Experimental Specimens Research Articles

Machine-learning networks to predict the ultimate axial load and displacement capacity of 3D printed concrete walls with different section geometries

This paper presents details on the machine learning (ML) models for predicting the ultimate axial load capacity and ultimate displacement capacity of 3D printed concrete (3DPC) walls. The large database required for training and testing procedures of ML models is generated using a validated finite element (FE) model, verified using experimental specimens from the literature. Then, a wide range of physical and mechanical properties is selected to form a large database of 3DPC walls. To this end, 61800 3DPC walls with five different cross-sections and with various geometries were analyzed. The ultimate axial load capacity and ultimate displacement capacity of each wall are determined using explicit dynamic analysis. In conclusion, ML algorithms provide accurate predictions with coefficient of determination values of 0.95 and above. It should be noted that the prediction of the maximum axial load capacities was better than that of the ultimate displacement capacities.

Effect of corrugated plate arrangements on the performance of steel shear wall frames

Nowadays, the use of corrugated steel shear walls with sinusoidal, triangular, and trapezoidal profiles, which are stiffened steel walls without stiffener, is recommended for delaying the premature occurrence of buckling in the plate. The arrangement of corrugated plates in the structural frame alters seismic parameters; therefore, this research focuses on various arrangements of inclined corrugated plates. For this purpose, experimental specimens are first validated under cyclic quasi-static loading using ABAQUS finite element software. Subsequently, the design of four different arrangements of inclined corrugated plates with three profiles of trapezoidal, sinusoidal, and triangular is conducted and compared with vertical and horizontal arrangements. Based on the results, the triangular waveform demonstrated better energy absorption, initial stiffness, and ultimate strength. Investigation of different plate thicknesses for triangularly corrugated shear walls, including 0.75, 1.25, and 1.75 mm, showed that increasing the wall thickness improved the seismic behavior. Additionally, Arrangement No. 1 (inclined arrangement) provided the highest energy absorption and ultimate strength; however, its behavior in the hysteresis curve was asymmetric. This issue has been addressed by implementing a double arrangement of plates.

Study on the Biological Drug Enterocol’s Effect on the Nile Tilapia Breeding

Background Nile tilapia (Oreochromis niloticus) is a promising fish species for fish farming development in the Republic of Kazakhstan. It exemplifies a balanced and fast-growing source of flesh for future food production. In this context, optimising breeding methods is crucial for a high flesh yield and a safe product. The study delves into the potential of the Enterocol drug in enhancing Nile tilapia breeding, focusing on assessing muscle state and blood parameters. Objects Two groups of fish were utilized, with 20 specimens in each group. One set was the control group, and the other was the experimental group. The single difference between the fish groups was the Enterocol consumption by the experimental specimens, which were given an E. coli 64G strain concentration of 108 CFU in mL and a 5% daily dose of fish body weight three times daily for two months. Methods Blood parameters were analysed to assess the health of the fish groups. Subsequently, classical pathological methods were employed, such as macroscopic and microscopic assessments of each group's fish material. A histological analysis was also performed to assess the condition of the muscles. Results Examining the experimental group's muscles revealed a significant average increase in fish mass and 6.74% total body weight growth. Moreover, the total thickness of the muscle layer decreased as villi height increased, indicating a clear fibre structure. Haematological analysis unveiled elevated levels of haemoglobin, erythrocytes, leucocytes, and total protein in the experimental fish group, indicating improved health. These findings underscore the potential of the Enterocol drug in enhancing fish health and productivity. Conclusion Based on the results, it can be concluded that using Enterocol in fish breeding plants can effectively enhance flesh quality and safety, providing a secure and reliable solution for the aquaculture industry.

The Possible Effect of Platelet Rich Plasma on Liver and Small intestine in Adult and Aged Male Rats. A Histological and Immunohistochemical Study

