This work presents synthesis and spectroscopic characterization of a new metal-organic framework (MOF). The compound Fe-BDC-DMF was synthetized by the solvothermal method and prepared via a reaction between FeCl3.6H2O and benzene-1,4-dicarboxylic acid (H2BDC) or terephthalic acid using N,N-dimethylformamide (DMF) as solvent. The powder was characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR) analysis. The electrochemical properties were investigated in a typical lithium-ion battery electrolyte by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charging and discharging. The synthetized Fe-BDC-DMF metal-organic framework (MOF) contains a mixture of three phases, identified by PXRD as: MOF-235, and MIL-53(Fe) monoclinic with C2/c and P21/c space groups. The structure of the Fe-BDC is built up from Fe3+ ions, terephalates (BDC) bridges and in-situ-generated DMF ligands. The electrochemical measurements conducted in the potential range of 0.5–3.5 V vs. Li+/Li0 show the voltage profiles of Fe-BDC and a plateau capacity of around 175 mAh/g. © 2022 The Author(s)

Residual stresses created during the packaging process can adversely affect the reliability of electronics components. We used incremental hole-drilling method, following the ASTM E 837-20 standard, to measure packaging induced residual stresses in discrete packages of power electronics components. For this purpose, we bonded a strain gauge on the surface of a Gallium Nitride (GaN) power component, drilled a hole through the thickness of the component in several incremental steps, recorded the relaxed strain data on the sample surface using the strain gauge, and finally calculated the residual stresses from the measured strain data. The recorded strains and the residual stresses are related by the compliance coefficients. For the hole drilling method in the isotropic materials, the compliance coefficients are calculated from the analytical solutions, and available in the ASTM standard. But for the orthotropic multilayered components typically found in microelectronics assemblies, numerical solutions are necessary. We developed a subroutine in ANSYS APDL to calculate the compliance coefficients of the hole drilling test in the molded and embedded power electronics components. This can extend the capability of the hole drilling method to determine residual stresses in more complex layered structures found in electronics. 

Additive manufacturing (AM) of large-scale polymer and composite parts using robotic arms integrated with extruders has received significant attention in recent years. Despite the contributions of great technical progress and material development towards optimizing this manufacturing method, different failure modes observed in the final printed products have hindered its application in producing large engineering structures used in aerospace and automotive industries. We report failure modes in a variety of printed polymer and composite parts, including fuel tanks and car bumpers. Delamination and warpage observed in these parts originate mostly from thermal gradients and residual stresses accumulated during material deposition and cooling. Because printing large structures requires expensive resources, process simulation to recognize the possible failure modes can significantly lower the manufacturing cost. In this regard, accurate prediction of temperature distribution using thermal simulations is the first step. Finite element analysis (FEA) was used for process simulation of large-scale robotic AM. The important steps of the simulation are presented, and the challenges related to the modeling are recognized and discussed in detail. The numerical results showed reasonable agreement with the temperature data measured by an infrared camera. While in small-scale extrusion AM, the cooling time to the glassy state is less than 1 s, in large-scale AM, the cooling time is around two orders of magnitudes longer. © 2022 by the authors

This text is an extension of notes from courses first given during the 1990-ies for engineers employed in industry, and then for master students in the international masters programme at Chalmers Technical University in Gothenburg 2001-2009. Hence, it covers most issues of fatigue analysis as taught on the master level in universities. The micromechanical features of fatigue as studied in materials science constitute an area of research and education in itself. The descriptions here are simplistic. Some fundamental models are introduced just to give qualitative indications of the micromechanical background to fatigue phenomena. These models are useful for the understanding of principal effects found by experiments on the macroscopic level. Some emphasis is given to the stochastic nature of fatigue. The use of statistical methods in design is described as well as uncertainty assessments in the evaluation of experiments to find material properties connected to fatigue. Most of the mathematical expressions used in fatigue design are not physical laws but suitable models suggested from curve fitting of experimental results, and then a critical statistical assessment is essential. The aim is to supply an easy-to-use support to people working with fatigue in industrial environments or as teachers on the bachelor or master level in universities. It should give useful background and understanding to handbook formulas and requirements in standards. If the text is used in courses it should be complemented by examples and problems to solve since only a few examples of a principal character are included. Likewise, extensive handbook data for e g stress concentration and stress intensity factors, and material properties, are necessary for use in practical design situations. Computer programs for solving of various problems, as FEM codes or procedures to find load spectra are not included, since the field is changing quickly, and the Internet gives ample information. The intention has not been to produce a reference work for scientific studies of fatigue. Therefore, literature references are few and only including works of authors having produced milestone contributions to the area, or well renowned textbooks, standards, and handbooks. It is underlined that all experimental evidence shows that fatigue phenomena in real materials can by no means be precisely described by mathematical models and formulas. Models are sometimes developed in the text by sophisticated mathematical tools giving such an impression. But they are just models, often competing with one another, and they only constitute a framework for understanding and approximate data for design.

Two approaches to modelling the effects of embedded defects and impact damage in composite aerostructures are presented. These differ in the manner in which the damage is represented; one as an equivalent delamination and the other as a soft inclusion with non-linear homogenized material properties. These techniques are applied to study the effects of defects and impact damage on the performance of composite panels.

There is an increasing need for reliable methods to assess load-carrying capacity and remaining service life of existing infrastructure. Several previous research projects have resulted in a verified, simple 1D model for assessment of anchorage in corroded reinforced concrete structures. Previous verification has involved both experiments and detailed 3D NLFE analyses. To further develop the 1D model it needs to be extended to comprise more practical situations. In order to facilitate an efficient extension procedure in the future, the size of 3D NLFE model that is required to capture the bond behaviour between corroded reinforcement and concrete is investigated. Beam-end models and models of sub-sections were studied, and the results in terms of bond stress and crack pattern were compared. Preliminary results indicate good agreement for some situations; however for some cases a section model seems to overestimate the capacity.

