Pulse Propagation in Straight Circular Elastic Tubes

1972 ◽  
Vol 39 (4) ◽  
pp. 1011-1018 ◽  
Author(s):  
W. Goldsmith ◽  
P. Y. Lee ◽  
J. L. Sackman
Keyword(s):  
Experimental Investigation ◽  
Pulse Duration ◽  
Longitudinal Strain ◽  
Pulse Propagation ◽  
Transverse Strain ◽  
Longitudinal Impact ◽  
Elastic Tubes ◽  
Air Gun ◽  
Steel Balls ◽  
Longitudinal Strains

An experimental investigation of elastic waves produced by the longitudinal impact of strikers with straight 2024 aluminum tubes of 1-in. dia and wall thicknesses of 0.035 in. (thin-walled), 0.095 in. (medium thick-walled), and 0.5 in. (solid bar) was performed by means of the Hopkinson bar technique. For most of the tests the strikers consisted of 1/2-in-dia steel balls; however, 1/4-in-dia, 3/16-in-dia and 1/8-in-dia steel balls were also used to permit variation in pulse duration. Both central and eccentric impact were achieved by firing the striker from an air gun at a predetermined pressure against the carefully positioned target; the initial velocity of the striker was measured whenever necessary. Longitudinal strain records of the resulting pulse from positions both on the inside and outside surfaces of the hollow specimens and on the outside of the solid bar were obtained by using strain gages of either foil or semiconductor type; some transverse strain histories were also measured concurrently. The transient longitudinal strains were predicted theoretically by solving the one-dimensional Rayleigh-Love equation of wave propagation in a semi-infinite tube with the aid of a computer program. The input to the program consisted of the measured strain record at the first gage station. Reasonable agreement between the data and the results of these calculations was obtained. An experimental investigation of the effect of shortening the pulse duration, the relation between the transverse and longitudinal strain at the same position, and the nature of the antisymmetrical component in the eccentric shots was also undertaken.

Plastic Waves of Combined Stresses Due to Longitudinal Impact of a Pretorqued Tube—Part 1: Experimental Results

1970 ◽  
Vol 37 (4) ◽  
pp. 1107-1112 ◽  
Author(s):  
J. Lipkin ◽  
R. J. Clifton
Keyword(s):  
Slow Wave ◽  
Longitudinal Strain ◽  
Fast Wave ◽  
Longitudinal Impact ◽  
Strain Response ◽  
Torsional Strain ◽  
Time Profiles ◽  
Combined Stresses ◽  
Fast Waves ◽  
Longitudinal Strains

Experiments are reported in which annealed aluminum tubes are subjected to a static plastic torque followed by a longitudinal compressive impact. Measurements are made of both longitudinal and shear strain-time profiles at stations along the specimen. Qualitatively, the strain response at the gages corresponds to the arrival of a fast wave for which torsional strain decreases while longitudinal strain increases followed by a slow wave for which both torsional and longitudinal strains increase. Between the slow and fast waves and following the slow wave, a strain rate of the order of 10 sec−1 is maintained.

ESR STUDY OF THE EFFECT OF UNIAXIAL STRESS ON THE BAND STRUCTURE OF CdS:I

1967 ◽  
Vol 45 (1) ◽  
pp. 127-135 ◽  
Author(s):  
B. J. Slagsvold ◽  
C. F. Schwerdtfeger
Keyword(s):  
Longitudinal Strain ◽  
Optical Band Gap ◽  
Energy Gap ◽  
Uniaxial Stress ◽  
Uniaxial Pressure ◽  
Transverse Strain ◽  
Deformation Potential ◽  
Average Change ◽  
Valence Bands ◽  
G Value

The shift with uniaxial pressure in the g value of the ESR signal obtained from conductive iodine-doped CdS has been measured at ≈ 1.7 °K. For pressures parallel to the c axis, an average change in the g tensor of ≈ 9.4 × 10−7 cm2/kg was found, while for perpendicular pressures [Formula: see text] shifted an average of ≈ 4.4 × 10−7 cm2/kg. These shifts have been ascribed to a change in the energy gap separating the conduction-band minimum from the valence bands. They, as well as the change in the optical band gap with hydrostatic pressure as measured by Langer (1960), could be fairly well described by the approximate values 6.3 eV/unit longitudinal strain and 1.8 eV/unit transverse strain of the deformation potential constants for the gap.