Abstract Introduction There is a general modest decline in the function of different organs in the body with aging. In the small intestine, there may be alterations in the intestinal morphology, as well as a decline in the absorption of fatty acids and sugars. The aging process decreases regenerative ability which significantly delays the restoration of liver function. Platelet-rich plasma (PRP) has recently attracted interest in many medical fields. PRP might has benefit effect on aged male rats. Aim of the Work This study aims to investigate the structural changes that might occur during normal aging and the possible effect of PRP intraperitoneal injection on adult and aged male albino rats. Materias and Methods Forty-two male albino rats were classified according to age into adult group and old aged groups. Adult male rats (300 -350 g), their age range between 6-8 months. Aged male rats (570-660 g), their age range between 12-24 months. They were divided randomly into four groups: Group I (Control adult): Included 14 rats that further subdivided into 2 equal subgroups: subgroup IA: untreated rats and subgroup Ib: rats were injected by sterile saline intraperitoneally (0.5 mL/kg by intraperitoneal injection 3 times/week). Group II (Control Aged): Included 14 rat that further subdivided into 2 similar subgroups as group I, Group III (Adult treated): Included 7 rats that received intraperitoneal injection of PRP (0.5 mL/kg by intraperitoneal injection 3 times/week), Group IV (Aged treated): Included 7 rats that received intraperitoneal injection of PRP as group III. Animals were kept under observation and the treated groups received intraperitoneal injections for 21 days. At the end of the experiment, Liver and small intestine specimens were processed for histological and immunohistochemical examination. Morphometric and statistical analysis was also done. Results Group II showed decrease in height of intestinal villi with disruption of their epithelium surface, increase spacing between enterocytes and abundant mononuclear cellular infiltration. Changes in the liver comprised nuclear and cytoplasmic changes that included an increase in nuclei number in hepatocytes with droplets fat infiltration. Treated Groups showed decreasing mononuclear cellular infiltration with decreasing collagen fibres and congested blood vessels. Conclusion Aging process enhanced the vulnerability to injury and inflammation in both the liver and small intestine. PRP had ameliorating effects on these changes.

A Study on the Evaluation of Thermal Insulation Performance of Cellulose-Based Silica Aerogel Composite Building Materials.

Buildings utilize both inorganic and organic insulation materials to conserve energy and prevent heat loss. However, while exhibiting excellent thermal insulation performance, organic insulation materials increase the risk of fire due to the emission of intense heat and toxic smoke in the event of a fire. Conversely, inorganic insulation materials are characterized by a lower thermal insulation performance, leading to an increase in the weight of the building with extensive use. Therefore, the necessity for research into new insulation materials that address the drawbacks of existing ones, including reducing weight, enhancing fire resistance, and improving thermal insulation performance, has been recognized. This study focuses on evaluating the enhancement of the thermal insulation performance using novel building materials compared to conventional ones. The research methodology involved the incorporation of porous aerogel powders into paper-based cellulose insulation to improve its insulating properties. Samples were prepared in standard 100 × 100 mm2 panel forms. Two control groups were utilized: a pure control group, where specimens were fabricated using 100% recycled cardboard for packaging, and a mixed control group, where specimens were produced using a mixture ratio of 30 wt% ceramic binder and 40 wt% expandable graphite. Experimental group specimens were prepared by increasing the aerogel content from 200 to 1000 mL under each condition of the control groups (pure and mixed) after mixing. The thermal insulation performance of the specimens was evaluated in terms of thermal conductivity and thermal diffusivity according to ISO 22007-2 (for solids, paste, and powders). Through this study, it was found that the thermal insulation performances of the pure control and experimental groups improved by 16.66%, while the mixed control and experimental groups demonstrated a 17.06% enhancement in thermal insulation performance with the addition of aerogel.

Diagnostic imaging of debonding in FRP-strengthened reinforced concrete structures using combinational harmonics generated by Rayleigh waves

A debonding location imaging technique (DLIT) utilising mixed-frequency Rayleigh waves is reported in this paper to predict the location of debonding in fibre-reinforced polymer (FRP) composite strengthened concrete structures. In the proposed methodology, a piezoceramic transducer network is employed to sequentially scan the FRP-concrete interface. One of the transducers serves as an actuator while the remainder serve as sensors. The incident waves which are sent by the actuator consist of two different fundamental frequencies. After the incident waves interact with debonding, additional signals are generated that coincide with the sum of the fundamental frequencies (i.e., sum frequency). The received wave component at the sum frequency is in accordance with theoretical predictions. In order to apply the DLIT, a time-frequency analysis is then applied to process the data collected by each actuator-sensor transducer pair in order to determine the signal energy density amplitudes (i.e., signal envelopes) at the fundamental frequencies and the sum frequency. Based on cross-correlation analysis between the signal envelopes of the fundamental frequencies and the sum frequency, an image can be constructed that reveals the centroid of the debonding region. Following the presentation of the proposed DLIT, numerical and experimental studies are then reported that compare the predicted centroid of debonding with the actual centroid of debonding as incorporated into the numerical model and the experimental specimens, respectively. The results demonstrate that the proposed DLIT based on the Rayleigh wave features at sum frequency can satisfactorily predict the location of debonding.

