Wyniki wyszukiwania - Biblioteka Nauki

1

Constitutive model for time-dependent ratchetting of SS304 stainless steel: simulation and its finite element analysis

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Jiang X. , Zhu Y. , Hong J. , Zhang Y. , Kan Q.

Journal of Theoretical and Applied Mechanics

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2013

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tom Vol. 51 nr 1

63--73

EN

Time-dependent ratchetting behaviour of SS304 stainless steel was experimentally conducted at room temperature and 973K. The material shows distinct time-dependent deformation. However, under cyclic stressing with a certain peak/valley stress hold and at 973K, more significant time-dependent inelastic behaviour was observed. Based on the Abdel-Karim-Ohno nonlinear kinematic hardening rule with the static recovery term, a time-dependent hardening rule incorporating an internal variable in the dynamic recovery term of the back stress is proposed to reasonably describe the evolution behaviour of time-dependent ratchetting with a certain peak/valley stress hold and at high temperature. Simultaneously, the proposed model is implemented into the ANSYS finite element package by User Programmable Features (UPFs). It is shown that the customized ANSYS model exhibits better performance than the reference model, especially under cyclic stressing with the certain peak/Valley stress hold and at high temperature.

PL

W pracy przedstawiono wyniki badań eksperymentalnych nad zależnym od czasu procesem zmęczeniowym typu ratcheting przeprowadzonych w temperaturze pokojowej oraz podwyższonej do 973K. Materiał wykazał wyraźnie zależną od czasu funkcję deformacji. Podczas cyklicznego obciążania przy zadanych wartościach min/max naprężeń w temperaturze 973K zaobserwowano silnie nieliniowe i zależne od czasu zachowanie się badanej stali. Do wyjaśnienia tego zjawiska, zwanego ratchetingiem zależnym od czasu, wykorzystano model umocnienia materiału oparty na nieliniowej formule kinematycznego umocnienia Abdela-Karima-Ohno ze statycznym członem odprężania. Model ten zmodyfikowano, wprowadzając wewnętrzną zmienną w dynamicznym członie odprężania przy obciążeniu powrotnym. Jednocześnie zaproponowany model wdrożono do systemu ANSYS poprzez zastosowanie pakietu User Programmable Features (UPFs). Wykazano, że taka modyfikacja systemu ANSYS charakteryzuje się lepszym działaniem w stosunku do standardowego oprogramowania. Jest to szczególnie zauważalne dla symulacji cyklicznego obciążenia stali w podwyższonej temperaturze.

2

Rock strength anisotropy in high stress conditions: a case study for application to shaft stability assessments

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Watson J. M. , Vakili M. , Jakubowski M.

Studia Geotechnica et Mechanica

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2015

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tom Vol. 37, nr 1

115--125

EN

Although rock strength anisotropy is a well-known phenomenon in rock mechanics, its impact on geotechnical design is often ignored or underestimated. This paper explores the concept of anisotropy in a high stress environment using an improved unified constitutive model (IUCM), which can account for more complex failure mechanisms. The IUCM is used to better understand the typical responses of anisotropic rocks to underground mining. This study applies the IUCM to a proposed rock shaft located in high stress/anisotropic conditions. Results suggest that the effect of rock strength anisotropy must be taken into consideration when assessing the rock mass response to mining in high stress and anisotropic rock conditions.

3

Modelling of material behaviour for Inconel 718 superalloy using experimental data

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Nieslony P. , Grzesik W. , Laskowski P.

Journal of Machine Engineering

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2017

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tom Vol. 17, No. 3

75--84

EN

In this paper parameters of the Johnson-Cook (J-C) constitutive material model were predicted more accurately based on the static and dynamic material tests and mathematical modelling of relevant response surfaces using specially developed Matlab scripts. Experimental tests were performed under strain rates of 10-3 and 101 1/s and the temperature ranging from the ambient up to 700°C. As a result, a set of mathematical models which fit the experimental data was determined. The experimentally-derived constitutive models were implemented into FEM-based simulations of real machining processes of Inconel 718.

4

Lifetime prediction in creep-fatigue environment

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Sabour M. H. , Bhat R. B.

