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1
Elsayed, M. M., M. O. Hendy e E. E. El Soally. "A new approach for the determination of residual stresses in biaxially stressed plates". Journal of Strain Analysis for Engineering Design 28, n. 3 (1 luglio 1993): 181–86. http://dx.doi.org/10.1243/03093247v283181.
Testo completoAbstract (sommario):
This paper presents a modified hole-drilling technique for measuring residual stresses in a finite width plate subjected to biaxial tensile loading. Instead of using a special strain rosette containing three elements, only two strain gauges are used to determine the values of relaxed strains and hence the residual stresses in a biaxially stressed plate. It also gives a new approach which measures the radial relieved strains in two strain gauges mounted on a plate due to drilling a small central hole and then enlarging it. The corresponding residual stresses and their directions are derived.
2
PAVLOVA, I. P., e I. V. BELKINA. "PARAMETRIC RESEARCH OF RESTRAINED STRAINS AND STRESSES OF SELF-STRESSED FIBER-REINFORCED CONCRETE AT THE STAGE OF EXPANSION". Building and reconstruction 108, n. 4 (2023): 81–92. http://dx.doi.org/10.33979/2073-7416-2023-108-4-81-92.
Testo completoAbstract (sommario):
One of the main advantages of self-stressed concrete is its ability to compensate for one of the main disadvantages inherent in mineral binders – shrinkage strains. However, approaches to predicting the properties of self-stressed concrete are not universal, since they are based mainly on phenomenological approaches and empirical dependencies. The main approaches to predicting strains and stresses arising in expansive concrete are energy- and deformation approaches. A number of researchers confirm the effectiveness of applying the deformation approach to determine intrinsic strains and stresses. Modification of the model for determining its own stresses and strains made it possible to move from the case of uniaxial bar reinforcement to two- and three-axis-limited elements. Based on the provisions of the deformation approach, a deformation model was proposed to determine the intrinsic strains and stresses of self-stressed fiber-reinforced concrete. The main prerequisites and assumptions of the proposed model are formulated. A block diagram of the algorithm of the iterative procedure is given, which makes it possible to calculate the intrinsic strains and stresses of self-stressed fiber-reinforced concrete. Parametric studies of self-strains and stresses of self-stressed fiber-reinforced concrete at the stage of expansion were carried out. The normalized dependences of the bounded strains on the varied parameters are presented. The area of effective use of steel fibers to achieve "binding" effect of free expansion in self-stressed concrete of different energy-activity has been determined. Influence of change of introduced fiber amount on development of bound strains of self-stressed concrete at different time intervals has been determined. The obtained results can be used in design, educational and research institutions.
3
Miner, Valerie, e Carol Anshaw. "Stresses and Strains". Women's Review of Books 19, n. 9 (giugno 2002): 14. http://dx.doi.org/10.2307/4023935.
Testo completo
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Xing, Yufeng, Lingyu Meng, Zhiwei Huang e Yahe Gao. "A Novel Efficient Prediction Method for Microscopic Stresses of Periodic Beam-like Structures". Aerospace 9, n. 10 (26 settembre 2022): 553. http://dx.doi.org/10.3390/aerospace9100553.
Testo completoAbstract (sommario):
This paper presents a novel superposition method for effectively predicting the microscopic stresses of heterogeneous periodic beam-like structures. The efficiency is attributed to using the microscopic stresses of the unit cell problem under six generalized strain states to construct the structural microscopic stresses. The six generalized strain states include one unit tension strain, two unit bending strains, one unit torsion strain, and two linear curvature strains of a Timoshenko beam. The six microscopic stress solutions of the unit cell problem under these six strain states have previously been used for the homogenization of composite beams to equivalent Timoshenko beams (Acta. Mech. Sin. 2022, 38, 421520), and they are employed in this work. In the first step of achieving structural stresses, two stress solutions concerning linear curvatures are transformed into two stress solutions concerning unit shear strains by linearly combining the stresses under two unit bending strains. Then, the six stress solutions corresponding to six generalized unit beam strains are combined together to predict the structural microscopic stresses, in which the six stress solutions serve as basic stresses. The last step is to determine the coefficients of these six basic stress solutions by the principle of the internal work equivalence. It is found that the six coefficients, in terms of the product of the inverse of the effective stiffness matrix and the macroscopic internal force column vector, are the actual generalized strains of the equivalent beam under real loads. The obtained coefficients are physically reasonable because the basic stress solutions are produced by the generalized unit strains. Several numerical examples show that the present method, combining the solutions of the microscopic unit cell problem with the solutions of the macroscopic equivalent beam problem, can accurately and effectively predict the microscopic stresses of whole composite beams. The present method is applicable to composite beams with arbitrary periodic microstructures and load conditions.
5
Hyde, T. H., R. Sabesan e S. B. Leen. "Approximate Prediction Methods For Multiaxial Notch Stresses and Strains Under Elastic-Plastic and Creep Conditions". Journal of Strain Analysis for Engineering Design 40, n. 6 (1 agosto 2005): 535–48. http://dx.doi.org/10.1243/030932405x16016.
Testo completoAbstract (sommario):
This paper describes general techniques for predicting multiaxial notch stresses and strains under elastic-plastic and creep conditions. The Neuber method, which is often used in elastic-plastic analysis, has been adapted and extended for predicting creep equivalent notch stresses and strains, based on a time-stepping integration scheme. A linear interpolation method, often used in creep analysis, is adapted and extended for predicting elastic-plastic equivalent stresses and strains. Then notch principal stresses and strains are obtained by applying plasticity theory in combination with assumptions concerning the ratios of the stress or strain components. The accuracy of the predicted equivalent and principal stress and strain values are assessed by comparing predictions based on them with results obtained from finite element analyses.
6
Frishter, Lyudmila. "Comparison of the stress and strain intensity factors for the corner area of the structure boundary". MATEC Web of Conferences 193 (2018): 03029. http://dx.doi.org/10.1051/matecconf/201819303029.
Testo completoAbstract (sommario):
The stress-strain state of structures in areas with corner cut-outs and cuts of boundaries features the occurrence of areas of stress concentration and requires assessment of strength and reliability of facilities, which is a relevant task in engineering practice. Theoretical analysis of stress-strain state (SSS) of corner cut-outs zones of the area boundary is reduced to the study of singular solutions of the elasticity theory problem with exponential features. At that, the concept of stress or strain concentration in an irregular point of the area boundary is meaningless. This paper considers the stress-strain state in the vicinity of the top of the corner cut-out of the flat area boundary, which is recorded using the intensity factors as limit values of stresses and strains. We give two approaches for obtaining the limit values for stress and strain in the vicinity of an irregular point of the plane area boundary using the stress intensity factors and the strain intensity factors. The stress-strain state in the corner cut-outs zone of structures and buildings boundary recorded in the form of limit values of stresses and strains may further be used to determine and record the influence of changing the factors of intensity of stresses and strains on SSS of structures, which is a separate task of solid mechanics. The difference in the expressions of stresses and displacements obtained for limit values of stresses and strains determines practical significance of the work when carrying out experiments and at determination of critical values of stresses and strains.