This paper describes a novel method developed for the optimization of composite components against distortion caused by cure-induced residual stresses. A novel ply stack alteration algorithm is described, which is coupled to a parametrized CAD/FE model used for optimization. Elastic strain energy in 1D spring elements, used to constrain the structure during analysis, serves as an objective function incorporating aspects of global/local part stiffness in predicted distortion. Design variables such as the number and stacking sequence of plies, and geometric parameters of the part are used. The optimization problem is solved using commercial software combined with Python scripts. The method is exemplified with a case study of a stiffened panel subjected to buckling loads. Results are presented, and the effectiveness of the method to reduce the effects of cure-induced distortion is discussed. © 2023, The Author(s).

The present work is focused on the computational challenges and further verification and validation of an advanced fibre kinking model. This model was previously developed by the authors and implemented in a Finite Element (FE) code with a mesh objective formulation. The previous validation in terms of comparison with an analytical and micromechanical model is herein extended to also encompass FE simulations in longitudinal compression and multiaxial stress states. In addition, numerical improvements have been added to the model targeting its computational efficiency and stability in order to handle multiaxial stress states and large structures.

In the present study, the bake hardening (BH 240) steel sheet’s formability behavior is studied experimentally based on the Nakajima test method. A forming limit diagram is successfully constructed using universal sheet metal forming machine by offline measuring the strains of deformed specimens. In-process strain measurement based on a digital image correlation technique is also performed for a few selected samples to compare the results with manual strain measurement techniques. All the deformed specimens are also characterized to correlate the sample geometries with hardness values and microstructure. It is observed that the hardness value gradually decreases with an increase in sample width for all the deformed specimens up to the width of 150 mm, except for full-width sample of 200 mm. Microstructural analysis reveals that the morphology of ferrite grains changes with the sample geometry in all the deformed specimens. Microstructural characterization at the top surface of the specimen demonstrates that the aspect ratio of grains is maximum for a 25 mm width sample due to uni-axial stretching. It is also noted that grain’s aspect ratio is close to one (minimum) for a 200 mm width sample due to almost equi-biaxial elongation in grains. It is also observed that the aspect ratio of grains obtained from specimen cross-section indicates that the ratio increases gradually from 25 to 200 mm width samples. 

 Automated vehicles and active safety functions based on sensor technology have been identified by the automotive industry as catalysts for improved safety, sustainability, accessibility, and efficiency. As technology advances, the applications of these systems are constantly expanding. Alongside these advancements, methods must be developed to evaluate and test AD and ADAS system performance and reliability in relevant and repeatable ways. This work outlines the main challenges in developing and evaluating a test method for generating road spray, a turbulent mix of fine water particles that reduce visibility caused by vehicles driving on wet surfaces. A hardware prototype and an appurtenant evaluation process were designed and produced to realize the test method. The evaluation process includes an automated software tool to quantify the prototype’s ability to degrade visibility and a method for automating sensor calibration for data collection at different locations and times. One of the key findings is the challenge of eliminating external disturbances in the test environment. Factors such as light and wind conditions significantly affect visibility through spray. The work concludes that controlling these factors is essential for achieving test repeatability. We successfully recreated road spray in a controlled environment, attenuating a sensor’s perceptive ability in steps of up to 80%, repeatedly within ±5-15%.

The SESBE research project aims to develop novel smart sandwich façade elements with high insulating capabilities while providing a reduced thickness in conjunction with superior mechanical and durability properties. The present paper mainly focuses on the verification of the mechanical performance of the glass fibre reinforced polymer (GFRP) connectors in the façade element composed of reactive powder concrete (RPC) panels with foam concrete insulation between them. Because of the reduced thickness of the large façade elements, the performance of the connectors is critical for the entire structural concept. A description of structural performance and results based on experimental methods and finite element (FE) analysis are presented.

The ZD-tensile strength is tested by attaching the top and bottom sides of a paperboard to rigid blocks that are pulled apart. In a production laboratory the strength is recorded using a tape as an adhesive. In specialized laboratories a more thorough method is available that also measures the force-displacement curve of the sample. The advanced method involves laminating and gluing the paperboard sample to metal blocks which are mounted in a universal testing machine. 

In this study the advanced ZD-tensile method was refined by removing the glue step and laminating the paperboard directly to the blocks. The new method was validated against the regular method with adequate results. The limits of the refined method were explored with regards to ZD-strength and paper/paperboard thickness. 

In an attempt to unify the ZD-tensile and -compressive behaviour of paperboard, samples were laminated and tested in combined compression and tension testing. The compressive properties were compared to non-laminated samples. The laminated samples showed a different behaviour than the non-laminated samples. The flat slope seen in the initial part of the pure compression curve disappeared, replaced by a continuous response passing 0 N. The stiffness in this region resembled the response in tensile testing. 

Microelectronic packages are typically composed of different layers of materials with un-similar thermo-mechanical properties. Fabrication-induced residual stresses, resulting from the mismatch of layers’ thermo-mechanical properties, may lead to adverse effects such as warpage and delamination at the interface of layers. In this study, the fabrication process of the ball grid array (BGA) package was simulated to predict the thermal residual stresses through the thickness of the package. A finite element model incorporating realistic material behavior of the BGA package layers was developed. To this end, the epoxy molding compound (EMC) was modeled as a viscoelastic material, while the silicon chip, the die-attach, and the composite substrate were simulated using an elastic model during cooling. Since Young’s modulus of EMC is time and temperature-dependent, three different process temperatures were simulated to investigate the impact of viscoelastic properties of EMC, defined using Prony coefficients, on numerical residual stresses. To verify the simulation results, the incremental hole-drilling method was used to experimentally measure the residual stress components. It includes drilling a small hole at the center of a rosette strain gauge bonded on the BGA package surface and measuring the released strains on the surface. The relaxed strains were then converted to the residual stresses using a calibration matrix whose coefficients are determined from a finite element model. The reasonable agreement of numerical and experimental components of the residual stress throughout the thickness of the BGA package confirms the reliability of the proposed simulation approach in estimating residual stresses in microelectronics packages. 

