Global ETD Search

1	NOVEL ON-LINE TRUE STRESS-STRAIN-ELECTRICAL CONDUCTIVITYUNIAXIAL TENSILE STRETCHING SYSTEM AND ITS UTILITY ON ELECTRICALLYCONDUCTIVE POLYLACTIC ACID (PLA) NANOCOMPOSITES Kwa, Teik Lim 18 May 2006 (has links) No description available. PLA nanocomposites electrical conductive PTC preferential alignment of CB networks
2	Analýza mechanických vlastností polymerů a polymerních kompozitů z videozáznamu tahové zkoušky / Analysis of mechanical properties of polymers and polymer compsites from video record of tensile test Ščudlová, Jolana January 2010 (has links) This thesis described mechanical tests with monitoring of camera. The aim of this work is to obtain additional information about material behavior during the test. The mechanical tests were monitored high-definition (HD) digital video-camera and camera with high resolution. The method was applied to the tensile test and Pennsylvania notch test (PENT test). The videorecordings were processed with the assistance image analysis method. The marks were placed on both of these specimens, mutual movement these marks were used to obtain following characteristics. It was Poisson’s ratio and true stress by tensile test. By PENT test it was rate growth crack. The investigated material was elastomeric polyurethane filled by biodegradable polyhydroxybutyrate for tensile test. Second material was polypropylene for PENT test. The camera is adding to the test gives extended information about the material and better interpretation results.
3	An Active Study of a Roller Coaster Project in Asia. Bridges, Robert Leamon 08 May 2010 (has links) A roller coaster manufacturer became aware that improperly heat treated track couplings were sent to a construction site for assembly. Concerns were that suspect couplings might not meet the engineering specifications and could be vulnerable to sudden failure. A testing company in Oak Ridge, TN that specializes in in-situ and laboratory mechanical testing was contacted by the manufacturer for help in this endeavor. The construction company elected to enlist a local testing firm to perform field tests on the components instead of the company in Oak Ridge. The test methods used are incapable of providing quantitative results that could be measured to the engineering specifications, making it unlikely to identify anything but the worst material conditions. This study is an example that the need for accurate analysis is very important. The manufacturer reported that 60 couplings were replaced, but it is presently unknown how many should have been replaced. yield strength ultimate strength Stress-Strain Microprobe« Automated Ball Indentation test Charpy V-notch non-destructive test Engineering Operational Research Risk Analysis
4	Characterization of Fatigue Cracking and Healing of Asphalt Mixtures Luo, Xue 2012 May 1900 (has links) Fatigue cracking is one of the most common distresses of asphalt pavements, whereas healing is a counter process to cracking which alleviates cracking damage and extends fatigue life of asphalt pavements. Most of existing methods to characterize fatigue cracking and healing are generally empirical or phenomenological in nature, which does not satisfy the need to develop mechanistic-based pavement design methods. The objective of this study is to characterize fatigue cracking and healing of asphalt mixtures using an energy-based mechanistic approach. A controlled-strain repeated direct tension (RDT) test is selected to generate both fatigue cracking and permanent deformation in an asphalt mixture specimen. Fatigue cracking is separated from permanent deformation from a mechanical viewpoint. The development of fatigue cracking is described by the evolution of the damage density and the increase of the average crack size with the increase of loading cycles. A creep and step-loading recovery (CSR) test is designed to measure the internal stress in the recovery phase of an asphalt mixture specimen. The internal stress and the strain measured in the recovery phase are used to conduct the mechanistic analysis of recovery and healing of the asphalt mixture specimen. Then healing is described using the decrease of the damage density and average crack size with time. Different types of asphalt mixtures produce distinctly different fatigue cracking and healing characteristics. The effect of mixture composition, temperature, and aging are evaluated using the approach above. The entire series of tests for fatigue, permanent deformation and healing can be completed in one day, with the healing part requiring only a matter of minutes. The methods proposed in this study characterize fatigue cracking and healing of asphalt mixtures using its essential cause and effect relationship. asphalt mixtures fatigue crack growth healing recovery dissipated pseudo strain energy recoverable pseudo strain energy dissipated strain energy recoverable strain energy energy-based mechanistic approach true stress internal stress damage density average crack size number of cracks
