Bending Strength Tests Research Articles

Optimizing mechanical properties and pioneering biodegradable polymer blends for superior energy-absorbing structures used in sport helmets

Replacing elements made of conventional plastics (like polystyrene) with biodegradable substitutes is part of the trend of sustainable development and waste reduction. The manuscript covers issues related to the design, manufacturing and testing of sports helmet protective inserts made of biodegradable material. The FEM numerical simulations carried out by the authors allowed to determine the optimal desirable mechanical properties (Re = 8.5–65 MPa, E = 500–8000 MPa for 30 × 30 mm inserts; Re = 10.5–60 MPa, E = 500–7500 MPa for 48 × 48 mm inserts; Re = 13–95 MPa, E = 400–8500 MPa for 55 × 55 mm inserts) and geometric parameters (wall thickness equal to 0.2–0.5 mm, height of 20 mm), ensuring the formation of a plastic fold, which is the most effective energy-absorbing mechanism. The conducted quasi-static compression, bending and dynamic tensile strength tests allowed to determine blends with appropriate proportions of durable PLA with more plastic PBAT, PBS and TPS that meet the established criteria: PLA50PBAT50, PLA30PBAT70 and PLA30TPS70.

Effects of Growth and Treatment Conditions on the Quality of Norway Spruce (Picea abies L.) Sawn Timber

A study was conducted to improve the effectiveness of silvicultural production of structural sawn timber from softwoods. It intends to explore prediction methods for mechanical timber quality. The study material was obtained from six stands divided into age groups of approximately 40- and 80-year-old trees (examining the influence of age). The stands were differentiated by their applied thinning system of thinning from below or above (examining the influence of the thinning system). Resulting from these different levels of data, i.e., stand parameters, tree anatomy, and visual board properties are examined and analyzed in ordinal logistic models and linear mixed models. Visual board properties were discerned by means of the German standard for visual grading of sawn timber. The mechanical board properties were measured in on-edge bending strength tests and allocated into strength classes, which were modeled in dependence of visual characteristics and forestry conditions. The evaluation of mechanical properties attributed a significant loss of timber quality to short rotation periods, non-ideal water supply, and a single-tree management system. The prediction capabilities of models based on site and tree characteristics were on par with the accuracy of visual grading. Management adaptations by intense thinning from above can lead to a significant decline in Norway spruce (Picea abies L.) timber quality when site factors coincide. Particular care should be taken in the management of locations with high yield potential. Non-destructive evaluation based on site characteristics combined with terrestrial laser scan data of tree characteristics has potential as a pregrading method.

Strengthening Polymer Concrete with Carbon and Basalt Fibres

To date, composite materials, such as polymer concrete, have found wide application in various industries due to their unique properties combining high strength, resistance to aggressive media and durability. Improving the performance characteristics of polymer concrete is an important task aimed at expanding the areas of its application. One of the promising methods of increasing the strength of this material is the use of various fillers. In this paper, the effect of fillers, based on carbon and basalt fibres, on the mechanical properties of polymer concrete was investigated. The polymer concrete was made of the following components: rubble stone, sand, quartz flour and polyester resin. During the experimental work, the amount of carbon and basalt fibres in the polymer concrete mixture varied from 0 to 6%. Bending and compressive strength tests showed that the addition of carbon and basalt fibres increased these properties. The highest bending and compressive strengths were achieved when carbon fibre contents were up to 1.5%, while basalt fibres provided the highest strengths in the case of around 2%. These results confirmed that carbon fibres had a higher efficiency in strengthening polymer concrete compared to that of basalt fibres. This could be explained by the fact that carbon fibres had a higher tensile strength and modulus of elasticity, which allowed them to better redistribute loads within the composite material. The fibre length for carbon fibre, which gave the maximum increase in properties, was 10–15 mm. For basalt fibre, the maximum bending strength was reached at 20 mm and compressive strength at 10 mm. Increasing the content of carbon fibre above 2% and basalt fibre above 1.5% did not give further increase in mechanical properties. In conclusion, it could be stated that the use of carbon fibres as fillers offered significant advantages in strengthening polymer concrete, opening up opportunities for its use in more demanding conditions and in a wider range of industrial applications.

