Academic literature on the topic 'Stiffness under stresses'
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Journal articles on the topic "Stiffness under stresses"
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Philippidis, T. P., and A. P. Vassilopoulos. "Stiffness Reduction of Composite Laminates under Combined Cyclic Stresses." Advanced Composites Letters 10, no. 3 (May 2001): 096369350101000. http://dx.doi.org/10.1177/096369350101000302.
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Stiffness reduction due to fatigue of a [0/(±45)2/0]T Glass/Polyester (GRP) laminate under combined cyclic stress is investigated in this experimental study. Stress states combining all three components of in-plane stress tensor are induced by uniaxially testing specimens cut off-axis at various angles from the principal material coordinate system. Modulus reduction is related to the various failure modes exhibited under different states of combined stress. It is verified that shear and transverse normal stress induce more severe stiffness degradation compared to stress states where normal stress in the main fibre direction is dominant. For every loading condition and stress state, it is observed in general that stiffness decrease is more pronounced under lower stress levels than these inducing low cycle fatigue.
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Topkaya, Cem, and Özer Zeybek. "Application of ring beam stiffness criterion for discretely supported shells under global shear and bending." Advances in Structural Engineering 21, no. 16 (February 20, 2018): 2404–15. http://dx.doi.org/10.1177/1369433218758476.
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Silos in the form of a cylindrical metal shell are commonly elevated to provide access to the space beneath. In general, a few discrete column supports at evenly spaced intervals are commonly utilized. The presence of discrete supports results in circumferential non-uniformity in the axial compressive stress above the support. Depending on the size of the structure, several different support arrangements may be chosen. A stiff ring beam is utilized in larger silos to transfer and evenly distribute the discrete forces from the supports into the cylindrical shell wall. A stiffness criterion was developed by Rotter to assess the degree of non-uniformity in axial compressive stresses around the circumference. The stiffness criterion is based on the relative stiffnesses of the ring beam and the cylindrical shell and was verified for loading conditions that produce circumferentially uniform axial stresses around the circumference. A study has been undertaken to investigate the applicability of the stiffness criterion to cylindrical shells under global shear and bending. Pursuant to this goal, extensive finite element analyses were conducted where different ring beam and cylindrical shell combinations are subjected to global shearing and bending actions. The results revealed that the stiffness criterion can be extended to shells under this loading condition. The degree of non-uniformity in axial stresses is quantified and presented as simple formulas that can be readily adopted by design standards.
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Pervan, Nedim, Elmedin Mešić, Adis J. Muminović, Muamer Delić, Enis Muratović, Mirsad Trobradović, and Vahidin Hadžiabdić. "Biomechanical Performance Analysis of the Monolateral External Fixation Devices with Steel and Composite Material Frames under the Impact of Axial Load." Applied Sciences 12, no. 2 (January 12, 2022): 722. http://dx.doi.org/10.3390/app12020722.
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This paper describes comparative analysis of the biomechanical performances conducted on the external fixation devices whose frames are made out of two different material (stainless steel and composite material). Biomechanical properties were determined with experimental and FEM (finite element method) models which are used to study the movement of the fracture crack, establish stiffness of the design solutions and monitor generated stresses on the zones of interest. Geometric modeling of two fixation devices configurations B50 and C50 is used as a basis for structural analysis under the impact of axial load. Structural analysis results are confirmed with an experimental setup. Analyzed deflection values in the load and fracture zones are used to define the exact values of the stiffness for the construction design and fracture, respectively. The carbon frame device configuration has 28% lower construction stiffness than the one with the steel frame (for B50 configuration), i.e., 9% (for C50 configuration). In addition, fracture stiffness values for the composite frame application are approximately 23% lower (B50 configuration), i.e., 13% lower (C50 configuration), compared to steel frame. The carbon frame device has about 33% lower stresses at the critical zones compared to the steel frame at the control zone MM+ and, similarly, 35% lower stresses at the control zone MM-. With an exhausting analysis of the biomechanical properties of the fixation devices, it can be concluded that steel frame fixation device is superior, meaning it has better biomechanical characteristics compared to carbon frame fixation device, regarding obtained data for stresses and stiffnesses of the frame construction and fracture. Considering stresses at the critical zones of the fixation device construction, the carbon frame device has better biomechanical performances compared to steel frame devices.
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Hsu, Thomas T. C., and Mohamad Y. Mansour. "Stiffness, Ductility, and Energy Dissipation of RC Elements under Cyclic Shear." Earthquake Spectra 21, no. 4 (November 2005): 1093–112. http://dx.doi.org/10.1193/1.2044828.
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A new Cyclic Softened Membrane Model (CSMM) was recently developed to predict the stiffness, ductility, and energy dissipation of reinforced concrete (RC) elements subjected to reversed cyclic shear. Using the nonlinear finite element analysis, we can integrate these responses of elements to predict the behavior of a whole structure, such as a low-rise shear wall, subjected to earthquake action. This study of CSMM summarizes systematically the effects of the two primary variables: the steel bar angle with respect to the direction of the applied principal stresses and the steel percentage. The results clearly show that RC structures under cyclic shear stresses could be designed to be very ductile, have large stiffness, and possess high energy-dissipation capacities (just like flexural-dominated elements), if the steel bars are properly oriented in the directions of principal stresses and if the steel percentages are kept within certain limits.
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Terrell, Ronald G., Brady R. Cox, Kenneth H. Stokoe, John J. Allen, and Dwayne Lewis. "Field Evaluation of the Stiffness of Unbound Aggregate Base Layers in Inverted Flexible Pavements." Transportation Research Record: Journal of the Transportation Research Board 1837, no. 1 (January 2003): 50–60. http://dx.doi.org/10.3141/1837-06.
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Unbound aggregate base layers in a quarry haul road in Georgia were characterized using embedded sensors and in situ seismic testing. Two sections of the road were constructed as inverted pavements, one using a South African Roads Board method and the other using a conventional Georgia Department of Transportation method. A third was constructed using a traditional method. Miniaturized versions of traditional cross-hole and downhole seismic tests were conducted to determine the stiffnesses of each base layer. Horizontally propagating compression and shear waves were measured under four different loading conditions to determine Young’s moduli and Poisson’s ratios of the base. An increase in stiffness with an increase in load was measured. Additionally, it was found that the Georgia and South Africa sections had similar stiffnesses. Surprisingly, the traditional section was found to be somewhat stiffer than the other sections. This higher stiffness is thought to be caused by a prolonged period of compaction before construction of the unbound aggregate base layer, which essentially transforms the traditional section into an inverted pavement. Using the vertical total normal stresses computed from ILLI-PAVE, a value of 0.3 for the earth pressure coefficient was found to be reasonable for this material in determining the radial total normal stresses. The radial effective normal stresses were calculated from the radial total normal stresses and experimentally determined pore water pressures. Additionally, the negative pore water pressures in the partially saturated granular base had a significant impact on the stiffness of the unbound aggregate base layer, especially under small load levels.
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Shen, Jun Min, Yu Min Zhou, and Xiao Zhang. "Finite Element Analysis of Asphalt Overlays on Existing PCC Pavement under Heavy Traffic Loading." Advanced Materials Research 361-363 (October 2011): 1472–75. http://dx.doi.org/10.4028/www.scientific.net/amr.361-363.1472.
