30 mm. The main steel reinforcement in the first and second groups was 2Ø10. The three beams of the third group were similar to those of the first and second group but the main steel reinforcement was 2Ø16. The 3-D FE commercial ANSYS program was used for the numerical work. The experimental results showed that decreasing the concrete cover increased the flexural capacity of the strengthened RC beams but this improvement disappeared by decreasing the NSM GFRP bar length. The RC beams flexural strength increased with increasing area of main steel reinforcement. The numerical results showed an agreement with the experimental results.</p> 2020-03-04T04:19:35+00:00 Copyright (c) 2020 Hesham EL-Emam, Alaa El-Sisi, Ramy Reda, Mohamed Bneni, Mohamed Seleem Numerical modeling of bending, buckling, and vibration of functionally graded beams by using a higher-order shear deformation theory 2020-04-01T13:02:30+00:00 Nabil Hebbar Imène Hebbar Djamel Ouinas Mohamed Bourada <p>The objective of this work is to analyze the behavior beams functionally graded, simply supported, under different conditions such as bending, buckling, and vibration and this by use shear deformation theories a two-dimensional (2D) and quasi-three-dimensional (quasi-3D). The proposed theories take into account a new field of displacement which includes indeterminate whole terms and contains fewer unknowns, compared to other theories of the literature; by taking account of the effects of the transverse shears and the thickness stretching. In this theory, the distribution of the transverse shear stress is hyperbolic and satisfies the boundary conditions on the upper and lower surfaces of the beam without the need for a shear correction factor. In this type of beam the properties of the materials vary according to a distribution of the volume fraction, the Hamilton principle is used to calculate the equations of motion, and in order to check the accuracy of the theory used comparison is made with the studies existing in the literature.</p> 2020-03-03T06:10:34+00:00 Copyright (c) 2020 Nabil Hebbar, Imène Hebbar, Djamel Ouinas, Mohamed Bourada Effect of aggregate type on moisture susceptibility of modified cold recycled mix asphalt: evaluation by mechanical tests and Surface Free Energy method 2020-04-01T13:02:54+00:00 Hassan Latifi Nahid Amini <p>There are deficiencies associated with cold mix asphalts, specifically, cold recycled mix asphalts in comparison with hot mix asphalt or hot recycled mix asphalt such as higher moisture susceptibility. Moisture damage of asphalt mixtures is inversely related to the bond quality between aggregates and binder. In this study, Portland cement (PC) and acryl polymer (AP) additives were employed to improve this bond. The effectiveness of used additives in improving the moisture susceptibility of cold recycled mix asphalt was examined using Surface Free Energy (SFE) method. Indirect Tensile Strength test and Dynamic Modulus test were performed to validate SFE method results. Moreover, scanning electron microscope (SEM) images were obtained for better understanding of mixture's microstructure. Also, effect of using granite, limestone and recycled asphalt pavement (RAP) aggregates was evaluated. The findings showed that cement and acryl polymer additives improved resistance of different studied mixtures, specifically, cold recycled mix asphalt against moisture damage by improving the adhesion between aggregate and asphalt. Considering effect of aggregates on moisture susceptibility, limestone-mixtures had the highest resistance while the RAP-mixtures performed the worst among the three. Finally, it was shown that results of SFE method were compatible with the mechanical tests in predicting moisture damage.</p> 2020-03-02T07:10:14+00:00 Copyright (c) 2020 Hassan Latifi, Nahid Amini Object-Oriented Software for Fitness-For-Service Assessment of Cracked Cylinder Based on API RP 579 2020-04-01T13:03:18+00:00 Jirapong Kasivitamnuay Pairod Singhatanadgid <p>Fitness-for-service assessment of a cracked component intends to evaluate its remaining strength and remaining life to support the implementation of a maintenance plan. This research aims to develop a fitness-for-service assessment software to facilitate the task. The software development process included identifying the software specifications, designing the software structure, manipulating the information from the standard for programming, the graphical user interface design, and finally verification of the software. The assessment procedure employed in this study was the third edition of the standard API RP 579. The