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The paper aims to shed some light on the effect of the notch/crack‐tip stresses and their role on the cyclic plasticity and crack growth behavior in compression‐compression fatigue.

Compression precracking was studied using 2D finite element analysis for CT specimen. The final crack length and the shape of the crack front were compared with those obtained experimentally.

It has been found that cyclic plasticity and stress redistribution govern the observed fatigue crack growth behavior in compression‐compression precracking. Only the internal stress corresponding to P_max shows a significant redistribution with the crack extension whereas the stress corresponding P_min is not affected by the increase of crack length.

This results are limited to Mode I cracking.

It supports that two thresholds, ΔK^th and K_max^th, govern the fatigue crack behavior. When the contribution from the internal tensile stress is not big enough to make K_max exceed K_max^th the crack will self arrest.

It has been found that cyclic plasticity and stress redistribution govern the observed fatigue crack growth behavior in compression‐compression precracking. The comparison of the numerical results with experimental data in terms of final crack length and crack front shape indicated a fair agreement.

The purpose of this paper is to obtain the mechanical behavior and damage mechanism of the coal and rock near the stope under the stress state and stress paths of the surrounding rock with the dynamic mining.

Through the three-axial compression test and the uniaxial compression test by meso experiment device, the mechanical behavior and fracture evolution process of coal and rock were studied, and the acoustic emission (AE) characteristics under uniaxial compression of the coal and rock were contrasted.

Under the three-axial compression, the strength of coal and rock enhance significantly by confining pressure. The volume of outburst coal shows obvious stages: compression is followed by expansion. The coal first appear to undergo compaction under vertical stress due to volume decrease, but with the development of micro- and macro-cracks, the specimens appeared to expand; under the uniaxial compression, through the comparison of stress–strain relationship and the crack propagation process, stress drop and fracture of coal have obvious correlation. The destruction of coal was gradual due to the slow and steady accumulation of internal damage. Due to the influence of the end effect, the specimens show the “conjugate double shear failure”. The failure process of the coal and rock and the characteristics of the AEs have a corresponding relationship: the failure causes a large number of AE events. Before the events peak, there was an initial stage, calm growth stage and explosive growth stage. There were some differences between the rock and coal in the characteristics of the AE.

These research studies are conducted to provide guidance on the basis of mine disaster prevention and control.

The purpose of this study is to investigate the manufacturability of Fe-3Si lattice structures and the resulting mechanical properties. This study could lead to the successful processing of squirrel cage conductors (a lattice structure by design) of an induction motor by additive manufacturing in the future.

The compression behaviour of two lattice structures where struts are arranged in a face-centred cubic position and vertical edges (FCCZ), and struts are placed at body-centred cubic (BCC) positions, prepared by laser powder bed fusion (LPBF), is explored. The experimental investigations are supported by finite element method (FEM) simulations.

The FCCZ lattice structure presents a peak in the stress-strain curve, whereas the BCC lattice structure manifests a plateau. The vertical struts aligned along the compression direction lead to a significant increase in the load-carrying ability of FCCZ lattice structures compared to BCC lattice structures. This results in a peak in the stress-strain curve. However, the BCC lattice structure presents the bending of struts with diagonal struts carrying the major loads with struts near the faceplate receiving the least load. A high concentration of geometrically necessary dislocations (GNDs) near the grain boundaries along cell formation is observed in the microstructure.

To the best of the authors’ knowledge, this is the first study on additive manufacturing of Fe-3Si lattice structures. Currently, there are no investigations in the literature on the manufacturability and mechanical properties of Fe-3Si lattice structures.

Selective laser melting (SLM) is a promising additive manufacturing technology in the field of complex parts’ fabrication. High temperature gradient and residual stress are vital problems for the development of SLM technology. The purpose of this paper is to investigate the influence of substrate characteristics on the residual stress of SLMed Inconel 718 (IN718).

The SLMed IN718 samples were fabricated on the substrates with different characteristics, including pre-compression stress, materials and pre-heating. The residual stress at the center of the top surface was measured and compared through Vickers micro-indentation.

