Academic literature on the topic 'Axial stress-strain curve'
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Journal articles on the topic "Axial stress-strain curve"
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Huo, Hong Yuan, Chen Jie Cao, Li Sun, Li Sha Song, and Tong Xing. "Experimental Study on Full Stress-Strain Curve of SFRC in Axial Tension." Applied Mechanics and Materials 238 (November 2012): 41–45. http://dx.doi.org/10.4028/www.scientific.net/amm.238.41.
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The tests were carried out to study the effects of the fraction of steel fiber by volume and the thickness of cement paste wrapping steel fibers on the axial tensile properties of steel fiber reinforced concrete (SFRC). The strength grade of SFRC was CF40 with the fraction of steel fiber by volume varying from 0.5% to 2.0%, and the thickness of cement paste wrapping steel fibers varying from 0.8mm to 1.2mm. The tests were conducted by WAW-600 electric-hydraulic servo-type test machine. The results show that the axial tensile properties such as the axial tensile strength, the fullness of stress-strain curve, the tensile energy and the axial tensile toughness ratio are all improved obviously by the adding of steel fiber in concrete. The reasonable thickness of cement paste wrapping steel fibers is 1.0mm. The formulas for stress-strain relationship of SFRC in axial tension are proposed.
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Sun, Lin Zhu, Tie Cheng Wang, and Fang Yang. "Stress-Strain Model for Confined Concrete in Cross-Shaped Columns." Advanced Materials Research 450-451 (January 2012): 822–26. http://dx.doi.org/10.4028/www.scientific.net/amr.450-451.822.
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To establish complete stress-strain curve equations for confined concrete in cross-shaped columns, we designed 7 test specimens corresponding to the usable eigenvalue range of stirrup of the cross-shaped columns. We obtained the test results of the reinforced concrete cross-shaped columns through axial compression test, got the system parameters of a stress-strain model through statistical analysis of the test data, and then established stress-strain curves for confined concrete in the cross-shaped columns. This model reflects the variation rule of the stress-strain curve of confined concrete in cross-shaped columns. Compared with the stress-strain model for confined concrete in square columns, the confined concrete in cross-shaped columns has smaller peak stress, larger peak strain, and relatively steeper descending part of curve. The research results provide theorotical basis for nonlinear analysis of cross-shaped columns.
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Sun, Ming Quan, and Shi Feng Yang. "The Study of Cemented Sand and Gravel Constitutive Model." Advanced Materials Research 243-249 (May 2011): 4596–601. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.4596.
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Basing on triaxial experiments, the paper conducts the research to Cemented Sand and Gravel constitutive model. Using virtual rigid spring method, the Cemented Sand and Gravel constitutive model with considering the softening characteristics of material is established, and parameters needed are determined, the model establishes the foundation of non-linear analysis of Cemented Sand and Gravel structure. Mechanical properties and constitutive model study of Cemented Sand and Gravel is key to Cemented Sand and Gravel faced eath-rockfill dam. Basing the Mechanical properties triaxial experiment of the material, the paper gives further discussion on the constitutive model of Cemented Sand and Gravel. From the results of the triaxial test, when the cemented material content is smaller than 20kg/m3, the stress strain curve agrees quite well with hyperbolic law to which the normal gravel test curve also obeys, the exception is the increase of shearing strength. If the cemented material content is more than 30kg/m3, there is a peak value on the stress strain curve, the curve (before peak value) shows that axial strain increase with deviatoric stress with the increment gradually changing slowly, i.e. the stress strain curve has obvious nonlinear feature. the curve peaks value at the axial strain =2％, the stress strain curve present softening pattern that deviatoric stress decreases with the strain increase if continuous applying axial load. When axial strain lies between 2% and 6%, the shearing strength of samples decreases rapidly, after this interval, the shear strength tends to the stable value in the final. It is core problem the paper try to solve that how to describe Cemented Sand and Gravel constitutive model.
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Lade, Poul V., and Hamid Karimpour. "Stress relaxation behavior in Virginia Beach sand." Canadian Geotechnical Journal 52, no. 7 (July 2015): 813–35. http://dx.doi.org/10.1139/cgj-2013-0463.
