Academic literature on the topic 'Stress invariants'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Stress invariants.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Stress invariants"
1
Sadegh, A. M., and S. C. Cowin. "The Proportional Anisotropic Elastic Invariants." Journal of Applied Mechanics 58, no. 1 (March 1, 1991): 50–57. http://dx.doi.org/10.1115/1.2897178.
Full textAbstract:
There are two proportional invariants for a linear isotropic material, the hydrostatic invariant, and the deviatoric invariant. The former is proportional to the trace of the tensor and the latter is proportional to the trace of the square of the associated deviatoric tensor. The hydrostatic stress and strain and the von Mises stress and strain are directly related to the hydrostatic and deviatoric proportional invariants, respectively, for an isotropic, linear elastic material. For each anisotropic linear elastic material symmetry there are up to six proportional invariants. In this paper we illustrate the six proportional invariants of an orthotropic elastic material using the elastic constants for spruce as the numerical example. The proportional elastic invariants play a role in anisotropic linear elasticity similar to the roles played by the hydrostatic stress and strain and the von Mises stress and strain in isotropic elasticity. They are the unique parameters whose contours represent both the stress and the strain distributions. They also have potential for representing failure or fracture criteria.
2
Schajer, G. S. "Mohr-Coulomb Failure Criterion Expressed in Terms of Stress Invariants." Journal of Applied Mechanics 65, no. 4 (December 1, 1998): 1066–68. http://dx.doi.org/10.1115/1.2791905.
Full textAbstract:
A polynomial expression for the Mohr-Coulomb criterion for failure of brittle or frictional materials in terms of stress invariants is derived. The form of the polynomial expression corresponds to the pyramidal shape of the failure surface in principal stress space. The pressure-sensitive character of the failure of a Mohr-Coulomb material is indicated by a linear influence of the first stress invariant I1 in the polynomial expression.
3
Kuznetsov, V. V. "Thin-shell stress-strain state invariants." Strength of Materials 26, no. 8 (August 1994): 598–603. http://dx.doi.org/10.1007/bf02209434.
Full text
4
Pejkowski, Łukasz, and Dariusz Skibicki. "Multiaxial Fatigue Life Assessment Method Based on the Mean Value of Modified Second Invariant of the Deviatoric Stress." Solid State Phenomena 224 (November 2014): 15–20. http://dx.doi.org/10.4028/www.scientific.net/ssp.224.15.
Full textAbstract:
Stress invariants approach to the multiaxial fatigue life estimation is generally based on the root mean square value of second invariant of the deviatoric stress amplitude and the value of hydrostatic stress. Such an approach omits a significant part of the information about multiaxial load history. It is particularly noticeable in case of non-proportional loadings, which lead to a reduction of fatigue life (i.e. [1–3]). In this work a new method based on the mean value of modified second invariant of the deviatoric stress has been presented.
5
Yang, Qiang, Xin Chen, and Wei-Yuan Zhou. "Microplane-damage-based Effective Stress and Invariants." International Journal of Damage Mechanics 14, no. 2 (April 2005): 179–91. http://dx.doi.org/10.1177/1056789505048602.
Full text
6
Murti, V., W. Zhang, and S. Valliappan. "Stress invariants in an orthotropic damage space." Engineering Fracture Mechanics 40, no. 6 (January 1991): 985–90. http://dx.doi.org/10.1016/0013-7944(91)90164-v.
Full text
7
Iyer, Saiganesh K., and Cliff J. Lissenden. "Inelastic Anisotropy of Inconel 718: Experiments and Mathematical Representation." Journal of Engineering Materials and Technology 122, no. 3 (March 15, 2000): 321–26. http://dx.doi.org/10.1115/1.482804.
Full textAbstract:
A generalized threshold function for viscoplastic materials, which can also serve as a yield function in rate-independent plasticity, is suggested for materials that exhibit a strength differential and/or a permanent volume change. The motivation for this type of a threshold function is that experiments, at both 25 and 650°C, on the nickel-based alloy Inconel 718 indicate that higher stresses occur in compression than in tension. Similar results have been obtained for martensitic steels and other metallic alloys at 25°C. A general approach for determining the inelastic flow dependence on each of the three stress invariants (I1,J2, and J3) is to follow stress paths where only one invariant is changing. Two classical experiments that do this are hydrostatic pressure and pure torsion, however many others are possible. Unfortunately, these stress paths generally require three-dimensional stress states, which are difficult to obtain in the laboratory. Thus, for experimental expediency, tests involving axial-torsional loading of thin-walled tubes can be used to determine the significance of the first and third stress invariants, I1 and J3, respectively. [S0094-4289(00)01303-7]
8
Haoyun, Liang. "On the stationary behaviour of the stress invariants." Mechanics Research Communications 13, no. 4 (July 1986): 203–7. http://dx.doi.org/10.1016/0093-6413(86)90020-0.
Full text
9
ZHANG, TINGTING, XIAOSHENG GAO, BRYAN A. WEBLER, BRIAN V. COCKERAM, MATTHEW HAYDEN, and STEPHEN M. GRAHAM. "APPLICATION OF THE PLASTICITY MODELS THAT INVOLVE THREE STRESS INVARIANTS." International Journal of Applied Mechanics 04, no. 02 (June 2012): 1250021. http://dx.doi.org/10.1142/s1758825112500214.
Full textAbstract:
Increasing experimental evidence shows that the classical J2 plasticity theory may not fully describe the plastic response of many materials, including some metallic alloys. In this paper, the effect of stress state on plasticity and the general forms of the yield function and flow potential for isotropic materials are assumed to be functions of the first invariant of the stress tensor (I1) and the second and third invariants of the deviatoric stress tensor (J2 and J3). A 5083 aluminum alloy, Nitronic 40 (a stainless steel), and Zircaloy-4 (a zirconium alloy) were tested under tension, compression, torsion, combined torsion–tension and combined torsion–compression at room temperature to demonstrate the applicability of a proposed I1-J2-J3 dependent model. The I1-J2-J3 dependent plasticity model was implemented in ABAQUS via a user defined subroutine. The model parameters were determined and validated by comparing the numerically predicted and experimentally measured load versus displacement and/or torque versus twist angle curves. The results showed that the proposed model incorporating the I1-J2-J3 dependence produced output that matched experimental data more closely than the classical J2 plasticity theory for the loading conditions and materials tested.
10
Shariff, Mohd Halim Bin Mohd, and Jose Merodio. "Residually Stressed Fiber Reinforced Solids: A Spectral Approach." Materials 13, no. 18 (September 14, 2020): 4076. http://dx.doi.org/10.3390/ma13184076.
