Variation Of Flexural Strength Research Articles

Effect of thermocycling on flexural strength of dental CAD/CAM ceramics of variable thicknesses and structures: an in vitro study

Background This study examined the effect of thermocycling on the flexural strength properties of four CAD/CAM ceramic materials at different thicknesses. Methods Four CAD/CAM ceramics of different types: advanced lithium disilicate (ALD), zirconia-reinforced lithium silicate (ZLS) lithium disilicate (LD), and leucite reinforced (LE), and at three varying thicknesses 0.5, 1.0 and 1.5 mm were examined. After subjecting all specimens to 5000 thermomechanical cycles, flexural strength was determined using a universal testing apparatus. Scanning electron microscopy (SEM) was employed for analysis. Two factorial ANOVA models assessed the association of different factors (ceramic type and thickness) with flexural strength and elastic modulus. The 95% confidence intervals (CIs) and adjusted means were computed. A p-value < 0.05 was designated significant. Results ZLS exhibited the highest flexural strength at 1.5 mm thickness, while LD showed the highest Young’s modulus of elasticity. The lowest flexural strength was observed in the 0.5 mm thickness group. There were notable variations in flexural strength across all ceramic materials, with the highest adjusted mean strength in the ZLS group, ALD, LD, and LE, respectively. Additionally, significant differences were noted in ceramic thickness, with 1.5 mm thickness showing the highest strength and 0.5 mm thickness the lowest. Conclusions Ceramic material thickness significantly impacts flexural strength, with 1.5 mm thickness deemed suitable for posterior restorations. Ceramic materials with zirconia fillers or matrix demonstrated higher flexural strength than other ceramics.

Exploring Flexural Strength Variation in Polymeric Materials for Provisional Fixed Prosthetic Structures: Comparative Analysis with and without Reinforcement through Laboratory Experimentation and Statistical Evaluation

Provisional fixed partial dentures represent a critical phase in dental treatment, necessitating heightened mechanical durability, particularly in comprehensive and extended treatment plans. Strengthening these structures with various reinforcing materials offers a method to enhance their resilience. Utilizing a three-point testing methodology on standardized trial specimens allows for a comparative assessment of various materials and reinforcement techniques for pre-prosthetic applications. This study aims to validate and assess the significance of integrating different reinforcing materials into standardized test bodies. The study focuses on test specimens comprising three types of unreinforced laboratory and clinical polymers for provisional constructions (n = 6)—heat-cured PMMA (Superpont C+B, Spofa Dental, Czech Republic), CAD-CAM prefabricated PMMA (DD temp MED, Dental Direkt, Germany), CAD-CAM printing resin (Temporary CB Resin, FormLabs, USA), self-polymerizing PEMA (DENTALON plus, Kulzer, Germany), light-polymerizing composite (Revotek LC, GC, Japan), and dual-polymerizing composite (TempSpan, Pentron, USA). Additionally, laboratory polymers are evaluated in groups with five types of reinforcing filaments (n = 15)—Glass Fiber (Fiber Splint One-Layer, Polydentia, Switzerland), Polyethylene thread (Ribbond Regular 4.0 mm, Ribbond Inc., USA), triple-stranded chrome-cobalt wire for splinting 015″ (Leone S.p.a., Italy), Aesthetic ligature wire 012″ (Leone S.p.a., Italy), and Glass Fiber coated with light-cured composite 8.5 × 0.2 mm (Interlig, Angelus, Brazil). Analysis of the data using Generalized Linear Models (GLMs) reveals that the experimental bodies, produced via the subtractive digital method using PMMA (DD temp MED, Dental Direkt GmbH, Germany) as the polymer and glass filaments as the reinforcement, exhibit superior mechanical properties, particularly when pre-wetted with Interlig liquid composite (Angelus, Brazil).

