Ultimate Bending Strength Research Articles

Bio-inspired discontinuous composite materials with a machine learning optimized architecture

Bio-inspired hierarchical discontinuous fibrous composite materials are investigated with the aim of achieving enhanced pseudo-ductility and elevated toughness. A novel methodology is proposed to search quickly and efficiently through the vast design space of the geometrical parameters of the discontinuities, combining advanced numerical simulations of the material’s mechanical behavior with state-of-the-art Machine Learning approaches, such as Active Learning. A continuum mesoscale-based numerical model is developed to simulate the mechanical behavior of discontinuous composites under three-point bending loading and is utilized in a sequential Bayesian optimization scheme that iteratively searches for the material architecture that maximizes toughness. Five independent geometrical variables related to the size and exact topology of the discontinuities form a vast five-dimensional design space of more than 2.6 million possible combinations. In this space, the proposed methodology efficiently identifies, after 100 iterations, a remarkable optimal configuration that increases the material’s toughness by more than 100%, with a knock-down effect on the ultimate bending strength of only 10%.

Mechanical performance analysis of double-dovetail joint applied to furniture T-shaped components

T-shaped mortise and tenon members are the main structure of traditional Chinese furniture. In this paper, the double-dovetail joint used for face-to-face joint of rubber wood (Hevea brasiliensis Muell. Arg) is transformed into a new type of double-dovetail joint and rounded double-dovetail joint for T-shaped members of point joint structure. The ultimate pull-out test and bending strength test were carried out on the two structures and three structures of oval mortise, round rod mortise and right angle mortise. The results show that the ultimate pull-out force of the round double-dovetail joint is 39% higher than that of the double-dovetail joint, and the bending resistance capacity is 8.9% higher, and the strength and stability are better than those of other split mortises and tenons, which proves that this structure can be used in actual production, and also proves that the mortise and tenon connected by the surface has the possibility of transforming into a point connection structure. The concave structure of the rounded double-dovetail joint makes the mortise and tenon fit well, the tenon squeezed tight, and a good bonding effect was achieved. This structure can also provide greater friction and resistance, delay rubber adhesive failure and improve the stability.

Parametric study of side collision-induced denting failures on the ultimate strength of a handy-size containership under vertical bending

This study focuses on analysing the collision behaviour and residual ultimate bending strength of a container ship following a collision. Initially, computational models employing nonlinear finite element analysis (NFEA) were used to consider dynamic material parameters like strain rate and crack strain. The accuracy of this numerical approach was verified by comparison with test results. Subsequently, various collision scenarios were analyzed using ABAQUS software, encompassing diverse impact velocities, indenter shapes, and boundary conditions. The aim was to evaluate the reduction in the residual ultimate bending strength of a container ship hull resulting from collisions at both sagging and hogging moments. Finally, empirical equations were formulated to forecast the residual ultimate bending strength based on numerical findings. These equations exhibited excellent accuracy when validated against numerical and experimental data. This methodology and its equations provide valuable tools for assessing the post-collision strength of container ships and enhancing maritime transportation safety.

Experimental Design and Analysis of MWCNT, Nanoclay and ZnO Nanofillers on Bi-Directional-Chopped Stranded Glass Fibre Reinforced Epoxy Matrix on Mechanical Properties using L9 and L18 Taguchi’s Orthogonal Technique

Stealth, mechanical and thermal properties, resistance to fire by limiting oxygen and retarding flame can lead to save several human lifes travelling and working in civil, commercial as well as defence air transport and could even develop drone and aircraft meant to escape enemy countries radar tracing and monitoring range. GFRP play very important role in engineering application. The composite manufactured using nanofillers have found to posses better propeties in certain application. In the present work, MWCNTs, Nanoclay and ZnO have been used in GFRP. The developed material can be a promising replacement of composites being used for structural applications in the aerospace sector and space technology apart from the automotives to impart light weight, superior bending and tensile strength. Testing of GFRP infused nanofillers was conducted to obtain the ultimate tensile strength and flexural bending strength of the composite. Experimental design with three Nanofillers as parameters at three levels for optimization of output characteristics with superior properties for structural applications was done using Taguchi’s L9 and L18 orthogonal arrays. ANOVA Analysis was also performed for both L9 and L18 arrays. The effects of three nanofillers infused GFRP was investigated and their impact on tensile and flexural strength were evaluated.