Study on Mechanical Properties of Moso Bamboo in Jian'ou City, Fujian Province, China

The original bamboo material of 3 to 4-year-old moso bamboo in Jian'o City, Fujian Province, was used as the research object. Study the change of mechanical properties such as axial compressive strength, bending strength, tensile strength, shear strength, and hardness test. The main work and results of this paper include:Forty-five longitudinal compression specimens on moso bamboo tubes were tested to investigate the effects of different sizes and bamboo knots on the axial compressive strength of the moso bamboo tubes. The mean tensile strength of moso bamboo was found to be 165.13 N/㎟. A total of 27 shear specimens of 5cm moso bamboo tubes were tested, and their average shear strength was 2.61Mpa; he average flexural strength of moso bamboo was 172.48N/㎟. The hardness of moso bamboo specimens was tested using the Janka hardness method. The hardness of each part of Moso bamboo was significantly different.Comparing the mechanical properties of moso bamboo with other wood timber, moso bamboo showed better mechanical properties, the research hoped to provide a theoretical basis and scientific evidence for a comprehensive understanding of the complex mechanical properties of Fujian moso bamboo and the use of moso bamboo in high value-added applications.

Development of 1400°C(2552°F) class Ceramic Matrix Composite Turbine Shroud and Demonstration Test with JAXA F7 Aircraft Engine

Abstract The Authors developed 1400°C(2552°F) class CMC material system which consist of SiC fibers and SiC matrix and ytterbium silicate base matrix, aiming for higher temperature capability. Then they designed and manufactured high pressure turbine shrouds for aircraft engines using that 1400°C class material system, and they conducted strength tests and thermal cycle tests for turbine shroud components. After that they conducted engine tests for the CMC turbine shrouds demonstration in the actual engine environment jointly with the Japan Aerospace Exploration Agency (JAXA) in 2021. The engine test was conducted for over 75 hours including over 35 hour hot time. After the test teardown inspection was conducted. No spallation of EBC, no recession and no wear on CMC turbine shrouds were found. As the result of the microstructure observation for cut faces of CMC turbine shrouds, no oxidation in SiC fibers, no chemical reaction in matrix, and no microcrack in matrix were found, but, some oxidation in fiber interface coating and microcrack in EBC were found. Bending strength tests with specimens cut out from CMC turbine shrouds were conducted in order to survey the degradation of material. As the result of bending test, the strength of the specimens cut out from engine tested shrouds were equivalent to the strength of the specimens cut out from unused shrouds. The CMC turbine shrouds after engine test were determined to be serviceable, therefore the developed 1400°C class CMC shrouds was proven to be sound in an actual engine environment.

Condition Monitoring System: A Flexible Hybrid Electronics Approach for Sealed Container Applications

A comparative study is presented between two advanced flexible hybrid electronics (FHE) systems designed for monitoring temperature within storage containers across various industries, including food, pharmaceuticals, agriculture, automotive, and defense. The first system, a copper-flex system (CFS), employs an 88.9 µm polyimide substrate with 35 µm thick copper traces, coated with a 12.5 µm polyimide solder mask. The second system, a printed-flex system (PFS), utilizes a 127 µm polyimide substrate with high-temperature resistance and tensile strength. Conductive silver ink was screen-printed on the PFS substrate, and electronic components including a temperature sensor were attached. Functional and reliability tests were performed to check the accuracy and durability of the temperature sensor. Further, environmental and mechanical characterizations including moisture and insulation resistance, corrosion, elongation, bending, and terminal bond strength tests were performed based on ASTM and IPC-TM650 standards. Moisture and insulation resistance test on the PFS test coupons without a coating layer indicated stable resistance of approximately 18 MΩ, while permanent color change indicated oxidation of copper on uncoated CFS test coupons. After 72 hours of corrosion test, both the CFS and PFS “meander line” test coupons covered with polyimide showed negligible change in weight and resistance, approximately 0.35%. A Young’s modulus of 7.17 GPa and 2.6 GPa was calculated from the elongation test for the CFS and PFS, respectively. Bending tests on PFS revealed negligible average resistance change (0.1%) during 180° bending cycles, while no impact was recorded on the CFS. During the terminal bond strength test, soldered wires detached from the CFS test coupons at an average force of 43 N, while it was 3.8 N on the PFS test coupons. Both systems with polyimide coating layer demonstrate robustness and reliability for diverse applications in various industries.

