Academic literature on the topic 'Stress transferring mechanism'

This research focuses on the interface’s impact on the macro-mechanics and damage mechanism of the fiber reinforced concrete (FRC). In consideration of the mesoscopic nonhomogeneity of the interface, numerical test has been adopted to simulate failure procedure of fiber reinforced concrete samples. It can, therefore, be concluded, that, the interface elastic modulus have a great impact on the macro-mechanics of the FRC. With interfaces added into FRC, failure could present ductile properties, cracks could be developed horizontally, and then unbonded and slid along the interface. During the process, phenomenons such as interface debonding and sliding, crack deflection, fiber bridging and pulling out could be clearly observed. Under With the premise that strength for interface is adequate for stress transferring, the toughness of the FRC would be enhanced by the interface.

Study the existing advancing mechanism of drill, analyze the disadvantage of the flat key and the spline, and the feature of the three circular arc equidistant profile connection. Taking the common chain advancing mechanism as basis, using three circular arc equidistant curve to make sprocket bore and intermediate shaft external cylindrical fit constitute the three circular arc equidistant profile keyless connection. Then introduce the advancing mechanism with three circular arc equidistant profile connection of drill. Applying Solidworks2010, we created the three-dimensional modeling of the mechanism, which lay the foundation for the further research and application. The new type advancing mechanism has many advantages, such as automatic-centering accurately, convenient in assembling and disassembling, eliminating the stress concentration, simplicity of the fit section，transferring bigger torque, suitable for heavy-loaded rock drill machine.

The computer-aided design method is used in modeling for the interaction between pile and geotechnical material soil. The behavior of the shear coupling springs is identical to the shear behavior of a grouted cable. Then a numerical model is founded by FLAC3D, deformation and stress responses are obtained as well as the mechanical response of pile during calculation, whose result reveals the mechanism of pile with soil under the load of gravitation and load transferring mode along pile shaft for different ground surface surcharge load, during simulation, the soil consists of two types, the less consolidated soil and normal consolidated soil, both the negative skin friction stress and positive skin friction stress are studied.

For discussing the mechanism of load-transferring for reinforced steel fiber reinforced concrete (SFRC) double-column combined six-pile caps, the large-scale general finite element software-ABAQUS is used for the tested SFRC caps with computing in the aspects of modeling, cracking load, limit load, load-deformation curve, distribution of stress in caps and cracks and etc. The results of computing is compared with the result of experiments and the comparison is indicated: The results of computing and experiments are coincided well; The destroy pattern of SFRC double-column combined six-pile caps is sheared damage or punched damage and the model of load-transferring accords with spatial strut-and-tie method (STM); The mixture of steel fiber can improve cracking load and limit load for RC caps, delay the crack for caps, block the cracks’ expansion, and enhance the cap’s ductility.

Casuarina glauca is an important coastal protection forest species, which is exposed to high salt stress all year round. Arbuscular mycorrhizal fungi (AMF) can promote the growth and salt tolerance of C. glauca under salt stress. However, the effects of AMF on the distribution of Na+ and Cl− and the expression of related genes in C. glauca under salt stress need to be further explored. This study explored the effects of Rhizophagus irregularis on plant biomass, the distribution of Na+ and Cl−, and the expression of related genes in C. glauca under NaCl stress through pot simulation experiments. The results revealed that the mechanisms of Na+ and Cl− transport of C. glauca under NaCl stress were different. C. glauca took a salt accumulation approach to Na+, transferring Na+ from roots to shoots. Salt accumulation of Na+ promoted by AMF was associated with CgNHX7. The transport mechanism of C. glauca to Cl− might involve salt exclusion rather than salt accumulation, and Cl− was no longer transferred to shoots in large quantities but started to accumulate in roots. However, AMF alleviated Na+ and Cl− stress by similar mechanisms. AMF could promote salt dilution of C. glauca by increasing biomass and the content of K+, compartmentalizing Na+ and Cl− in vacuoles. These processes were associated with the expression of CgNHX1, CgNHX2-1, CgCLCD, CgCLCF, and CgCLCG. Our study will provide a theoretical basis for the application of AMF to improve salt tolerance in plants.

