Force-deformation Curves Research Articles

Fracture performance study on Q460D steel and ER55-G welds after high temperature

Uniaxial tensile tests were conducted on smooth round bar specimens made of Q460D high-strength steel base metal and ER55-G welds after a high temperature of 900 °C and natural cooling. Counterpart specimens at room temperature were also examined for comparison. The basic mechanical properties of each specimen were obtained, enabling quantification of the true stress-plastic strain curve of the material required for finite element analysis (FEA) in ABAQUS. The notched round bar specimens were heated up to high temperature of 900 °C, and then naturally cooled to room temperature. Uniaxial tensile tests were carried out on the notched round bar specimens. By combining test results with ABAQUS FEA and scanning electron microscope tests, the void growth model (VGM) parameters of Q460D high-strength steel and ER55-G welds after high temperature of 900 °C and natural cooling were calibrated. Finally, the calibrated VGM model was adopted as a fracture criterion in the ABAQUS subroutine VUMAT to simulate the uniaxial tensile tests on notched round bar specimens of Q460D steel base metal and ER55-G welds after high temperature of 900 °C and natural cooling. It is indicated that in most cases, the post-fracture path and the whole force-deformation curve can be simulated through the FEA with subroutine VUMAT with reasonable accuracy.

EFFECT OF MOISTURE CONTENTS AND COMPRESSION AXES ON SOME PHYSICAL AND MECHANICAL PROPERTIES OF DIOCLEA REFLEXA SEED

Interest in unconventional seeds such as Dioclea reflexa is growing in the tropical regions, with the potential for utilisation as food or industrial materials. Researchers confirmed that Dioclea reflexa seed has the potential for clinical use, use as a food source, and as industrial raw material. This research studies the effect of moisture content on the physical properties of Dioclea reflexa seed and the effect of moisture content and compression axes its mechanical properties. Standards methods were used to determine the physical properties, while the mechanical properties were derived from force-deformation curves for the moisture content range 4.8 to 12.1% (wet basis). The mean values of the seed’s length increased by 3.55% (from 31.01 mm), the width increased by 4.13% (from 26.64 mm), and the thickness decreased by 2.48% (from 21.75 mm). The geometric mean diameter increased by 1.68%, surface area increased by 3.68%, sphericity decreased by 1.54% and individual seed mass increased by 10.46%. The physical properties exhibit linear relationships with moisture content. Rupture force increased by 75% (from 0.80 kN) for loading along the major axis; by 84% (from 0.72 kN) for the intermediate axis; and by 41% (from 0.78 kN) for the minor axis. Rupture energy increased from 0.18 J to 1.25 J for compression along the major axis, from 0.087 J to 0.43 J for the intermediate axis, and from 0.080 J to 0.18 J for the minor axis. The mechanical properties were found to be moisture content and loading orientation-dependent. Reducing moisture content reduced both the force and the energy required to rupture the seeds. The data generated will be useful in the design of processing machinery and storage facilities for the seeds.

Compressive-Tensile Mechanics and Energy Consumptions of a Cementitious Composite with High Utilization of Steel Slag