Materials Science Poland

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2008

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tom Vol. 26, No. 3

563--584

EN

The creep-fatigue interaction has been studied and innovative mathematical models are proposed to predict the operating life of aircraft components, specifically gas turbine blades subject to creep-fatigue at high temperatures. The historical evolution of the creep-fatigue lifetime prediction is given in order to place the present study in the context. A literature review of the life estimation under creep-fatigue environment is presented.

5

Cyclic shear behavior of austenitic stainless

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Geijselaers B. , Bor T. , Van Den Boogaard T.

Computer Methods in Materials Science

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2015

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tom Vol. 15, No.1

13--22

EN

An austenitic stainless steel has been subjected to large amplitude strain paths containing a strain reversal. During the tests, apart from the stress and the strain also magnetic induction was measured to monitor the transformation of austenitc to martensite. From the in-situ magnetic induction measurements an estimate of the stress partitioning among the phases is determined. When the strain path reversal is applied at low strains, a classical Bauschinger effect is observed. When the strain reversal is applied at higher strains, a higher flow stress is measured after the reversal compared to the flow stress before reversal. Also a stagnation of the transformation is observed, meaning that a higher strain as well as a higher stress than before the strain path change is required to restart the transformation after reversal. The observed behavior can be explained by a model in which for the martensitic transformation a stress induced transformation model is used. The constitutive behavior of both the austenite phase and the martensite is described by a Chaboche model to account for the Bauschinger effect. In the model mean-field homogenization of the material behavior of the individual phases is employed to obtain a constitutive behavior of the two-phase composite. The overall applied stress, the stress in the martensite phase and the observed transformation behavior during cyclic shear are very well reproduced by the model simulations.

PL

Próbki z austenitycznej stali nierdzewnej poddawano od-kształceniom o dużej amplitudzie i przeciwnych zwrotach. W przeprowadzonych doświadczeniach, poza pomiarem naprężenia i odkształcenia, mierzono również indukcję magnetyczną do monitorowania przemiany austenitu w martenzyt. Dzięki bezpośrednim pomiarom indukcji magnetycznej możliwe było oszacowanie wielkości naprężenia w poszczególnych fazach materiału. Przy małych odkształceniach, dla przeciwnego zwrotu, obserwowany jest klasyczny efekt Bauschingera. Gdy dokonywana jest zmiana zwrotu przy większych odkształceniach, mierzone naprężenie jest większe niż przed zmianą. Obserwowana jest również stagnacja przemiany fazowej, to znaczy, że potrzebne jest wyższe odkształcenie i naprężenie niż przed zmianą ścieżki odkształcania aby ponownie zaczęła się przemiana po zmianie. Zaobserwowane zachowanie można opisać modelem, w którym dla przemiany martenzytycznej ma zastosowanie model naprężenia indukowanego przemianą. Zachowanie konstytutywne austenitu i martenzytu zostało opisane modelem Chaboche'a uwzględniającym efekt Bauschingera. W modelu wykorzystano metodę homogenizacji dla opisu materiału i faz, otrzymując konstytutywny model zachowania się dwu-fazowego kompozytu. Przyłożone naprężenie, naprężenie w fazie martenzytu i obserwowane zachowanie się podczas przemiany w trakcie cyklicznego ścinania zostało bardzo dobrze odtworzone w symulacjach modelu.

6

Building a numerical model for bulk materials from standard shear test data

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Feise H. , Daiss A.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2003

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tom Vol. 7, No 4

539-547

EN

While numerical methods have become an integral part of everyday work in process engineering for fluid processes, there is a curious lack of such methods in the field of solid handling. One of the reasons may be the inability of the most often used CFD codes to handle bulk solids. In the paper an attempt is made to show how the behaviour of bulk solids can be modelled using a CFD code without a specific constitutive model for bulk solids. Another reason for not using numerical tools to handle bulk materials is the difficulty of generating the necessary material parameters. Those material models suitable for bulk solids that are available in commercial packages are mostly derived from soil mechanics. Their parameters are determined using a triaxial cell. This device is generally not available in the chemical industries and most often not suitable for bulk solids, due to the high stress levels applied in those tests. In the paper a method is presented which allows the use of standard shear test data, supplemented by data from a compression tests in a "lambda-meter", to determine the parameters of an extended Drucker-Prager model with a compressive yield cap. Model equations are given and parameters are determined for white polymer powder. With these parameters a simulation of silo discharge has been performed successfully using a CFD code. To make CFD codes, which already have the much-needed multi-phase capability, capable of handling bulk solid flow, significant work remains to be done (e.g. shear stresses at rest and anisotropic stress tensors).

