Beam Bending Test Research Articles

Report on laboratory tests of sandstone and porphyry for rock fracture analysis

The paper presents the results of mechanical tests of three types of rocks from stone mines in Poland. Compression tests of cubic samples, three-point bending tests of beams, bending of beams with notch and testing of tensile strength using the quasi-Brazilian method were performed. Based on the tests, the compressive strength, tensile strength, Young's modulus, and Poisson's ratios were determined. The stress intensity factor and critical strain energy release rate in mode I were determined from the bending test of the notched beams. The determined values were used as parameters of computer models which are used to verify the authors’ method of predicting the crack propagation in the Abaqus FEA system.

Suitability of Fiber Lengths for Hot Mix Asphalt with Different Nominal Maximum Aggregate Size: A Pilot Experimental Investigation.

Fiber length is a key parameter for the mixture design of basalt fiber-reinforced hot mix asphalt (HMA), which significantly affects the mix performance. To evaluate the suitability of fiber lengths for HMA with different nominal maximum aggregate size (NMAS), basalt fiber with the lengths of 3, 6, 9, 12, and 15 mm were selected for dense graded gradations with different NMASs (namely, SUP-13, SUP-20, and SUP-25), so as to prepare the fiber-reinforced HMA mixtures. Then, the mix performance was evaluated by an indirect tensile asphalt cracking test (IDEAL-CT), a four-point bending beam fatigue test, a wheel tracking test, a uniaxial penetration test, a low temperature bending beam test, and a freeze-thaw splitting test. Based on the performance results, the optimum fiber length for each mix gradation was proposed by the normalization method. The results showed that adding basalt fiber can enhance the comprehensive performance of all three types of HMA to a great extent. Furthermore, fiber length presented remarkable impact on the crack resistance, the fatigue resistance of the HMA, and the low temperature crack resistance, but it had limited influence on the high temperature deformation resistance, and water stability. The optimum fiber length for SUP-13, SUP-20, and SUP-25 was 6, 9, and 12 mm, respectively.

Impact of back-end-of-line architecture on chip-package-interaction in advanced interconnects

Chip–package interaction (CPI) has become an increasingly important reliability issue in the microelectronics industry. In order to survive the thermally induced stresses during processing or working lifetime, the complex back-end-of-line (BEOL) layer stacks must have sufficient mechanical strength. The understanding of accelerated mechanical tests performed at wafer level, such as shear microprobing, is needed to early detect the risk of failure in the final IC device. In this study, the impact of the BEOL architecture in terms of via density and metal density on the failure location and the amount of observed BEOL failures is demonstrated by performing a large statistical amount of shear microprobing combined with post-mortem focused ion beam (FIB) cross sections. The experimental results are further supported by local bump pull tests, in-situ scanning electron microscopy (SEM) micro beam bending tests and finite element modeling (FEM). A clear correlation was found between the BEOL architecture and the amount of observed BEOL fractures. It was found that the cross sectional metal area in the topmost Z–group has a stronger impact on the amount of BEOL failures compared to the low or medium, X or Y–groups respectively. This trend was explained in terms of elastic shielding effect. Furthermore, both experimental results and FEM show that the via density may play a dominant role in both crack initiation and crack growth. These findings lead to a better understanding of the robustness of interconnect structures and the stresses they can tolerate and may serve as guidelines to develop a CPI-aware design of advanced nano-interconnects.

Bending Behavior of Lightweight Wood-Based Sandwich Beams with Auxetic Cellular Core.

The work concerns a three-point bending test of beams made of plywood, high density fibre boards, cardboard, and wood-epoxy mass. The goal of the investigation was to determine the effect of thickness and type of wood-based facings on stiffness, strength, ability to absorb, and dissipate the energy of sandwich beams with an auxetic core. The cognitive goal of the work was to demonstrate the possibility of using recycled materials for facings and cores instead of popular wood composites. Experimental studies and numerical calculations were performed on correctly calibrated models. Experimental studies have shown that the beams with HDF facings ( = 1528 MPa, = 12.61 MPa) and plywood facings ( = 1248–1395 MPa, = 8.34–10.40 MPa) have the most favourable mechanical properties. Beams with plywood facings also have a good ability to absorb energy (1.380–1.746 J), but, in this respect, the beams manufactured of HDF (2.223 J) exhibited better capacity. The use of an auxetic core and facings of plywood and cardboard significantly reduces the amount of dissipated energy (0.0093 J, 0.0067 J). Therefore, this type of structures can be used for modeling beams carrying high deflections.