software structure was designed using an object-oriented concept. The software can perform integrity assessment levels 1, 2, and 3 option B, leak-before-break assessment, and remaining life assessment for a cracked cylinder that has a through-thickness crack or semi-elliptical surface crack oriented in an axial or circumferential direction. The applied loads could be a nominal axial force, bending moment, and internal pressure, as well as stress profiles perpendicular to the crack plane due to mechanical, thermal, and residual stresses. Accuracy of the software was demonstrated by applying it to example problems. Some aspects of the software extensibility were conceptually discussed.</p> 2020-03-01T16:10:16+00:00 Copyright (c) 2020 Jirapong Kasivitamnuay, Pairod Singhatanadgid Prediction of the burst pressure for defective pipelines using different semi-empirical models 2020-04-01T13:03:43+00:00 Sandip Budhe S. de Barros M. D. Banea <p>The main aim of this work is to predict the theoretical burst pressure of defective pipelines using different semi-empirical models and compare them with the results of the hydrostatic tests. A methodology was formulated with accounting for a minimum thickness (weakest section of the pipe) over the length of the pipe to predict the most conservative burst pressure. With a simple analytical expression, a reasonable accuracy and more conservative burst pressure can be obtained for any arbitrary defect shapes. A variation of burst pressure was found between theoretical prediction and hydrostatic burst test results with respect to the different semi-empirical models even for the same corroded defects. Different defect geometry shapes and pipe material conditions are the possible causes for variation in the burst pressure between the semi-empirical models, so a careful selection of these parameters is necessary. The proposed methodology predicted a more conservative burst pressure for all arbitrary defects shapes and can predict reasonably accurate values if it accounts for the axial stress.</p> 2020-02-29T17:03:24+00:00 Copyright (c) 2020 Sandip Budhe, S. de Barros, M. D. Banea Numerical modelling of dynamic ductile fracture propagation in different lab-scale experiments using GTN damage model 2020-04-01T13:04:07+00:00 Benoît Paermentier Dimitri Debruyne Reza Talemi <p>Initiation and propagation of ductile fractures are a major consideration during the design of high-pressure pipelines. Consequences of a pipeline failure can be catastrophic thus structural integrity must be ensured over several decades. Traditional lab-scale experiments such as the Charpy V-Notch (CVN) and Drop Weight Tear Test (DWTT), impact experiments on a notched three-point bending sample, are widely used to measure the fracture toughness of a material. However, with increasing wall thickness and the transition to high-grade steels in the pipeline industry, the size-effect of the specimen and inverse fracture became prominent issues. A new testing methodology called the Dynamic Tensile Tear Test (DT3) is currently investigated as to address the issues presented by the current state of the art.</p> <p>In this study, a numerical investigation is conducted on the CVN, DWTT and DT3 experiments to compare the modelling of dynamic ductile fracture propagation in three different testing scales using the Gurson-Tvergaard-Needleman (GTN) damage model. X70 and X100 pipeline steel grades are used to model material behaviour. For each considered lab-scale experiment, the dynamic ductile fracture behaviour was successfully reproduced using the GTN damage model.</p> 2020-02-08T04:45:43+00:00 Copyright (c) 2020 Benoît Paermentier, Dimitri Debruyne, Reza Talemi Elastoplastic analysis of plane structures using improved membrane finite element with rotational DOFs 2020-04-01T13:04:32+00:00 Ayoub Ayadi Kamel Meftah Lakhdar Sedira <p>In this work, the small-strain elastoplastic behavior of structures is analyzed using an improved nonlinear finite element formulation. In this framework, an eight-node quadrilateral finite element denoted PFR8 (Plane Fiber Rotation) that belongs to the set of elements with rotational degrees of freedom is developed. Its formulation stems from the plane adaptation of the Space Fiber Rotation (SFR) concept that considers virtual rotations of nodal fiber within the element. This approach results in an enhancement of the displacement vector approximation. Von-Mises yield criteria have been applied for yielding of the materials along with the associated flow rule. Newton-Raphson method has been used to solve the nonlinear equations. To assess the performance of the proposed element, benchmark problems are addressed and the results are compared with some analytical and numerical solutions from the literature.