Drought and salinity are major constraints to agriculture. In this review, we present an overview of the global situation and the consequences of drought and salt stress connected to climatic changes. We provide a list of possible genetic resources as sources of resistance or tolerant traits, together with the previous studies that focused on transferring genes from the germplasm to cultivated varieties. We explained the morphological and physiological aspects connected to hydric stresses, described the mechanisms that induce tolerance, and discussed the results of the main studies. Finally, we described more than 100 genes associated with tolerance to hydric stresses in the Triticeae. These were divided in agreement with their main function into osmotic adjustment and ionic and redox homeostasis. The understanding of a given gene function and expression pattern according to hydric stress is particularly important for the efficient selection of new tolerant genotypes in classical breeding. For this reason, the current review provides a crucial reference for future studies on the mechanism involved in hydric stress tolerance and the use of these genes in mark assistance selection (MAS) to select the wheat germplasm to face the climatic changes.

The tensile failure mechanism of carbon–aramid hybrid fibers/epoxy sandwich structure laminates was investigated by using experimental and finite element methods. Double curing agents, triarylsulfonium hexafluoroantimonates and triethylene tetramine with a mass ratio of 4:15 were introduced into the laminates. Sandwich structure laminates, with different proportions of hybrid fibers, were cured by UV-initiated anion/cationic dual curing technique. The results showed that the synergetic curing effects of two curing agents were observed under UV irradiation, leading to the better curing of the system, which further plays a positive influence on the mechanical performance. The tensile properties and failure mechanism of the laminates depended on the stacking sequence and fiber volume fractions of the layer structures. The interplay hybrid laminates, containing three alternate plies with fiber contents of 67.7 vol%, presented the optimal tensile performance, and its tensile strength and modulus were 0.82 GPa and 22.09 GPa, respectively. The fracture morphologies revealed that pull-out and debonding of fibers were the main failure mechanism of hybrid laminates. The performance of sandwich structure laminates was determined by the load-carrying capacity of carbon fiber and load-transferring capacity of the aramid fiber and adhesive. The finite element model based on experiments was established to simulate the stress state and failure mechanism of sandwich laminates. The results demonstrated that the stress was better transferred into carbon fibers from the aramid fibers and adhesive, and the relative error rate of maximum stress from finite element analysis and experimental results was less than 5%, which were in reasonable agreement with the experimental results.