7
Johnson, A. R., T. Chen e J. L. Mead. "Modeling Step—Strain Relaxation and Cyclic Deformations of Elastomers". Rubber Chemistry and Technology 75, n. 2 (1 maggio 2002): 333–45. http://dx.doi.org/10.5254/1.3544982.
Testo completoAbstract (sommario):
Abstract Data for step—strain relaxation and cyclic compressive deformations of highly viscous short elastomer cylinders are modeled using a large strain rubber viscoelastic constitutive theory with a rate—independent friction stress term added. In the tests, both small and large amplitude cyclic compressive strains, in the range of 1% to 10%, were superimposed on steady state compressed strains, in the range of 5% to 20%, for frequencies of 1 and 10 Hz. The elastomer cylinders were conditioned prior to each test to soften them. The constants in the viscoelastic—friction constitutive theory are determined by employing a nonlinear least-squares method to fit the analytical stresses for a Maxwell model, which includes friction, to measured relaxation stresses obtained from a 20% step—strain compression test. The simulation of the relaxation data with the nonlinear model is successful at compressive strains of 5%, 10%, 15%, and 20%. Simulations of hysteresis stresses for enforced cyclic compressive strains of 20%±5% are made with the model calibrated by the relaxation data. The predicted hysteresis stresses are lower than the measured stresses.
8
Gu, Randy J., e Yung-Li Lee. "A New Method for Estimating Nonproportional Notch-Root Stresses and Strains". Journal of Engineering Materials and Technology 119, n. 1 (1 gennaio 1997): 40–45. http://dx.doi.org/10.1115/1.2805971.
Testo completoAbstract (sommario):
This paper presents a generalized two-step endochronic approach for estimating notch stresses and strains based on elastic stress solutions. In the first stress-controlled step, notch root strains are calculated from elastic stresses using a conventional uniaxial method, such as Glinka’s energy density method and Neuber’s rule. In the second strain-controlled step notch root stresses corresponding to the estimated local strains are calculated from the given material properties. Both stress-controlled and strain-controlled algorithms based on endochronic plasticity theory are presented herein. The proposed method is used to calculate multiaxial strains under monotonie and nonproportional loads. Various geometric constraints (plane stress, plane strain, and intermediate level) are also examined. The results are compared with experimental measurements by other researchers and with predictions from other models.
9
Ezendiokwere, Nnamdi E., Victor J. Aimikhe, Adewale Dosunmu e Ogbonna F. Joel. "Influence of depth on induced geo-mechanical, chemical, and thermal poromechanical effects". Journal of Petroleum Exploration and Production Technology 11, n. 7 (14 maggio 2021): 2917–30. http://dx.doi.org/10.1007/s13202-021-01174-6.
Testo completoAbstract (sommario):
AbstractDelivering efficient and cost-effective drilled and excavated holes require effective prediction of instability along the hole profile. Most drilled and excavated hole stability analyses in the literature are performed for a given zone without considering the influence of depth. This study focused on determining the influence of depth on induced geo-mechanical, chemical, and thermal stresses and strains in drilled or excavated holes. To this end, a new porochemothermoelastic model was developed based on extended poroelastic theory, and the developed model was employed in determining induced strains and stresses for an oil and gas well case study, using data from the literature. The study delineated the different significance levels of geo-thermal-, chemical-, and thermal-induced strains and stresses as depth increased. From the results obtained, it was clear that at shallow depths, chemically induced strains and stress were the most significant formation perturbations responsible for instability of drilled and excavated holes. On the other hand, at deeper depths, geo-mechanical-induced strains and stress were the most predominant. Comparatively, thermally induced strains and stresses were found to be the least significant formation perturbations responsible for instability of drilled and excavated holes. For this case study, the results indicated that chemical strains and stresses were more prominent at depths below 170 m, accounting for more than 50% of the total stresses and strains. At 170 m, both chemical and geo-mechanical stress and strain had equal contributions to the overall stress and strain. However, as depth increased, the percentage contribution of the geo-mechanical component increased and accounted for about 80% of the total strains and stresses at 1000 m, which increased to 98.48% at depths of 6000 m and beyond. The findings of this study will provide guide for future studies on the application of extended poroelasticity theory in solving instability problems of drilled and excavated holes.
10
Pyzalla, Anke R., Björn Reetz, Alain Jacques, Jean-Pierre Feiereisen, Olivier Ferry, Thomas Buslaps e Walter Reimers. "In-situ investigation of strain relaxation in an Al/Si–MMC using high energy synchrotron radiation". International Journal of Materials Research 95, n. 7 (1 luglio 2004): 624–30. http://dx.doi.org/10.1515/ijmr-2004-0119.
Testo completoAbstract (sommario):
Abstract Thermal and mechanical loading induce phase specific strains/stresses in MMCs. At elevated temperature part of the phase-specific strains/stresses relax. The relaxation of the phase-specific strains/stresses is determined by in-situ experiments using white high-energy synchrotron radiation. The experiments reveal that such time-resolved strain measurements are possible and that short-time phenomena can be accessed using white high-energy synchrotron radiation. The elastic strain relaxation behavior is similar for all lattice planes accessed. The influence of the temperature on the characteristic relaxation time is determined. The characteristic relaxation time appears to be independent of the amount of plastic deformation the sample suffers before strain/stress relaxation.
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Ghasemi Nejhad, Mehrdad N., Chiling Pan e Hongwei Feng. "Intrinsic Strain Modeling and Residual Stress Analysis for Thin-Film Processing of Layered Structures". Journal of Electronic Packaging 125, n. 1 (1 marzo 2003): 4–17. http://dx.doi.org/10.1115/1.1512295.
Testo completoAbstract (sommario):
Residual stresses develop due to intrinsic and extrinsic strains that form during the processing. Extrinsic strains can be determined using coefficient of thermal expansion, material properties, and processing conditions. An “Equivalent Reference Temperature (ERT)” technique is described and used to model and evaluate the intrinsic strains. piezoelectric microelectromechanical systems (P-MEMS) are considered in this work. Laminate theory with three-dimensional state of stress and strain is used to evaluate residual stresses using the ERT model. In finite element analysis (FEA), the residual stresses and strains of multi-layer P-MEMS structures deposited layer-by-layer during processing, are simulated using the “element birth-and-death” approach. The evaluated residual stresses for a simplified geometry using ANSYS three-dimensional FEA and analytical analysis employing three-dimensional laminate theory are presented along with their corresponding experimental results. A user-friendly software based on the 3-D laminate theory is developed and installed on the Internet. The “equivalent reference temperature” as well as residual stresses and strains can be determined using this software. The level of residual stresses and strains of P-MEMS depend upon various factors such as geometrical design, material selection, and process conditions.
12
McMahon, Darryl. "Theory for highly stressed thick-walled elastic spheres and their vibration without small strain approximations". Journal of the Acoustical Society of America 154, n. 4_supplement (1 ottobre 2023): A262. http://dx.doi.org/10.1121/10.0023471.