In response to the National Development and Reform Commission's “Guiding Opinions on Comprehensive Utilization of Large Solid Wastes during the Fourteenth Five Year Plan”, further expand the use of steel slag as concrete admixture in construction projects and other fields, and gradually improve the comprehensive utilization ratio, a cementitious composite with high utilization of steel slag (CHS) was developed, which is with the cement replaced by high-content super-fine steel slag powder (SSP) (replacement ratio υ ≥ 30%) as the cementitious materials, steel slag sand (SS) as the only aggregate and environmentally basalt fiber (BF) for toughening. It improves the utilization percentage of steel slag (SSP and SS) and reduces the consumption of natural resources such as cement and natural sand. Use BF to achieve better strength and toughness. In order to better understand the performance of CHS and make it better used in the engineering field. Study the influence of each component on the strength and energy consumption of compression and splitting tension, and strive to find the optimal proportion and lay the theoretical foundation for its application. Through the tests, the effects of high replacement ratio υ (30%–50%), low binder-aggregate ratio γ (0.31–0.44), and BF content ρv (0%–2%) on the aspects of peak strength, force-deformation curve and energy consumption were analyzed. The results show that the standard curing fck and ft,s can reach 40 MPa and 5 MPa respectively. With the increase of υ, the maximum axial compressive strength fck and splitting tensile strength ft,s decreased insignificantly. The γ has an important influence on fck and ft,s. When it increases from 0.31 to 0.44, fck increases linearly by 63.1% to 40.4 MPa, while ft,s increases by 52.8% to 5.18 MPa. As ρv increases, fck and ft,s show a trend of first increasing and then decreasing. ρv exerts a significant impact on the descending segments of stress-strain response curves of the compression which expressed as bilinear and trilinear models with different ρv after normalization. The energy consumptions of peak, total, and residual (Epeak, Edisp, Eres) show a slight downward trend with the increase of υ, a significantly upward trend with the increase of γ. With the increase of γv, and Edisp increase first and then tend to be flat, while Eres always increases and the percentages of Eres/Edisp in the compressive test increase from 22.6% to 38.5%, reflecting the improvement of the compressive toughness of BF.

Finite element based study on aerostatic post-buckling and multi-stability of long-span bridges

Aerostatic instability is one of two vital instabilities of wind resistance design for long-span bridges. Traditionally, the aerostatic instability considering aerodynamic and structural nonlinearity is evaluated through finite element methods employing the Newton-Raphson algorithm. However, the Newton-Raphson algorithm cannot track the structural equilibrium path after the first critical wind speeds (zero stiffness point) and the potential post-buckling multi-stability. This study proposes to use the arc-length method to calculate the aerostatic structural deformation for increasing wind speeds iteratively. Arc-length can track the equilibrium force-deformation curve even after the initial critical wind speeds. This study finds out that when the pitch moment curve of the bridge deck has a” turning point” at a large angle of attack, there is possibly more than one equilibrium point (multi-stability) for the same wind speeds. Correspondingly, the bridge deck deformation shape and cable and hangers’ internal force along span direction change dramatically at the same wind speed due to aerostatic multi-stability. In the last part of this study, the bridge structure under a turbulent wind field can buckle at a lower wind speed than a smooth wind field because the material yields are caused by large instantaneous deformation.

Stabilise and symmetrise the deformation of buckling metamaterial for tunable vibration bandgaps

Abstract Mechanical metamaterials have attracted extensive attention. This paper reports a metamaterial with tunable elastic wave bandgaps based on bistable buckling structure. First, we find that deformation of two symmetric buckling shells is intrinsically asymmetric, which blocks the realisation of robust tunability. Based on an analytical model, we clarify that the mechanisms for this intrinsic asymmetricity are the bifurcations on force–deformation curves. Then we propose a superposition method of buckling shells, which can realise the symmetric deformation for robust tunable stiffness. Using this variable-stiffness oscillator, we design a metamaterial sandwich beam, and numerically and experimentally demonstrate its tunable bandgap for vibration suppression. This paper presents the unusual deformation process of buckling elements widely used for constructing metamaterials, and provides a robust way to realise metamaterials with tunable vibration bandgaps.

Application of Uniaxial Compression Curve Fractal Dimension in the Identification of Cañihua (Chenopodium Pallidicaule Aellen) Grain Cultivars