A new approach to calculate the shear strength of high-performance reinforced concrete beams fibered with micro polypropylene (experimental and analytical study)

Micro polypropylene (PP) fibers are commonly utilized to increase concrete's durability and fire resistance in building projects. High-Performance-Fiber-Concrete (HPFC) has become increasingly popular in the sustainable buildings industry in the past two decades. Some important structures were constructed using HPFC with micro polypropylene fibers to limit corrosion and increase fire resistance. This paper presents an experimental and analytical investigation to study the effect of micro PP fibers on the shear strength of HPFC beams with and without stirrups. The experimental results were used to obtain a new and simple approach that can calculate the shear strength of HPFC beams without needing for experimental findings. Also, the effect of PP fibers was compared with that of using steel (ST) fibers only or the hybridization of both PP and ST fibers. Twelve simply supported beams were fabricated and loaded with a concentrated load up to failure and all the required data were obtained and examined. The results indicated that adding PP fibers was effective in increasing both the shear capacity and the toughness of HPFC beams, either with or without stirrups, especially for beams with 1 % PP fibers. For beams without stirrups either with or without PP fibers, the mode of failure was diagonal tension shear failure. The presence of stirrups and / or ST fibers changed the failure mode from diagonal tension shear failure to compression shear failure. Analytically, a new approach of ten equations, was proposed based on the angle of compression struts and the splitting tensile concrete strength, to calculate the shear strength of HPFC beams. The equations of the proposed approach were compared with the results of forty five experimental specimens from four different research studies to examine their validity. The results were in a very good agreement and accuracy with the experimental results.

Development and validity of type II sulcus vocalis in excised canine larynx

AbstractObjectivesThis study aims to develop a sulcus vocalis model in the excised canine larynx and to investigate the validity of the model.MethodsType II sulcus vocalis was created by continuous intradermal suture in six excised canine larynges. We investigated the validity of the model based on phonatory (aerodynamic and acoustic) measures, laryngeal videostroboscopy (LVS), and histological examination. The aeroacoustic parameters included phonation threshold pressure (PTP), fundamental frequency (Fo), jitter %, shimmer %, and harmonics‐to‐noise ratio (HNR).ResultsIn all the experimental specimens, there were significant increases in the PTP ([6.61 ± 1.66] cm H2O, p < 0.01), the Fo ([106.48 ± 49.59] Hz, p = 0.003), the jitter ([0.76 ± 0.42]%, p = 0.007), the shimmer ([6.87 ± 2.99%, p = 0.002]), while the HNR decreased ([5.71 ± 4.68] dB, p = 0.031), compared to that of the untreated canine larynges. The estabilished model simulated the histology with type Ⅱ sulcus.ConclusionsType Ⅱ sulcus vocalis was successfully created in excised canine larynx. The aeroacoustic and LVS analysis of this model resembled the characteristics of patients with sulcus vocalis. The model could be helpful to elucidate the pathology of the phonation, and evaluate and compare the treatments for sulcus vocalis.

Comparison of Mechanical Property Simulations with Results of Limited Flexural Tests of Different Multi-Layer Carbon Fiber-Reinforced Polymer Composites.