Theoretically is glass one of the strongest materials. However, due to surface defects inevitably formed during manufacturing, transport, handling and use of glass, the practical strength is greatly limited by stress-concentrations at crack tips under tension. Glass has limited fracture toughness which gives a practical strength that spans over several orders of magnitude. Despite this is glass used in a wide range of applications, where architectural and automotive are among the most apparent applications for the general public. The unreliable strength requires an unnecessary thick glass and this has a direct consequence on the sustainability fingerprint. The recent advances and an outlook on improving the practical strength of glass are presented including the improvement of surface quality, improving mechanical properties, and strengthening of glass together with a concept of non-destructive testing (NDT) of the glass strength. NDT of glass is a game-changer that, among other things, enables quality-sorting in the glass industry.

Glass is a unique but unfortunately brittle material whose strength is primarily limited by the presenceof cracks on the surface [1]. The strength of glass is limited by the fact that very high stresses arise atthe crack tips when subjected to tensile load. In principle, without the presence of surface cracks, glasswould have a strength far exceeding many other structural materials, e.g., steel. The size and thedistribution of surface cracks vary greatly, which results in the strength of glass exhibit a great variationand thus requires that large safety margins must be applied for glass in practical applications, e.g., whenused as a load bearing building material.Today, there are no methods to determine the strength of flat glass non-destructively. Instead, thestrength is determined by different experimental methods requiring >10 samples for sufficient statistics.This procedure requires both lots of glassy materials and time. The future aim is to investigate if the useof nonlinear acoustic waves (NAW) could be an alternative for developing a standardized designstrength value. Developing a non-destructive inspection method for determining the glass strength is ascientific breakthrough that will have a great industrial impact for the sustainable development of glassmanufacturing.With the use of NAW it is possible to detect and quantify the defects in materials [2,3]. The nonlinearwaves are transmitted through the object and the nonlinear effects, caused by the defects in thematerial, corresponds to the level of damage in the material. This work present result from samplescontaining relatively precise defects. The defects were created using a microindenter with a sufficientload to cause indentation induced cracking in the glass. The indentations were created using a Vickersdiamond tip in the middle of commercial 4 mm float glass samples of the dimensions 10x10 cm2. Theapplied loads were 0.5N, 1N, 2N, 5N and 10N. The “damage value” of the sample series was thenquantified using the NAW technique. The fracture strength of the samples was correlated destructivelyusing a conventional ring-on-ring setup.The results show that there is a clear correlation between the indenter load, the damage value from theNAW inspection and the fracture strength. We noted that the standard deviation for the ring-on-ringtests for the 1N, 2N, 5N and 10N was low while the 0.5N and the reference samples presented a highstandard deviation. A possible explanation for this observation is that for 0.5N not all indents give radialcracks but in some cases the indentation produces only plastic deformation. The main conclusion fromthe research is that is possible to detect realistically large defects in glass using the non-destructive NAWmethod and these defects cannot be seen with the naked eye. Moreover, the results can be directlycorrelated with the strength of glass [4].

References[1] Veer, F.A. and Y.M. Rodichev, The structural strength of glass: hidden damage. Strength of Materials, 2011.43(3): p. 302-315. DOI: 10.1007/s11223-011-9298-5.[2] Persson, K., K. Haller, S. Karlsson, and M. Kozłowski, Non-destructive testing of the strength of glass by a nonlinearultrasonic method. Challenging Glass Conference Proceedings, 2020. 7. DOI: 10.7480/cgc.7.4498.[3] Haller, K., Doctoral Thesis: Acoustical measurements of material nonlinearity and nonequilibrium recovery.2008: Department of Mechanical Engineering, Blekinge Institute of Technology.[4] Karlsson, S., L. Grund Bäck, S. Andersson, K. Haller, M. Kozłowski, and K. Persson, Strength classification of flatglass for better quality – validation of method by well-defined surface defects and strength testing, in ÅForskReport,19-479. 2021: http://dx.doi.org/10.13140/RG.2.2.32992.40962.