Full textAbstract:
We use a spectral approach to model residually stressed elastic solids that can be applied to carbon fiber reinforced solids with a preferred direction; since the spectral formulation is more general than the classical-invariant formulation, it facilitates the search for an adequate constitutive equation for these solids. The constitutive equation is governed by spectral invariants, where each of them has a direct meaning, and are functions of the preferred direction, the residual stress tensor and the right stretch tensor. Invariants that have a transparent interpretation are useful in assisting the construction of a stringent experiment to seek a specific form of strain energy function. A separable nonlinear (finite strain) strain energy function containing single-variable functions is postulated and the associated infinitesimal strain energy function is straightforwardly obtained from its finite strain counterpart. We prove that only 11 invariants are independent. Some illustrative boundary value calculations are given. The proposed strain energy function can be simply transformed to admit the mechanical influence of compressed fibers to be partially or fully excluded.
Dissertations / Theses on the topic "Stress invariants"
1
Zhang, Tingting. "Development of Plasticity and Ductile Fracture Models Involving Three Stress Invariants." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1334113425.
Full text
2
Leibo, Joel Zaidspiner. "The invariance hypothesis and the ventral stream." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87458.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Brain and Cognitive Sciences, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 122-138).
The invariance hypothesis is the claim that properties of the ventral stream can be deduced from 1. a consideration of the computational problem with which it is engaged: invariant object recognition, 2. constraints of the neural "hardare", and 3. the visual environment. We are interested here in a particular instantiation of this idea. A recent general theory of hierarchical networks for invariant recognition [1] describes many modern convolutional networks as special cases, and also implies the existence of a wider class of algorithms, which we are only now beginning to explore. Our version of the invariance hypothesis is the claim that the algorithm implemented by the ventral stream is also in this class. As applied to the brain, the theory follows from a few simple and commonly accepted premises. This thesis contributes several models/studies in which properties of the ventral stream are deduced and explained in the context of the theory. The main contribution here is providing a general framework through which disparate results concerning many parts of the ventral stream, and even different levels of analysis [2], can be bridged and understood. In that sense, it is primarily a Neuroscience contribution. However, the ideas and algorithms it suggests may also have implications for the broader question of how to learn representations capable of supporting intelligence.
by Joel Zaidspiner Leibo.
Ph. D.
3
Bedford, Lee. "Measurement Invariance of a Posttraumatic Stress Disorder Symptoms Measure (PCL-5) in College Student and Amazon's Mechanical Turk Samples." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1707346/.
Full textAbstract:
College student and Amazon's Mechanical TURK (MTURK) samples are regularly utilized in trauma research. Recent literature, however, has criticized these samples for not being generalizable to the general U.S. population. Measurement invariance (MI) using confirmatory factor analyses (CFA), is rarely utilized in trauma research, even though the analysis can determine whether groups are invariant across factor structure, factor loadings, item intercepts, and residual error variances on a given measure of PTSD symptom severity. The purpose of this study was to determine whether college student (n = 255) and MTURK (n = 316) samples are invariant on the PCL-5. Model fit indices indicated the 7-factor Hybrid model was the best fitting model, but the 6-factor anhedonia model was the most parsimonious model. Both models demonstrated equivalence in factor structures (configural invariance), factor loadings (metric invariance), intercepts (scalar invariance), and residuals (strict invariance), indicating MTURK and college student samples are similar in regards to PTSD symptom severity. These findings provide evidence that these groups can be combined in future studies to increase sample size for trauma research. Only the Anhedonia factor exhibited mean differences between groups, which may be related to true differences between college students and MTURK survey-takers. Thus, there is further evidence that the findings from trauma studies using these populations are generalizable to each other.
4
Langenbruch, Cornelius [Verfasser]. "The Role of Stress Fluctuations in Seismogenic Processes : Fluid injection-induced earthquakes and scale invariance / Cornelius Langenbruch." Berlin : Freie Universität Berlin, 2014. http://d-nb.info/1054637040/34.
Full text
5
Davis, Samantha. "The measurement invariance and measurement equivalence of the sources of work stress inventory (SWSI) across gender groups in South Africa." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95741.
Full textAbstract:
Thesis (MCom)--Stellenbosch University, 2014.You will be needing the program SPSS in order to read the .spv files
ENGLISH ABSTRACT: The primary goal of an organisation, in a capitalistic system, is the maximisation of profit. The task of the human resource function in organisations is to affect the work performance of working man to the advantage of the organisation and in a manner that adds value to the organisation. The management of employee wellbeing/psychological health is one of the human resource interventions with which the human resource function pursues this objective. It is imperative for organisations to be aware of, and sensitive to, negative factors in the workplace, such as occupational stress, that influence employees’ health and wellbeing and have a significant effect on job satisfaction and performance (Hamidi & Eivazi, 2010). Prevailing stress levels need to be monitored regularly if escalating stress levels are to be detected in time to prevent serious personal and organisational problems from developing. The Sources of Work Stress Inventory (SWSI) is an instrument developed in South Africa specifically for this purpose (De Bruin & Taylor, 2005). The inappropriate use of occupational stress assessments across genders can seriously jeopardize the extent to which occupational stress assessments, and the decisions based on them, achieve their intended objectives. In order to avoid making widespread generalisations and untested assumptions which will eventually do a disservice to the field of psychology, the absence of measurement bias (i.e. invariance and equivalence) should be demonstrated instead of simply assumed (Van de Vijver & Tanzer, 2004). Establishing the measurement invariance and equivalence of an instrument across groups should be a prerequisite to conducting substantive cross-group comparisons (Dunbar, Theron & Spangenberg, 2011). It is imperative to empirically ascertain whether the instruments that are used are free of cultural, language, gender, age and racial bias, not only because it is prohibited by the Employment Equity Act 55 of 1998, but also as it is in the interest of good workmanship. Bias is indicated as nuisance factors that threaten the validity of cross-group (cultural) comparisons (Van de Vijver & Leung, 1997). These nuisance factors could be due to construct bias, method bias and/or item bias. Due to the importance of the decisions made, it would seem essential that the information provided by test results apply equally across different reference groups. In this study the specific measurement invariance and equivalence sequence of tests set out by Dunbar et al. (2011) was used to answer a sequence of research questions that examine the extent to which the SWSI multi-group measurement model may be considered measurement invariant and equivalent or not, and to determine the source of variance if it existed (Vandenberg & Lance, 2000). Upon investigating the measurement model fit of the SWSI, the results indicated that support was found for the hypotheses that the measurement model fits the data of both gender samples independently. Furthermore, support was found for the configural and weak invariance model. However, due to not meeting the requirements for metric equivalence, partial measurement invariance and equivalence was explored. The SWSI multi-group measurement model met the requirements of partial complete invariance and partial full equivalence, and the non-invariant items were identified in the process. The implications of the results are discussed, limitations are indicated and areas for further research are highlighted.