The purpose of the present dissertation is the study of the shear behavior of the so-called, in the recent scientific literature, Hybrid Steel Trussed Concrete Beams (HSTCBs). Such beams represent a structural typology which usually consists of a steel truss embedded into a concrete core so that, after curing and maturation, the two materials behave as a unique structural system, the steel members working as the reinforcement of the beam itself. Since the Seventies, the HSTCBs are widely employed in civil constructions because they allow to industrialize the building process, avoiding substantial alterations in the construction processes and organizational protocols of the industries. With regard to the introduction of this beam typology within seismic framed structures, it is necessary to develop specific design criteria based on the capacity design approach, ensuring both an adequate shear resistance in order to prevent brittle failure modes and a cyclic dissipative behavior of beam-to-column joints. While the issues concerning the flexural behavior has been widely investigated in the literature, particularly focusing on the connection deformability and strength, the problems related to the shear behavior still represent an open issue. Within this framework, the present thesis aims at investigating the shear response of HSTCBs and the stress transfer mechanism between the steel members and the surrounding concrete. With reference to the stress transfer mechanisms, theoretical analyses with the aim of interpreting the experimental results of push-out tests on pieces of HSTCBs are developed. Such models for the prediction of the maximum slip force refer both to the classical truss models with variable inclination of the compressed concrete strut, typically adopted for the classical Reinforced Concrete (R.C.) structures, and models with a failure mechanism governed by the dowel effect, generally used for composite structures. The application of these models, according to their original formulation, generally leads to an underestimation of the maximum load experimentally obtained by various authors from the push-out tests. For this reason, the formulation of further strut and tie models, on one hand, and dowel-mechanism models, on the other hand, has been developed. In those models proper changes have been introduced in order to take into account the geometrical and mechanical characteristics of the beam object of study. Besides the analytical interpretation of the maximum load obtained in the push-out tests, a two-dimensional (2D) non-linear finite element (FE) model is also developed with the aim to simulate, under few simplified hypotheses, the mechanical response of the beam identifying the stresses transfer mechanisms. The result of the 2D modeling highlights the difficulty of grasping, with an extremely simplified model, the large variety of parameters on which the transferring of the stresses and the failure modes depend. Among these parameters, the ones playing a preeminent role are the three-dimensional (3D) geometry and the actual bond between the surfaces of the steel bars (smooth or ribbed) and the concrete in which they are embedded. Therefore, after the developing of the simplified modeling, a detailed 3D FE model containing solid elements is realized by means of the software Abaqus 6.10. The model was developed in collaboration with the research group of Prof. Gianvittorio Rizzano of the Department of Civil Engineering, University of Salerno. Particularly, the developed models are representative, on one hand, of cases in which the diagonals of the steel truss are ribbed and, on the other hand, cases in which they are made up of smooth steel. The simulation concern cases in which the hypothesis of perfect bond between the surfaces is assumed or, similarly, cases in which there is no bond between the steel and the concrete as well as the more realistic case in which a specific bond stress-slip relationship at the interface is introduced. Besides the modeling of the experimental tests, also a parametric numerical analysis is provided with the aim of evaluating the influence of the geometrical and mechanical features of the various components of the HSTCB, such as the deformability of the bottom steel plate, the type of steel constituting the diagonal web bars (smooth or ribbed) as well as the mechanical characteristics of the materials. In addition to the study of the local problems of stresses transfer, some theoretical and experimental studies are carried out in order to investigate the global behavior of the structural elements. In particular, an experimental campaign is performed on simply supported HSTCB specimens loaded with a concentrated force in the midspan and designed to exhibit a shear failure. For the execution of the tests, a particular type of steel truss produced by the industry Sicilferro Torrenovese Torrenova (ME) is employed. Six specimens have been manufactured and classified into two series, "A" and "B". Particularly, the specimens of series "A" have been tested inducing a positive bending moment; on the contrary, the specimens of series "B" have been tested so that a negative bending moment arises. Before the concrete casting, electric strain gauges have been placed on the specimens in correspondence of the tensile and compressed diagonal bars (in the section near the welding to the inferior plate) and in the bar of the upper chord in correspondence with the central mesh of the truss in the shear span. After casting and curing of the concrete, strain gauges were placed even on the bottom steel plate. The obtained experimental results are compared with the detailed numerical FE model representative of the abovementioned tests, showing a good agreement in terms of load-displacement curve as well as crack pattern evolution. The numerical analysis is followed by the analytical interpretation for the assessment of the shear strength of the beams. In the first instance, the prediction models existing in the literature and typically employed for the classic R.C. structures have been applied. They can be mainly classified into "additive models" and "strut and tie models". In the additive models the value of shear strength is calculated as the sum of the contribution due to the concrete and the additional contribution provided by the shear reinforcement. The strut and tie models, instead, are primarily truss models in which the hypothesis of the variable inclination or 45° inclination of the compressed concrete strut is assumed. In addition to these classical formulations, also other computational models recently developed by some authors for the HSTCBs are taken into account. Successively, also a specific model able to interpret the shear strength mechanism in the tested beam typology is proposed. Considering the three-point bending tests performed on the HSTCBs, a further 3D model, realized with the software Abaqus 6.11, is developed in a simplified way, with the aim of managing a model sufficiently accurate in the estimation of the maximum load that, in the same time, would allow computational efforts appropriate for the generation of a certain number of different cases for the study of the size effect on beams with similar geometry. The model has been developed under the guide of Professors Roberto Ballarini and Jialiang Le of the Department of Civil Engineering, University of Minnesota. Starting from specific scaling criteria, three different sizes of beams are considered and the numerical load-displacement curve is obtained also interpreting the failure mechanisms and the evolution of the cracks. The numerical analyses have been developed with the aid of computers and software provided by the Minnesota Supercomputing Institute.