The current project was a collaborative project between the involved partners: RISE Glass, Lund University and Acoustic Agree. It is funded by ÅForsk (Grant No. 19-479). The project is a follow-up project from a Smart Housing Småland (Grant No. 2016-04218) pre-study where we used a nonlinear acoustic wave (NAW) to determine the damage value in float glass simultaneously with four-point bending tests. Glass is a brittle material whose strength is primarily determined by its surface characteristics i.e., the presence of flaws, defects or cracks on the surface. The strength of glass is greatly limited by stress-concentrations at the crack tips generating very high stresses when the glass is under load. The size and distribution of surface defects vary greatly, this gives a great variation of strength of glasses so that conventionally very large safety measures must be employed for glass products. If these defects and/or cracks could be detected in a non-destructive way, it would be beneficial for glass manufacturers as well as final building users. Nonlinear acoustic wave (NAW) techniques can be used to detect defects in materials. In these methods, acoustic waves are transmitted through an object and nonlinear effects, caused by the defects in the material, is analysed from the signal obtained at the receiver. The aim of the current project was to establish a calibration and a clear correlation between nonlinear acoustic wave measurements and the ultimate strength of annealed glass samples with controlled defects. Controlled defects were made as indentation imprints with a microindenter, equipped with a Vickers diamond head, in the middle of float glass samples with the dimensions 4×100×100 mm3. The applied loads were 0.5N, 1N, 2N, 5N and 10N. The indents were inspected with a microscope in order to see the cracks and the depth of the indents were also determined. The formed defects (cracks) were detected with NAW technique. Analysing the waves after propagating in the glass the nonlinear content in the wave was analysed. Due to the objects damage, the propagated wave distorts proportionally to the damage. After the NAW-inspection the strength of the glass samples were tested with ring-on-ring tests. Using the results from NAW-inspection, a clear correlation between the nonlinear response and the indenter load was found. There was also an obvious correlation between the failure load on the ring-on-ring-tests and the indenter load. The standard deviation for the ring-on-ring-tests for the 1N, 2N, 5N and 10 N was low but for the 0.5 N load was very high. A possible explanation is that the indenter imprint in most of the cases only gave rise to plastic deformation and in some samples, cracks were formed too. There were visible cracks for all the higher indenter loads and thus a lower scatter of the results. The main conclusion of the project is that it is possible to detect small cracks, which cannot be seen with the naked eye, with NAW technique and it can be directly correlated to the strength of the glass.

The present paper describes a method for non-destructive testing of the glass strength. Square 10 × 10 cm2 samples of annealed float glass was inflicted with a controlled defect in the centre of the atmospheric side using Vickers microindentation-induced cracking with a force of 2 N, 5 N and 10 N and compared to an un-indented reference. The samples were non-destructively tested using a nonlinear acoustic wave method resulting in defect values. The average of the defect values was found to linearly correlate to the indentation force in a log–log relationship. The samples were subsequently tested in a ring-on-ring setup that allows for an equibiaxial stress state. The indentation-induced cracking gave practically realistic strength values in the range of 45 to 110 MPa. The individual sample values for failure stress as a function of normalized defect value show linear trends with approximately half of the data within 95% confidence limit. In summary, this study provides an initial proof-of-concept for a non-destructive testing of the strength of glass.

I dagsläget finns endast förstörande metoder för att bestämma hållfastheten för planglas. Det har medfört att på grund av den stora spridningen i hållfasthet av planglas behöver man ta till en stor säkerhetsfaktor. En ”säker” designhållfasthet som med andra ord behöver vara så låg så att risken är minimal att glaset går sönder. Resultatet blir att onödigt mycket glas används eftersom glas i princip alltid är starkare än designhållfastheten. Dessutom finns det idag heller ingen metod som kan mäta att glaset faktiskt upprätthåller designhållfastheten. Det finns med andra många skäl, både miljömässiga och kvalitetsskäl, till att utveckla en icke-förstörande metod till att bestämma hållfastheten av planglas. 

A method to estimate the stress-free temperature in a rail by exciting the complete track has been theoretically investigated, by both simple beam theory and by a finite element model. For frequencies below a cut-off frequency, bending waves cannot propagate in the track. The cut-off frequency primarily depends on the stiffness of the lateral ballast. For a given ballast stiffness, the wavelength (or speed) of propagating waves depends on the axial stress in the rail. By first determining the cut-off frequency, the ballast stiffness can be determined. Then, the actual stress can be estimated by measuring the wave speed. By knowing the actual rail temperature, the stress-free temperature is then easily calculated. It is found that stress-free temperatures of 5 °Cshould cause measurable changes in the speed of wave propagation. It is determined that variations in damping of the ballast and stiffness of the pads in the rail clamps do not influence the results. Field measurements show that a track can be excited and propagating waves detected.

The longitudinal load in rail caused by thermal expansion must be regularly monitored in order to avoid buckling or rail fracture. Different methods of monitoring with benefits and drawbacks are used or suggested. In this paper one of the proposed methods is investigated by a full-scale experiment. The aim is to measure the change in wavelength of the bending wave caused by the longitudinal load. In contrast to other vibration methods, this method does not require knowledge of the boundary conditions. However, it requires very accurate measurements, advanced finite element (FE) calculations, and sophisticated data analyses. The full-scale experiment shows that this is a method with potential. On the basis of the results of the full-scale experiment the required accuracy of the different steps in the method are clarified. Influence of measurement accuracy, loosened clamps at the sleepers, FE mesh size, degree of wear of the rail, and inaccuracy in the material parameters is considered.

The work presented in this report focuses on estimating maximum gas temperatures at ceiling level during large tunnel fires. Gas temperature is an important parameter to consider when designing the fire resistance of a tunnel structure. Earlier work by the authors has established correlations between excess ceiling gas temperature and effective tunnel height, ventilation rate, and heat release rate. The maximum possible excess gas temperature was set as 1350°C, independent of the tunnel structure and local combustion conditions. As a result of this research, two models have been developed to better estimate possible excess maximum gas temperatures for large tunnel fires in tunnels with differing lining materials and structure types (e.g. rock, concrete). These have been validated using both model- and full-scale tests. Comparisons of predicted and measured temperatures show that both models correlate well with the test data. However, Model I is better and more optimal, due to the fact that it is more conservative and easier to use. The fire duration and flame volume are found to be related to gas temperature development. In reality, the models could also be used to estimate temperatures in a fully developed compartment fire.

The critical velocity and backlayering length in sloped tunnels are investigated by numerical simulations using FDS. Simulation in two full-scale tunnels, with negative slopes ranging up to -18 % and heat release rates from 5 to 100 MW were carried out.

The results show that NFPA 502 equation significantly overestimates the effect of negative slopes.

The equation proposed by Atkinson and Wu is found to be in closer agreement with the results. A simplified correlation, i.e. Eq. (12), is proposed and recommended for practical use.

