Search results

This paper aims to clarify the relationship between mechanical behaviors and the underlying geometry of periodic cellular structures. Particularly, the answer to the following research question is investigated: Can seemingly different geometries of the repeating unit cells of periodic cellular structure result in similar functional behaviors? The study aims to cluster the geometry-functional behavior relationship into different categories.

Specifically, the effects of the geometry on the compressive deformation (mechanical behavior) responses of multiple standardized cubic periodic cellular structures (CPCS) at macro scales are investigated through both physical tests and finite element simulations of three-dimensional (3D) printed samples. Additionally, these multiple CPCS can be further nested into the shell of 3D models of various mechanical domain parts to demonstrate the influence of their geometries in practical applications.

The paper provides insights into how different CPCS (geometrically different unit cells) influence their compressive deformation behaviors. It suggests a standardized strategy for comparing mechanical behaviors of different CPCS.

This paper is the first work in the research domain to investigate if seemingly different geometries of the underlying unit cell can result in similar mechanical behaviors. It also fulfills the need to infill and lattify real functional parts with geometrically complex unit cells. Existing work mainly focused on simple shapes such as basic trusses or cubes with spherical holes.

The purpose of this paper is to investigate the mechanical properties’ behaviors of woven composite cut-out structures with specific parameters. Because of the complexity of micro-scale and meso-scale structure, it is difficult to accurately predict the mechanical material behavior of woven composites. Numerical simulations are increasingly necessary for the design and optimization of test procedures for composite structures made by the woven composite. The results of the proposed method are well satisfied with the results obtained from the experiment and other studies. Moreover, parametric studies on different plates based on the stacking sequences are investigated.

A multi-scale modeling approach is suggested. Back-propagation neural networks (BPNN), radial basis function (RBF) and least square support vector regression are integrated with efficient global optimization (EGO) to reduce the weight of assigned structure. Optimization results are verified by finite element analysis.

Compared with other similar studies, the advantage of the suggested strategy uses homogenized properties behaviors with more complex analysis of woven composite structures. According to investigation results, it can be found that 450/−450 ply-orientation is the best buckling load value for all the cut-out shape requirements. According to the optimal results, the BPNN-EGO is the best candidate for the EGO to optimize the woven composite structures.

A multi-scale approach is used to investigate the mechanical properties of a complex woven composite material architecture. Buckling of different cut-out shapes with the same area is surveyed. According to investigation, 45°/−45° ply-orientation is the best for all cut-out shapes. Different surrogate models are integrated in EGO for optimization. The BPNN surrogate model is the best choice for EGO to optimization difficult problems of woven composite materials.

The purpose of this paper is to describe the ageing behaviour of acrylate‐based resins for stereolithography (SL) technology using different test methods and to investigate these effects on polymers.

Controlling the polymer degradation requires an understanding of many different phenomena, including the different chemical mechanisms underlying structural changes in polymer macromolecules, the influences of polymer morphology, the complexities of oxidation chemistry and the complex reaction pathways of polymer additives. Several ageing characterization experiments are given.

The paper covers the ageing process analysis of acrylate‐based polymers. An overview of the ageing behaviour is given, along with the bandwidth of material characteristics for a prolonged lifetime of this material class.

For research and development in the field of rapid prototyping (RP) materials data about ageing behaviour and environmental effects are crucial. The authors show possible methods for measuring these effects and discuss the consequences in material research using a recently developed biocompatible SL resin as an example.

The study of the ageing behaviour of polymers is important for understanding their usability, storage, lifetime and recycling. The presented polymeric formulations are able to meet the growing demand for both soft and stiff manufacturing resin materials in the engineering and medical fields.

The analysis of the ageing behaviour of polymer materials is an important issue for engineering applications, recycling of post‐consumer plastic waste, as well as the use of polymers as biological implants and matrices for drug delivery and the lifetime of an article. The paper gives an overview of details involving ageing behaviour and their meaning for applications of acrylate‐based SL resins and is therefore of high importance to people with interest in long‐term behaviour and ageing of RP materials.

Additive manufacturing technologies such as, for example, selective laser melting (SLM) offer new design possibilities for a wide range of applications and industrial sectors. Whereas many results have been published regarding material options and their static mechanical properties, the knowledge about their dynamic mechanical behaviour is still low. The purpose of this paper is to deal with the measurement of the dynamic mechanical properties of two types of stainless steels.

Specimens for dynamic testing were produced in a vertical orientation using SLM. The specimens were turned to the required end geometry and some of them were polished in order to minimise surface effects. Additionally, some samples were produced in the end geometry (“near net shape”) to investigate the effect of the comparably rough surface quality on the lifetime. The samples were tension‐tested and the results were compared to similar conventional materials.