Testo completoAbstract (sommario):
This paper considers how the radii and vibration of an elastic thick-walled sphere is affected by high stresses imposed by high external pressures or by high internal pressures. For simplicity, the sphere consists of idealized Hookean material allowing unlimited compression or expansion. The sphere is filled by material with an isotropic pressure that generally differs from the pressure on the outer surface of the sphere. The analysis includes large strain nonlinear curvature effects where, unlike linear elasticity theory, the difference in radial and tangential strains is not small compared to those strains. Despite the sphere’s robustness, destructive physical consequences are predicted for nonzero Poisson coefficients where, for instance, a high-pressure tank inner stresses make the inner radius approach the less stressed outer radius. This would be avoided if the Poisson coefficient changed with large strains and approached zero. To model the effect of high stresses and strains on breathing mode vibration, an effective spring constant is derived from quadratic radius deviations of the system potential energy from equilibrium. Insights from analysis avoiding linear elasticity approximations may be applicable to improved understanding of deep-sea marine creature survival, improved underwater vessel design for large depths, and safer containers of fluids at high pressures.
13
Ogawa, Masaru. "Proposal of an Eigen-Strain Estimation for Determination of Residual Stresses Considering the Influence of Machining". Advanced Materials Research 891-892 (marzo 2014): 1225–30. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.1225.
Testo completoAbstract (sommario):
In order to assure structural integrity for mechanical structures, it is indispensable to estimate three-dimensional residual stresses quantitatively to asses a crack growth rate of an observed crack. Now, the neutron diffraction method and the DHD (Deep Hole Drilling) method have been proposed to evaluate stress gradient in the thickness direction. However, estimated stresses by these methods can not be input to the FEM (Finite Element Method) model that has been widely used at design time for the assessment of the structural integrity. Then, the eigen-strain method has been proposed. In this method, three-dimensional residual stresses are calculated by an elastic FEM analysis from eigen-strains those can be evaluated quantitatively by an inverse analysis from released strains measured by strain gauges while the geometric boundary condition or material properties of the object has been changed. However, inelastic strains are newly created on the machined surface, the estimation accuracy of this method becomes relatively poor because the eigen-strains before and after measurements have to be the same. In this study, a calculation technique to evaluate not only initial eigen-strains but also processing strains is shown, and effectiveness of this method is demonstrated numerically in the bead flush method based on the eigen-strain method. Although estimation accuracy of processing strains was poorer, three-dimensional residual stresses for whole region could be evaluated accurately from measured strains without measurement errors.
14
Moore, Tara L. A., e Lorna J. Gibson. "Fatigue Microdamage in Bovine Trabecular Bone". Journal of Biomechanical Engineering 125, n. 6 (1 dicembre 2003): 769–76. http://dx.doi.org/10.1115/1.1631584.
Testo completoAbstract (sommario):
Microdamage, in the form of small cracks, may accumulate in trabecular bone loaded in fatigue. Specimens of bovine trabecular bone were loaded in compressive fatigue at one of four normalized stresses and loading was stopped after the specimens reached one of six maximum strains. Microdamage was identified using a fluorochrome staining technique, and microdamage parameters, including the number of damaged trabeculae and the damaged area fraction, were measured. No microdamage was observed during loading to strains below the yield strain; at higher strains, all microdamage parameters increased with increasing maximum compressive strain. Few significant differences were observed in the type or amount of microdamage accumulation between specimens loaded to the same maximum strain at different normalized stresses; however, more trabecular fractures were observed at high numbers of cycles, which corresponded to low normalized stresses.
15
BONIFAZ, E. A., e N. L. RICHARDS. "STRESS–STRAIN EVOLUTION IN CAST IN-738 SUPERALLOY SINGLE FUSION WELDS". International Journal of Applied Mechanics 02, n. 04 (dicembre 2010): 807–26. http://dx.doi.org/10.1142/s1758825110000767.
Testo completoAbstract (sommario):
A three-dimensional finite element elastic–plastic model was developed to study localized plastic strains and residual stresses that exist in a body that has previously been subjected to nonuniform temperature changes. The mechanical model was used to compute the evolution of plastic strains and residual stresses of welded material. The thermal gradient histories calculated during the GTA welding of cast IN-738LC alloys were imposed as load conditions on structural calculations. It can be clearly seen that at constant heat input, the level of plastic strains and the level of residual (Mises) stresses increase with welding speed. The model predicts highest residual stresses in regions of highest elastic strains, in agreement with conventional phenomenological material models where the macroscopic residual stress is always directly related to the macroscopic elastic strain. The highest residual stresses are located at the fusion line (where coarser dendrite secondary arm spacing exist); and the highest plastic strains are located at centerline (where finer dendrite secondary arm spacing exist). The calculations were performed using ABAQUS® FE code on the basis of a time-increment Lagrangian formulation.
16
Chang, Chia Lung, Yan Huo Kao, You Lung Jao e Chih Laing Chang. "Residual Stress Measurements of Cylindrical Parts by Hole Drilling Strain Gage Method". Applied Mechanics and Materials 311 (febbraio 2013): 462–66. http://dx.doi.org/10.4028/www.scientific.net/amm.311.462.
Testo completoAbstract (sommario):
Hole drilling strain gage method is a semi-destructive measurement. The method is most commonly used to measure residual stresses. The relieved strains are measured around the drilled hole, and the residual stresses are estimated by the mechanical relationship between relieved strains and residual stresses as well calibration coefficients. The calibration coefficients indicate the relieved strains due to unit stresses within the hole depth. Finite element method is always used to determine the calibration coefficients, and the analytical model is based on the infinite plate. But the geometrical shape and size of cylindrical part are different from the infinite plate. The relieved strains around the drilled hole are different too. Finite element model of the cylindrical part is constructed to obtain the hole drilling calibration coefficients. The measurement of residual stresses in a cylindrical part subject to axial loading calculated by calibration coefficients of both infinite plate and cylindrical part model are compared to show the difference.
17
D. D’Lima, Darryl, Peter C. Chen e Clifford W. Colwell Jr. "Osteochondral Grafting: Effect of Graft Alignment, Material Properties, and Articular Geometry". Open Orthopaedics Journal 3, n. 1 (6 agosto 2009): 61–68. http://dx.doi.org/10.2174/1874325000903010061.
Testo completoAbstract (sommario):
Osteochondral grafting for cartilage lesions is an attractive surgical procedure; however, the clinical results have not always been successful. Surgical recommendations differ with respect to donor site and graft placement technique. No clear biomechanical analysis of these surgical options has been reported. We hypothesized that differences in graft placement, graft biomechanical properties, and graft topography affect cartilage stresses and strains. A finite element model of articular cartilage and meniscus in a normal knee was constructed. The model was used to analyze the magnitude and the distribution of contact stresses, von Mises stresses, and compressive strains in the intact knee, after creation of an 8-mm diameter osteochondral defect, and after osteochondral grafting of the defect. The effects of graft placement, articular surface topography, and biomechanical properties were evaluated. The osteochondral defect generated minimal changes in peak contact stress (3.6 MPa) relative to the intact condition (3.4 MPa) but significantly increased peak von Mises stress (by 110%) and peak compressive strain (by 63%). A perfectly matched graft restored stresses and strains to near intact conditions. Leaving the graft proud by 0.5 mm generated the greatest increase in local stresses (peak contact stresses = 6.7 MPa). Reducing graft stiffness and curvature of articular surface had lesser effects on local stresses. Graft alignment, graft biomechanical properties, and graft topography all affected cartilage stresses and strains. Contact stresses, von Mises stresses, and compressive strains are biomechanical markers for potential tissue damage and cell death. Leaving the graft proud tends to jeopardize the graft by increasing the stresses and strains on the graft. From a biomechanical perspective, the ideal surgical procedure is a perfectly aligned graft with reasonably matched articular cartilage surface from a lower load-bearing region of the knee.
