MAGNETOELASTIC ELECTROMAGNETIC ACOUSTIC TRANSFORMATION. Part 5

2019 ◽  
pp. 14-22
Author(s):  
V. A. Komarov
Keyword(s):  
Analytical Model ◽  
Functional Relationship ◽  
Spontaneous Magnetization ◽  
Internal Stresses ◽  
Magnetization Process ◽  
Saturation Magnetostriction ◽  
Tensile Stresses ◽  
Compressive Stresses

The analytical model of the applied and internal stresses influence on the efficiency of EMAT in the region of spontaneous magnetization vectors rotation processes (a saturation magnetostriction ls < 0) in the case of strong polarizing field is considered.It has been shown analytically and confirmed experimentally that in the presence of applied s0 or internal si stresses the region of maximum EMAT efficiency in the polarizing field changes. If the product lss0 or lssi is greater than zero then this region shifts to the weaker fields. If the product lss0 or lssi is less than zero then the maximum of EMAT efficiency shifts to the stronger fields region (magnetization process is difficult) compared to the stresses absence in the sample. The EMAT efficiency for materials with ls < 0 increases with the tensile stresses increasing and decreas with the compressive stresses increasing. It has been shown analytically and confirmed experimentally that the presence of internal stresses in the material changes the efficiency of EMAT inversely related to the magnitude of these stresses. The functional relationship between EMAT efficiency and internal stresses is demonstrated.

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.

Correlation of Residual Stresses in the Fatigue Strength of Axles

1942 ◽  
Vol 9 (2) ◽  
pp. A85-A90
Author(s):  
O. J. Horger ◽  
H. R. Neifert
Keyword(s):  
Heat Treatment ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
High Surface ◽  
Full Size ◽  
Tensile Stresses ◽  
Compressive Stresses ◽  
Actual Service

Abstract The object of this paper is to present a correlation between residual stresses, obtained by heat-treatment, with fatigue values, determined from an investigation of full-size railroad axles. The axles tested were of both solid and tubular design and represent members which could be used under a car in actual service. It was found from these tests that high axle fatigue strength is associated with high surface residual compressive stresses, and lowest axle strength values with surface residual tensile stresses.

scholarly journals The Effect of the Metal Phase on the Compressive and Tensile Stresses Reduction in the Superhard Nitride Coatings

Coatings ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 798
Author(s):  
Alexey O. Volkhonsky ◽  
Igor V. Blinkov ◽  
Dmitry S. Belov
Keyword(s):  
Crack Resistance ◽  
High Hardness ◽  
Scratch Test ◽  
Vacuum Arc ◽  
Nitride Phase ◽  
Tensile Stresses ◽  
Compressive Stresses ◽  
Cutting Inserts ◽  
Evaporation Apparatus ◽  
Arc Evaporation

The influence of the compressive and tensile stresses forming in the nanostructured Ti–Al–N coatings during deposition on their physical-mechanical properties was studied. The modifying influence of metal components (Ni and Cu) introduction into Ti–Al–N coatings, which do not interact with nitrogen and have limited solubility with the nitride phase, was also under research. Coatings were deposited on WC–(6 wt.%)Co carbide cutting inserts with an arc-PVD method using a cathodic vacuum arc evaporation apparatus. The introduction of Ni and Cu to the composition leads to the reduction of nitride phases grain size in both investigated coatings from 120 to 10–12 nm for Ti–Al–Cu–N and to 15–18 nm for Ti–Al–Ni–N. Thus, the hardness increases from 29 to 43 and 51 GPa for the mentioned above coatings, respectively. Meanwhile, Ti–Al–Cu–N and Ti–Al–Ni–N coatings are characterized by tensile stresses about 0.12–0.32 MPa against the much higher value of compressive stresses in Ti–Al–N coatings (4.29–5.31 GPa). The modification of Ti–Al–N coatings also leads to the changing of their destruction mechanism during the scratch-test. The critical loads characterizing the emergence of the first cracks in the coatings and complete abrasion of the coating (Lc1 and Lc3) were determined. They had the value of 20; 22 N (Lc1) and 64; 57 N (Lc3) for Ti–Al–Ni–N; Ti–Al–Cu–N coatings, respectively. The Lc1 parameter for Ti–Al–N coatings was much lower and was equal to 11 N. Along with those, Ti–Al–N coatings destructed according to the adhesion mechanism when the critical load was 35 N. In addition, the decreasing level of compressive stresses in Ti–Al–Cu–N and Ti–Al–Ni–N coatings as compared to that in the Ti–Al–N coating, their crack resistance during multi-cycle shock-dynamic impact test was significantly higher. The results can indicate that high hardness and crack resistance of the coatings is to a greater extent determined by coatings nanostructuring, not the stresses value. In addition, it confirms the possibility to obtain coatings with low stresses value while maintaining their superhardness.