The SLM‐fabricated stainless steels show tensile and fatigue behaviour comparable to conventionally processed materials. For SS316L the fatigue life is 25 per cent lower than conventional material, but lifetimes at higher stress amplitudes are similar. For 15‐5PH the endurance limit is 20 per cent lower than conventional material. Lifetimes at higher stress also are significantly lower for this material although the surface conditions were different for the two tests. The influence of surface quality was investigated for 316L. Polishing produced an improvement in fatigue life but lifetime behaviour at higher stress amplitudes was not significantly different compared to the behaviour of the as‐fabricated material.

In order to widen the field of applications for additive manufacturing technologies, the knowledge about the materials properties is essential, especially about the dynamic mechanical behaviour. The current study is the only published report of fatigue properties of SLM‐fabricated stainless steels.

This paper aims to investigate the mechanical and thermal behavior, i.e. tensile strength, hardness, impact strength and glass transition temperatures of water-treated polyamide6/boric oxide (PA) composites.

The PA6 and PA6/boric oxide composites were exposed to an open environment and immersed in water for 15 days to analyze the effect of environmental humidity and frequent water immersion conditions on the composite’s mechanical and thermal properties. The tensile strength, elastic modulus, hardness and impact strength of materials were measured to identify the mechanical properties. The scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) characterizations were used to see the effect of humidity/water absorption on microstructure, crystallinity and glass transition temperatures.

The testing results revealed the loss in strength, elastic modulus and hardness, while the impact resistance was improved after exposure of materials to humidity/water. SEM images clearly show the formation of voids and XRD graphs revealed the loss in crystallinity after water immersion. The DSC plots of water immersed materials revealed the loss of glass transition temperatures up to 15°C.

The mechanical and thermal behavior of PA composites varies according to the surrounding atmosphere. Experiments were performed to investigate the influence of water treatment on the PA6/B₂O₃ composite’s mechanical and thermal properties. Water treatment resulted in the bonding between PA and water molecules, which generated voids in the materials. These voids generations are found the main reason for the low strength and hardness of water-treated materials.

The purpose of this paper is to examine the mechanical behaviour of additively manufactured Ti-6Al-4V under cyclic loading. Using as-built selective laser melting (SLM) Ti-6Al-4V in engineering applications requires a detailed understanding of its elastoplastic behaviour. This preliminary study intends to create a better understanding on the cyclic plasticity phenomena exhibited by this material under symmetric and asymmetric strain-controlled cyclic loading.

This paper investigates experimentally the cyclic elastoplastic behaviour of as-built SLM Ti-6Al-4V under symmetric and asymmetric strain-controlled loading histories and compares it to that of wrought Ti-6Al-4V. Moreover, a plasticity model has been customised to simulate effectively the mechanical behaviour of the as-built SLM Ti-6Al-4V. This model is formulated to account for the SLM Ti-6Al-4V-specific characteristics, under the strain-controlled experiments.

The elastoplastic behaviour of the as-built SLM Ti-6Al-4V has been compared to that of the wrought material, enabling characterisation of the cyclic transient phenomena under symmetric and asymmetric strain-controlled loadings. The test results have identified a difference in the strain-controlled cyclic phenomena in the as-build SLM Ti-6Al-4V when compared to its wrought counterpart, because of a difference in their microstructure. The plasticity model offers accurate simulation of the observed experimental behaviour in the SLM material.

Further investigation through a more extensive test campaign involving a wider set of strain-controlled loading cases, including multiaxial (biaxial) histories, is required for a more complete characterisation of the material performance.

The present investigation offers an advancement in the knowledge of cyclic transient effects exhibited by a typical α’ martensite SLM Ti-6Al-4V under symmetric and asymmetric strain-controlled tests. The research data and findings reported are among the very few reported so far in the literature.

This study aims to reveal the influences of three-dimensional (3D) printing parameters such as layer heights (0.1 mm, 0.2 mm and 0.4 mm), infill rates (40, 70 and 100%) and geometrical property as tapered angle (0, 0.25 and 0.50) on vibrational behavior of 3D-printed polyethylene terephthalate glycol (PET-G) tapered beams with fused filament fabrication (FFF) method.

In this performance, all test specimens were modeled in AutoCAD 2020 software and then 3D-printed by FFF. The effects of printing parameters on the natural frequencies of 3D-printed PET-G beams with different tapered angles were also analyzed experimentally, and numerically (finite element analysis) via Ansys APDL 16 program. In addition to vibrational properties, tensile strength, elasticity modulus, hardness, and surface roughness of the 3D-printed PET-G parts were examined.

It can be stated that average surface roughness values ranged between 1.63 and 6.91 µm. In addition, the highest and lowest hardness values were found as 68.6 and 58.4 Shore D. Tensile strength and elasticity modulus increased with the increase of infill rate and decrease of the layer height. In conclusion, natural frequency of the 3D-printed PET-G beams went up with higher infill rate values though no critical change was observed for layer height and a change in tapered angle fluctuated the natural frequency values significantly.