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.

An Approach to Improve Specimen Processing for the Flexural Strength Testing of Zirconia.

Measuring the flexural strength of restorative materials such as zirconia is crucial for providing proper indications for clinical applications and predicting performance. Great variations in specimen preparation for flexural strength measurements exist among laboratories. The aim was to evaluate how the processing method, surface treatment, and test method of the specimens affect the flexural strength of zirconia. Zirconia specimens (VITA YZ HT) (n = 270) were processed using CAD/CAM or were conventionally milled with three different surface treatments (machined, ground, polished) and were measured with three-point bending (non-chamfered/chamfered) or biaxial flexural strength test. Weibull statistics were conducted. The mean flexural strength values ranged from 612 MPa (conventional, machined, three-point bending non-chamfered) to 1143 MPa (CAD/CAM, polished, biaxial flexural strength). The highest reliability is achieved when specimens are prepared using thoroughly controllable processing with CAD/CAM and subsequently polished. Higher strength values are achieved with the biaxial flexural strength test method because the stress concentration in relation to the effective volume is smaller. Polishing reduces surface microcracks and therefore increases the strength values.

Preparation of fused silica glass micropatterns via gel method using quartz fiber as reinforcer

The preparation of fused silica glass with microstructural patterns has attracted considerable interest, and the process chain of using nano-silica powders mixed with organic polymers to prepare composites for molding, degreasing, and sintering provides a good solution. However, the potential negative effects of organic residues cannot be avoided. In this study, a pattern stencil replication method with silica gel using high-purity quartz fibers as reinforcement is proposed for preparing micropatterned fused silica glass. The microscopic morphology and mechanical properties before and after silica gel drying and the optical properties of fused silica glass obtained by sintering were evaluated via transmission electron microscopy), three-point bending strength test, scanning electron microscopy, X-ray diffraction spectrum analysis, ultraviolet–visible and infrared measurements. The results showed that quartz fiber as a reinforcer could shorten the drying time of the gel and did not degrade the quality of the fused silica glass obtained by sintering. Laser confocal test results showed that microlens arrays were generated by template replication, demonstrating the feasibility of molding fused silica lens arrays with small feature sizes and providing new ideas for the preparation of bulk fused silica glass or micropatterned glass.

Stress – deformation relations of Scotch Pine (Pinus sylvestris L.) under different conditions

In this study, precise samples of Scots pine wood were subjected to bending strength tests in air dry, moisture above LDN and steamed conditions. In the tests, in addition to resistance values, stress and deformation at the elastic limit, II. zone length and total deformation were investigated. As a result of the experiments, it was observed that the materials lost some resistance after the maximum load was reached in LDN and steamed samples, but they continued to carry the load. This situation has led to the need to create two different resistance classes: maximum bending tensile strength and bending fracture resistance. The maximum stress in bending and fracture resistance in bending was found to be highest in air-dried samples, while the lowest was found in steamed samples. In examining the elastic limit resistance and deformations, the highest values were found in air-dried samples, while the lowest values were found in steamed samples. In determining the II. zone length, it was determined that the II. zone length of steamed samples gave the highest value, while air-dried samples gave the lowest value. In determining the total deformations, it was concluded that while the most deformation occurred in the steamed samples, the least deformation occurred in the air-dried samples.