18
Andreeva, Nadeshda, Lubov Ryazanova, Larisa Ledova, Ludmila Trilisenko e Tatiana Kulakovskaya. "Stress Resistance of Saccharomyces cerevisiae Strains Overexpressing Yeast Polyphosphatases". Stresses 2, n. 1 (24 gennaio 2022): 17–25. http://dx.doi.org/10.3390/stresses2010002.
Testo completoAbstract (sommario):
Inorganic polyphosphate (polyP) is an important factor in the stress resistance of microorganisms. The polyphosphate-overexpressing strains of yeast S. cerevisiae were used as a model for studying the inter-relationship between stress resistance and polyP level. We compared the polyP level and resistance to the oxidative, manganese, cadmium, and alkaline stresses in parent stain CRN and in strains overexpressing the four yeast polyphosphatases: Ppx1, Ppn1, Ppn2, and Ddp1. Strains overexpressing Ppx1, Ppn1, and Ppn2 have lower polyP content and the strain overexpressing Ddp1 has the same polyP content as the parent strain. The strains overexpressing Ppn1 and Ddp1 show higher resistance to peroxide and manganese. The strain overexpressing Ppx1 showed a decrease in peroxide resistance. The strain overexpressing Ppn2 was more resistant to alkaline and peroxide stresses. A similar increase in resistance to the manganese and peroxide stresses of strains overexpressing Ppn1 and Ddp1, which differ in polyP content, led to the conclusion that there is no direct relationship between polyP content and variations in this resistance. Thus, we speculate about the potential role of inositol pyrophosphates as signaling molecules in stress response.
19
J. J. Lutchko e V. V. Kovalchuk. "DETERMINATION OF TEMPERATURE STRESSES AND STRAINS IN METAL SPANS BRIDGES". Bridges and tunnels: Theory, Research, Practice, n. 4 (2 giugno 2015): 26–36. http://dx.doi.org/10.15802/bttrp2013/26629.
Testo completoAbstract (sommario):
Purpose. For metal bridges topical study of the stress-strain state arising from the effects of variable temperature extremes of the environment, since the last five years rihayutsya observed significant increases ambient temperatures in summer and decrease in winter. Methodology. Using data from experimental measurements of temperaturedistribution on the surface of the beam-honovyh buildings of metal bridges using an analytical model was calculated thermal stresses and deformations tion arising from a given temperature distribution. Findings. Based on the calculated data revealed that statistically undetectable beams having tension level which reaches 30% of the allowable stress. Originality. For the first time were measured distribut temperature on the surface of metal girders bridges and developed a method for determining the temperature , stresses and deformations of the action variable ambient temperatures. Practical value. The analytical method of determining the thermal stresses and strains may be used byengineers of bridges testing station Railways of Ukraine to install and «Ukravtodor» thermo-stressed state beam spans metal bridges.
20
Tipgoes, Manual A., e James P. Trebby. "Job-Related Stresses And Strains In Management Accounting". Journal of Applied Business Research (JABR) 3, n. 3 (31 ottobre 2011): 8. http://dx.doi.org/10.19030/jabr.v3i3.6510.
Testo completoAbstract (sommario):
This paper reports the results of a questionnaire study of National Association of Accountants members regarding the overall amount of stress and strain among management accounting practitioners. The findings of the questionnaire study indicate that job-related stresses and strains in the management accounting area of the profession are moderate. The paper concludes by discussing ways in which management can identify and correct organizational causes which appear to be major sources of stress and strain.
21
Kuo-Huang, Ling-Long, Yan-San Huang, Shin-Shin Chen e Yi-Ru Huang. "GROWTH STRESSES AND RELATED ANATOMICAL CHARACTERISTICS IN COCONUT PALM TREES". IAWA Journal 25, n. 3 (2004): 297–310. http://dx.doi.org/10.1163/22941932-90000367.
Testo completoAbstract (sommario):
The surface growth strains and the distribution of internal stresses in woody palms, coconut (Cocos nucifera L.), were determined by measuring the strains released by the kerf method using strain gauges. Measurements of the surface strains showed that longitudinal tensile stresses existed at the cortex, while longitudinal compressive stresses existed at the periphery of the central cylinder. These stresses may be generated from the fibers located in the scattered fiber and vascular bundles. In the central cylinder of narrow and wide trunks, both positive and negative stresses were observed, indicating the existence of some tensile and compressive stresses in the trunks. The amount of stress varied from base to top and from periphery to core because of the variation in proportion of the vascular bundles and the fibers, and the cell wall layers of fibers along these points. Furthermore, changes in the angle of vascular bundles and of the fiber microfibrils were correlated with the various tensile and compressive stresses located in the central cylinder of the trunks.
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Sharpe, W. N. "Measurement of Monotonic Biaxial Elastoplastic Stresses at Notch Roots". Journal of Applied Mechanics 58, n. 4 (1 dicembre 1991): 916–22. http://dx.doi.org/10.1115/1.2897708.
Testo completoAbstract (sommario):
Biaxial principal strains were measured at the roots of notches in aluminum specimens with a laser-based interferometric technique. Interference patterns from three tiny indentations spaced 150 or 200 micrometers apart in an orthogonal pattern were monitored with a microcomputer-controlled system. Elastoplastic strains up to one percent were measured in real time with a resolution of 25 microstrain. Procedures were developed for computing the two principal stresses from the incremental strain data using J2-flow theory. The validity of the computations was checked by computing the stresses in smooth tensile specimens. Anisotropy in the thin sheet material leads to errors in the computed lateral stresses (which should be zero), but the maximum deviation of the computed effective stress from the uniaxial stress is only five percent. Three kinds of double-notched specimens were prepared to vary the amount of constraint at the notch root. These were tested under monotonic tensile loading and the biaxial notch-root strains recorded. There is considerable variation among the strains once the elastic limit is passed. This is due primarily to the local inhomogeneity of plastic strain, since the gage length of the measurement is only a few times larger than the grain size of the material. Local biaxial stresses were computed from the measured strains for the three cases. The nature of the material’s stress-strain curve tends to smooth out the variations among tests, particularly when the effective stress is computed. It is discovered that the local stress predicted by the Neuber relation agrees very closely with the measured local effective stress.