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This study models the thermal stresses and load stresses of Xia-Feng expressway asphalt overly on an existing PCC pavement by using finite element method. The sensitiveness of different influence factors on thermal stresses and load stresses are discussed. Research results show that asphalt overlay deflection and load stresses increase with the decreasing of weakening of subgrade strength index λk and when a soft interlayer with low level of spring stiffness is adopted, the thermal stress of asphalt overlay is quite small compared with load stresses.
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Tong, Li Li, Zhen Qing Wang, and Bao Hua Sun. "Numerical Simulation of Unidirectional Hoop Composite Laminates under Flexural Loads." Key Engineering Materials 334-335 (March 2007): 217–20. http://dx.doi.org/10.4028/www.scientific.net/kem.334-335.217.
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Numerical simulation for unidirectional hoop composite laminates under flexural loads was finished. The change of tensile and compressive stresses, the position of local crush and delamination and stiffness degradation were analyzed with parametric program compiled by APDL language in ANSYS. The results showed that composite laminate could bear the load continually after local crush and delamination. Displacements of calculated result with stiffness degradation model matched test results well.
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He, Jun, Yu Qing Liu, Chen Zhao, Ai Rong Chen, and Teruhiko Yoda. "Mechanical Behavior of Composite Girder with Perfobond Shear Connector under Hogging Moment." Advanced Materials Research 446-449 (January 2012): 1046–53. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.1046.
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The mechanical behavior of the support regions for continuous composite girders with tensile stresses in the concrete slab and compressive stresses in the lower steel profile becomes strongly nonlinear under negative bending moments. A static test on four half-scale model of a steel and concrete composite girders with different shear connectors including studs and PBL under hogging moments was conducted and observed to evaluate the influence of shear connector on inelastic behavior such as flexural stiffness reduction, crack initiation and development in concrete slab. From the test results, the flexural stiffness and loading capacity of the composite girders were improved by PBL shear connector. Higher initial cracking load and crack resistance stiffness of composite girders with PBL shear connector under serviceability limit state was obtained during crack development process. The test specimen could be assumed as full composite section until the ultimate state from load-slip relationship of shear connector. Analytical and experimental studies can serve as a basis for continuous composite bridges design.
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Liu, Guangsheng, Xiaocong Yang, and Lijie Guo. "Stiffness Determination of Backfill-Rock Interface to Numerically Investigate Backfill Stress Distributions in Mine Stopes." Advances in Civil Engineering 2021 (October 19, 2021): 1–13. http://dx.doi.org/10.1155/2021/6460764.
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Numerical modeling is an effective and efficient method to investigate the stress distributions of backfill in stopes, which should be well understood in underground mining. Interface elements between backfill and rock in simulated stopes had been proved to be essential components, for which the stiffness parameters need to be assessed and assigned. However, few reports have revealed the effects of interface stiffness on backfill stress distributions, and there is not yet a clear solution to determine the interface stiffness to simulate stresses in backfilled stopes, except an empirical method for simply applying a high value suggested in FLAC manual. In this study, a new solution is first proposed to determine the normal stiffness and shear stiffness of interface elements, respectively, in numerical modeling of backfill stresses. The applicability of the solution has been verified by investigating backfill stress distributions in mine stopes of two widely used mining methods with variable stiffness values. The results show that the newly proposed method leads to totally the same backfill stress distributions with models applying the interface stiffness by the method in FLAC manual based on a “rule-of-thumb” but will save at least 20%–30% calculation time to improve modeling efficiency under the same simulation conditions and will carry much clear physical meanings corresponding to the interaction between backfill and rock walls in mine stopes. In addition, the vertical and horizontal stresses show good agreements with the analytical stresses predicted by the Marston equation under the at-rest state, which validates the reliability of the proposed solution for interface stiffness. Moreover, the plotting methods of stress distributions and the coefficient of lateral earth pressure of backfill in simulated stopes with proposed interface stiffness were discussed to further clarify the reasonable methods to investigate the backfill stresses in mine stopes, especially after considering the effects of the convergence from rock walls, which is a very significant and common phenomenon in practical mining engineering.
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Zhang, Peng, Dan Shen, and Shi Rong Li. "Analysis of Stress Distribution of Externally Pre-Stressed Beams under Transverse Loads." Applied Mechanics and Materials 166-169 (May 2012): 3065–70. http://dx.doi.org/10.4028/www.scientific.net/amm.166-169.3065.
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The size, the position and the arrangement of external restraint will significantly affect the mechanical properties of the structures with the external restraint. Based on classical beam theory, the stress distribution of a simply supported beam with externally reinforcing steel bars under transverse loads is analyzed in this presentation. By assuming that the stresses in both the beam and the external constrains are less than their proportional limits, an analytical formulation of normal stress in the cross section of the beam was derived by considering two cases that the externally reinforcing steel bars are pre-stressed and are not pre-stressed. Influences of the parameters of the stiffness and the position of the externally reinforcing steel bars on the stress of the beam are discussed.
Dissertations / Theses on the topic "Stiffness under stresses"
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Mohamed, Ahmed Abdeldayem. "Behavior, strength and flexural stiffness of circular concrete columns reinforced with FRP bars and spirals/hoops under eccentric loading." Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/11406.
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Abstract : Deterioration of concrete structures reinforced with steel bars can be seen daily in regions with aggressive weather as steel-corrosion problems worsen. Fiber-reinforced-polymers (FRP) reinforcement has proven its feasibility through different civil structural elements. Present guidelines for FRP structures in North-America and Europe have not yet handled axially loaded members, due to the lack of research and experiments. This research takes charge of providing experimental database as well as extensive analyses and design recommendations of circular concrete columns reinforced totally with different FRP bars and spirals/hoops (FRP-RC columns). Full-scale columns were tested under monotonic loading with different levels of eccentricity. Test variables included the eccentricity-to-diameter ratio (e/D); reinforcement type (GFRP and CFRP vs. steel); concrete strength; longitudinal and transverse reinforcement ratio; and confinement configuration. All specimens measured 305 mm diameter and 1500 mm height. Test results indicated that specimens reinforced with glass-FRP (GFRP) or carbon-FRP (CFRP) reached their peak strengths with no damages to GFRP or CFRP rebar on either side of specimens. Specimens with CFRP reinforcement (CFRP-RC) behaved very similarly to their steel counterparts, and achieved almost the same nominal axial forces. Specimens with GFRP reinforcement (GFRP-RC) exhibited, however, reduced stiffness and achieved lower nominal axial forces than their steel or CFRP counterparts. Failure of GFRP-RC and CFRP-RC specimens was dominated by concrete crushing at low levels of eccentricity (e/D ratios of 8.2% and 16.4%). Experimental strain results revealed that GFRP bars developed high levels of strains and stresses on the compression and tension sides and hence the GFRP-RC specimens could sustain constant axial load after peak for some time up to the limit of concrete crushing