High Elastic Deformation Research Articles

Biobased poly(butylene 2,5-furandicarboxylate) and poly(butylene adipate-co-butylene 2,5-furandicarboxylate)s: From synthesis using highly purified 2,5-furandicarboxylic acid to thermo-mechanical properties

To synthesize high quality (co)polyesters derived from 2,5-furandicarboxylic acid (FA), an acetic acid refluxing/pH-swing method was proposed to purify FA. 2-Carboxyl furfural and other impurities were removed completely from FA with this method. Using highly purified FA, biobased polyester poly(butylene furnadicarboxylate) (PBF) and aliphatic-aromatic copolyesters poly(butylene adipate-co-butylene 2,5-furandicarboxy-late)s (PBAFs) were synthesized via melt (co)polycondensation. The (co)polyesters were characterized with GPC, FTIR, 1H NMR, DSC and TGA, and their tensile mechanical properties were also assessed. The copolyesters possess random chain structure, monomer feed ratio-controlled copolymer composition and excellent thermal stability (Td,5% > 340 °C) in full composition range. Both BA-rich and BF-rich PBAFs are crystalline polymers. The crystallizability decreases with composition, up to nearly amorphous at moderate ϕBF (40–60%). PBAFs with ϕBF no more than 50% exhibit obvious high-elastic deformation and rebound resilience, and possess tensile properties (E 18–160 MPa, σb 9–17 MPa, εb 370–910%) comparable to poly(butylene adipate). PBAFs with higher ϕBF behave like nonrigid plastics with low tensile moduli (42–110 MPa), moderate strength (30–42 MPa) and high elongation at break (310–470%). In comparison, PBF is a strong and tough thermoplastic having balanced mechanical properties, namely, much higher tensile modulus (1.9 GPa) and strength (56 MPa) and high elongation at break (260%). It seems necessary and effective to use highly purified FA for synthesizing high performance FA-derived (co)polyesters.

Electrical actuation and shape recovery control of shape-memory polymer nanocomposites

Shape-memory polymers (SMPs) are one of the most popular smart materials due to their light weight and high elastic deformation capability. The synergistic effect of carbon nanofiber (CNF) and carbon nanofiber paper (CNFP) on the electro-actuation of SMP nanocomposites was studied. The electrical conductivity of SMPs was significantly improved by incorporating CNF and CNFP into them. The dynamic mechanical analysis result reveals good thermal stability of SMP nanocomposites even after they were mixed with CNFs. A vision-based control system is designed to precisely control the shape recovery of SMP composites. Any quasi-state shape between the permanent shape and a temporary shape can be achieved by adjusting the electrical energy input. Experimental results demonstrated that (1) compared with the baseline material, the full recovery time of the SMP nanocomposites was decreased by 1000% to less than 80 s; (2) a good repeatability was shown in the developed vision system in 10 experimental trials and the accuracy of the controlled deflection angle of SMPs was within a 5% error bound.

Failure analysis on antistatic coatings on radome

The inelastic and elastic antistatic coatings on the surface of airborne radome failed under the condition of different service duration. The damage of the inelastic coating was more serious than the elastic coating. The failure causes of the antistatic coating on the radome were analyzed by visual inspection, accelerated ageing, falling abrasive test, strength and elongation test, in-layer adhesion test and finite element analysis. The results show that the failure of inelastic and elastic antistatic coatings was caused by particles erosion, and the aging of the coatings accelerated the failure of coatings. There was shear deformation of normal and tangential direction on the coating surface during erosion. The low elasticity, fracture elongation and deformation ability of the inelastic coating made erosion energy concentrate on local areas, resulting in the coating cracking and powdering flake. The elastic coating had better anti-erosion ability than the inelastic coating because of its high fracture elongation and good elastic deformation, so its damage was lighter than the inelastic coating.

TRIBOLOGY OF BIO-INSPIRED NANOWRINKLED FILMS ON ULTRASOFT SUBSTRATES

Biomimetic design of new materials uses nature as antetype, learning from billions of years of evolution. This work emphasizes the mechanical and tribological properties of skin, combining both hardness and wear resistance of its surface (the stratum corneum) with high elasticity of the bulk (epidermis, dermis, hypodermis). The key for combination of such opposite properties is wrinkling, being consequence of intrinsic stresses in the bulk (soft tissue): Tribological contact to counterparts below the stress threshold for tissue trauma occurs on the thick hard stratum corneum layer pads, while tensile loads smooth out wrinkles in between these pads. Similar mechanism offers high tribological resistance to hard films on soft, flexible polymers, which is shown for diamond-like carbon (DLC) and titanium nitride thin films on ultrasoft polyurethane and harder polycarbonate substrates. The choice of these two compared substrate materials will show that ultra-soft substrate materials are decisive for the distinct tribological material. Hierarchical wrinkled structures of films on these substrates are due to high intrinsic compressive stress, which evolves during high energetic film growth. Incremental relaxation of these stresses occurs by compound deformation of film and elastic substrate surface, appearing in hierarchical nano-wrinkles. Nano-wrinkled topographies enable high elastic deformability of thin hard films, while overstressing results in zigzag film fracture along larger hierarchical wrinkle structures. Tribologically, these fracture mechanisms are highly important for ploughing and sliding of sharp and flat counterparts on hard-coated ultra-soft substrates like polyurethane. Concentration of polyurethane deformation under the applied normal loads occurs below these zigzag cracks. Unloading closes these cracks again. Even cyclic testing do not lead to film delamination and retain low friction behavior, if the adhesion to the substrate is high and the initial friction coefficient of the film against the sliding counterpart low, e.g. found for DLC.