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Effects of strain rate on the stress–strain and subsequent stress relaxation behaviors have been studied by performing triaxial compression tests on dense Virginia Beach sand specimens at three different strain rates (ratio of 256 between the slowest and the fastest) under low and high confining pressures. For the tests performed under low confining pressure, the specimens that were initially sheared at a faster rate showed a slightly higher amount of stress relaxation, but almost identical stress–strain behaviors were achieved. For tests performed under high confining pressure, the same amount of strength was achieved at high axial strains (10% to 20%), but specimens sheared at higher strain rates showed a slightly stiffer stress–strain response at low axial strains (up to 10%). Similar to the tests performed under low confining pressure, higher strain rates produced higher amounts of stress relaxation to some extent. Effects of correction of axial strain due to load cell expansion and drainage condition during stress relaxation have also been studied and the results indicated that correction of axial strain and undrained condition will both increase the observed amount of stress relaxation. Moreover, a 1 day stress relaxation curve was obtained by connecting the ending stress–strain points of six stress relaxation tests initiated at different deviator stress levels, and this curve was found to be different from the 1 day creep curve obtained from a previous study. A long-term stress relaxation test was also performed, and it showed linear reduction of deviator stress with the logarithm of time during stress relaxation. Observations made are all aligned with the phenomenon of static fatigue and the proposed mechanism for time effects in granular materials.
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Zhang, Fu Jun, and Chuan Xiao Liu. "Experimental Study of Short-Term Creep Characteristics Base on Step Loading-Unloading Method for Hard Rock." Advanced Materials Research 774-776 (September 2013): 86–93. http://dx.doi.org/10.4028/www.scientific.net/amr.774-776.86.
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Based on experimental results of uniaxial compression and short-term creep using 8-step loading-unloading method, fine sandstone specimen, which lower creep limit is 27MPa, present typical brittle breakage properties of hard rock. The correlative coefficients of linear regression function for isochronous stress-strain curve are all higher than 0. 92, and the ratio of long-term strength to instantaneous strength reaches 94. 39%，which indicate that the whole creep of fine sandstone specimen is weak. The average correlative coefficients of linear regression function for isochronous stress- axial strain curve are 3. 92% higher than that of average correlative coefficients of linear regression function for isochronous stress- radial strain curve, so nonlinear creep property of the fine sandstone specimen in axial direction is correspondingly weaker than that in radial direction. Negative Gauss distribution can be applied collectively to nonlinear creep of fine sandstone specimen, which has obvious time effect.With increasing loading, the reduction degrees of average correlative coefficients of linear fitting functions of isochronous stress-axial strain curve and isochronous stress-radial strain curve are 0. 97% and 0. 67% respectively, which indicates the linear correlation decreases commonly. Thus, the degree of nonlinear creep for fine sandstone specimen increases along with loading stress with obvious stress effect.
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Wellekens, J. B., Wim De Waele, Rudi Denys, Stijn Hertele, and Matthias Verstraete. "Interpretation of stress-strain curve in pipeline research." International Journal Sustainable Construction & Design 1, no. 1 (November 6, 2010): 40–45. http://dx.doi.org/10.21825/scad.v1i1.20393.
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For the design of on-shore pipelines installed in areas that are susceptible to ground movements and offshore pipelines, axial stresses above yield must be considered. In such so-called strain-based design,knowledge of the stress-strain behaviour of the pipeline steel and girth welds is highly important. These behaviours are influenced by many factors, including: welding parameters, operation temperature, tensile test specimen geometry and orientation, and microstructure of the steel. This paper focuses on the influence of the tensile test specimen geometry and orientation, for the case of UOE formed pipes. As regards the geometry, it is concluded that the stress-strain diagram is most representative for a flat fullthickness test specimen. As regards the orientation, the yield stress is higher for transversal test specimens, as compared to longitudinally oriented test specimens.
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He, Xing, Junfeng Chen, Wei Tian, Yuebing Li, and Weiya Jin. "Low Cycle Fatigue Behavior of Steam Generator Tubes under Axial Loading." Materials 11, no. 10 (October 11, 2018): 1944. http://dx.doi.org/10.3390/ma11101944.