23
Kose, Sadi, Murat Guler, Hussain U. Bahia e Eyad Masad. "Distribution of Strains Within Hot-Mix Asphalt Binders: Applying Imaging and Finite-Element Techniques". Transportation Research Record: Journal of the Transportation Research Board 1728, n. 1 (gennaio 2000): 21–27. http://dx.doi.org/10.3141/1728-04.
Testo completoAbstract (sommario):
Because of several orders of magnitude difference between the stiffness of aggregate and binder and the randomness of the binder domain boundaries, the induced deformation under loading can result in a wide distribution of stresses and strains within each of the components. It is expected that although aggregates undergo small strains, most of the strain will accumulate within the binder. Although studies have covered the micromechanics of hot-mix asphalt (HMA), information about the actual typical distribution of asphalt binder domains in HMA and the resulting distribution of stresses and strains is scarce. In this study, advances in imaging techniques are applied to understand the distribution of binder and air voids in selected HMAs. The objective is to determine the strain distribution within the binder using digitized images analyzed with finite-element procedures. This approach captures the image of the specimen cross section and converts the image into finite-element mesh after image processing. The images are converted to finite-element mesh and the finite-element program ABAQUS provides numerical solutions to relate bulk stresses or strains applied to the asphalt mixture to stresses and strains within the binder domains. The results are presented including a summary of the distribution of directional binder film thickness and maximum strains in the mastic domain. Also included is a discussion of the effect of air voids and mineral fillers.
24
Sharpe, William N. "ASME 1993 Nadai Lecture—Elastoplastic Stress and Strain Concentrations". Journal of Engineering Materials and Technology 117, n. 1 (1 gennaio 1995): 1–7. http://dx.doi.org/10.1115/1.2804366.
Testo completoAbstract (sommario):
Elastic stress concentration factors are familiar and easily incorporated into the design of components or structures through charts or finite element analysis. However when the material at the most concentrated location no longer behaves elastically, computation of the local stresses and strains is not so easy. Local elastoplastic behavior is an especially important consideration when the loading is cyclic. This paper summarizes the predictive capability of the Neuber and the Glinka models that relate gross loading to the local stresses and strains. The author and his students have used a unique laser-based technique capable of measuring biaxial strains over very short gage lengths to evaluate the two models. Their results, as well as those from earlier studies by other researchers using foil gages, lead to the general conclusion that the Neuber model works best when the local region is in a state of plane stress and the Glinka model is best for plane strain. There are intermediate levels of constraint that are neither plane stress nor plane strain. This paper presents a recommended practice for predicting the local elastoplastic stresses and strains for any constraint. First, one computes or estimates the initial elastic strains. Then, based on the amount of elastic constraint, one selects the appropriate model to compute the local elastoplastic stresses and strains.
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Matlock, Beth S., Daniel J. Snoha e Scott M. Grendahl. "Using XRD elastic and plastic strain data to evaluate the effectiveness of different cold-working techniques in aerospace materials". Powder Diffraction 24, S1 (giugno 2009): S51—S58. http://dx.doi.org/10.1154/1.3133148.
Testo completoAbstract (sommario):
Generating compressive stresses in aerospace materials is an important consideration for enhancing fatigue life. Shot peening and cold expansion of holes are two techniques for imparting beneficial compressive stresses. X-ray diffraction is a direct method for measuring elastic strains. Diffraction peak widths are an indication of plastic strain. Elastic and plastic strains can be used to better assess the true condition of a component. This paper presents elastic and plastic strain information from shot peened and cold expanded aerospace materials. Examination of surface data showed which shot peened samples had the deeper layer of compressive stresses. Likewise, elastic and plastic strain data enabled successful ranking of the holes in terms of the maximum amount of cold working.
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Zhang, Min, e Xitian Tian. "Residual stresses and strains analysis in press-braking bending parts considering multi-step forming effect". Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 234, n. 4 (1 novembre 2019): 788–800. http://dx.doi.org/10.1177/0954405419883053.
Testo completoAbstract (sommario):
Press-braking bending is a multi-step bending process and widely applied in the aerospace industry. Residual stresses and strains generated during the forming process play an important role in determining its forming parameters and bending path. This work aims to analyze the residual stresses and strains in press-braking bending parts using both the theoretical method and numerical method. First, the analytical model of residual stress and strain is established based on the elastic–plastic bending theory. Second, a fully finite element model of press-braking bending has been developed, and a procedure to simulate the multi-step bending process is presented by using the elastic–plastic large deformation finite element method. The simulation results are then compared with three-point bending experiments in terms of forming force and final shapes of the bent specimens, and excellent agreement is achieved. Finally, the results calculated from the analytical model are compared with the numerical results. The distributions of residual stresses and strains on the finished plate along the length and thickness direction, and particularly the multi-step forming effect on residual stresses and strains, are discussed. It is found that the residual stresses and strains decrease at the initial loading position along the thickness direction during the forming process of subsequent loading positions. With the same punch displacement, the residual stresses and strains at the initial loading position are less than those at the subsequent bending position.
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Sultana, Uzma, Suseelendra Desai e Sravani Pinisetty. "In Vitro Screening for Abiotic Stress Tolerance and Biocontrol Ability of Plant Growth Promoting Strains of Azotobacter and Azospirillum spp." Current Agriculture Research Journal 11, n. 3 (5 gennaio 2024): 840–50. http://dx.doi.org/10.12944/carj.11.3.14.
Testo completoAbstract (sommario):
The selection and deployment of microorganisms in stressed ecosystems with biocontrol ability is a major challenge. In this investigation, we sought to isolate and identify strains of Azotobacter and Azospirillum spp., which could withstand abiotic stresses and possess the potential to serve as biological control against five phytopathogenic fungi. Stress tolerance was evidently less obvious in Azospirillum strains than in Azotobacter strains, when bacterial strains were screened for high temperature (50 °C), salt (7% NaCl), and drought (1.2 MPa). Strains Asp30 and Asp 32 of Azospirillum and Azb 19, Azb20 and Azb27 of Azotobacter were found tolerant to temperature, drought and salinity stresses. Five strains of Azotobacter viz. Azb2, Azb6, Azb10, Azb16 and Azb18 and six strains of Azospirillum viz. Asp2, Asp10, Asp22, Asp30, Asp32 and Asp39 inhibited all the five fungal phytopathogens studied. Therefore, in vitro screening provided the basis for identification and selection of strains with abiotic stress tolerance and biocontrol ability.
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Chanyshev, Anvar I., e Igizar M. Abdulin. "STRESS-STRAIN BEHAVIOR OF ROCK MASS AROUND CYLINDRICAL EXCAVATIONS WITH THE PRESET CAUCHY STRESS STRESSES AND DISPLACEMENTS AT THE BOUNDARIES". Interexpo GEO-Siberia 2, n. 4 (21 maggio 2021): 158–63. http://dx.doi.org/10.33764/2618-981x-2021-2-4-158-163.