Influence of polycarbosilane composition on the properties of SiC/SiC composite fabricated by precursor infiltration and pyrolysis process

AbstractA series of SiC/SiC composites were fabricated through the precursor infiltration and pyrolysis (PIP) process, using solid polycarbosilane (PCS) and liquid vinyl perhydrogen PCS (VHPCS) solutions as impregnating agents. The physicochemical characteristics of the SiC matrices derived from PCS and VHPCS were investigated and compared. The impact of the PCS composition on the microstructure, density, flexural strength, and modulus of the resulting SiC/SiC composites was also examined. As the VHPCS content increased to 60 wt%, the flexural strength of the composites gradually rose to a peak of 490.9 MPa before decreasing as the VHPCS proportion continued to increase. Meanwhile, the flexural modulus increased continually with the introduction of VHPCS. A possible mechanism is proposed to explain the different variations in flexural strength and modulus, taking into account the ceramic toughening principle and the distinct properties of PCS and VHPCS.

Comparative analysis of self-cure and dual cure-dental composites on their physico-mechanical behaviour.

Clinical practitioners may have become familiar with the rapid transformation of dental composites. However, they may not scientifically understand the factors influencing the mechanical and physical properties. Scientific knowledge of filler-resin interaction can significantly improve clinical understanding of resin composites. Several independent studies have examined the mechanical and physico-mechanical properties of dental resin composites; however, no comprehensive study has examined the influence of fillers and resin materials on the physico-mechanical properties of both self-cure and dual-cure composites. This study performed investigations on the physico-mechanical behaviour of four commercially available dual-cure dental composites (Bioactive, Fill Up!, Surefil One, Cention N) and two commercially available self-cure dental composites (Stela Capsule and Stela Automix). Test specimens for flexural and compressive strength, microhardness, fracture toughness, and hydrolytic behaviour were prepared and tested as per respective standards. The data sets were statistically analysed using one-way ANOVA and Tukey's post-hoc comparison. There was a substantial variation in flexural strength and modulus values in this study, ranging from 32.0 to 113.4 MPa and 2.36 to 12.07 GPa, respectively. Similarly, there were significant differences in compressive strength between the materials in this study, ranging from 119.3 to 223.5 MPa. The highest fracture toughness value was found to be 1.41 MPa.m0.5, while the lowest value was 0.43 MPa.m0.5. Variations in surface microhardness were significant (24.11-68.0 N/mm2), which correlated with the filler content. Water sorption and solubility demonstrated high variations among materials, with Surefil One exceeding ISO 4049 thresholds significantly. A linear correlation can be established between surface microhardness (HV) and flexural and compressive moduli, as well as filler content (wt.%). However, both flexural and compressive strengths are impacted by the resin's constituent monomers and the resin-filler matrix's cross-linking capability. Additionally, factors such as filler size, shape, and the cross-linking ability of the resin-filler matrix play a crucial role in fracture toughness and the propagation of cracks within the restoration. Also, resin monomers and filler particle size affect the hydrolytic degradation characteristics of composites, which can also affect their mechanical properties. © 2023 Australian Dental Association.

Residual mechanical properties of recycled aggregate concrete at elevated temperatures

AbstractThis research examines the residual mechanical properties of normal and recycled aggregate concrete when subjected to elevated temperatures. The concrete specimens containing recycled aggregate (0%, 50%, 75%, and 100%) were exposed to different temperatures (25, 200, 400, and 600°C) in a muffle furnace at a heating rate of 10°C/min. The variations in flexural strength, compressive strength, and density were then tested according to ASTM standards. Findings from this investigation indicate that the degradation in the mechanical strength of concrete does not seem to be significantly affected by the increase in the percentage of recycled aggregates. However, a significant and linear decrease in the density was observed at 400°C with an increase in the percentage of recycled aggregates. The degradation of the compressive and flexural strengths of recycled aggregate concrete with increasing temperatures obtained from the experimental analysis was compared with the analytical predictions provided by Eurocode 2. Moreover, simplified equations have been proposed to estimate the degradation of the mechanical properties of recycled aggregate concrete at higher temperatures. The incorporation of recycled aggregates into concrete resulted in satisfactory residual performance.