HIGHLIGHTS Grains of three cañihua cultivars were identified through the determination of fractal dimension of its force?deformation curves. A special test cell device was developed to mechanically assess small grains during compression tests. Cañihua cultivars form separate groups when results of fractal dimension of their force?deformation curves, force of rupture, and fracture force are analyzed with PCA. ABSTRACT.Cañihua is an ancient crop of the Andean regions in South America. High genetic diversity of this crop can be found around Lake Titicaca. Cañihua grain is an important source of food for the people in this region because of its high protein and amino acid contents. Currently, there are three known cultivars and more than a hundred accessions of cañihua. Most of the grains from these cultivars and accessions have the same shape and color, making their identification difficult. This work sought to estimate the fractal dimension of force–deformation curves obtained during individual cañihua grain compression tests through the box-counting method (BCM) and the Higuchi fractal dimension (HFD) to show the possibility of differentiating and recognizing cañihua cultivars by taking into consideration the influence of their mechanical properties and chemical composition. Using BCM for the fractal dimension of the force-strain curves allowed us to differentiate the three cultivars from each other, and with HFD, it was possible to observe the difference between accessions and cultivars. Finally, by using the BCM and HFD results, together with mechanical properties such as the bioyield and rupture points and the energy required to reach them, the three cañihua cultivars could be differentiated from the accessions through multivariate PCA. The findings of this work could be applied to distinguish or identify cultivars of different crop grains. Keywords: Cañihua cultivars and accessions, Fractal dimension, Force–deformation curves, PCA.

A method to assess the hygro-mechanical behaviour of original panel paintings, through in situ non-invasive continuous monitoring, to improve their conservation: a long-term study on the Mona Lisa

• Non-invasive methods and equipment to measure and monitor panel painting's behaviour. • Technological analysis and state of conservation of the Mona Lisa ’s wooden panel. • Studying mechanical properties and conditions of an artwork painted on wood. • Monitoring mechanical response of panel paintings to environmental fluctuations. • Collecting data to feed and reliably calibrate numerical models. This paper describes an innovative method, and related equipment, developed by the authors to monitor non-invasively historic panel paintings under museum display conditions. This method permits in-depth knowledge about such artworks, allowing us to understand their reactions to climatic variations, and provides objective data on which conservation decisions can be confidently based, since the data are directly obtained from the individual artwork. Since 2004, following the invitation from the Louvre Museum and the C2RMF (National Centre for Research and Restoration of French Museums), the wooden panel on which Leonardo da Vinci painted his Mona Lisa has been studied by an international research team of wood technologists and engineers, including researchers from French and Italian universities and related scientific institutions (Montpellier, Clermont Auvergne, Poitiers, Florence), to understand its mechanical, hygroscopic and shape characteristics and behaviour, to evaluate its present state, and to provide suggestions for optimizing its conservation conditions. Non-invasive methods and equipment were therefore devised and implemented to measure (during the annual opening day of its display case) and automatically monitor (during the time the display case remains closed) both the deformations that the panel undergoes (mainly produced by the inevitable small climatic fluctuations within the case) and the constraining forces acting on the panel itself. The method and the related equipment, improved over the years, are based on miniature load cells and displacement transducers, whose outputs are automatically logged at desired time intervals, typically ranging between 30 min for monitoring during the whole year, and a few seconds for manual measurements, calibrations, and other selected events; the stored data can be downloaded both through a cable connection and wirelessly, by means of a specially developed connection apparatus. The panel is confined in a climate-controlled display case, which typically is opened only for a few hours once a year. Additionally, close restrictions must be respected, including absolute non-invasiveness, non-interference with the enjoyment of the artwork by the public, and compliance with strict procedures for safe and secure conservation. The implementation of this method has provided significant information about the actual behaviour of the panel during the whole year. Comparing several annual force-deformation curves, their good linearity suggests that no unacceptable stress or deformation has taken place in it, showing that the climatic conditions (air temperature and relative humidity) maintained in the display case can be considered favourable to the conservation of the artwork. Moreover, based on the collected data, reliable Finite Element Method (FEM) models are being developed and calibrated, with the aim of describing the mechanical behaviour of the panel and virtually evaluating the risk of damage (including the propagation of an ancient crack) deriving from external conditions or actions to which it would be unthinkable to submit the original historic artwork.

