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Deformation Behavior (deformation + behavior)
Selected AbstractsA Micromechanical Study of the Deformation Behavior of TRIP-Assisted Multiphase Steels as a Function of the Microstructural Parameters of the Retained AusteniteADVANCED ENGINEERING MATERIALS, Issue 3 2009Denny Tjahjanto The influence of austenitic volume fraction, carbon concentration, and grain size on the behavior of multiphase TRIP steels is investigated by means of micromechanical modeling and finite element simulations. The present analysis allows to directly attribute overall mechanical characteristics to the corresponding microstructural parameters, which is a difficult task to perform experimentally. [source] Novel Nanostructure and Deformation Behavior in Rapidly Quenched Cu- (Zr or Hf)-Ti Alloys,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2005J. Saida Novel nanostructure consisting of the metastable nanocrystalline particles embedded in the glassy matrix are reported in the rapidly quenched Cu60(Zr or Hf)30Ti10 alloys. The transformation behavior and mechanical properties in the nanoscale composite alloys are also investigated. The as-cast bulk sample of Cu60Zr30Ti10 alloy exhibits the high fracture strength of approximately 2000 MPa in the compressive test at room temperature. [source] Elementary Mechanisms behind the High-Temperature Deformation Behavior of Lutetium-Doped Silicon NitrideJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2003Giuseppe Pezzotti Intergranular sliding and diffusive mechanisms behind the deformation behavior of a commercially available lutetium-doped silicon nitride were investigated and discussed. A method of locating and separating phenomena critical for mechanical relaxation at elevated temperatures was applied; the method was based on low-frequency forced-vibration damping measurements. The potentiality of lutetium addition for improving the deformation resistance of silicon nitride was clearly reflected in the high-temperature damping behavior of the investigated polycrystal. Softening of intergranular lutetium silicate phases located at multigrain junctions, which resulted in a grain-boundary sliding peak, occurred at remarkably high temperatures (>1725 K). This phenomenon, partly overlapping diffusional flow, was followed by further damping relaxation with the melting of the lutetium silicates. Subsequent grain growth was also detected at temperatures >2100 K. Torsional creep results, collected up to 2100 K, consistently proved the presence of a "locking" effect by lutetium silicates with the sliding of silicon nitride grain boundaries below 1873 K. [source] Deformation Behavior of PET, PBT and PBT-Based Thermoplastic Elastomers as Revealed by SAXS from SynchrotronMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2003Norbert Stribeck Abstract The present paper discloses the changes in the nanostructure as revealed by small-angle X-ray scattering (SAXS) of synchrotron radiation of anisotropic semi-crystalline samples of polyester and poly(ether ester) type differing in their chemical composition, while subjected to controlled progressive elongation. From the group of polyesters poly(ethylene terephthalate) (PET), and poly(butylene terephthalate) (PBT) were selected. Two PBT-based commercial poly(ether ester)s were also studied differing in the molecular weight of their soft segments (poly(tetramethylene glycol), PTMG) being 1000 and 2000, respectively. A blend of PBT and EM550 (40/60 by wt.) was also characterized. All materials underwent the same sample preparation process resulting in highly oriented "bristles" of 1 mm diameter. It was found that ,b, the elongation at break, strongly depends on the flexibility of the glycol residues of the materials studied , ranging from ,b,=,8% for PET that contains ethylene glycol residues, through ,b,=,18% for PBT including the more flexible tetramethylene glycol (TMG) up to ,b,=,510% for the PEE containing the longest PTMG moieties. During straining the relationship between the external elongation , and the changes in the long spacing L was determined. After relaxation from each deformation step the relationship between the tensile set ,r and the long period L was also followed and discussed. Such analysis led to a model describing the nanostructure evolution during the deformation-relaxation cycle that finally was verified and refined utilizing the multidimensional chord distribution function computed from the anisotropic SAXS patterns. 