Stress and Strain Distribution in Hypertensive and Normotensive Rat Aorta Considering Residual Strain

1996 ◽  
Vol 118 (1) ◽  
pp. 62-73 ◽  
Author(s):  
Takeo Matsumoto ◽  
Kozaburo Hayashi
Keyword(s):  
Residual Stresses ◽  
Wall Thickness ◽  
Axial Stress ◽  
Circumferential Stress ◽  
Circumferential Direction ◽  
Wall Thickening ◽  
Left Renal Artery ◽  
Stress And Strain ◽  
Stress Distributions ◽  
Cross Sectional

The effects of hypertension on the stress and strain distributions through the wall thickness were studied in the rat thoracic aorta. Goldblatt hypertension was induced by constricting the left renal artery for 8 weeks. Static pressure-diameter-axial force relations were determined on excised tubular segments. The segments were then sliced into thin ring specimens. Circumferential strain distributions were determined from the cross-sectional shape of the ring specimens observed before and after releasing residual stresses by radial cutting. Stress distributions were calculated using a logarithmic type of strain energy density function. The wall thickness at the systolic blood pressure, Psys, significantly correlated with Psys. The mean stress and strain developed by Psys in the circumferential direction were not significantly different between the hypertensive and control aortas, while those in the axial direction were significantly smaller in the hypertensive aorta than in the control. The opening angles of the stress-free ring specimens correlated well with Psys. The stress concentration factor in the circumferential direction was almost constant and independent of Psys, although the stress distributions were not uniform through the wall thickness. Histological observation showed that the wall thickening caused by hypertension is mainly due to the hypertrophy of the lamellar units of the media, especially in the subintimal layer where the stress increase developed by hypertension is larger than in the other layers. These results indicate that: (a) the aortic wall adapts itself to the mechanical field by changing not only the wall dimensions but also the residual stresses, (b) this adaptation is primarily related to the circumferential stress but not to the axial stress, and (c) the aortic smooth muscle cells seem to change their morphology in response to the mechanical stress.

X-ray residual stress analysis of cylindrically curved surfaces—estimation of circumferential distributions of residual stresses

2003 ◽  
Vol 38 (5) ◽  
pp. 459-468 ◽  
Author(s):  
T Oguri ◽  
K Murata ◽  
Y Sato
Keyword(s):  
Residual Stresses ◽  
Least Squares Method ◽  
Stress Measurement ◽  
Incident Angle ◽  
Axial Stress ◽  
Circumferential Stress ◽  
Distribution Functions ◽  
Scanning Method ◽  
X Ray ◽  
Reference Axis

A new measuring technique utilizing X-ray diffraction is proposed in order to estimate the circumferential distributions of residual stresses on convex/concave cylindrical surfaces. This technique requires neither tilting X-ray beams in the circumferential direction in which the X-ray incident angle tends to be limited nor adjusting the normal of the irradiation area to the reference axis of the ψ angle. The circumferential distributions of the circumferential stress and of the axial stress are estimated from the diffraction angles at ψ = 0° and the axial stresses obtained by the stress measurement on multiple inclined areas on the cylindrical surfaces under the configuration of the axial stress measurement using the iso-inclination scanning method. This estimate technique was applied to two round bars of steel, one with circumferential distributions of the residual stresses and the other with almost uniform stresses. The distribution functions of the residual stresses were expanded to a couple of Fourier series, and the coefficients of them were determined by the least-squares method. The estimated distributions of the residual stresses were in good agreement with the actual ones.

Effects of Pipe Dimensions and Outer Surface-Buttering Weld Conditions on Residual Stress Distributions

2008 ◽  
Author(s):  
Nobuyoshi Yanagida
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Outer Surface ◽  
Hoop Stress ◽  
Axial Stress ◽  
Butt Joint ◽  
Stress Distributions ◽  
The Finite Element Method ◽  
Butt Joints ◽  
Inner Surface

Effects of pipe dimensions and outer surface-buttering weld conditions on residual stress distributions were evaluated using the finite element method. Residual stresses were analyzed for 508–mm-diameter (500A) pipe 38.1 mm thick, 508–mm-diameter (500A) pipe 15.1 mm thick, and 267–mm-diameter (250A) pipe 15.1 mm thick. After the residual stresses at pipe butt joints were analyzed, residual stresses at these joints subjected to the outer surface-buttering welds were analyzed. Residual stresses were determined for various weld widths, thicknesses, and heat inputs. These analyses indicate that tensile axial stress occurred at inner surface of the pipe butt joint and that it decreased with increasing the outer surface buttering-weld width or heat input. They also indicate that compressive hoop stress occurred at inner surface of the joint and that outer surface-buttering weld increased it. The outer surface-buttering weld conditions that generate compressive residual stress at the inner surface of the pipe butt joints were determined.