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Compared with the fatigue properties of the material (Inconel Alloy 690), the real fatigue lives of tubes are more meaningful in the fatigue design and assessment of steam generator (SG) tube bundles. However, it is almost impossible to get a satisfactory result by conducting fatigue tests on the tube directly. A tube with a uniform and thin wall easily fails near the clamping ends under cyclic loading due to the stress concentration. In this research, a set-up for fatigue tests of real tubes is proposed to overcome the stress concentration. With the set-up, low cycle fatigue tests were conducted in accordance with an existing fatigue design curve for Alloy 690. Strain control mode was applied with fully reversed push–pull loading under different strain amplitudes (0.15%, 0.2%, 0.3%, and 0.4%). A favourable result was obtained, and the low cycle fatigue behavior was investigated. The results showed that the fatigue life tested by the real tube was below the strain–life curve of Alloy 690 which was fitted by conventional solid specimens. A cyclic hardening behavior was found by the cyclic stress–strain curve when compared with the monotonic stress–strain curve.
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Li, Gang, Zhen Yan, Jinli Zhang, Jia Liu, and Yu Xi. "Test Study on the Creep Behaviors of Tianjin Clays." E3S Web of Conferences 136 (2019): 07029. http://dx.doi.org/10.1051/e3sconf/201913607029.
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The drained triaxial creep tests were carriedout to investigate the relationshipsbetween axial strain and time, axial strain and deviatoricstress, and axial strain rate and time for the undisturbed samples of muddy clay and clay in Tianjin.Based on the creep test results, the Singh-Mitchell modelwas used for creep calculation. The results showed that the muddyclay and clay exhibited typical non-linear creep properties. The axial strain increasedwith time and then gradually tendedto be stable.The strain rate increasedasthe deviatoric stress increased, and the muddy clay and clay showedthe characteristics of attenuation creep under deviatoricstresses. The axial strain of muddy clay wassignificantly larger than that of clay, and reachedthestable state within 3000 minutes.Under low deviatoricstress, the slope of the isochronal curve was smaller; while under high deviatoric stress, the slope of the isochronal curve waslarger.The test results were in good agreement with the calculation results, which indicated that the Singh-Mitchell model wassuitable for describing the creep behaviorsof the undisturbed claysin Tianjin.
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Wang, X. B. "Temperature-Dependent Shear Strain Localization of Aluminium-Lithium Alloy in Uniaxial Compression Using Zerilli-Armstrong and Gradient Plasticity Models." Materials Science Forum 519-521 (July 2006): 789–94. http://dx.doi.org/10.4028/www.scientific.net/msf.519-521.789.
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Gradient-dependent plasticity where a characteristic length is involved to consider the microstructural effect (interactions and interplaying among microstructures due to the heterogeneous texture) is introduced into Zerilli-Armstrong model based on the framework of thermally activated dislocation motion. Effect of initial temperature on the distributions of plastic shear strain and deformation in adiabatic shear band (ASB), the axial compressive stress-axial compressive strain curve, the shear stress-average plastic shear strain in ASB curve and the plastic shear strain corresponding to the occurrence of shear strain localization is investigated. The axial deformation within aluminum-lithium alloy specimen in uniaxial compression in strain-hardening stage is considered to be uniform. Beyond the peak compressive stress, a single ASB with a certain thickness determined by internal length is formed and intersects the specimen. The axial plastic deformation is decomposed into uniform deformation and localized deformation due to the shear slip along ASB. Lower temperature leads to earlier occurrence of shear strain localization, i.e., lower critical plastic compressive strain, steeper post-peak shear stress-average plastic shear strain in ASB curve, higher peak shear stress and more apparent shear strain localization. The calculated distributions of plastic shear strain and deformation in ASB are highly nonuniform due to the microstructural effect, as cannot be predicted by classical elastoplastic theory applicable to completely homogenous material. The predicted average plastic shear strains in ASB for different widths of ASB agree with the measured values for under-aged Al-Li alloy at 298K and at strain rate of approximately 103s-1.
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Yang, Gang, Qing Yang, and Wen Hua Liu. "Study of Variation of Soil Stress State Based on the Curve of Normalized Strain- Pore Water Pressure." Applied Mechanics and Materials 275-277 (January 2013): 295–98. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.295.