2D SAXS patterns (pseudo color) of bristles of PET (PBT), respectively, cold drawn, ,,=,3.5 (,,=,2.3) and annealed with fixed ends for 6 h at 240,°C (180,°C), recorded at room temperature at a forced tensile deformation , or tensile set (residual elongation) ,r in percent. [source] On Processing and Impact Deformation Behavior of High Density Polyethylene (HDPE),Calcium Carbonate NanocompositesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2009Qiang Yuan Abstract Different processing approaches were adopted to obtain the best combination of strength and toughness. The approach that yielded superior properties was examined in detail to study the mechanical response of nanoscale calcium carbonate-reinforced high density polyethylene in conjunction with unreinforced high density polyethylene. The reinforcement of high density polyethylene with nanoscale calcium carbonate increases impact strength and is not accompanied by decrease in yield strength. The addition of nanoscale calcium carbonate to high density polyethylene alters the micromechanism of deformation from crazing-tearing in high density polyethylene to fibrillation in high density polyethylene,calcium carbonate nanocomposite. [source] Strain-Controlled Tensile Deformation Behavior and Relaxation Properties of Isotactic Poly(1-butene) and Its Ethylene CopolymersMACROMOLECULAR SYMPOSIA, Issue 1 2004Mahmoud Al-Hussein Abstract The tensile deformation behaviour of poly(1-butene) and two of its ethylene copoloymers was studied at room temperature. This was done by investigating true stress-strain curves at constant strain rates, elastic recovery and stress relaxation properties and in-situ WAXS patterns during the deformation process. As for a series of semicrystalline polymers in previous studies, a strain-controlled deformation behaviour was found. The differential compliance, the recovery properties and the stress relaxation curves changed simultaneously at well-defined points. The strains at which these points occurred along the true stress-strain remained constant for the different samples despite their different percentage crystallinities. The well-defined way in which the different samples respond to external stresses complies with the granular substructure of the crystalline lamellae in a semicrystalline polymer. [source] Physically Guided Animation of TreesCOMPUTER GRAPHICS FORUM, Issue 2 2009Ralf Habel Abstract This paper presents a new method to animate the interaction of a tree with wind both realistically and in real time. The main idea is to combine statistical observations with physical properties in two major parts of tree animation. First, the interaction of a single branch with the forces applied to it is approximated by a novel efficient two step nonlinear deformation method, allowing arbitrary continuous deformations and circumventing the need to segment a branch to model its deformation behavior. Second, the interaction of wind with the dynamic system representing a tree is statistically modeled. By precomputing the response function of branches to turbulent wind in frequency space, the motion of a branch can be synthesized efficiently by sampling a 2D motion texture. Using a hierarchical form of vertex displacement, both methods can be combined in a single vertex shader, fully leveraging the power of modern GPUs to realistically animate thousands of branches and ten thousands of leaves at practically no cost. [source] Failure Mechanism of Deformed Concrete Tunnels Subject to Diagonally Concentrated LoadsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 6 2009Wei He Based on the experimental findings, an extended discussion is carried out to select a rational compressive model for concrete that represents the dominant failure modes of deformed concrete tunnels. Three main dominant final failure modes are described: structural failure due to the plastic rotation of softening hinges, tensile failure caused by localized cracks, and material failure due to concrete deterioration. A parametric analysis of the material properties of concrete shows that the compressive strength of concrete has a dominant effect on the load-carrying capacity, although the compressive fracture energy of concrete remarkably influences the post-peak deformation behavior of the tunnel. Moreover, the soil pressure, which is regarded as a distributed external load, plays an important role in controlling the final failure modes and the deformation behavior of concrete tunnels. The size effect on the load-carrying capacities of different-sized concrete tunnels is also discussed based on the numerical simulations. [source] Size Independent Shape Memory Behavior of Nickel,Titanium,ADVANCED ENGINEERING MATERIALS, Issue 8 2010Blythe G. Clark While shape memory alloys such as NiTi have strong potential as active materials in many small-scale applications, much is still unknown about their shape memory and deformation behavior as size scale is reduced. This paper reports on two sets of experiments which shed light onto an inconsistent body of research regarding the behavior of NiTi at the nano- to microscale. In situ SEM pillar bending experiments directly show that the shape memory behavior of NiTi is still