Mechanical and Shape Recovery Characterization of MWCNTs/HNTs-Reinforced Thermal-Responsive Shape-Memory Polymer Nanocomposites.

Mechanical and shape recovery characteristics of thermal-responsive shape-memory polyurethane (SMPU) reinforced with two types of reinforcements, multiwalled carbon nanotubes (MWCNTs) and halloysite nanotubes (HNTs), were studied in the present research work. Three weight percentages of reinforcement (0, 0.5 and 1%) in the SMPU matrix were considered, and the required composite specimens were obtained through injection moulding. Tensile, flexural, impact and shape recovery behaviours were studied experimentally. Further, flexural tests were performed for multiple cycles to understand the specimens' flexural strength variation after shape recovery. The concentration of both reinforcements (MWCNTs and HNTs) considered in the present study significantly improved mechanical properties and shape recovery.

Modeling the flexural strength of steel fibre reinforced concrete

<abstract> <p>Industrial applications of fibre-reinforced concrete (FRC) in structures require extensive experimental and analytical investigations of the FRC material properties. For design purposes and applications involving the flexural loading of the member, it is essential to have a predictive model for the flexural strength of the FRC material. In the present paper, a fracture mechanics approach based on Bridged Crack Model (BCM) is used to predict the flexural strength of steel fibre-reinforced concrete (SFRC) beams. The model assumes a quadratic tension-softening relationship (σ-δ) governing the bridging action of the steel fibres and a linear profile of the propagating crack. The proposed tension-softening relationship is considered valid for a wide range of fibre-reinforced concrete materials based on the knowledge of either the material micromechanical parameters (such as fibre volume fraction, fibre/matrix bond strength, fibre length, and fibre tensile strength) or an actual experimentally-measured σ-δ relationship. The flexural strength model thus obtained allows the prediction of the flexural strength of SFRC and study the variation of the latter as a function of the micromechanical parameters. An experimental program involving the flexural testing of 13 SFRC prism series was carried out to verify the prediction of the proposed model. The SFRC mixes incorporated two types of steel fibres (straight-end and hooked-end), four different concrete compressive strengths (40, 50, 60, and 70 MPa), three different fibre volume fractions (1, 1.5, and 2%), and three specimen depths (100, 150, and 200 mm). The experimental results were compared to the predictions of the proposed flexural strength model, and a reasonable agreement between the two has been observed. The model provided a useful physical explanation for the observed variation of flexural strength as a function of the test variables investigated in this study.</p> </abstract>

Mechanical Characterization of Filler Modified ABS 3D Printed Composites Made via Fused Filament Fabrication

Rapid prototyping (also known as additive manufacturing, AM) is a quickly developing process with increasing new applications in a large variety of industrial sectors (i.e., aerospace, automotive, medical, among others.) However, despite the great advantage of a decoupled price to part complexity of an AM fabricated structure, the material properties (largely governed by filament material and printing parameters) still present a significant limiting factor. In this context, the development of new filament materials for a wider range of applications has great potential. In this study, the influence of micro-scale filler reinforcement (powders), both natural (curauá) and synthetic (glass fibre), in the fabrication of an Acrylonitrile Butadiene Styrene (ABS) filament was evaluated. The filler was controlled by weight fraction (~1%) and the filament was fabricated via extrusion. A commercially available 3D printer was used to print tensile and flexural specimens for mechanical characterization as per ASTM standards. The fracture morphology was analysed after tensile testing via optical microscopy in order to evaluate the effect of the fillers on the material deposition and void formation. No significant variation in the tensile properties was reported, except for the strain at failure, while more significant flexural strength variation was observed as a function of filler material. The fillers presented a significant effect on the void density of the fractured surface. It was demonstrated that this simple fabrication technique can generate novel filament materials that may enhance the mechanical properties or widen the range of application (e.g., faster decomposition times in nature for single-use plastics due to the hydrophilic nature of the natural filler and lower water absorption of the hydrophobic synthetic filler for marine environment applications).

