Theoretical study of the prestressing strand's stress by computer modeling methods

2020 ◽  
Vol 76 (11) ◽  
pp. 1139-1148
Author(s):  
A. G. Korchunov ◽  
E. M. Medvedeva ◽  
E. M. Golubchik
Keyword(s):  
Residual Stresses ◽  
High Strength ◽  
Pearlitic Steel ◽  
Internal Stresses ◽  
Steel Microstructure ◽  
Compressive Stresses ◽  
Wide Range ◽  
Prestressing Strands ◽  
Increasing Temperature ◽  
Wire Strand

The modern construction industry widely uses reinforced concrete structures, where high-strength prestressing strands are used. Key parameters determining strength and relaxation resistance are a steel microstructure and internal stresses. The aim of the work was a computer research of a stage-by-stage formation of internal stresses during production of prestressing strands of structure 1х7(1+6), 12.5 mm diameter, 1770 MPa strength grade, made of pearlitic steel, as well as study of various modes of mechanical and thermal treatment (MTT) influence on their distribution. To study the effect of every strand manufacturing operation on internal stresses of its wires, the authors developed three models: stranding and reducing a 7-wire strand; straightening of a laid strand, stranding and MTT of a 7-wire strand. It was shown that absolute values of residual stresses and their distribution in a wire used for strands of a specified structure significantly influence performance properties of strands. The use of MTT makes it possible to control in a wide range a redistribution of residual stresses in steel resulting from drawing and strand laying processes. It was established that during drawing of up to 80% degree, compressive stresses of 1100-1200 MPa degree are generated in the central layers of wire. The residual stresses on the wire surface accounted for 450-500 MPa and were tension in nature. The tension within a range of 70 kN to 82 kN combined with a temperature range of 360-380°С contributes to a two-fold decrease in residual stresses both in the central and surface layers of wire. When increasing temperature up to 400°С and maintaining the tension, it is possible to achieve maximum balance of residual stresses. Stranding stresses, whose high values entail failure of lay length and geometry of the studied strand may be fully eliminated only at tension of 82 kN and temperature of 400°С. Otherwise, stranding stresses result in opening of strands.

scholarly journals Analysis of the Bauschinger Effect in Cold Drawn Pearlitic Steels

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 114
Author(s):  
Jesús Toribio ◽  
Viktor Kharin ◽  
Francisco-Javier Ayaso ◽  
Miguel Lorenzo ◽  
Beatriz González ◽  
...  
Keyword(s):  
Mechanical Behaviour ◽  
Bauschinger Effect ◽  
High Strength ◽  
Pearlitic Steel ◽  
Internal Stresses ◽  
Compression Load ◽  
Prestressing Steel ◽  
Hardening Rule ◽  
Steel Wires ◽  
Cyclic Tension

Prestressing steel wires usually undergo cyclic loading in service. Therefore, it is of interest to analyse certain features of their mechanical behaviour under this type of loading, such as the Bauschinger effect (BE) or the hardening rule, that fit the real mechanical behaviour appropriately. In this study, different samples of high strength pearlitic steel wires were subjected to cyclic tension-compression load exceeding the material yield strength, thus generating plastic strains. From the experimental results, various parameters were obtained revealing that analysed steels exhibited the so-called Masing type BE. In addition, the variation of the BE characteristics (of the effective and internal stresses) with the applied plastic pre-strain indicated that the studied materials followed a mixed strain hardening rule with the domination of the kinematic component.

scholarly journals Relaxation patterns of technological residual voltage in the surface layer of high-strength steel when cyclically loaded

2021 ◽  
Vol 244 ◽  
pp. 04001
Author(s):  
Georgi Kravchenko ◽  
Konstantin Kravchenko ◽  
Andrey Smolyaninov ◽  
Irina Kudryavtseva
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Construction Materials ◽  
High Strength ◽  
Surface Plastic Deformation ◽  
Variable Pressure ◽  
Surface Plastic ◽  
Initial Value ◽  
Residual Voltage ◽  
Compressive Stresses

Experimentally investigated patterns of changes in technological residual stresses under the influence of variable pressure in the surface layer became 30XNS2A. A mathematical model of relaxation of residual compressive stresses created by surface plastic deformation techniques with symmetrical cyclical bending of samples has been proposed. An empirical expression is proposed for assessing the final value of residual stresses as a result of cyclic loading, depending on the stress amplitude of a symmetric cycle. An expression is given for estimating the coefficient of relaxation rate of residual compressive stresses from their initial value, amplitude of alternating stresses and material properties. The constants of these expressions are determined for various construction materials. The theoretical dependences describe well the obtained experimental data. To predict the level of residual stress realization under operational loading, a formula was obtained to calculate their change as a result of the action of a step loading block with different amplitudes and duration of their action at each of the stages.

