Improved model of powder blend compacting in a roll compactor

A new mathematical model of mineral fertilizer compacting using a roll compactor is developed. This model is based on the transition to the values of stress tensor components averaged over the cross-sectional area of the powder mixture flow. To define these stresses, equations of equilibrium of the elementary layer determined in the mixture by two planes perpendicular to the flow direction are composed. To obtain relatively simple analytical relations in the calculations, the hypothesis of a power-law dependence of hydrostatic pressure on mixture density, accepted in the framework of the Johansen model, was used. In order to take into account changes in the mechanical characteristics of the mixture (angle of internal friction, coefficient of external friction, transverse strain coefficient) while compacting, we approximated the known experimental dependencies of the corresponding characteristics on the density. The inter-particle cohesion parameter was taken to be proportional to the hydrostatic pressure. The model allows calculating the gap between the rolls surfaces for a given initial bulk density and the required flake density. With the known gap value, the distribution of the axial average stresses in the powder mixture, the normal and shear stresses on the rolls’ surfaces are determined. The results of the calculations of the rolls surface gap and the normal roll pressure diagram are compared with the experimental data given in the literature for the urea compacting process.

The effects of preloading on tensile properties of braided polyarylate fiber ropes

In the present work, the effects of preloading on the tensile properties of braided polyarylate fiber ropes were investigated experimentally. Four kinds of samples with different pitch lengths were tested with designed preload levels. The deformation responses of the ropes were captured using digital image correlation (DIC) and micro-computed tomography (micro-CT). It is shown that the nonlinearity in the mechanical behavior of the ropes can be almost eliminated post-preloading with one cyclic loading, and the transverse strains are much greater than the longitudinal strains due to the compaction of rope structure because of the spiral interlaced path of braid yarns. The rope with shorter pitch length (larger braid angle) has larger longitudinal strain and smaller transverse strain due to the higher yarn crimp rate and tighter yarns, respectively. The preload level is the most important parameter for preloading. The chord modulus of the ropes reached an optimum level at the preload level of 40% break load, and the tensile strength can be increased by 15% at the preload level of 50% break load. Moreover, the stability of the tensile properties could be accelerated at the higher preload level. Consequently, preloading is vital to improve the tensile properties of braided polyarylate fiber ropes, with a preload level at least of 40% break load and 10 cyclic loadings.

Mathematical modeling of auxetic systems: bridging the gap between analytical models and observation

The Poisson’s ratio, a property which quantifies the changes in thickness when a material is stretched and compressed, can be determined as the negative of the transverse strain over the applied strain. In the scientific literature, there are various ways how strain may be defined and the actual definition used could result in a different Poisson’s ratio being computed. This paper will look in more detail at this by comparing the more commonly used forms of strain and the Poisson’s ratio that is computable from them. More specifically, an attempt is made to assess through examples on the usefulness of the various formulations to properly describe what can actually be observed, thus providing a clearer picture of which form of Poisson’s ratio should be used in analytical modelling.

Mechanical Analysis and Experimental Studies of the Transverse Strain in Wrinkled Metallic Thin Films

The wrinkling structures, which can greatly improve the stretchability of the metallic thin films, have been widely used in the preparation of stretchable devices. However, the artificial wrinkling structures are often accompanied by the generation of microcracks, which seriously affect the performance of the devices. In this work, by establishing the corresponding model, the transverse strain of the longitudinally prestrained continuous film and the strip film is mechanically analyzed, which is verified by experimental results; for the strain of blank substrate, the error of the model was about 3.7%. It is difficult to avoid the generation of microcracks with continuous films, but strip films can avoid the generation of microcracks to a certain extent. The experimental results illustrate the various factors affecting the generation of microcracks. The transverse strain of the film is proportional to the substrate’s Young’s modulus, Poisson’s ratio, thickness, and prestrain and is basically inversely proportional to the strip film’s Young’s modulus, thickness, and strip interval. Our results provide deeper knowledge for choosing proper metallic materials to fabricate stretchable wrinkled devices.