Low-velocity single and repeated impact behavior of 3D printed honeycomb cellular panels

Abstract In this study, low velocity single and repeated impact behaviors of 3D printed curved honeycomb cellular panels that can be used for impact protection are investigated. The energy absorbing capacity of the 3D printed honeycomb curved panels is predicted by evaluating the results. In addition, the changes in the fundamental free vibration frequencies of the panels subjected to impact are examined to have an idea about the presence of the damage. The effect of curvature on the damage mechanisms of 3D printed honeycomb panels is studied by examining the contact force–deformation curves, energy profile diagrams, and SEM images. The experimental results indicate that the radius of curvature of the cellular panels highly affects the impact and free vibration behavior, and the change in the natural frequency due to the impact damage is more considerable for ABS than PLA.

Characterization of various modified asphalts using force ductility test with “8“ shaped mold and straight mold

To explore a suitable mold for the force ductility test and propose a new index to better characterize low-temperature properties of modified asphalt, plain asphalt (PG 58–16, PG 52–22), styrene–butadienestyrene (SBS) modified asphalt (4.2 %, 7.5 %), low-density polyethylene (LDPE) modified asphalt (3 %, 8 %) and crumb rubber modified asphalt (20 %) were characterized using the force ductility test with “8” shaped mold and straight mold, respectively. The difference between their failure types and force–deformation curve evolution stages was analyzed. True stress was calculated to highlight the toughening effect of elastic polymer modifiers. Results demonstrate that three failure types (brittle fracture, flow failure, and ductile fracture) and three deformation stages (elastic, yield, and slender neck stage) can be observed and summarized for the force ductility test. The ductile failure and slender neck deformation stage is only observed for elastic-modified asphalts, which highlights the elastic polymer’s toughening effect. “8” shaped mold appears to be a better choice than straight mold due to its better discrimination ability and less variability. The calculated true fracture stress has a very strong correlation (R2 > 0.95) with deformation energy, which shows a good discrimination between modified asphalts.

Demonstration of Hybrid Effect in Single Fiber Pull-Out Tests for Glass/Cellulose-Reinforced Polypropylene with Different Fiber-Matrix Adhesions.

In hybrid fiber reinforcement, the combination of glass and regenerated cellulose fibers is a promising combination because the different properties of the fibers can be combined. The properties of the regenerated cellulose fiber in combination with the absorption of energy by fiber pull-outs can thus significantly increase the toughness of the composite in the event of failure, while the glass fiber significantly increases the stiffness and strength due to its properties. In this study, the interaction of the two fiber types in a composite is demonstrated by fiber pull-outs. For this purpose, the fibers are embedded in a PP matrix and simultaneously pulled out. Different bondings of the fiber by, e.g., coupling agent and/or a pretreatment of the regenerated cellulose fiber, were also investigated. The results show that each type of fiber has a characteristic force–deformation curve, and the hybrid reinforcement is a combination of both curves. The use of a coupling agent leads to an increase in the interfacial shear stress from 4.5 to 7.5 MPa. A treatment of the regenerated cellulose fiber by UV light further increases the interfacial shear stress to 11 MPa.

Characterizing Mechanical Properties of Primary Cell Wall in Living Plant Organs Using Atomic Force Microscopy

The mechanical properties of the primary cell walls determine the direction and rate of plant cell growth and, therefore, the future size and shape of the plant. Many sophisticated techniques have been developed to measure these properties; however, atomic force microscopy (AFM) remains the most convenient for studying cell wall elasticity at the cellular level. One of the most important limitations of this technique has been that only superficial or isolated living cells can be studied. Here, the use of atomic force microscopy to investigate the mechanical properties of primary cell walls belonging to the internal tissues of a plant body is presented. This protocol describes measurements of the apparent Young's modulus of cell walls in roots, but the method can also be applied to other plant organs. The measurements are performed on vibratome-derived sections of plant material in a liquid cell, which allows (i) avoiding the use of plasmolyzing solutions or sample impregnation with wax or resin, (ii) making the experiments fast, and (iii) preventing dehydration of the sample. Both anticlinal and periclinal cell walls can be studied, depending on how the specimen was sectioned. Differences in the mechanical properties of different tissues can be investigated in a single section. The protocol describes the principles of study planning, issues with specimen preparation and measurements, as well as the method of selecting force-deformation curves to avoid the influence of topography on the obtained values of elastic modulus. The method is not limited by sample size but is sensitive to cell size (i.e., cells with a large lumen are difficult to examine).