AFRIKAANSE OPSOMMING: Die kerndoelwit van enige organisasie, veral in ‘n kapitalistiese stelsel, is om optimale wins te genereer. Die taak van die menslike hulpbronbestuurfunksie binne organisasies is om die werksverrigting van die werkende mens te beïnvloed tot voordeel van die organisasie en terselfdetyd waarde tot die organisasie toe te voeg. Die bestuur van ‘n werknemer se welstand / sielkundige gesondheid is een van die menslike hulpbron-iintervensies waarmee die menslike hulpbronfunksie hierdie doelwit nastreef. Dit is uiters belangrik vir organisasies om bewus te wees van, asook sensitief te wees vir, negatiewe faktore soos werkstres, wat werknemers se gesondheid en welsyn beïnvloed en wat 'n beduidende invloed op werkstevredenheid en prestasie het (Hamidi & Eivazi, 2010). Heersende stresvlakke moet gereeld gemonitor word om tydig stygende stresvlakke te bespeur ten einde ernstige persoonlike en organisasieverwante probleme te verhoed. Die Bronne van die Werkstres-inventaris (BWSI) is in Suid-Afrika spesifiek vir hierdie doel ontwikkel (De Bruin & Taylor, 2005). Die ontoepaslike gebruik van werkstresmetings oor geslagte kan egter die mate waartoe beroepstresmetings en die besluite wat daarop gebaseer word hul oogmerke bereik ernstig benadeel. Die afwesigheid van metingsydigheid (bv. invariansie en ekwivalensie) moet dus empiries gedemonstreer word, in stede daarvan dat die afwesigheid daarvan eenvoudig aanvaar word (Van de Vijver & Tanzer, 2004). Die afwesigheid van hierdie informasie kan lei tot wydverspreide veralgemenings en ongetoetsde aannames wat die Sielkunde professie ernstige skade kan berokken. Die meetings-invariansie en -ekwivalensie van 'n instrument oor groepe is 'n voorvereiste vir substantiewe kruis-groepvergelykings (Dunbar, Theron & Spangenberg, 2011). Dit is noodsaaklik om empiries te bepaal of die instrumente wat gebruik is vry is van kulturele-, taal, geslag-, ouderdom- en rasse-sydigheid, nie net omdat dit verbied word deur die Wet op Diensbillikheid 55 van 1998 nie, maar ook omdat dit in die belang van goeie vakmanskap is. Sydigheid is sistermatiese steurnisse wat die geldigheid van die kruis-groep (kulturele) vergelykings (Van de Vijver & Leung, 1997) bedreig. Hierdie steurnisse kan wees as gevolg van konstruk-, metode- en/of itemsydigheid. Gegewe die belangrikheid van die besluite wat geneem word gebaseer op die metings is dit noodsaaklik dat die inligting vergelykbaar oor die verskillende verwysingsgroepe is. Die studie het die stel metingsinvariansie en -ekwivalensie toetse wat deur Dunbar et al. (2011) gebruik om 'n reeks van navorsingsvrae te beantwoord. Daar is ondersoek gestel na die mate waartoe die BWSI multi-groep metingsmodel as invariant of ekwivalent beskou kan word, en die bron van variansie te bepaal as dit sou bestaan (Vandenberg & Lance, 2000). In die ondersoek na die metingsmodel passing van die BWSI, is daar ondersteuning gevind is vir die hipoteses dat die metingsmodel beide van die geslagsteekproewe goed pas. Steun is ook gevind vir die konfigurale en swak invariansie modelle. Aangesien slegs beperkte steun vir metriese ekwivalensie gevind is, is ondersoek na die parsiële metriese invariansie en ekwivalensie ingestel. Die BWSI multi-groep metingsmodel het voldoen aan die vereistes van parsiële volledige invariansie en parsiële volle ekwivalensie, en die nie-invariante items is deur die proses geïdentifiseer. Die implikasies van die resultate word bespreek, beperkinge word aangedui en areas vir verdere navorsing word uitgelig.
6
Petrowski, Katja, Sören Kliem, Michael Sadler, Alicia E. Meuret, Thomas Ritz, and Elmar Brähler. "Factor structure and psychometric properties of the english version of the trier inventory for chronic stress (TICS-E)." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-234462.
Full textAbstract:
Background
Demands placed on individuals in occupational and social settings, as well as imbalances in personal traits and resources, can lead to chronic stress. The Trier Inventory for Chronic Stress (TICS) measures chronic stress while incorporating domain-specific aspects, and has been found to be a highly reliable and valid research tool. The aims of the present study were to confirm the German version TICS factorial structure in an English translation of the instrument (TICS-E) and to report its psychometric properties.
Methods
A random route sample of healthy participants (N = 483) aged 18–30 years completed the TICS-E. The robust maximum likelihood estimation with a mean-adjusted chi-square test statistic was applied due to the sample’s significant deviation from the multivariate normal distribution. Goodness of fit, absolute model fit, and relative model fit were assessed by means of the root mean square error of approximation (RMSEA), the Comparative Fit Index (CFI) and the Tucker Lewis Index (TLI).
Results
Reliability estimates (Cronbach’s α and adjusted split-half reliability) ranged from .84 to .92. Item-scale correlations ranged from .50 to .85. Measures of fit showed values of .052 for RMSEA (Cl = 0.50–.054) and .067 for SRMR for absolute model fit, and values of .846 (TLI) and .855 (CFI) for relative model-fit. Factor loadings ranged from .55 to .91.
Conclusion
The psychometric properties and factor structure of the TICS-E are comparable to the German version of the TICS. The instrument therefore meets quality standards for an adequate measurement of chronic stress.
7
Lucey, Patrick Joseph. "Lipreading across multiple views." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16676/.
