Shear Strength Of Material Research Articles

Investigation of shear properties of axial flow fan blade material with partial woven jute reinforcements

Axial flow fan blades are often made from glass-fibre reinforced polymers (GFRP), which are increasingly used in making composites. These non-biodegradable composite reinforcements, on the other hand, pose significant environmental and human health risks, especially at the end of its service life. Until now, companies have hustled to use GFRP without regard to disposal. Glass fibres recycling is expensive and unjustifiable. On the other hand, natural fibres are gaining popularity due to their sustainability. So, they're suitable for polymer composites. To improve the biodegradability of GFRP composites after service life, it must be determined to what extent natural fibres can be reinforced in them without significantly affecting mechanical properties. In this work, the material C1 is an 18-ft axial flow fan blade material made of GFRP. The materials C2 to C6 were made by substituting one layer of C1 with woven jute and changing the location of the jute in C1. All the materials are tested for shear strength as per IS 1998-62. The shear strength results were validated by using the finite element software ANSYS R19.2. The woven jute fibre composite has higher shear properties when jute is placed in the second position (C2). C2 preserves the shear strength of the blade material and also improves biodegradability after service life.

Experimental research on the performance of a Novel Geo-filament anchor for an Earthen architectural site

At present, most studies of anchorage techniques for earthen architecture ruins are conducted so as to improve the anchor force, however, the damage caused to the ruins by anchor reinforcement has not been fully considered in practice and no special anchor technique has been applied to reinforce the small sliding mass. This paper summarizes the application and R&D of anchor rod techniques as applied to the protection of the Gaochang Ruins, Turpan, in China. Based on the reinforcement of the small sliding mass of the earthen historical ramparts, a new type of Geotechnical Filament Anchor (GFA) is designed. By changing six parameters, including anchorage length (L), GF thickness (H), bore diameter (D), slurry strength (S), GFA surface state (R) and inclination Angle (A), the tensile strength, failure mode, load displacement (P-S) relationship and strain (ζ-L) distribution characteristics are studied, and corresponding analysis is performed on the test data and phenomena. (1) A formula for the design value of the anchorage force N is presented. (2) Combining the data on the strain distribution at the GF-slurry interface under the action of N, the shear stress distribution model of the anchorage system is obtained. (3) Taking into account the soil mechanical properties of the above-mentioned ruins, the shear stress diffusion coefficient (α) is conceptualized, the formula for the shear strength of the grouting material is obtained, and the allowable ranges of L, D, H, R, and S determined. A new design is proposed for the application of anchorage techniques to earthen ruins in the context of protection of cultural relics, which promotes the design and calculation method described in this paper.

Shear behavior of bedding fault material on the basal layer of DGB landslide

Daguangbao (DGB) Landslide (12 × 108 m3) is the largest landslide triggered by the 2008 Ms8.0 Wenchuan Earthquake, in which basal shear failure develops on an interlayer fault at 400 m deep under the ground. After the landslide, a 1.8 km long (in the sliding direction) oblique shear face is exposed. Different kinds of materials in the interlayer fault of DGB landslide are taken for direct shear test, medium scale shear test, in-situ shear test and ring shear test. The test results show that fault material cohesion ranges from 20 to 320 kPa and internal friction angle from 15° to 41°. Shearing strength of interlayer fault materials is related to fragmentation degree of structure. The lower fragmentation degree the more obvious strain softening characteristics of materials, the higher fragmentation degree the poorer shearing resistance of materials. Compared with argillaceous materials in the same fault, the mylonitic materials are of higher shear strength and internal friction angle. Both mylonitic materials and breccia materials are strong in liquefying. In saturated undrained cases, shear strength of fault materials could drop to 9.7°, with S3 down to 0. In saturated undrained dynamic shear conditions, fault internal friction angle could be reduced to 23.1° and 4.2°. It is concluded that low friction feature of fault materials caused by the influence of groundwater is the main reason for destabilization of DGB landslide.