The previous correlation for dimensionless backlayering length, Eq. (3), is valid for tunnels of various slopes and aspect ratios, and can be used for prediction of backlayering length.

Vibration injury in the hand–arm system from hand-held machines is one of the most common occupational health injuries. Machines emitting high-frequency shock vibrations, e.g., impact wrenches have since long been identified as a special risk factor. In legislative and standard texts, the terms shock, impact, peak and transient vibration are frequently used to underline the special risks associated with these kinds of vibrations. Despite this fact, in the literature there is not a mathematically stringent definition of either shock vibration or how the amplitude of the shock is defined. In this study, we suggest algorithms for definition and quantification of these terms and apply them to machine vibrations of various kinds.

The purpose of this paper is to numerically simulate the in-plane behaviour of rammed earth walls under cyclic shear-compression tests. The experimental testing allowed obtaining the maximum horizontal loads, the displacement capacity and the level of non-linear behaviour of the respective load-displacement relationships as well as the failure modes. The calibration of the numerical model (finite element method) was carried out based on the experimental results. Within this framework, a micro-modelling approach was considered. The behaviour of the rammed earth material was simulated using a total strain rotating crack model. A Mohr-Coulomb failure criterion was used to reproduce the behaviour of the interfaces between the layers. Although the numerical results achieved a satisfactory agreement with the experimental results a sensitivity analysis of the parameters involved was performed. The sensitivity analysis aimed at determining which parameters of the model have a significant impact in the model's results. As expected the sensitivity analysis pointed out that the sliding failure occurrence is mainly influenced by two parameters of the interface elements: the interface tensile strength fit and the friction angle φ. Moreover the cohesion c and the layers thickness showed a limited effect on the shear behaviour. It should be noted that the results mentioned above are related to the cases where a significant level of vertical compressive stress σ is employed.

This paper studies the sequence of fibre kinking, the fibre lock-up and the subsequent constitutive behaviour. The conditions governing these phenomena are discussed with focus on the conditions for fibre lock-up. Lower bounds for the fibre lock-up angle a and the kink band angle b are derived purely from geometrical conditions for 3D arrays of fibres, with the aim to define the termination of fibre kinking in homogenized material models for FE analysis. It is concluded that the limit of the lock-up angle is 90° for low fibre volume fractions, decreases to about 50° for fibre volume fractions common in high performance composites, and reaches zero for fully packed fibres.

Cost and time for stamping die tryouts are significant within the car industry. A major contributing factor is that elastic deflections of stamping dies and presses are usually not considered during the virtual die design and forming simulation phase. Active surfaces of stamping dies are only cambered based on previous experiences of tool types and stamping presses. However, almost all stamping dies and presses are unique, and available experiences are not valid for new sheet materials. This leads to component deviations and often several loops of tool adjustments are needed. Previously partners within the SMART Advanced Manufacturing research project CAMBER have developed advanced deflection measuring devices to quantify the elastic deformations of stamping presses. Using these measurements, cambering methodologies can be utilized in sheet metal forming simulations. In this paper numerical substitutive stamping press models are described which are capable of compensating for measured stamping press dynamics. The result show that a numerical compensated tool can improve the contact by over 80% compared to the corresponding contact without compensation.

MoodyMarine is a weakly nonlinear potential flow model for wave-body and mooring  simulations with a graphical user interface. In this work we present the extension of the model to deal with constrained multi-body dynamics. By combining different translation and rotation constraints most joints can be modelled. As the constraints are imposed through springs and dampers in the explicit time-stepping algorithm, a slight manual tuning is required to make sure the bodies are constrained properly. Nevertheless, this tuning is shown not to influence the final results. In the paper we compare to existing test cases in literature as well as against experimental data. In all test cases there is a good agreement between the target solutions and MoodyMarine .

This study presents a modeling approach for predicting strain localization during sheet metal stamping processes focused on automotive engineering applications. The so-called stretching-to-bending ratio, ρ, is proposed to characterize the loading conditions acting on an element during stamping processes. Then, localized strain or necking strain is suggested to be a function of ρ. Different stretch–bending tests with different tool radii, i.e., R3, R6, R10, and R50 are conducted for two automotive sheet metals, DP800 and AA6010, to identify their forming limits under combined stretch–bend loads. The calibrated necking limit curve of the AA6016 sheet is then employed in AutoForm R10 software to predict the necking and failure of a stamped panel. Agreement with the experimental observation of failure positions of the panel validates the usefulness of the proposed modeling approach in practice. 

Cost and time for die tryout are significant within the car industry, and elastic deflections of dies and presses are most commonly not considered during the virtual die design and forming simulation phase. Because of this, active surfaces of stamping dies are only cambered based on previous experiences of tool types and presses. However, almost all stamping dies and presses are unique, and available experiences are not valid for new materials. Partners within the Eureka SMART Advanced Manufacturing research project CAMBER have developed advanced deflection measuring devices to quantify the elastic deformations of presses. Using these measurements, cambering methodologies can be utilized in sheet metal forming simulations. Important breakthroughs in recent years enabling the cambering methodology consists of efficient simulation strategies for full scale simulations with elastic dies and optimization techniques for creating substitutive press structures based on measurements. Furthermore, modern press deflection measurement methods are beneficial in applications such as Industry 4.0, predictive maintenance, product quality control, etc. through a more advanced understanding and live monitoring of the press system.

A multi-level structural assessment strategy for evaluation of response and load carrying capacity of reinforced concrete bridges deck slabs are presented [1]. The strategy is based on the principle of successively improved analysis methods in structural assessment. It provides a structured approach to the use of simplified as well as advanced non-linear finite element analysis methods. The proposed methods were used for analysis of previously tested slabs subjected to bending and shear type of failures. As expected, the advanced methods gave an improved understanding of the structural response and were capable of demonstrating higher, yet conservative, predictions of the load-carrying capacity. The proposed strategy clearly provides the engineering community a framework for using successively improved structural analysis methods for enhanced assessment in a straightforward manner.