Comparative multi-parameters approach to dissect texture subcomponents of highbush blueberry cultivars at harvest and postharvest

Fruit texture and firmness are important cues of blueberry quality for the fresh market. These attributes contribute to consumer acceptance, resistance to bruising during harvesting and transportation, and shelf-life. Thus, fruit firmness and texture are major priorities for blueberry breeders, producers and distributors. In this study, the discriminative power of texture analysis was examined using penetration tests with different probes and double compression for texture profile analysis (TPA). Mechanical parameters taken from the force deformation curves used to dissect texture subcomponents in blueberries that are associated with specific tissue layers. Principal component analysis (PCA) allows to filter and identify mechanical parameters that significantly discern the most variation amongst 24 blueberry genotypes and showed that texture in this crop is multi-trait and cultivar-dependent. Texture analysis was used also on blueberries stored over six weeks to identify mechanical parameters that could be used as predictors for long shelf life. Additionally, the mechanical parameters were correlated with dynamometer data to determine the utility and accuracy of a simple handheld device to measure fruit firmness in blueberries. This study provides a framework for the identification and characterization of the subcomponents of texture in highbush blueberry.

Full-range behaviour of T-stubs with various yield line patterns

This paper investigates the full-range behaviour of T-stubs through both experimental and numerical approaches. Nineteen T-stub specimens with six different yield line patterns were loaded to the complete failure. Most of the specimens failed due to rupture of the bolts after significant yielding of the flanges. A new method is proposed to determine the points of initial yielding and ultimate state on a nonlinear full-range force-deformation curve, and by using this method the mechanical properties of the specimens were obtained. Benchmarked against the experimental results, the validities of three T-stub analytical models are examined. None of the models is proven to be able to accurately capture the full-range behaviour of the T-stubs, with the Jaspart model showing a comparatively better accuracy. Finite-element models capable of reproducing the experimental phenomena are developed and are extended to cover all possible failure modes. It is observed that the ratio between the resistances of Failure modes 1 and 3, β, can be used to predict the behaviour and failure mode of the T-stub. The actual β-value dividing Failure modes 1 and 2 is equal to the theoretical value, but that dividing Failure modes 2 and 3 is much smaller than the theoretical value of 2.0. Taking the resistance, stiffness and ductility into comprehensive consideration, it is suggested that a T-stub be designed with a β-value around 0.67 to achieve a balanced design with a good overall performance.

Novel Distributed Loading Technique Using Multimaterial, Long-Segment Spinal Constructs to Prevent Proximal Junctional Pathology in Adult Spinal Deformity Correction—Operative Technique and Radiographic Findings

Proximal junctional kyphosis (PJK) and proximal junction failure are common and costly complications after long-segment adult spinal deformity (ASD) correction. Although much research has focused on the concept of "softening the landing" to prevent proximal junction pathologies, long-segment constructs largely deviate from the force-deformation curve of the physiologic spine. Our novel distributed loading technique for ASD correction is described using multimaterial, long-segment constructs to create a biomechanically sound, yet physiologic, decremental stiffness toward the rostral end. Operative steps detail the custom-designed constructs of dual-headed pedicle screws and varied rod diameters and materials (cobalt chromium or titanium) for an initial 20 patients (mean 66.6 ± 4.8 years). Standing scoliosis films were obtained preoperatively and at regular intervals postoperatively to assess for PJK. No patient had evidence of PJK or proximal junction failure at latest radiographic follow-up (mean 17.9 months, range 13-25 months). Radiographic findings for sagittal vertical axis averaged 11.2 ± 5.6 cm preoperatively and 3.6 ± 2.3 cm postoperatively. Compared with preoperative parameters, postoperative reductions in pelvic incidence-lumbar lordosis mismatch averaged 28.7 ± 12.9 degrees, and sagittal vertical axis averaged 7.6 ± 5.2 cm while PJA was essentially unchanged. Preliminary results suggest that the distributed loading technique is promising for prevention of PJK with stiffness gradients that mimic the force-deformation curve of the physiologic posterior tension band. Our technique may optimize the degree of stress at the proximal junction without overwhelming the anterior column bony while remodeling and mature arthrodesis takes place.