</p> 2020-02-06T15:01:18+00:00 Copyright (c) 2020 Ayoub Ayadi, Kamel Meftah, Lakhdar Sedira Alternative Estimation of Effective Young’s Modulus for Lightweight Aggregate Concrete LWAC 2020-04-01T13:04:57+00:00 Meriem Fakhreddine Bouali Hima Abdelkader <p>The prediction of effective mechanical properties of composite materials using analytical models is of significant practical interest in situations in which tests are impossible, difficult, or costly. Many experimental and numerical works are attempting to predict the elastic properties of Lightweight Aggregate Concrete (LWAC). In order to choose the optimized prediction composite model, the purpose of this paper is to appraise the effective Young’s modulus of LWAC using two-phase composite models. To this effect, results of previous experimental research have used as a platform, upon which, 07 two-phase composite models were applied. The outcomes of this comparative analysis show that not all two-phase analytical models can be directly used for predicting Young’s modulus of LWAC. The Hashin-Hansen and Counto2 models are in close concordance with the experimental Young’s modulus of all LWAC used for comparison in this study. Thus, the precision of this prediction model demonstrates its effectiveness and potential application as a model for Lightweight Aggregate Concrete. They were found more appropriate for reasonable prediction of elasticity modules of the LWAC.</p> 2020-02-04T17:35:10+00:00 Copyright (c) 2020 Meriem Fakhreddine Bouali, Hima Abdelkader Numerical Analysis and Verification of Residual Stress in T Joint of S355 Steel 2020-04-01T13:05:22+00:00 Xiangming Wang Erfu Guo <p>T joint is a widely used welding form. The welding deformation and residual stress produced during the welding process will affect the integrity and reliability of the structure. In this study, S355 low alloy steel was used as test material, and the thermal-mechanical coupling characteristics of multi-layer welding were combined with SYSWELD finite element software to calculate the residual stress of T joint after welding. The residual stress of multi-layer welding T joint with tangent tube and sheet after welding was measured by X-ray diffraction method. The results showed that the numerical simulation agreed well with the experimental results. For the transverse residual stress, the maximum residual stress appeared near the weld toe, and the transverse stress perpendicular to the weld direction presented tensile stress at the weld center and presented stress at the tube surface far from the weld. For the longitudinal residual stress, the maximum residual stress also appeared near the weld toe, and the value was the largest at the center of the weld and decreased along the direction perpendicular to the weld. The research results can provide a reference for actual welding design.</p> 2020-02-02T16:27:09+00:00 Copyright (c) 2020 Xiangming Wang, Erfu Guo Thermally active interphase inclusion in a smooth contact conditions with transversely isotropic half-spaces 2020-04-01T13:05:47+00:00 Oleksandr Kryvyi Yurii Morozov <p>An exact solution of the stationary thermoelasticity problem about interfacial circular absolutely rigid inclusion, which is in the smooth contact conditions in a piecewise homogeneous transversely homogeneous space, is constructed. The task with the help of the constructed discontinuous solution, by the method of singular integral relations, is reduced to a system of singular integral equations (SIE). An exact solution has been built for the specified SIE, as a result, dependences of translational displacement of the inclusion on temperature, the resultant load, main moment and thermomechanical characteristics of transversely isotropic materials have been obtained.</p> 2020-01-31T16:22:25+00:00 Copyright (c) 2020 Oleksandr Kryvyi, Yurii Morozov Three-dimensional Numerical Analysis of a Joint Bonded Reinforced with Silica Nanoparticles (SiO2) 2020-04-01T13:06:11+00:00 Noureddine Djebbar Rachid Hadj Boulenouar Benali Boutabout <p>Nanostructured adhesives may be defined as those materials whose elements imbedded in an epoxy matrix have dimensions in the 1 to 100 nm range. One of the most interesting aspects of ceramic nanoparticles is that their mechanical properties depend strongly upon the particle size and shape. Silica nanoparticles (SiO2) have different physical and mechanical properties from bulk ceramics. The aim of the present study is to investigate the effect of the nanoparticles rate on the equivalent stress, peeling stress and shear stress as well as the strains developed in the adhesive joint. Three-dimensional finite element models of adhesive joint were developed to determine the stress intensity as well as strain with different nanoparticles rate in the epoxy resin. Dispersion of nanoparticles with different percent in the epoxy resin allows for reinforcing the adhesive. Polymer embedded silica nanoparticles (SiO2) proved to be highly effective.