Ultimate strength failure mechanism and optimization design of marine composite deck grillage structures with opening

In this paper, the ultimate bending strength and the failure mechanism of the marine composite deck grillage structure are experimentally and numerically investigated, before the optimization design is conducted to enhance the ultimate bearing capacity. The ultimate strength experiment of the composite deck grillage structure is first carried out. Based on the improved progressive failure method and the cohesive damage theory, the numerical simulation considering fiber failure, matrix failure, shear failure and adhesive layer failure is conducted and the predicted strains, load–displacement curves, and failure modes of the specimen are compared with the experimental ones to verify the accuracy of the present method. Both experimental and predicted results show that the stiffeners and the laminated deck near the opening are the stress concentration areas, and the matrix failure is main failure mode. The optimization results show that the suitable panel thickness can reduce the stress concentration effect and avoid premature fracture in localized areas due to stress concentration. The increase of the stiffener heights can significantly increase the ultimate strength and the bending stiffness. These findings can provide support for the design of composite deck grillage structures in ships.

Strength degradation of GFRP cross-ply laminates in hydrothermal conditions

The changes in mechanical properties of glass fiber reinforced plastic cross-ply laminates as a result of hydrothermal aging were studied theoretically. The composite specimens have been immersed in distilled water at 25, 40, and 70 °C for 60 days for aging testing. Based on Fick’s law and the Arrhenius theorem, the moisture absorption data under different environments was analyzed, and the method for determining the diffusivity and the equilibrium moisture content was obtained. The relationship model between the moisture absorption behavior of the composite material and the ambient temperature was proposed and verified by finite element analysis. The mechanical behavior of the composites was studied by tensile, compression, and three-point bending tests. Under the condition of ultimate moisture absorption, the tensile, compressive, and bending strengths of the composite decreased by 31.663%, 12.948%, and 26.985%, respectively. A variety of empirical models were used for data analysis, which confirmed the strong correlation between strength degradation and moisture absorption of composite cross-ply laminates. The scanning electron microscope observation results of different moisture absorption levels showed that matrix cracking and fiber/matrix interface debonding caused by moisture absorption are the fundamental reasons for the strength degradation of the composites.

Experimental and Numerical Studies on the Ultimate Bending Strength of Welded Plated Grillage with Combined Openings

Plated grillage with combined openings was susceptible to complex failure behaviors as the main load-bearing structure of the superstructure on passenger ships subjected to deck loads. Additionally, the deformation and stresses generated during the welding of the plated grillage complicated the prediction of its failure behavior. In this case, a new partitioned inherent strain method and nonlinear finite element method were used to simulate the welding and loading process, and experiments were designed and carried out to make comparisons, unveiling the influence regulations between the failure behavior of the structure and the loading condition, the initial welding state. This research on the failure mode analysis of plated grillages could provide references for the optimization of the structural form of plated grillages and the cargo loading scheme on the deck of a real ship.

Структура и прочность пористых материалов на основе порошков карбида титана разной дисперсности

Materials with porosity from 67.5 to 82.5 % were obtained from mixtures of titanium carbide powders and ammonium bicarbonate blowing agent by sintering in vacuum at temperatures of 1300 – 1500 °C. X-ray phase analysis of porous materials found that the crystal lattice parameter decreases with increasing sintering temperature. This indicates a decrease in the content of bound carbon C/Ti in titanium carbide. As a result of a comparative study of the obtained according to bending test strength characteristics of materials synthesized from nano- and submicron titanium carbide powders, it was found that the strength have close values. Ultimate bending strength are in the range of 2.6 – 18.1 MPa. As the porosity of the material increases, the tensile strength decreases. Fracture is brittle. In the fracture of materials obtained from titanium carbide nanopowder, destruction is observed both along the body and along the grain boundaries regardless of the sintering temperature. In materials obtained by sintering submicron titanium carbide powder at 1500 °C, the destruction occurs predominantly along the body of the grains. It has been found that under the same sintering conditions, the density of the porous material made of titanium carbide nanopowder is higher than that of the material made of submicron powder.