The results indicate that the residual stress reduces when the substrate contains pre-compression stress before the SLM process starts. Both substrate thermal expansion coefficient and thermal conductivity affect the residual stress. In addition to reducing the difference of thermal expansion coefficient between the substrate and the deposited material, the substrate with low thermal conductivity can also decrease the residual stress. Substrate pre-heating at 150°C reduces nearly 42.6 per cent residual stress because of the reduction of the temperature gradient.

The influence of substrate characteristics on the residual stress has been studied. The investigation results can help to control the residual stress generated in SLM processing.

This study aims to present comprehensive nonlinear material modelling techniques and simulations of reinforced concrete (RC) beams subjected to short-term monotonic static load using the robust and reliable general-purpose finite element (FE) software ANSYS. A parametric study is carried out to analyse the flexural and ductility behaviour of RC beams under various influencing parameters.

To develop and validate the numerical FE models, a total of four experimentally tested simply supported RC beams are taken from the available literature and two beams are selected from each author. The concrete, steel reinforcements, bond-slip mechanism, loading and supporting plates are modelled using SOLID65, LINK180, COMBIN39 and SOLID185 elements, respectively. The validated models are then used to conduct parametric FE analysis to investigate the effect of concrete compressive strength, percentage of tensile reinforcement, compression reinforcement ratio, transverse shear reinforcement, bond-slip mechanism, concrete compressive stress-strain constitutive models, beam symmetry and varying overall depth of beam on the ultimate load-carrying capacity and ductility behaviour of RC beams.

The developed three-dimensional FE models can able to capture the load and midspan deflections at critical points, the accurate yield point of steel reinforcements, the formation of initial and progressive concrete crack patterns and the complete load-deflection curves of RC beams up to ultimate failure. From the numerical results, it can be concluded that the FE model considering the bond-slip effect with Thorenfeldt’s concrete compressive stress-strain model exhibits a better correlation with the experimental data.

The ultimate load and deflection results of validated FE models show a maximum deviation of less than 10% and 15%, respectively, as compared to the experimental results. The developed model is also capable of capturing concrete failure modes accurately. Overall, the FE analysis results were found quite acceptable and compared well with the experimental data at all loading stages. It is suggested that the proposed FE model is a practical and reliable tool for analyzing the flexural behaviour of RC members and can be used for performing parametric studies.

A nonlinear finite element (FE) beam-column model for the analysis of reinforced concrete (RC) frames with due account of shear is presented in this paper. The model is an expansion of the traditional flexural fibre beam formulations to cases where multiaxial behaviour exists, being an alternative to plane and solid FE models for the nonlinear analysis of entire frame structures. The paper aims to discuss these issues.

Shear is taken into account at different levels of the numerical model: at the material level RC is simulated through a smeared cracked approach with rotating cracks; at the fibre level, an iterative procedure guarantees equilibrium between concrete and transversal reinforcement, allowing to compute the biaxial stress-strain state of each fibre; at the section level, a uniform shear stress pattern is assumed in order to estimate the internal shear stress-strain distribution; and at the element level, the Timoshenko beam theory takes into account an average rotation due to shear.

The proposed model is validated through experimental tests available in the literature, as well as through an experimental campaign carried out by the authors. The results on the response of RC elements critical to shear include displacements, strains and crack patterns and show the capabilities of the model to efficiently deal with shear effects in beam elements.

A formulation for the nonlinear shear-bending interaction based on the fixed stress approach is implemented in a fibre beam model. Shear effects are accurately accounted during all the nonlinear path of the structure in a computationally efficient manner.

For size reasons, adapted sensors, able to measure intrinsic mechanical properties of fabrics, have not been developed yet. The study aims at developing a sensor that can be inserted within a specific textile, a “complex” fabric used as seat‐cover fabrics, and consisting of an assembly of three layers.

Piezoelectric polymer sensors containing polyvinylidene fluoride (PVDF) were chosen. A total of 20 “complex” were studied. A characterisation in compression was achieved, using the Kawabata Evaluation System. The best‐adapted measurement method using a PVDF sensor has been required. The method consists in analyzing the response under compressive stress of a PVDF disc using the resonant frequency of the material. A constraint series is applied to the fabric in the sensor area; the maximal phase at the sensor's resonant frequency is taken up for each one.