at higher levels of eccentricity (e/D ratios of 8.2% and 16.4%), which help to delay the full damage. At these levels, flexural–tension failure initiated in the GFRP-RC specimens resulting from large axial and lateral deformations and cracks on the tension side until secondary compression failure occurred due to strain limitations in concrete and degradation of the concrete compressive block. The failure of CFRP-RC specimens at higher levels of eccentricity (e/D ratios of 8.2% and 16.4%) was characterized as flexural–compression in which it took place in a less brittle manner. On the other hand, this research also included different studies to analyze the test results, evaluate rebar efficiency, and provide recommendations for analysis and design. It was, therefore, indicated that the axial and flexural capacities of the tested FRP-RC specimens could be reasonably predicted using plane sectional analysis, utilizing the equivalent rectangular stress block (ERSB) parameters given by the ACI 440.1R-15 or CSA S806-12. All predictions underestimated the actual strength with variable levels of conservatism ranged between 1.05 to 1.25 for the GFRP-RC specimens and between 1.20 to 1.40 for the CFRP-RC specimens. These levels were noticeably reduced to critical limits in specimens with high-strength concretes. An elaborate review was made to the available ERSB parameters in the present steel and FRP design standards and guidelines. Modified expressions of the ERSB given in ACI 440.1R-15 and CSA S806-12 were developed. The results indicated good correlation of predicted and measured strength values with enhanced levels of conservatism. Additionally, sets of axial force–bending moment (P-M) interaction diagrams and indicative bar charts are introduced, and recommendations drawn. The compressive-strength contribution of FRP reinforcement was thoroughly reviewed and discussed. The minimum GFRP and CFRP reinforcement ratios to avoid rebar rupturing were broadly examined. Finally, the flexure stiffness (EI) of the tested specimens was analytically determined and compared with the available expressions using experimental and analytical M-ψ responses. Proposed equations are developed and validated against the experimental results to represent the stiffness of GFRP-RC and CFRP-RC columns at service and ultimate levels.La détérioration des structures en béton armé avec des barres d’armature d’acier peut être observée quotidiennement dans les régions à climat agressif. Le renforcement interne en polymères renforcés de fibres (PRF) a démontré sa faisabilité grâce à différents éléments structuraux en génie civil. Les lignes directrices actuelles pour les structures en béton armé de PRF en Amérique du Nord et en Europe n'ont pas encore gérées les sections soumises à des efforts axiaux excentrique, en raison du manque de recherches et d'expériences. Cette recherche permet d’augmenter la base de données expérimentales ainsi établir des analyses approfondies et des recommandations de conception pour les colonnes circulaires en béton armé complètement renforcées de PRF (barres et spirales). Des grandeur-nature colonnes ont été testées sous charge monotone avec différents niveaux d'excentricité. Les variables de test comprenaient le rapport excentricité / diamètre (e/D) ; le type de renfort (PRFV et PRFC comparativement à l’acier); la résistance du béton en compression; le taux d’armature longitudinal et transversal; et la configuration de l’armature de confinement. Tous les échantillons mesuraient 305 mm de diamètre et 1500 mm de hauteur. Les résultats des tests ont indiqué que les spécimens renforcés avec des PRF de verre ou des PRF de carbone atteignaient leur résistance maximale sans endommager les barres d’armature. Des deux types de renforcement, les spécimens de PRFCCFRP se comportaient de manière très similaire à leurs homologues en acier et atteignaient presque les mêmes résistances axiales. Cependant, les spécimens avec renforcement en PRFV ont présenté une rigidité réduite et des forces axiales nominales inférieures à celles de leurs homologues en acier ou en PRFC. Le mode de rupture des spécimens de PRFC et de PRFV a été dominé par l’écrasement du béton à de faibles niveaux d'excentricité (rapports e/D de 8,2% et 16,4%). Les résultats ont révélé que les barres de PRFV ont développé des niveaux élevés de déformations et de contraintes sur les faces en compression et en tension et, par conséquent, les spécimens de PRFVC pourraient supporter une charge axiale constante après la résistance ultime pendant un certain temps jusqu'à la limite de la rupture en compression du béton du noyau à des niveaux supérieurs d'excentricité (rapport e/D de 8,2% et 16,4%), ce qui contribue à retarder la dégradation. À ces niveaux, une rupture en tension a été initiée dans les spécimens de PRFV résultant à de grandes déformations axiales et latérales et des fissures du côté de la face en tension jusqu'à ce que la rupture en compression du béton. La rupture des spécimens de PRFC à des niveaux supérieurs d'excentricité (rapport e/D de 8,2% et 16,4%) a été caractérisé comme étant en compression du béton dans laquelle il s'est déroulé de manière moins fragile. D'autre part, cette recherche comprenait également différentes études pour analyser les résultats des tests, évaluer l'efficacité des barres d'armature et fournir des recommandations pour l'analyse et la conception. Il a donc été indiqué que les capacités axiales et de flexion des spécimens en PRF testées pourraient être raisonnablement prédites en utilisant une analyse en section plane, en utilisant les paramètres du bloc de contrainte rectangulaire équivalent (BCRE) donnés par l'ACI 440.1R-15 ou la CSA S806- 12. Toutes les prédictions ont sous-estimé la résistance réelle avec des niveaux de variabilité conservateur entre 1,05 et 1,25 pour les spécimens de PRFC et entre 1,20 et 1,40 pour les spécimens de PRFC. Ces niveaux ont été nettement réduits à des limites critiques dans les spécimens avec des bétons à haute résistance. Un examen approfondi a été effectué sur les paramètres du BCRE disponibles dans les normes et les directives de conception actuelles en acier et en PRF. Les expressions modifiées du BCRE fournies dans ACI 440.1R-15 et CSA S806-12 ont été développées. Les résultats indiquent une bonne corrélation entre les valeurs de résistance prédites et mesurées avec des niveaux accrus de conservatisme. La contribution de la résistance à la compression du renforcement en PRF a été soigneusement examinée et discutée. Le taux d’armature minimum de PRFV et de PRFC pour éviter la rupture de l'armature ont été largement examinés. Enfin, la rigidité en flexion (EI) des spécimens testés a été déterminée de manière analytique et comparée aux expressions disponibles dans la littérature en utilisant les réponses expérimentales et analytiques M-ψ. Les expressions modifiées de la rigidité en flexion EI apportées dans l’ACI 440.1R ont été développées et validées.
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(12804799), Bruce Arthur Jordan. "Duration of load behaviour of an aligned strand wood composite (ASC)." Thesis, 1994. https://figshare.com/articles/thesis/Duration_of_load_behaviour_of_an_aligned_strand_wood_composite_ASC_/20010698.
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An aligned strand, wood composite (ASC) material was subjected to a two year duration of load (DOL) study. The experimental work was conducted in Mt. Gambier South Australia from a purpose built shed housing 42 back to back (double) vertically oriented specimen test rigs in an atmosphere not controlled for temperature and relative humidity. A total of 244 specimens were tested in two population groups, each group divided into two subgroups. One subgroup each for short term static Modulus of Rupture (MOR) and Modulus of Elasticity (MOE), and the other for long term bending strength and stiffness under stresses varying from 0.4MOR to 0.9MOR.
Creep and creep - rupture observations were taken over a two year period providing an extensive database for the evaluation of DOL properties. Monte Carlo simulations were used to give confidence in the process of assigning MOR values to the long term specimens using a statistical matched distribution technique for long term strength evaluation.
Creep and creep - rupture responses for the ASC were similar in effect but fifty percent greater in magnitude than that predicted for solid seasoned timber by AS1720.1-1988, the Australian Timber Structures Code. Creep design multipliers, and long term strength design multipliers in both working stress and limit state design formats were derived for the ASC.
A limiting strain criterion was established for the ASC and was observed to be independent of time under load and applied stress intensity. A failure strain model was presented for the ASC in a form enabling the determination of a limiting deflection for flexural (beam) members at failure.