Fracture modeling and experimental validation of Compacted Graphite Iron (CGI) specimens loaded under quasi-static conditions at room temperature are considered. Continuum damage mechanics coupled to plasticity is adopted to describe the evolution of damage. The damage production is based on a recently developed rate dependent damage evolution law, where the damage–plasticity coupling is modeled based on a damage driving energy that involves both stored energy and plasticity contributions. To describe ductile fracture accounting for stress triaxiality on the damage initiation, the inelastic contribution to the damage driving energy is controlled by the Johnson-Cook failure criterion. Three different damage models are defined based on elastic/inelastic damage driving energies. The damage models are validated against experiments on a set of notched specimens made of CGI with different notch geometries, where the global force-displacement curves and corresponding strain fields are obtained using digital image correlation technology. It is shown from the testing and the simulations that plastic strains generally need to be accounted for in order to properly describe the different failure processes of the CGI specimens. In addition, the ductile damage model is shown to more accurately predict the experimental force-displacement response as compared to the more simplistic stress drop, element deletion technique. 

Under seismic actions, stone masonry buildings are prone to damage. To assess the severity of damaged masonry buildings and their failure modes, engineers connect these problems to surface crack features, such as the crack width and the extent of cracking. We aim to further these assessments in this study, wherein we propose using simple machine learning models to predict: 1) three ratios encoding the degradation of stiffness, strength, and displacement capacity of damaged rubble stone masonry piers as a function of the observed crack features and the applied axial load and shear span ratio; and 2) the pre-peak vs. post-peak regime, based on the crack features. When predicting the stiffness, force, and drift ratios, the prediction error is significantly reduced when the axial load and shear span ratio are included in the feature vector. Furthermore, when predicting the pre-peak vs. post-peak regime, simple machine learning models such as the k-nearest neighbor and the logistic regression result in remarkable accuracy. The obtained results have significant implications on the automated post-earthquake assessment of masonry buildings using image data. It is shown based on documented laboratory test data, that, by selecting proper crack features and incorporating information about the kinematic and static boundary conditions, even simple machine learning models can predict accurately the damage level caused to a rubble masonry pier. The three crack features used in this study are the maximum crack width, length density, and complexity dimension. The pipeline developed in this paper is general enough and is applicable to other masonry typologies and elements upon new evaluation of crack features and image data.

Shock load caused by underwater explosion in naval battles can lead to malfunction of the equipment on-board naval vessels. It makes the ships vulnerable and they can lose the ability to accomplish their missions. This study presents a shock analysis, using the dynamic design analysis method (DDAM), of a naval ship stern ramp subjected to a non-contact underwater explosion. The objective is to evaluate the performance of the ramp subjected to a shock load, identify areas for structural improvements and recommend design changes. The DDAM in the commercial software ANSYS is used in the evaluation of the ramp. The structural response to the shock load is estimated by combined modal and response spectrum analyses. The shock load is applied in three directions (vertical, fore and aft, athwart ships) and the results show that the vertical direction is the most severe loading direction and critical to the functionality of the ramp. A parametric study is presented which shows which parameters that influence the most the structural response. The results from this study are used to suggest improvements of the ramp structure to make it more resistant to shock loads.

Introduction/Purpose

Europe’s railway industries require a step change in technologies and design for the next generation of railway vehicles in order to remain competitive globally. One way is use of composite materials that can reduce the weight of railway vehicles. Safety regulations for fire, smoke & toxicity requirements in the railway sector limits which materials that can be used for the composites and require special flame-retardant additives. The mechanical properties need to be asserted to reach the demands given by railway standards such as EN 12663. These standards are written for metallic materials requiring adaptation when designing and testing with composite materials.

To address this, the EU funded project Mat4Rail – “Designing the railway of the future: Fire resistant composite materials and smart modular design” have been formed. It is part of the Shift2Rail program.

Methods

To find composites that meet the demands for fire safety and high mechanical strength, different combinations of resins and fibers are tested. The resins that are investigated are epoxies, benzoxazines and hybrid chemistry together with additives for enhanced fire performance. The fibers that are investigated are carbon, glass and basalt.

The manufactured composite combinations are tested for reaction to fire EN 45545-2 and fire resistance EN 45545-3. The composites with the best fire-performance results are then further characterized for mechanical properties. A crucial property is the fatigue strength which is performed to harmonize with EN 12663-1 that is written with metals in mind. Several types of static tests are also performed.

Another topic is adhesive joints for composites that also are investigated for fire performance and mechanical properties. Results Composites reaching higher hazard levels of EN 45545-2 are developed. For these are static strengths and SN-curves determined.

Conclusions

It is shown that composite material can be used for railway applications e.g. carbodyshell parts.

The method Variation and Mode Effect Analysis (VMEA) is successfully implemented for the AGMA based gear design of the rack pinion mechanism. The rack and pinion is a feature in Ocean Harvesting Technologies (OHT) gravity accumulator device. The purpose of it is to make the electrical power output to the grid more uniform. This is a novel technology where previous experience in designing is absent. The VMEA method is there for useful for incorporating all known uncertainties to estimate the uncertainty and reliability of the technology. This allows for adequate safety factors to be set so the desired reliability can be achieved.

The uncertainty and reliability analysis is performed for different OHT designs and methods where the reliability is calculated. This calculation can be used as basis for further analysis when more design details are determined and modifications are made, thus allowing for more optimized and reliable design to be made.