Development of an effective technology for producing composite wood-plastic board materials for construction and furniture purposes

This article presents the results of research in the development of an effective technology for obtaining composite wood-plastic board materials for construction and furniture purposes based on fillers from cotton stalks, which are agricultural waste, and polymer binders based on modified urea-formaldehyde and gossypol resins, epichlorohydrin, benzyl chloride, and polyvinyl chloride. The study revealed a correlation between the ultimate bending strength, tensile strength and water absorption with the parameters of pressing polymer-fillers of the mass. At the same time, to obtain composite wood-plastic board materials, it is recommended to use a urea-formaldehyde resin modified with reactive structuring additives as a binder. It has been established that the optimal technological mode for pressing the mass of polymer fillers and cotton stalks is: specific pressure 35 kg/m², pressing temperature 168-170°C, heating duration 7-10 minutes. Key words: technology, composition, modified urea-formaldehyde resin, cotton stem filler, wood-plastic board, specific pressure, pressing temperature, heating duration, water absorption, tensile strength.

Circular steel tube-confined ultra-high performance concrete beam-column: Database, modeling, and design

The fiber beam element (FBE) model is widely used to simulate and predict the nonlinear behavior of structures owing to its simplicity and high computational efficiency. The accuracy of the FBE simulation of ultra-high-performance concrete (UHPC) filled steel tubular (UHPCFST) members is mainly dependent on the input materials and interactions between the steel tubes and concrete, such as second-order effect, yielding of steel tubes and passive confinement effect to the UHPC. This work proposes uniaxial effective stress-strain models of UHPC confined by circular steel tubes based on existing experimental data that are integrated into the FBE model to predict the nonlinear behavior of UHPCFST members. The robustness and reliability of the proposed material models are comprehensively verified against a database encompassing a wide range of materials and geometric parameters under different loading conditions (monotonic and cyclic loading). Furthermore, the application of existing design codes for computing ultimate bending strengths is assessed using an established experimental database. Finally, the ultimate bending strengths of circular UHPCFSTs are calculated using a novel and simplified N–M interaction equation. It is demonstrated that the developed material models could predict the nonlinear behaviors of circular UHPCFST members with good satisfaction, and that current design codes, to some extent, underestimate the ultimate bending strengths of circular UHPCFST columns, the proposed practical method in this study is highly accurate, with a mean value of 1.00.

High-Temperature Bending Tests of Reaction-Sintered Silicon Carbide-Based Ceramic Materials

The high-temperature strength properties of silicon carbide-based ceramic materials reaction-sintered in air and vacuum are proved by experimental data. The ultimate bending strength of pressed and cast ceramic material samples at temperatures up to 1400°C was measured as a criterion. High-temperature tests demonstrate the guaranteed strength of ceramics above 100 MPa. An example of the manufacture of a complex shaped ceramic product using the hot slip casting processing under pressure into additive water-soluble forms is given. An approval of the combined technology makes it possible to manufacture bladed ceramic elements with a thickness of about 1 mm.