Testo completoAbstract (sommario):
The authors solve the problem on the stresses and strains of rock mass around a cylindrical excavation with the preset vectors of the Cauchy stresses and displacements at the boundary. It is assumed that the surrounding rock mass is elastic. Along the cylindrical excavation (free of stresses), displacements are measured as functions of two surface coordinates (polar angle and length along the symmetry axis of the excavation). These measurements are used to determine all components of tensors of stresses and strains at the boundary, and all coordinates of rotation vector. It is shown how this information can be used in the stress-strain analysis of rock mass farther from the excavation.
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Corning, WR, e AA Biewener. "In vivo strains in pigeon flight feather shafts: implications for structural design". Journal of Experimental Biology 201, n. 22 (1 novembre 1998): 3057–65. http://dx.doi.org/10.1242/jeb.201.22.3057.
Testo completoAbstract (sommario):
To evaluate the safety factor for flight feather shafts, in vivo strains were recorded during free flight from the dorsal surface of a variety of flight feathers of captive pigeons (Columba livia) using metal foil strain gauges. Strains recorded while the birds flew at a slow speed (approximately 5-6 m s-1) were used to calculate functional stresses on the basis of published values for the elastic modulus of feather keratin. These stresses were then compared with measurements of the failure stress obtained from four-point bending tests of whole sections of the rachis at a similar location. Recorded strains followed an oscillatory pattern, changing from tensile strain during the upstroke to compressive strain during the downstroke. Peak compressive strains were 2.2+/-0. 9 times (mean +/- s.d.) greater than peak tensile strains. Tensile strain peaks were generally not as large in more proximal flight feathers. Maximal compressive strains averaged -0.0033+/-0.0012 and occurred late in the downstroke. Bending tests demonstrated that feather shafts are most likely to fail through local buckling of their compact keratin cortex. A comparison of the mean (8.3 MPa) and maximum (15.7 MPa) peak stresses calculated from the in vivo strain recordings with the mean failure stress measured in four-point bending (137 MPa) yields a safety factor of between 9 and 17. Under more strenuous flight conditions, feather stresses are estimated to be 1.4-fold higher, reducing their safety factor to the range 6-12. These values seem high, considering that the safety factor of the humerus of pigeons has been estimated to be between 1.9 and 3.5. Several hypotheses explaining this difference in safety factor are considered, but the most reasonable explanation appears to be that flexural stiffness is more critical than strength to feather shaft performance.
30
Breslavsky, Dmytro. "Influence of stresses on deformation process under the irradiation creep and swelling". Bulletin of the National Technical University «KhPI» Series: Dynamics and Strength of Machines, n. 2 (31 dicembre 2021): 23–28. http://dx.doi.org/10.20998/2078-9130.2021.2.245529.
Testo completoAbstract (sommario):
Approaches for describing the deformation of structural elements made from the material, in which radiation creep and swelling strains develop simultaneously, are discussed. The technique for description of irradiation swelling strains, which is used for calculational analysis of stress-strain state arising in structural elements under the joint action of irradiation and thermal-stress fields, is regarded. A complete system of equations of the boundary –initial value problem is presented, in which elastic and thermal strains, strains of radiation creep and swelling are taken into account. Numerical modelling was carried out using the specialized software FEM Creep, in which the boundary value problem is solved by the Finite Element Method, and the initial one is integrated in time by the difference predictor-corrector method. Two forms are given for the equation of state describing the radiation swelling strains: first is for the components of the strain tensor as well as second is prepared for their rates. The hypothesis about the linear correspondence of the received radiation dose and the deformation time, during which radiation swelling strains develop, are analyzed. A number of questions that require answers when using equations with a complex stress state in which the radiation swelling strains are directly depend on stresses, are discussed. Based on the processing of experimental data on the swelling of tubes made of steel 316Ti in the temperature range of 450-460 °С, a form of the equation for the radiation swelling strain rate is proposed, and the constants included in it are determined. Using the example of numerical modelling of the deformation of tubes were made of steel 316Ti and loaded by inner pressure, the applicability of the classical approach for the analysis of the stress-strain state in the presence of radiation swelling strains is shown.
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Safari, Maedeh, Shahrokh Shojaei, Pedram Tehrani e Alireza Karimi. "A patient-specific finite element analysis of the anterior cruciate ligament under different flexion angles". Journal of Back and Musculoskeletal Rehabilitation 33, n. 5 (17 settembre 2020): 811–15. http://dx.doi.org/10.3233/bmr-191505.
Testo completoAbstract (sommario):
BACKGROUND: The main responsibility of the anterior cruciate ligament (ACL) is to restore normal knee kinematics and kinetics. Although so far different research has been carried out to measure or quantify the stresses and strains in the ACL experimentally or numerically, there is still a paucity of knowledge in this regard under different flexion angles of the tibiofemoral knee joint. OBJECTIVE: Understanding the stresses and strains within the ACL under various loading and boundary conditions may have a key asset for the development of an optimal surgical treatment of ACL injury that can better restore normal knee function. This study aimed to calculate the stresses and strains within the ACL under different flexion angles using a patient-specific finite element (FE) model of the human tibiofemoral knee joint. METHODS: A patient-specific FE model of the human tibiofemoral knee joint was established using computed tomography/magnetic resonance imaging data to calculate the stresses and strains in the ACL under different flexion angles of 0, 10, 20, 30, and 45∘. RESULTS: Although the role of the flexion angle in the induced stresses and strains of the ACL was insignificant, the highest stress and strain were observed at the flexion angle of 0∘. The concentration of the stresses and strains regardless of the flexion angles were also located at the proximal end of the ACL, where the clinical reports indicated that most ACL tearing occurs there at the femoral insertion site. CONCLUSIONS: The results have implications not only for understanding the stresses and strains within the ACL under different flexion angles, but also for providing preliminary data for the biomechanical and medical experts in regard of the injuries which may occur to the ACL at relatively higher flexion angles.
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Abishkenov, Maxat, Zhassulan Ashkeyev, Kayrosh Nogaev, Yerbol Bestembek, Kuathan Azimbayev e Ilgar Tavshanov. "On the possibility of implementing a simple shear in the cross-section of metal materials during caliber rolling". Engineering Solid Mechanics 11, n. 3 (2023): 253–62. http://dx.doi.org/10.5267/j.esm.2023.3.004.
Testo completoAbstract (sommario):
The article analyzes the stress-strain state in the zone of plastic deformation during special caliber rolling. The principle of caliber rolling technology is described, which makes it possible to combine shear and compression deformations in the cross-section of metals, alloys, and metal-matrix composites. The analysis results of stresses and strains during shear rolling in a diamond pass, which included compressive strains that had not been considered in previous studies, revealed that localization or point inversion of stresses and strains is observed in the plastic deformation zone. Stress and strain are localized along the minor and major diagonals of the diamond pass.
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Klochkov, Yuriy V., Anatoliy P. Nikolaev, Tatiana A. Sobolesvskaya e Mikhail Yu Klochkov. "Comparative Analysis of Plasticity Theory Algorithms in Finite-Element Calculations of the Rotation Shell". Materials Science Forum 974 (dicembre 2019): 608–13. http://dx.doi.org/10.4028/www.scientific.net/msf.974.608.