Reconsidering the strength of concrete pavements

ABSTRACT Concrete pavements develop cracks with the accumulation of fatigue damage caused by the combined effect of vehicular and environmental loadings. In Mechanistic-Empirical (ME) design, the ratio of stresses to some measure of strength is used to evaluate incremental damage, which is then related to cracking. Typically, this measure is the Modulus of Rupture (MOR) of a beam made of the same material. The flexural strength is also known to vary with the thickness of the beam. However, the variation of flexural strength due the presence of eigenstresses from temperature or moisture distributions has not received sufficient attention. A non-linear fracture mechanics model demonstrated that the thickness-adjusted flexural strength can also be used for characterising the maximum elastic stress under a linear temperature distribution. However, under a non-linear temperature distribution, the material may sustain a higher or lower maximum elastic stress than the flexural strength. To model this, a practical analytical expression for the apparent flexural strength was derived and showed excellent agreement with numerical simulations as well as with a model based on equivalent elastic deformation energy. The model was used to show that the fatigue capacity under a typical axle load varies with various non-linear temperature distributions.

Structural Design Variations in Beetle Elytra

AbstractBeetles typically use their protective wing coverings or elytra to shield their membranous hindwings from the environment. Elytra in some terrestrial species have evolved a greater protective role capable of shielding the organism from powerful antagonistic predators. The structure–function relationships of these biological composites identify how architectural and chemical variations of the cuticle are tuned to create light‐weight, impact resistant composites. Specifically, the elytral structures of a tree dwelling beetle capable of flight, Trypoxylus dichotomus, and a terrestrial beetle incapable of flight, Phloeodes diabolicus, are compared to understand how their varied environmental needs forged the elytra to facilitate fight or resist fatal predator strikes. Mechanical and microstructural analysis reveals P. diabolicus has a harder, stiffer elytra that incorporate through‐thickness fibers to resist greater mechanical stresses imposed by bending and puncture. Conversely, the elytra of T. dichotomus have a compliant structure with large voids that facilitates localized deformation. Variations in flexural strength and puncture resistance remain attributed to P. diabolicus possessing a thicker cuticle with a greater degree of cross‐linking and an increased amount of endocuticular layers. These findings may provide useful insight into the design and manufacturing of composite materials for use in light‐weight or energy‐absorbing applications.

Influence of time and hydration (ageing) on flexural strength of Yttrium stabilized Zirconia polycrystals (Y-TZP) fabricated with different CAD-CAM Systems.

Objectives:To evaluate the effect of time and hydration (ageing) on flexural strength of yttrium-stabilized zirconia polycrystals (Y-TZP) zirconia fabricated from three different materials.Methods:This in-vitro study was performed from June to September 2019. Y-TZP bars, measuring 2 x 3 x 20 mm were prepared and sintered from three different materials, Group-1: LAVA™ Zirconia (3M ESPE, US) (control) Group-2: Vita In-Ceram YZ (VITA, Germany) and Group-3: Aadva™ Zirconia (Zr) (GC Advanced technologies Inc.). 30 zirconia bars per group were prepared using sectioning of blocks with isomet saw. Followed by sintering in furnaces for recommended temperature cycles. One side of bars were polished and beveled for flexural testing. Groups of specimens were divided into subgroups of 3 (n=10) based on the ageing (distilled water in the incubator at 37ºC) durations (48 Hrs and two and half years). Ten specimens in each material groups were not aged (controls). Samples were exposed to a static force in a three-point bend test using a universal instron-testing machine until fracture. Scanning electron microscopic assessment was performed for fractured specimens for ageing. Data was analyzed using ANOVA and Tukey post hoc test.Results:The mean flexural strength at baseline for Group-1: LAVA™ Zirconia, group (632.7 ± 136.5 MPa) 2: Vita In-Ceram YZ (1036.3 ± 229.6 MPa), and Group-3: Aadva™ Zirconia (1171.3 ± 266.3 MPa) were significantly different. Group-2 and Group-3 specimens showed higher strength compared to Group-1 specimens, irrespective of the ageing duration (p<0.05). Analysis of pooled data for flexural strength for materials by aging period (baseline, after 48 hours and after 2 and ½ years) showed that there was significant reduction of strength with increasing duration (p<0.05).Conclusions:Y-TZP showed variations in flexural strength depending on the material type. Ageing duration exhibited significant influence on the flexural strength of Y-TZP when comparing no ageing to two and half years. Vita In-Ceram YZ and Aadva Zirconia (Zr) showed higher and clinically acceptable flexural strength outcomes.