present for pillar diameters as small as 200,nm. Uniaxial pillar compression experiments demonstrate that plasticity of the phase transformation in NiTi is size independent and, in contrast to bulk single crystal observations, is not influenced by heat treatment (i.e., precipitate structure). [source] Strength Effects in Micropillars of a Dispersion Strengthened Superalloy,ADVANCED ENGINEERING MATERIALS, Issue 5 2010Baptiste Girault The present paper investigates the uniaxial compression behavior of highly alloyed, focused ion beam (FIB) manufactured micropillars, ranging from 200 up to 4000,nm in diameter. The material used was the Ni-based oxide-dispersion strengthened (ODS) alloy Inconel MA6000. Stress,strain curves show a change in slip behavior comparable to those observed in pure fcc metals. Contrary to pure Ni pillar experiments, high critical resolved shear stress (CRSS) values were found independent of pillar diameter. This suggests that the deformation behavior is primarily controlled by the internal obstacle spacing, overwhelming any pillar-size-dependent mechanisms such as dislocation source action or starvation. [source] Determination of Activation Volume in Nanocrystalline Cu Using the Shear Punch Test,ADVANCED ENGINEERING MATERIALS, Issue 10 2007K. Guduru Stress relaxation test (SRT) is very useful to study the dislocation dynamics and thus the deformation behavior. It becomes quite difficult to use conventional testing methods when the material availability is limited. In such instances, miniaturized specimen testing procedures such as shear punch test (SPT) becomes significantly useful for studying the mechanical behavior of materials. Current research deals with a novel SRT method employed on nanocrystalline Cu using SPT to study the deformation mechanism. [source] Elementary Mechanisms behind the High-Temperature Deformation Behavior of Lutetium-Doped Silicon NitrideJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2003Giuseppe Pezzotti Intergranular sliding and diffusive mechanisms behind the deformation behavior of a commercially available lutetium-doped silicon nitride were investigated and discussed. A method of locating and separating phenomena critical for mechanical relaxation at elevated temperatures was applied; the method was based on low-frequency forced-vibration damping measurements. The potentiality of lutetium addition for improving the deformation resistance of silicon nitride was clearly reflected in the high-temperature damping behavior of the investigated polycrystal. Softening of intergranular lutetium silicate phases located at multigrain junctions, which resulted in a grain-boundary sliding peak, occurred at remarkably high temperatures (>1725 K). This phenomenon, partly overlapping diffusional flow, was followed by further damping relaxation with the melting of the lutetium silicates. Subsequent grain growth was also detected at temperatures >2100 K. Torsional creep results, collected up to 2100 K, consistently proved the presence of a "locking" effect by lutetium silicates with the sliding of silicon nitride grain boundaries below 1873 K. [source] Study on Flow Induced Nano Structures in iPP with Different Molecular Weight and Resulting Strength BehaviorMACROMOLECULAR SYMPOSIA, Issue 1 2010Achim Frick Abstract Polypropylene samples in a wide molecular weight range between approx. 100,kg/mol to 1 600,kg/mol were processed by injection molding to thin walled micro specimens with respect to study shear induced crystallization phenomena under high shear rate and subsequently possible self reinforcement effects. The specimens nano structures were investigated and related deformation behavior under tensile studied. Novel morphologies have been detect and their micromechanical mechanism interpret and summarized. [source] Properties and strain hardening character of polyethylene terephthalate containing IsosorbidePOLYMER ENGINEERING & SCIENCE, Issue 3 2009Ramesh M. Gohil Polyethylene terephthalate containing Isosorbide (PEIT) polymers made from renewable corn-derived Isosorbide monomer exhibit a wide range of glass transition temperatures (80,180°C) and are therefore able to be used in many applications. Stress,strain curves for high Isosorbide content copolymers show strain softening, which impairs the molecular orientation during orientation of films and bottles. It is therefore necessary to find ways to modify deformation behavior of PEIT copolymers. Deformation characteristics of PEIT and other polyesters have been evaluated to define stretching parameters and necessary composition for making oriented bottles for hot fill applications. In the presence of polymeric nucleating agents, (polymeric ionomers or polyesters containing sodium ions), strain-hardening parameters become almost temperature- independent below solid state deformation temperature of 125°C. We developed a methodology to achieve molecular orientation comparable with films and articles made by conventional processing of poly(ethylene terephthalate), PET. Polyesters containing sodium ions are efficient nucleating agents for PEIT, and their required concentration is dependent on deformation temperature. Both strain hardening and stress at 250% strain depend on the concentration of nucleating agents and deformation temperatures. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] A uniform phenomenological constitutive model for glassy and semicrystalline polymersPOLYMER ENGINEERING & SCIENCE, Issue 8 2001Y. Duan A phenomenological constitutive model is proposed on the basis of four models: the Johnson-Cook model, the G'Sell-Jonas model, the Matsuoka model, and the Brooks model. The proposed constitutive model has a concise expression of stress dependence on strain, strain rate and temperature. It is capable of uniformly describing the entire range of deformation behavior of glassy and semicrystalline polymers, especially the intrinsic strain softening and subsequent orientation hardening of glassy polymers. At least three experimental stress-strain curves including variation with strain rate and temperature are needed to calibrate the eight material coefficients. Sequential calibration procedures of the eight material coefficients are given in detail. Predictions from the proposed constitutive model are compared with experimental data of two glassy polymers, polymethyl-methacrylate and polycarbonate under various deformation conditions, and with that of the G'Sell-Jonas model for polyamide 12, a semicrystalline polymer. [source] Morphology and micromechanical properties of ethylene/1-octene copolymers and their blends with high density polyethylene,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2-3 2005R. Adhikari Abstract The relationship between morphology and deformation behavior of selected ethylene/1-octene copolymers (EOCs) and their blends with high density polyethylene (HDPE) was investigated. The copolymers showed, depending on the 1-octene content, different morphologies ranging from lamellar to worm-like crystalline domains. The binary HDPE/EOC blends studied, which showed well phase-separated structures consistent with individual melting and crystallization behavior of the blend components, were characterized by a wide range of mechanical and micromechanical properties. The study of strain induced structural changes in an HDPE/EOC blend revealed that at large strains, the extensive stretching of the soft EOC phase is accompanied by rotation of lamellar stack along the strain axis and subsequent fragmentation of the crystals forming beaded-string-like structures. A significant depression in microhardness was observed in the copolymers. In their blends with HDPE, a deviation in microhardness behavior from the additivity law was observed. Copyright © 2005 John Wiley & Sons, Ltd. [source] Homogenization in the Theory of ViscoplasticityPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005Sergiy Nesenenko We study the homogenization of the quasistatic initial boundary value problem with internal variables which models the deformation behavior of viscoplastic bodies with a periodic microstructure. This problem is represented through a system of linear partial differential equations coupled with a nonlinear system of differential equations or inclusions. Recently it was shown by Alber [2] that the formally derived homogenized initial boundary value problem has a solution. From this solution we construct an asymptotic solution for the original problem and prove that the difference of the exact solution and the asymptotic solution tends to zero if the lengthscale of the microstructure goes to zero. The work is based on monotonicity properties of the differential equations or inclusions. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Simulation of Agglomerate Dispersion in Cubic Cavity FlowMACROMOLECULAR THEORY AND SIMULATIONS, Issue 3 2009Mahdi Salami Hosseini Abstract Agglomerate dispersion and deformation is simulated and studied in a cavity flow, as a typical three-dimensional flow field, using Stokesian dynamics and macroscopic flow analysis. The break-up and deformation behaviors of two different agglomerate structures , loose, with fractal dimension FD,=,1.8, and dense, with FD,=,2.6 , are examined in different flow paths. The interparticle forces are calculated using van der Waals and Born forces. Results show that agglomerates with a dense structure break-up through detachment, while ones with a loose structure deform and break into fragments through rupture. It was also found that the rearrangement of particles in the agglomerate can postpone break-up in flow fields where rotation occurs, since it can dissipate stress through rearrangements. [source] | |||||||||||||