Sustainability is not only a matter of choosing durable stone types for a specific application. It is also about theenergy consumed during the production, transportation and placing of the stone. It is also about dimensioningand shaping of the stone properly for the actual construction and the stone together with other materials in theconstruction. This contribution deals with the latter and is a case study on a failed paving construction.Stone paving is the collective expression for the use of stone slabs, setts and kerbs for exterior paving purposes.There are three European product standards in force; EN 1341, 1342 and 1343 respectively. These standardsdescribe e.g. how to denominate the products, the allowed dimensional tolerances and which technical propertiesto validate. There is little or no information on the actual usage of these products. Such information has generallyto be elaborated by each country.The standard way of construction for pavements is non-bonded laying of elements in crushed sand/splitmixtures. Under special loads and cleaning requirements this traditional, unbound construction method easily failsand a bound construction is needed. The structural integrity of an unbound pavement construction is maintainedon the basis of friction and mechanical interlock. Energy from traffic loading enters the structure via the surfacecourse, some of this energy is dissipated within the surface course itself and some is transmitted into the beddingcourse and thereafter the supporting base layers beneath. There are two structural elements in the surface course,the setts and the jointing medium. The jointing medium has physical properties which are important to consider,such as stiffness modulus, resistance to shear et al, which crucially affect the manner in which the pavementresponds to applied loads.Sufficient friction between the various components is crucial but is not generated and mechanical interlock notexercised without movement of the component parts of the structural model. The unbound paving is not a rigidconstruction and the various parts of this structural model must be mobilised in order that friction is generated.The paving is therefore also heavily dependant upon the unseen surface finishing of the setts (and slabs). In orderto adequately generate friction between the paving element and both bedding and jointing materials the unseensurfaces have to be rough, preferably a cleft or riven surface, to function properly.There are two distinct categories of setts, shallow setts and full setts, each requiring a different approach:Shallow setts are those having depth less than width.Specifying shallow setts makes a more economical use of the raw material used in their manufacture but thepavement construction requires to designed more carefully and there is an upper limit to the level of traffic whichcan be carried. A concrete base must be provided when specifying shallow setts.Full setts are those having depth not less than width.For many centuries the "golden rule" was that setts must be at least as deep as they are wide. The heavier thetraffic loading, the deeper the sett in relation to its width. Before the advent of concrete and mortar, when jointing,bedding and supporting base were all unbound, this rule was very necessary. Even with the development of highperformance mortars and reinforced concrete for a base, we need to use full setts when the traffic loading exceedsa given maximum.The deeper the sett in relation to its width, the more the strength of the pavement is taken by the joints between thesetts. So, with deep, full setts we can sometimes lay over an unbound or a bituminous base, even for heavy traffic.As can be seen, these simple rules given above depend on proper definition of the traffic loads. i.e. numberof vehicles per day and the weight of them. When the general rules are not followed the stones start to move inan uncontrolled manner. Some cases and one in particular will be detailed in this presentation. The case studiesdemonstrate the importance of the necessary knowledge needed to build a paving that can cope with the dynamicand static traffic loads. In addition, it shows the problem that may arise due to a poorly defined border betweensetts and slabs.

Failure of reinforced concrete (RC) slabs in punching has been a challenging problem for nonlinear finite element (FE) analysis. To improve the analysis approach, this study was conducted by developing a nonlinear FE analysis method for slabs subjected to punching failure, using three-dimensional continuum elements. The influence of several modelling choices were investigated by comparing such results as load carrying capacity, load-deflection response and crack pattern from the FE analyses with available experimental data. The proposed method show the possibility of accurately predicting the load-carrying capacity and realistically describing the behaviour of slabs.

This study was conducted by carrying out nonlinear FE analysis of RC slabs subjected to punching failure, using three-dimensional (3D) continuum elements. The influence of several modelling choices for concrete material were investigated by comparing results such as load-carrying capacity, load-deflection response and crack pattern from the FE analyses with available experimental data. The analyses of the tested slabs show possibility to accurately predict the load-carrying capacity and realistically simulate the behavior of slabs using the proposed method.

Failure of reinforced concrete (RC) slabs without shear reinforcement in punching has been a challenging problem for nonlinear finite element (FE) analysis. To improve the analysis approach, this study was conducted by developing a nonlinear FE analysis method for slabs subjected to punching failure without shear reinforcement, using three-dimensional continuum elements. The influence of several modelling choices were investigated by comparing such results as loadcarrying capacity, load-deflection response and crack pattern from the FE analyses with available experimental data. The proposed method shows the possibility of accurately predicting the load-carrying capacity and realistically describing the behaviour of slabs.

Fibre-reinforced polymer composites are widely used in structural applications due to their high specific stiffness and strength. In some applications the response of dynamically loaded composite components must be analysed. For example, in crash analyses of structural components, where very high loading rates occurs, the composite behaviour is not fully understood. For this, we present a novel transversely isotropic viscoelasticviscoplastic constitutive model for a unidirectional carbon-epoxy composite. The model is micromechanically motivated so that the matrix and fibre materials of the composite are treated as micromechanical constituents at the ply scale. Based on the Hill-Mandel condition, the phases are homogenized via the macroscopic and fluctuating strain fields. To arrive at a simple but still representative model, a simplistic ansatz is applied to the structure of the fluctuating strains leading to a non-standard homogenized response of the composite. The model is applied to the non-linear rate dependent anisotropic ply behaviour under quasi-static and dynamic loading at different off-axis angles. For a simple viscoelastic-viscoplastic prototype for the rate dependent matrix response, there is a good correlation between measured and model response of the IM7-8552 material system in compression and tension.