Optimization of TIG welding process parameters on 304 austenitic stainless steel sheet metal using fuzzy logic based Taguchi method

TIG welding can be used to produce excellent weld quality and precise welding operation for sheet metals. The aim of this study was to get the best welding parameters for enhancing ultimate tensile strength, bending strength and Rockwell hardness of the butt-weld joint. The experimental work was used, and the experiment was carried out on 2 mm thickness of 304 austenitic-stainless steel sheet metal using the L9 orthogonal array of the Taguchi design. Automated TIG welding fixture was developed to control the welding speed accurately. The selected welding parameters were welding speed, current, voltage and gas flow rate with their three levels. Based on the fuzzy logic based Taguchi method, the best optimal levels of parameters were found at the values of 110 A of current, 13.86 cm/min of speed, 17.5 V of voltage and 7.5 L/min of gas flow rate. The analysis results of ANOVA showed that gas flow rate and current were found as the significant factors, and the contributions of the gas flow rate, current, speed and error were 47.63%, 34.34%, 16.49% and 1.54%, respectively. According to the confirmation tests, the multi response performance index mean value of the confirmatory test of 0.6068 was found between the 95% confidence interval of 0.5028 and 0.7314, and the maximum ultimate tensile strength, bending strength and Rockwell hardness were obtained 614.8 MPa, 765.32 MPa and 95.3 HRB, respectively.

Effect of intrinsic thermal cycles on the microstructure and mechanical properties of heat affect zones in laser cladding coatings on full-scale rails

Laser cladding (LC) wear-resistant alloy on the surface of pearlite rails has been proven to be able to improve their wear resistance significantly. However, the rapid cooling rate in LC will result in the formation of martensite structures with high hardness but low toughness in heat affected zone (HAZ), making the rails' service safety endangered. In this paper, a novel method was proposed to eliminate the un-tempered martensite in U71Mn rail based on the in-situ gradient tempering (IGT) effect induced by the intrinsic thermal cycles in multilayer LC. The influence mechanisms of interlayer and inter-track thermal cycles on the evolutions of microstructure and mechanical properties of HAZs were studied systematically. The results illustrate that the martensite in HAZs can be gradually tempered within the optimal IGT temperature range, and the tempering processing mechanisms are as follows: firstly, the ε-carbides precipitate from HAZs and then dissolve to form granular cementites. Then, the cementites form colonies of lathlike particles with similar orientations. Finally, a composite structure consisting of fine-tempered sorbite and granular cementites forms, in which the lamellar spacing of sorbite is <1/5 of that of the original pearlite, and the proportion of the high angle grain boundaries has increased by 2.2 times. During the tempering process, the microhardness of HAZs gradually decreases, accompanied by the increase of the bending properties therein. The ultimate bending strength and fracture strain of the specimens with fully tempered HAZs are enhanced to be about 1.6 and 5.5 times as much as those of the specimens with fully quenched HAZs, even much better than the substrate.

A research on similarity law for combined ultimate bending and torsional strength

ABSTRACT As basic structural components of the ship hull, stiffened plates suffer both thrust and shear loads while ships sail in rough sea environments. In order to guide the scaled model design effectively, the similarity law is investigated in this paper. The parameters that determine the nonlinear behaviour of the stiffened plate under compression and shear loading are defined and the nonlinear similarity method is improved. This method is applied to design a scaled model under combined bending and torsional moment, and the collapse test is conducted to research the collapse characteristics. The collapse behaviour of actual ship structures under combined loads predicted by the model test is compared with that obtained by the nonlinear finite element analysis. The good agreement represents the capability of the newly improved nonlinear similarity law. The present research provides a proper way to investigate the collapse characteristics of actual ship structures through a model test.

Influence of Powder Charge Composition on the Structure and Properties of T15K6 Hard Alloy