In PVP2011-57942 we reported improved endurance in fatigue tests with intermediate annealing to roughly simulate steady state operation between fatigue transients in NPP components. Quantification of this effect is in focus of our continued research on fatigue performance of niobium stabilized stainless steel (1.4550, X6CrNiNb1810mod). Similar effect is expected in nuclear power plants during normal operation — e.g. in a PWR surge line or in pressurizer spray lines. Holds affect cyclic stress strain response. Stress amplitude, tensile mean stress and apparent elastic modulus are increased immediately after a hold, while decreased by cycles in between. Axial shortening is measured during hot holds at zero stress. This all suggest cyclic accumulation of lattice defects and recovery during holds. Recovery may occur through thermally activated dislocation migration together with diffusion, grouping and annihilation of lattice defects. More than one thermally activated processes control the rates of contraction during hold periods at elevated temperatures. Hold hardening delays crack formation by preventing plastic strain localization, in components also on macroscopic level. A mechanism informed model is sought for transferring laboratory data to real plant components in terms of improving accuracy of numerical fatigue usage assessment. Anticipated mechanisms behind gradual changes in material responses are discussed in relation to quantitative effects of holds.

Rock at depth is subjected to stresses resulting from the weight of the overlying strata. When an underground opening is excavated, the stress field in this rock mass is locally disrupted and induces a new set of stresses surrounding the new opening. At tunnel and cavern associated junctions, the re-distributed stresses will alter the stress fields of adjacent openings. For example, loadings from a taller cavern will be transferred through the rock arch and concentrated as additional vertical stress above the crown of the shorter cavern. The load transferring mechanisms in this paper refer to the construction of the cavern complex, which involves developing new sewage treatment works in caverns to be constructed at Nui Po Shan, A Kung Kok, Sha Tin, to replace the existing Sha Tin Sewage Treatment Works (STSTW). Upon functioning of the new STSTW, the existing site will be released for other uses beneficial to the development of Hong Kong.The works at the new STSTW occupies about 14 hectares in the area comprising of Main Access Tunnel (MAT), Secondary Access Tunnel (SAT), fifteen Process Caverns, the Main Driveway (MD), Secondary Driveway (SD), four Branch Driveways, Ventilation Shaft, Ventilation Adit, two Effluent Pipelines, and lining and portal structure of MAT and SAT. These structures are excavated mainly by the drill-and-blast method in hard rock, with rock covering more than half of the excavation span/height above the crown. They are designed as drained and are primarily supported by the rock arch, reinforced by systematic permanent rock bolts with permanent sprayed concrete. In addition, drained cast-in-situ reinforced concrete lining is proposed for poor ground conditions.For the proposed cavern complex, most of the Branch Driveways are taller than Process Caverns and MD/SD except for the middle cavern for sludge treatment (STC) purposes. STC's design span and height are 30 m and 35 m, respectively. Therefore, additional stresses are expected to transfer from Branch Driveways and STC to other Process Caverns and MD/SD. Numerical modeling using finite element methods has been established, where two-dimensional design models and three-dimensional verification models in accordance with the varying excavation profiles, overburden depth, and rock mass quality have been carried out. By observing the stress redistribution from the taller STC to other Process Caverns, the two-dimensional and three-dimensional models aim to study the stress concentration zones and the extent of the influence zone at tunnel and cavern associated junctions. The maximum deformation is located along with the crown of STC and intruding corners at the associated junctions, in which the Process Caverns with the largest excavation span and height are proposed.This paper provided a detailed description of the geology, cavern complex geometrical arrangements, rock mass properties for the modeling, methodology of modeling, and mechanism of load redistribution observed at the junctions.