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The cyclic behavior of normally consolidated silty clays was investigated by conducting a series of cyclic simple shear tests on one-dimensionally and isotropically consolidated reconstituted samples. The critical cyclic stress ratio was obtained by the normalized axial strain. Based on hysteretic curve of pore water pressure versus strain, dynamic characteristics of silty clay were investigated. The results showed that with increasing of cyclic loading, soil stress state can be divided into steady state, critical state and failure state based on the critical cyclic stress ratio. The hysteresis curve of pore water pressure versus strain was divided into two parts by cross point A. Compared with two parts, the variation law was obtained. When the upper part area was bigger than the lower part area, pore water pressure and axial strain continuously increase with cycle number; when the upper part area was smaller than the lower part area, pore water pressure and axial strain tended to be steady with cycle number.
Dissertations / Theses on the topic "Axial stress-strain curve"
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Erdil, Baris. "Behavior Of Cfrp Confined Concrete Specimens Under Temperature Cycles And Sustained Loads." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614137/index.pdf.
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The application of carbon fiber reinforced polymers (CFRP) is one of the effective retrofitting and strengthening methods that is used worldwide and is starting to be used in Turkey as well because they have high strength and high modulus in the fiber direction, have very low coefficient of thermal expansion when compared to concrete and steel and are known not to corrode. Since FRPs are lightweight, their mass can be neglected when compared to concrete and steel.
However, before proposing this material as an alternative for strengthening and retrofitting applications their long-term behavior should be understood because they are applied on to concrete by several layers of epoxy-based adhesives, which can be affected by change in humidity, temperature and load. Therefore, behavior of CFRP-strengthened structures in varying temperature and humidity conditions must be investigated.
In this dissertation, behavior of CFRP confined cylindrical and prismatic concrete specimens having square cross-section were investigated under sustained compressive loads, dry and wet heating-cooling cycles, and outdoor exposures under direct sunlight, to determine the possible changes in their mechanical properties. Sustained loads were applied as the 40% and 50% of their confined axial load capacity. In addition to the sustained loads, specimens were subjected to 200 heating-cooling cycles between -10°C to 50°
C. In order to understand the change in behavior of CFRP confined concrete specimens better, they were divided in six groups. A single effect was investigated in each group. After aging tests mechanical properties of the specimens were recorded via monotonic uniaxial loading. It was observed that temperature cycles had little effect on behavior but sustained loads changed the shape of the axial stress-strain diagram and resulted in a dramatic decrease in ultimate strain. Based on the test results and also using the data of similar studies available in the literature, strength and strain models considering the exposures as independent parameters were established and finally axial stress-strain curve was tried to be predicted.
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Jakel, Roland. "Grundlagen der Elasto-Plastizität in Creo Simulate - Theorie und Anwendung." Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-87141.
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Der Vortrag beschreibt die Grundlagen der Elasto-Plastizität sowie die softwaretechnische Anwendung mit dem FEM-Programm Creo Simulate bzw. Pro/MECHANICA von PTC. Der erste Teil des Vortrages beschreibt die Charakteristika plastischen Verhaltens, unterschiedliche plastische Materialgesetze, Fließkriterien bei mehrachsiger Beanspruchung und unterschiedliche Verfestigungsmodelle. Im zweiten Vortragsteil werden Möglichkeiten und Grenzen der Berechnung elasto-plastischer Probleme mit der Software dargestellt sowie Anwendungstipps gegeben. Im dritten Vortragsteil schließlich werden verschiedene Beispiele vorgestellt, davon besonders ausführlich das Verhalten einer einachsigen elasto-plastischen Zugprobe vor und nach dem Eintreten der EinschnürdehnungThis presentation describes the basics of elasto-plasticity and its application with the finite element software Creo Simulate (formerly Pro/MECHANICA) from PTC. The first part describes the characteristics of plastic behavior, different plastic material laws, yield criteria for multiaxial stress states and different hardening models. In the second part, the opportunities and limitations of analyzing elasto-plastic problems with the FEM-code are described and user information is provided. The last part finally presents different examples. Deeply treated is the behavior of a uniaxial tensile test specimen before and after elongation with necking appears
Book chapters on the topic "Axial stress-strain curve"
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Kobayashi, Shiro, Soo-Ik Oh, and Taylan Altan. "Plasticity and Viscoplasticity." In Metal Forming and the Finite-Element Method. Oxford University Press, 1989. http://dx.doi.org/10.1093/oso/9780195044027.003.0007.