Enhancing Shear Strength of Bonding Materials Used for Asphalt Concrete and Composite Pavement Layers

A tack coat is a thin cut-back cement or asphalt emulsion coating applied on an existing non-absorbent pavement. A good bonding between the asphalt and concrete is necessary to provide sufficient structural strength. Poor adhesion will result in shear failure. The shear test is one of the basic tests to determine bond strength. This study aims to quantify the best shear resistance obtained using three types of cut-back asphalts (RC70, RC800 modified with polymer 4.5% and MC70), PG (76-10) modified asphalt cement with polymer 4.5%, Sikadur®-31 CF usage at elevated temperatures between +25°C and +45°C and Nitomortar TC2000 epoxy from Fosrok company. All are applied on concrete surfaces with an application rate of 0.5kg/m2 except for Nitomortar, which depends on layer thickness ranges between (1-2.5) mm instead of the application rate. A special attachment and loading mechanism were designed to facilitate the measurement of the asphalt-to-concrete contact shear strength in Al-Ahmad Lab-Baghdad. Vertical shear force is applied to a multiple-layer sample with a 0.25 kN/sec rate until the failure occurs at the interface. The final result of this test is stated in terms of the maximal force or power needed to break the bond. The average shear strength of tack coat materials is (0.049, 0.0455, 0.0085, 0.677, 1.088, 1.361) MPa Respectively. It concluded that Fosrok epoxy has the maximum shear strength. Also, adding polymer to asphalt increased the viscosity. All materials used enhanced the shear strength of bonding materials used for asphalt concrete and composite pavement layers

Examining the conditioning factors that influence material shear strength of particle deposits in a full-scale drinking water distribution laboratory

Experiments with synthetic iron oxide particles in a full-scale pipe system were used to investigate the material shear strength of particulate accumulation. Results highlighted the importance of the pipe wall roughness on the attachment process.

Application of Vertical Electrical Sounding for Subsurface Characterization to Determineslope Instability at Perizie, Nagaland

Vertical Electrical Sounding (VES) technique which employs the Schlumberger depth sounding method was used to investigate the subsurface conditions at the landslide in Perizie colony, Kohima. The interpretation of the VES curves shows differing lithology consisting of weathered shales with associated clay, which is considered an important factor for slope instability. The shear strength of the slope materials, including the country rocks and the soil cover, is also significantly reduced and easily detached due to the effects of weathering and erosion, causing the landslides. Three to six possible geo-electric layers are delineated from the variations in the resistivity values, with the lithologies consisting of topsoil followed by alternate layers of weathered and fractured rocks of varying thickness. The analysis also points to the presence of a weak zone at a depth of about 10 m, which is not apparent from the surface. The formation of groundwater aquifers in the fractured zones indicates high risk for slope failure as this accelerates the weak country rocks to weather. The results obtained by this study correspond well with the available borehole data of the area.

Prediction of shear strength for granular material under the effect of liquid-powder binder using a PSO–RBF neural network model

In this paper, the performance of particle swarm optimization–radial basis function (PSO–RBF) neural network was examined to predict the shear strength of granular material. Direct shear tests were conducted on glass beads (400–600 mm in size) with 2% of liquid content at different powder contents (1, 2, 3, 4, and 5%) as the binder. Hydrated lime (HL), quick lime (QL), calcite, and sodium lignosulfonate (SL) powders were used to compare their shear strength characteristics. The actual loading stress was controlled at five levels (6.9, 10.3, 13.8, 17.3, and 20.7 kPa), and five further levels (24.2, 27.7, 31.2, 34.6, and 38.1 kPa) were used for prediction. Results showed that at 2% of water, the shear strength regularly increased at all amounts of HL, QL, and calcite powder. With the increased SL powder, the shear strength decreased. The actual and predicted maximum shear stress values for different levels of normal stress were fitted using the widely accepted Mohr–Coulomb criterion to determine the internal friction angle and cohesion, and R 2 was improved from 0.98 to 0.99. The PSO–RBF neural network model was a flexible and accurate method for the prediction of the shear strength of granular material.