Structural integrity of spent fuel racks is a critical safety issue in nuclear power stations. The standard approach of evaluating the effects of an impact projectile on a submerged structure, which constitute the start point of the current study, involves three main steps: determination of the conditions just prior to the impact (that are considered as initial conditions for the analysis), setting the mechanism of transferring energy from the projectile to the target structure, and determining how that energy is absorbed by the impacted structure. Usually, the dynamics of the projectile are ideally considered, the influence of the fluid presence is restricted to the determination of the impact velocity and strain rate dependency is limited to choosing a true stress vs. strain curve corresponding to some constant strain rate. Starting from the standard engineering approach, the authors have refined the model considering more realistic dynamics of the projectile, extending the influence of the fluid to the entire analysis and using a more accurate strain rate dependant material behavior. Explicit Finite Element analyses are used in order to incorporate the desired effects.

For the joints composed of steel beams and reinforced concrete columns, shear failure and bearing failure are the key failure modes. The shear failure indicates stable hysteresis loop without the strength degradation. On the other hand, the bearing failure mode indicates large pinching and strength degration after the attainment of the maximum load.Accordingly, bearing failure in the joints should not be caused in RCS system.To improve the bearing failure behavior of S beam - RC column joint, joint details using perfobond plate connectors were proposed. Perfobond plate connectors were attached on the upper and bottom flanges at right angles to the steel flange. The objective of this study is to clarify the effectiveness of proposed joints details experimentally and theoretically.Six specimens were tested. All specimens were T-shaped planar beam - column joints with 350mm square RC column and S beams with the width of 125mm and the depth of 300mm. The beams were all continuous through the column.Perfobond plate connectors were attached on the bottom flanges at right angles to the steel flange.Three holes were set up in the perfobond plate connectors. The experimental variable was the transverse reinforcement ratio of the joints. The transverse reinforcement ratio of the joints was 0.181% and 0.815%. For each transverse reinforcement ratio of the joints, specimen without the perfobond plate connectors, specimen with the perfobond plate connectors and specimen with the reinforcing bar inserted the hole of perfobond plate connectors were planned.For all specimens, the hysteresis loop showed the reversed S-shape. However, energy dissipation for specimens for specimens with perfobond plate connectors was larger than of specimen without perfobond plate connectors. Bearing strength of specimens with perfobond plate connectors was larger than that of specimen without perfobond plate connectors. From the test results, shear strength of concrete connector a hole was 0.7 times compression strength of concrete.On the other hand, shear strength of inserted reinforcing bar was 1.25 times shear strength of reinforcing bar.Based on the stress transferring mechanism and resistance mechanism of joints proposed by authors, the design formulae of joints with perfobond plate connectors were proposed.The predictions were shown to be in good agreement with the test results.

Abstract. Cyclic strength is essential in many lightweight design concepts where the design is to be pushed to the limits of strength. While joining dissimilar metals such as aluminum and steel is a challenge of its own, fatigue life prediction for this joining type is all the more challenging. Here, clinching as a mechanical joining process offers many advantages. However, a generalized evaluation of the fatigue properties is complex since many influencing factors, such as the joint's geometry, the high plastic deformation, the proportion of bonding mechanisms, have to be considered. Force versus number of cycles (F-N) curves are the established basis to describe the fatigue behavior of clinch joints. However, a generalized evaluation of the service life requires stress versus number of cycles (S-N) curves. This research gives a first approach to transferring F-N curves to S-N curves on the basis of nominal stress determination in the damage relevant clinch cross section. The material combination used, EN AW-6014 and HCT590, offers excellent practical relevance since both materials are widely used in the automotive industry.