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The theory of plasticity describes the mechanics of deformation in plastically deforming solids, and, as applied to metals and alloys, it is based on experimental studies of the relations between stresses and strains under simple loading conditions. The theory described here assumes the ideal plastic body for which the Bauschinger effect and size effects are neglected. The theory also is valid only at temperatures for which recovery, creep, and thermal phenomena can be neglected. The basic theory of classical plasticity is described by Hill, and also in References, in addition to the books listed in Chap. 1. A concise description of the general plasticity theory necessary for metal forming is given in the book by Johnson et al.. In this chapter, certain important aspects of the theory are presented in order to elucidate the developments of the finite-element solutions of metal-forming problems discussed in this book. First, various measures of stress and strain are introduced. Then, the governing equations for plastic deformation and principles that are the foundations for the analysis are described. The extension of the theory of plasticity to time-dependent theory of viscoplasticity is outlined in Section 4.8. Particular references are made, in Sections 4.3 through 4.7, to the books by Hill and by Johnson and Mellor, and to the section on general plasticity theory in the book by Johnson et al.. The basic quantities that may be used to describe the mechanics of deformation when a body deforms from one configuration to another under an external load are the stress, strain, and strain-rate. Various measures of these quantities are defined, depending upon how closely formulations represent actual situations. Although it is not possible to provide the complete mathematical formulations in one-dimensional deformation, these measures are introduced for the case of simple uniaxial tension. Consider the uniaxial tension test of a round specimen whose initial length is l0 and cross-sectional area is A0. The specimen is stretched in the axial direction by the force P to the length l and the cross-sectional area A at time t, as shown in Fig. 4.1. The response of the material is recorded as the load-displacement curve, and converted to the stress-strain curve as shown in the figure. The deformation is assumed to be homogeneous until necking begins.
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Wern, H., and A. Peiter. "COMPUTER CODE FOR TRI-AXIAL X-RAY STRAIN AND STRESS ANALYSIS USING FITTED CURVES." In Advances in Surface Treatments, 219–26. Elsevier, 1987. http://dx.doi.org/10.1016/b978-0-08-034923-7.50028-0.
Full textConference papers on the topic "Axial stress-strain curve"
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Dan, W. J., W. G. Zhang, S. H. Li, and Z. Q. Lin. "A Tensile Characterization Study of Metal Sheet in Large-Strain." In ASME 2006 International Manufacturing Science and Engineering Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/msec2006-21022.
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A method for determining the strain-stress curve of larger-strain is proposed when plastic instability occurs in standard tension tests. Thin tested steel sheet is subjected to tension loading until fracture occurs. The deformation process is captured with a digital camera. Displacement and strain field of material deformation can be calculated by a mesh-free PIM method. A tensile experiment is simulated to verify that local measuring stress-strain curve by PIM method near the center of the specimen can describe a full stress-strain curve clearly. Numerical simulation results, at different location along the specimen axial, present that different parts of specimen have different deformation distribution in tensile and the center fracture part of tensile specimen is the only region which can experience full strain. The true stress- true strain curves, based on the estimated parameters, are validated in all strain regions by comparison with curves from standard tension tests. The measured curves by PIM method are very stabilization. Compared with several material constitutive equations, The Swift’s equation is very close to experiment curve at plastic deformation.
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Mei, Hongyuan, Deyu Wang, and Qi Wan. "Numerical and Experimental Study on Ultimate Strength of Stiffened Column Under Axial Compression." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18340.
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Abstract Six specimens with one Tee-bar stiffener and its attached plating were tested under axial compression to investigate the ultimate strength. The specimens have one longitudinal span and the simply supported boundary conditions at the end edge of loading were produced based on a horizontal test fixture. The initial geometrical imperfections were measured and tensile tests of high tensile steel used in the specimens with different thickness were conducted. The results calculated by FE analysis with true stress-strain curves, average measured thickness and measured initial geometrical deformation could reach a good agreement with experimental results. The ultimate strength calculated with elastic/perfectly plastic curve is approximately 10% larger than that with true stress-strain curve. The reason is that the proportional limit stress of material is significantly lower than 0.2% proof stress for the high strength steel used in specimens. And the occurrence of buckling is earlier than the time that the material enters into plastic stage. As a result, the ultimate strength assessed with elastic/perfectly plastic curve doesn’t always the lowest result and it should be adopted carefully.