Multimaterial laminated composites: An assessment of effect of stacking sequence on flexural response

Abstract Various industries are aiming to develop low weight-high performance materials especially in structural and automotive applications. Fiber metal laminated composite materials are the one such material which meets the global requirement and are in a position of replacing current material. Metallic and composite material combinations owe to enhance the performance. In present research work, two types of tin sheet/glass fiber reinforced laminated composites were prepared such as Sn-G4-Sn and Sn-G2-Sn-G2-Sn. The current research work reveals the effect of stacking sequence on the mechanical behaviour of tin sheet/glass fiber laminated composites. The flexural properties of the laminated composites have been evaluated. The results revealed that there is no significant variation in flexural strength; however, Sn-G2-Sn-G2-Sn laminated composite exhibited superior performance in flexural modulus with an improvement of 52.97%. Additionally, to understand the various failure modes in the laminated composites post failure analysis was carried out using stereo microscope. Macrographic/Post failure analysis revealed that delamination between the interface of the Sn and composite layer was dominant in experimented laminated composites.

High-temperature Mechanical Properties and Their Influence Mechanisms of ZrC-Modified C-SiC Ceramic Matrix Composites up to 1600 °C.

In order to understand the influence of the mechanisms of ZrC nanoparticles on the high-temperature mechanical properties of C-SiC ceramic matrix composites, the mechanical properties were measured from room temperature (RT) to 1600 °C under vacuum. The microstructures features were characterized by scanning electron microscopy. In comparison with the composites without ZrC nanoparticles, the ZrC-modified composite presented better mechanical properties at all temperatures, indicating that the mechanical properties could be improved by the ZrC nanoparticles. The ZrC nanoparticles could reduce the residual silicon and improve the microstructure integrity of composite. Furthermore, the variation of flexural strength and the flexural modulus showed an asynchronous trend with the increase of temperature. The flexural strength reached the maximum value at 1200 °C, but the highest elastic modulus was obtained at 800 °C. The strength increase was ascribed to the decrease of the thermally-induced residual stresses. The degradation of mechanical properties was observed at 1600 °C because of the microstructure deterioration and the formation of strongly bonded fiber–matrix interface. Therefore, it is concluded that the high temperature mechanical properties under vacuum were related to the consisting phase, the matrix microstructure, and the thermally-induced residual stresses.

The Ball-on-Three-Ball (B3B) Test – Application to Cement Paste and Mortar

Abstract While originally used for ceramics, the ball-on-three-ball (B3B) test has shown value for use with cementitious materials. The B3B test uses disk-shaped samples that can be sectioned from a cylinder, which allows a large number of samples to be tested to provide information on statistical repeatability. Additionally, this test is also well suited for use in some cement paste degradation studies. In this research, cement paste and mortar samples made with standard ASTM sand or natural sand were tested using the B3B test. The results showed that the B3B test has less than 10 % variation in flexural strength for cement paste and mortar. Data analysis using statistical Weibull theory indicated that the B3B flexural strength is typically lower than four-point bending flexural strength; however, this can be explained by size effect considerations. Recommended testing procedures were given.