Full textAbstract:
Visual information from a speaker's mouth region is known to improve automatic speech recognition (ASR) robustness, especially in the presence of acoustic noise. Currently, the vast majority of audio-visual ASR (AVASR) studies assume frontal images of the speaker's face, which is a rather restrictive human-computer interaction (HCI) scenario. The lack of research into AVASR across multiple views has been dictated by the lack of large corpora that contains varying pose/viewpoint speech data. Recently, research has concentrated on recognising human be- haviours within "meeting " or "lecture " type scenarios via "smart-rooms ". This has resulted in the collection of audio-visual speech data which allows for the recognition of visual speech from both frontal and non-frontal views to occur. Using this data, the main focus of this thesis was to investigate and develop various methods within the confines of a lipreading system which can recognise visual speech across multiple views. This reseach constitutes the first published work within the field which looks at this particular aspect of AVASR. The task of recognising visual speech from non-frontal views (i.e. profile) is in principle very similar to that of frontal views, requiring the lipreading system to initially locate and track the mouth region and subsequently extract visual features. However, this task is far more complicated than the frontal case, because the facial features required to locate and track the mouth lie in a much more limited spatial plane. Nevertheless, accurate mouth region tracking can be achieved by employing techniques similar to frontal facial feature localisation. Once the mouth region has been extracted, the same visual feature extraction process can take place to the frontal view. A novel contribution of this thesis, is to quantify the degradation in lipreading performance between the frontal and profile views. In addition to this, novel patch-based analysis of the various views is conducted, and as a result a novel multi-stream patch-based representation is formulated. Having a lipreading system which can recognise visual speech from both frontal and profile views is a novel contribution to the field of AVASR. How- ever, given both the frontal and profile viewpoints, this begs the question, is there any benefit of having the additional viewpoint? Another major contribution of this thesis, is an exploration of a novel multi-view lipreading system. This system shows that there does exist complimentary information in the additional viewpoint (possibly that of lip protrusion), with superior performance achieved in the multi-view system compared to the frontal-only system. Even though having a multi-view lipreading system which can recognise visual speech from both front and profile views is very beneficial, it can hardly considered to be realistic, as each particular viewpoint is dedicated to a single pose (i.e. front or profile). In an effort to make the lipreading system more realistic, a unified system based on a single camera was developed which enables a lipreading system to recognise visual speech from both frontal and profile poses. This is called pose-invariant lipreading. Pose-invariant lipreading can be performed on either stationary or continuous tasks. Methods which effectively normalise the various poses into a single pose were investigated for the stationary scenario and in another contribution of this thesis, an algorithm based on regularised linear regression was employed to project all the visual speech features into a uniform pose. This particular method is shown to be beneficial when the lipreading system was biased towards the dominant pose (i.e. frontal). The final contribution of this thesis is the formulation of a continuous pose-invariant lipreading system which contains a pose-estimator at the start of the visual front-end. This system highlights the complexity of developing such a system, as introducing more flexibility within the lipreading system invariability means the introduction of more error. All the works contained in this thesis present novel and innovative contributions to the field of AVASR, and hopefully this will aid in the future deployment of an AVASR system in realistic scenarios.
8
Brito, João. "Ductile fracture prediction using a coupled damage model." Master's thesis, 2018. http://hdl.handle.net/10316/80684.
Full textAbstract:
The growing complexity of the sheet metal formed products and the shortening of the development cycles has placed new challenges to this forming industry. In this context, it is well-known that the numerical simulation of the forming processes assumed a vital role to face up these challenges. In particular, the introduction of new materials with higher strength-to-weight ratio, and consequently reduced ductility, have sparked a growing interest on the development of reliable computational tools, able to accurately predict the onset of failure of ductile materials.
The main objective of this work is to evaluate the ability of a coupled micromechanical damage model – the so-called CPB06 porous model, to describe the damage accumulation and, ultimately, the onset of failure of ductile materials exhibiting tension-compression asymmetry (SD effects). The main features of the CPB06 porous model are investigated and the importance of the yield loci shape, through the role played by all stress invariants, on the damage evolution are highlighted.
Within this framework, a detail sensitivity analysis of the damage model is firstly performed based on the yield loci change of shape and size, when varying material and/or damage parameters. Both two-dimensional and three-dimensional representations of the yield surfaces are analysed. The influence of the stress state through the stress triaxiality, hydrostatic stress and the sign of the third invariant of the deviatoric stress tensor, particularly for axisymmetric loadings, is also studied. Next, a numerical analysis is carried out, based on single-element computations under axisymmetric and hydrostatic stress states, obeying the isotropic form of the CPB06 porous model. The applicability and reliability of the damage model is assessed by comparing the obtained results with the ones predicted by documented and well-accepted micromechanical finite element computations on three-dimensional unit cells. Additionally, the numerical tests are complemented with a brief sensitivity analysis regarding the matrix isotropic hardening law parameters. All numerical simulations are performed with the in-house finite element solver DD3IMP.
It is shown that, under tensile axisymmetric loadings, the damage model predicts two very distinct behaviours for the ductile damage evolution, whit regard to the sign of the third deviatoric stress invariant. For positive values of this invariant, the model is sensitive to the SD effects, in agreement with the behaviour predicted by the unit cell studies. Nonetheless, for negative values of this invariant the damage model is shown to be insensitive to the SD effects, which contrasts with the behaviour predicted by the same studies. It is concluded that the insensitivity to the SD effects for this particular stress state is due the homogeneous characteristics of the yield function, implying that the direction of the plastic strain increment, and eventually the damage accumulation, are independent of the tension-compression asymmetry displayed by the materials.A crescente complexidade dos componentes obtidos pelo processo de estampagem de chapas metálicas e a redução dos ciclos de desenvolvimento de novos produtos colocaram novos desafios a esta tecnologia de conformação. Neste contexto, a simulação numérica do processo de estampagem de chapas metálicas assumiu um papel notório para enfrentar estes desafios. Em particular, a introdução de materiais com maior relação resistência-peso e, consequentemente, menor ductilidade, despertou um interesse acrescido no desenvolvimento de ferramentas computacionais fiáveis e robustas, com capacidade para prever com precisão a ocorrência da rotura de materiais dúcteis. O principal objetivo deste trabalho é avaliar a capacidade de um modelo de dano micromecânico acoplado – o modelo poroso CPB06, para descrever a acumulação de dano e, eventualmente, o instante em que ocorre a falha mecânica de materiais dúcteis que exibem assimetria tração-compressão (efeitos SD). As principais características do modelo poroso CPB06 são investigadas e é destacada a importância da forma da superfície de elasticidade, através do papel desempenhado por todos os invariantes do tensor das tensões, na evolução do dano dúctil. Neste contexto, inicialmente é realizada uma análise de sensibilidade ao modelo, com base na alteração da forma e dimensão da superfície limite de elasticidade com a variação dos parâmetros materiais e/ou de dano. São analisadas representações tridimensionais e bidimensionais destas superfícies. A influência do estado de tensão caracterizado através da triaxialidade, da pressão hidrostática e do sinal do terceiro invariante do tensor desviador das tensões, particularmente para carregamentos axissimétricos, é igualmente estudada. De seguida, é realizada uma análise com base em simulações numéricas com um único elemento finito submetido a estados de tensão axissimétricos e hidrostáticos, obedecendo à forma isotrópica do modelo poroso CPB06. A aplicabilidade e fiabilidade do modelo de dano são avaliadas comparando os resultados obtidos com os previstos por estudos numéricos em células unitárias tridimensionais documentados na literatura. Os testes numéricos são complementados por uma análise de sensibilidade em relação aos parâmetros da lei de encruamento isotrópico da matriz. Todas as simulações numéricas são realizadas com o código de elementos finitos académico DD3IMP. A análise numérica mostra que, em carregamentos axissimétricos de tração, o modelo de dano prevê dois comportamentos bastante distintos para a evolução do dano dúctil, em função do sinal do terceiro invariante do tensor desviador das tensões. Para valores positivos deste invariante, o modelo é sensível aos efeitos SD, o que está de acordo com o comportamento previsto pelos estudos numéricos realizados com células unitárias. No entanto, para valores negativos deste invariante, o modelo de dano mostra-se insensível aos efeitos SD, o que contrasta com o comportamento previsto pelos mesmos estudos. Conclui-se que a insensibilidade aos efeitos SD para este estado de tensão é devida à homogeneidade da função que define a superfície limite de elasticidade do critério. Esta característica matemática da função implica que a direção do incremento de deformação plástica e, em última análise, a acumulação de dano, sejam independentes da assimetria tração-compressão exibida pela matriz dos materiais porosos.
