scholarly journals Transitory Ultrasonic Absorption in “Domain Engineered” Structures of 10 M Ni-Mn-Ga Martensite

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1505
Author(s):  
Sergey Kustov ◽  
Andrey Saren ◽  
Bruno D’Agosto ◽  
Konstantin Sapozhnikov ◽  
Vladimir Nikolaev ◽  
...  

In this work we create in 10 M Ni-Mn-Ga martensitic samples special martensitic variant structures consisting of only three twins separated by two a/c twin boundaries: Type I and Type II, with relatively low and very high mobility, respectively. The “domain engineered” structure thus created allows us to investigate the dynamics of a single highly mobile a/c twin boundary (TB). We show that temperature variations between 290 and 173 K in our samples induce an intense transitory internal friction at ultrasonic frequencies ca. 100 kHz, peaking around 215 K. A comparison is made of the data for the “domain engineered” sample with the behaviour of reference samples without a/c TB. Reference samples have two different orientations of a/b twins providing zero and maximum shear stresses in a/b twinning planes. We argue, first, that the transitory internal friction, registered at rather high ultrasonic frequencies, has magnetic origin. It is related with the rearrangement of magnetic domain structure due to the motion of a/c twin boundary induced by thermal stresses. This internal friction term can be coined “magnetic transitory internal friction”. Magnetic transitory internal friction is a new category, linking the classes of transitory and magnetomechanical internal friction. Second, the structure of a/b twins is strongly non-equilibrium over a broad temperature range. As a consequence, the Young’s modulus values of the samples with maximum shear stress in a/b twinning planes can take any value between ca. 15 and 35 GPa, depending on the prehistory of the sample.

1969 ◽  
Vol 91 (3) ◽  
pp. 891-896 ◽  
Author(s):  
G. E. Novak ◽  
B. J. Eck

A numerical solution is presented for both the transient temperature and three-dimensional stress distribution in a railcar wheel resulting from a simulated emergency brake application. A computer program has been written for generating thermoelastic solutions applicable to wheels of arbitrary contour with temperature variations in both axial and radial directions. The results include the effect of shear stresses caused by the axial-radial temperature gradients and the high degree of boundary irregularity associated with this type of problem. The program has been validated by computing thermoelastic solutions for thin disks and long cylinders; the computed values being in good agreement with the closed form solutions. Currently, the computer program is being extended to general stress solutions corresponding to the transient temperature distributions obtained by simulated drag brake applications. When this work is completed, it will be possible to synthesize the thermal history of a railcar wheel and investigate the effects of wheel geometry in relation to thermal fatigue.


2013 ◽  
Vol 184 (4-5) ◽  
pp. 299-306 ◽  
Author(s):  
Richard J. Lisle

AbstractThe assumption is widely made that slip on faults occurs in the direction of maximum resolved shear stress, an assumption known as the Wallace-Bott hypothesis. This assumption is used to theoretically predict slip directions from known in situ stresses, and also as the basis of palaeostress inversion from fault-slip data. This paper examines different situations in relation to the appropriateness of this assumption. Firstly, it is shown that the magnitude of the shear stress resolved within a plane is a function with a poorly defined maximum direction, so that shear stress values greater than 90% of the maximum occur within a wide angular range (± 26°) degrees. The situation of simultaneous movement on pairs of faults requires slip on each fault to be parallel to their mutual line of intersection. However, the resolved shear stresses arising from a homogeneous state of stress do not accord with such a slip arrangement except in the case of pairs of perpendicular faults. Where fault surfaces are non-planar, the directions of resolved shear stress in general give, according to the Wallace-Bott hypothesis, a set of slip directions of rigid fault blocks, which is generally kinematically incompatible. Finally, a simple model of a corrugated fault suggests that any anisotropy of the shear strength of the fault such as that arising from fault surface topography, can lead to a significant angular difference between the directions of maximum shear stress and the slip direction.These findings have relevance to the design of procedures used to estimate palaeostresses and the amount of data required for this type of analysis.