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Wei, Zhigang, Pingsha Dong, Romesh C. Batra, and Kamran Nikbin. "Analysis of Multi-Axial Fatigue Test Data Using a Path-Dependent Effective Stress/Strain Definition." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97630.
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Multi-axial fatigue life assessment is important in power generation, aerospace, automotive, and many other industries. The newly developed path-dependent multi-axial cycle counting and fatigue life assessment method has been shown effective for some applications. For instance, when stress range is used as the only driving force for fatigue failure, the method correlates high cycle fatigue test data well. The method consists of two parts: (1) maximum-range (or maximum distance) based cycle counting method, so that the method can be applied to 2-D and 3-D stress or strain space, as compared to the conventional rainflow counting method, which is based on the peak-valley concept, therefore, can be applied only to uniaxial (1-D) loadings; and (2) a path-length based stress range is used as the fatigue damage parameter replacing the traditional concept of stress or strain range, which is the difference between the peak value and the valley value of a cycle. This method has been justified using the classical fracture mechanics in multidimensional stress space. In this paper, we apply the method to analyze two additional classes of multi-axial fatigue test data reported in the literature: (1) low-cycle strain based tests, which has an important implications in high-temperature applications, such as piping/vessels in power industry, turbine, and automotive exhaust systems; (2) a series of test data that require an introduction of two parameters in either fatigue crack growth model or S-N curve based approach. For the latter, an incremental crack growth model reported earlier by the authors is recast to incorporate one additional stress based parameter to account either mean stress or maximum principle stress effects in multi-axial fatigue damage process, dependent upon material characteristics under consideration. The results show that strain-based low-cycle multi-axial fatigue data can be effectively correlated in the form of a single S-N curve using a path-dependent effective strain range definition. Furthermore, a two parameter based interpretation of the crack propagation model is capable of capturing effects of the maximum principle and mean stresses on multi-axial fatigue damage process associated with some of the test data. Finally, the physical basis of the method in these extended applications is discussed.
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Jha, Deepak K., and Anuradha Banerjee. "Cohesive Model in Prediction of Multi-Axial Fatigue." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-40353.
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A fatigue failure model for life assessment of a structure that incorporates the stress-state dependence and irreversible nature of fatigue damage is presented. In the frame work of cohesive zone model, a stress state dependent traction separation law for plane strain is taken to represent an undamaged ferritic steel. The evolution of damage has two additional fatigue parameters: a stress and a length parameter. Initially a parametric study is done to show that the model is able to reproduce a typical uniaxial fatigue response to stress based cyclic load, that of a stress-life curve and reduction in life due to positive mean stress. The effect of the cohesive fatigue parameters on the characteristics of the stress-life curve is then established. The model is further applied for a range of sinusoidally varying in-phase stress states which are characterised by a fixed bi-axiality ratio. The initiation and growth of damage is shown to be more rapid for higher bi-axiality. Except for stress amplitudes in which the lower bi-axiality case has conditions close to monotonic failure, the effect of bi-axiality is shown to be detrimental to the life expectancy of the material as observed in available experimental literature.
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Nadarajah, Chithranjan, Benjamin F. Hantz, and Sujay Krishnamurthy. "Using Isochronous Method to Calculate Creep Damage: Part 1." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65211.
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This paper is Part 1 of two papers illustrating how isochronous curves can be used to determine creep stress and damage. In Part 1 of the paper two simple examples of two bars under axial load and a beam in pure bending are illustrated using a closed form solution to determine the creep stress and damage from an isochronous stress strain curves. For the two examples, the Omega material model was used for generating the isochronous stress strain curve and for computing the creep damage. The closed from solutions are compared with finite element analysis using isochronous stress strain curves as well as time explicit Omega creep model. The results from all the three analysis are found to be in good agreement.