Post-fire performance of steel reinforced concrete columns with different steel sections

This study investigates the post-fire performance of steel reinforced concrete composite (SRC) columns used in building construction using experimental compression tests. Four conventional steel sections as I-shaped, Cross, Box, and Plus were considered as the steel core. For fire loading, all fabricated columns were subjected to five target temperatures, including 25°, 250°, 500°, 700°, and 900°C, and then the cooling phase of the columns was done under natural conditions. Then using pressure jacks, the compressive behavior including strength and axial deformation of each of them was measured, and force-deformation curves were plotted and investigated for each SRC column. The results of these tests showed that the compressive strength and the elasticity modulus of the columns decrease at higher temperatures. Also, the effect of the steel core was examined on the compressive strength. Among the tested sections, SRC columns with the Box-steel core showed a more recovery in its compressive strength and elasticity modulus, and hence, its performance was better than SRC columns with the other steel cores. Moreover, SRC columns with the Plus-steel core indicated the weakest compressive strength and elasticity modulus. Finally, some equations were proposed for the prediction of the compressive strength and elasticity modulus of SRC columns at different temperatures by applying gene expression programming (GEP modeling) to the results.

A Computational Study of the Shear Behavior of Reinforced Concrete Beams Affected from Alkali-Silica Reactivity Damage.

In this study, an investigation of the shear behavior of full-scale reinforced concrete (RC) beams affected from alkali–silica reactivity damage is presented. A detailed finite element model (FEM) was developed and validated with data obtained from the experiments using several metrics, including a force–deformation curve, rebar strains, and crack maps and width. The validated FEM was used in a parametric study to investigate the potential impact of alkali–silica reactivity (ASR) degradation on the shear capacity of the beam. Degradations of concrete mechanical properties were correlated with ASR expansion using material test data and implemented in the FEM for different expansions. The finite element (FE) analysis provided a better understanding of the failure mechanism of ASR-affected RC beam and degradation in the capacity as a function of the ASR expansion. The parametric study using the FEM showed 6%, 19%, and 25% reduction in the shear capacity of the beam, respectively, affected from 0.2%, 0.4%, and 0.6% of ASR-induced expansion.

Investigation on low-cost friction-based isolation systems for masonry building structures: Experimental and numerical studies

Masonry structures do not exhibit adequate seismic performance but they are still the most commonly constructed buildings across the globe. To enhance their seismic capacity and to protect them from the damaging effects of earthquakes in seismic active regions, an innovative low-cost friction-based seismic isolation system is developed in this study. The proposed isolation system, installed between the foundation and superstructure is made up of a 50 mm thick isolation layer material having low lateral stiffness, which is sandwiched between two 4 mm thick Teflon sheets and is further reinforced by vertical rebars. To establish the mechanical properties of the isolation system, experimental trials were performed using weak mortar, asphalt cushion, steel balls enclosed in mortar, coarse sand mortar, and rubberized mortar as an isolation layer material, and the proposed isolation system is installed between two hollow concrete blocks for testing purpose. Cyclic load tests were performed on the specimens and force-deformation curves were achieved. Two numerical models, one with a fixed base and another with the proposed isolator were developed using finite element analysis approach and analyzed against five different ground motions input. The isolation layer material used in the numerical model was selected based on friction coefficient and cyclic loading tests. In case of low seismic excitation, the isolation system does not activate to ensure structural integrity, however, when the lateral forces exceed the permissible limit then the isolation system permit deformation in both horizontal directions to dissipate seismic energy through friction while the vertical reinforcement ensure the re-centering mechanism of the structure. It is observed that the proposed isolation system considerably reduces the transmission of earthquake energy to the superstructure over a variety of ground motions. Depending upon the type of ground motion, an overall 45% − 56% reduction was observed in the absolute acceleration response of the top roof level of the isolated structure.