9
Roux, David Johannes. "An assessment of the invariance of work-related well-being in selected South African sectors / David Johannes Roux." Thesis, 2013. http://hdl.handle.net/10394/10586.
Full textAbstract:
The current work environment demands a lot from employees. Organisations implement strategies to reduce cost and increase productivity, often ignoring the well-being and needs of employees. Factors such as virtual offices are becoming a reality as cell phones, laptops, tablets and other technology make availability a reality 24 hours a day. This leads to employees being confronted with work wherever and whenever it is required. These factors can lead to distress or eustress or both. Some employees experience symptoms of burnout due to all these demands placed on them, yet others experience eustress. Work well-being is crucial to ensure that employees are engaged and committed to their job and contribute to the success of the organisation they are employed with. In the model of work-related well-being of Nelson and Simmons (2003), which will be discussed in this research, burnout is regarded as distress, while work engagement is regarded as eustress.
The objective of this study is to determine whether a relationship exists between the dimensions of work-related well-being within selected sectors in South Africa – whether it leads to either burnout or work engagement and whether it is similar in different sectors. Various models can be used to explain these effects but for the purposes of this study the following models were consulted, namely the Comprehensive Model of Burnout and Engagement (COBE), the Effort-Recovery (E-R) Model and the Job Demand / Resources (JD-R) model.
The participants in this study are educators and administrative personnel from tertiary education institutions (n = 1324), secondary schools (n = 1177), employees from the insurance industry (n = 613), and correctional services (n = 892). The measurement vii
instruments used are the Maslach Burnout Inventory, the Utrecht Work Engagement Scale and the Job Demands-Resources Scale and the Organisational Stress Screening Tool (ASSET).
The results indicate that there is a relationship between the dimensions of work-related well-being in different sectors and that it has great predictive value in different sectors.MA (Industrial Psychology), North-West University, Potchefstroom Campus, 2013
10
Schoeman, Petrus Gerhardus. "Developing a measure of coping in high stress security occupations: a stress management model approach." Thesis, 2020. http://hdl.handle.net/10500/26852.
Full textAbstract:
Summaries in English, Afrikaans and ZuluOrientation: Security personnel work in a high risk and consequently high stress environment. This may negatively affect their wellbeing. Owing to the high crime rate in South Africa, one of the continuous stressors security personnel experience might be fearing for their lives. If security personnel fail to use effective coping strategies they will remain stressed, and this may have a negative impact on them, and their organisation or community. Challenges such as work stress in the South African security industry have not been comprehensively researched or documented (Sibanyoni, 2014). Consequently, no South African questionnaire measuring coping with stress or a stress management model for dealing with stress in a security environment, could be found. Research purpose: The general aim of the research was to develop a valid and reliable coping questionnaire and stress management model for high stress security occupations. Research methodology: A questionnaire development process, as suggested by scientific literature, was followed. The process entailed (1) determining coping strategies by means of a literature review, (2) developing the coping questionnaire, (3) administering the questionnaire to the target population, and (4) statistical analysis. The stress management model was developed by combining the results of the confirmatory factor analysis (CFA) and canonical correlation analysis (CCA). The development of the questionnaire was based on a sample of 381 active duty security personnel working in a high stress security environment in South Africa. Main findings: The study resulted in the development of a psychometrically sound 39-item questionnaire. The following 12 empirically validated healthy and unhealthy coping strategies were identified: (1) social support, (2) group cohesion, (3) physical exercise, (4) relaxation, (5) social media addiction, (6) healthy sleeping habits, (7) healthy diet, (8) training, (9) humour, (10) religion, (11) avoidance, and (12) denial. CFA confirmed both the construct and content validity, and composite reliability. The questionnaire was found to be invariant, and could thus be applied to different groups in high stress security occupations. A stress management model indicating the interrelationship between personality and coping was also developed. Contribution/value-add: The main contribution of this study was the development of a valid coping questionnaire and stress management model. By identifying the specific coping strategies, targeted stress management interventions could be developed. This could contribute to the overall wellness of security personnel working in high stress occupations, resulting in a healthy organisation and sound relationships with the community. Security organisations could also use the model during assessments to identify candidates with personality traits that would lead to healthier coping strategies, thereby selecting personnel that could better adapt to a security environment.
Oriëntasie: Sekuriteitspersoneel werk in ’n hoë risiko en gevolglik ’n stresvolle omgewing. Dit kan hulle welstand negatief beïnvloed. As gevolg van die hoë misdaadsyfer in Suid-Afrika kan een van die deurlopende stressors wat sekuriteitspersoneel ervaar ’n vrees vir hulle lewens wees. Indien sekuriteitspersoneel nie effektiewe streshantering strategieë gebruik nie, kan hulle voortdurend stres ervaar en dit kan ’n negatiewe impak op hulleself, hulle organisasie of gemeenskap hê. Uitdagings soos beroepstres in die Suid-Afrikaanse sekuriteitsindustrie is nog nie deeglik nagevors of gedokumenteer nie (Sibanyoni, 2014). Gevolglik kon daar vir die sekuriteitsomgewing geen Suid-Afrikaanse vraelys wat streshantering meet of ’n stresbestuursmodel gevind word nie. Doel van die navorsing: Die algemene doel van die navorsing was om vir stresvolle sekuriteitsberoepe ’n geldige en betroubare streshanteringsvraelys en stresbestuursmodel te ontwikkel. Navorsingsmetodologie: ’n Vraelys ontwikkelingsproses, soos deur wetenskaplike literatuur voorgestel, is gevolg. Die proses het die volgende behels: (1) die vasstel van die streshantering strategieë deur middel van ’n literatuuroorsig, (2) die ontwikkeling van die streshanteringsvraelys, (3) administrasie van die vraelys aan die teiken populasie en (4) statistiese analise. Die stresbestuursmodel is ontwikkel deur die resultate van die bevestigende faktoranalise (BFA) en die kanoniese korrelasie analise te kombineer. Die ontwikkeling van die vraelys is gebaseer op ’n steekproef van 381 aktiewe diens sekuriteitspersoneel wat in Suid-Afrika in ’n stresvolle sekuriteitsomgewing werk. Hoofbevindinge: Die studie het tot ’n psigometries betroubare 39-item vraelys gelei. Twaalf empiries gestaafde gesonde en ongesonde streshantering strategieë is geïdentifiseer naamlik: (1) sosiale ondersteuning, (2) groep kohesie, (3) fisiese oefening, (4) ontspanning, (5) sosiale media verslawing, (6) gesonde slaapgewoontes, (7) gesonde dieet, (8) opleiding, (9) humor, (10) godsdiens, (11) vermyding en (12) ontkenning. BFA het die konstruk- en inhoudsgeldigheid so wel as die saamgestelde betroubaarheid bevestig. Die vraelys is invariant en kan dus op verskillende groepe in hoë stres sekuriteitsberoepe toegepas word. ’n Stresbestuursmodel wat die verwantskap tussen persoonlikheid en streshantering aandui is ook ontwikkel. Bydrae/waardetoevoeging: Die belangrikste bydrae van hierdie studie was die ontwikkeling van ’n geldige streshanteringsvraelys en stresbestuursmodel. Deur die spesifieke streshantering strategieë te identifiseer kan gefokusde streshantering intervensies ontwikkel word. Dit kan tot die algehele welstand van sekuriteitspersoneel wat in stresvolle beroepe werk bydra en derhalwe ’n gesonde organisasie en goeie verhoudings met die gemeenskap. Sekuriteitsorganisasies kan ook tydens keurings die model gebruik om kandidate met persoonlikheidstrekke, wat tot gesonder streshantering strategieë sal lei, te identifiseer en dus personeel kies wat beter by ’n sekuriteitsomgewing sal aanpas.
