Ultimate Shear Stress Research Articles

Transient response analysis of sandwich composite panel

In order to introduce a novel way relied on enhancing structural design as well as utilizing advanced material for protecting nonmetallic structures from detrimental impacts of transient thermal shock, this research analyzes the transient coupled thermo-elasticity response of the sandwich cylindrical panel with nanocomposite face-sheets strengthened with the functionally graded distributions of graphene-platelets affected by thermal shock loading. To determine the performance of the simply-supported system in the content of the time-altering stresses and deflections, the analytical solving approach, according to the broadly-known Navier technique, is applied to the governing equations developed on the bases of the exact theory of elasticity. It is considered that the internal surface of the panel is thermally isolated, while the outer surface is affected by thermal shock. The energy balance relation specified for this thermal boundary condition is solved to acquire the temperature gradient. Inverting the Laplace transform would be done with the aid of Dubner and Abates’ technique to designate time-history of displacements, shear stresses, and temperature distribution. The Halpin-Tsai micromechanics adjusted for nanocomposites is utilized to calculate thermoelastic properties of the nanocomposite face-sheets. The obtained numerical outcomes revealed the growth of the geometrical factor called mid-radius to thickness ratio leads to higher ultimate temperature and lower transverse shear stress.

Opredelenie nesushchei sposobnosti armirovannogo kontaktnogo shva na osnovanii dvuchlennogo zakona treniya Deryagina [Deryagin binomial law of friction for bearing capacity identification of reinforced joint

Cast-in-place and precast construction must consider a possible fracture of concrete along the reinforced joint. Moreover, the joint quality significantly affects its strength properties. The stress-strain state of the joint can be divided into three classical stages.It is shown that the stress-strain state of cast-in-place and precast construction under a shear load, is characterized by the linear dependence between the maximum shear stress, vertical compression of the joint, and transverse reinforcement. Since the joint deformation relates to friction and adhesion, the Deryagin binomial law of friction is used to determine the bearing capacity identification of the reinforced joint.The proposed calculation method implies the ultimate shear stress as an exhaustion criterion for the bearing capacity, which based on the true friction coefficient, compression stress and yield strength in the transverse reinforcement. It is shown that the obtained results are in good agreement with the experimental data.

Flexural performance of squared one-sided CFRP patches: modelling and experimental study

ABSTRACT Three-point bending analysis, experimental and numerical, is conducted for three different sizes, 30*30 mm, 40*40 mm and 60*60 mm, of one-sided square cross-ply TEXIPREG HS 160 RM carbon-fiber-reinforced polymer (CFRP) patches as well as intact and notched specimens. The tests are carried out with the aim to study the influence of the patch’s size on the flexural properties of the specimen. Hashin-2D damage initiation criterion is adopted to investigate the failure in each ply, and the damage evolution is represented by the stiffness degradation. The intact and notched laminates flexural properties are investigated as well as notch sensitivity. The bonded patch repairs efficiency is investigated in the light of ultimate load, flexural modulus, peel and shear stresses along the bond-line as well as the damage initiation coefficient at critical zones. A significant advancement in the flexural modulus and ultimate load for the repaired laminates is noticed with increasing the patch’s size. A Parametric numerical study is conducted to investigate the influence of the patch size on the damage initiation coefficient at the critical zones. The recommended patch’s size is 44*44 mm in order to avoid failure initiation at the patch corner overlap on the parent laminate.

Influence of temperature modes of processing chia seed meal gel on its rheological and functional-technological properties

