•A coupled 3D laser scanning and DIC system was innovated.•3D tunnel model tunnel profile was obtained by the system.•Geometry acquisition and deformation monitoring of runnels were accomplished.•3D ...DIC was adopted to monitor the geometrical changes.
In this study, a 40 m-long section of a shallow railway rock tunnel so-called “Monte Seco tunnel” located at Vitoria Minas Railway in Brazil is investigated. In the real environment, the tunnel has been scanned by a 3D Terrestrial Laser Scanning (TLS) instrumentation and its geometry was reconstructed on a point cloud. Due to the complex geometry of the irregular rock face created by drill and blast, the obtained geometry lacked a number of regions (occlusions). In this study, a small-size model of the obtained point cloud was built through additive manufacturing and submitted to laboratory tests. A scaled demonstrator was developed for the acquisition of the 3D tunnel model profile with a Laser Scanning System (LSS), comprising a camera and a circular laser that scans the entire tunnel surface. After 3D geometry acquisition, the tunnel model was compressively loaded by imposing a displacement from the exterior wall and the deformation was monitored by a 3D Digital Image correlation (DIC) system setup adapted to the rail structure. Promising results have been accomplished and the achieved tunnel’s point cloud verified the geometrical characteristics with minimum occlusions. Owing to obtained successful results on the geometry documentation, a real-scale 3D LSS model is presented for operation in a real environment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A crack tip monitoring is studied through multiscale contactless optical methods.•DIC and ESPI techniques are employed to measure the experimental data.•The crack is detected and its length is ...measured by both methods.•SIF is calculated and compared to the reference solution.•The crack opening evolution is studied by ESPI and DIC analyses.
This study focuses on the development of a complementary fatigue crack-tip evaluation approach with multiscale optical techniques with different resolutions. A middle tension (MT) specimen, of aluminium alloy AA6082-T6, was prepared and submitted to a cyclic fatigue loading to generate a fatigue crack. Then, it was statically loaded under a uniaxial tensile condition, and two non-contact full-field optical techniques, Digital Image Correlation (DIC) and Electronic Speckle Pattern Interferometry (ESPI), were employed to acquire the experimental data. While the specimen is loaded with incremental force values, the behaviour of the cracked area is monitored, with displacement and deformation fields acquired for each force increment. The obtained data is thereby used to calculate the Stress Intensity Factor (SIF) and monitor the crack opening evolution. An overdeterministic algorithm was developed for the SIF determination. The main contribution of the present work is the development of a complementary multiscale methodology, which employs available techniques with different resolutions to monitor the tip of a fatigue crack, drawing a comparison between calculated parameters for each system to shift from one technique to the higher resolution one and validating the proposed methodologies. The obtained SIF values are compared to the reference solution proposed by ASTM E647, and an acceptable agreement has been verified amongst the results.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Dental caries and dental restorations possess a long history and over the years, many materials and methods have been invented. In recent decades, modern techniques and materials have brought ...complexity to this issue, which has created the necessity to investigate more and more to achieve durability, consistency, proper mechanical properties, efficiency, beauty, good colour, and reduced costs and time. Combined with the recent advances in the medical field, mechanical engineering plays a significant role in this topic. This work aims at studying the elasto-static response of a human molar tooth as a case study, respecting the integral property of the tooth and different composite materials of the dental restoration. The structural integrity of the case study will be assessed through advanced numerical modelling resorting to meshless methods within the stress analysis on the molar tooth under different loading conditions. In this regard, bruxism is considered as being one of the most important cases that cause damage and fracture in a human tooth. The obtained meshless methods results are compared to the finite element method (FEM) solution. The advantages and disadvantages of the analysed materials are identified, which could be used by the producers of the studied materials to improve their quality. On the other hand, a computational framework, as the one presented here, would assist the clinical practice and treatment decision (in accordance with each patient's characteristics).
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
This study presents an experimental and numerical assessment of the fracture toughness of steam boiler components, which have been in operation for more than 100,000 h. The materials tested are ...components of two different parts of a steam turbine unit: the pipeline section that connects the headers with turbines, which is made of 13HMF steel, and the valve chamber section, which is made of L17HMF steel grades. Full-size arc-shaped tension specimens (AT) are employed for the experimental evaluation. AT and single-edge notch tension (SENT) specimens are used for numerical assessment. The finite element method (FEM) formulations are developed and examined in Abaqus, which is set up as a shell model with the specimen thickness designated as the mid-surface for the analysis. The notch is modeled using a contour integral definition based on the maximum energy release rate criterion. The fracture toughness is quantified using the stress intensity factor (KI), and the results are compared. The valve chamber is found to have a higher fracture toughness than the pipeline section. The effect of specimen geometry is also noticeable, and the fracture toughness of SENT and AT specimens are compared. The results are useful in assessing the component's durability after long operation.