Eccentric compression behavior of long poplar columns externally reinforced by BFRP

The column, which is the vertical main structural part of the building, bears the force transmitted from the upper beam and slab and is a crucial part of the structure. In this study, the columns with a rectangular section cut from poplar were reinforced by basalt fiber-reinforced polymer (BFRP) strips with four different reinforced configurations. The mechanical behaviors of the specimens were also investigated under different eccentricities. Experimental results are presented as follows: for the wooden columns under axial compression, the wooden column BFRP with one layer spaced apart, two layers spaced apart, one layer fully filled, and two layers fully reinforced demonstrated increased bearing capacities of 3.13%, 30.00%, 40.63%, and 65.00%, respectively; the longitudinal strain increased by 7.54%, 19.65%, 22.06%, and 30.69%, and the lateral strain decreased by 26.53%, 29.80%, 41.30%, and 66.64%, respectively. Meanwhile, for the wooden column subjected to eccentric compression, the bearing capacities of the aforementioned wooden column BFRP configurations increased by 8.70%, 19.56%, 23.91%, and 30.43%; the longitudinal strain of the wooden column increased by 25.41%, 35.20%, 39.52%, and 41.85%; and the transverse strain increased by 130.77%, 166.77%, 192.57%, and 230.86%. In addition, the finite element model was used to simulate the eccentric compression behavior of the specimen. However, the ultimate bearing capacity and deflection of the analyzed column were higher than the test value. This finding was due to the completely ideal state of poplar in Finite Element Analysis (FEA) modeling without the influence of some initial defects, such as knots. These values can roughly be used as a reference for experimental results for the repair and reinforcement of poplar structures in Xinjiang.

Development of High Dielectric Electrostrictive PVDF Terpolymer Blends for Enhanced Electromechanical Properties

Electroactive polymers with high dielectric constants and low moduli can offer fast responses and large electromechanical strain under a relatively low electric field with regard to theoretical driving forces of electrostriction and electrostatic force. However, the conventional electroactive polymers, including silicone rubbers and acrylic polymers, have shown low dielectric constants (ca. < 4) because of their intrinsic limitation, although they have lower moduli (ca. < 1 MPa) than inorganics. To this end, we proposed the high dielectric PVDF terpolymer blends (PVTC-PTM) including poly(vinylidene fluoride-trifluoroethylene-chlorofluoro-ethylene) (P(VDF-TrFE-CFE), PVTC) as a matrix and micelle structured poly(3-hexylthiophene)-b-poly(methyl methacrylate) (P3HT-b-PMMA, PTM) as a conducting filler. The dielectric constant of PVTC-PTM dramatically increased up to 116.8 at 100 Hz despite adding only 2 wt% of the polymer-type filler (PTM). The compatibility and crystalline properties of the PVTC-PTM blends were examined by microscopic, thermal, and X-ray studies. The PVTC-PTM showed more compatible blends than those of the P3HT homopolymer filler (PT) and led to higher crystallinity and smaller crystal grain size relative to those of neat PVTC and PVTC with the PT filler (PVTC-PT). Those by the PVTC-PTM blends can beneficially affect the high-performance electromechanical properties compared to those by the neat PVTC and the PVTC-PT blend. The electromechanical strain of the PVTC-PTM with 2 wt% PTM (PVTC-PTM2) showed ca. 2-fold enhancement (0.44% transverse strain at 30 Vpp μm−1) relative to that of PVTC. We found that the more significant electromechanical performance of the PVTC-PTM blend than the PVTC was predominantly due to the electrostrictive force rather than electrostatic force. We believe that the acquired PVTC-PTM blends are great candidates to achieve the high-performance electromechanical strain and take all benefits derived from the all-organic system, including high electrical breakdown strength, processibility, dielectrics, and large strain, which are largely different from the organic–inorganic hybrid nanocomposite systems.

COMPARATIVE ANALYSIS OF RESULTS OF NUMERICAL MODELING OF MECHANICAL BEHAVIOR OF GRAPHENE AND SILICENE IN THE FRAMES OF COMMON HARMONIC FIELD

В статье представлены результаты применения модели общего гармонического поля для численного моделирования механических свойств близких по геометрической форме образцов наноструктур графена и силицена. Проведён расчёт коэффициентов жёсткости элементов для этой модели на основе жёсткостей пары базовых через собственные частоты колебаний трёхузловых фрагментов. Приведены зависимости упругих модулей от линейных размеров. В обоих случаях наблюдается рост модуля продольной упругости с выходом на асимптоту при увеличении длины образца и очень слабая зависимость от его ширины. Коэффициент поперечной деформации уменьшается с ростом ширины. Увеличение длины даёт у графена рост данного показателя, а у силицена - его снижение. The article presents the results of application of the general harmonic field model for numerical modeling of mechanical properties of samples of graphene and silicene nanostructures similar in geometric form. A calculation of the stiffness coefficients of the elements for this model was made based on the stiffness of a pair of basic ones through the natural frequencies of oscillations of three-node fragments. Dependencies of elastic modules on linear dimensions for examined samples are given. In both cases, there is an increase in the modulus of longitudinal elasticity with an increase in asymptote with an increase in the length of the sample and a very weak dependence on its width. The coefficient of transverse strain decreases as the width increases. Increasing the length gives graphene an increase in this indicator, and in silicene - its decrease.