7

Calibration of Visco-Hyperelastic Model for Tensile Behavior of Porcine Skin

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Shin H. , Han D. , Kim S. , Rhim S.

Archives of Metallurgy and Materials

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2019

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tom Vol. 64, iss. 3

819--822

EN

Uniaxial tensile tests were performed on porcine skin to investigate the tensile stress-strain constitutive characteristic at qua-sistatic deformations using uniaxial tensile tests. Experimental results were then used to determine the parameters of the various constitutive model types for rubber, including the Mooney-Rivlin, Yeoh, Ogden, and others. The Prony series viscoelastic model was also calibrated based on the stress relaxation test. To investigate the calibrated constitutive equations (visco-hyperelastic), the falling impact test was conducted. From the viewpoint of the maximum impact load, the error was approximately 15.87%. Overall, the Ogden model predicted the experimental measurements most reasonably. The calibrated constitutive model is expected to be of practical use in describing the mechanical properties of porcine skin.

8

The elasto- viscoplastic Chaboche model

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Ambroziak A. , Kłosowski P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2006

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tom Vol. 10, No 1

49-61

EN

The elasto-viseoplastie constitutive equations of the Chaboehe model [I] have been developed and modified many times. The aim of the present paper is to present the existing Chaboche model variants and describe its scientific and engineering applications. A compact review of literature on these applications is given, focussed on publications offering a wider and more comprehensive view of the elasto-viscoplastic Chaboche model. The article is an introduction to a comprehensive investigation of the elasto-viscoplastic Chaboche model.

9

Numerical test on polystyrene tunnel seismic-isolation material

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He J. , Chen W. , Zhao W. , Huang S. , Yao Y.

Polish Journal of Chemical Technology

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2016

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tom Vol. 18, nr 3

122--127

EN

Stress-strain mechanical properties of polystyrene foam plastic material were tested under different loading conditions. An empirical constitutive model for describing metal materials was proposed for the polystyrene plastic foam. The static and dynamic tests results show that the ductility and watertightness of the polystyrene plastic foam are significantly improved. At the same time, in order to check its seismic-isolation property, the high-performance foam concrete as filling materials of Galongla tunnel in Tibet was simulated by FEM. The simulated results show that the polystyrene plastic foam can remarkably decrease the stress and the plastic zone in final lining, so it can effectively reduce the seismic damage of the tunnel. Considering the seismic-isolation property and low price of polystyrene plastic foam, it is a good reference for the anti-seismic design of tunnels in high intensity zones.

10

Effect of cyclic hardening on stress relaxation in SUS316HTP under creep-fatigue loading at 700ºC: experiments and simulations nobutada

88%

Ohno N. , Sasaki T. , Shimada T. , Tokuda K. , Yoshida K. , Okumura D.

Journal of Theoretical and Applied Mechanics

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2018

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tom Vol. 56 nr 2

497--510

EN

Cyclic hardening and stress relaxation experiments of SUS316HTP were performed under creep-fatigue loading with tensile strain holding at 700ºC. Experiments revealed that under strain holding, the slow stress-relaxation stage satisfying Norton’s law with slight cyclic hardening followed a rapid stress-relaxation stage that was noticeably affected by cyclic hardening. This suggests that in the slow stress-relaxation stage, inelastic deformation mechanisms different from that of viscoplasticity occurred. Experiments were simulated using a cyclic viscoplastic-creep model in which the inelastic strain-rate was decomposed into viscoplastic and creep components that were affected differently by cyclic hardening. The simulation accurately reproduced the experiments.