Formulas for Generating Prescribed Residual Stress Distributions in Center-Wound Rolls

1991 ◽  
Vol 58 (3) ◽  
pp. 836-840 ◽  
Author(s):  
Zine-Eddine Boutaghou ◽  
Thomas R. Chase
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Circumferential Stress ◽  
Stress Distributions ◽  
Wound Rolls

Altmann’s equations for describing the residual stresses in center-wound rolled webs are solved to determine the winding stress necessary to produce prescribed residual stress distributions in the finished roll. A solution for constant circumferential stress is expanded to control the peak winding stress. Two example winding problems are discussed.

Non-Euclidean Stress-Free Configuration of Arteries Accounting for Curl of Axial Strips Sectioned From Vessels

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Keiichi Takamizawa ◽  
Yasuhide Nakayama
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Stress Analysis ◽  
Riemannian Geometry ◽  
Axial Stress ◽  
Circumferential Stress ◽  
Arterial Walls ◽  
Physiological Loading ◽  
Residual Strains

It is well known that arteries are subject to residual stress. In earlier studies, the residual stress in the arterial ring relieved by a radial cut was considered in stress analysis. However, it has been found that axial strips sectioned from arteries also curled into arcs, showing that the axial residual stresses were relieved from the arterial walls. The combined relief of circumferential and axial residual stresses must be considered to accurately analyze stress and strain distributions under physiological loading conditions. In the present study, a mathematical model of a stress-free configuration of artery was proposed using Riemannian geometry. Stress analysis for arterial walls under unloaded and physiologically loaded conditions was performed using exponential strain energy functions for porcine and human common carotid arteries. In the porcine artery, the circumferential stress distribution under physiological loading became uniform compared with that without axial residual strain, whereas a gradient of axial stress distribution increased through the wall thickness. This behavior showed almost the same pattern that was observed in a recent study in which approximate analysis accounting for circumferential and axial residual strains was performed, whereas the circumferential and axial stresses increased from the inner surface to the outer surface under a physiological condition in the human common carotid artery of a two-layer model based on data of other recent studies. In both analyses, Riemannian geometry was appropriate to define the stress-free configurations of the arterial walls with both circumferential and axial residual strains.

Improved Mathematical Models of Thermal Residual Stresses in Functionally Graded Adhesively Bonded Joints: A Critical Review

2019 ◽  
Vol 7 (4) ◽  
pp. 367-416 ◽  
Author(s):  
M. Kemal Apalak ◽  
M. Didem Demirbas
Keyword(s):  
Residual Stresses ◽  
Mathematical Models ◽  
Adhesive Layer ◽  
Adhesive Joints ◽  
Functionally Graded ◽  
Stress And Strain ◽  
Stress Distributions ◽  
Adhesively Bonded ◽  
Thermal Residual Stresses ◽  
Derivatives Of

Functionally graded material (FGM) concept has been applied successfully in order to improve/design heat transfer, electric and electronic conductivity, static and dynamic strengths of adhesive joints by reliving stress distributions in both adhesive and adherend materials. This new approach relies on tailoring material composition of adhesive and adherends along one or more coordinate directions. Thermal residual stresses in adhesive joints are a vital issue in terms of the joint strength. FGM concept also allows to relieve/control thermal residual stresses encountered in adhesive joints due to mismatches between coefficients of thermal expansion of adhesive and adherend materials. Mathematical models and solutions on the thermal residual stress analysis have been continuously improved. This paper reviews the current status of mathematical models, and offers an improved mathematical model and numerical solution method by considering two-dimensional thermal stress and deformation states of adhesively bonded bi-directional functionally graded clamped plates subjected to an in-plane heat flux along one of the ceramic edges. This mathematical model assumes the material properties of the functionally graded plates to vary with a power law along two in-plane directions and not through the plate thickness direction, in particular, considers the spatial derivatives of thermal and mechanical properties of the material, and enables the investigation of the effects of the bi-directional composition variations and spatial derivative terms on the displacement, strain and stress distributions. The heat conduction and Navier equations describing the twodimensional thermo-elastic problem are discretized using finite-difference method, and the set of linear equations are solved using the pseudo singular value method. The functionally graded plates relieve both stress and strain distributions and levels in the adhesive layer and in the plates even though the adhesive layer is still ungraded. The spatial derivatives of mechanical and thermal properties of the local material become more effective on the strain and stress distributions of the plates and adhesive layer. The model, disregarding these derivative terms, exhibits sensitivity to small changes in the compositional gradients (n, m) by adjusting the variations of ceramic volume fraction along the x - and y-directions, respectively, and instability in the calculation of stress and strain distributions and levels. However, the improved model with material derivatives, which considers the effects of these derivative terms, predicts stress and strain distributions and levels complying with changes in the compositional gradient exponents.