Development of a sustainable coating and repair material to prevent bio-corrosion in concrete sewer and waste-water pipes

Concrete biogenic corrosion (bio-corrosion) in wastewater pipes occurs mainly because of the diffusion of aggressive solutions and in situ production of sulfuric acid by sulfur-oxidizing microorganisms. The prevention of concrete bio-corrosion usually requires modification of the concrete mix or the application of a corrosion-resistant, chemical/antimicrobial-coating layer on the inner surface of the pipe to inhibit biological activity and provide a protective layer between the concrete surface and corrosive solution. However, the short bio-resistant lifetime due to undesired leaching of biocides to the surrounding environment coupled with the coating's poor acid-resistant properties have increased the requisite for safe, more efficient, environmentally friendly and long-lasting alternatives.In this paper, three broad families of coating materials were investigated. These comprised Portland cement-based, geopolymer-based and geopolymer magnesium phosphate-based coatings. These three coatings carried in separate formulations, intermixed Zinc particle and Zinc-doped clay particles. These were in turn compared with ordinary cement-based coatings without Zinc or Zinc-doped clay. For the Zinc-doped clay particles, sodium-bentonite were impregnated with zinc ions to create a biocide-loaded carrier. The coatings’ chemical stability and resistance to biogenic corrosion were investigated by testing samples in an accelerated bio-corrosion chamber designed and developed by the authors. Variations in flexural strength were studied to evaluate the properties and performance of the coated samples after corrosion. Results show that the developed coating materials have significantly superior resistance to biogenic corrosion compared to ordinary cement-based coatings.

Influence of Areca Nut Nano Filler on Mechanical and Tribological Properties of Coir Fiber Reinforced Epoxy Based Polymer Composite

The present study is aimed at investigating the effect of incorporating arecanut nano filler on the tribological behaviour of coir reinforced epoxy based polymer matrix composite. Areca nut nano filler is produced by grinding followed by ball milling. Particle size analyzer confirmed the size of nano fillers obtained are in the range of 20-100 nm. Composites with different weight percentage of nano filler (0%, 5%, and 10%) were studied for their mechanical and tribological behaviour using pin on disc rig. Tensile, Flexural, Interlaminar shear and impact tests are carried out on the proposed composite. Taguchi’s technique is used for analysing effect of various factors on the tribological behaviour of the composite. The results showed that inclusion of arecanut nano filler enhanced the microhardness of the composite, with inclusion of arecanut filler the tensile strength increased up to 5 %, later there is a decrease in tensile strength. Flexural strength significantly increases with increase in filler percentage from 0% to 5%, but the variation of flexural strength from 5% to 10% is negligible. Inclusion of filler has negligible effect on the interlaminar shear strength of composites. Impact strength and wear resistance of the composite is enhanced with incorporation of filler.

The significance of concrete slab flexural strength inference variation based on its compression strength characteristics in apron pavement analysis and design

Rigid pavement of apron in the airport is a complex structure which is designed based on the sense of balance of sub-grade strength, pavement aggregates, applied load characteristics, and climate. Various sub-grade condition and concrete slab flexural strength values results on the pavement design thickness that have a direct impact on the cost construction. In this study, the rigid pavement design of an apron with various sub-grade condition and concrete flexural strength values are presented. As a reference, the Federal Aviation and Administration (FAA) method is used. Dynamic Cone Penetration (DCP) test value is used to estimate California Bearing Ratio (CBR) values to determine the sub-grade reaction modulus (k). The flexural strength of concrete slab analyzed by several empirical models with constant values range of 0.72-0.9. The pavement structure analysis conducted by FAARFIELD. The CBR values from DCP’s test vary between 6-10% which equal to k values between 31.4-46.8 MN/m3. Concrete slab flexural strength of 4.6 MPa results on the concrete slab thickness of 550-510 mm. Based on k value of 46.8 MN/m3 and K400 concrete strength, the calculated flexural strength varies between 4.15-5.17 MPa and the concrete slab thickness is 570-540 cm. The inference variation of flexural strength based on the same value of concrete compression strength characteristics will produce different concrete slab thickness. The concrete slab thickness tends to increase with the smaller values of inference of flexural strength.