5	Investigation of a thermomechanical process in a high temperature deformation simulator using an FE software : Using LS-DYNA to create a digital twin of the hot deformation simulator Gleeble-3800 GTC Hydrawedge module. Tregulov, Farhad January 2024 (has links) Thermomechanical processes such as hot rolling have been used in the industry for a long time to process and shape metals to a desired form with specific properties. However it can be difficult to make changes to the different process parameters. That's where it is beneficial to use a hot deformation simulator such as the Gleeble 3800-GTC. It can be used to test metals in a controlled environment where the deformation, temperature and other parameters are easily changed. When the machine uses a Hydrawedge module, it is able to simulate hot rolling using uniaxial compression at high temperatures. Swerim AB has one such machine and has requested to investigate what occurs inside a specimen during testing in the Gleeble, specifically inside two low-alloyed steels with a hardness between 400 and 500 HV. Such tests were replicated using LS-DYNA, an FE software. The goal was to acquire true stress-strain graphs that showed similar behaviour to the data from the Gleeble and plots of the effective plastic strain which could be correlated to the grain structure pattern inside the deformed cylinders. An FE-model was created which replicates the procedure. The model was verified through numerous steps. An initial mesh verification was done where the simulation time took at least 5 hours and at most 86 hours. Using a technique called mass scaling, the elements inside the model were manipulated using additional mass to increase their time step and reduce the computational time. A verification of the mass scaling was done where the computational time was weighed off against accuracy. Afterwards the friction had to be verified where it was found that the Gleeble test specimens were deformed more than necessary which was taken into account and the models were adjusted for friction verification. After all was said and done, the model had a reasonable friction coefficient with an optimal mesh and mass scaling configuration. The resulting model simulated a test of 0.5 seconds in 15 minutes and only costing at most 10 MPa in accuracy when experimental results have maximum values between 110 to 220 MPa depending on the scenario. This equals an approximate error of around 5-10%. When investigating the grain structure after 100 seconds of relaxation, the computational time amounted to 52 hours but could be reduced to 12 hours when simulating 30 seconds as there was no change in the effective plastic strain after that time. The final model has a high enough accuracy which, when combined with the Gleeble, is able to confirm material models and describe what occurs in the material during conditions akin to hot rolling. Thermomechanical process Hot rolling Digital twin Hot deformation simulator High temperature deformation simulator Gleeble-3800 GTC Hydrawedge LS-DYNA Uniaxial compression FE software True stress-strain Effective plastic strain Grain structure Applied Mechanics Teknisk mekanik
6	Grundlagen der Elasto-Plastizität in Creo Simulate - Theorie und Anwendung / Basics of Elasto-Plasticity in Creo Simulate - Theory and Application Jakel, Roland 10 May 2012 (has links) (PDF) Der Vortrag beschreibt die Grundlagen der Elasto-Plastizität sowie die softwaretechnische Anwendung mit dem FEM-Programm Creo Simulate bzw. Pro/MECHANICA von PTC. Der erste Teil des Vortrages beschreibt die Charakteristika plastischen Verhaltens, unterschiedliche plastische Materialgesetze, Fließkriterien bei mehrachsiger Beanspruchung und unterschiedliche Verfestigungsmodelle. Im zweiten Vortragsteil werden Möglichkeiten und Grenzen der Berechnung elasto-plastischer Probleme mit der Software dargestellt sowie Anwendungstipps gegeben. Im dritten Vortragsteil schließlich werden verschiedene Beispiele vorgestellt, davon besonders ausführlich das Verhalten einer einachsigen elasto-plastischen Zugprobe vor und nach dem Eintreten der Einschnürdehnung. / This presentation describes the basics of elasto-plasticity and its application with the finite element software Creo Simulate (formerly Pro/MECHANICA) from PTC. The first part describes the characteristics of plastic behavior, different