Utilization of Slip Casting Process for Recycling CAD/CAM Dental Zirconia Wastes

This study aimed to find the ideal parameters for shaping waste zirconia powders from dental laboratories using the slip-casting process. Additionally, the qualities of ceramic products created in this manner were evaluated using microstructural characterization and physical-mechanical tests. Various dental laboratories provided the waste CAD/CAM zirconia powder used in the investigation. Wastes in powder form were first calcined. Afterward, an attritor mill was used to grind the grain size until it was usable, following the completion of the grain size distribution analysis. Waste and commercial zirconia powders were combined using various dispersants to create slip-casting slurries. The rheological characteristics of these slurries were then ascertained. By evaluating the rheological properties of slip-casting slurries prepared in this way, the most suitable casting parameters were determined, and ceramic products were formed by slip-casting technique from the slurries to be prepared in accordance with these parameters. The shaped samples were dried and sintered at two different temperatures, 1400-1450°C, and samples were designed for physical, mechanical, and microstructural characterization. The pore percentages, bulk densities, and water absorption of the sintered samples, according to Archimedes’ principle, as well as their strengths, were determined by the three-point bending strength test. Phase analysis was performed with XRD (X-ray diffractometer) microstructure studies with SEM (Scanning Electron Microscopy). It has been concluded that waste zirconia can be used in dental applications.

Synergistic preparation of geopolymer using electrolytic manganese residue, coal slag and granulated blast furnace slag

To improve the utilization rate of industrial solid waste and the sustainable development of geopolymer research and development, this article uses electrolytic manganese residue (EMR), coal slag (CS), and granulated blast furnace slag (GGBS) as raw materials to prepare a new eco-friendly geopolymer cementitious material (GOCM). The mechanical properties, phase composition, and microstructure of GOCM are measured and analyzed using methods such as compressive bending strength test, X-ray diffraction, scanning electron microscopy, mercury intrusion test, and Fourier transform infrared spectroscopy. The effects of material ratio, water cement ratio, and alkali activator content on GOCM are explored. Meantime, the environmental characteristics of GOCM were also investigated through toxicity leaching experiments. Results show that CS improves the flowability and late compressive strength of GOCM, and EMR reduces the setting time of the slurry, the maximum strength of GOCM was observed when the contents of EMR, CS, and GGBS were 25 %, 55 %, and 20 %, the mass fraction of alkaline activator was 14 %, and the W/C was 0.45. and the maximum compressive strength reaches 22.8 MPa. The hydrates in GOCM are composed of flocculent, cluster, block C–S–H gel. The hydrates formed have excellent stabilization effect on heavy metals in raw materials. When the GOCM material ratio is optimal (the contents of EMR, CS, and GGBS were 25 %, 55 %, and 20 %), the leaching concentration of Cd, Cr, and Mn is lower than the limit values (Cd < 0.001 mg/L, Cr < 0.01 mg/L, Mn < 0.05 mg/L) specified in GB/T14848-2017.

Fabrication and optimization process of mechanical properties of MoSi2 composites reinforced by carbon nanotubes (CNT) using Taguchi method

This experimental research aims to produce and study the properties of MoSi2 reinforced with CNT composites using the SPS sintering method. First and before any laboratory operations, using the Minitab 14 software, experimental samples were designed under L16 arrays. Four levels were set for defining parameters, such as the amount of reinforcing phase (CNT), sintering temperature (°C), and holding time (T). XRD, FESEM, density, micro-hardness, bending strength, and fracture toughness tests were used in the study for in-depth investigations. According to the signal-to-noise analysis, the parameter with the greatest influence is the reinforcement rate. Based on the obtained results, the composite with 5 wt% of carbon nanotubes, a sintering temperature of 1300 °C, and a holding time of 10 min was found to have the highest results.

Relationship between mechanical properties and height-diameter ratio of moso bamboo

Systematic tests of longitudinal compression, bending, longitudinal shear, and longitudinal tensile strength of bamboo were conducted to study the variation of mechanical properties and the height-diameter ratio of bamboo. The predictive relations of mechanical properties and height-diameter ratio were fitted by linear regression analysis. The results showed that the mechanical properties of longitudinal compression, bending, longitudinal shear, and longitudinal tensile strength of bamboo increased with the increase of the height-diameter ratio. In this paper, the method of deducing the relationship between mechanical properties and height-diameter ratio of bamboo through the linear fitting relationship between mechanical properties and height-diameter ratio was shown to have high applicability and accuracy for bamboo. This paper has a certain reference value for the evaluation of mechanical properties of bamboo and has a certain practical value for reducing the testing cost.