11

An elastoplastic constitutive model for assessing ground settlements induced by deep excavations

88%

El-Arja H. , Burlon S. , Bourgeois E.

Studia Geotechnica et Mechanica

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2023

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tom Vol. 45, nr 3

231--245

EN

Ground movements induced by deep excavations may cause damages on neighboring existing buildings. Finite element simulations generally give acceptable estimates of the horizontal displacements of the retaining wall, but results are less satisfactory for the vertical displacements of the ground surface behind the structure. A possible explanation is that most constitutive models describe volumetric strains in a simplified way. This paper proposes an elastoplastic constitutive model aimed at improving the prediction of vertical displacements behind retaining walls. The model comprises a single plastic mechanism with isotropic strain hardening, but has a specific flow rule that allows to generate contractive plastic strains. Identification of the parameters based on triaxial tests is explained and illustrated by an example of calibration. A numerical analysis of a well-documented sheet pile wall in sand in Hochstetten (Germany) is presented. The results given by the model are compared with the measurements and with those obtained using the Hardening Soil Model. The potential advantages of the proposed model are then discussed.

12

Identyfikacja parametrów materiałowych modelu Chaboche'a na podstawie wyników eksperymentów reologicznych

88%

Zalewski R. , Bajkowski J.

Modelowanie Inżynierskie

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2007

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tom T. 2, nr 33

167-174

PL

Tematyka pracy poświęcona jest omówieniu metody estymacji parametrów materiałowych wybranego lepkoplastycznego modelu konstytutywnego. Pomimo faktu, że obiektem modelowania są struktury, zbudowane z luźnego materiału sypkiego, otoczonego zamkniętą plastomerową osnową, w której wytwarzane jest podciśnienie zewnętrzne, prezentowana metoda identyfikacji modelu jest uniwersalna.

EN

Procedure of material constants values estimation, taking into consideration results of rheological tests, without the necessity of carrying out more complex experiments, will be the topic of the paper.

13

A Pressure-Dependent Plasticity Model for Polymer Bonded Explosives under Confined Conditions

88%

Wei Q. , Huang X.-c. , Chen P.-w. , Liu R.

Central European Journal of Energetic Materials

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2021

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tom Vol. 18, no. 3

339--368

EN

The safety of explosives is closely related to the stress state of the explosives. Under some stress stimulation, explosives may detonate abnormally. It is of great significance to accurately describe the mechanical response of explosives for the safety evaluation of explosives. The mechanical properties of polymer bonded explosives (PBXs) strongly depend on pressure. In this study, the mechanical behaviour of PBXs under confined conditions was investigated. It was found that the stress-plastic strain response of a PBX under high confining pressures is a combination of the non-linear and linear hardening portions. However, the linear hardening portion has often been neglected in characterizing the mechanical behaviour of a PBX under such pressures. The Karagozian and Case (K&C) model was applied to characterize the mechanical behaviour of PBXs. The numerical results demonstrated that when the confining pressure was high, the K&C model could not adequately match the experimental data due to the limitation of the damage model. Therefore, a new damage model was developed by means of considering intragranular damage and transgranular damage. This modification made it possible to introduce a linear hardening process into the original K&C model. The method proposed to describe the stress-strain results under high confining pressures was to consider the stress-plastic strain curve, including the nonlinear and linear hardening portions. The damage evolution of the original K&C model and a linear hardening model were applied for the nonlinear and linear hardening portions respectively. The influence of the linear hardening model on the damage evolution of the original K&C model was included when describing the nonlinear hardening portion. A comparison between simulation and experiment showed that the modified K&C model could well describe the mechanical response of PBXs under different confining pressures.

14

88%

Jankowski K. , Pawlikowski M. , Barcz K.