•Experimental and numerical assessment of fracture toughness of steam boiler components, in operation for over 100 khours.•Pipeline connecting the headers with turbines, made of 13HMF steel, and valve chamber, made of L17HMF steel grades tested.•Arc-shaped for experiments, and single-edge notch tension specimens employed for numerical assessment.•FEM formulations developed and examined in Abaqus, effect of geometry noticed, fracture toughness were compared.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This manuscript investigates the effect of existing slant cracks in finite plates subjected to the mode I loading condition using the stress dead‐zone (SDZ) concept. For this purpose, standardised ...polymeric middle tension (MT) specimens containing slant notches with different orientations were mechanically tested under a unidirectional tensile load. The experimental data were collected and analysed using 3D digital image correlation (DIC) contributing to document the deformation field around slanted cracks and stress intensity factor (SIF) evaluation. Computationally, the fracture model was solved using the finite element method (FEM) to obtain results on the SIF, deformation field and the SDZ characterisations. The obtained SIFs were compared with a reference solution from the literature. An acceptable agreement has been accomplished amongst the results. Furthermore, the SDZ was assessed through deformation field obtained from DIC and FEM.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
The mechanical integrity of two commercially available lithium-ion battery separators was investigated under uniaxial and biaxial loading conditions. Two dry-processed microporous films with ...polypropylene (PP)/polyethylene (PE)/polypropylene (PP) compositions were studied: Celgard H2010 Trilayer and Celgard Q20S1HX Ceramic-Coated Trilayer. The uniaxial tests were carried out along the machine direction (MD), transverse direction (TD), and diagonal direction (DD). In order to generate a state of in-plane biaxial tension, a pneumatic bulge test setup was prioritized over the commonly performed punch test in an attempt to eliminate the effects of contact friction. The biaxial flow stress-strain behavior of the membranes was deduced via the Panknin-Kruglov method coupled with a 3D Digital Image Correlation (DIC) technique. The findings demonstrate a high degree of in-plane anisotropy in both membranes. The ceramic coating was found to negatively affect the mechanical performance of the trilayer microporous separator, compromising its strength and stretchability, while preserving its failure mode. Derived from experimentally calibrated constitutive models, a finite element model was developed using the explicit solver OpenRadioss. The numerical model was capable of predicting the biaxial deformation of the semicrystalline membranes up until failure, showing a fairly good correlation with the experimental observations.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
•The stress intensity factor is experimentally calculated using thermoelastic stress analysis.•The model is numerically simulated using finite element and meshless methods.•The obtained numerical ...results are very close with the experimental solution, validating the methodology proposed.•This work possesses a hybrid numerical/experimental attitude.•The obtained stress result is combined with an overdeterministic algorithm to evaluate the stress intensity factor.
This work aims at determining the stress intensity factor (SIF) for a compact tension specimen (CT) during a fatigue crack growth test with Thermoelastic Stress Analysis (TSA). Additionally, the problem is addressed using advanced discretization techniques, Radial Point Interpolation Meshless method (RPIM) and Finite Element Method (FEM) to obtain a stress distribution and calculate SIF range. Based on an optimization procedure, a functional stress relation was designated where the TSA analysis relies upon. The stress fields obtained with the FEM and the RPIM, are graphically represented and both methodologies are compared with the experimental TSA analysis in the presence of mode I fatigue loading test. The stress field in front of the crack tip is obtained with TSA and used in Williams series expansion, together with an overdeterministic algorithm to compute the SIF under mode I loading. This proposed procedure possesses a hybrid experimental-computational feature in which the SIF determination hinges on a stress field obtained with an optical technique, TSA. The robustness of the numerical FE and RPIM computations were thereby experimentally validated with the achieved SIF solution.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The dynamic assessment of a passenger bus is of the highest importance when aiming at high safety standards and low emissions for environmental sustainability. This work studies the dynamic response ...of a bus considering its modal analysis, for which simple dynamic models were developed for fast determination of the lowest frequencies, mainly arising from the suspension flexibility. In addition, complex natural vibration modes, impossible to determine using simplified models, were calculated via finite element method (FEM) modeling. To study the tire elastic behavior, as the key link between the vehicle and the road, specific deformation models, leading to a stiffness matrix to be combined with that of the vehicle spring suspension at each wheel/axis, were developed. This study aims at proposing a set of mathematical formulations to describe the modal behavior of passenger buses in detail, which could be applicable in any other long vehicle with similar conditions. Two main factors are studied, namely the suspension and the tire deformation effect. An acceptable agreement was verified between the simplified approach and FEM model results for the evaluation of natural frequencies and associated modes.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Automotive engineering is a very important branch of design and development in mechanical engineering devoted to vehicle manufacturing. It demands solid knowledge focusing on the kinematics and ...dynamics of mechanical systems, either using structural analysis or modelling techniques. In this manuscript, a model based on the application of the fundamentals of the static and dynamic behaviour of the suspension system of a bus vehicle is developed. Therefore, a set of mathematical equations is expanded following the structural dynamic formulations to obtain an analytical solution on natural frequencies and the displacement under an external load. The problem is also solved using the Finite Element Method (FEM) to confirm the analytical results. Equivalent material parameters and boundary conditions were used for the FEM simulation. This work aims to propose a methodology based on modal analysis with a simplified model to predict the dynamic response of an automotive structure.
This work investigates fracture characteristics of a marble semi-circular bend (SCB) specimen with a pre-defined crack under a compressive loading condition. It aims at evaluating how the fracture ...toughness can be affected by the crack and span length variation. Numerically, the model is solved using meshless methods, extended to the linear elastic fracture mechanics (LEFM), resorting to radial point interpolation method (RPIM) and its natural neighbor versions (NNRPIMv1 and NNRPIMv2). Alternatively, to validate the meshless method results, the problem is resolved following the finite element method (FEM) model based on the standard 2D constant strain triangle elements. As a result, fracture toughness and the critical strain energy release rate are characterized following the testing method on the cracked straight through semi-circular bend specimen (CSTSCB). A comparison is drawn amongst the theoretical, meshless methods and FEM results to evaluate the capability of advanced numerical methods. Encouraging results have been accomplished leading to validate the supporting numerical methodologies.
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