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Chen, Hsin-I., and 陳欣儀. "Investigations on stiffness degradation behavior by undrained triaxial tests under different stress paths." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/uec7kn.
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碩士國立臺灣科技大學
營建工程系
99
Behaviors of high initial Young’s modulus and stiffness degradation were observed on Taipei silty clay, and were applied to the numerical analysis in excavations with advanced soil models. The analysis with consideration of high initial Young’s modulus and stiffness degradation under axial compression condition yields in better prediction results. However, stress paths in a real excavation are different for soil elements at different positions. Thus, the degradation behavior of stiffness for soils under different stress paths should be investigated. This study presented a series of CK0U (K0 consolidation and undrained shearing) unloading-reloading triaxial tests under three stress paths, i.e. AC (axial compression), AE (axial extension), and LC (lateral extension), with bender element tests. Test results demonstrated that both secant Young’s moduli and shear moduli degraded with the increase of strain and stress level. From results of AC and LE tests, stiffness degradation ratios for tested soil versus axial strains are unique (or stress path independent). Nevertheless, the degradation ratio versus the stress level is affected by the failure strain and dependent on stress paths.
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Bewick, Robert P. "Shear Rupture of Massive Brittle Rock under Constant Normal Stress and Stiffness Boundary Conditions." Thesis, 2013. http://hdl.handle.net/1807/43475.
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The shear rupture of massive (intact non-jointed) brittle rock in underground high stress mines occurs under a variety of different boundary conditions ranging from constant stress (no resistance to deformation) to constant stiffness (resistance to deformation). While a variety of boundary conditions exist, the shear rupture of massive rock in the brittle field is typically studied under constant stress boundary conditions. According to the theory, the fracturing processes leading to shear rupture zone creation occur at or near peak strength with a shear rupture surface created in the post-peak region of the stress-strain curve. However, there is evidence suggesting that shear rupture zone creation can occur pre-peak. Limited studies of shear rupture in brittle rock indicate pre-peak shear rupture zone creation under constant stiffness boundary conditions. This suggests that the boundary condition influences the shear rupture zone creation characteristics.
In this thesis, shear rupture zone creation in brittle rock is investigated in direct shear under constant normal stress and normal stiffness boundary conditions. It is hypothesized that the boundary condition under which a shear rupture zone is created influences its characteristics (i.e., shear rupture zone geometry, load-displacement response, shear rupture zone creation relative to the load-displacement curve, and peak and ultimate strengths). In other words, it is proposed that the characteristics of a shear rupture zone are not only a function of the rock or rock mass properties but the boundary conditions under which the rupture zone is created.
The hypothesis is tested and proven through a series of simulations using a two dimensional particle based Distinct Element Method (DEM) and its embedded grain based method. The understanding gained from these simulations is then used in the analysis and re-interpretation of rupture zone creation in two mine pillars. This is completed to show the value and practical application of the improved understanding gained from the simulations. The re-interpretation of these case histories suggests that one pillar ruptured predominately under a constant stress boundary condition while the other ruptured under a boundary condition changing from stiffness to stress control.
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Zhang, D., J. Ye, and Dennis Lam. "Ply cracking and stiffness degradation in cross-ply laminates under biaxial extension, bending and thermal loading." 2006. http://hdl.handle.net/10454/5794.
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Transverse ply cracking often leads to the loss of stiffness and reduction in thermal expansion coefficients. This paper presents the thermoelastic degradation of general cross-ply laminates, containing transverse ply cracks, subjected to biaxial extension, bending and thermal loading. The stress and displacement fields are calculated by using the state space equation method [Zhang D, Ye JQ, Sheng HY. Free-edge and ply cracking effect in cross-ply laminated composites under uniform extension and thermal loading. Compos Struct [in press].]. By this approach, a laminated plate may be composed of an arbitrary number of orthotropic layers, each of which may have different material properties and thickness. The method takes into account all independent material constants and guarantees continuous fields of all interlaminar stresses across interfaces between material layers. After introducing the concept of the effective thermoelastic properties of a laminate, the degradations of axial elastic moduli, Poisson¿s ratios, thermal expansion coefficients and flexural moduli are predicted and compared with numerical results from other methods or available test results. It is found that the theory provides good predictions of the stiffness degradation in both symmetric and antisymmetric cross-ply laminates. The predictions of stiffness reduction in nonsymmetric cross-ply laminates can be used as benchmark test for other methods.
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Lam, Dennis, D. Zhang, and J. Ye. "Ply cracking and stiffness degradation in cross-ply laminates under biaxial extension, bending and thermal loading." 2005. http://hdl.handle.net/10454/5555.
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Transverse ply cracking often leads to the loss of stiffness and reduction in thermal expansion coefficients. This paper presents the thermoelastic degradation of general cross-ply laminates, containing transverse ply cracks, subjected to biaxial extension, bending and thermal loading. The stress and displacement fields are calculated by using the state space equation method [Zhang D, Ye JQ, Sheng HY. Free-edge and ply cracking effect in cross-ply laminated composites under uniform extension and thermal loading. Compos Struct [in press].]. By this approach, a laminated plate may be composed of an arbitrary number of orthotropic layers, each of which may have different material properties and thickness. The method takes into account all independent material constants and guarantees continuous fields of all interlaminar stresses across interfaces between material layers. After introducing the concept of the effective thermoelastic properties of a laminate, the degradations of axial elastic moduli, Poisson's ratios, thermal expansion coefficients and flexural moduli are predicted and compared with numerical results from other methods or available test results. It is found that the theory provides good predictions of the stiffness degradation in both symmetric and antisymmetric cross-ply laminates. The predictions of stiffness reduction in nonsymmetric cross-ply laminates can be used as benchmark test for other methods.
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LAI, YU-LIN, and 賴昱霖. "Dynamic Stress Analysis and Multi-Objective Optimization Design of an On-Road Bicycle Frame Under Fatigue and Stiffness Test." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/u7pkya.
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碩士國立高雄第一科技大學
機械與自動化工程系碩士班
105
The aim of this paper is to present an integrated procedure for the optimization of dimensions of an on-road bicycle frame under horizontal, vertical and pedaling fatigue test and stiffness simulation. The procedure is composed of uniform design of experiments, explicit dynamics finite element analysis, Kriging interpolation, compromise programming method. The experimental design is used to plan a set of experiments with multiple factors of bike frame size by uniform design. Then, the bicycle frame in each experiment is analyzed by ANSYS/Workbench to obtain the maximum stress and deformation value. Then, Kriging interpolation is applied to construct the surrogate model of permanent deformation, maximum stress and bicycle mass based on the input and output data of experiment simulations. In order to get minimize the mass, maximum stress and permanent deformation of bicycle frame at the same time. First, to compose the each target be a single objective function by compromise programming method with weighting factors. Then, the bicycle frame stiffness simulation and mass is used to find the best weighting factors. Finally, generalized reduced gradient algorithm combine GRG algorithm method applied to find the optimal solution of dimensions of bicycle frame under the goal of minimize the mass, maximum stress and permanent deformation. From result, after performing the optimization procedure presented in this paper, the improvement rate of the horizontal test of maximum von Mises stress is 2.12%, the vertical test of maximum von Mises stress is 6.73%, the pedal test of maximum von Mises stress is 1.97%, the stiffness of maximum deformation is 1.28%, the mass of bicycle is 3.81%. Generally, successful achieve multi object design of optimization and the lightweight and high strength design of the bicycle frame.