An HVOF-Sprayed (Cr3C2-NiCr+Co) Composite Coating on Ductile Cast Iron: Microstructure, Mechanical Properties, and Scratch Resistance.

High-velocity oxy-fuel (HVOF) thermally sprayed Cr3C2-NiCr coatings have been shown to be effective in shielding important machinery and equipment components from wear in harsh, high-temperature conditions. In this investigation, the HVOF thermal spray coating technique was used to deposit Cr3C2-NiCr powder with 10% Co particles onto ductile cast iron. The effect of the Co particles on the mechanical, tribological, and microstructure characteristics of a Cr3C2-NiCr/ductile cast iron system was investigated. The microstructure analysis employed various techniques, including light microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Scratch tests were applied to analyze the coating quality and adhesion. The coatings created using the HVOF spray method with Cr3C2-NiCr powders mixed with Co particles exhibited a dense structure containing large Co particles, partially melted, and very fine Cr3C2 particles embedded into the NiCr alloy matrix. Additionally, they possessed high hardness and excellent adhesion to the substrate. The results of bending strength tests were also presented, together with information on the coating's microhardness and fracture toughness. These included an analysis of the cracks and delamination in the Cr3C2-NiCr/ductile cast iron system. It was observed that the addition of Co particles significantly increased the resistance to cracking and wear behavior in the studied system.

Effect of Additives on Heat Hardened Inorganic Solid Foundry Binder

AbstractRenewed interest in inorganic binders for sand molding has also intensified research on different forms of it. In this study, solid inorganic sodium silicate binder was tested with different additives to see how these affected the silica mold quality. The five additives used were: glucose, sucrose, boric acid, aluminum oxide and iron(III)oxide powders. The mold quality was assessed through tests like bending strength, tensile strength, hot distortion, wear resistance, gas evolution and collapsibility tests. In addition, SEM imaging was done on some select mold fracture samples. In the end, a casting trial was carried out followed by a surface roughness and defects analysis. A reduction in mold strength was noticed with glucose and boric acid, while collapsibility was improved by glucose, sucrose and boric acid additives. Casting trials have shown the best surface finish to be obtained with sucrose additive. All the casts in general showed some penetration; however, repeat casts have proven that altering some casting parameters could result in casts with excellent surface finish using solid silicates.

Effect of additive type and amount on structural and mechanical properties of ZrO2/B4C/Al2O3/SiC added Al 1050 based composite structures produced by vacuum infiltration—Comparative study

With this experimental study, ZrO2/B4C/Al2O3/SiC ceramics in different weight ratios were added to 99.5% pure aluminum and composites were produced by vacuum infiltration, which is very rare in the literature. It is aimed to investigate how different ceramics will affect the technical properties of an aluminum composite. First, scanning electron microscope images were taken to examine their microstructures, and energy-dispersive x-ray spectroscopy analyses were performed. In addition, x-ray diffraction analyses of phase structures were performed. Then, the densities of the composite structures were measured. In the last stage of the experiments, hardness measurement, bending strength, and abrasive wear amount tests were carried out to determine the mechanical properties of the composite structures. According to the data obtained, a relatively homogeneous structure was obtained up to 10% of the ceramic particles in the structure. It was observed that thermal damage did not occur in the composite structures and no significant phase changes occurred. The highest infiltration distance was obtained from B4C-reinforced samples, and the lowest infiltration distances were obtained from ZrO2-reinforced samples. Ceramic reinforcement elements have reduced the density values of composite structures. With the increase in the ratio of ceramic reinforcement particles, the hardness values of the composites increased and the flexural strength values decreased. In the abrasive wear tests, the least wear loss was obtained from SiC-reinforced samples and the highest wear loss was obtained from ZrO2-reinforced samples. When the composites were evaluated according to their microstructure and mechanical strength, the best results were obtained with SiC and then Al2O3, B4C, and ZrO2 reinforcements, respectively. It has been concluded that SiC, Al2O3, B4C, and ZrO2 reinforcement elements in Al 1050-based composites produced by vacuum infiltration have a positive effect on most of the mechanical properties and a negative effect on some of them.