Silicon carbide (SiC) and SiC matrix composites (SiCf/SiC) are being investigated as potential fuel cladding materials for advanced PWRs in order to improve the safety of nuclear power plants. The conceptual design of multi-layered SiC cladding (consisting of a monolithic SiC layer, SiCf/SiC composite layer and a monolithic SiC coating layer) has been investigated to meet the fuel requirements of both the strength and impermeability. A stress distribution model of the triple-layered SiC is developed on the basis of the theory of thermo-elasticity mechanics, taking radial temperature gradient and swelling effects into account as well. The heat transferring behavior of the cladding is investigated by analyzing the temperature distribution under steady conditions. Finite Element Analysis (FEA) code ANSYS is used to obtain the stress and temperature nephogram of multi-layered SiC fuel cladding under simulated steady conditions. Compared with the results of ANSYS, the stress distribution model and temperature distribution is validated.

This paper investigates the nature of the contact between the load transferring surfaces in the roller screw mechanism, i.e., between the screw and roller threads and between the nut and roller threads. The analysis is applied to both planetary roller screws and recirculating roller screws. Prior work has neglected to take a fundamental approach toward understanding the mechanics of the contact between these components, and as a consequence, detailed analysis of aspects such as contact mechanics, friction, lubrication, and wear are not carried out correctly. Accordingly, in this paper, the principle of conjugate surfaces is used to establish contact at the screw-roller and nut-roller interfaces. The in-plane angles to the contact points are derived and it is shown that for the screw-roller interface, the contact point cannot lie on the bodies’ line of centers as has been the assumption in previous papers. Then, based on the curved profile of the roller thread, the radii of contact on the roller, screw, and nut bodies are also derived. Knowledge of the contact point locations is necessary to understand the interaction forces between the key components of the roller screw mechanism. In addition, accurate estimates of the radii of contact are necessary for minimizing the phenomenon of roller migration, a condition that can cause binding between components and eventually lead to the destruction of the mechanism. Last, the principal radii of curvature at the contact points and the angle between the principal axes are derived. These are essential for further development of the contact mechanics, such as the surface stresses, deformations, and consideration of wear.

Abstract Little is known about the contributions of specific extracellular matrix components of tendon to the tissue’s mechanical properties. Type I collagen, given its abundance and association into long fibrils, is thought to dominate the elastic properties of tendon. Proteoglycans (PGs) are believed to provide elasticity through their potential role in transferring stress between discontinuous fibrils, as well as viscoelasticity via their interaction with water. Previous studies suggest relationships between collagen or PGs and tissue mechanics [1,2]. However, no study to date has isolated the contributions that distinct tendon components make to the elastic and viscoelastic properties of tendon. Recently, transgenic mice with prescribed mutations or deletions of various genes for specific tendon constituents have become available. In this study, we use transgenic mice as a tool to investigate the contributions of tendon components to tendon function based on a previously described approach [3]. In particular, we compare the strain rate sensitivity among fascicles from the tails of mice described in Table 1. We hypothesize that (a) fascicles with alterations in type I collagen (C1TJ8 and C1M8) will have different elastic properties but no difference in strain rate sensitivity than age-matched controls (CTL8), and (b) fascicles with alterations in proteoglycan (DKO8 and CTL3 [4]) will have different elastic properties and different strain rate sensitivity than CTL8 fascicles.

As a promising composite structure, gangue concrete filled steel tubular (GCFST) column exhibites favarable characteristics including high strength and economic efficiency. This paper conducted numerical investiagations on structural behavior of a ring-beam connection to GCFST column with concrete beam under cyclic loading. Furthermore, finite element models of column-beam connections were developed using ABAQUS and validated against full-scale experimental tests to identify accuracy of selected modeling approaches. Using these validated models, stress distribution of each component was examined to study the force-transferring mechanism among the components and failure modes of the ring-beam connection. Research study indicated that the ring-beam connection showed a reasonable force-transferring mechanism under cyclic loading and the remarkable earthquake-resistant performance with high capacity and acceptable ductility. Finally, parametric studies were performed to assess the influences of beam-to-column stiffness ratio,steel ratio, axial load level, and concrete compressive strength on connection cyclic behaviors. Parametric studies provided some suggestions and references for the application of the ring-beam connection in various engineering projects.