This article is focused on the experimental study of flexural properties in different multi-layer carbon fiber-reinforced polymer (CFRP) composites and correlations with the results of finite element method (FEM) simulations of mechanical properties. The comparison of the results shows the possibility of reducing the number of experimental specimens for testing. The experimental study of flexural properties for four types of carbon fiber-reinforced polymer matrix composites with twill weaves (2 × 2) was carried out. As input materials, pre-impregnated carbon laminate GG 204 T and GG 630 T (prepreg) and two types of carbon fiber fabrics (GG 285 T and GG 300 T (fabric)) were used. Multi-layer samples were manufactured from two types of prepregs and two types of fabrics, which were hand-impregnated during sample preparation. The layers were stacked using same orientation. All specimens for flexural test were cut with the longer side in the weft direction. Pre-impregnated carbon laminates were further impregnated with resin DT 121H. Carbon fabrics were hand-impregnated with epoxy matrix LG 120 and hardener HG 700. To fulfill the aim of this research, finite element method (FEM)-based simulations of mechanical properties were performed. The FEM simulations and analysis were conducted in Hexagon's MSC Marc Mentat 2022.3 and Digimat 2022.4 software. This paper presents the results of actual experimental bending tests and the results of simulations of bending tests for different composite materials (mentioned previously). We created material models for simulations based on two methods-MF (Mean Field) and FE (Finite Element), and the comparative results show better agreement with the MF model. The composites (GG 285 T and GG 300 T) showed better flexural results than composites made from pre-impregnated carbon laminates (GG 204 T and GG 630 T). The difference in results for the hand-impregnated laminates was about 15% higher than for prepregs, but this is still within an acceptable tolerance as per the reported literature. The highest percentage difference of 14.25% between the simulation and the real experiment was found for the software tool Digimat FE 2022.4-GG 630 T composite. The lowest difference of 0.5% was found for the software tool Digimat MF 2022.4-GG 204 T composite. By comparing the results of the software tools with the results of the experimental measurements, it was found that the Digimat MF 2022.4 tool is closer to the results of the experimental measurements than the Digimat FE 2022.4 tool.

Experimental study on the influence of welding structure details of TC4 titanium alloy under thermo-vibration coupling environment on vibration fatigue life

The widespread application of titanium alloy materials in aerospace structural design makes them susceptible to thermo-vibration coupling fatigue failure in harsh vibration and thermal environments. Vibration fatigue issues significantly affect the safety and operational reliability of aircraft. In order to obtain optimal design details for titanium alloy welding structures under thermo-vibration coupling conditions, experimental specimens with different structural details of TC4 titanium alloy welding structures were designed to simulate actual structural designs. The structural details included skin with U-shaped supports at different angles, skin with L-shaped supports, and skin with T-shaped supports. A thermo-vibration coupling vibration fatigue test system was established, and vibration fatigue tests were conducted at a temperature of 150°C. All structural fatigue crack failures occurred at the welds. The experimental results were statistically analysed, and using the Chauvinet criterion, abnormal data points were removed. The influence of structural details on vibration fatigue life was determined through F-tests. It was found that for the skin with a U-shaped support structure, a support angle of 90° resulted in a longer vibration fatigue life. When comparing skin with T-shaped support and skin with L-shaped support structures, the T-shaped support structure exhibited a longer vibration fatigue life. Among the three structural types, the skin with a T-shaped support structure has the longest vibration fatigue life. These experimental conclusions serve as important references for the design of thin-walled structures in aircraft structural design.

Effect of ultrasonic and Er,Cr:YSGG laser-activated irrigation protocol on dual-species root canal biofilm removal: An in vitro study.

The aim of the study was to investigate the disinfecting efficacy of a standardized irrigating solution activated by ultrasonics or laser irradiation on mature dual-species biofilms at different root levels in vitro. Conventional access cavity preparations were done on 160 single-rooted mandibular premolar teeth with single canals. Freshly extracted oral microbial strains of Staphylococcus aureus, Streptococcus mutans, Enterococcus faecalis, and Candida albicans after biochemical confirmation were used to generate two discrete dual-species microbial inoculums. The sterilized tooth samples were randomly segregated into two groups (n = 80) and inoculated with a mixed inoculum of S. aureus + E. faecalis strains (Group 1) and S. mutans + C. albicans strains (Group 2), respectively. Following the 21-day incubation period under aerobic conditions, the infected specimens in each group were divided into four subgroups (n = 20) and subjected to experimental treatment protocols. This included a positive control (no treatment of biofilms), syringe irrigation alone with TruNatomy needle, passive ultrasonically activated irrigation with 20# Irrisafe tip, and laser agitation of irrigant with Er,Cr:YSGG laser using RFT 2 laser tip. Root canals of experimental specimens (except the control samples) are instrumented with TruNatomy rotary file system using 1:1 mixture of 3% NaOCl and 18% etidronic acid as irrigants. The quantitative assessment of reduction in viable biofilm microbes after treatment was done using colony-forming unit counts and confocal laser scanning microscopy image analysis. The obtained data were analyzed statistically with a significant level set at 0.05. Laser-assisted irrigation has shown a considerably higher mean percentage reduction of microbes compared to ultrasonic agitation and the syringe irrigation showed the least microbial reduction (P = 0.001). No significant difference was noted between the three root regions of ultrasonic and laser groups (P > 0.05), whereas in the syringe groups, apical portions showed higher microbial counts compared to cervical and mid-root regions (P = 0.001). Erbium laser-assisted irrigation has performed superior to ultrasonic agitation against both the experimental dual-species biofilms, while the syringe irrigation showed the least microbial reduction specifically at apical root portions.