The Control Of Intrinsic Stresses In Cvd Diamond Films With Multistep Processing

1995 ◽  
Vol 416 ◽  
Author(s):  
S. Nijhawan ◽  
S. M. Jankovsky ◽  
B. W. Sheldon
Keyword(s):  
Thermal Stresses ◽  
Microwave Plasma ◽  
Diamond Films ◽  
Annealing Treatment ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Internal Stresses ◽  
Tensile Stresses ◽  
Si Substrates

ABSTRACTThe role of intrinsic stresses in diamond films is examined. The films were deposited on (100) Si substrates by microwave plasma-enhanced chemical vapor deposition. The total internal stresses (thermal and intrinsic) were measured at room temperature with the bending plate method. The thermal stresses are compressive and arise due to the mismatch in thermal expansion coefficient of film and substrate. The intinsic stresses were tensile and evolved during the deposition process. These stresses increased with increasing deposition time. A 12 hour intermediate annealing treatment was found to reduce the tensile stresses considerably. The annealing treatment is most effective when the diamond crystallites are undergoing impingement and coalescence. This is consistent with the theory that the maximum tensile stresses are associated with grain boundary energetics.

Pressure effect on spontaneous magnetization and first-order magnetization process in the Er2Fe17 single crystal

1999 ◽  
Vol 196-197 ◽  
pp. 701-702 ◽  
Author(s):  
J. Kamarád ◽  
O. Mikulina ◽  
Z. Arnold ◽  
B. Garcia-Landa ◽  
M.R. Ibarra ◽  
...  
Keyword(s):  
Single Crystal ◽  
Pressure Effect ◽  
Spontaneous Magnetization ◽  
Magnetization Process ◽  
First Order

scholarly journals Local, transient tensile stress on the nuclear membrane causes membrane rupture

2019 ◽  
Vol 30 (7) ◽  
pp. 899-906 ◽  
Author(s):  
Qiao Zhang ◽  
Andrew C. Tamashunas ◽  
Ashutosh Agrawal ◽  
Mehdi Torbati ◽  
Aditya Katiyar ◽  
...  
Keyword(s):  
Tensile Stress ◽  
Nuclear Membrane ◽  
Mammary Epithelial Cells ◽  
Mammary Epithelial ◽  
Tensile Stresses ◽  
Membrane Rupture ◽  
Nuclear Membranes ◽  
Compressive Stresses ◽  
Diffusive Fluxes ◽  
Nuclear Deformations

Cancer cell migration through narrow constrictions generates compressive stresses on the nucleus that deform it and cause rupture of nuclear membranes. Nuclear membrane rupture allows uncontrolled exchange between nuclear and cytoplasmic contents. Local tensile stresses can also cause nuclear deformations, but whether such deformations are accompanied by nuclear membrane rupture is unknown. Here we used a direct force probe to locally deform the nucleus by applying a transient tensile stress to the nuclear membrane. We found that a transient (∼0.2 s) deformation (∼1% projected area strain) in normal mammary epithelial cells (MCF-10A cells) was sufficient to cause rupture of the nuclear membrane. Nuclear membrane rupture scaled with the magnitude of nuclear deformation and the magnitude of applied tensile stress. Comparison of diffusive fluxes of nuclear probes between wild-type and lamin-depleted MCF-10A cells revealed that lamin A/C, but not lamin B2, protects the nuclear membranes against rupture from tensile stress. Our results suggest that transient nuclear deformations typically caused by local tensile stresses are sufficient to cause nuclear membrane rupture.