An Indoor Laboratory Simulation and Evaluation on the Aging Resistance of Polyether Polyurethane Concrete for Bridge Deck Pavement

Polyether Polyurethane Concrete (PPC) is a new engineering material used for bridge deck pavement. In this paper, the aging resistance performance of PPC for long-term service is evaluated. Based on the actual climate and environment conditions of bridge deck pavement, the indoor laboratory simulation considering various environmental factors was first proposed, and then the indoor accelerated aging tests of PPC were carried out. Finally, the Cantabro test, the low temperature bending beam test, the rutting test, the splitting test under freeze-thaw cycle and four point bending fatigue test were conducted on the aged PPC specimens. The performances of anti-loose, resistance to permanent deformation, low temperature, water stability and fatigue resistance were evaluated and compared with SBS modified asphalt mixture (SBSM). Test results showed that PPC had good anti-aging performance, and the road performance of PPC after aging was still better than that of non-aging SBSM, which can be used for the long-term service as a bridge deck pavement material.

Effect of nano montmorillonite on the multiple self-healing of microcracks in asphalt mixture

This study investigated the effect of nano montmorillonite at different damage degree on the multiple self-healing properties of asphalt mixture by semicircular bending (SCB) test. Four kinds of asphalt binder were used to prepare the asphalt mixture. The cumulative fatigue life was measured and the multiple healing index (MHI) was proposed as an index to evaluate the multiple healing. The test results of different healing temperatures and damage degrees were fitted to obtain the threshold conditions of multiple self-healing. The fatigue life of asphalt mixture was evaluated by four-point bending beam test. Results showed that montmorillonite (MMT) could improve fatigue resistance and the self-healing ability of asphalt mixture, especially when the damage degree was small. The multiple healing capacity of the mixture decreased with the increased of the degree of damage. After freezing-thawing cycle, the self-healing ability decreased significantly. In addition, the results of multivariate nonlinear fitting showed that when the damage degree of montmorillonite modified asphalt mixture was less than 30% and the ambient temperature reaches 50°C, multiple times of self-healing can be effectively achieved. The fitting results can also be used to calculate the self-healing threshold conditions of other asphalt mixtures.

Performance Characterization of Hot Mix Asphalt with High RAP Content and Basalt Fiber.

Incorporating reclaimed asphalt pavement (RAP) into asphalt mixtures achieves astonishingly environmental and economic benefits. However, there is hesitation to use higher RAP content due to the concern regarding the deterioration in pavement performance, especially the cracking resistance. Basalt fiber has been considered an effective additive to reinforce the performance of asphalt mixtures and, subsequently, the reinforcement effect is also expected for high-RAP content mixtures. Therefore, this study investigated the effect of basalt fiber on the pavement performance of asphalt mixtures with 0%, 30%, 40%, and 50% RAP contents against high-temperature performance, moisture susceptibility, low-temperature and intermediate-temperature cracking resistance, based on the wheel-tracking test, the uniaxial penetration test, the freeze-thaw splitting test, the low-temperature bending beam test, the semicircular bend fracture test and the indirect tensile asphalt cracking test, respectively. In addition, a performance-space diagram was developed to determine the mixture performance shift caused by basalt fiber. The results showed that adding basalt fiber compensated for the detrimental effect caused by RAP, leading to significant enhancement in moisture susceptibility and low- and intermediate-temperature cracking resistance of mixtures with high RAP content, along with the enhancement in high-temperature performance, indicating that basalt fiber can contribute to the use of high RAP content.

Evaluation of Stone Mastic Asphalt Containing Ceramic Waste Aggregate for Cooling Asphalt Pavement.

Construction and demolition waste material is of great potential for use in pavement engineering. This paper aims to investigate the feasibility of ceramic waste aggregate (CA) used in cooling asphalt pavement through a series of test methods and simulation techniques. Stone mastic asphalt (SMA) containing 10%, 20%, 30%, 40%, and 50% coarse ceramic waste aggregate (CASMAs) was first designed using the Marshall method. Afterward, the road performance and thermal insulation performance of the five different CASMAs were assessed by a comprehensive lab test, including a wheel rutting test, moisture susceptibility test, bending beam test, fatigue beam test, and indoor thermal insulation test. Finally, a 2D finite-element (FE) model was developed to investigate the transient thermal field and rutting deformation response of the cooling asphalt pavement with CASMAs. Results show that CASMAs experienced degradation of rutting resistance, moisture susceptibility, and anti-cracking performance while still meeting technical requirements with CA content of up to 40%. On the other hand, CASMAs can cool the pavement’s temperature by 11.5 °C at the bottom of asphalt layers. The permanent rutting deformation of cooling asphalt pavement was 45.36% smaller than that of conventional asphalt pavement without CASMAs. Based on the test results and numerical simulation results, the optimum content of ceramic waste aggregate in stone mastic asphalt was recommended as 40%.