The object of research. One of the alternatives of naturally occurring structuring agents with great potential in the food industry is the use of chia seeds. The meal obtained from the processing of chia seeds is the object of the above studies.
 Investigated problem. The study of changes in the emulsifying and rheological properties of chia seed meal, depending on the temperature treatment regimes, will determine the manifestation of the cryoprotective properties of this additive. This will help to solve the problem of deterioration in the quality of frozen split ends as a result of uncontrolled formation of ice crystals in the structure of the meat product.
 Main scientific results. Determination of the effect of heat treatment (heating to 70±2 C and freezing to -18 °C in the center) on the emulsifying properties of hydrated systems of chia seed meal showed that the emulsifying ability index increases by 7 % and 16 %, and the emulsion stability - by 8.7 % and 18.8 % according to the type of heat treatment. A decrease in emulsifying ability, emulsion stability, effective viscosity and shear stress was found in proportion to an increase in the degree of hydration.
 An increase in the indicators of effective viscosity and tangential shear stress as a result of heat treatment of prototypes was noted – by 45.3 % and 46.5 %, respectively. Freezing the hydrated dispersion of chia seed meal led to an increase in the ultimate shear stress by an average of 18.45 % compared to the untreated sample, the effective viscosity of the experimental dispersion did not change.
 The area of practical use of the research results. It can be used at food industry enterprises to improve the emulsifying and structural properties of products and their enrichment with dietary fiber.
 The innovativeness of the proposed solution. The results obtained prove the prospects of using this additive as a stabilizer, emulsifier and cryoprotectant in the technology of frozen meat products.
 The area of use of the innovative solution. This will ensure a consistently high quality of finished products and will improve the efficiency of production of a wide range of food products.

Uncharged Lewis bases yield polydimethylsiloxane ionomers with amidinium alkyldithiocarbamate side chains

AbstractIonomers exhibiting good thermal stability have been prepared by mixing three uncharged components—a poly(dimethyl)siloxane (PDMS) with randomly substituted amidine side chains, an alkylamine, and carbon disulfide. In essence, the three uncharged components produce charged materials, polyelectrolytes with amidinium dithiocarbamate ion pairs. The preparation, structures, and properties of the ionomers at the microscopic and macroscopic levels are reported as a function of PDMS chain length, degree of amidine substitution, and length of the alky group of the amine component. Whereas ionomers with hexyldithiocarbamate anions are viscous liquids at room temperature, those with octadecyldithiocarbamate groups are semi‐crystalline solids, exhibiting multiple thermal transitions between 0 °C and the temperature at which they become isotropic phases. The structural natures of those transitions have been characterized from analyses of data from differential scanning calorimetry, X‐ray diffraction, and rheology measurements. Among the interesting properties exhibited by the ionomers are strong adhesion to different surfaces, and high ultimate shear stress considering their relatively low amidinium contents.

Direct shear behavior of castellated dry RPC joints in precast concrete segmental bridges

Reactive power concrete (RPC) is advanced cementitious material. Precast RPC segmental bridges (PRSBs) have been popular in China. The shear behavior of the dry RPC joints between concrete segments in PRSBs was the most concerning issue. Ten push-off specimens were tested under direct shear with parameters of key number, confining stress, and steel fiber type. The cracking patterns, failure modes, and load–displacement curves of the dry RPC joints were obtained. Experimental analysis indicated that confining stress could significantly improve the cracking resistance and shear capacity of specimens, which the influence on three-keyed joints was higher than that of single-keyed joints and monolithic specimens. The normalized cracking shear stress and the normalized ultimate shear stress transferred across the keyed-joints decreased with the increasing of key numbers, but this effect was annihilated as the confining stress increased. The concrete strength could significantly affect the shear capacity of joints, where the shear strength of dry RPC joints was about 2.38 ~ 3.17 times that of dry normal concrete (NC) joints. The steel fiber type had a slight influence on the shear strength of dry RPC joints. According to the comparison between experimental results and predictions obtained by several typical formulae, the existing formulae could not well predict the shear capacity of dry RPC joints. A more accurate formula considering the tensile strength of concrete was proposed to predict the shear strength of the dry RPC joints in PRSBs, which the mean ratio of calculated value to test results was 0.995, and the standard deviation was 0.123.