DEFORMATION TWINNING IN Bi-Sb CRYSTALS UNDER DYNAMIC INDENTATION

2001 ◽  
Vol 08 (03n04) ◽  
pp. 241-243 ◽  
Author(s):  
R. C. SHAH
Keyword(s):  
Single Crystals ◽  
Impact Loading ◽  
Deformation Twinning ◽  
Spherical Indenter ◽  
Dynamic Indentation ◽  
Tensile Stresses ◽  
Compressive Stresses ◽  
Mechanical Twins

Bi–Sb single crystals (with Sb concentration varied up to 30 at. %) have been subjected to impact loading in the form of dynamic indentation on their (111) cleavage planes. The resulting mechanical twins are the theme of this report. The tensile and compressive stresses developed by the spherical indenter employed have been differentiated with respect to their role in producing the twins. While the twins produced in the crystals with Sb ≤15 at. % are interpreted as being due to tensile stresses, those in the crystals with Sb>15 at. % are found to be due to compressive stresses.

Novel Nanostructural Biomaterial Composites

2002 ◽  
Author(s):  
R. J. Narayan
Keyword(s):  
Heart Valves ◽  
Antimicrobial Properties ◽  
Internal Stresses ◽  
Dlc Coatings ◽  
Compressive Stresses ◽  
Diamondlike Carbon ◽  
Nanotube Composites ◽  
Novel Processing ◽  
Hardness Values ◽  
Poor Adhesion

Hydrogen-free diamondlike carbon (DLC), with hardness values close to that of diamond, possess many desirable biocompatible properties for a variety of biomedical applications. The DLC coatings can be applied to joints prostheses, heart valves, and other medical devices. Unfortunately, hydrogen-free DLC coatings have a large compressive stresses which result in poor adhesion and wear characteristics. In this paper, we present results on silver doping of DLC to alleviate internal stresses as well as create DLC-Ag nanocomposites where Ag is in the form of nanoparticles. The Ag nanoparticles are expected to impart antimicrobial properties by providing sources of electrons. In the second part of the paper, we have created DLC and nanotube composites where nanotubes grow normal to the surface. This novel architecture not only alleviates internal stresses, but DLC + Nanotube composites have enhanced hardness and unique antimicrobial properties. Finally, we discuss novel multilayer DLC and hydroxyapatite (HA) composite where HA and DLC films are deposited sequentially at room temperature. The HA films with composites close to that of bone is considered very desirable for biocompatibility and integration with base structures. We discuss novel processing, characterization, hardness and bioeompatible properties of all these composites in detail.

scholarly journals Impact of Stress Annealing on the Magnetization Process of Amorphous and Nanocrystalline Co-Based Microwires

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2644 ◽  
Author(s):  
Ahmed Talaat ◽  
Valentina Zhukova ◽  
Mihail Ipatov ◽  
Juan María Blanco ◽  
Julián Gonzalez ◽  
...  
Keyword(s):  
Domain Wall ◽  
Stress Dependence ◽  
Magnetization Process ◽  
Magnetoelastic Anisotropy ◽  
Tensile Stresses ◽  
Amorphous Microwires

The domain wall (DW) dynamics of amorphous and nanocrystalline Co-based glass-coated microwires are explored under the influence of stress annealing. Different annealing profiles have enabled remarkable changes in coercivity and magnetostriction values of Co-based amorphous microwires with initially negative magnitude, allowing induced magnetic bistability in stress-annealed samples and, consequently, high DW velocity has been observed. Similarly, Co-based nanocrystalline microwires with positive magnetostriction and spontaneous bistability have featured high DW velocity. Different values of tensile stresses applied during annealing have resulted in a redistribution of magnetoelastic anisotropy showing a decreasing trend in both DW velocities and coercivity of nanocrystalline samples. Observed results are discussed in terms of the stress dependence on magnetostriction and microstructural relaxation.

Internal Stresses in Plasma Coatings with an Amorphous Structure

1998 ◽  
Author(s):  
Y. Borisov ◽  
V. Korzhyk
Keyword(s):  
Stress State ◽  
Boron Content ◽  
Amorphous Structure ◽  
Internal Stresses ◽  
Compressive Stresses ◽  
Stress Formation ◽  
Coating Layers ◽  
Plasma Sprayed ◽  
Amorphous Coatings ◽  
Material Temperature

Abstract The stress state of plasma sprayed amorphous coatings of the Fe-B based alloys with the boron content of 15-35 %, as well as of the above type alloys but with additions of Ni, Cr, Mo, was studied. Internal stresses depend on the type of a plasma gas, thickness and composition of the coatings, material, temperature and conditions of additional cooling of the substrate. Additional cooling of the substrate was found to be the most efficient method of decreasing the internal stress. Formation of compressive stresses in the coating layers adjoining the substrate is shown to lead to 25-30 % increase in its fatigue strength under alternating loads.

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