Numerical Investigation of the Influence of Tool Rake Angle on Residual Stresses in Precision Hard Turning

2016 ◽  
Vol 686 ◽  
pp. 68-73 ◽  
Author(s):  
János Kundrák ◽  
Gergely Szabó ◽  
Angelos P. Markopoulos
Keyword(s):  
Residual Stresses ◽  
Surface Integrity ◽  
Hard Turning ◽  
Dominant Role ◽  
A Priori ◽  
Relevant Literature ◽  
Rake Angle ◽  
Compressive Stresses ◽  
Wide Range

In precision manufacturing processes surface integrity is of the utmost importance for the performance and life-cycle of the final products. An important aspect of surface integrity is associated with residual stresses induced in the workpiece during machining. According to the relevant literature, tool rake angle plays an important role on the features of residual stresses, regarding their magnitude and distribution within the workpiece. In this paper, numerical investigations with the use of the finite elements method are presented that allow the evaluation of the influence of the tool rake angle on residual stresses for the case of hard turning of stainless steel. The investigation is performed in a wide range of positive and negative rake angles. Numerical results verify the dominant role of tool rake angle on the residual stresses. The proposed models can be used for the a priori evaluation of the characteristics of compressive stresses that are considered favorable for the produced components.

Development of Internal Stresses in Alumina-Zirconia Laminates

2012 ◽  
Vol 507 ◽  
pp. 221-226
Author(s):  
Zdeněk Chlup ◽  
Hynek Hadraba ◽  
Daniel Drdlík ◽  
Karel Maca ◽  
Ivo Dlouhý
Keyword(s):  
Electrophoretic Deposition ◽  
Tape Casting ◽  
Slip Casting ◽  
Fem Simulation ◽  
High Strength ◽  
Internal Stresses ◽  
Strong Bond ◽  
Wide Range ◽  
Strength And Stiffness ◽  
Laminated Structures

The laminated ceramics can provide a flaw tolerant behaviour compare to the monolithic ceramics. Two ways how to ensure flaw tolerant behaviour of layered materials are known. The first is based on production of weak interfaces between layers allowing delamination without catastrophic failure. The second way, on the contrary, uses strong bond between layers ensuring high strength and stiffness. The presence of internal stresses developed due to differences in shrinkage of individual layers can effectively change the crack path or even more to stop the crack propagation. Laminated structures with strong bond between layers can be prepared by various methods including tape casting, slip casting and last but not least by electrophoretic deposition. The electrophoretic deposition is probably the most suitable method which is able to create sharp and therefore strong interface in wide range of preciously set layer thicknesses. This contribution demonstrates a way how to determine level of internal stresses based on combined numerical simulation and dilatometric measurements. For this purposes alumina and zirconia monoliths and laminates were prepared. The numerical model of laminated structure using measured data was created for FEM simulation to obtain a stress distribution.

Energy Efficient Servo Controlled Roll Levelling Machines

2016 ◽  
Vol 716 ◽  
pp. 413-419
Author(s):  
Eneko Sáenz de Argandoña ◽  
Elena Silvestre ◽  
Daniel Garcia ◽  
Joseba Mendiguren ◽  
Lander Galdos
Keyword(s):  
Energy Consumption ◽  
Residual Stresses ◽  
Sheet Metal ◽  
Energy Efficient ◽  
High Strength Steels ◽  
High Strength ◽  
Important Process ◽  
Process Improvements ◽  
Wide Range ◽  
Ultra High Strength Steels

The roll levelling and coil straightening facilities are becoming one of the most important process steps when forming Ultra High Strength Steels. The correct levelling and straightening of these materials are the main responsible for the stabilization of the residual stresses through the thickness and post forming springback of sheet metal formed components.Due to the arrangement of the rolls in roll levellers, micro-sliding occurs between the rolls and the sheet and the first rolls are subjected to high torques and high forces since they are responsible for the plastification of the material to a high extent. In order to reduce these drawbacks and optimize the energy consumption avoiding energy loses due to friction, the use of servo technology in levelling processes is studied in this paper.A wide range of materials are levelled using the conventional and the new servo controlled strategy that uses two servo motors and the process improvements are quantified.

scholarly journals FEM study of internal stresses evolution in prestressing strands

2020 ◽  
pp. 21-24
Author(s):  
A. G. Korchunov ◽  
E. M. Medvedeva ◽  
P. V. Ivekeeva ◽  
D. V. Konstantinov
Keyword(s):  
Residual Stresses ◽  
Mechanical Treatment ◽  
High Tech ◽  
Internal Stresses ◽  
Russian Science ◽  
Near Surface ◽  
Thermo Mechanical Treatment ◽  
The Wire ◽  
Prestressing Strands ◽  
The Government