</p> 2020-01-30T04:54:01+00:00 Copyright (c) 2020 Noureddine Djebbar, Rachid Hadj Boulenouar, Benali Boutabout Study on the thermal cycle of Wire Arc Additive Manufactured (WAAM) carbon steel wall using numerical simulation 2020-04-01T13:06:35+00:00 Mohsen Saadatmand Reza Talemi <p>The thermal behavior in WAAM process is a significant cause for thermal stress. In this paper, a 3D model of a four-layer wall is built in ABAQUS software in order to investigate the thermal behavior in a carbon steel (ASTM A36) WAAM wall. Moreover, the effects of substrate preheating temperature and travel speed on the temperature distribution are studied. The modelling results show that with increase in number of deposited layers, the peak temperature increases but average cooling speed decreases. Furthermore, substrate preheating increases peak temperature of fist layer and decreases its average cooling speed. Regarding simulation results, the travel speed has major effects on the thermal behavior of deposited layers.&nbsp;&nbsp;</p> 2020-01-28T17:24:48+00:00 Copyright (c) 2020 Mohsen Saadatmand, Reza Talemi A comparative study on the fatigue life of the vehicle body spot welds using different numerical techniques: Inertia relief and Modal dynamic analyses 2020-04-01T13:06:59+00:00 G.H. Farrahi Alireza Ahmadi Kazem Reza Kashyzadeh Shahram Azadi Kambiz Jahani <p>Among different parts of a vehicle, the body is the main load-bearing component and as a result, its durability is critical. Fatigue analyses are typically divided into different categories, the quasi-static methods and the dynamic methods. The aim of this paper was to compare the inertia relief and modal dynamic approaches for their formulation, accuracy and computation time. The chosen case study is the fatigue life of the vehicle body. By utilizing multi-body dynamics model and driving the vehicle on different standardized roads and by different velocities, the force and moment time histories which act on the body were calculated and later used by the finite element model for the stress analysis. Then, by using the structural stress method, the fatigue life of the vehicle spot welds were calculated and the results were compared for both quasi-static and dynamic approaches. The findings reveal that the modal dynamic method is almost 37 times more time-consuming than the inertia relief approach, but if accuracy is desired, it can be up to 96% more accurate. Also as predicted, at low frequency loading (less than 10% of the first nonzero frequency of the structure), there is no difference between the results of both methods.</p> 2020-01-28T07:17:19+00:00 Copyright (c) 2020 G.H. Farrahi, Alireza Ahmadi, Kazem Reza Kashyzadeh, Shahram Azadi, Kambiz Jahani Differential Evolution Algorithm for Identification of Structural Damage in Steel Beams 2020-04-01T13:07:23+00:00 Brunno Emidio Sobrinho Gilberto Gomes Welington Vital da Silva Ramon Silva Erwin U. L. Palechor Luciano M. Bezerra <p>Problems involving errors and uncertainties from the use of numerical and experimental responses of beams using optimization processes have been studied by many researchers. In this field, to simulate the real behavior of structures, especially in problems involving damage, it is required to have reliable experimental results in order to adjust a numerical model. These difficulties may be associated for example to modeling the connection stiffness, support conditions, or relevant parameters in structures involving damages among others. This paper proposes a new methodology to detect damage in steel beams using the Differential Evolution Technique based on experimental and numerical data. The results show a great potential of the methodology to solve damage detection problems.