Strain-rate effects in a unidirectional non-crimp fabric carbon/epoxy composite are addressed. To allow for kink-band formation including strain-rate effects and damage in such composites, the paper advances a recent model focused on compression loading at small off-axis angles. The model is based on computational homogenization with a subscale represented by matrix and fibre constituents at finite deformation. The fibre constituent is assumed to be elastic transversely isotropic and the matrix is viscoelastic–viscoplastic with damage degradation. Novel model improvements of special importance to small off-axis loading relate to the isostress formulation of the homogenized response in transverse shear. In this context, an enhanced homogenized elastic response is proposed based on Halpin–Tsai corrections to account for the nonuniform stress distribution on the microscale. The model captures the strongly rate sensitive kink-band formation due to localized matrix shearing and fibre rotation, confirming the experimentally observed increase in compressive strength for high strain rates. © 2022 The Author(s)

This study has compared different methods for measuring residual stresses in high pressure aluminium castings. The hole-drilling and X-ray diffraction method were used. A stress lattice were used. The results from the measurements were then compared with simulations of residual stresses. The effect of different heat transfer related parameters were investigated and correlated to measurements. It has in present work been shown that deviations in measured stresses is to be expected, especially at the surface and in positions where large stress gradients are present. Compressive stresses were the dominating stresses at the surface for all measuring points. The principle stresses then increased inwards. The simulations were based on both qualitative and quantitative aspects. Both relaxation of strains during drilling and stresses were evaluated and compared to measurements. The initial heat transfer coefficient (h0) in combination with a highly resolved model the first millimeter had the largest impact on the simulation results. The use of an extremely high h0 gave the best results, both from a qualitative and quantitative aspect. A high h0 gave lower stresses at the surface compared with a lower h0. The stress gradient inwards from the surface were also in better conformity compared to a low h0. The stresses at 1 millimeter were not however influenced at all from the h0. Simulations were also performed on two industrial components, one die and one high pressure cast. However, they had been subjected to different post-processing steps after they were cast, one shoot peened and one T6-treated. Therefore no valid comparisons could be performed.

In assessing existing structures, inspection results need to be linked to the effects on load-carrying capacity; to provide such information, this study has investigated the correlation between splitting crack width, corrosion level and anchorage capacity. The study was based on 13 reinforced concrete beams that had been exposed to natural corrosion for 32 years, 11 beams with splitting cracks and 2 without. The crack pattern and widths were documented before undergoing structural testing of anchorage capacity. Thereafter, the reinforcement bars were extracted and their corrosion levels measured using two methods, gravimetric weight loss and 3D scanning. The corrosion level from the weight loss method was approximately twice as large; possible reasons are horizontal or subsurface corrosion pits, and the cleaning method. Further, for the same corrosion level, the specimens in this study had much larger crack widths and slightly lower bond capacity than the artificially corroded tests in the literature; a possible reason is that these specimens had been subjected to combined corrosion and freezing. However, the corrosion level and reduction in bond capacity related to crack width were both lower in the present than in previous studies in the literature. Thus, by formulating a damage indicator from the damage visible in the form of crack widths from artificial test data, the structural capacity is estimated to be on the safe side.

In the framework of the Cost Action CERTBOND (Reliable roadmap for certification of bonded primary structures), a wide group of researchers from 27 European Countries have had the opportunity to work on the topic of certification of bonded joints for primary structural applications from different engineering sectors such as the aerospace, automotive, civil engineering, wind energy and marine sectors. Since virtual testing and optimization are basic tools in the certification process, one of the key objectives of CERTBOND is to critically review some of the available models and failure theories for adhesive joints. The present paper summarizes the outcome of this task. Nine different models/theories are described in detail. Specifically, reviewed are the Classical Analytical Methods, the Process Zone Methods, Linear Elastic Fracture Mechanics (LEFM), the Virtual Crack Closure Technique (VCCT), the Stress Singularity Approach, Finite Fracture Mechanics (FFM), the Cohesive Zone Method (CZM), the Progressive Damage Modeling method and the Probabilistic methods. Also, at the end of the paper, the modeling of temperature effects on adhesive joints have been addressed. For each model/theory, information on the methodology, the required input, the main results, the advantages and disadvantages and the applications are given. © 2021 The Author(s). 

Textile reinforced concrete (TRC) is an innovative high performance composite material which has revealed many promising attributes in various applications but test methods and reliable numerical models need to be established to reduce uncertainty and the need for extensive experimental studies. The aim of this paper was to evaluate the flexural behaviour of carbon textile reinforced TRC slabs both experimentally and numerically along with the characterization of the material and interaction level properties. The experimental results characterizing the bond behaviour were linked to the experimental behaviour of a rectangular TRC slab in bending through numerical analyses. A 2D macro-scale FE-model of the tested TRC slab was developed based on the related experimental input. Comparison of the numerical results to the experiments revealed that the flexural failure was governed by bond, and reasonable agreement was obtained in terms of crack development, deflections, maximum load, and failure mode. Accordingly, the experiments further indicated that the flexural behaviour of TRC slabs is greatly influenced by the bond quality.

In this paper, both experimental and numerical methods are presented to gain an understanding of the structural behaviour related to a TRC sandwich panel with a glass fibre reinforced polymer (GFRP) plate connection system. Double shear tests were conducted on component-scale sandwich panels to characterize the available shear capacity provided by the connectors and panel configuration. Three-dimension (3D) non-linear Finite Element Analysis (NLFEA) was applied to develop a model for the design of TRC sandwich panels while focusing on the connectors. The experimental outcome of the shear tests was applied to validate the corresponding numerical model developed in this work. The need for further modifications to the design of the shear connectors or other parameters such as panel thickness can be established accordingly. This developed FE model can essentially be applied as a design tool to further predict the structural behaviour of the full-scale sandwich elements.