Recommendation on block shear strength equation of double shear four-bolted connection in cold-formed mild carbon steel

In this study, experimental research was performed to investigate the structural behaviors such as the ultimate strength and fracture mode of double shear four-bolted connection fabricated with cold-formed mild carbon steel. It shows that bolted connections failed by either block shear fracture or net-section fracture at test end. Finite element (FE) analysis model was developed to replicate experimental response. After successful verification, it was employed for further analysis such as stress and strain distributions that could not be seen through the physical testing. Three paths on the plate model of bolted connection were established to investigate the critical shear plane and the shear stress distribution on the critical shear plane at ultimate state. A modified block shear fracture strength equation of the bolted connection was proposed considering the shear stress factor (average of ultimate shear stress and yield shear stress) at the critical shear failure plane (midway of gross shear section and net shear section; effective shear plane), and block shear fracture strengths by test and analysis results were compared with those by the suggested equation. It is concluded that the proposed equation is able to provide more accurate prediction in determining block shear strength of double shear four-bolted connection with mild carbon steel.

DEM-FDM numerical investigation on load transfer mechanism of GESC-supported embankment

This paper presents a numerical investigation on the load transfer mechanism of geosynthetic-encased stone column supported embankment. A coupled numerical model is developed by combining the discrete element method (DEM) with the finite difference method (FDM). A parametric study is then conducted on several governing factors such as the encasement length (Lenc), geosynthetic stiffness (J), the strength of foundation soil (cu), embankment height (Hemb), and area replacement ratio (αE). The predicted stress concentration ratio (SCR) under the embankment load is smaller than that under rigid loading (i.e., under the equal strain condition of the composite foundation). The predicted coefficient of the lateral pressure (Kps) lies between the coefficient of earth pressure at rest (K0) and the coefficient of passive earth pressure (Kp). Particularly, the bearing capacity of the GESC would be overestimated when substituting the confinement with Kp in the calculation. The shear stress at the column-soil interface (τcs) is less than the ultimate shear stress, and its development would be retarded with depth.

Laboratory modeling of deformation of specimens with discontinuity under direct shear in constant normal stiffness conditions

This study presents tests of specimens with discontinuity made of artificial geomaterial (concrete-sand mixture) having triangular profile of surface roughness under shear loading with the boundary “constant normal stiffness” condition, with three values of normal compressive load: 0.5, 0.9 and 1.2 MPa. The patterns of deformation were determined at each stage of loading diagrams: linear, nonlinear, peak load and residual strength. The empirical dependences of the ultimate shear stress on normal stress were constructed for different values of roughness.

Experimental and numerical study of the size effect on compound Meso/Microforming behaviors and performances for making bulk parts by directly using sheet metals

Meso/microforming of bulk multi-scaled parts and components by directly using sheet metals is an efficient approach to realizing mass production of meso-/micro-scaled bulk structures with good productivity and low cost. This process is promising with the large-scaled application potentials. In this unique deformation-based meso-/micro-scaled manufacturing, size effect arises due to the size scaling up and down of the extrinsic and intrinsic parameters of materials and forming systems, which further induces different mechanical responses and deformation behaviors in meso/microscale from those in macroscale. In this research, a compound microforming system for a blanking-heading process was developed to produce plug-shaped bulk parts by directly using copper sheets as a case study. Different punch-die clearances and grain sizes of specimen were employed to study the interactive effects of geometry and grain sizes on the microforming process and the micro-formed part. Through numerical simulations and experimental measurements of the final parts, the influences of size effect on microstructural evolution, geometrical precision and surface defects of the meso-/micro-formed parts and the load-stroke relationship were comprehensively investigated. The results reveal that when punch-die clearance equals grain size, the maximum ultimate shear stress of blanking and the highest burr are obtained. The larger grain size and punch-die clearance increase the material loss and reduce the bulge diameter of the produced parts. Three shear bands and three dead metal zones were identified on the cross-section of parts, and various defects including sunken area, pits, crack and surface damage were observed on the surface of the parts. These findings facilitate the production of plug-shaped microparts in the aspects of process monitoring and product qualities control and enrich the understanding of sheet-metal bulk forming in this progressive and compound meso/microforming.