This paper describes the results of modeling when the processes of stranding, reduction, straightening and thermo-mechanical treatment (TMT) of prestressing strands were simulated with the help of finite-element method. The distribution of residual stresses used in the simulation models refers to the stresses created at the preliminary stage of wire drawing. The simulation study looked at the effect of thermo-mechanical treatment on the internal wire stresses: residual stresses resultant from the drawing process and further stranding stresses. All studied methods demonstrated a positive effect not only in terms of eliminating internal stresses, but also from the point of view of their redistribution. Reduction of a strand in a solid tool at the ratios of 1–3 % allows to create tensile stresses at the surface of the wire and retain compressive stresses in its core. Straightening in a 5-roller group helped reach a double relaxation in outer wires. TMT, a process combining different physical effects, enabled to control within a broad range the redistribution of residual stresses in steel that was subjected to prior drawing at high deformation ratios. Such residual stresses occur as a result of stranding stresses that accompany the stranding operation and can affect the geometry of the strand. The study showed that tension as a TMT parameter plays a greater role in the elimination of longitudinal residual stresses. That’s why, at the minimum tension, almost no redistribution of residual stresses occur either in the central or in the near-surface layers irrespective of the TMT temperature regime applied. However, when the tension exceeding 70 kN is applied at the temperatures of 380–400 °C, the central and surface residual stresses balance off in the wire or almost disappear. This research was carried out under the Decree No. 220 dated 9th April 2010 of the Government of the Russian Federation (Contract No. 075-15-2019-869 dated 12th May 2019) and was funded by the Russian Science Foundation (Project No. 20-69-46042 dated 20th May 2020) and by the Russian Ministry of Education and Science with the goal of developing high-tech production (contract nos. 02.G25.31.078, December 1, 2015; and MK204895, July 27, 2015).

scholarly journals New functional insights into the internal architecture of the laminated anchor spicules of Euplectella aspergillum

2015 ◽  
Vol 112 (16) ◽  
pp. 4976-4981 ◽  
Author(s):  
Michael A. Monn ◽  
James C. Weaver ◽  
Tianyang Zhang ◽  
Joanna Aizenberg ◽  
Haneesh Kesari
Keyword(s):  
High Strength ◽  
Internal Stresses ◽  
Organic Layer ◽  
Solid Core ◽  
Skeletal System ◽  
Sea Floor ◽  
Mechanics Model ◽  
Wide Range ◽  
Structural Principles ◽  
Internal Architecture

To adapt to a wide range of physically demanding environmental conditions, biological systems have evolved a diverse variety of robust skeletal architectures. One such example, Euplectella aspergillum, is a sediment-dwelling marine sponge that is anchored into the sea floor by a flexible holdfast apparatus consisting of thousands of anchor spicules (long, hair-like glassy fibers). Each spicule is covered with recurved barbs and has an internal architecture consisting of a solid core of silica surrounded by an assembly of coaxial silica cylinders, each of which is separated by a thin organic layer. The thickness of each silica cylinder progressively decreases from the spicule’s core to its periphery, which we hypothesize is an adaptation for redistributing internal stresses, thus increasing the overall strength of each spicule. To evaluate this hypothesis, we created a spicule structural mechanics model, in which we fixed the radii of the silica cylinders such that the force transmitted from the surface barbs to the remainder of the skeletal system was maximized. Compared with measurements of these parameters in the native sponge spicules, our modeling results correlate remarkably well, highlighting the beneficial nature of this elastically heterogeneous lamellar design strategy. The structural principles obtained from this study thus provide potential design insights for the fabrication of high-strength beams for load-bearing applications through the modification of their internal architecture, rather than their external geometry.

scholarly journals Numerical Investigations of the Crack Resistance of Ion-Strengthened Sheet Glass Under Bending Strains

2021 ◽  
Vol 24 (3) ◽  
pp. 27-34
Author(s):  
Pavlo P. Hontarovskyi ◽  
◽  
Natalia V. Smetankina ◽  
Serhii V. Ugrimov ◽  
Nataliia H. Garmash ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Residual Stresses ◽  
Crack Resistance ◽  
Sheet Glass ◽  
Surface Crack ◽  
Bending Strength ◽  
Surface Defects ◽  
High Strength ◽  
Structural Element ◽  
Compressive Stresses