Predictive modeling of wide-shallow RC beams shear strength considering stirrups effect using (FEM-ML) approach

This paper presents an analysis and prediction of the shear strength of wide-shallow reinforced concrete beams, utilizing Finite Element Analysis (FEA) and machine learning techniques. The methodology involves validating a detailed Finite Element Model (FEM) against experimental results, conducting a parametric study, and developing three Machine Learning prediction equations. The FEM captures concrete and steel behaviors, including cracking and crushing for concrete and linear isotropic properties for steel reinforcement. Loading and boundary conditions are defined for accuracy and validated against 13 experimental specimens, exhibiting a maximum 8% and 12% difference in loads and deflections, respectively. A parametric study generates a dataset of 77 wide beam configurations, exploring variations in beam widths, concrete strengths, compression rebars, and shear reinforcement. This dataset is used to develop machine learning models, including “Genetic Programming (GP)”, “Evolutionary Polynomial Regression (EPR)”, and “Artificial Neural Network (ANN)”. Comparative analysis reveals GP and EPR models with over 95% correlation, while the ANN model outperforms with 99% accuracy. Sensitivity analysis underscores the significant influence of concrete strength and beam aspect ratio on shear strength. In conclusion, the study demonstrates the potential of FEA and machine learning models to predict shear strength in wide-shallow reinforced concrete beams, providing valuable insights for architectural design and engineering practices and emphasizing the role of concrete strength and beam geometry in shear behavior.

Assessment of the resistance to lodging of spring triticale based on the study of physical and mechanical properties

The results of the study of architectonics and physical and mechanical properties of the stems of selective forms of spring hexaploid triticale of different ecological and geographical origin are presented. Traits of 19 collection and breeding samples from the collections of the N.I. Vavilov All-Russian Institute of Plant Genetic Resources (VIR) and the Siberian Research Institute of Plant Growing and Selection - branch of the Federal Research Center of the Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences (SibNIIRS – branch of the Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences) served as research objects. Macrometric parameters were studied on 25 representative specimens of each breeding sample when they reached the phase of full ripeness during three years (2021–2023). The resistance of the stem to bending or fracture was determined on an experimental specimen manufactured at the SibNIIRS with a stable platform, bars for fixing the specimen and a slot for placing a dynamometer. The susceptibility of triticale plants to lodging was evaluated by a set of traits: weight of a 10-cm straw of the 2nd internode; stem resistance to breaking determined by the peak reading of an electronic dynamometer; stem tissue density of the 2nd internode. The studied samples differed significantly in these parameters and were characterized by different degrees of the resistance to lodging. Promising breeding specimens that can be used as sources of valuable traits have been identified based on the totality of the strength parameters. Application of the principal component method allowed to identify the marker trait "sum of lengths of the 2nd and 3rd internodes", which was determinant in providing high lodging resistance in the studied samples. A close relationship between the trait of 10-cm straw mass of the 2nd internode and the parameter of the stem resistance to breakage has been established. The conjugation of these characteristics will make it possible to identify the sources of valuable traits and purposefully carry out the selection process of triticale for resistance to lodging without attracting short-stemmed forms.

Multi-scale study on the mechanical properties of concrete based on crack propagation under hygrothermal coupling