Books on the topic "Stiffness under stresses"
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Luk'yanov, Mihail. Collection of problems in strength of materials. ru: INFRA-M Academic Publishing LLC., 2020. http://dx.doi.org/10.12737/989326.
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Given objectives for all sections of the course "strength of materials", studied by students in accordance with the existing program for Russian universities. Along with the classical methods of assessing strength are the basic concepts of fracture mechanics and methods of calculations on strength, stiffness and stability of structures.
Detailed solution of the task allows the subject to students of day and correspondence forms of training. The unconventional construction of the book are aimed at improving the learning material. Almost all tasks are accompanied by answers.
In the Appendix to the book gives some reference materials: table of Standards, values, functions, A. N. Krylov and hyperbolic functions, as well as data relevant to the calculation of strength under cyclic stresses.
Meets the requirements of Federal state educational standards of higher education of the last generation.
Designed for students in all specialties of railway transport, the study of mechanics of materials.
Book chapters on the topic "Stiffness under stresses"
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Xu, Guoping, Qingfei Huang, Shenyou Song, Hai Ji, Bin Deng, and Tian Song. "Research on Mechanical Properties of Steel Shell Concrete Immersed Tube Shear Connectors." In Advances in Frontier Research on Engineering Structures, 295–312. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-8657-4_27.
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AbstractStructural designs of shear connector in immersed tunnel is one of the most significant key technical problems in tunnel designing. According to investigations conducted in Shenzhong Link project, this paper combined numerical simulation methods and experimental verifications and to research effects of shear connector void, stress state, and opening holes on performances of steel–concrete connectors, and also discussed differences of shear slip curves under the influence of factors above, as well as impacts on bearing capacities and stiffnesses of connectors. Through numerical simulations of void and non-void connectors by finite element method, patterns of concrete stress, connector behaviors under tension and compression and shear stresses were analyzed respectively. Additionally, reductions of bearing capacity and stiffness caused by voids and openings which were controlled as variables were discussed. Furthermore, a calculation formula of shear connector bearing capacity is proposed which is in consistent with experimental verifications with considerations of void, stress state and opening. Researches in this paper could provide knowledge for reasonable structural designs of structural connectors in future immersed tunnel engineering construction.
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Shepelenko, Ihor, Yuri Tsekhanov, Yakiv Nemyrovskyi, Pavlo Eremin, and Oleh Bevz. "Plasticity Studies During Deformation Under Conditions of Significant Negative Values of the Stiffness Coefficient of the Stress State." In New Technologies, Development and Application IV, 215–23. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-75275-0_25.
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Newnham, Robert E. "Elasticity." In Properties of Materials. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780198520757.003.0015.
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All solids change shape under mechanical force. Under small stresses, the strain x is related to stress X by Hooke’s Law (x) = (s)(X), or the converse relationship (X) = (c)(x). The elastic compliance coefficients (s) are generally reported in units of m2/N, and the stiffness coefficients (c) in N/m2. For a fairly stiff material like a metal or a ceramic, c is about 1011 N/m2 = 1012 dynes/cm2 = 100 GPa = 0.145 × 108 PSI. Hooke’s Law is a linear relation between stress and strain, and does not describe the elastic behavior at high stress levels that requires higher order elastic constants (Chapter 14). Irreversible phenomena such as plasticity and fracture occur at still higher stress levels. Two directions are needed to specify stress (the direction of the force and the normal to the face on which the force acts), and two directions are needed to specify strain (the direction of the displacement and the orientation of the measurement axis). Thus there are four directions involved in measuring elastic stiffness, which is therefore a fourth rank tensor: . . . Xij = cijklxkl . . . .
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Yang, Jianhui, Wenchao Zhi, Xujun Tang, Qinting Wang, and Tom Cosgrove. "Comparison of Bond Properties Between ALWSCC and Steel Bars Based on Different Test Methods." In Advances in Transdisciplinary Engineering. IOS Press, 2021. http://dx.doi.org/10.3233/atde210143.
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Reasonable evaluation of the bond performance between steel bars and concrete has important theoretical and practical value for reinforced concrete structural design and seismic analysis. The stress (τ) – strain (ε) formula is corrected based on a pull-out test, and the load (F) – deflection (w) curves are analyzed according to the change of stiffness before and after crack appearance based on a beam test, and new estimation formulas are given. At the same time, the bond properties are compared between all-lightweight shale ceramsite concrete (ALWSCC) and normal weight concrete (NWC). The results show that the bond property of ALWSCC is better than NWC. The bond stresses of pull-out specimens and beam specimens are the same or similar under equal conditions, but the ultimate load (F0) of the former is about 3.66 times that of the latter, the peak slip (S0) of the latter is 4.80 times that of the former, and the latter has significant splitting or pull-out failure characteristics. The peak slip (S0) in this paper is larger than that in the related literature, where the pull-out specimens are no more than 10 mm, and are generally less than 2 mm, while the beam specimens are not more than 3 mm, with the others generally around 1 mm. The research results have reference values and guiding significance for similar experimental research and engineering practice.
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Melhem, George Nadim. "Aerospace Fasteners: Use in Structural Applications." In Encyclopedia of Aluminum and Its Alloys. Boca Raton: CRC Press, 2019. http://dx.doi.org/10.1201/9781351045636-140000240.
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Aircraft components need to be selected and manufactured to adequately combat the environment, temperature, loading, compatibility, and so on. When structural materials such as aluminum alloys or fiber-reinforced polymer composites need to be joined in aircraft, the selection of fasteners, bolts, rivets, adhesives, and other methods need to be quantitatively assessed in order that the correct design for the component and joining method is identified. There is a variety of fasteners, bolts, and rivets, made using a variety of materials. Aluminum rivets are often used to join aluminum components in an aircraft. Rivets do not perform well under tension loading, but perform better in shear, thus limiting the application specifically for these purposes. Bolts are designed to clamp material together, and even though the bolt may be adequate to support a particular structure and load requirement, consideration must also be given to the modulus of elasticity and stiffness of the components that are being clamped together. Therefore, an understanding of each of the materials being clamped or joined together is necessary. Bolts manufactured from steel, for instance, have coatings applied in order to help protect them from corrosion. The use of composites translates to a reduced number of rivets and fasteners to be used. Drilling of holes into composites to insert fasteners poses many challenges because the fibers are damaged, a region of high stress concentration may be formed, and the hole is a site for the ingress of water or moisture. The insertion of aluminum fasteners or the contact of aluminum components with carbon fibers creates galvanic corrosion due to the large difference in electrical potential. Titanium alloy (Ti-6Al-4V) is a typical fastener where there is composite joining due to its better compatibility (elimination of galvanic corrosion) and increased strength properties. Substitution of rivets and fasteners for welding is also on the increase in aircraft because laser beam welding (LBW) and friction stir welding both reduce cracking, porosity, and better properties achieved due to deeper penetration, and reduce the heat-affected zone which would typically be undesirable with conventional arc welding such as metal inert gas and tungsten inert gas welding. The shear and compressive stresses are increased, and fatigue cracking, weight, and cost are also reduced as a result of LBW, including the elimination of stresses and corrosion associated with rivets and the elimination of adhesives. Dissimilar metals such as the 7000 series and the 2000 series can be joined with a filler metal compatible to both metals to mitigate galvanic corrosion.