The safety of reliable operation of aircraft and their durability essentially depend on the strength of the glazing, which is a critical structural element. There are a number of different requirements for glazing. To provide the necessary parameters, high-strength silicate glass is widely used, and special technologies for its strengthening are used. The analysis of the problem showed that the insufficient strength of aircraft glazing elements and the complexity of methods for monitoring the state of glass during production and operation due to the presence of microscopic surface defects, as well as the need for a reliable assessment of residual stresses, require that there be used new approaches and technical solutions for the development of modern technologies for creating structures. Ion exchange is one of the glass strengthening mechanisms, which makes it possible to reduce the negative effect of surface defects by artificially creating residual compressive stresses and reducing the thickness of the damaged layer. Computational studies, under bending strains, of the crack resistance of ion-exchange strengthened sheet glass were carried out using an in-house FEM-based software package developed to study the thermally stressed states of structures. The results obtained showed that the strength of real sheet glass fracture due to tensile stresses in bending is determined by crack-like surface defects. The creation of residual compressive stresses on the glass surface by ion exchange strengthening provides an increase in bending strength. With an increase in residual stresses and the depth of their distribution, the effect of ion-exchange treatment increases. If the depth of the zone of compressive stresses due to ion-exchange strengthening is much less than the depth of the surface crack, then the strength of the glass depends little on the maximum compressive stresses on the surface. The effect of ion-exchange strengthening increases significantly in the case of a decrease in the depth of the surface crack. The expediency of further research and comparison of calculation results with experimental data are shown. The developed technique will make it possible to solve important practical problems in studying the strength of the aircraft multilayer glazing and determining the optimal methods for eliminating defects.

Numerical Study of Residual Thermal Stresses in MMC

2020 ◽  
Vol 22 (4) ◽  
pp. 1099-1110
Author(s):  
Tayeb Nehari
Keyword(s):  
Residual Stresses ◽  
Thermal Stresses ◽  
Numerical Study ◽  
Aluminum Matrix ◽  
Internal Stresses ◽  
Thermal Residual Stresses ◽  
Wide Range ◽  
The Matrix ◽  
Silicon Carbide Particles ◽  
Carbide Particles

AbstractIn this paper, numerical study analysis of residual thermal stresses in aluminum matrix reinforced with silicon carbide particles with double-crack has been carried out. is studied in order to determine the thermo-mechanical behavior under the effect of different temperature gradients during cooling. For a more realistic simulation of the microstructure of these materials subjected to different loadings, a representative volume element may be used. In this paper, three different types of crack width a = 5 μm, 10 μm, 15 μm, has been carried. The thermal residual stresses are calculated by considering a wide range of cracks of different penetrations proximity to particle of 0.1, 0.2 and 0.5 μm. regarding the distribution of the stresses along the plane of the crack and in vicinity of the particle, results show that the penetration of the crack in the matrix causes an asymmetry. The inter-distance between crack and particle plays an important role regarding the generation of residual stresses. The lower the inter-distance, the higher the internal stresses of normal residual stresses of σzz.

The Influence of Bauschinger Effect on the Stability of Residual Stresses in Autofrettaged High Pressure Tubes

2018 ◽  
Author(s):  
Hermann Maderbacher ◽  
Manfred Pölzl
Keyword(s):  
High Pressure ◽  
Yield Strength ◽  
Residual Stresses ◽  
Bauschinger Effect ◽  
High Strength ◽  
Quantitative Character ◽  
Compressive Stresses ◽  
Pressure Tubes ◽  
The Stability ◽  
Fatigue Endurance

In the petrochemical industry, in particular for LDPE (Low-Density-Poly-Ethylene) and EVA-processes (Ethylene-Vinyl-Acetate), high strength quenched and tempered steels are used for seamless tubes subjected to ultra-high pressure. The high safety demands at pressures up to 4000bar require besides high fracture toughness and static strength also high fatigue endurance. The fatigue performance can be significantly impoved by the use of autofrettage. In this case residual compressive stresses are generated with simultaneous material work-hardening by targeted plastic deformation in the area of the inner wall of the tube. The positive effect of autofrettage mainly depends on the level of residual compressive stress. The maximum magnitude of these compressive stresses is always smaller than the yield strength of the material in tensile direction, even if the autofrettage level is increased. The amount by what this stress is smaller than the material yield strength depends on the characteristic of the so-called Bauschinger-effect, or on the kinematic hardening behavior of the material. The target of the present work is to investigate the stability of residual stresses from autofrettage and their influence on the service life of high pressure tubes under cyclic internal pressure loading. For this purpose, in the first part, the quantitative character of the Bauschinger effect for a high strength quenched and tempered steel is determined by means of specimen tests. In the next step, the influence of the Bauschinger-effect on the resulting residual compressive stresses in a tube-like specimen is investigated. Autofrettage tests are performed on these specimens equipped with strain gages. In the second part of the work, the results of fatigue tests of the mentioned tube-like specimen are compared with the calculated fatigue endurance according to Division 3, Section VIII of the ASME Pressure Vessel Code (BPVC). Calculations are performed, which once use the residual stress correction for reverse yielding according to ASME Code and once consider the actual residual stresses from tests and simulation.

Sign in / Sign up

Export Citation Format

Share Document