The purpose of the study is to determine the effect of nanosized additives on the structure and properties of the T15K6 hard alloy.Methods. These studies were carried out using an S-3400N electron microscope. The mechanical and physical properties of the structure of a hard alloy of the WC-TiC-Co system were studied using the example of T15K6 when nanosized tungsten powder and nanosized tungsten carbide powder with cobalt deposited on it were introduced into the initial charge using an optical and electron microscope; An X-ray spectrum analysis of the obtained samples of the T15K6 hard alloy was carried out on a DRON-4 X-ray diffractometer.Results. A hard alloy of the WC-TiC-Co system was studied with the introduction of nanosized tungsten powder into the initial charge, as well as with the introduction of nanosized tungsten carbide with cobalt deposited on its surface.In the work, the used powders of tungsten, nano-tungsten, cobalt, titanium carbide, tungsten carbide, nano-powder of tungsten carbide were studied, and the microstructure of the obtained hard alloys was also studied. It is shown that the coercive force of the T15K6 alloy depends on the size of the cobalt phase regions in the alloy; measuring its value makes it possible to judge the size of carbide grains. To improve the strength properties of hard alloys of the WC-TiCCo system, it is recommended to introduce nanosized WC additives or WC nanopowder with deposited cobalt.Conclusion. To improve the strength properties of hard alloys of the WC-TiC-Co system, it is recommended to introduce nanosized WC additives or WC nanopowder with deposited cobalt. The introduction of these additives into the composition of the powder charge of the T15K6 hard alloy leads to an increase in the ultimate bending strength by 15%. The introduction of nanosized WC additives or WC nanopowder with deposited cobalt makes it possible to obtain a fine-grained structure with a grain size of no more than 4–6 μm.

Bending performance of nail laminated timber: Experimental, analytical and numerical analyses

Nail laminated Timber (NLT) is a kind of mass timber product becoming popular in recent years. To further understand the bending performance of NLT and motivate its utilization in engineering, experimental, analytical and numerical analyses were conducted in this study. Spruce-pine-fir (SPF) dimension lumber was used as the lamination to fabricate the NLT and four-point bending test was conducted on ten NLT specimens. The failure modes, modulus of elasticity and load-carrying capacity of the NLT were investigated. Results showed that the dominant failure mode of specimens was tension failure at the bottom of the laminations. The bending strength of the NLT corresponding to the occurrence of the first lamination failure was about 11.4% lower than the ultimate bending strength. The average modulus of elasticity and the average ultimate bending strength of the NLT were close to those of the laminations. Considering the property difference of the laminations, an analytical method was proposed to analyze the internal force of NLT. Then, the finite element model of NLT was established and further calibrated by the experimental and analytical results. The comparison proved that both the analytical and numerical methods could effectively predict the bending performance of NLT.

Effect of the Ti/Ta ratio on the feasibility of porous Ti25+x-Nb25-Zr25-Ta25-x (X= 0, 5, and 10) alloys for biomedical applications

Non-toxic biomedical HEAs by powder metallurgy methods have been scarcely studied despite their promising mechanical and biological behaviors. This work studied the microstructural, mechanical, electrochemical, and ion release effects of the Ti/Ta ratio on three porous Ti–Nb–Zr–Ta (TNZT) alloys. The microstructure of the TNZT alloys consisted of semi-equiaxed and micrometric BCC-phases (matrix) with lower contents of HCP phase. Elastic moduli (82–91 GPa), hardness (373–430 HVN), ultimate bending (225–475 MPa), and tensile (119–256 MPa) strength, electrochemical corrosion (4.5–9.6 μm year−1), and ion release (toxicity, 0.9–1.1 μm year−1) were within acceptable limits for implant biomaterials. Increasing the Ti content (and decreasing Ta) was advantageous for improving mechanical strengthening and reducing the elastic modulus. The medium value of elastic modulus may be beneficial to reduce the mechanical mismatch between the implant and the organic tissue. However, the corrosion rate and metallic ion release increased as a function of the Ti content. Besides, the alloy with the lowest Ti content (highest Ta content) showed local corrosion. Based on the above, the porous TNZT alloys with medium and highest Ti contents (30 and 35 wt%) were demonstrated as promising candidates for biomedical implant applications.