Phase variation is linear and differs according to the studied “complex”. A correlation study between Kawabata compression parameters and slopes did not show any relationship between slope values and compression properties when the surface fabrics of “complex” are compared, but a classification in “families” is possible when different foams are considered.

Further studies should demonstrate whether these “smart” textiles could find applications in the automotive field, to measure accurately the mass of a passenger. The influence of the external parameters (vibrations, temperature variations) has to be checked, knowing that the sensor is not depending on moisture. To complete the study, the sensor has to be tested in a real situation, i.e. inserted in a car‐seat, in contact with a human body.

This study promises development of a sensor that can be inserted into a specific textile, a “complex” fabric used as a seat‐cover, consisting of an assembly of three layers.

The analysis of ancient buildings presents professionals with important challenges, so it is necessary to have a rational methodology of analysis of these constructions. From the point of view of the technology of structures it is imperative to know the mechanical characteristics of the structural elements involved, as well as the existing stress levels. Currently the tendency is to obtain such knowledge in a non‐destructive way, producing minimal damage. The purpose of this paper is to provide a vision of some of the minor‐destructive techniques (MDT) applied to the diagnosis of historical rubble stone masonry structures.

The paper focuses attention on the employment of techniques based on mechanical stress aspects: flat jack, hole‐drilling and dilatometer, conducted on rubble stone masonry structures. Several computational models were made of parts of the building. These models were used to obtain experimental data (modulus of elasticity and Poisson's ratio). The accuracy of the models was contrasted through the comparison with compression stress levels obtained experimentally.

The paper provides a brief description of these MDT, and exposes the flat jack tests results obtained on several historical masonry walls in the Major Seminary of Comillas (Spain): Compression stress levels, modulus of elasticity and Poisson's ratio of several masonries of this building.

These techniques improve the computational models of constructions, because they can obtain a better knowledge of their mechanical properties, from experimental ways, and the calibration of models through experimental data.

This paper describes one of the first applications of these techniques in Spain.

The purpose of this paper is to focus on the production of scaffolds with specific morphology and mechanical behavior to satisfy specific requirements regarding their stiffness, biological interactions and surface structure that can promote cell-cell and cell-matrix interactions though proper porosity, pore size and interconnectivity.

This case study was focused on the production of multi-layered hybrid scaffolds made of polycaprolactone and consisting in supporting grids obtained by Material Extrusion (ME) alternated with electrospun layers. An open source 3D printer was utilized, with a grain extrusion head that allows the production and distribution of strands on the plate according to the designed geometry. Square grid samples were observed under optical microscope showing a good interconnectivity and spatial distribution of the pores, while scanning electron microscope analysis was used to study the electrospun mats morphology.

A good adhesion between the ME and electrospinning layers was achieved by compression under specific thermomechanical conditions obtaining a hybrid three-dimensional scaffold. The mechanical performances of the scaffolds have been analyzed by compression tests, and the biological characterization was carried out by seeding two different cells phenotypes on each side of the substrates.

The structure of the multi-layered scaffolds demonstrated to play an important role in promoting cell attachment and proliferation in a 3D culture formation. It is expected that this design will improve the performances of osteochondral scaffolds with a strong influence on the required formation of an interface tissue and structure that need to be rebuilt.

DOUGLAS and Carmichael (REF. 1) have suggested formulae relating the compressive strength at failure of short circular tubes with their ultimate tensile strength and thickness/radius ratio. Robertson (REF. 2) has tested Southwell's theoretical formula for thin‐walled circular tubes. Further tests on medium and thick tubes by the author have indicated that the new data and that of Douglas and Carmichael can best be correlated by the inclusion of yet another property of the tube material. The representation, within the specified limits, is extremely good and taken in conjunction with existing data on thin tubes, the strength of tubes under this loading condition can be predicted over a wide range of material properties and geometrical dimensions. Also included in the author's data are extensometer tests over the elastic and early plastic regions of compression. A comparison of the resultant proof stresses with those of control tensile tests verifies their equality except under certain interesting conditions.