The influence of printing parameters on the vibrational properties of 3D-printed PET-G beams with different tapered angles was carried out and the determination of these effects is quite important. On the other hand, with the addition of glass or carbon fiber reinforcements to the PET-G filaments, the material and vibrational properties of the parts can be examined in future works.

As a result of this study, it was shown that natural frequencies of the 3D-printed tapered beams from PET-G material can be predicted via finite element analysis after obtaining material data with the help of mechanical/physical tests. In addition, the outcome of this study can be used as a reference during the design of parts that are subjected to vibration such as turbine blades, drone arms, propellers, orthopedic implants, scaffolds and gears.

It is believed that determination of the effect of the most used 3D printing parameters (layer height and infill rate) and geometrical property of tapered angle on natural frequencies of the 3D-printed parts will be very useful for researchers and engineers; especially when the importance of resonance is known well.

When the literature efforts are scanned in depth, it can be seen that there are many studies about mechanical or wear properties of the 3D-printed parts. However, this is the first study which focuses on the influences of the both 3D printing parameters and tapered angles on the vibrational behaviors of the tapered PET-G beams produced with material extrusion based FFF method. In addition, obtained experimental results were also supported with the performed finite element analysis.

Topologically interlocked materials are a class of materials in which individual unit elements interact with each other through contact only. Cracks and other defects occurring due to external loading are contained in the individual unit elements. Thus, topologically interlocked materials are damage tolerant and provide high structural integrity. The purpose of this paper is to investigate the concepts of remanufacturing in the context of a material for which the intended use is structural such that the material's structural integrity is of concern. In particular, the study is concerned with the mechanical behavior of a topologically interlocked material.

A topologically interlocked material based on tetrahedron unit elements is investigated experimentally. Manufacturing with aid of a robotically controlled end‐effector is demonstrated, and mechanical properties are determined for a plate configuration. A conceptual mechanical model for failure of topologically interlocked materials is developed and used to interpret the experimental results.

It is demonstrated that remanufacturing of the topologically interlocked material is possible with only a limited loss of material performance. The proposed model predicts trends in agreement with the experimental findings.

While the model predictions are qualitatively in agreement with experiments, more detailed finite element models are needed to predict the material performance accurately. Experiments were conducted on a model material obtained from a 3D printer and should be verified on other solids.

The authors demonstrate that damage containment together with the absence of binders or adhesives enables reuse through remanufacturing without loss of structural integrity.

Topologically interlocked materials emerge as attractive materials for sustainable engineering once their material performance are weighted with an environmental impact factor.

Remanufacturing experiments on a novel class of materials were conducted and a new model for the characterization of the structural integrity of topologically interlocked materials is proposed and successfully evaluated against experiments in at least qualitative form.

Based on the random aggregate model of recycled aggregate concrete (RAC), this paper aims to focus on the effect of loading rate on the failure pattern and the macroscopic mechanical properties.

RAC is regarded as a five-phase inhomogeneous composite material at the mesoscopic level. The number and position of the aggregates are modeled by the Walraven formula and Monte–Carlo stochastic method, respectively. The RAC specimen is divided by the finite-element mesh to establish the dynamic base force element model. In this model, the element mechanical parameters of each material phase satisfy Weibull distribution. To simulate and analyze the dynamic mechanical behavior of RAC under axial tension, flexural tension and shear tension, the dynamic tensile modes of the double-notched specimens, the simply supported beam and the L specimens are modeled, respectively. In addition, the different concrete samples are numerically investigated under different loading rates.

The failure strength and failure pattern of RAC have strong rate-dependent characteristics because of the inhomogeneity and the inertial effect of the material.

The dynamic base force element method has been successfully applied to the study of recycled concrete.

Mechanical stress can heavily affect the magnetic behaviour law in ferromagnetic materials. This paper, aims to take into account the effect of mechanical stress into a hystreresis model. This model is implemented in a finite element analysis code and tested in the case of a simple system.

A simple extension of the classical Preisach model is proposed, in which a function linked to the Preisach density is parameterized using the mechanical stress as a supplementary parameter. The methodology is based on experimental measurements for identifying the required function. As a first approach, a linear interpolation is used between the measurements in order to have a continuous evolution of the magneto‐mechanical behaviour. This model has been tested in the case of a steel sheet in which width is not constant in order to obtain a non‐uniform distribution of stress and magnetic flux density.

The model can predict the magneto‐mechanical behaviour with a good accuracy in the case of tensile stress. Implementation of the model in finite element analysis has shown that the model can predict the behaviour of steel sheet subject to a non‐uniform stress distribution.

This paper shows that a classical hysteresis model can be extended to take into account the magneto‐mechanical behaviour. This is useful for the design of electrical machines which are subject to non‐negligible mechanical stress.