Characteristics, Causes, and Management of Circumferential Stress-Corrosion Cracking

2014 ◽  
Author(s):  
Raymond R. Fessler ◽  
Millan Sen
Keyword(s):  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Axial Stress ◽  
Circumferential Stress ◽  
The United States ◽  
Maximum Tensile Stress ◽  
Corrosion Cracking ◽  
Poisson Effect ◽  
Bent Pipe

While much more rare than axial stress-corrosion cracking (SCC), circumferential SCC (CSCC) has been observed in pipelines in Canada, the United States, and two European countries. In some cases, the CSCC has been of sufficient size to cause in-service leaks. Because the orientation of stress-corrosion cracks invariably is perpendicular to the maximum tensile stress, the axial stresses at the locations of the cracks must have been greater than the hoop stress. The Poisson effect and thermal effects can account for about half of the axial stresses. Evidence from the field suggests that there are three probable sources of additional axial stresses that can promote CSCC: residual stresses in bent pipe, axial stresses caused by movement of unstable soil on slopes, and residual stresses opposite rock dents. CSCC can be managed by one or a combination of the following procedures: direct assessment (DA), in-line inspection (ILI), or hydrostatic testing. Guidance for selection of sites for DA is derived from industry experience, which was determined from responses to a questionnaire and published reports. The capabilities of ILI to detect circumferential stress-corrosion cracks or the conditions that promote them are summarized. The benefits and limitations of hydrostatic testing also are described. A method for calculating the size of circumferential flaws that can cause ruptures is presented and compared with service experience. That information can provide useful guidance for ILI requirements and decisions about which flaws need to be removed immediately.

Surrounding tissues affect the passive mechanics of the vessel wall: theory and experiment

2007 ◽  
Vol 293 (6) ◽  
pp. H3290-H3300 ◽  
Author(s):  
Yi Liu ◽  
Charles Dang ◽  
Marisa Garcia ◽  
Hans Gregersen ◽  
Ghassan S. Kassab
Keyword(s):  
Vessel Wall ◽  
Circumferential Stress ◽  
Stretch Ratio ◽  
Surrounding Tissue ◽  
Stress And Strain ◽  
Cross Sectional ◽  
Vascular Physiology ◽  
Intravascular Pressure

The stress and strain in the vessel wall are important determinants of vascular physiology and pathophysiology. Vessels are constrained radially by the surrounding tissue. The hypothesis in this work is that the surrounding tissue takes up a considerable portion of the intravascular pressure and significantly reduces the wall strain and stress. Ten swine of either sex were used to test this hypothesis. An impedance catheter was inserted into the carotid or femoral artery, and after mechanical preconditioning pressure-cross-sectional area relations were obtained with the surrounding tissue intact and dissected away (untethered), respectively. The radial constraint of the surrounding tissue was quantified as an effective perivascular pressure on the outer surface of the vessel, which was estimated as 50% or more of the intravascular pressure. For carotid arteries at pressure of 100 mmHg, the circumferential wall stretch ratio in the intact state was ∼20% lower than in the untethered state and the average circumferential stress was reduced by ∼70%. For femoral arteries, the reductions were ∼15% and 70%, respectively. These experimental data support the proposed hypothesis and suggest that in vitro and in vivo measurements of the mechanical properties of vessels must be interpreted with consideration of the constraint of the surrounding tissue.