Fracture of Structured Rocks and Materials in Nonuniform Stress Fields

The article reports the experimental data on brittle rock strength from the bending tests of beams and from diametrical fracture of disk specimens with an axial hole. The author uses the nonlocal fracture approach and compares the strength from the tests with the tensile strength of rocks. It is shown that the different geometry fracture tests allow determining the structural parameter of a medium.

Characteristic Research and Test for Component Strength of C/C and C/SiC Connecting End Frame Part

An analytical study on the component-level mechanical functional properties of the thermal structure connecting end frame was conducted, illustrating by advanced composite materials (ACM) C/C and C/SiC. Different grades of component-level experiments and analyses the weakness of composite connecting end frames were carried out, including the screw hole pull-out test, which mainly reflects the features of materials, the bending test of corner beams, and the corner box test with structural characteristics. The failure of different components and the factors have been obtained from this research.

Effect of Load on the Corrosion Behavior of Friction Stir Welded AA 7075-T6 Aluminum Alloy.

The paper focuses on the corrosion behavior of aluminum joints made by friction stir welding as a function of loading conditions. A four-points bend-beam test, constant loading test, and slow strain-rate test were carried out on AA 7075-T6 alloy in aerated NaCl 35g/L solution at room temperature monitoring the free corrosion potential. The penetration depth of the intergranular attack was deeper after the four-point bent-beam tests compared to all the other testing techniques. Preferential dissolution along the grain boundaries was found in the heat-affected zone and the attack follows the elongated grains structure along the rolling direction. However, no stress-corrosion cracking phenomena were detected. No relevant stress corrosion cracking (SCC) crack embryos propagation was noticed under uniaxial tensile tests—both constant loading and slow strain-rate tests—manly due to the high dissolution rate occurring at the crack tip which promoted premature shear ruptures.

Fatigue behavior study of a dense graded HMA using the four point bending beam test aided by an in-situ instrumentation at BR-116/RS, Brazil

A fadiga é caracterizada pela deterioração estrutural de um material quando submetido a repetidos esforços de tensão-deformação. O ensaio laboratorial comumente empregado no Brasil para análise de fadiga em misturas asfálticas é o ensaio de tração indireta (IDT). Como alternativa ao ensaio IDT, o ensaio de flexão em quatro pontos (4PBBT) submete o material a um estado de tensões mais realístico em relação ao campo. Este trabalho avaliou o comportamento à fadiga de uma mistura asfáltica com ligante modificado por polímero (PG76-11) usando os ensaios IDT e 4PBBT. Um segmento da rodovia BR-116/RS, pavimentado com o mesmo material, foi instrumentado para monitorar as respostas mecânicas na camada asfáltica, permitindo a avaliação do material sob condições de tráfego real, e através do monitoramento ao longo do tempo, permitindo melhor entendimento do desgaste estrutural. Em relação aos ensaios laboratoriais, o ensaio 4PBBT apresentou uma melhor relação com o observado em campo.