plastic material laws, yield criteria for multiaxial stress states and different hardening models. In the second part, the opportunities and limitations of analyzing elasto-plastic problems with the FEM-code are described and user information is provided. The last part finally presents different examples. Deeply treated is the behavior of a uniaxial tensile test specimen before and after elongation with necking appears. Elasto-Plastizität Creo Simulate Mechanica FEM Plastitzität kleiner Dehnungen Plastitzität großer Dehnungen technische Spannung wahre Spannung technische Dehnung logarithmische Dehnung kinematische und isotrope Verfestigung plastische Materialgesetze sprödes und duktiles Verhalten Mehrachsigkeit Lastschritte Entlasten Elasto-plasticity Creo Simulate Mechanica FEM small strain plasticity finite strain plasticity engineering stress true stress engineering strain logarithmic strain yield criteria kinematic and isotropic hardening elasto-plastic material laws brittle and ductile behavior multi-axial plasticity characteristic measures for plasticity load steps unloading meshing uniaxial tensile test with necking ddc:629 Fließbedingung Plastizität Dehnung Mehrachsigkeit Vernetzung
7	Lineare und nichtlineare Analyse hochdynamischer Einschlagvorgänge mit Creo Simulate und Abaqus/Explicit / Linear and Nonlinear Analysis of High Dynamic Impact Events with Creo Simulate and Abaqus/Explicit Jakel, Roland 23 June 2015 (has links) (PDF) Der Vortrag beschreibt wie sich mittels der unterschiedlichen Berechnungsverfahren zur Lösung dynamischer Strukturpobleme der Einschlag eines idealisierten Bruchstücks in eine Schutzwand berechnen lässt. Dies wird mittels zweier kommerzieller FEM-Programme beschrieben: a.) Creo Simulate nutzt zur Lösung die Methode der modalen Superposition, d.h., es können nur lineare dynamische Systeme mit rein modaler Dämpfung berechnet werden. Kontakt zwischen zwei Bauteilen lässt sich damit nicht erfassen. Die unbekannte Kraft-Zeit-Funktion des Einschlagvorganges muss also geeignet abgeschätzt und als äußere Last auf die Schutzwand aufgebracht werden. Je dynamischer der Einschlagvorgang, desto eher wird der Gültigkeitsbereich des zugrunde liegenden linearen Modells verlassen. b.) Abaqus/Explicit nutzt ein direktes Zeitintegrationsverfahren zur schrittweisen Lösung der zugrunde liegenden Differentialgleichung, die keine tangentiale Steifigkeitsmatrix benötigt. Damit können sowohl Materialnichtlinearitäten als auch Kontakt geeignet erfasst und damit die Kraft-Zeit-Funktion des Einschlages ermittelt werden. Auch bei extrem hochdynamischen Vorgängen liefert diese Methode ein gutes Ergebnis. Es müssen dafür jedoch weit mehr Werkstoffdaten bekannt sein, um das nichtlineare elasto-plastische Materialverhalten mit Schädigungseffekten korrekt zu beschreiben. Die Schwierigkeiten der Werkstoffdatenbestimmung werden in den Grundlagen erläutert. / The presentation describes how to analyze the impact of an idealized fragment into a stell protective panel with different dynamic analysis methods. Two different commercial Finite Element codes are used for this: a.) Creo Simulate: This code uses the method of modal superposition for analyzing the dynamic response of linear dynamic systems. Therefore, only modal damping and no contact can be used. The unknown force-vs.-time curve of the impact event cannot be computed, but must be assumed and applied as external force to the steel protective panel. As more dynamic the impact, as sooner the range of validity of the underlying linear model is left. b.) Abaqus/Explicit: This code uses a direct integration method for an incremental (step by step) solution of the underlying differential equation, which does not need a tangential stiffness matrix. In this way, matieral nonlinearities as well as contact can be obtained as one result of the FEM analysis. Even for extremely high-dynamic impacts, good results can be obtained. But, the nonlinear elasto-plastic material behavior with damage initiation and damage evolution must be characterized with a lot of effort. The principal difficulties of the material characterization are described. Einschlag Impuls Stahl-Schutzwand lineare und nichtlineare Dynamik modale Superposition direkte Zeitintegration Schädigungsinitiierung Schädigungsfortschritt Zugversuch Gleichmaßdehnung Einschnürdehnung FEM Creo Simulate Abaqus/Explicit impact impulse steel protective panel direct time integration damage of elasto-plastic materials damage initiation damage evolution tensile test elongation without necking local necking engineering and true stress and strain FEM Creo Simulate Abaqus/Explicit ddc:629 Impuls Zugversuch Gleichmassdehnung Creo Simulate Abaqus