FE simulation study of deep drawing process of SUS304 cups having no delayed cracks under enhanced blank holding force

2019 ◽  
Vol 234 (1-2) ◽  
pp. 84-94 ◽  
Author(s):  
Chin Joo Tan ◽  
Afshin Aslian
Keyword(s):  
Wall Thickness ◽  
Deep Drawing ◽  
Circumferential Stress ◽  
Wall Thickening ◽  
Drawing Process ◽  
High Concentration ◽  
Deep Drawing Process ◽  
Blank Holding Force ◽  
Force Range ◽  
Hoop Stresses

In the experiment, delayed cracks in deep drawing processes of metastable stainless steel SUS304 cylindrical cups were prevented using elevated blank holding force aided by nanolubrication. Besides tensile residual hoop stresses, the elimination of the cracks was also attributed to the change in wall thickening profile along the wavy cup edges. The wall thickening is a result of the high circumferential stress acting in the flange, leading to the high concentration of deformation-induced martensite and high risk of cracks. The amount of increase in wall thickness in the valleys along the edge during the deep drawing process was higher than the peaks at low blank holding force range due to shorter heights. Therefore, the portions of blank equivalent to the valleys were subject to higher holding force during the process, resulting in decrease in degree of wall thickening with increase in height for blank holding force up to 25 kN. However, the wall thickening and the height increased at blank holding force of 28 kN due to the same amount of increase in wall thickness in both valleys and peaks, resulting in a larger contacting area and lower holding force. Therefore, the wall thickness in the valleys sharply increased, and the formation of the cracks persists. Within the crack-free range, that is, from 29 to 31 kN, both the heights and wall thickening decreased. The decrease in frictional force by means of the nanolubrication has facilitated the flow of material into the die, resulting in lower cup height. It also facilitated the flow of materials away from the thick valley regions under the high pressure, resulting in significant decrease in degree of wall thickening. The cracks were prevented. The amount of compression at blank holding force of 32 kN was insufficient to suppress the increase in wall thickening in valleys, resulting in the formation of the cracks again.

Research on the Stress of the Oxide Scales on the Superheater Tubes under Uneven Circumferential Loading

2013 ◽  
Vol 860-863 ◽  
pp. 1398-1401
Author(s):  
Qing Wei Li
Keyword(s):  
Growth Temperature ◽  
Axial Stress ◽  
Circumferential Stress ◽  
Circumferential Direction ◽  
Oxide Scales ◽  
Negative Effects ◽  
Superheater Tube ◽  
Simulated Temperature ◽  
Simulation Results ◽  
Volume Method

Oxide scales have negative effects on the security and economy of supercritical and ultra-supercritical units.The finite volume method was exploited to simulate oxide scales growth temperature on the inside of superheater tube,then the appropriate time and spatial intervals were selected to calculate oxide scales thickness along the circumferential direction with the correspond growth temperature.At last,the stress response of the oxides was simulated with finite element method.The simulated temperature is closed to the analytical temperature, confirming that the simulation results are credible.The results show that the growth temperature rises fast at the beginning and drops in the circumferential direction,which changes rapidly at the 90°. Oxide scales thickness is thinner and thinner in the circumferential direction and changes fast at approximately 90°.Though the magnitude of circumferential stress and axial stress is different, but the trend same.The simulation results can provides a theoretical basis for the failure research of the oxide scales.

Effects of Repair Weld Length on Residual Stress Distribution

2001 ◽  
Vol 124 (1) ◽  
pp. 74-80 ◽  
Author(s):  
P. Dong ◽  
J. Zhang ◽  
P. J. Bouchard
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Axial Stress ◽  
Base Material ◽  
Shell Element ◽  
Element Model ◽  
Outer Diameter ◽  
Stress Distributions ◽  
Axial Tensile

This paper discusses residual stress distributions induced by repairing a stainless steel girth weld in a 19-mm thick pipe of outer diameter 541 mm. In particular, the effects of repair weld circumferential length are examined using finite element modeling. Results for three different repair lengths are presented having circumferential angular spans of 20 deg (short repair), 57 deg (medium repair), and 114 deg (long repair). A special 3-D shell element model is used which facilitates the simulation of multi-pass welds in 3-D piping components. The results shed light on a number of important 3-D residual stress features associated with repairs. Outer surface axial residual stresses in the weld and adjacent base material are tensile along the length of the repair, reach maxima values near the arc start/stop positions, and then drop into compression beyond the repair ends. The short repair develops the highest axial tensile stresses due to the overlay of start/stop effects. The circumferentially remote residual stresses are unaffected by the repairs. At midlength of the repair, profiles of axial stress along the pipe show tensile peaks at ≈40 mm away from the weld centerline; these peaks decrease in magnitude with increasing repair length. However, the medium repair axial stresses show the greatest range of influence along the pipe. The pre-existing original girth weld residual stresses have very little effect on the repair residual stress characteristics. Finally, residual stress measurements on mock-up components are discussed which confirm the validity of the finite element methods used.

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