During the long-term service of structures, the environmental temperature and humidity fields can lead to the evolution of the pore structure within concrete materials, thereby affecting changes in mechanical properties. However, the mechanisms of their influence still need further clarification and are challenging to correlate for prediction. Addressing this specific issue, the current study focuses on evaluating 78 cubic concrete specimens with C30 and C40 strength grades. These specimens were subjected to a 95 % humidity environment at temperatures of 40 °C, 60 °C, and 80 °C for durations of 30, 60, and 90 days. The research involved conducting both microstructural and macroscopic mechanical tests to quantify the evolution of internal hydrates, pore structures, and pore distribution, as well as to assess the changes in the macroscopic mechanical properties of the specimens. To accurately predict the process, a multiscale finite element model (FEM) based on the bilinear continuum cohesive damage model was established. This model quantifies the changes in mechanical properties of mesoscopic three-phase concrete due to microcrack evolution under hygrothermal coupling. To facilitate multiscale simulations between the Representative Volume Element (RVE) and macroscopic scale models, relevant subroutines were written using Umath, and parallel computing was employed to reduce the computational burden. For the macroscopic model in this study, a homogenized concrete cube model with dimensions identical to the experimental specimens was selected. The effectiveness of the parallel computational model was validated by comparing and analyzing the simulation results under uniaxial compression with the experimental data. The findings indicate that hygrothermal action leads to the initiation and expansion of microcracks within the concrete, thereby impacting the alteration of its mechanical properties. In addition, the parallel computing-based multiscale FEM can more accurately quantify the typical damage process of crack propagation while reducing the computational load and may provide relatively accurate predictions of the mechanical characteristics of concrete under the influence of hygrothermal coupling, ensuring effective modeling of macroscopic structural specimens in various temperature and humidity environments.

Seeking the most informative design of test specimens for learning constitutive models

Accurate calibration of constitutive models is vital for predicting the mechanical behavior of engineering materials under various loading conditions. Traditionally, the calibration process involves a series of experiments on specimens with simple geometries to capture the complexities in the constitutive models. Each single test conveys a small amount of information that a well-trained human brain can handle, resulting in a large number of experiments needed for a complete calibration. Therefore, traditional calibration approaches are usually costly and time-consuming. With recent advancements in computational techniques, there is an emerging opportunity to leverage geometrically complex specimens in experiments to obtain a larger amount of information for computers to learn and calibrate the model. Despite some initial success, the most important question remains unsettled: How much information does a mechanical test convey? In this work, we answer this question by incorporating information entropy as a quantitative measure in the design of mechanical test specimens. We demonstrate the viability of the proposed approach by comparing the performance of selected test specimens for learning the plasticity model of sheet metal, e.g., the Hill48 anisotropic elastic-plastic model in this case. An optimal entropy criterion is proposed for selecting the appropriate heterogeneous test specimen for inverse calibration, depending on the cardinality of the stress state space considered in the model. Finally, Bayesian optimization is applied to uniaxial and biaxial tension specimens, using the stress state entropy as an objective function, to investigate the general principles of designing specimens with maximum information for learning constitutive models.

Study on Microscopic Characteristics and Rock Mechanical Properties of Tight Sandstone after Acidification–Supercritical CO2 Composite Action: Case Study from Xujiahe Formation, China

Acidified CO2 fracturing is a viable method for increasing production in deep, tight sandstone reservoirs. However, the potential mechanism of changes in pore structure and mechanical properties of sandstone under acidified CO2 supercritical composite is not clear. Understanding this mechanism is important for the study of crack initiation and extension in tight sandstone reservoirs. This study utilizes sandstone samples from the Xujiahe Formation reservoir in Rongchang District as experimental specimens. The primary focus is to analyze the changes in pore structure and mechanical properties of these samples after acidification–supercritical CO2 composite action. Nuclear magnetic resonance (NMR) and uniaxial compression tests are employed as the main investigative techniques. The results show that there was a physicochemical synergy between the acidification–supercritical CO2 composite effect; the crack initial stress, damage stress, and peak stress of the sandstone after 16 MPa supercritical CO2 acidification treatment were reduced by 20%, 49.5%, and 49.8%, respectively; the crack volumetric strain accelerated and the sandstone evolved from brittle to ductile damage; and the larger pore space and microcracks of the sandstone increased significantly after the treatment, which can be attributed to the gradual dissolution of intergranular cement leading to the formation of new pores connected to the existing pore network. The change mechanism of sandstone after acidification–supercritical CO2 compound treatment is also proposed.

3D novel zero Poisson’s ratio metamaterials with programmable thermal expansion and Young's modulus

The shape stability of the structure plays a very important role in deep space exploration engineering. This paper presents 3D novel zero Poisson’s ratio metamaterial (ZPRM) with programmable thermal expansion and Young's modulus through the combination of bi-material triangles and re-entrant hexagonal structures. The coefficient of thermal expansion (CTE) and Young's modulus of the ZPRM-1 are predicted by establishing theoretical analysis models based on the classical beam theory. The mechanical response behavior of the ZPRM −1 under small deformation is simulated by finite element analysis (FEA). 3D printing is adopted to design and prepare experimental specimens, and compression experiments are carried out to certify the accuracy of the theories and FEA of Young's modulus. The results of parameter analysis show that the ZPRM-1 can tune the CTE and Young's modulus in a wide range when the geometric parameters and material combination are changed. In addition, the mechanical properties of the ZPRM-1 under the combined field of temperature and mechanical loads are investigated to achieve the tunable Young's modulus from positive to negative. This study provides a feasible reference for temperature and mechanical sensitivity instruments.