Understanding the mechanical performance of raw and cooked potato cells

The micromechanics of individual potato cells comprising of cell wall and embedded native or gelatinised starch were explored. Micromanipulation can be used to compare cells of distinct strengths and study (bio)mechanical issues related to industrial processing (e.g. heat treatment). Two commercial types of potato, ‘baking’ and ‘Maris Piper’ were selected to conduct microcompression experiments. Cells isolated from ‘Maris Piper’ raw tubers appeared to be more resistant to deformation than the respective ones from the ‘baking’ cultivar. Cooked cells suffered a decrease in their turgidity which resulted in clusters of observed behaviours, with force–deformation curves showing a single or multiple bursting events. This study provides fundamental work and an insight on the behaviour of potato cells via an exploratory investigation of how different elements of the potato tissue can be measured. The results obtained can be used to relate cellular biology to mechanical properties and could also pave the way to understanding other starch-containing cells (e.g. pea, lentils, wheat).

Potentiality of MWCNT fillers on the lateral crashworthiness behaviour of polymer composite cylindrical tubes under quasi-static loading

In recent years, light-weight nano composite materials have been progressively employed in the aviation, defense, naval and automotive manufacturing applications owing to their outstanding mechanical and crashworthiness characteristics. In this regard, nano composite cylindrical tubes could be significantly utilized as energy absorbing elements for dissipating the impact energy during vehicle collisions. The present research study aimed to examine the lateral crashworthiness response of Multi-Walled Carbon Nano Tubes (MWCNT) filled epoxy composite (basalt fabric and glass fabric) tubes of three different inner diameters using quasi-static crushing experiments. Crushing profiles and crush force–deformation curves of all the recommended typical tube samples are computed and discussed elaborately. The results obtained revealed that better crashworthiness characteristics of MWCNT reinforced epoxy composite tubes with a larger diameter, were owing to more promising crushing modes occurring during lateral compression. It is also found that the lateral crashworthiness response of the MWCNT filled glass fabric epoxy composite tubes was marginally superior to that of the MWCNT filled basalt fabric epoxy composite tubes. However, both the recommended composite cylindrical tubes with nano-fillers might be employed as energy dissipating elements in modern vehicles.

Finite Element Simulations of Mechanical Behaviour of Endothelial Cells.

Biomechanical models based on the finite element method have already shown their potential in the simulation of the mechanical behaviour of cells. For instance, development of atherosclerosis is accelerated by damage of the endothelium, a monolayer of endothelial cells on the inner surface of arteries. Finite element models enable us to investigate mechanical factors not only at the level of the arterial wall but also at the level of individual cells. To achieve this, several finite element models of endothelial cells with different shapes are presented in this paper. Implementing the recently proposed bendotensegrity concept, these models consider the flexural behaviour of microtubules and incorporate also waviness of intermediate filaments. The suspended and adherent cell models are validated by comparison of their simulated force-deformation curves with experiments from the literature. The flat and dome cell models, mimicking natural cell shapes inside the endothelial layer, are then used to simulate their response in compression and shear which represent typical loads in a vascular wall. The models enable us to analyse the role of individual cytoskeletal components in the mechanical responses, as well as to quantify the nucleus deformation which is hypothesized to be the quantity decisive for mechanotransduction.