Isimo somqondo: Abasebenzi bezokuphepha basebenza ezindaweni ezinobungozi obuphakeme nengcindezi ephakeme. Lokhu kungaba nomthelela omubi esimeni sabo sempilo. Ngenxa yezinga lobugebengu eliphezulu eNingizimu Afrika, okukodwa okudala ingcindezi ngokuqhubekayo kubasebenzi bezokuphepha ukwesabela izimpilo zabo. Uma abasebenzi bezokuphepha bengasebenzisi amasu aphumelelayo okubhekana nalezi zimo, bazohlala benengcindezi futhi lokhu kungaba nomphumela omubi kubona, enhlanganweni yabo noma emphakathini wabo. Ucwaningo ngezinselelo ezinjengokucindezeleka emsebenzini ezimbonini zokuphepha lapha eNingizimu Afrika alwenziwanga futhi akubhaliwe kabanzi ngakho (Sibanyoni, 2014). Kanjalo, alutholakalanga uhlu lwemibuzo lwaseNingizimu Afrika olungalinganisa ukuthi abasebenzi bezokuphepha babhekana kanjani nengcindezi kanye nomlinganiso olawula ingcindezi ukubhekana nengcindezi ezindaweni zezokuphepha. Inhloso yocwaningo: Inhloso enkulu yocwaningo kwakuwukuqamba uhlu lwemibuzo oluqinisekile noluthembekile ukubhekana nengcindezi nomlinganiso wokulawula ingcindezi emisebenzini yezokuphepha enengcindezi ephakeme. Indlela yokwenza ucwaningo: Isenzo sokuqamba uhlu lwemibuzo njengoba kuhlongozwa yimibhalo yezesayensi silandelwe kulolu cwaningo. Lesi senzo sibe (1) nokuthola amasu okubhekana nengcindezi ngokubhekisa emibhalweni ehloliwe, (2) nokuqamba uhlu lwemibuzo ephathelene nokubhekana nengcindezi, (3) nokunikeza uhlu lwemibuzo kubantu abathintekayo, kanye (4) nokwenza uhlaziyo lwezibalo. Umlinganiso wokulawula ingcindezi wenziwe ngokuhlanganisa imiphumela yeConfirmatory Factor Analysis (CFA) neyeCanonical Correlation Analysis (CCA). Ukuqanjwa kohlu lwemibuzo kweyeme esampuleni labasebenzi bezokuphepha abangama-381 abamatasa emsebenzini abasebenza ezindaweni ezinengcindezi ephakeme eNingizimu Afrika. Okukhulu okutholakele ocwaningweni: Ucwaningo lube nomphumela ekuqanjweni kohlu lwemibuzo oluqinisekile ngokwesayikhomethri olunemibuzo angama-39. Kukhonjwe amasu okubhekana nengcindezi ayishumi nambili aqinisekiswe ngokubukisiswa asesimeni esiphilile nesingaphilile sempilo, okubalwa kuwo, (1) uxhaso lomphakathi, (2) ukuba ndawonye kweqembu, (3) ukuzivocavoca umzimba, (4) ukuziphumuza, (5) ukuba yisigqili semithombo yomphakathi, (6) imikhuba emihle yokulala, (7) uqeqesho, (8) amahlaya, (10) inkolo, (11) ukuxwaya, kanye (12) nokwala. ICFA iqinisekise ukuba neqiniso kombono nokuqukethwe, kanye nokwethembeka okuxubile. Kutholakele ukuthi uhlu lwemibuzo aluguquki futhi lungasetshenziswa emaqenjini ehlukene emisebenzini yezokuphepha anengcindezi ephakeme. Kuthuthukiswe nomlinganiso olawula ingcindezi okhombisa ubudlelwano phakathi komuntu isibili nokubhekana nengcindezi. Umnikelo: Umnikelo omkhulu walolu cwaningo kube ukuqamba uhlu lwemibuzo oluqinisekile ukubhekana nengcindezi kanye nomlinganiso wokulawula ingcindezi. Ngokukhomba amasu aqondene nokubhekana nengcindezi, kungathuthukiswa izindlela ezihlosiwe zokulawula ingcindezi. Lokhu kunganikela esimeni esihle sempilo yabasebenzi bezokuphepha abasebenza imisebenzi enengcindezi ephakeme, okuzoholela enhlanganweni esesimeni esihle nasebudlelwaneni obuhle nomphakathi. Izinhlangano zezokuphepha nazo zingawusebenzisa lomlinganiso ngesikhathi sokuhlola ukubona abafundi abanezici ezinomthelela omuhle, kumasu abhekana nengcindezi asesimeni esihle, ezizobenza bakhethe abasebenzi abazongena kahle ezindaweni zokuphepha.
Industrial and Organisational Psychology
D. Phil. (Industrial and Organisational Psychology)
Books on the topic "Stress invariants"
1
Isett, Philip. Mollification along the Coarse Scale Flow. Princeton University Press, 2017. http://dx.doi.org/10.23943/princeton/9780691174822.003.0018.
Full textAbstract:
This chapter shows how to construct the appropriate mollification of the Reynolds stress along the coarse scale flow. Unlike the velocity field, which was only mollified in the spatial variables and which earned its time-regularity through the Euler-Reynolds equation, the Reynolds stress must be mollified in both space and time. Mollification along the flow is consistent with the Galilean invariance of the equations. After considering the problem of mollifying the stress in time, the chapter explains how the stress can be mollified in both space and time. It then chooses the mollification parameters, requiring that the error term generated by this mollification constitutes a small fraction of the allowable stress. It also derives estimates for the coarse scale flow as well as transport estimates for the mollified stress.
Book chapters on the topic "Stress invariants"
1
Lliboutry, Louis A. "Rotation and strain. Invariants of stress and of strain rates." In Mechanics of Fluids and Transport Processes, 37–62. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3563-1_3.