VIGAS DE CONCRETO REFORÇADO COM FIBRAS DE AÇO SUBMETIDAS À FLEXÃO

RESUMO: O presente trabalho compara experimentalmente os resultados de ensaios à flexão a quatro pontos de vigas de concreto com e sem adição de fibras de aço. O objetivo principal do trabalho foi analisar as influências que as fibras de aço tendem em modificar o surgimento de patologias relacionadas à fissuração do concreto. Este trabalho se justifica pelo fato de que a implementação de elementos de reforço ao esforço de flexão não é amplamente explorada no Brasil, mesmo tendo ocorrido um crescimento considerável nas últimas décadas. Vigas com adição de fibras não é um método totalmente difundido no Brasil, entretanto pisos de concreto e lajes reforçados com fibras já são mais usuais nas construções do país Para análise do comportamento à flexão foram realizados ensaios de laboratório com oito corpos de prova, moldados com e sem fibras, a maioria com entalhe induzindo a propagação vertical da fissura na região central da viga. Foi utilizado um baixo teor de fibras de aço (0,25%) para não implicar na trabalhabilidade do concreto e, com isso, testar um material que pode ser confeccionado em situações usuais da construção civil. Para o teor de fibras estudado observou-se um acréscimo de 26,6% no valor da carga máxima atingida. Outro fator relevante foi que não houve dificuldades em relação a trabalhabilidade do concreto quando adicionado as fibras. Os resultados obtidos sobre a resistência comprovaram eficiência quando se usou as fibras no ensaio a flexão.
 ABSTRACT: The present work compares the results experimentally of four-point bending tests of concrete beams with and without addition of steel fibers. The main objective of this work was to analyze the influence of steel fibers in modifying the appearance of pathologies related to concrete cracking. This work is justified by the fact that the implementation of reinforcement elements to the flexion effort is not widely explored in Brazil, even though there has been a considerable growth in the last decades. Beams with addition of steel fibers are not method used in Brazil, however, concrete floors and fiber-reinforced slabs are more common in the country's constructions. For bending behavior analysis, laboratory tests were performed with eight test specimens, molded with and without fibers, most of them with notch, inducing vertical propagation of the crack in the central region of the beam. It was use of a low content of steel fibers (0,25%) to avoid the workability of the concrete and, with this, to test a material that can be made in usual civil construction situations. For the fiber content studied, there an increase of 26,6% in the maximum load value. Another relevant factor was that there were no difficulties in relation to the workability of the concrete when added the fibers. The results obtained on the resistance proved efficiency when the fibers were used in the bending test.

Mechanical Performance Characterization of Lignin-Modified Asphalt Mixture

Lignin, as a bio-based waste, has been utilized in the asphalt industry due to various advantages. This study aimed to investigate the effects of two lignin products (lignin powder and lignin fiber) on the mechanical properties of asphalt mixtures. The raveling, rutting, thermal and fatigue cracking resistance, and moisture susceptibility of different asphalt mixtures were respectively evaluated by the Cantabro test, wheel loading tracking test, semicircular bending test, four-point beam bending test, and freezing-thaw cyclic test. Results show that asphalt mixture with lignin powder-modified asphalt improved the overall mechanical performance. However, lignin fiber showed contradictory effects on certain mechanical properties, i.e., improved rutting resistance and thermal cracking resistance of asphalt mixture, degraded abrasion resistance, fatigue performance, and moisture stability. Therefore, cautions need to be taken when incorporating lignin fiber into asphalt mixture.

Mitigation of desiccation cracks in clay using fibre and enzyme

Formation of cracks during desiccation is a natural phenomenon in expansive clay. Mitigation of desiccation-induced cracks is highly beneficial for increasing the life span of geo-infrastructures particularly in hydraulic barriers. Improvement of soil properties using additives is a key method in controlling desiccation crack formation and their influence. This paper presents experimental results for an expansive clay modified with nylon fibre and an enzyme-based product. A series of desiccation cracking tests were carried out with varying fibre contents and a constant enzyme dosage. Three-point bending beam tests were performed to evaluate tensile strength of the modified clay. The additives, fibre and the enzyme were able to alter the crack patterns significantly thereby alleviating the effects of cracks. Furthermore, the addition of enzyme alone increased the tensile strength by about 50% while the combined effect of both fibre and enzyme increased the tensile strength by approximately 100% compared with untreated soil. Based on measurement of crack patterns and other properties of the modified clay, the investigation suggests the potential for the fibre-enzyme addition to mitigate desiccation cracks. Further work needs to be carried out to determine optimal dosing requirements for each additive and investigate the effects of potential interactions between the fibre and enzyme.

Foam Concrete and Composite Fittings Cohesion Parameters: Experimental Result and Numerical Simulation

The article presents the computer simulation results and real experiment of foam concrete cohesion with glass-composite, basalt-composite and metal fittings in bending elements. Numerical simulation of beams implemented with software package “Lira-SAPR 2013” using finite element method for modeling. For real experiment used bending beam test method according to ISO 10406-1:2015. As a result, the influence of the loading level and foam concrete density on the reinforcement slipping value and foam concrete cohesive strength with reinforcement in the bending elements. The foam concrete cohesive strength with glass-composite fittings meets the standard requirements, so it can be recommended for the foam concrete bending elements reinforcement. Verification of the computer simulation results with the real experiment data allowed to establish the efficiency of the used numerical model and revealed the need to use the cohesion parameters in the "foam concrete – reinforcement" system for foam concrete structures calculations in specialized programs.