2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Jianxia Wen ◽  
Dan Wang ◽  
Jian Wang ◽  
Ruilin Wang ◽  
Shizhang Wei ◽  
...  

Astragali Radix (AR), the dried root of Astragali Radix membranaceus (Fisch.) Bge. or Astragali Radix membranaceus (Fisch.) Bge. var. mongholicus (Bge) Hsiao, is a commonly used traditional Chinese medicine for the treatment of liver diseases. This study aimed to comprehensively evaluate the pharmacological action and explore the potential mechanism of AR on liver fibrosis. Rats were administered with carbon tetrachloride for eight weeks, followed by oral treatment with AR for six weeks. The efficacy was confirmed by measuring liver function and liver fibrosis levels. The underlying mechanisms were explored by detecting the expression of related proteins. AR significantly decreased the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), collagen IV (COL-IV), hyaluronic acid (HA), laminin (LN), and precollagen type III (PCIII). In addition, AR inhibited the deposition of collagen and the activation of hepatic stellate cells. Those data strongly demonstrated that AR alleviated liver fibrosis by CCl4. In order to illustrate the potential inflammatory, the mRNA levels of IL-6, TNF-α, and IL-1β were detected. Subsequently, immunohistochemistry analysis was performed to further verify the expression of type I collagen. Finally, the expression of key proteins in the inflammatory signaling pathway was detected. AR significantly reduced the expression of high-mobility group box 1 (HMGB1), TLR4, Myd88, RAGE, and NF-κ B p65 genes and proteins. In addition, western blotting showed AR decreased the protein expression of RAGE, p-MEK1/2, p-ERK1/2, and p-c-Jun. Taken together, our data reveal that AR significantly inhibits liver fibrosis by intervening in the HMGB1-mediated inflammatory signaling pathway and secretion signaling pathway. This study will provide valuable references for the in-depth research and development of Astragali Radix against liver fibrosis.


1986 ◽  
Vol 35 (10) ◽  
pp. 1378
Author(s):  
Zhen Wen-guang ◽  
Zhang Jin-xiu ◽  
Lin Hao-qing ◽  
He Zhen-hui ◽  
Yao Yi-fa

2018 ◽  
Vol 147 ◽  
pp. 01005
Author(s):  
Jonie Tanijaya

This study is carried out to evaluate the potential of three hybrid T-beams with web openings theoretical shear stresses distribution. The shear stresses at the opening edges were plotted at the working stage, yielding stage and collapse stage for these three tested beams. The available experimental results from the previous research was compared to the finite element results as well as the developed analytical. The shear stress distribution at the middle of the top and bottom chords of the opening in pure bending region are zero. At the upper and lower corners of the opening occurs the maximum shear stresses. The maximum shear stress occurs at the right lower corner chord at the high moment edge and at the left upper corner chord at the low moment edge in beams with openings at high shear and high flexural – shear region. Furthermore, an extensive parametric study is performed on these beams to find the distributing ratio of the shear force between the opening chords. The shear force at an opening in hybrid R/C T-beam is carried by the top and bottom chords of the opening according to the area – moment of inertia root ratio with the correction factor 0.70.


1999 ◽  
Vol 122 (1) ◽  
pp. 42-48 ◽  
Author(s):  
Xiao Lin

Macroscopic response and microscopic dislocation structures of Zr-4 subjected to biaxial fatigue under different phase angles of 30°, 60°, 90° and different equivalent strain ranges of 0.8%, 0.6%, 0.4% were studied. The testing results show that the delay angle between the stress deviators and strain increment tensors is strongly dependent on phase angle and the equivalent strain range. When phase angle equals 60°, the delay angle has the minimum variation range for all specimens. The mean value of the delay angle decreases with increasing phase angle or the equivalent strain range. The variation range and average value of the Mises equivalent stress have the maximum in S3 with the phase angle of 90°. They decrease as the equivalent strain range decreases. Zr-4 displays a pronounced initial hardening followed by a continuous softening for all specimens during out-of-phase cycling. The stabilized saturation stresses of Zr-4 under out-of-phase cycling are much higher than that under uniaxial cycling. It indicates that Zr-4 displays an obvious additional hardening. As the phase angle increases, the typical dislocation structure changes from dislocation cells to tangles. The dislocation-dislocation interactions increase resulting in an additional hardening. In essence, the degree of additional hardening depends, among other factors, on the maximum shear stress ratio of resolved shear stresses and critical resolved shear stresses (RSS/CRSS). [S0094-4289(00)00601-0]