The use of laterally mounted stress gauges in the measurement of strength during shock loading

The shear strength of materials under shock-loading conditions has long been recognized as being of the utmost importance, as this can be related to deformation mechanisms and ballistic performance. As such, a number of experimental techniques have been developed to study this component of shock loading, and in this paper, we concentrate on the embedded lateral stress gauge. We acknowledge that as the requirements of the target assembly necessitate that the target be sectioned, the gauge glued in place, and the target reassembled, it is possible that the gauge response is dominated by its local environment. As a consequence, we have, therefore, asked three questions—can the gauge be placed in a known stress condition and measure the correct lateral stress and shear strengths; do the results from the lateral stress gauge agree with other non-invasive techniques; and finally, if we do trust the results from lateral gauges, can they be placed in context with other known shock-induced materials responses. In all three cases, we believe that the answer is yes, and we present evidence for all three situations.

Investigation of the underwater clinching process for joining metal sheets

The underwater building of marine or offshore structures requires the application of underwater joining techniques. Compared to underwater welding and underwater adhesive bonding, clinching is energy efficient, clean, and simple to the tool. In particular, clinching is not susceptible to the effects of water as well as water depth. In the present study, the joinability of metal sheets by the underwater clinching process was investigated by experimental methods. Clinching tools with extensible die were used to join Al5052 sheets at different force levels. Material flow, shear strength, tensile strength, failure modes, and energy absorption were analyzed. The results showed that the application of clinching with an extensible die could be extended to underwater joining. In the study, three failure modes of the joints were obtained, including button separation, hybrid failure, and neck fracture. Increasing the forming force was effective in improving the strength of underwater clinched joints. 40 kN was considered to be the optimum forming force for joining double layers of Al5052 sheets using underwater clinching process.

Effects of Particle Size and Soil Bed on the Shear Strength of Materials in the Direct Shear Test

Generally, direct shear apparatus is used to determine the shear strength parameters of soil and rock for designing a geotechnical engineering structure. However, the size of the shearing box and the soil sample is key for evaluating the shear strength parameters of test materials, and also testing conditions in the laboratory are different from site conditions. This research aimed to focus experimentally on the effect of particle size and the property of subgrade materials that were necessary keys for installing apparatuses for the direct shear test. According to the experimental results based on a 5 x 5 cm shear box, an increase in average particle size and coefficient of curvature could provide higher shear strength in terms of internal friction angle of the sample, but not for the case of higher value of the uniformity coefficient. Using both 5 x 5 cm and 30 x 30 cm shear boxes, a large B/Dmax ratio is not the key for determining appropriate parameters when testing with samples that have a nearly uniform size. Samples varied in thickness of both the ballast and subgrade layers, were investigated and observed by a large shear box. It was found that good properties of subgrade materials affected the shear strength of ballast materials, and they provided underestimates of strength when the bottom of the shearing box was rigid. The modified parameter of ballast materials on the subgrade layer is suggested for obtaining strength parameters reflecting the ballasted track system.

Triaxial Testing and Numerical Simulation on High Fill Slopes of Gobi Gravel Soils in Urumchi

Abstract Gobi gravel soils (GGS), widely distributed in northwestern China, are used as main filling materials in construction of high filling slopes in Urumqi airport. To analyze the stability of slopes, the shear strength of the granular materials should be investigated. To this end, a series of large-scale triaxial tests were performed on GGS to investigate the influencing factors on their mechanical behavior, including coarse content, degree of compaction, and confining pressure. The results show that the stress-strain curves show strain-hardening behavior within 90 % coarse content. The specimens show a transition from shear contraction to shear dilation with increasing coarse fraction and degree of compaction; they show contraction with an increase of confining pressure. The interlocking strength is significantly affected by the degree of compaction and coarse content, whereas the frictional angle changes within a narrow range from 35° to 40°. Based on testing results, the stability of the filling slopes was simulated using limit equilibrium method. The effect of the slope angle and geotextiles on the safety factor is discussed, through which the optimum slope angle and optimum geotextiles reinforcement are determined.