Testo completoAbstract (sommario):
Comparative analysis of the use of the defining equations of plasticity theories obtained at the loading step in three ways is performed. In the first method, the relations between strains increments and stresses increments are obtained by differentiating the governing equations of the small elastic-plastic deformations theory between full stresses and strains. In the second method, the authors based on the proportionality hypothesis between the component deviators of strains increments and the component deviators of stresses increments without separating the incremental strain into elastic and plastic parts obtain the determining equations at the loading step. In the third method, the relations between the incremental strain and the stresses increment of the plastic flow theory are used on the basis of the hypothesis about the proportionality of the plastic deformations increments to the components of the stress deviator. Based on the analysis of algorithms for obtaining the constitutive relations and the analysis of the numerical results of the calculation example, preference is given to the second method of obtaining expressions between stress increments and strain increments without separating the latter into elastic and plastic parts.
34
Greenhalf, Jim. "Stresses and strains in city hall". Local Government Studies 11, n. 2 (marzo 1985): 1–7. http://dx.doi.org/10.1080/03003938508433189.
Testo completo
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Nowacki, Jerzy, e Michał Kawiak. "Stresses and strains in soldered joints". Welding International 27, n. 1 (gennaio 2013): 42–47. http://dx.doi.org/10.1080/09507116.2011.600025.
Testo completo
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Comba, Peter. "Strains and stresses in coordination compounds". Coordination Chemistry Reviews 182, n. 1 (febbraio 1999): 343–71. http://dx.doi.org/10.1016/s0010-8545(98)00199-4.
Testo completo
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Nichols, T. Richard. "The Stresses and Strains of Tensegrity". Journal of Motor Behavior 46, n. 3 (14 marzo 2014): 197–98. http://dx.doi.org/10.1080/00222895.2014.880308.
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Nicholson, D. W. "On stresses conjugate to Eulerian strains". Acta Mechanica 165, n. 1-2 (1 ottobre 2003): 87–98. http://dx.doi.org/10.1007/s00707-003-0037-2.
Testo completo
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Praveen Kumar, G., S. K. Mir Hassan Ahmed, Suseelendra Desai, E. Leo Daniel Amalraj e Abdul Rasul. "In Vitro Screening for Abiotic Stress Tolerance in Potent Biocontrol and Plant Growth Promoting Strains of Pseudomonas and Bacillus spp." International Journal of Bacteriology 2014 (6 marzo 2014): 1–6. http://dx.doi.org/10.1155/2014/195946.
Testo completoAbstract (sommario):
Plant growth promoting rhizobacteria (PGPR) has been identified as a group of microbes that are used for plant growth enhancement and biocontrol for management of plant diseases. The inconsistency in performance of these bacteria from laboratory to field conditions is compounded due to the prevailing abiotic stresses in the field. Therefore, selection of bacterial strains with tolerance to abiotic stresses would benefit the end-user by successful establishment of the strain for showing desired effects. In this study we attempted to isolate and identify strains of Bacillus and Pseudomonas spp. with stress tolerance and proven ability to inhibit the growth of potential phytopathogenic fungi. Screening of bacterial strains for high temperature (50°C), salinity (7% NaCl), and drought (−1.2 MPa) showed that stress tolerance was pronounced less in Pseudomonas isolates than in Bacillus strains. The reason behind this could be the formation of endospores by Bacillus isolates. Tolerance to drought was high in Pseudomonas strains than the other two stresses. Three strains, P8, P20 and P21 showed both salinity and temperature tolerance. P59 strain possessed promising antagonistic activity and drought tolerance. The magnitude of antagonism shown by Bacillus isolates was also higher when compared to Pseudomonas strains. To conclude, identification of microbial candidate strains with stress tolerance and other added characteristic features would help the end-user obtain the desired beneficial effects.
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Alzyod, Hussein, e Peter Ficzere. "Using the Photostress method to determine the residual stresses". International Journal of Engineering and Management Sciences 7, n. 2 (14 ottobre 2022): 24–38. http://dx.doi.org/10.21791/ijems.2022.2.2.
Testo completoAbstract (sommario):
Strains and stresses in loaded and photoelastically coated structural members can be determined using the PhotoStress method. The quantitative values of variations in the principal strains (stresses) and their directions could be employed to get the strain or stress components field on the entire coated surface. In the PhotoStress experiment, isochromatic fringes give qualitative and quantitative information. It provides a source of information on the directions and magnitudes of principal strain and principal normal stress on the surface of photoelastic coated parts. This article reviews the principle of using PhotoStress analysis to measure the residual stress and provides the boundary condition of using this method.
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Xie, Jian Feng. "Finite Element Analysis on Stress and Strain of Nickel Electroless Plated Fiber Bragg Grating". Advanced Materials Research 383-390 (novembre 2011): 3893–97. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.3893.
Testo completoAbstract (sommario):
After FBG was nickel electroless plated, the stresses and strains on the FBG and nickel eclectroless plated layer under varied temperature were analyzed in theory. In order to verify the theoretical analysis of stress and strain,a finite element analysis software(ANSYS) was used to simulate the stresses and strains on the FBG and nickel ececltroless plated layer. The results of theoretical analysis matches the ones form simulations well.
42
Wu, Tsung-Tsong, Masahiko Hirao e Yih-Hsing Pao. "Acoustoelastic Birefringences in Plastically Deformed Solids: Part II—Experiment". Journal of Applied Mechanics 58, n. 1 (1 marzo 1991): 18–23. http://dx.doi.org/10.1115/1.2897148.
Testo completoAbstract (sommario):
Ultrasonic experiments are preformed on a carbon steel specimen to determine the change of elastic wave speeds by plastic strains and residual stresses in the specimen. Under repeated uniaxial loadings, the acoustoelastic birefringence was found to be a linear function of plastic strains at various states of total unloading. In elastoplastic bendings, the acoustoelastic birefringes are dependent on the natural anisotropy, plastic strains, and residual stresses as predicted by the theory of Part I. The uniaxial residual stress and plastic strain in the beam are determined by acoustoelastic experiments.
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Liu, Y., e N. J. Shen. "The residual stress and strain solutions of autofrettaged pressure vessels with a cone and cylinder connection". Journal of Strain Analysis for Engineering Design 27, n. 1 (1 gennaio 1992): 7–14. http://dx.doi.org/10.1243/03093247v271007.
Testo completoAbstract (sommario):
This paper presents analysis and experimental research on an autofrettaged pressure vessel with a cone and cylinder connection. Non-linear loading stresses and strains and the unloading residual stresses and strains are considered. The residual stress and strain fields are obtained by the non-linear axisymmetric boundary element method (BEM). The results of the BEM are verified by means of the finite element method (FEM) program ADINA and compared with autofrettaged high pressure experiments. It is concluded that the calculated residual strains are in reasonable agreement with those determined experimentally.
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Li, Zhao, Wei Ke, Mingyao Liu e Yang Zhou. "Reduction of Thermal Residual Strain in a Metal-CFRP-Metal Hybrid Tube Using an Axial Preload Tool Monitored through Optical Fiber Sensors". Polymers 14, n. 20 (17 ottobre 2022): 4368. http://dx.doi.org/10.3390/polym14204368.