Impact of Thoracic Endovascular Aortic Repair on Pulsatile Circumferential and Longitudinal Strain in Patients With Aneurysm

2017 ◽  
Vol 24 (2) ◽  
pp. 281-289 ◽  
Author(s):  
Foeke J. H. Nauta ◽  
Guido H. W. van Bogerijen ◽  
Chiara Trentin ◽  
Michele Conti ◽  
Ferdinando Auricchio ◽  
...  
Keyword(s):  
Longitudinal Strain ◽  
Celiac Trunk ◽  
Ascending Aorta ◽  
Thoracic Endovascular Aortic Repair ◽  
Endovascular Aortic Repair ◽  
Sinotubular Junction ◽  
Aortic Repair ◽  
Brachiocephalic Trunk ◽  
The Impact ◽  
Longitudinal Strains

Purpose: To quantify both pulsatile longitudinal and circumferential aortic strains before and after thoracic endovascular aortic repair (TEVAR), potentially clarifying TEVAR-related complications. Methods: This retrospective study assessed the impact of TEVAR on pulsatile aortic strains through custom developed software and cardiac-gated computed tomography imaging of 8 thoracic aneurysm patients (mean age 71.0±8.2 years; 6 men) performed before TEVAR and during follow-up (median 0.1 months, interquartile range 0.1–5.8). Lengths of the ascending aorta, the aortic arch, and the descending aorta were measured. Diameters and areas were computed at the sinotubular junction, brachiocephalic trunk, left subclavian artery, and the celiac trunk. Pulsatile longitudinal and circumferential strains were quantified as systolic increments of length and circumference divided by the corresponding diastolic values. Results: Average pulsatile longitudinal strain ranged from 1.4% to 7.1%, was highest in the arch (p<0.001), and increased after TEVAR by 77% in the arch (7.1%±2.5% vs 12.5%±5.1%, p=0.04) and by 69% in the ascending aorta (5.6±2.3% vs 9.4±4.4%, p=0.06). Average pulsatile circumferential strain ranged from 3.6% to 5.0% before TEVAR and did not differ significantly throughout the thoracic aorta; there was a nonsignificant increase after TEVAR at the unstented sinotubular junction (5.0%±1.4% vs 6.3%±1.0%, p=0.18), with a significant increase at the celiac trunk (3.6%±1.8% vs 6.2%±1.8%, p=0.02). Pulsatile circumferential strains within stented segments were deemed unreliable due to image artifacts. Conclusion: TEVAR was associated with an increase of pulsatile longitudinal strains (in the arch) and circumferential strains (at the celiac trunk) in unstented aortic segments. These observations suggest increased pulsatile wall stress after TEVAR in segments adjacent to the device, which may contribute to the understanding of stent-graft–related complications such as retrograde dissection, aneurysm formation, and rupture.

scholarly journals An experimental investigation of the impact of thoracic endovascular aortic repair on longitudinal strain

2016 ◽  
Vol 50 (5) ◽  
pp. 955-961 ◽  
Author(s):  
Foeke J.H. Nauta ◽  
Michele Conti ◽  
Stefania Marconi ◽  
Arnoud V. Kamman ◽  
Gianluca Alaimo ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Longitudinal Strain ◽  
Thoracic Endovascular Aortic Repair ◽  
Endovascular Aortic Repair ◽  
Aortic Repair ◽  
The Impact

scholarly journals Left and right ventricular longitudinal strains are associated with poor outcome in COVID-19: a systematic review and meta-analysis

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Arief Wibowo ◽  
Raymond Pranata ◽  
Astri Astuti ◽  
Badai Bhatara Tiksnadi ◽  
Erwan Martanto ◽  
...  
Keyword(s):  
Systematic Review ◽  
Longitudinal Strain ◽  
Meta Analysis ◽  
Global Longitudinal Strain ◽  
Left Ventricular ◽  
Poor Outcome ◽  
Literature Searches ◽  
Increased Risk ◽  
Left And Right ◽  
Longitudinal Strains

Abstract Background This systematic review and meta-analysis aimed to assess whether ventricular longitudinal strain can be used as a prognostication tool in patients with coronavirus disease 2019 (COVID-19). Methods Systematic literature searches of PubMed, Embase, and EuropePMC databases were performed on 16 November 2020. Left ventricular global longitudinal strain (LV-GLS) refers to LV contraction measurement using the speckle tracking-based method refers to the mean of strain values of the RV free wall (three segments) measured using echocardiography. The main outcome was poor outcome, defined as a composite of mortality and severe COVID-19. Results Seven studies comprising of 612 patients were included in meta-analysis. Six studies have mortality as their outcome, and 1 study has severity as their outcome. Patients with poor outcome have lower LV-GLS (SMD 1.15 (0.57, 1.72), p < 0.001; I2 70.4%). Each 1% decrease in LV-GLS was associated with 1.4x increased risk of poor outcome (OR 1.37 (1.12, 1.67), p = 0.002; I2 48.8%). Patients with poor outcome have lower RV-LS (SMD 1.18 (0.91, 1.45), p < 0.001; I2 0%). Each 1% decrease in RV-LS was associated with 1.3x increased risk of poor outcome (OR 1.25 (1.15, 1.35), p < 0.001; I2 11.8%). Subgroup analysis showed that for every 1% decrease in LV-GLS and RV-LS is increased mortality with OR of 1.30 (1.12, 1.50) and OR of 1.24 (1.14, 1.35), respectively. Conclusion This study shows that lower LV-GLS and RV-LS measurements were associated with poor outcome in patients with COVID-19. Trial registration PROSPERO CRD42020221144

scholarly journals An experimental investigation to model wheezing in lungs

2021 ◽  
Vol 8 (2) ◽  
Author(s):  
A. L. Gregory ◽  
A. Agarwal ◽  
J. Lasenby
Keyword(s):  
Experimental Investigation ◽  
Lung Diseases ◽  
Necessary Conditions ◽  
Quantitative Model ◽  
Sectional Area ◽  
Predictive Tool ◽  
Cross Sectional ◽  
Physical Mechanisms ◽  
Elastic Tubes ◽  
Deformed State