Acta of Bioengineering and Biomechanics

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2022

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tom Vol. 24, no. 3

169--177

EN

The aim of this research was to verify to what extent the shape of an indenter tip influences the final form of the constitutive equation for the trabecular bone. Methods: Trabecular bone was formulated as a non-linear viscoelastic material with Mooney–Rivlin hyperelastic model to describe the purely elastic response of the bone tissue. Tests of the mechanical properties of the trabecular bone, resected from the femoral head of a 56-year-old patient, were carried out with two types of indenter: the spherical tip of a diameter of 200 μm and pyramid Vickers tip with 136° between plane faces. Tests with both indenters included loading and unloading phases with no hold at peak force and with hold time t = 20 s and were conducted with a maximum load Pmax = 500 mN and loading/unloading rate V = 500 mN/min. Results: The formulated constitutive model describes the trabecula behaviour very well. The model curves match the experimental results in the loading phase, holding period and most of the unloading ramp. The purely viscoelastic material constants are very close in value for both considered tips, but purely elastic constants differ. Conclusions: The results indicate that the constitutive model based on the indentation with the Vickers tip does not cover the plastic residual deformation. When a viscoelastic response of bone is expected, a model with constants calibrated for the spherical tip should be used, and the other set of parameters values (Vickers tip) when trabeculae may undergo plastic deformation.

15

New constitutive model based on disturbed state concept for shear deformation of rock joints

75%

Xie S. , Lin H. , Chen Y.

Archives of Civil and Mechanical Engineering

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2023

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tom Vol. 23, no. 1

art. no. e26, 2023

EN

The mechanical behavior and constitutive relation of rock joints have caught more and more attention in the field of geotechnical engineering. The disturbed state concept (DSC) theory offers a powerful tool for building a constitutive model to interpret the mechanical response of geomaterials. In this paper, a new constitutive model for joint shear deformation was developed based on the DSC theory. The characteristics of quasi-elastic phase, pre-peak hardening phase, peak shear strength, post-peak softening phase and residual strength during the whole process of joint shear deformation are considered in this model. In the framework of this shear constitutive model, the rock material was assumed to consist of two kinds of micro-units with different mechanical responses, namely the relatively intact unit and the fully adjusted unit. Subsequently, the DSC theory was used to connect the mechanical behavior of micro-units with the macroscopic joint shear deformation characteristics, and a disturbance factor was introduced to reveal the disturbed state evolution process inside the rock. In addition, the proposed DSC model was simple in form, less in parameters and reasonable in physical meaning. The model was cross-validated by experimental data of different kinds of natural joints and artificial joint replicas. Finally, the model is compared with existing models, and the model effectiveness is quantitatively evaluated through statistical indicators. The values of R2 are greater than 0.9, and the AAREP and RMSE of the proposed DSC model are closer to 0 than those of other models. The research results can provide a valuable reference for further understanding of shear deformation mechanism.

16

Investigation of the biomechanical behaviour of articular cartilage in hindfoot joints

75%

Venturanto C. , Pavan P. G. , Forestiero A. , Carniel E. L. , Natali A. N.

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2014

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tom Vol. 16, no. 2

57--65

EN

Numerical models represent a powerful tool for investigating the biomechanical behavior of articular cartilages, in particular in the case of complex conformation of anatomical site. In the literature, there are complex non-linear-multiphase models for investigating the mechanical response of articular cartilages, but seldom implemented for the analysis of high organized structure such as the foot. In the present work, the biomechanical behavior of foot cartilage is investigated by means of a fiber-reinforced hyperelastic constitutive model. The constitutive parameters are obtained through the comparison between in vitro experimental indentation tests on cartilage and numerical analysis data interpreting the specific experimental conditions. A finite element model of the hindfoot region is developed. Particular attention is paid to model cartilage in order to respect its morphometric configuration, including also the synovial capsule. The reliability of the procedure adopted is evaluated by comparing the numerical response of tibio-talar joint model with in vivo experimental tests mimicking the foot response in stance configuration.

17

Model konstytutywny materiału SMA z lockingiem

75%

Grzesikiewicz W. , Wakulicz A. , Zbiciak A.

Modelowanie Inżynierskie

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2009

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tom T. 6, nr 37

105-110

PL

W pracy podano różniczkowy opisu związków konstytutywnych materiału SMA z lockingiem na podstawie zaproponowanego, oryginalnego schematu Teologicznego. Wykorzystano relacje konstytutywne idealnego stopu SMA sformułowane we wcześniejszych pracach autorów, modyfikując schemat reologiczny poprzez dodanie elementu blokującego odkształcenia. Opisano szczegółowo metodę wyznaczenia tensora prędkości odkształceń niesprężystych.