Research on the new method for visualizing bendability testing of fabrics in multiple directions

PurposeThe current bending test method can only test the bending performance of fabric in one direction at a time. It is not possible to directly observe the bending morphology of fabrics in different directions, and it is necessary to cut samples and repeat the test several times, which takes more time. For this situation, a multidirectional visualization of the fabric bending test method is proposed, using which multiple results can be obtained at one time and the fabric bending can be visualized.Design/methodology/approachAbout 17 fabrics are tested using a self-designed device. The fabrics are cut into special triangles and multiple sets of results in three directions are obtained at once using the device. The experimental specimens are photographed from the above and the transverse elongation length, bending projection area and circumference are extracted after image processing.FindingsThe results show that the correlation coefficients of transverse elongation, bending projected area and circumference are good with the bending length measured by the cantilever method. In which, all three indicators are positively correlated with the bending length. This indicates the good feasibility of the new method.Originality/valueThis method can get the bending index of fabrics in three directions, with five samples in each direction at one time. Meanwhile, it can also visualize the flexural differences between different fabrics and directions of the same fabric. It can provide more efficient testing means for the textile testing field, and the testing efficiency is 15 times of the existing method, which has better theoretical significance and practical values.

Simulated Hydrostatic Pulpal Pressure Effect on Microleakage-An Initial Study.

This study's purpose was to evaluate the effect of simulated in vitro hydrostatic pulpal pressure (HPP) on microleakage. Extracted third molars (n=12) were sectioned 5 mm below the cementoenamel junction, pulp tissue removed, and the sectioned crowns mounted on a Plexiglas plate penetrated by an 18-gauge stainless steel tube. The mounted specimen mesial surface received a 2×4×6 mm Class V preparation followed by restoration with a strongly acidic, one-step dental adhesive and a flowable microfilled resin, following all manufacturers' instructions. Restorations were finished to contour, and tubing was attached to a 20-cm elevated, 0.2% rhodamine G reservoir to the specimen steel tube for 48 hours. Specimens then received a nail polish coating to within 1 mm of the restoration margins and were placed in 2% methylene blue (MB) dye for 24 hours, followed by rinsing, embedding in epoxy resin, and sectioning into 1 mm slices using a diamond saw. Controls were intact molars (n=12) processed as above but without HPP. Specimen slices were evaluated using laser confocal microscopy with images exported to ImageJ software with microleakage assessed as the MB linear penetration as a percentage of the total interfacial wall length. Mean values were evaluated with the Kruskal Wallis/Dunn test at a 95% confidence level. The control specimens demonstrated significantly greater (p<0.0001) MB penetration than experimental specimens with simulated HPP. Under this study's conditions, simulated HPP significantly decreased MB dye penetration. Studies accomplished without simulated HPP may overestimate microleakage results.

Influence of Sunflower Seed Husks Ash on the Structure Formation and Properties of Cement Concrete

The limitation of the application of non-renewable materials is one of the solutions to the problem of the sustainable evolution of civilization in the 21st century. Using additional binders in concrete obtained from plant waste will be economically and environmentally beneficial and will also allow us to move closer to achieving sustainable development goals. This study searches for rational composition components and a methodological approach regarding the technological characteristics to get the highest quality elements and prime concrete properties on the basis of sunflower seed husk ash (SSHA). Experimental concrete specimens were manufactured with partial Portland cement substitution with SSHA amounts ranging from 2% to 16% by weight in increments of 2%. This study focuses on investigating the density and workability of the concrete mixture, along with the compressive strength, concrete density, and water absorption. This article used granulometric, microscopic, and X-ray phase analysis methods. Including SSHA in all considered ranges reduces the slump in concrete mixtures. The optimal SSHA content in concrete is up to 12%. An 8% SSHA content has been found to deliver the most favorable mechanical characteristics of the concrete studied. The compressive strength of the investigated concrete has increased by 14.89%, and water absorption has decreased by 15.78%. Doi: 10.28991/CEJ-2024-010-05-08 Full Text: PDF