Investigation of the hygrothermal aging behavior of GFRP laminates used for a marine unmanned aerial vehicle structure

In this study, the hygrothermal aging behavior of E-glass fiber/epoxy composites was investigated. The moisture absorption data and diffusivity of the composite laminates were determined by conducting five sets of aging tests at different temperatures and humidities. Based on the Shen and Springer model and the Arrhenius model, a relationship model between environmental parameters and moisture absorption behavior was proposed, which was verified by experimental data and Fick’s law. The Rajaram empirical model was used to predict the aging strength of composite laminates as a function of moisture content. Under the condition of ultimate moisture absorption, the tensile, compression, and bending strengths of the laminate decreased by 24.126%, 11.148%, and 24.942%, respectively. Scanning electron microscopy observations showed that swelling cracks and fiber/matrix interface debonding caused by moisture absorption of the resin matrix are the key factors affecting the macroscopic properties of the composites.

Experimental and Analytical Investigation on Flexural Behavior of High-Strength Steel-Concrete Composite Beams

This research investigated the flexural behavior of high-strength steel (HSS)—concrete composite beams. The effect of concrete strength on the load-deflection behavior, flexural capacity, and ductility of HSS—concrete composite beams was investigated. Four full-scale HSS—concrete composite beam specimens were tested under static load. The test results demonstrate that the failure mode of HSS—concrete composite beams is flexural failure of the steel member and compression fracture of concrete at mid-span. The HSS—concrete composite beam exhibits good mechanical performance and deformation behavior. The ultimate bending strength and ductility of HSS—concrete composite beams were improved with the increased concrete strength. The theoretical results demonstrate that the simplified plastic method overestimates the ultimate bending strength of HSS—concrete composite beams. The main reason is that only a small part of the steel beam bottom shows plastic strengthening, which is not enough to make up for the strength loss caused by the steel near the neutral axis failure to yield and the relative interface slip. The nonlinear method based on material constitutive model could predict the load-bearing capacity accurately. After analyzing the ultimate bending capacity of 192 sample beams, the simplified plastic method was modified, and the theoretical method for ultimate bearing capacity of HSS—concrete composite beams was proposed.

Effects of interval time and interfacial agents on the mechanical characteristics of ultra-high toughnessnn cementitious composites under 3D-printed technology

Anisotropic mechanical characteristics are crucial to the application of the printed structure. This study is aimed to investigate the effects of interval time and interfacial agents on the anisotropic mechanical strength of ultra-high toughness cementitious composite under 3D-printed technology. The bending capacity of ultra-high toughness cementitious composite under 3D-printed technology was compared with mould-casting ultra-high toughness cementitious composite. The compressive strength, flexural strength and splitting tensile strength were measured to represent mechanical properties in different directions and the microstructure of ultra-high toughness cementitious composite under 3D-printed technology with different interval time and interfacial agents were characterized using nanoindentation, scanning electron microscopy, and X-ray computed tomography. The experimental results indicated that the ultimate bending strength and bending toughness of ultra-high toughness cementitious composite under 3D-printed technology were 13.6% and 3.3% to 13.3% higher than those of mould-casting ultra-high toughness cementitious composite at 28 d, respectively. As the interval time increased, the mechanical properties showed differential development patterns. Specifically, compressive strength and splitting tensile strength had a higher rate of decline in the X direction (parallel to the printing path) than in the Y and Z directions but flexural strength was the opposite. A 3-h interval time reduced the 28-d compressive strength and splitting tensile strength in the X direction by 24.02% and 49.64% but the strength only decreased by 10.57% and 26.59% in the Z-direction. The addition of interfacial agents reduced anisotropy in compressive strength and splitting tensile strength but increased the anisotropy of flexural strength. When the interval time was 3 h, the increase rate of the 28-d flexural strength in the X direction, in which the flexural strength was weakest, was 22%–29% lower than that in the Y and Z directions under the effects of interfacial agents. A microstructure analysis showed that the filling effect and high moisture content of interfacial agents counteracted the negative impact of interval time on the width of the interface between layers and the porosity of ultra-high toughness cementitious composite under 3D-printed technology, which can enhance the interlayer bonding. These results can promote the application of ultra-high toughness cementitious composite under 3D-printed technology in additive manufacturing.