Seismic Bearing Capacity of Strip Foundations with Nonlinear Power-Law Yield Criterion Using the Stress Characteristics Method

The computations of the bearing capacity of foundations have generally been carried out with the usage of the Mohr-Coulomb failure criterion—a linear yield envelope in a shear stress–normal stress plot. However, as noted from many experimental observations, the failure criteria associated with most geomaterials are generally nonlinear. A novel computational analysis, based on the stress characteristics method, has been performed in the current study to compute very accurately the seismic bearing capacity of a rough strip foundation considering a nonlinear power-law yield criterion. The analysis incorporates the effect of pseudostatic horizontal seismic inertial forces. The obtained results can, however, be used to include even the effect of the vertical component of the seismic inertial forces. The present formulation is based on the consideration of a curvilinear nonplastic trapped wedge below the footing base. By carrying out a detailed parametric analysis, the effects of different material shear strength parameters, overburden pressure, seismic forces, and foundation width on the bearing capacity factor Nσ have been examined. With the changes in horizontal seismic acceleration coefficients, the slip line patterns have also been explored. The results from the present analysis compare quite well with that reported from studies available in the literature.

Predicting Angle of Internal Friction and Cohesion of Rocks Based on Machine Learning Algorithms

The safe and sustainable design of rock slopes, open-pit mines, tunnels, foundations, and underground excavations requires appropriate and reliable estimation of rock strength and deformation characteristics. Cohesion (𝑐) and angle of internal friction (𝜑) are the two key parameters widely used to characterize the shear strength of materials. Thus, the prediction of these parameters is essential to evaluate the deformation and stability of any rock formation. In this study, four advanced machine learning (ML)-based intelligent prediction models, namely Lasso regression (LR), ridge regression (RR), decision tree (DT), and support vector machine (SVM), were developed to predict 𝑐 in (MPa) and 𝜑 in (°), with P-wave velocity in (m/s), density in (gm/cc), UCS in (MPa), and tensile strength in (MPa) as input parameters. The actual dataset having 199 data points with no missing data was allocated identically for each model with 70% for training and 30% for testing purposes. To enhance the performance of the developed models, an iterative 5-fold cross-validation method was used. The coefficient of determination (R2), mean absolute error (MAE), mean square error (MSE), root mean square error (RMSE), and a10-index were used as performance metrics to evaluate the optimal prediction model. The results revealed the SVM to be a more efficient model in predicting 𝑐 (R2 = 0.977) and 𝜑 (R2 = 0.916) than LR (𝑐: R2 = 0.928 and 𝜑: R2 = 0.606), RR (𝑐: R2 = 0.961 and 𝜑: R2 = 0.822), and DT (𝑐: R2 = 0.934 and 𝜑: R2 = 0.607) on the testing data. Furthermore, to check the level of accuracy of the SVM model, a sensitivity analysis was performed on the testing data. The results showed that UCS and tensile strength were the most influential parameters in predicting 𝑐 and 𝜑. The findings of this study contribute to long-term stability and deformation evaluation of rock masses in surface and subsurface rock excavations.