Full text
2
Könözsy, László. "Theoretical Principles and Galilean Invariance." In A New Hypothesis on the Anisotropic Reynolds Stress Tensor for Turbulent Flows, 43–55. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-13543-0_2.
Full text
3
Morro, Angelo. "Thermoviscoelasticity and Invariance of the Entropy Production Under Time Reversal." In Encyclopedia of Thermal Stresses, 6084–92. Dordrecht: Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-007-2739-7_911.
Full text
4
Nunziati, Walter, Stan Sclaroff, and Alberto Del Bimbo. "An Invariant Representation for Matching Trajectories Across Uncalibrated Video Streams." In Lecture Notes in Computer Science, 318–27. Berlin, Heidelberg: Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/11526346_35.
Full text
5
Bhatti, N. A., K. Pereira, and M. Abdel Wahab. "A Comparison Between Critical-Plane and Stress-Invariant Approaches for the Prediction of Fretting Fatigue Crack Nucleation." In Proceedings of the 7th International Conference on Fracture Fatigue and Wear, 530–38. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-0411-8_47.
Full text
6
Sun, Li, Song Qiu, Qingli Li, Hongying Liu, and Mei Zhou. "Age Estimation via Pose-Invariant 3D Face Alignment Feature in 3 Streams of CNN." In Advances in Multimedia Information Processing – PCM 2017, 172–83. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-77380-3_17.
Full text
7
Garrett, Steven L. "Three-Dimensional Enclosures." In Understanding Acoustics, 621–72. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44787-8_13.
Full textAbstract:
Abstract In this chapter, solutions to the wave equation that satisfies the boundary conditions within three-dimensional enclosures of different shapes are derived. This treatment is very similar to the two-dimensional solutions for waves on a membrane of Chap. 10.1007/978-3-030-44787-8_6. Many of the concepts introduced in Sect. 10.1007/978-3-030-44787-8_6#Sec1 for rectangular membranes and Sect. 10.1007/978-3-030-44787-8_6#Sec5 for circular membranes are repeated here with only slight modifications. These concepts include separation of variables, normal modes, modal degeneracy, and density of modes, as well as adiabatic invariance and the splitting of degenerate modes by perturbations. Throughout this chapter, familiarity with the results of Chap. 10.1007/978-3-030-44787-8_6 will be assumed. The similarities between the standing-wave solutions within enclosures of different shapes are stressed. At high enough frequencies, where the individual modes overlap, statistical energy analysis will be introduced to describe the diffuse (reverberant) sound field.
8
Alves, José Luis, and Oana Cazacu. "Effect of the Third Invariant of the Stress Deviator on the Response of Porous Solids with Pressure-Insensitive Matrix." In From Microstructure Investigations to Multiscale Modeling, 167–96. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2017. http://dx.doi.org/10.1002/9781119476757.ch7.
Full text
9
Yazdi, Saeed Varasteh, Ahlame Douzal-Chouakria, Patrick Gallinari, and Manuel Moussallam. "Time Warp Invariant Dictionary Learning for Time Series Clustering: Application to Music Data Stream Analysis." In Machine Learning and Knowledge Discovery in Databases, 356–72. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-10925-7_22.
Full text
10
Sutton, Adrian P. "Stress." In Physics of Elasticity and Crystal Defects, 9–28. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198860785.003.0002.
Full textAbstract:
The concept of stress is introduced in terms of interatomic forces acting through a plane, and in the Cauchy sense of a force per unit area on a plane in a continuum. Normal stresses and shear stresses are defined. Invariants of the stress tensor are derived and the von Mises shear stress is expressed in terms of them. The conditions for mechanical equilibrium in a continuum are derived, one of which leads to the stress tensor being symmetric. Stress is also shown to be the functional derivative of the elastic energy with respect to strain,which enables the stress tensor to be derived in models of interatomic forces. Adiabatic and isothermal stresses are distinguished thermodynamically and anharmonicity of atomic interactions is identified as the reason for their differences. Problems set 2 containsfour problems, one of which is based on Noll’s insightful analysis of stress and mechanical equilibrium.
Conference papers on the topic "Stress invariants"
1
Kremer, J. M., A. A. Shabana, and G. E. O. Widera. "Dynamic and Stress Analyisis of Spatial Flexible Mechanical Systems." In ASME 1992 Design Technical Conferences. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/detc1992-0427.
Full textAbstract:
Abstract This investigation concerns itself with the dynamic and stress analysis of thin, laminated composite plates consisting of layers of orthotropic laminae. It is assumed that the bonds between the laminae are infinitesimally thin and shear nondeformable. The finite element formulation presented is sufficiently general to accept an arbitrary number of layers and an arbitrary number of orthotropic material property sets. In the dynamic formulation presented, the laminae is assumed to undergo large arbitrary rigid body displacements and small elastic deformations. The nodal shape functions of the laminae are assumed to have rigid body modes that need to describe only large rigid body translations. Using the expressions for the kinetic and strain energies, the lamina mass and stiffness matrices are identified. The nonlinear mass matrix of the lamina is expressed in terms of a set of invariants that depend on the assumed displacement field. By summing the laminae kinetic and strain energies, the body mass and stiffness matrices are identified. It is shown that the body invariants can be expressed explicitly in terms of the invariants of its laminae. Numerical examples of a spatial RSSR mechanism demonstrate the use of the present formulation.
2
Gerolymos, Georges A., and Isabelle Vallet. "Contribution to Single-Point-Closure Reynolds-Stress Modelling of Inhomogeneous Flows." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45346.
Full textAbstract:
The purpose of this paper is to present recent advances on the development of fully single-point-closure Reynolds-stress models, for flows with strong inhomogeneities, such as solid-wall effects or strong streamwise gradients (eg. shockwave/turbulent-boundary-layer-interaction). As a starting point it is shown that several recently developed wall-normal-free (wall-topology-free) RSMs, using gradients of turbulence length-scale and of anisotropy-invariants to replace geometric normals, can be interpreted as a generalization of well-known redistribution closures but with coefficients that are not scalars but fourth-order tensors. These tensorial coefficients are function of anisotropy-invariants and of their gradients (which indicate the direction of inhomogeneity). In view of the above result, it is suggested that the theory of the redistribution tensor closure should be revisited, with emphasis on inhomogeneity effects. Four baseline sets of coefficient values are given, and the proposed models are applied for various flows (developing flow in a square duct, 2-D and 3-D separated flows).
3
Parsa, M. H., K. A. Shirvanedeh, and P. H. Matin. "Possibility of Expressing Anisotropic Yield Functions of Metals using the Invariants of Stress Tensor." In THE 8TH INTERNATIONAL CONFERENCE AND WORKSHOP ON NUMERICAL SIMULATION OF 3D SHEET METAL FORMING PROCESSES (NUMISHEET 2011). AIP, 2011. http://dx.doi.org/10.1063/1.3623609.