Analysis of contact interaction of polymer honeycomb core and CFRP base layers in sandwich-core constructions

The article considers the challenge of studying the mechanical properties of composite sandwich constructions at the interface between the base layers and the lightweight core. The results of strength tests are presented for specimens of sandwich-core panels with coats made of high-strength carbon fiber-reinforced plastics (CFRP) and polymer honeycomb core considering various loading conditions. It is noted that a discrepancy in the values of shear stresses occurs in four-point bending and shear tests due to the complex stress-strain state of the specimens during bending. In order to interpret the experimental data, numerical analysis of the area of contact interaction between the coats and the filler of the sandwich-core composite structures is carried out. It is noted that in the presence of significant normal stresses in the adhesive coat the base layers separate from the core during shear tests and there is underestimation of the values of shear stresses by about 20%. Recommendations for the assignment of ultimate shear stresses for the use in practical design of sandwich-core composite constructions are put forward.

Shear-friction behavior of concrete-to-concrete interface under direct shear load

Shear transfer at concrete-to-concrete interfaces under direct shear is of great significance to the performance of concrete structures. In this study, a series of direct shear specimens with concrete-to-concrete interfaces were designed by considering the normal pressure, longitudinal reinforcement, and coupling effects. Adding reinforcement or normal pressure increased the interface cracking stress, ultimate shear strength, and residual shear strength, and changed the brittle behavior of the bonding interface to a gradual strength degradation mode. However, an increase in the normal pressure from 4 to 8 MPa only slightly improved the elastic stiffness and plastic ductility of the direct shear specimens. Furthermore, comparing the observed ultimate strengths with the calculated ultimate strengths of three models in main codes, it was shown that all calculated strengths were conservative. During the shear-slip process, among cohesion, friction, and dowel action, the friction was the most affected property during the direct shear process. In the final residual stage, the ratios of cohesion, friction, and dowel action were found to be similar, and no significant relationship was observed between the longitudinal reinforcement and normal pressure before the ultimate shear stress was reached. However, after the ultimate shear stress was reached, the interaction was found to improve the shear resistance at the concrete-to-concrete interface, thereby improving the ductility and interface shear performance.

Effects of Build Orientation on Mechanical Properties of Fused Deposition Modeling Parts

Our aim was to further analyze the effect of print orientation on the mechanical properties of FDM parts and explore the failure modes of differently oriented printed parts using scanning electron microscopy. We compared 3D printed ABSplus (P430) FDM parts in tension, bending, and torsion printed in flat, edge, and vertical orientations to machined equivalent parts. Parts were printed on a Stratasys uPrint SE in orientations according to ISO/ASTM 52921:2013(E) and evaluated using ASTM standards. Tensile, torsion and bending results are reported. Printed part properties were in many cases significantly different from machined part properties. For example, when subjected to tensile testing, the edgewise print orientation produced both the highest elastic modulus and the highest ultimate tensile strength of the 3D printed parts. During flexural testing, the flatwise orientation produced the highest ultimate stress at 54.31 MPa, while the edgewise elongation at break was the highest at 8.7%. However, unlike what was observed in the tensile and flexural tests, torsion samples printed in the angled, vertical, and horizontal orientations did not fail at significantly different ultimate shear stress values. Scanning electron microscopy work revealed that fracture propagation and failure modes are significantly different between the various print orientations with fractures through filaments giving superior strength.

Experimental Study of Adobe Masonry and its Adherence with Reinforced Concrete Confinement Elements

The constructions with adobe masonry confined with concrete elements, experience a separation between them, mainly due to the inherent physical and chemical characteristics of both materials that are not very compatible with each other; adobe, a raw masonry with a high clay content, undergoes changes in its shape in the presence of humidity and temperature variation, which affects its adherence to concrete elements, compromising the confinement, function and stability of the walls. The different coefficients of expansion and contraction between concrete and adobe, added to their physical properties, make it difficult to achieve adequate adherence between these two materials. In the present study, 6 mixtures of earth (adobe) were designed, with different granulometry proportions to measure the adherence between adobe and concrete, identifying the most suitable one with the purpose of using it as a bonding material in walls for houses, from this study, with the best response being the sample MA-3. The test methodology was based on standards applicable to concrete and annealed brick masonry, as there is no available one for this material. Thirty-six adobe specimens adhered to concrete were tested, to which a normal load was gradually applied to their cross section, to a piece of adobe between two pieces of concrete, recording the ultimate horizontal shear stress between both materials. The scope is considered the result of the test of adobe pieces adhered to concrete subjected to horizontal shear force, considering different granulometry in the composition of the adobe mixture. This work provides a starting point for the standardization of the test and the justification of the need for an additional element that contributes to the confinement.