1983 ◽  
Vol 56 (1) ◽  
pp. 252-269 ◽  
Author(s):  
R. A. Ridha ◽  
R. N. Crano

Abstract The ASTM D 2229-80 test specimen with a circular hole and a pad restriction was analyzed by 3D finite elements. Maximum shear stresses within the specimen are at the cord-rubber interface. Thus, failure is expected to initiate in the vicinity of the cord-rubber interface. This characteristic is similar to that seen in the MICA and TCAT tests; it represents an improvement over other pull-through tests including earlier ASTM tests. The computed tensile stresses normal to the cord indicate that friction forces will not be significant in this test (as they are in the TCAT test) and that debonding will propagate rapidly. In this regard, the D 2229-80 test is similar to the MICA test. Results of photoelastic analysis of the ASTM D 2229-80, MICA, and TCAT tests are in good agreement with the computed results. Maximum shear stress at the cord-rubber interface in the ASTM D 2229-80 test varies with the modulus of elasticity of the rubber. This variation becomes more pronounced with increasing rubber deformations (e.g., at higher loads and with softer rubber compounds). Thus, the cord pullout force will be dependent on the rubber modulus. From the above results we conclude the following: 1. The ASTM D 2229-80 test overcomes one of the serious drawbacks of earlier pull-through tests; failure is expected to initiate in the vicinity of the cord-rubber interface rather than elsewhere in the rubber. The new test's main deficiency is the dependence of the cord pullout force on the rubber modulus; in this regard, the MICA test offers a considerable advantage. 2. The ASTM D2229-80 test may be used in evaluating the adhesion of various steel cords embedded in a control rubber compound. 3. When changes are anticipated in the properties of the rubber compound, the MICA test offers a considerable advantage because the cord pullout force in the MICA test is independent of the rubber modulus.


2006 ◽  
Vol 128 (3) ◽  
pp. 254-259 ◽  
Author(s):  
B. Coluzzi ◽  
A. Biscarini ◽  
G. Mazzolai ◽  
F. M. Mazzolai ◽  
A. Tuissi

The internal friction Q−1 and the Young’s modulus E of NiTi based alloys have been measured as a function of temperature after various thermomechanical and hydrogen-doping treatments given to the materials. Hydrogen is found to play a major role introducing tall damping peaks associated with Snoek-type and H-twin boundary relaxations. Levels of Q−1 as high as 0.08 have been detected, which are among the highest to date measured in metal alloy systems. For appropriate alloy compositions, these peaks occur at around room temperature (for acoustical frequencies), thus providing a good opportunity to reduce machinery vibrations and noise pollution. In the paper, the conditions are highlighted under which maximum efficiency can be reached in the conversion of mechanical energy into heat.


2003 ◽  
Vol 125 (3) ◽  
pp. 504-511 ◽  
Author(s):  
Ching-Kong Chao ◽  
Shih-Yu Hung ◽  
Cheng-Ching Yu

The concept of rapid thermal processing has many potential applications in microelectronics manufacturing, but the details of chamber design remains an active area of research. In this work the influence of lamps radius on the thermal stresses in a wafer during the cooling process is studied in detail. Since the equations governing the present thermal-elastic system are coupled in nature, the solution for the temperature and stresses must proceed simultaneously by using a fully implicit finite difference method. After the thermal stresses are obtained, the optimum lamps radii for various heights of the chamber under the constant power ramp-down control scheme are determined based on the maximum shear stress failure criterion. The shortest cooling time that can significantly reduce the thermal budget and dopant redistribution is also predicted by applying the maximum stress control scheme. The result obtained is useful in the design of a reliable rapid thermal processor based on a more practical consideration, thermal stress.


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