EN

The objective of the paper was to present the matheniatical description of constitutive properties of the SMA material with complete martensitic transformation. The rheological model possessing elastic, plastic, pseudoelastic and locking elements was proposed. The key problem being discussed herein was to evaluate the ratę of non-elastic strain. The constitutive relationships being obtained in the paper may be used for initial-boundary value problems analysis using FEM software.

18

Modelowanie numeryczne badania TSRST w celu określenia przydatności wybranych modeli konstytutywnych

75%

Gajewski M. , Mirski K. , Bańkowski W.

Logistyka

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2014

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tom nr 3

1893--1902

PL

W pracy analizowany jest test skrępowanego skurczu następującego w wyniku obniżania temperatury. Badanie to pozwala na określenie odporności na pękanie niskotemperaturowe mieszanek mineralnoasfaltowych, stąd jego prawidłowa interpretacja w świetle ostatnich problemów z nawierzchniami drogowymi w Polsce jest szczególnie interesująca. Badanie to jest modelowane przy zastosowaniu metody elementów skończonych i rozwiązywane jako zadanie termo-mechaniki z tzw. słabym sprzężeniem efektów termicznych i mechanicznych. Mechaniczne właściwości są uwzględnione poprzez relacje konstytutywne sprężystości, lepkosprężystości i sprężysto-plastyczności. Jako, że mieszanki mineralno-asfaltowe są materiałami, których właściwości mechaniczne i termiczne w sposób istotny zależą od temperatury to na podstawie uzyskanych wyników można zauważyć, że ich precyzyjne określenie jest warunkiem koniecznym do racjonalnego przewidywania ich zachowania przy zmiennej temperaturze.

EN

In the paper we analyze the Thermal Stress Restrained Specimen Test in which the shrinkage proceeds due to temperature reduction . This test allows to determine the low-temperature cracking resistance of asphalt mixes, hence its correct interpretation in the light of the recent problems with road pavements in Poland is particularly interesting . This study is devoted to modeling of the TSRST test using the finite element method in a frame of thermo - mechanics with the so-called weak coupling between thermal and mechanical effects. Mechanical properties are taken into account by the constitutive relations of elasticity, visco- elasticity and elasto- plasticity. As the asphalt mixtures are materials whose mechanical and thermal properties significantly depend on the temperature then on the basis of the obtained results it can be concluded, that its precise determination is a prerequisite for the rational prediction of road pavement behavior at low service temperatures.

19

Study on nonlinear constitutive model of skin under compression load over a wide range of strain rates

75%

Zhang X. , Wen C. , Tang C. , Liu S. , Wen Y. , Wang Y. , Bao Z. , Luo S.

Acta of Bioengineering and Biomechanics

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2021

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tom Vol. 23, no. 4

161--171

EN

Purpose: In wound ballistics, skin has obvious blocking effect in the biological target penetration of projectiles. An analytical description of skin mechanical properties under compression can set the basis for the numerical simulation and the evaluation of blocking effect. Methods: In this study, an improved three-parameter solid visco-elastic model was proposed to describe the skin creep phenomenon. And then combined with Maxwell and Ogden model, a new nonlinear skin constitutive model, consisting of hyper-elastic unit, creep unit and relaxation unit in parallel, was established. Here, we examine the material properties of freshly harvested porcine skin in compression at strain rates from 0.01/s to 4000/s. Results: The model is verified by comparison with the experimental results by our test and that in the literature at different strain rates. Conclusions: It shows that calculated results of the constitutive model agree well with the experiment data at extremely low to high strain rates, which is useful for the description of the heterogeneous, nonlinear viscoelastic, relaxation and creep mechanical response of skin under compression.

20

Propagation of temperature waves in rigid conductors with a plain periodic structure

75%

Piwowarski M.

Vibrations in Physical Systems

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2004

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tom Vol. 21

307--310