Mechanical properties of unbound granular materials reinforced with nanosilica

The development of new technologies for soil improvement has been a hot research topic in the fields of geological engineering, geotechnical engineering, and road engineering. Nanomaterials have been proven to offer significant advantages in the field of geotechnical material enhancement due to their unique structures and excellent properties. The effect of nanosilica amount on the stress-strain behavior, elastic modulus, shear strength, and shear parameters of unbound granular materials was investigated, and its potential enhancement mechanism was discussed in this research. Treated samples with nanosilica contents (by weight) of 0,1%, 2%, 3%, 3.5%, 4%, and 4.5% were prepared and rigorously examined through unconsolidated undrained (UU) triaxial tests under different confining pressures. Also, the intrinsic mechanism and variations in the microstructure of the specimens were investigated by the computed tomography (CT) and scanning electronic microscope (SEM). Testing results showed that with the addition of more nanosilica, the elastic modulus and shear strength of the specimens increased and the ductility decreased. The apparent cohesion of the treated specimens increased approximately linearly and had almost as little effect on the internal friction angle. The maximum improvement rate was obtained at 3.5% of nanosilica content. The CT and SEM scanning results indicated that the control specimen has a higher void ratio than the treated specimens, and the filling and nucleation effects of nanomaterials may be the intrinsic mechanism to improve the mechanical properties of unbound particulate materials. The experimental results contribute to enriching the application of nanomaterials in geotechnical engineering, guiding the optimization of mechanical properties of unbound granular materials.

Determination of the Chip–Tool Contact Length in Orthogonal Cutting

Abstract This work presents an experimental–numerical approach aimed at determining the chip–tool contact length during orthogonal cutting of annealed AISI 4340 steel (223 HV) with TiN-coated tungsten carbide inserts. Initially, pin-on-disc tests were performed, followed by orthogonal cutting tests. The components of the cutting force were used to calculate the coefficient of friction in orthogonal cutting, and its value was compared with those obtained under sliding. Moreover, the cutting force components obtained experimentally were used to assess the reliability of the finite element model and estimate the temperature in the cutting zone. The contact length between chip and rake face was calculated based on the experimental feed force and shear strength of the work material and was compared with the results provided by an analytical model. The experimental–numerical approach can be considered more accurate due to the fact that it considers the effect of the tool–chip interface temperature on the shear strength of the work material. However, the analytical model is quite straightforward, since it only requires the values of chip thickness and undeformed chip thickness to estimate the tool–chip contact length.

Mechanical and failure analysis of thick composites under hygrothermal conditions by a novel coupled hygro-thermo-mechanical multiscale algorithm

A novel coupled hygro-thermo-mechanical multiscale-APFEA (HTM-multiscale-APFEA) algorithm is developed to precisely predict the mechanical and failure behavior of thick fiber-reinforced laminated composites under hygrothermal conditions. The Fourier and Fick's equations are simultaneously solved by the proposed fully-coupled temperature-moisture concentration (FCTM) algorithm to account for their mutual effects on each other. Two subroutines, one responsible for the homogenization, failure analysis, and also linking the macro and micro models of the composite material, and another for establishing the constitutive equations and failure analysis of the cohesive/adhesive material, are integrated into a user-defined material code extended for also defining the materials failure behavior. The effects of temperature and moisture conditions on the stiffness, strength, coefficients of hygrothermal expansions (CHEs), and fracture toughness of matrix and cohesive/adhesive materials are considered. The results of the HTM-multiscale-APFEA algorithm are verified against the results of experimental data, analytical high-order theories, and reliable numerical analysis. Furthermore, the failure analysis of composite laminate under hygrothermal conditions coupled with mechanical loading (bending) is carried out by the HTM-multiscale-APFEA algorithm, and compared with experimental data. The results have shown that the transverse tensile strength, shear strength, and transverse Young's modulus of the composite material degrade respectively about 72%, 13%, and 40% in the most severe hygrothermal conditions at the material boundaries; while the normal stiffness and normal strength of the cohesive/adhesive material decline by about 73% and 47%, respectively, at outer layers. In addition, the mixed-mode fracture toughness of the adhesive material elevates from 0.55 ×103N/m at inner layers to 2.14 ×103N/m at outer layers of adhesive material. The proposed algorithm is highly flexible and can easily be adapted to model different types of laminated composites.