Effect of finger joining on flexural strength of commonly used timber species in Sri Lanka

The variation of flexural strength of seven timber species mainly used for furniture industry in Sri Lanka was studied. Modulus of Rupture (MOR) and Modulus of Elasticity (MOE) were measured without finger joint and with finger joint specimens of timber species. Finger joint technique is used to eliminate wood defects which weaken the strength of sawn wood plank and used. This paper gives comparison study of finger jointed and un-jointed seven wood species, tested under three point bending test. BS 373: 1957 and BS EN 15497:2014 were used as standards for tests. Vertical finger joint orientation and 13 mm finger joint length were used in this study. The tests for mechanical properties were performed by using a Universal Testing Machine (UTM 100 PC). The parameters were analyzed by using ANOVA and means were separated by Duncan's Multiple Range Test at 0.05 significant levels in SAS. It was found that control (un-jointed solid wood) samples gave the highest flexural strength than finger-jointed specimens and it was also observed that Kumbuk timber species was showed the highest MOE in 13 mm finger-jointed specimens comparing control specimens. The highest flexural strength loss percentage was obtained from Satin species. The MOE of finger-jointed Kumbuk was higher than clear Kumbuk specimens and least strength loss percentage of MOR (46.08 %) was obtained from Mahogany species.

Studies of the relationship between rice stem composition and lodging resistance

AbstractPlant height and lodging resistance can affect rice yield significantly, but these traits have always conflicted in crop cultivation and breeding. The current study aimed to establish a rapid and accurate plant type evaluation mechanism to provide a basis for breeding tall but lodging-resistant super rice varieties. A comprehensive approach integrating plant anatomy and histochemistry was used to investigate variations in flexural strength (a material property, defined as the stress in a material just before it yields in a flexure test) of the rice stem and the lodging index of 15 rice accessions at different growth stages to understand trends in these parameters and the potential factors influencing them. Rice stem anatomical structure was observed and the lignin content the cell wall was determined at different developmental stages. Three rice lodging evaluation models were established using correlation analysis, multivariate regression and artificial radial basis function (RBF) neural network analysis, and the results were compared to identify the most suitable model for predicting optimal rice plant types. Among the three evaluation methods, the mean residual and relative prediction errors were lowest using the RBF network, indicating that it was highly accurate and robust and could be used to establish a mathematical model of the morphological characteristics and lodging resistance of rice to identify optimal varieties.

Flexural strength of glass using Weibull statistic analysis

Purpose: The aim of the study is to measure the flexural strength of glass by proposed experimental procedures. In addition, step-by-step guidelines for the strength data analysis using a two-parameter Weibull distribution are given. Design/methodology/approach: Twelve glass samples of three series were tested by three-point bending with horizontal ‘3PB(H)’ and vertical ‘3PB(V)’ orientation of samples. A two-parameter Weibull distribution was applied as an appropriate model to describe three strength data sets for glass. Findings: The experiments performed on nominally identical glass specimens revealed a wide range of flexural strength values, from 39.77 MPa to 171.71 MPa at a loading rate of not more than 1.05 MPa/s. 3PB(V) samples with vertical orientation demonstrated the flexural strength similar to that of 3PB(H) samples with horizontal orientation. The Weibull modulus, which is the measure of flexural strength variation, was between 2.04 and 5.23 at the coefficient of determination R2 greater than 90% for all series. The characteristic values of the glass strength, corresponding to the 5% fractile value, in accordance with the test evaluation procedure were 23.71 MPa, 31.98 MPa, 53.43 MPa for the first, the second and the third test series, respectively. Research limitations/implications: The maximum flexural strength of glass highly depends on the surface condition, and therefore the strength of the glass of different batches is variable whatever the case may be. For the guaranteed strength of glass used for structural purposes it is necessary to conduct strength tests of the glass from each batch under conditions that closely correspond to actual operating conditions. Practical implications: The obtained strength data is needed for designing glass load bearing constructions subjected to actual operating conditions (e.g. multilayered glass plates working on bending under static loading). Originality/value: A comprehensive overview of the existing methods for glass strength testing was presented. The features of the used flexural tests and the statistical analysis of the measured strength data were described. The results may be of a particular interest to the specialists in the modern design of load bearing glass constructions.