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Tan, Kok Ee, and John H. L. Pang. "Strain-Rate Effects on Constitutive Behavior of Sn3.8-Ag0.7-Cu Lead-Free Solder." In ASME 2009 InterPACK Conference collocated with the ASME 2009 Summer Heat Transfer Conference and the ASME 2009 3rd International Conference on Energy Sustainability. ASMEDC, 2009. http://dx.doi.org/10.1115/interpack2009-89278.
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In this paper, the strain-rate dependent mechanical properties and stress-strain curve behavior of Sn3.8Ag0.7Cu (SAC387) solder is presented for a range of strain-rates at room temperature. The apparent elastic modulus, yield stress properties and stress-strain curve equation of the solder material is needed to facilitate finite element modeling work. Tensile tests on dog-bone shaped bulk solder specimens were conducted using a non-contact video extensometer system. Constant strain-rate uni-axial tensile tests were conducted over the strain-rates of 0.001, 0.01, 0.1 and 1 (s−1) at 25°C. The effects of strain-rate on the stress-strain behavior for lead-free Sn3.8Ag0.7Cu solder are presented. The tensile yield stress results were compared to equivalent yield stress values derived from nano-indentation hardness test results. Constitutive models based on the Ramberg-Osgood model and the Cowper-Symond model were fitted for the tensile test results to describe the elastic-plastic behavior of solder deformation behavior.
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Cosham, Andrew, Kenneth A. Macdonald, Ian MacRae, and Malcolm Carr. "ECAs and Lateral Buckling." In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95529.
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Abstract An engineering critical assessment (ECA) is commonly conducted during the design of an offshore pipeline in order to determine the tolerable size of flaws in the girth welds. API 579-1/ASME FFS-1 2016 and BS 7910:2013+A1:2015 Incorporating Corrigenda Nos. 1 and 2 give guidance on conducting fitness-for-service assessments of cracks and crack-like flaws. DNVGL-RP-F108, 2017 Assessment of flaws in pipeline and riser girth welds describes a methodology to satisfy the fracture and fatigue limit states in DNVGL-ST-F101, 2017 based on Option 2 with ductile tearing in BS 7910:2013. It requires that the stress-strain curve used in a strain-based fracture mechanics analysis should represent a high yield strength combined with low strain-hardening properties (a characteristic high stress-strain curve with low strain hardening), and that used in a stress-based fracture mechanics assessment should represent a low yield strength. A pipeline operating at high temperatures and/or high pressures is subject to high compressive axial forces. The pipeline might then relieve these forces by buckling. A design that incorporates controlled lateral buckling is an efficient solution to the problem of high compressive axial stresses. Lateral buckling does, however, give rise to relatively high tensile axial strains (possibly exceeding 0.4 percent) in the pipe wall, and, relatively high fatigue loading associated with movement of the buckle under start-up and shut-down cycles. The calculated tensile axial strain in the pipe wall in a lateral buckle depends on the assumed stress-strain curve. It tends to be higher if a low yield strength combined with low strain-hardening properties is assumed. There is then an apparent inconsistency between the two sets of assumptions. A deterministic assessment of a circumferentially-orientated, internal surface crack-like flaw in a girth weld in a lateral buckle is used to investigate the significance of this apparent inconsistency.
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Cosham, Andrew, and Kenneth A. Macdonald. "ECAs, FE and Bi-Axial Loading: A Critique of DNV-OS-F101, Appendix A." In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41422.