Testo completoAbstract (sommario):
Thermal residual strains/stresses cause several defects in hybrid structures and various studies have reported the reduction of residual strain. This paper describes a method for reducing thermal residual strains/stresses in metal-CFRP-metal hybrid tubes (MCMHT). The proposed axial preload tool provides two ways to reduce the thermal residual strains/stresses during the co-cure bonding process: pre-compressing of the metal layers and pre-stretching of the unidirectional carbon fiber reinforced polymer (CFRP) layers. An online measurement technique with embedded optical fiber Bragg grating (FBG) sensors is presented. Thermal residual strains are evaluated based on classical lamination theory with the assumption of plane stress. The theoretical calculations and measurement results agree well. Furthermore, the dynamic characteristics of the MCMHTs are tested. The results show that the reduction of residual strain increases the natural frequency of the MCMHT, but is detrimental to the damping capability of the MCMHT, which imply that the intrinsic properties of the metal-composite hybrid structure can be modified by the proposed axial preload tool.
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Kubík, Ľubomír, Viera Kažimírová e Monika Božiková. "Compressive Loading of Apple Cultivar Golden Delicious". Acta Technologica Agriculturae 25, n. 3 (12 agosto 2022): 144–49. http://dx.doi.org/10.2478/ata-2022-0022.
Testo completoAbstract (sommario):
Abstract The study dealt with the experimental and numerical assessment of the apple cultivar Golden Delicious (Malus domestica L.) at compressive loading in lateral direction. The development of fruit hemisphere behaviour was examined between two parallel plates. Apple samples were subjected to tests at different strain rates. The experiments were conducted at eleven velocities from 10 to 350 mm·min−1 for the purposes of achieving different strain rates. Compression tests of the fruits at different strain rates corresponded to the quasi-state loading. Impacts of loading rate and strain rate on force and stress at compression were studied. The material exhibited nonlinear behaviour of dependency of stresses on strains, but linear viscoelastic behaviour of dependency of stresses on strain rate. The application possibilities of Kelvin-Voight viscoelastic model were evaluated. Forces, strains, stresses and the apparent moduli of elasticity were evaluated for the detection of fruit damage at different strain rates.
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Xie, Jian Feng. "Finite Element Analysis on Stress and Strain of Protected Fiber Bragg Grating". Advanced Materials Research 148-149 (ottobre 2010): 1639–42. http://dx.doi.org/10.4028/www.scientific.net/amr.148-149.1639.
Testo completoAbstract (sommario):
The stresses and strains on the protected FBG and protected layer under varied temperature were analyzed in theory. In order to verify the theoretical analysis of stress and strain,a finite element analysis software(ANSYS) was used to simulate the stresses and strains on the protected FBG and protected layer. Both simulation and theoretical analysis are show that the strain and stress on protected layer in r direction decreases with the increasing of radius(r), while the strain and stress in direction increases with the increasing of radius(r) . The results of theoretical analysis matches the ones form simulations well.
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Chen, Junfu, Zhiping Guan, Pinkui Ma, Zhigang Li e Xiangrui Meng. "The improvement of stress correction in post-necking tension of cylindrical specimen". Journal of Strain Analysis for Engineering Design 54, n. 3 (aprile 2019): 209–22. http://dx.doi.org/10.1177/0309324719852875.
Testo completoAbstract (sommario):
In post-necking tension of cylindrical specimen, the stress corrections based on the current analytical models have relatively significant errors at large strains. In this study, the prediction capability of these models involving Bridgman model, Siebel model and Chen model is evaluated by performing a series of finite element simulations of uniaxial tension of cylindrical specimen with different hardening exponents varied from 0.05 to 0.3. Numerical analysis of stress and strain distributions on the necking cross section indicates that the considerable errors of the corrected stresses corresponding to large strains might be mainly attributed to the assumption of uniform strain distribution on the necking cross section in these analytical models. The modification strategies of these models are presented in order to improve their prediction accuracy of post-necking stresses, taking geometrical configuration of neck and material properties into consideration. Accordingly, the modification formulas are proposed based on simulation results, involving the radius of cross section of neck and the hardening exponent. Finally, these formulas are used to correct the stresses in the post-necking tension of Q345 cylindrical specimen, which are compared with the stresses identified through inverse method. The results indicate that the modified models significantly improve the prediction accuracy of post-necking stresses at large strains.
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Ilchuk, Nazar, Philippe Spätig, Vadim Davydov e Steven van Petegem. "Measurement of Residual Stresses around the Notch of Tensile Specimens of the High-Cr Tempered Martensitic Steel F82H-Mod". Key Engineering Materials 592-593 (novembre 2013): 295–98. http://dx.doi.org/10.4028/www.scientific.net/kem.592-593.295.
Testo completoAbstract (sommario):
Residual elastic strains were measured by neutron diffraction using POLDI materials science diffractometer at PSI-Switzerland on pre-loaded notched flat tensile specimens made of the high-chromium tempered martensitic steel F82H-mod steel. To calculate the residual stresses using Hooke's equation, three perpendicular components of the residual strain field were determined. The measured residual strains and stresses were compared with those deduced from finite element simulation calculations. A very good agreement was found for the strains in the loading plane of the specimen while a somewhat larger discrepancy was observed for the out-of-plane residual strain, which was tentatively attributed to an uncertainty in the initial lattice spacing in that direction.
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Lorentzen, T., T. Faurholdt, B. Clausen e J. Danckert. "Characterization of residual stresses generated during inhomogeneous plastic deformation". Journal of Strain Analysis for Engineering Design 33, n. 3 (1 aprile 1998): 243–52. http://dx.doi.org/10.1243/0309324981512968.
Testo completoAbstract (sommario):
Residual stresses generated by macroscopic inhomogeneous plastic deformation are predicted by an explicit finite element (FE) technique. The numerical predictions are evaluated by characterizing the residual elastic strains by neutron diffraction using two different ( hkl) reflections. Intergranular residual elastic strains between subsets of grains are predicted numerically and verified by neutron diffraction. Subsequently, the measured residual strain profiles in the test samples are modified by the intergranular strains and compared to the engineering predictions of the FE technique. Results compare well and verify the capability of the numerical technique as well as the possibilities of experimental validation using neutron diffraction. The presented experimental and numerical approach will subsequently be utilized for the evaluation of more complicated plastic deformation processes resembling forming operations.
50
Xie, Jian Feng. "Finite Element Analysis on Stress and Strain of Embedded Fiber Bragg Grating". Advanced Materials Research 148-149 (ottobre 2010): 1634–38. http://dx.doi.org/10.4028/www.scientific.net/amr.148-149.1634.
Testo completoAbstract (sommario):
After FBG was protected and embedded into cement mortar, the stresses and strains on the FBG ,protected layer and cement mortar under varied temperature were analyzed in theory. In order to verify the theoretical analysis of stress and strain,a finite element analysis software(ANSYS)was used to simulate the stresses and strains on the FBG ,protected layer and cement mortar. The results of theoretical analysis matches the ones form simulations well.