8	Lineare und nichtlineare Analyse hochdynamischer Einschlagvorgänge mit Creo Simulate und Abaqus/Explicit / Linear and Nonlinear Analysis of High Dynamic Impact Events with Creo Simulate and Abaqus/Explicit Jakel, Roland 23 June 2015 (has links) Der Vortrag beschreibt wie sich mittels der unterschiedlichen Berechnungsverfahren zur Lösung dynamischer Strukturpobleme der Einschlag eines idealisierten Bruchstücks in eine Schutzwand berechnen lässt. Dies wird mittels zweier kommerzieller FEM-Programme beschrieben: a.) Creo Simulate nutzt zur Lösung die Methode der modalen Superposition, d.h., es können nur lineare dynamische Systeme mit rein modaler Dämpfung berechnet werden. Kontakt zwischen zwei Bauteilen lässt sich damit nicht erfassen. Die unbekannte Kraft-Zeit-Funktion des Einschlagvorganges muss also geeignet abgeschätzt und als äußere Last auf die Schutzwand aufgebracht werden. Je dynamischer der Einschlagvorgang, desto eher wird der Gültigkeitsbereich des zugrunde liegenden linearen Modells verlassen. b.) Abaqus/Explicit nutzt ein direktes Zeitintegrationsverfahren zur schrittweisen Lösung der zugrunde liegenden Differentialgleichung, die keine tangentiale Steifigkeitsmatrix benötigt. Damit können sowohl Materialnichtlinearitäten als auch Kontakt geeignet erfasst und damit die Kraft-Zeit-Funktion des Einschlages ermittelt werden. Auch bei extrem hochdynamischen Vorgängen liefert diese Methode ein gutes Ergebnis. Es müssen dafür jedoch weit mehr Werkstoffdaten bekannt sein, um das nichtlineare elasto-plastische Materialverhalten mit Schädigungseffekten korrekt zu beschreiben. Die Schwierigkeiten der Werkstoffdatenbestimmung werden in den Grundlagen erläutert. / The presentation describes how to analyze the impact of an idealized fragment into a stell protective panel with different dynamic analysis methods. Two different commercial Finite Element codes are used for this: a.) Creo Simulate: This code uses the method of modal superposition for analyzing the dynamic response of linear dynamic systems. Therefore, only modal damping and no contact can be used. The unknown force-vs.-time curve of the impact event cannot be computed, but must be assumed and applied as external force to the steel protective panel. As more dynamic the impact, as sooner the range of validity of the underlying linear model is left. b.) Abaqus/Explicit: This code uses a direct integration method for an incremental (step by step) solution of the underlying differential equation, which does not need a tangential stiffness matrix. In this way, matieral nonlinearities as well as contact can be obtained as one result of the FEM analysis. Even for extremely high-dynamic impacts, good results can be obtained. But, the nonlinear elasto-plastic material behavior with damage initiation and damage evolution must be characterized with a lot of effort. The principal difficulties of the material characterization are described. info:eu-repo/classification/ddc/629 ddc:629
9	Grundlagen der Elasto-Plastizität in Creo Simulate - Theorie und Anwendung / Basics of Elasto-Plasticity in Creo Simulate - Theory and Application Jakel, Roland 10 May 2012 (has links) Der Vortrag beschreibt die Grundlagen der Elasto-Plastizität sowie die softwaretechnische Anwendung mit dem FEM-Programm Creo Simulate bzw. Pro/MECHANICA von PTC. Der erste Teil des Vortrages beschreibt die Charakteristika plastischen Verhaltens, unterschiedliche plastische Materialgesetze, Fließkriterien bei mehrachsiger Beanspruchung und unterschiedliche Verfestigungsmodelle. Im zweiten Vortragsteil werden Möglichkeiten und Grenzen der Berechnung elasto-plastischer Probleme mit der Software dargestellt sowie Anwendungstipps gegeben. Im dritten Vortragsteil schließlich werden verschiedene Beispiele vorgestellt, davon besonders ausführlich das Verhalten einer einachsigen elasto-plastischen Zugprobe vor und nach dem Eintreten der Einschnürdehnung. / This presentation describes the basics of elasto-plasticity and its application with the finite element software Creo Simulate (formerly Pro/MECHANICA) from PTC. The first part describes the characteristics of plastic behavior, different plastic material laws, yield criteria for multiaxial stress states and different hardening models. In the second part, the opportunities and limitations of analyzing elasto-plastic problems with the FEM-code are described and user information is provided. The last part finally presents different examples. Deeply treated is the behavior of a uniaxial tensile test specimen before and after elongation with necking appears. info:eu-repo/classification/ddc/629 ddc:629

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