Effect of Hydrothermal Treatment on the Mechanical and Microscopic Properties of Moso Bamboo

In this study, moso bamboo was used as a raw material. To increase the plasticity of bamboo to achieve a greater softening effect, the softening method of hydrothermal treatment was used. Hardness and the flexural elastic modulus were used as the evaluation indices, and the crystallinity and main functional groups of the softened bamboo were analysed using X-ray diffraction and Fourier-transform infrared spectroscopy. Combined with the examination of timber colour, micromorphology, bending strength, and nanomechanical tests, our analysis showed the effects of the hydrothermal treatment on bamboo. The results showed that the hardness and flexural moduli of bamboo decreased with the increase in hydrothermal treatment temperature. However, cracking occurred after 3.5 and 4 h of treatment at 180 °C and 190 °C. This indicated that the softening effect was most pronounced when the treatment temperature and time were 180 ℃ and 3 h, respectively. The cellulose crystallinity of bamboo increased and then decreased with the increase in treatment temperature. Cracks were produced in the cell structure, starch locally disappeared, and the hardness and the elasticity modulus of the thin-walled bamboo cells first increased and then decreased with the increase in treatment temperature.

Mechanical Properties of Zirconia Materials with Different Translucency: An In Vitro Study.

To investigate the biaxial flexural strength of zirconia materials with different translucency before and after aging procedures and to evaluate the effects of aging on hardness and surface characteristics. A total of 90 disc-shaped specimens (n = 30 each) were prepared from translucent (Upcera-ST, Upcera Dental), high translucent (Katana HT, Kuraray Noritake), and ultra high translucent (Katana UTML, Kuraray Noritake) zirconia materials to a ø.16 ±1.2 mm thickness. The different translucency discs were then divided into three subgroups; one group was subjected to aging in a chewing simulator (n = 10), one group was aged with thermocycling (n = 10), and one was a control group (n = 10). Biaxial flexural strength, Vickers hardness, and surface characteristics were examined for all discs. The data were analyzed using the Shapiro-Wilk (P = .05), Mann-Whitney U, and Kruskal-Wallis H tests. Fracture strength was determined using biaxial bending strength tests, and Weibull analysis was used to analyze the resulting data. A statistically significant difference was found among zirconia materials with different translucency in terms of fracture strength. On average, fracture strength was highest in the Upcera ST group (1,932.87 MPa) and lowest in the Katana UTML group (1,073.6 MPa; P = .001). The results of Weibull analysis showed a statistically similar distribution for all groups. Aging procedures did not cause significant differences in fracture strength and hardness. The fracture strength of the zirconia materials with different translucency was considered acceptable for intraoral use.

Study on the Ultimate Load Failure Mechanism and Structural Optimization Design of Insulators.

This study aims to enhance the productivity of high-voltage transmission line insulators and their operational safety by investigating their failure mechanisms under ultimate load conditions. Destructive tests were conducted on a specific type of insulator under ultimate load conditions. A high-speed camera was used to document the insulator's failure process and collect strain data from designated points. A simulation model of the insulator was established to predict the effects of ultimate loads. The simulation results identified a maximum first principal stress of 94.549 MPa in the porcelain shell, with stress distribution characteristics resembling a cantilever beam subjected to bending. This implied that the insulator failure occurred when the stress reached the bending strength of the porcelain shell. To validate the simulation's accuracy, bending and tensile strength tests were conducted on the ceramic materials constituting the insulator. The bending strength of the porcelain shell was 100.52 MPa, showing a 5.6% variation from the simulation results, which indicated the reliability of the simulation model. Finally, optimization designs on the design parameters P1 and P2 of the insulator were conducted. The results indicated that setting P1 to 8° and P2 to 90.062 mm decreased the first principal stress of the porcelain shell by 47.6% and Von Mises stress by 31.6% under ultimate load conditions, significantly enhancing the load-bearing capacity. This research contributed to improving the production yield and safety performance of insulators.