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Gomes Correia, A., L. Q. AnhDan, J. Koseki, and F. Tatsuoka. "Small strain stiffness under different isotropic and anisotropic stress conditions of two granular granite materials." In Advanced Laboratory Stress-Strain Testing of Geomaterials, 209–15. Routledge, 2018. http://dx.doi.org/10.1201/9781315136776-11.
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Newnham, Robert E. "Thermodynamic relationships." In Properties of Materials. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780198520757.003.0008.
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In the next few chapters we shall discuss tensors of rank zero to four which relate the intensive variables in the outer triangle of the Heckmann Diagram to the extensive variables in the inner triangle. Effects such as pyroelectricity, permittivity, pyroelectricity, and elasticity are the standard topics in crystal physics that allow us to discuss tensors of rank one through four. First, however, it is useful to introduce the thermodynamic relationships between physical properties and consider the importance of measurement conditions. Before discussing all the cross-coupled relationships, we first define the coupling within the three individual systems. In a thermal system, the basic relationship is between change in entropy δS [J/m3] and change in temperature δT [K]: . . . δS = CδT, . . . where C is the specific heat per unit volume [J/m3 K] and T is the absolute temperature. S, T, and C are all scalar quantities. In a dielectric system the electric displacement Di [C/m2] changes under the influence of the electric field Ei [V/m]. Both are vectors and therefore the electric permittivity, εij , requires two-directional subscripts. Occasionally the dielectric stiffness, βij , is required as well. . . . Di = εijEj Ei = βijDj. . . . Some authors use polarization P rather than electric displacement D. The three variables are interrelated through the constitutive relation . . . Di = Pi + ε0Ei = εijEj. . . . The third linear system in the Heckmann Diagram is mechanical, relating strain xij to stress Xkl [N/m2] through the fourth rank elastic compliance coefficients sijkl [m2/N]. . . . xij = sijklXkl. . . . Alternatively, Hooke’s Law can be expressed in terms of the elastic stiffness coefficients cijkl [N/m2]. . . Xij = cijklxkl. . . . When cross coupling occurs between thermal, electrical, and mechanical variables, the Gibbs free energy G(T, X, E) is used to derive relationships between the property coefficients. Temperature T, stress X, and electric field E are the independent variables in most experiments.
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Wang, Liangwen, Yangguang Kong, Tianyun He, Hongwei Hao, Ruolan Wang, Zhigang Zhang, and Weiwei Zhang. "Collision Simulation of Inner Brace Grasping Manipulator During Operation Based on Grasping Impact Velocity Variation." In Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220208.
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For the needs of gripping and transferring and assembling thin-walled fragile parts in industrial production, an internally supported manipulator configuration with finger-palm synergy features for thin-walled brittle cylindrical inner workpieces is proposed. Due to the poor impact resistance and low tensile strength of brittle materials, they are easily broken during the manipulator operation. In order to find the internal brace gripper finger configuration and stiffness matching for the operation of thin-walled fragile parts, and to explore the contact-collision law of the gripping process, the finite element model of the mechanical finger end parts was established by the integrated modeling method of Hypermesh and other software, and the change of the internal force of the mechanical finger contact with the workpiece when the gripping impact speed changes was studied. The corresponding constraints, loads and contact types are applied to the finite element model by LS-prepost software, and post-processing is performed to calculate the stress and strain clouds during the contact collision of the fragile parts. The simulation results show that the stress on the fragile part increases linearly with the increase of the impact speed of the manipulator: Under the speed of 4 mm/ms, the stress increases linearly and slowly. When the speed goes from 0.5 mm/ms to 4 mm/ms, the stress increases about 8 times in X, XY direction and about 14 times in Maximum Principal, Y direction. Above the velocity of 4 mm/ms the stress increases sharply and the model is destroyed. The results of the study establish the basis for optimizing the manipulator’s operating process.
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Li, Longping, Linfeng Wang, Xiaohan Zhou, Yunlu Bai, and Qiang Xu. "Study on Deformation Characteristics and Instability Failure Mode of New Suspended Diaphragm Wall Deep Excavation in Soil-Rock Strata." In Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220929.
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In the design of suspended diaphragm wall of existing soil-rock foundation pit, the bottom of the wall needs to reserve rock shoulder to provide embedding, and prestressed anchor should be used to lock the foot at the same time. It is the first time to propose a new type of suspended diaphragm wall supporting structure without rock shoulder and prestressed anchor, and makes full use of the inner struts and the middle plate of the underground structure to form a stable system, which lacks engineering experience and theoretical verification. By means of numerical simulation, the deformation characteristics and instability failure mode of soil-rock foundation pit supported by the new type of suspended diaphragm wall were discussed. The research shows that: (1) The deformation of the excavation meets the requirements under the supporting of the new suspended diaphragm wall without rock shoulder. The deformation of the wall mainly occurs in the soil section, and the deformation is mainly caused by the lateral water and soil pressure of soil. The shear stress distribution of the rock section shows that the top of the rock section is not the control point, and there is no need to take additional measures. (2) The method of ground overload can cause the damage of the supporting system components. At this time, the deformation of the rock section is still small, and the safety reserve of the rock wall section is higher than that of the supporting section. (3) By increasing the stiffness of the upper supporting structure to ensure the stability of the upper supporting structure, and increasing the ground overload to study the failure mode of the lower rock section, it is found that the failure mode of the lower rock section is that the shear stress exceeds the allowable shear strength and produces a sliding surface, and the maximum shear stress occurs at the junction of the rock section and the basement.
Conference papers on the topic "Stiffness under stresses"
1
Darji, P. H., and D. P. Vakharia. "Stiffness Optimization of Hollow Cylindrical Rolling Element Bearing." In STLE/ASME 2008 International Joint Tribology Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/ijtc2008-71009.
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Since being originally introduced, cylindrical rolling element bearings have been significantly improved, in terms of their performance and working life. A major objective has been to decrease the Hertz contact stresses at the roller–raceway interfaces, because these are the most heavily stressed areas in a bearing. It has been shown that bearing life is inversely proportional to the stress raised to the ninth power (even higher). Investigators have proposed that under large normal loads a hollow element with a sufficiently thin wall thickness will deflect appreciably more than a solid element of the same size. An improvement in load distribution and thus load capacity may be realized, as well as contact stress is also reduced considerably by using a bearing with hollow rolling elements. Since for hollow rolling element no method is available for the calculation of contact stresses and deformation. The contact stresses in hollow members are often calculated by using the same equations and procedures as for solid specimens. This approach seems to be incorrect. Recently, the Finite Element Analysis (FEA) has been successfully used to evaluate contact problems for the roller bearings. Investigations have been made for hollow rollers in pure normal loading. Different hollowness percentages ranging from 0% to 90% have been analysed in FEA software to find the optimum percentage hollowness which gives minimum stress and finally longest fatigue life.
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Clark, Russell, Mohammed Shubaili, Ali Elawadi, Sarah Orton, and Ying Tian. "Time Dependent Strength and Stiffness of Shear Controlled Reinforced Concrete Beams under High Sustained Stresses." In Structures Congress 2020. Reston, VA: American Society of Civil Engineers, 2020. http://dx.doi.org/10.1061/9780784482896.005.