Dynamic behavior of natural sand soils and fiber reinforced soils in heavy-haul railway embankment under multistage cyclic loading

In this study, dynamic triaxial tests of natural sand soils and fiber reinforced soils were conducted. The influence of loading frequency, water content, and compaction degree on the dynamic shear modulus and damping ratio of natural soils were identified. Different fiber length, confining pressure, and fiber content were studied to gain the dynamic characteristics of fiber reinforced soils. The results show that the water content and compaction degree has a significant effect on the dynamic behavior of natural soils, and confining pressure and fiber content has a visible reinforcement effect on the dynamic characteristic of fiber reinforced soils. The empirical formulas of maximum dynamic shear modulus (Gd max), ultimate shear stress (τdult), and damping ratio (λ) were generate, which can provide references for fiber reinforced soil design.

Investigation of properties, structural links and structure of dispersed systems from coal sludges

Goal. Investigate the mineral composition of coal sludge and determine its effect on the properties, structural bonds and structure of dispersed systems from them. The research technique consists in the application of methods for measuring the structural and mechanical properties of dispersed systems. To assess the characteristics of the mechanical properties of structured dispersed systems, the most rational methods are to determine their deformation properties: strength - ultimate shear stress, modulus of elasticity and relaxation characteristics. Macroscopic and optical methods were used to study the mineral composition of sludges from coal concentrators. Results of the research. The study of coal industry waste as dispersed systems is performed. The factors and structured structure that influence the technological processes in the processing of coal sludge and the application of the method of electrokinetic lumping are analyzed. The mineral composition of waste - dispersed systems is determined. It is established that the main factors determining the structural and rheological properties of dispersed systems include: adhesion force in the contacts between particles, coordination number, concentration of the dispersed phase in the dispersion medium, dispersion and particle size distribution. It is proved that the main factor that determines the interaction of dispersed systems is the presence of adsorption balls of surfactants. Scientific novelty. An inseparable connection between dispersed systems and surface phenomena, as well as the kinetics of electrochemical processes on interfacial surfaces, microheterogeneity, sorption and ion exchange processes in ultramicroporous systems has been established. Practical meaning. Technological parameters of processes and ways of perspective treatment of wastes of coal concentrators as dispersed systems at their processing and use as additional power resources are substantiated.

Shear friction capacity of self-consolidating concrete

Abstract An experimental research was developed to evaluate shear transfer in self-consolidating. Three concrete mixes were prepared, one conventional and two self-consolidating, differing on the proportion of the coarse and fine aggregate used. Nine push-off specimens, containing steel reinforcement passing through the shear plane, were tested, to evaluate the ultimate shear stress and shear plane displacements. Shear strength of self-consolidating concrete specimens were higher than conventionally vibrated concrete. The experimental results were compared to the shear strength estimated by literature and code based equations, yielding conservative results of these equations for both types of concrete, especially the models that disregard the compressive strength of concretes.