Full text
4
Minucci, Frederico R., Auteliano A. dos Santos @sJr., and Rafael A. Lima e Silva. "Presentation and Comparison of Three Multiaxial Fatigue Criteria Based on Stress Invariants Applied to a Crankshaft." In SAE Brasil 2010 Congress and Exhibit. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2010. http://dx.doi.org/10.4271/2010-36-0316.
Full text
5
Kitayama, Satoshi, and Hiroshi Yamakawa. "A Study on Optimum Topology of Plate Structure Using Coordinate Transformation by Conformal Mapping." In ASME 2002 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/detc2002/dac-34053.
Full textAbstract:
This paper presents a new method to determine an optimum topology of plate structure using coordinate transformation by conformal mapping. We have already proposed a method to determine an optimum topology of planar structure using coordinate transformation by conformal mapping. In that study first we defined simple design domain in which analysis and optimization were performed easily. We calculated optimum topology in this simple design domain. Then we applied coordinate transformation by conformal mapping to optimum topology calculated in simple design domain, and obtained some optimum topologies in complex design domain. We also showed that the invariants of stresses which were the sum and difference of principal stress satisfied Laplace equation and relationshi p between fluid mechanics and electromagnetic could be valid in the theory of elasticity. In this study we clarify two invariants of bending moments satisfy Laplace equation under a certain condition. We note the similarity between Airy stress function of 2-D elastic body and deflection of plate, and will show that the two invariants of bending moments which are the sum and difference of principal bending moments satisfy Laplace equation using this similarity. As a result we will show that corresponding relationship between fluid mechanics, electromagnetic and elasticity may be valid in the theory of plate. Then by using this relationship, we proposed a new method to determine optimum topology using coordinate transformation by conformal mapping. Our proposed method will be useful to determine optimum topology easily in complex design domain. Through numerical examples, we can examine the effectiveness of the proposed method.
6
Revuzhenko, A. F., and O. A. Mikenina. "Criteria of limit state and failure of geomaterials based on the new system of invariants of stress tensor." In INTERNATIONAL CONFERENCE ON PHYSICAL MESOMECHANICS OF MULTILEVEL SYSTEMS 2014. AIP Publishing LLC, 2014. http://dx.doi.org/10.1063/1.4898995.
Full text
7
Naji, H., O. El Yahyaoui, and G. Mompean. "A Priori Analysis of Explicit Algebraic Stress Models for a Turbulent Flow Through a Straight Square Duct." In ASME/JSME 2004 Pressure Vessels and Piping Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/pvp2004-2846.
Full textAbstract:
The ability of two explicit algebraic Reynolds stress models (EARSMs) to accurately predict the problem of fully turbulent flow in a straight square duct is studied. The first model is devised by Gatski and Rumsey (2001) and the second is the one derived by Wallin and Johansson (2000). These models are studied using a priori procedure based on data resulting from direct numerical simulation (DNS) of the Navier-Stokes equations, which is available for this problem. For this case, we show that the equilibrium assumption for the anisotropy tensor is found to be correct. The analysis leans on the maps of the second and third invariants of the Reynolds stress tensor. In order to handle wall-proximity effects in the near-wall region, damping functions are implemented in the two models. The predictions and DNS obtained for a Reynolds number of 4800 both agree well and show that these models are able to predict such flows.
8
Liu, Shuhong, Xuelin Tang, Yulin Wu, and Michihiro Nishi. "Simulation of Dense Solid-Liquid Two-Phase Flow in a Pump Impeller." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56208.
Full textAbstract:
In the present study, simulation with the second-order dynamic model for sub-grid stress is used to solve the governing equations of dense solid-liquid two-phase (DSLTP) flow numerically, and continuity is conserved by a mass-weighted method to solve the filtered governing equations. In the current second-order dynamic model with double dynamic coefficients, the sub-grid-scale stress is a function of both the strain-rate tensor and the rotation-rate tensor. This model considers the symmetry of the sub-grid-scale stresses, dimensional consistency with the Cauchy-Helmholtz theorem, the Smagorinsky model and the invariants of the strain-rate tensor and the rotation-rate tensor in large eddy simulation (LES). In the numerical calculation, the SIMPLEC algorithm and a staggered grid system were applied for the solution of the discretized particle-liquid turbulent flow equations, and Body-fitted Coordinates were used to simulate the flow over the complex geometry field. In this paper, the second-order dynamic model for turbulent dense solid-liquid two-phase flows was applied to a centrifugal pump impeller.
9
Anani, Y., M. Asghari, and R. Naghdabadi. "Modeling of Rate Dependent Finite Deformation Viscoelastic Behavior of Foams." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-66952.
Full textAbstract:
The behavior of foams is typically rate-dependent and viscoelastic. In this paper, multiplicative decomposition of the deformation gradient and the second law of thermodynamics are employed to develop the differential constitutive equations for isotropic viscoelastic foams experiencing finite deformations, from a phenomenological point of view, i.e. without referring to micro-structural viewpoint. A model containing an equilibrium hyperelastic spring which is parallel to a Maxwell model has been utilized for introducing constitutive formulation. The deformation gradient tensor is decomposed into two parts: elastic deformation gradient tensor and viscoelastic deformation gradient tensor. A strain energy function is presented for the equilibrium spring as a function of the invariants of the left Cauchy-Green stretch tensor to obtain equilibrium stress components. Also, a strain energy function is presented for the intermediate spring as a function of the invariants of elastic deformation gradient tensor to determine overstress components. The constants of the strain energies are calculated by using nonlinear regulation numerical methods and by comparing with the experimental data obtained from uniaxial tension tests. The developed finite deformation constitutive equations are derived such that for every admissible process, the second law of thermodynamics is satisfied.
10
Janosik, Lesley A., and Stephen F. Duffy. "A Viscoplastic Constitutive Theory for Monolithic Ceramics: I." In ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-368.
Full textAbstract:
This paper, which is the first of two in a series, provides an overview of a viscoplastic constitutive model that accounts for time-dependent material deformation (e.g., creep, stress relaxation, etc.) in monolithic ceramics. Using continuum principles of engineering mechanics the complete theory is derived from a scalar dissipative potential function first proposed by Robinson (1978), and later utilized by Duffy (1988). Derivations based on a flow potential function provide an assurance that the inelastic boundary value problem is well posed, and solutions obtained are unique. The specific formulation used here for the threshold function (a component of the flow potential function) was originally proposed by Willam and Warnke (1975) in order to formulate constitutive equations for time-independent classical plasticity behavior observed in cement and unreinforced concrete. Here constitutive equations formulated for the flow law (strain rate) and evolutionary law employ stress invariants to define the functional dependence on the Cauchy stress and a tensorial state variable. This particular formulation of the viscoplastic model exhibits a sensitivity to hydrostatic stress, and allows different behavior in tension and compression.