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Bushmanov, Aleksandr, and D. Mel'nichenko. "MODELING OF SPOKE STIFFNESS FOR EXTERNAL FIXATION DEVICES." In XIV International Scientific Conference "System Analysis in Medicine". Far Eastern Scientific Center of Physiology and Pathology of Respiration, 2020. http://dx.doi.org/10.12737/conferencearticle_5fe01d9b7fe4e6.75478054.
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A nonlinear calculation of the stiffness of the spokes of external fixation devices in traumatology is proposed. Taking into account the geometric nonlinearity of the spoke, the finite element method is used in the calculations of stiffness and stresses arising in the spoke fasteners. Under the action of the transverse force and its preliminary tension, deflections of the spoke and stresses in the attachment points are determined.
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Qiu, Chen, Ketao Zhang, Jing Shan Zhao, and Jian S. Dai. "Stiffness Design, Analysis and Validation of a Parallel-Mechanism Equivalent Suspension System." In ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-46641.
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This paper provides a systematic approach to design a vehicle’s independent suspension system. In this approach, multi-link type suspension is selected. By treating it as a parallel mechanism, both the kinematic design and force analysis are conducted in the same framework of screw theory. Regarding the kinematic design, constraint-based approach is used to find suitable layouts of constraint limbs in accordance with desired degree of freedom. In the force analysis, stiffness matrix of the suspension mechanism is developed, leading to the deformation and stress analysis under various critical loads. The developed formulae are further utilized to design suitable suspension mechanism, followed by finite-element-simulation validation as well as optimization design to reduce the resulted maximum stresses.
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Lin, Chen-Chi, and Clayton D. Mote. "The Criteria Predicting Wrinkling of Thin, Flat, Rectangular Webs." In ASME 1995 Design Engineering Technical Conferences collocated with the ASME 1995 15th International Computers in Engineering Conference and the ASME 1995 9th Annual Engineering Database Symposium. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/detc1995-0148.
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Abstract A web is termed wrinkled when one of the in-plane principal stresses is tensile and the other is sufficiently compressive. A criterion is derived that predicts wrinkling of isotropic, compressible rectangular webs under uniform in-plane principal stresses. The compressive stress at impending wrinkling depends on the flexural stiffness, and it equals zero in the case of a membrane. A criterion of wrinkling is also derived using isotropic, incompressible membrane theory. This criterion predicts an infinite number of wrinkle waves in a wrinkled region. With small flexural stiffness, the number of wrinkle waves becomes finite at wrinkling and it is predictable along with the shape and the size of the wrinkled region. The number of the wrinkle waves increases as the aspect ratio of the rectangular web increases, as the in-plane principal tension increases, and as the flexural stiffness decreases. Analyses of wrinkling of a rectangular web under simple shear and uniform longitudinal stretching illustrate the above predictions.
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DOSHI, SAGAR M., PAUL D. SAMUEL, MOLLA A. ALI, ANDREW J. STACK, BAZLE Z. (GAMA) HAQUE, JOSEPH M. DEITZEL, and JOHN W. GILLESPIE, JR. "LOW VELOCITY IMPACT EXPERIMENTS OF S-2 GLASS-EPOXY COMPOSITES UNDER DIFFERENT ENVIRONMENTAL CONDITIONS." In Proceedings for the American Society for Composites-Thirty Seventh Technical Conference. Destech Publications, Inc., 2022. http://dx.doi.org/10.12783/asc37/36422.
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S-2 glass-epoxy composites are used in damage tolerant structural applications such as military ground vehicles due to their high specific strength, stiffness, and energy-absorbing capabilities. Composites can be susceptible to delamination failure caused due to high interlaminar shear stresses when subjected to transverse impact loading. While fiber fracture, fiber pullout, matrix cracking, and delaminations are the major damage mechanisms, delamination is a significant energy absorbing failure mode in low-velocity impacts (LVI). LVI leads to a reduction of stiffness and residual strength, which is critical for structural integrity. To improve the delamination resistance, researchers have used various types of interlayers for composites subjected to impacts. In this research, LVI experiments are conducted on composites made using plain weave S-2 glass and SC-15 epoxy resin. Two types of specimens are tested, 'baseline' (without interlayer) and 'interlayer' (with thermoplastic interlayer UAF 472). A Dynatup 9200 drop tower with a hemi-cylindrical 12.7 mm impactor is used. The specimens are impacted (40J) at three temperatures, -55C, RT, and 76C. The stiffness before and after the LVI test is evaluated, and the influence of temperature and impacts on stiffness change is discussed, along with the mechanisms that cause the change in stiffness. The interlayer specimens have significantly smaller delamination areas, and the stiffness loss due to impact is also reduced (compared to baseline) at each temperature. However, since the properties of the resin and the TPU deteriorate at elevated temperatures, there is a drastic stiffness loss in interlayer specimens at elevated temperatures in the pristine, non-impacted samples.
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Naserkhaki, Sadegh, Jacob L. Jaremko, Greg Kawchuk, Samer Adeeb, and Marwan El-Rich. "Investigation of Lumbosacral Spine Anatomical Variation Effect on Load-Partitioning Under Follower Load Using Geometrically Personalized Finite Element Model." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-40231.
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The spinal load sharing and mechanical stresses developed in the spine segments due to mechanical loads are dependent on the unique spinal anatomy (geometry and posture). Variation in spinal curvature alters the load sharing of the lumbar spine as well as the stiffness and stability of the passive tissues. In this paper, effects of lumbar spine curvature variation on spinal load sharing under compressive Follower Load (FL) are investigated numerically. 3D nonlinear Finite Element (FE) models of three ligamentous lumbosacral spines are developed based on personalized geometries; hypo-lordotic (Hypo-L), normal (Normal-L) and hyper-lordotic (Hyper-L) cases. Analysis of each model is performed under Follower Load and developed stress in the discs and forces in the collagen fibers are investigated. Stresses on the discs vary in magnitude and distribution depending on the degree of lordosis. A straight hypo-lordotic spine shows stresses more equally distributed among discs while a highly curved hyper-lordotic spine has stresses concentrated at lower discs. Stresses are uniformly distributed in each disc for Hypo-L case while they are concentrated posteriorly for Hyper-L case. Also, the maximum force in collagen fibers is developed in the Hyper-L case. These differences might be clinically significant related to back pain.
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Zand, Benjamin B. "Vehicle Load Distribution Under Timber Mats and Flexible Slab." In 2020 13th International Pipeline Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/ipc2020-9599.
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Abstract Pipeline operators commonly use means of temporary crossing such as timber-mat, airbridge, and slab to reduce surface loading induced stresses in a buried pipeline at locations where a heavy vehicle crosses the buried pipeline. When a temporary crossing has a continuous contact with soil, (e.g. timber mat, flexible slab) load distribution over the ground surface is not immediately known. Load distribution under a timber-mat or flexible slab is a function of the slab to soil stiffness ratio. The load distribution tends to become more uniform with increasing timber-mat or slab stiffness. In this work an analytical model using beam-on-elastic-foundation has been developed and Laplace transform has been utilized to find the solution and apply free-end boundary conditions. The analytical solution can be used for any arbitrary load distribution over a beam-on-elastic foundation. In this work the solution for a point load and a partially distributed uniform load were employed as these scenarios can accurately represent conventional vehicle foot-prints, while being computationally efficient. The analytical solutions are compared to finite element analysis to validate the model. This model can be used in conjunction with the Canadian Energy Pipeline Association (CEPA) surface loading calculator (or similar tools) to analyze pipeline encroachment problems when means of temporary crossing is installed. This model can help the operators determine dimensions and bending stiffness of timber-mat or flexible slab to assure a desirable load distribution will be achieved. The model can also be used for structural analysis of a timber-mat or flexible slab under vehicular load.