Left ventricular segmental strain and the prediction of cancer therapy-related cardiac dysfunction

Aims We aimed to determine the early changes and predictive value of left ventricular (LV) segmental strain measures in women with breast cancer receiving doxorubicin. Methods and results In a cohort of 237 women with breast cancer receiving doxorubicin with or without trastuzumab, 1151 echocardiograms were prospectively acquired over a median (Q1–Q3) of 7 (2–24) months. LV ejection fraction (LVEF) and 36 segmental strain measures were core lab quantified. A supervised machine learning (ML) model was then developed using random forest regression to identify segmental strain measures predictive of nadir LVEF post-doxorubicin completion. Cancer therapy-related cardiac dysfunction (CTRCD) was defined as a ≥10% absolute LVEF decline pre-treatment to a value &lt;50%. Median (Q1–Q3) baseline age was 48 (41–57) years. Thirty-five women developed CTRCD, and eight of these developed symptomatic heart failure. From pre-treatment to doxorubicin completion, longitudinal strain worsened across the basal and mid-LV segments but not in the apical segments; circumferential strain worsened primarily in the septum; radial strain worsened uniformly and transverse strain remained unchanged across all LV segments. In the ML model, anterolateral and inferoseptal circumferential strain were the most predictive features; longitudinal and transverse strain in the basal inferoseptal, anterior, basal anterolateral, and apical lateral segments were also top predictive features. The addition of predictive segmental strain measures to a model including age, cancer therapy regimen, hypertension, and LVEF increased the area under the curve (AUC) from 0.70 (95% confidence interval (CI) 0.60–0.80) to 0.87 (95% CI 0.81–0.92), ΔAUC = 0.18 (95% CI 0.08–0.27) for the prediction of CTRCD. Conclusion Our findings suggest that segmental strain measures can enhance cardiotoxicity risk prediction in women with breast cancer receiving doxorubicin.

Diagnostic accuracy of left ventricular diastolic transverse strain imaging by speckle tracking echocardiography for diagnosing chest pain in diabetic patients

Background Two-dimensional speckle tracking echocardiography (2D-STE) has been reported to be useful for the diagnosis of myocardial ischemia by detecting delayed relaxation (diastolic stunning) after an episode of angina. 2D-longitudinal strain is not specific besides ischemia such as diastolic dysfunction, and diabetes have been associated with abnormal longitudinal fibers. The aim is to evaluate the diagnostic accuracy of Left ventricular (LV) diastolic transverse strain imaging by STE to detect the presence of acute coronary syndrome (ACS) in diabetic patients with acute chest pain. Methods 385 consecutive patients with acute chest pain and without wall motion abnormality, who were admitted to an emergency department (ED) at 1 of 12 clinical sites in Japan, were enrolled and underwent 2D-STE at ED. Left ventricular (LV) transverse strain values at aortic valve closure (A) and one-third of diastole duration (B) were measured. The strain imaging diastolic index (SI-DI) was value was determined as: (A − B)/A × 100% to assess the LV diastolic strain imaging and was used to identify the regional LV delayed relaxation. All patients underwent coronary CT or coronary angiography to establish the diagnosis of ACS. Clinicians were blinded to the 2D-STE results. Results Out of 385 patients, 2D-STE analysis was possible in 365 patients (94%). 76 patients were diabetic (DM+), and 289 patients were non-diabetic (DM-). With assessment of coronary CT or coronary angiography, ACS was diagnosed in 125 patients (34%). 2D-STE was obtained at a mean of 5.3 hours after chest pain episode. Transverse SI-DI of ischemic segments were significantly lower than those of non-ischemic segments (p value &lt;0.001) in both diabetic and non-diabetic patients, and transverse SI-DI of both diabetic and non-diabetic patients demonstrated high area under curve (AUC) for detection of myocardial ischemia (Figure: RCA; right coronary artery, LAD; left anterior descending artery, LCX; left circumferencial artery). In diabetic patients, sensitivity, specificity, and negative predictive value for ACS of transverse SI-DI are 100%, 95%, 100% in RCA (a cut-off value of 36.2), and 86.4%, 95%, 93% in LAD (a cut-off value of 50.2), and 75%, 85%, 94% in LCX (a cut-off value of 52), respectively. Conclusion LV diastolic transverse strain imaging by 2D-STE at ED increase the sensitivity, specificity and accuracy to predict the presence of ACS in diabetic patients with chest pain, as well as non-diabetic patients. (UMIN000013859). Figure 1. Transverse Strain (SI-DI): AUC (95% CI) Funding Acknowledgement Type of funding source: None