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Controlled lateral buckling in offshore pipelines typically gives rise to the combination of internal over-pressure and high longitudinal strains (possibly exceeding 0.4 percent). Engineering critical assessments (ECAs) are commonly conducted during design to determine tolerable sizes for girth weld flaws. ECAs are primarily conducted in accordance with BS 7910, often supplemented by guidance given in DNV-OS-F101 and DNV-FP-F108. DNV-OS-F101 requires that finite element (FE) analysis is conducted when, in the presence of internal over-pressure, the nominal longitudinal strain exceeds 0.4 percent. It recommends a crack driving force assessment, rather than one based on the failure assessment diagram. FE analysis is complicated, time consuming and costly. ECAs are, necessarily, conducted towards the end of the design process, at which point the design loads have been defined, the welding procedures qualified and the material properties quantified. In this context, ECAs and FE are not an ideal combination for the pipeline operator, the designer or the installation contractor. A pipeline subject to internal over-pressure is in a state of bi-axial loading. The combination of internal over-pressure and longitudinal strain appears to become more complicated as the longitudinal strain increases, because of the effect of bi-axial loading on the stress-strain response. An analysis of a relatively simple case, a fully-circumferential, external crack in a cylinder subject to internal over-pressure and longitudinal strain, is presented in order to illustrate the issues with the assessment. Finite element analysis, with and without internal over-pressure, are used to determine the plastic limit load, the crack driving force, and the Option 3 failure assessment curve. The results of the assessment are then compared with an assessment using the Option 2 curve. It is shown that an assessment based Option 2, which does not require FE analysis, can potentially give comparable results to the more detailed assessments, when more accurate stress intensity factor and reference stress (plastic limit load) solutions are used. Finally, the results of the illustrative analysis are used to present an outline of suggested revisions to the guidance in DNV-OS-F101, to reduce the need for FE analysis.
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Scott-Emuakpor, Onome, M. H. Herman Shen, Tommy George, and Charles Cross. "An Energy-Based Method for Multi-Axial Fatigue Life Calculation." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27425.
Full textAbstract:
An accelerated method for determining the material strength of Aluminum 6061-T6 has been developed for prediction of fully-reversed shear and biaxial fatigue life. The framework for this accelerated method is developed in accordance with a previously developed uniaxial energy-based prediction approach, which states: the total strain energy dissipated during a monotonic fracture and a cyclic process is the same material property, where each can be determined by measuring the area underneath the monotonic true stress-strain curve and the area within a hysteresis loop, respectively [1]. The developed framework consists of the following two elements: (1) The development of a life prediction and estimation implementation scheme for calculating effective shear fatigue life cycles, and (2) the development of a constitutive law for multi-axial fatigue life prediction based on analytical comparison with biaxial fatigue experimental data. A comparison between these two framework elements and experimental results for Al 6061-T6 has been conducted to show that there is good agreement, thus validating the prediction method and the developed procedures of the entire framework.
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Karpanan, Kumarswamy, and William Thomas. "Influence of Lode Angle on the ASME Local Strain Failure Criterion." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63067.
Full textAbstract:
Failure strain at any point on a structure is not a constant but is a function of several factors, such as stress state, strain rate, and temperature. Failure strain predicted from the uniaxial tensile testing cannot be applied to the bi-axial or tri-axial stress state. ASME Sec VIII-Div-2, and −3 codes give methods to predict the failure strain for multi-axial stress state by considering the triaxiality factor, which is defined as the ratio of mean stress to the equivalent stress. Failure strain predicted by the ASME method (based on the Rice-Tracey ductile failure model) is an exponential curve that relates the failure strain to the triaxiality factor. The ASME VIII-3 method also gives procedures to calculate failure strain for various material types: ferritic, stainless steel, nickel alloy, aluminum, etc. Experimental results of failure strain at various stress states show that the failure strain is not only a function of the triaxiality factor, but also a function of the Lode angle. The Lode angle takes on the value of 1, 0, and −1 for tension, pure shear, and compression stress state, respectively. Experimental data shows that the failure strain is a 3D surface which has an exponential relation with triaxiality and a parabolic relation with the Lode angle. To validate the ASME failure strain prediction, this paper compares experimental failure strain test data from literature with the ASME predictions. The ASME predictions are non-conservative especially for moderately ductile materials such as aluminum and high strength carbon steel. A reduction factor on failure strain for low ductile material is presented using the relation between the R (yield/ultimate) and the stress ratio (shear/tensile stress). The ASME method does not account for the environmental effects while calculating the failure strain. High pressure, high temperature (HPHT) subsea components designed using ASME VIII-3 code are subjected to various environments in subsea, such as seawater, seawater with cathodic protection (CP) and production fluid (crude oil). Experimental data shows that the Elongation (EL) and/or Reduction in Area (RA) from tensile testing decrease in these environments. Therefore, to account for any environment effect on the failure strain, reduced EL and RA can be used to predict the failure strain.