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Liao, Lijuan, and Toshiyuki Sawa. "Axisymmetric Analysis of Mechanical Properties of Bonded Shrink Fitted Joints Under Torsional Loads." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-37214.
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Shrink fitting combining with anaerobic adhesives (bonded shrink fitted joints) has been widely used for joining cylindrical components in a lot of mechanical structures. This paper deals with mechanical properties (stress analysis and strength estimation) of the bonded shrink fitted joint in which a ring is fitted at the middle part of a shaft subjected to torsion. The stress distributions in the adhesive layer of bonded shrink fitted joint are analyzed using an axisymmetric theory of elasticity when an external torsion is applied to the upper end of the shaft. The effects of the stiffness, the outside diameter and the height of the ring on the interface stress distributions are clarified in the numerical calculations. The maximum shear stress, which shows singular stress property, initiates near the inside upper edge of the adhesive layer interface, where the rupture occurs in the joint under external torsional loads. In addition, the estimation method of joint strength is applied using the interface stress distributions and the modified singularity stresses expressions obtained from the analogous tests. It is found that the joint strength increases as the stiffness, the outside diameter and the height of the ring increase. Furthermore, experiments to measure the joint strength were carried out. Three-dimensional finite element (FEM) method is also adopted to verify the theoretical results. In addition, the strength of the bonded shrink fitted joint is compared with that of shrink fitted joint based on the experimental results, which is found that the strength of the bonded shrink fitted joints is greater than that of shrink fitted joints. The numerical results are in a fair good agreement with the experimental results and FEM results.
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Gravett, Phillip W., and Robert E. deLaneuville. "Analysis and Results of an SCS-6/Ti-15-3 MMC Reinforced Ring Structure Under Internal Radial Loading." In ASME 1993 Design Technical Conferences. American Society of Mechanical Engineers, 1993. http://dx.doi.org/10.1115/detc1993-0074.
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Abstract This paper presents a stress analysis method and test results of a ring structure reinforced with SCS-6/Ti-15-3 MMC under an applied internal radial load. To assess the structural integrity of an MMC reinforced component, the state of stress within the component must be determined. Two major factors complicating the state of stress in the given MMC reinforced rings are the stress concentrations caused by the load fixture and the thermal residual stresses induced during processing. To model the stress concentrations, the ring and its load fixture were modeled as a 3-d solid finite element model. To calculate the processing residual stresses, a 2-d axisymetric finite element thermal stress analysis was completed. Plasticity was modeled with the 2-d axisymetric finite element model accounting for the nonlinear response of the MMC core and monolithic sheath. Testing of the rings at room and high temperature showed good correlation to load-deflection calculations while ultimate strength was far less than predicted. Subsequent post failure analysis revealed preexisting damage within the MMC which was not detected by pretest NDE inspections. This damage did not significantly affect the measured stiffness of the ring, but diminished the ultimate strength by reducing the capability of the MMC in a localized area.
Reports on the topic "Stiffness under stresses"
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FATIGUE TESTS OF COMPOSITE DECKS WITH MCL CONNECTORS. The Hong Kong Institute of Steel Construction, December 2022. http://dx.doi.org/10.18057/ijasc.2022.18.4.7.
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Full-scale fatigue tests were performed on three composite decks with the MCL (modified clothoid) connectors to investigate their fatigue performance. Fatigue life and failure mode of the composite bridge decks were explored by measuring the specimens with three different stress amplitudes. The deflection, strain, carrying capacity, and stiffness degradation of the composite decks were measured and analyzed in the test. In addition, parameter analysis was performed using finite-element method in this study. Results showed that the mechanical performance of the composite decks accorded with the plane-section assumption under constant amplitude load, and the fatigue failure mode of the composite decks was the local fracture of the bottom steel plate. The stiffness degradation law and S-N curve were obtained in this study. Moreover, the concrete slab depth had a remarkable effect on the fatigue performance of the composite decks.
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NUMERICAL INVESTIGATION ON CYCLIC BEHAVIOR OF RING-BEAM CONNECTION TO GANGUE CONCRETE FILLED STEEL TUBULAR COLUMNS. The Hong Kong Institute of Steel Construction, December 2021. http://dx.doi.org/10.18057/ijasc.2021.17.4.7.
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As a promising composite structure, gangue concrete filled steel tubular (GCFST) column exhibites favarable characteristics including high strength and economic efficiency. This paper conducted numerical investiagations on structural behavior of a ring-beam connection to GCFST column with concrete beam under cyclic loading. Furthermore, finite element models of column-beam connections were developed using ABAQUS and validated against full-scale experimental tests to identify accuracy of selected modeling approaches. Using these validated models, stress distribution of each component was examined to study the force-transferring mechanism among the components and failure modes of the ring-beam connection. Research study indicated that the ring-beam connection showed a reasonable force-transferring mechanism under cyclic loading and the remarkable earthquake-resistant performance with high capacity and acceptable ductility. Finally, parametric studies were performed to assess the influences of beam-to-column stiffness ratio,steel ratio, axial load level, and concrete compressive strength on connection cyclic behaviors. Parametric studies provided some suggestions and references for the application of the ring-beam connection in various engineering projects.
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THE SEISMIC PERFORMANCE OF DOUBLE TUBE BUCKLING RESTRAINED BRACE WITH CAST STEEL CONNECTORS. The Hong Kong Institute of Steel Construction, March 2022. http://dx.doi.org/10.18057/ijasc.2022.18.1.2.
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The special concentrically braced frame (SCBF) is an aseismic structure, but its bracing system exhibits brittle failure and premature buckling connected with the weld fracture of the gusset plate and the post-buckling of the braces; thus, maximizing the role of energy dissipation is difficult. Here, this paper proposes a system of double-tube buckling-restrained brace with cast steel connectors for steel SCBFs. The large inelastic deformation of the bracing system is mainly concentrated in the ductile cast connectors under the earthquake, and the degree of buckling and post-buckling of braces can be reduced. Cyclic loading tests were conducted on two groups of specimens with different parameters, then the deformation trend, stress distribution, energy dissipation capacity, and stiffness degradation of the specimens were analyzed. The improved measures of increasing the width–thickness ratio of the energy dissipation plate and stiffener and casting the end right-angle tip tightly for a certain length of cast connector in Group 2 specimens, which overcomes the brittle fracture caused by the crack of the connection segment due to flexural buckling in Group 1 specimen tests, was evaluated. The cast steel connector conducts the main energy dissipation member that exhibits good ductile and energy absorption performance, and the advantages of using improved ductile cast steel connectors to obtain the energy dissipation of BRBs are illustrated. The test results provided direct evidence that the seismic performance of specimens is closely associated with the length of the energy dissipation segment of the cast connector and the overstrength factor of axial force. Also, the strength, rigidity, deformation, and energy dissipation performance of the members can be independently controlled by reasonably designing the cast connector. Our results provide the underlying insights needed to guide the design of the bracing connector.