Experimental and numerical investigation of G-UHPC based novel multi-layer protective slabs under contact explosions

Geopolymer based ultra-high performance concrete (G-UHPC) has been recognized as a ‘eco-friendly’ form of ultra-high performance concrete owing to its beneficial characteristics, e.g. waste utilization, reduction in carbon dioxide emission, low energy consumption, superior mechanical behavior and adjustable hardening time. Thus, G-UHPC is well suitable for the rapid construction of blast-resistant structures. In this study, four slabs, including a reference normal strength concrete (NSC) slab and three novel multi-layered composite slabs fabricated by G-UHPC, steel wire mesh (SWM) and energy absorber foam materials, were tested on their blast resistance against contact explosions and the corresponding numerical simulations were carried out. Four failure patterns (crater, crater and spalling, breach-perforation and breach-punching) were quantitatively characterized. The G-UHPC slab reinforced with SWM exhibited superior blast resistance as compared to the referenced NSC specimen. The low stiffness and shear strength of the energy absorber foam materials were the main reasons for the breach-punching failure mode. The acoustic impedance and compressibility of the energy absorber foam materials must be reasonably considered to achieve a positive effect on the blast resistance of the concrete slabs. The developed finite element mode could effectively predict the failure characteristics of the specimens.

Improvement of Shear Strength of Zeolite-Bentonite Liner Material under High Temperatures with Tincal and Pumice

Thermal changes (high temperature and thermal cycles) occur around energy structures, such as energy piles, nuclear waste repositories, etc. Sometimes these temperature changes affect the engineering properties of surrounding soils undesirably. Hence, there is a need for durable soils that can maintain their engineering properties unchanged under high temperature and thermal cycles for a long time. Tincal and pumice are used in the production of temperature-resistant and heat-insulated materials. Therefore, in the present study, 10% and 20% tincal and pumice additives were added to zeolite-bentonite mixtures and shear strength behavior of the mixtures was investigated under room and high temperatures (80°C). According to the results, the maximum shear stress values of zeolite- bentonite mixtures generally increased in the presence of tincal and pumice additives under high temperature. Both additives are effective for improvement, however; the effect of pumice can be more pronounced.

Triaxial mechanical properties and microscopic characterization of fiber-reinforced cement stabilized aeolian sand–coal gangue blends

To understand the mechanical properties of fiber-reinforced cement stabilized aeolian sand–coal gangue blend materials and reveal their failure mechanism, polypropylene fiber was uniformly incorporated into cement stabilized aeolian sand–coal gangue blend materials. Triaxial compression tests were carried out to study the coupling effect of different fiber contents and fiber lengths on the shear strength of the blend materials. The internal physical and chemical mechanisms of structural performance evolution were clearly revealed by scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and X-ray diffraction (XRD) at the micro level. The results show that adding 2 ‰ 12 mm fiber can effectively improve the shear properties of the sample. When the fiber length is 12 mm, the elastic strain energy first increases and then decreases with the increase in fiber content. When the fiber content is 2 ‰, the total energy and elastic strain energy increases steadily with the increase in fiber length. SEM results revealed that the fiber was gradually wrapped with the formation of cement hydration products, which provided both induction and bridging properties. The interface between fiber and granular particles was composed mainly of single fiber grip and fiber network formed by the random distribution of fiber. In the shear process, the fibers in the sample exhibited two failure modes: interface slip and tensile break.

The effect of core materials on flexural behaviour of sandwich panels with basalt FRP facesheets

The flexural behaviour of sandwich panels with basalt fiber-reinforced polymer (BFRP) facesheets was investigated. A total of 10 sandwich panels were subjected to six-point flexural tests to simulate uniformly distributed loading conditions. The variable parameters were the core thickness (30, 50, 60 and 100 mm), core category (polyurethane [PU], extruded polystyrene [XPS], rock-mineral wool [RW]), and hybrid core (PU+RW and XPS+RW). Finally, the shear distribution coefficient of core material for sandwich panels with BFRP facesheets was modified depending on the experimental data. The experimental results showed that an increase in the PU core thickness significantly increased the flexural strength and rigidity of the sandwich panels. For different core materials, the maximum loads of the panels were positive with the shear strength of the core materials. Whereas, XPS+RW hybrid core not only can significantly decreases the costs, but also exhibits the highest bearing capacity and stiffness as compared with the PU+RW hybrid and PU cores.