</p> 2020-01-25T17:35:32+00:00 Copyright (c) 2020 Brunno Emidio Sobrinho, Gilberto Gomes, Welington Vital da Silva, Ramon Silva, Erwin U. L. Palechor, Luciano M. Bezerra Experimental and Numerical Analysis of Epoxy Based Adhesive Failure on Mono- and Bi-Material Single Lap Joints Under Different Displacement Rates 2020-04-01T13:07:47+00:00 Hojjat Ghahramanzadeh Asl Salim Çam Osman Orhan Adnan Özel <p>Development in material science impose to use different materials in production. This causes a problem for joining different materials because traditional joining techniques such as welding could not overcome this problem in industries such as automotive. Hence, adhesive bonding overcomes this problem by its superiorities to join different materials. Joint strength of epoxy-based adhesives are affected by adhesive thickness, adherent’s surface quality and curing conditions. In this study, two different materials (SAE 304 and AL7075) were bonded by epoxy adhesive (3M DP460NS) as single lap joint (SLJ) of Aluminum-Aluminum, Steel-Steel and Aluminum-Steel. Effects of adhesive thickness (0.05, 0.13, 0.25 mm) and surface roughness (281, 193, 81 nm) to strength were compared. SLJs were tested for 1, 10, 25 and 50 mm/min displacement rates. Adhesive surface structures were imaged by Scanning Electron Microscopy (SEM) to investigate adhesive fractures. Surface roughness’s were examined by using Atomic Force Microscopy (AFM) to compare its influence on failure load. Finite Element Analysis (FEA) were conducted by using Cohesive Zone Model with ANSYS 18.0 software to obtain stress distribution of adhesive.</p> <p>Optimum values according to the present conditions of thickness(0.13mm) and roughness(&lt;200nm) were determined. Experimental results were demonstrated that while displacement rates rose, failure loads increased as well. FEA analysis were fit to experimental results. It has been observed that along with material type, peel stresses become an important factor for joint strength.</p> <p>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</p> 2020-01-25T12:36:51+00:00 Copyright (c) 2020 Hojjat Ghahramanzadeh Asl, Salim Çam, Osman Orhan, Adnan Özel Finite element analysis of the thermomechanical behavior of metal matrix composites (MMC) 2020-04-01T13:08:13+00:00 Zaoui Bouchra Baghdadi Mohammed Boualem Serier Mohammed Belhouari <p>In this work the finite element method (FEM) was used to analyze the mechanical behavior of the composite materials subjected to the mechanical loading. This behavior is studied in terms of stress intensity factor variation as a function of the applied stress intensity. The residual stresses induced in the composites, during the elaboration of these composites are taken into consideration in this study. The superimposition of these types of stresses (residuals and commissioning) is simulated here by thermomechanical stresses. The results obtained show that in the vicinity very close to the fiber-matrix interface and under the effect of this loading type, the matrix cracks propagate in modes I, II and III, and far from the interface, in mode I. The propagation kinetics is slowed down by the interface-crack interaction.</p> <p>The effects of the crack size, the orientation and propagation of the crack, commissioning stresses, the elaboration temperature, fiber physical properties, matrix stiffness and thermomechanical stresses have been highlighted in this work.</p> 2020-01-03T09:26:08+00:00 Copyright (c) 2020 Baghdadi Mohammed, Zaoui Zaoui Bouchra, Boualem Serier, Mohammed Belhouari Analysis of Printed Circuit Boards strains using finite element analysis and digital image correlation 2020-04-01T13:09:00+00:00 Liviu Marsavina Alexandru Falk Octavian Pop <p>This paper investigates the use of digital image correlation (DIC) and finite element analysis for strain measurement on Printed Board Circuits (PCBs).</p> <p>Circuit boards (PCBs) are designed to mechanically support and electrically connect an electronic component assembly. Due to screw assemblies, the surface level differences on which the PCB is placed, the process of assembling the electronic components induces a certain state of stress and deformation in the PCB. The main components affected are microprocessors due to the way they are glued to PCBs with BGA - Ball grid arrays (BGA).</p> <p>Digital Image Correlation (DIC) is a full-field contactless optical method for measuring displacements and strain in experimental testing, based on the correlation of images taken during test. The experimental setup is realized with Dantec Q-400 system used for image capture and Istra 4D software for image correlations and data analyses. The maximum level of the obtained strain is compared with the allowable limit.</p> <p>Finite element analysis (FEA) is a numerical method of analysis for stresses and strain in structures of any given geometry.</p> 2019-12-14T00:00:00+00:00 Copyright (c) 2020 Liviu Marsavina, Alexandru Falk, Octavian Pop