Material Analysis of Steel Fibre Reinforced High-Strength Concrete in Terms of Flexural Behaviour. Experimental and Numerical Investigation.

The paper presents the results of tests for flexural tensile strength (fct,fl) and fracture energy (Gf) in a three-point bending test of prismatic beams with notches, which were made of steel fibre reinforced high-strength concrete (SFRHSC). The registration of the conventional force–displacement (F–δ) relationship and unconventional force-crack tip opening displacement (CTOD) relationship was made. On the basis of the obtained test results, estimations of parameters fct,fl and Gf in the function of fibre reinforcement ratio were carried out. The obtained results were applied to building and validating a numerical model with the use of the finite element method (FEM). A non-linear concrete damaged plasticity model CDP was used for the description of the concrete. The obtained FEM results were compared with the experimental ones that were based on the assumed criteria. The usefulness of the flexural tensile strength and fracture energy parameters for defining the linear form of weakening of the SFRHSC material under tension, was confirmed. Own equations for estimating the flexural tensile strength and fracture energy of SFRHSC, as well as for approximating deflections (δ) of SFRHSC beams as the function of crack tip opening displacement (CTOD) instead of crack mouth opening displacement (CMOD), were proposed.

Crack monitoring in reinforced concrete beams by distributed optical fiber sensors

This paper investigates the use of distributed optical fiber sensors (DOFS) based on Optical Frequency Domain Reflectometry of Rayleigh backscattering for Structural Health Monitoring purposes in civil engineering structures. More specifically, the results of a series of laboratory experiments aimed at assessing the suitability and accuracy of DOFS for crack monitoring in reinforced concrete members subjected to external loading are reported. The experiments consisted on three-point bending tests of concrete beams, where a polyamide-coated optical fiber sensor was bonded directly onto the surface of an unaltered reinforcement bar and protected by a layer of silicone. The strain measurements obtained by the DOFS system exhibited an accuracy equivalent to that provided by traditional electrical foil gauges. Moreover, the analysis of the high spatial resolution strain profiles provided by the DOFS enabled the effective detection of crack formation. Furthermore, the comparison of the reinforcement strain profiles with measurements from a digital image correlation system revealed that determining the location of cracks and tracking the evolution of the crack width over time were both feasible, with most errors being below ±3 cm and ±20 µm, for the crack location and crack width, respectively.

Local and global response of sandwich beams made of GFRP facings and PET foam core in three point bending test

In the paper behaviour of laminated sandwich beams (FRP face sheet – PET foam core – FRP face sheet) subjected to three point bending is studied. The paper aim is to find practical descriptions enabling effective and accurate estimation of the elastic response, damage and failure of the beams, basing on experiments and static calculations. Therefore a number of tests are described, that were done on laminated coupons and foam specimens in order to choose appropriate material models and find their constants. Experimental results of three-point bending tests of sandwich beams with three types of PET cores are analysed to evaluate the chosen material laws. The beam responses are predicted in numerical static simulations. The equations of problem are solved by means of finite element method (FEM). In the end the experimental and FEM results are compared. They are similar in terms of both their quantity and quality.

Investigation of the Performance of Basalt Fiber Reinforced Asphalt Mixture

This study is focused on the effect of basalt fiber on the road performance of the asphalt mixture. The road performance of asphalt mixture with different dosages of basalt fiber was comprehensively evaluated using Marshall Stability test, the wheel tracking test, the three-point bending beam test and the freezing-thaw splitting test. The road performance of lignin fiber reinforced asphalt mixture and polyester fiber reinforced asphalt mixture also were tested to compare with the road performance of basalt fiber reinforced asphalt mixture. The results showed that basalt fiber can enhance mechanical properties, the low-and high-temperature performance and water sensitivity of the asphalt mixture significantly. Considering the road performance and economic benefits, the appropriate dosage of basalt fiber is about 0.3%. Marshall Stability (MS), dynamic stability (DS), the maximum bending strain and the tensile strength ratio (TSR) of asphalt mixture with 0.3% basalt fiber were increased by 19.6%, 25.5%, 22.2% and 6.0%, respectively. Basalt fiber has certain advantages in improving the low-temperature performance of asphalt mixture by comparison with lignin fiber and polyester fiber.