Shear Behavior of High Strength Self-Compacting Concrete with Lower Transverse Reinforcement Index

ABSTRACT Self-Compacting Concrete (SCC) generally has lesser coarse aggregate contents and also the maximum size of aggregates is limited as compared to Normal Vibrating Concrete (NVC) for the same class of strength. This results in reduced aggregate interlock in Self-Compacting concrete as against NVC, which affects the shear strength of slender beams and thus, SCC might have lower shear strength. In this article, an experimental programme which includes six slender beams of High-Strength Self Compacting Concrete (HSSCC) with compressive strength more of than 90 MPa and with different stirrup spacing is presented. Experimental test results of shear strength of HSSCC beams are compared with high strength NVC beams for different stirrups spacing. The results showed the ultimate shear stress of HSSCC beams is lower than NVC beams and increase in transverse reinforcement index, ρw fy, in HSSCC beams decreases this difference. The results are also compared with different code provisions. Not much work has been done on beams with lower transverse reinforcement index (ρw fy) and in the present work, ρw fy ranges between 0.276 to 0.80.

Effects of Microbial Transglutaminase on Technological, Rheological, and Microstructural Indicators of Minced Meat with the Addition of Plant Raw Materials.

The aim of the study was to analyse the effects of transglutaminase on the physicochemical, technological, rheological, and microstructural indicators of minced meat with the addition of plant raw materials. The formulations of minced meat from beef trimming, hemp protein, and flax flour were optimized in terms of biological value and optimal content of essential amino acids. The addition of plant components in amounts greater than 18% caused an increase in the content of protein, fat, and ash in the minced samples. The rheological properties of minced meat samples without enzyme treatment changed depending on the proportion of plant raw materials. When the content of the flax flour was increased, the minimum ultimate shear stress and viscosity were observed, while the maximum values for these indicators were achieved in samples containing about 15% hemp protein, as well as in samples without plant additives. When adding transglutaminase to the formulation, increases in the ultimate shear stress and viscosity were proven for all combined minced samples. The combined minces, containing flax flour, had a more plastic structure and the lowest modulus of elasticity, while minces including 14% hemp protein or more than 87% meat components were identical to the control samples in terms of deformation and elasticity. In enzyme-treated minces, the plasticity of the samples reduced while density and elasticity increased. Transglutaminase treatment contributed to the formation of optimal technological properties of combined minces. Microstructural analysis showed the intermolecular bonds between protein particles in combined minced samples with the addition of enzymes. The research results have demonstrated the effectiveness of using transglutaminase in the composition of combined minced meat for the formation of a homogeneous and dense system with the necessary technological and rheological properties.

Torque at elastic-plastic torsion of sheet-straightening machines’ steel shafts

The experiments on the torsion of the steel shaft were conducted on the machine Instron 55MT2 with a maximum torque of 220 N×m and a mass of 2500 N. The ends of the shaft clamped with collet-chucks. For the torsion we used the round cylindrical samples from a low-carbon steel with the Young’s modulus of 2×1011 Pa, the shear modulus of 7.752×1010 Pa, the Poisson’s ratio of 0.29, the yield strength of 524 MPa, the yield strength at shift of 302 MPa, the ultimate shear stress of 352 MPa, the ultimate shift of 0.18 and the plastic module at shift of 740 MPa. The torsion of the steel shafts and thick-walled pipes is widely used in the metallurgy, mechanical engineering and oilgas industry. For example, the shafts’ torsion is observed in the drive mechanisms of the sheet-straightening machines for the thin and thick steel sheets, in the rolling mills for the cold and hot steel sheets, in the drives of the rear wheels of motor transport, in the land and sea gas-oil drilling platforms and so on. Under the significant torque, the steel shafts can experience not only elastic, but also plastic deformation without the destruction. The experimental dependence of the shaft torque on the twisting angle gives researchers much more information about the mechanical properties of steel than the analogous experiments on the rupture of the steel shafts, since there is no neck formation during the torsion and the steel shaft does not collapse even at the very large twisting angles. The classical Ludwik’s and Nadai’s approximations for shear do not sufficiently accurately describe the shear deformation and are, therefore, not sufficiently effective for calculating the shaft torque. Therefore, the more accurate the straight and back Shinkin’s approximations are used below to describe the shear deformation. A special feature of calculating the dependence of the shaft torque on the shear angle is that the torque is calculated approximately as a power series, since the corresponding integrals are transcendental (cannot be calculated analytically). At the same time, the relative accuracy of the torque calculation is very high (about 10-6 %).