A quarter of the world's population experience wheezing. These sounds have been used for diagnosis since the time of the Ebers Papyrus ( ca 1500 BC). We know that wheezing is a result of the oscillations of the airways that make up the lung. However, the physical mechanisms for the onset of wheezing remain poorly understood, and we do not have a quantitative model to predict when wheezing occurs. We address these issues in this paper. We model the airways of the lungs by a modified Starling resistor in which airflow is driven through thin, stretched elastic tubes. By completing systematic experiments, we find a generalized ‘tube law’ that describes how the cross-sectional area of the tubes change in response to the transmural pressure difference across them. We find the necessary conditions for the onset of oscillations that represent wheezing and propose a flutter-like instability model for it about a heavily deformed state of the tube. Our findings allow for a predictive tool for wheezing in lungs, which could lead to better diagnosis and treatment of lung diseases.

The effects of preloading on tensile properties of braided polyarylate fiber ropes

2021 ◽  
pp. 004051752110505
Author(s):  
Xu Ding ◽  
Ying Sun ◽  
Chunhui Dong ◽  
Mengwei Guo ◽  
Li Chen
Keyword(s):  
Tensile Properties ◽  
Image Correlation ◽  
Transverse Strain ◽  
Optimum Level ◽  
Micro Ct ◽  
Micro Computed Tomography ◽  
The Stability ◽  
Transverse Strains ◽  
Longitudinal Strains ◽  
Break Load

In the present work, the effects of preloading on the tensile properties of braided polyarylate fiber ropes were investigated experimentally. Four kinds of samples with different pitch lengths were tested with designed preload levels. The deformation responses of the ropes were captured using digital image correlation (DIC) and micro-computed tomography (micro-CT). It is shown that the nonlinearity in the mechanical behavior of the ropes can be almost eliminated post-preloading with one cyclic loading, and the transverse strains are much greater than the longitudinal strains due to the compaction of rope structure because of the spiral interlaced path of braid yarns. The rope with shorter pitch length (larger braid angle) has larger longitudinal strain and smaller transverse strain due to the higher yarn crimp rate and tighter yarns, respectively. The preload level is the most important parameter for preloading. The chord modulus of the ropes reached an optimum level at the preload level of 40% break load, and the tensile strength can be increased by 15% at the preload level of 50% break load. Moreover, the stability of the tensile properties could be accelerated at the higher preload level. Consequently, preloading is vital to improve the tensile properties of braided polyarylate fiber ropes, with a preload level at least of 40% break load and 10 cyclic loadings.

Three-Dimensional Strain Fields in a Uniform Osteotomy Gap

1986 ◽  
Vol 108 (3) ◽  
pp. 273-280 ◽  
Author(s):  
A. M. DiGioia ◽  
E. J. Cheal ◽  
W. C. Hayes
Keyword(s):  
Longitudinal Strain ◽  
Large Strain ◽  
Geometric Analysis ◽  
Local Strain ◽  
Material Model ◽  
Nonlinear Material ◽  
In Vivo Study ◽  
Strain Fields ◽  
Longitudinal Strains

Stable internal fixation usually results in a unique histological healing pattern which involves direct cortical reconstruction and an absence of periosteal bridging callus. While it has been suggested that longitudinal interfragmentary strain levels control this healing pattern, the complex, multiaxial strain fields in the interfragmentary region are not well understood. Based on an in-vivo study of gap healing in the sheep tibia by Mansmann et al. [13], we used several finite element models of simplified geometry to: 1) explore modeling assumptions on material linearity and deformation kinematics, and 2) examine the strain distribution in a healing fracture gap subjected to known levels of interfragmentary strain. We found that a general nonlinear material, nonlinear geometric analysis is necessary to model an osteotomy gap subjected to a maximum longitudinal strain of 100 percent. The large displacement, large strain conditions which were used in the in-vivo study result in complex, multiaxial strain fields in the gap. Restricting the maximum longitudinal strain to 10 percent allows use of a linear goemetric formulation without compromising the numerical results. At this reduced strain level a linear material model can be used to examine the extent of material yielding within a homogeneous osteotomy gap. Severe local strain variations occurred both through the thickness of the gap and radially from the endosteal to periosteal gap surfaces. The bone/gap interface represented a critical plane of high distortional and volumetric change and principal strain magnitudes exceeded the maximum longitudinal strains.

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