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.

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.

Deformation twinning in vanadium single crystals tested in compression at 77 K

2018 ◽  
Vol 737 ◽  
pp. 413-421 ◽  
Author(s):  
Roman Gröger ◽  
Zdeněk Chlup ◽  
Tereza Kuběnová
Keyword(s):  
Single Crystals ◽  
Deformation Twinning

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.

Acrylic Plastic Spherical Shell Windows Under Point Impact Loading

1976 ◽  
Vol 98 (2) ◽  
pp. 563-575 ◽  
Author(s):  
J. D. Stachiw ◽  
O. H. Burnside
Keyword(s):  
Hydrostatic Pressure ◽  
Spherical Shell ◽  
Impact Loading ◽  
External Hydrostatic Pressure ◽  
Element Analysis ◽  
Destructive Effect ◽  
Tensile Stresses ◽  
Acrylic Plastic ◽  
Degree Of Confidence ◽  
Ocean Environment

Acrylic plastic spherical shell sector windows with 117-deg included angle and outside radius of 24-in. (61 mm), have been impacted at their center, with a 12,500 lb (5662 kg) weight, in a simulated ocean environment. Velocities of impacts ranged from 0.205 to 10.702 ft (0.06 to 3.26 m) per second. It has been found that fracture of windows is initiated by tensile stresses on the concave surface of the window, directly below the point of impact. Compressive stresses, generated by external hydrostatic pressure, decrease the destructive effect of tensile stresses introduced by point impact loading. For 2.25 and 4.0-in. (57 and 101 mm) thick windows the critical impact velocities were found to fall into the 1.5 to 3 ft (0.45 to 0.91 m) per second range, the exact value being a function of window thickness and external hydrostatic pressure. A finite element analysis was found to agree rather well with the experimental. This analysis can be employed to predict, with a reasonable degree of confidence, the critical impact velocities for acrylic plastic spherical windows in the bows of submersibles.

scholarly journals Deformation Twinning in Cu-Si Alloy Single Crystals

1975 ◽  
Vol 39 (3) ◽  
pp. 261-267 ◽  
Author(s):  
Shozo Yoshioka ◽  
Yutaka Nakayama ◽  
Taichiro Ito ◽  
Hiroshi Mabuchi
Keyword(s):  
Single Crystals ◽  
Deformation Twinning

Resistance of prestressed bridge girders to diagonal tension cracking

2021 ◽  
Author(s):  
Marco A. Roosen ◽  
Max A. N. Hendriks ◽  
Yuguang Yang ◽  
Cor van der Veen ◽  
Dick Schaafsma
Keyword(s):  
Tensile Strength ◽  
Failure Mode ◽  
Bridge Girders ◽  
Shear Reinforcement ◽  
Tensile Stresses ◽  
Compressive Stresses ◽  
Eurocode 2 ◽  
Prestressed Bridge Girders ◽  
Improved Model ◽  
The Web

<p>Diagonal tension cracking is the governing failure mode for bridge girders with a thin web that are highly prestressed and contain little shear reinforcement. When assessing existing bridge girders using the Eurocode 2 [1], it often turns out that it is not possible to demonstrate sufficient resistance to diagonal tension cracking. This paper evaluates the method to determine the maximum principal tensile stresses as used in the Eurocode 2 [1] and investigates how flexural cracks affect the principle tensile stresses in the regions without flexural cracks. This paper also investigates how the tensile strength of the web is affected by the presence of compressive stresses and by the size of the area subjected to high tensile stresses. Based on the results of these investigations, an improved model is proposed to determine the resistance to diagonal tension cracking.</p>

Calculation of Thermal Stresses in Mo-Ti FGM with a Continuous Change of Composition

2005 ◽  
Vol 475-479 ◽  
pp. 1529-1532 ◽  
Author(s):  
Lian Meng Zhang ◽  
Qiang Shen ◽  
Zhong Min Yang
Keyword(s):  
Thermal Stresses ◽  
Bending Strength ◽  
Functionally Graded ◽  
Continuous Change ◽  
Hot Press ◽  
Medial Region ◽  
Tensile Stresses ◽  
Compressive Stresses ◽  
Ti Alloys ◽  
Graded Material

In the present paper, a kind of Mo-Ti system functionally graded material with a continuous change of composition was formed via particle settling method at first, and then it was desified by hot-press under 1473K-30MPa-1h. Finally, by using an axisymmetric finite element method, the fabricated thermal stresses in a disk-shaped Mo-Ti FGM were calculated. The results showed that the thermal stresses changed continuously with the smooth variation of graded composition. The residual tensile stresses in the Mo-Ti FGM with a continuously changed composition were located in the medial region of graded layer and the radial compressive stresses distributed in the Mo- and Ti-rich sides. The calculated maximum residual tensile stresses in the Mo-Ti FGM were much lower than the bending strength of Mo-Ti alloys, which demonstrated that during fabrication no damages occurred in the Mo-Ti FGM with continuously graded composition.

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