Impact of Epoxy Rubbers on the Shape Memory Effect in Epoxy Polymers

This paper examines the potential for the creation of modified epoxy polymer compositions with high elastic-deformation properties possessing a shape memory effect. A methodology for producing and testing these has been determined. Establishes the optimum epoxy polymer compositions to obtain a shape memory effect. Demonstrates the potential for their use in practice.

Consideration of Elastic Tool Deformation in Numerical Simulation of Hydroforming with Granular Material Used as a Medium

The use of high and ultra high strength steels in modern bodies in white raises steadily since the 1980’s. This trend is caused by the consumers’ wish of low fuel consuming cars with an increased passenger’s safety. The processing of these steels brings new challenges e.g. high flow stresses and a low formability at room temperature or high tool loads. These challenges can be resolved by warm forming at temperatures up to 600 °C reducing the flow stresses and increasing formability. For the production of complex parts that can not be produced by deep drawing hydroforming is an appropriate technology which can also help to reduce the number of parts and thus the weight of the body in white. Nowadays typical fluids used for hydroforming are only temperature stable up to about 330 °C so that it is not possible to combine the benefits of warm forming and hydroforming. Media like gases and fluids tend to leakage during the process which can only be avoided by a sealing or high blank holder forces. A new approach is the use of ceramic beads as medium for hydroforming at elevated temperatures. Building up a heatable tool for hydroforming with granular material used as medium makes it necessary to consider thermal conductivity so that there is a need of thick insulation plates. These insulation plates show high elastic deformations affecting the blank holder forces during the forming process. Measurements of the compressibility of these plates and implementation in numerical simulation allow a significant increase of the prediction accuracy of the model. A comparison of real part geometry and numerical results from models with and without consideration of elastic deformation will be given.

Effect of cold severe deformation by multi directional forging on elastic modulus of multi functional Ti + 25 mol% (Ta,Nb,V) + (Zr,Hr,O) alloy

A new and unique beta-titanium alloy (Ti + 25 mol% (Ta,Nb,V) + (Zr,Hr,O) has interesting properties such as low elastic modulus, high strength and high elastic deformability as well as Invar and Elinvar properties. These properties have been successfully realized for the round wire or rods by cold working process but not enough for the sheet made by the cold rolling. To improve the mechanical properties of the alloy sheet, the effect of cold severe deformation on the elastic modulus and microstructure of the alloy sheet was experimentally investigated. The samples were processed using the multi directional forging (MDF) and cold plain rolling. The elastic modulus of the alloy sheet which was cold rolled after MDF was lower than that of cold rolled sheet without MDF. The severe cold plastic deformation by MDF was also effective for obtaining isotropic elastic modulus and very fine grain size (∼1 μm) of sheet after plain rolling. The prototype sheet with low elastic modulus (60–65 GPa), high strength (1100 MPa) and high ductility (total elongation more than 10%) was successfully made in the laboratory test by combining MDF and plain rolling at room temperature.

Study on Subsurface Damage Model of the Ground Monocrystallinge Silicon Wafers

In order to better understand the grinding mechanism, the rough, semi-fine and fine ground silicon wafer subsurface damage models are experimentally investigated with the aid of advanced measurement methods. The results show that the rough ground wafer subsurface damage model is composed of large quantity of microcracks with complicated configurations, high density dislocations, stalk faults and elastic deformation layer. Among them microcracks, dislocations and stalk faults are dominant. Apart from the above damage, the amorphous layer and polycrystalline layer (Si-I, Si-III, Si-IV and Si-XII) exist in the semi-fine ground and fine ground wafer subsurface damage models. The amorphous layer depth firstly increases from rough grinding to semi-fine grinding and then decreases from semi-fine grinding to fine grinding. The damage model can be divided in severe damage part and elastic deformation part with high stress. When the material is removed by ductile mode two parts are all small and the ratio of second part is relatively great.

A new structural system: friction-resistant dry-masonry

A new structural type is proposed and tested: steel-reinforced brick based on distributed unbond prestress theory (SRB-DUP). This is a dry-masonry structure with a friction-resistant stress-transfer mechanism. The elements comprising the entire assembly are not bonded to each other, allowing deconstruction for their easy reuse or recycling. Laboratory tests are reported on the structural performance of walls, beams and columns. Horizontal loading tests of walls and bending tests of beams along their strong axes reveal that the energy-absorbing capacities of both are high. Bending tests on walls and columns along their weak axis showed that both have high elastic deformation capacity. The SRB-DUP structure is a newly proposed type of earthquake resilient construction, different from other structural systems such as earthquake resistant construction, vibration control construction, and construction of vibration isolation. After meeting strict Japanese structural standards, the construction of two experimental houses using SRB-DUP structures was authorized. A new type of brick, with a uniform height achieved by covering it with fly-ash slurry mortar, has also been developed. Cet article présente un nouveau type de structure ainsi que les essais auxquels il a été soumis: il s'agit d'une brique renforcée à l'acier conçue selon la théorie du précontraint non collé distribué (SRB-DUP). C'est une structure en maçonnerie sèche avec un mécanisme de transfert des contraintes résistant au frottement. Les éléments qui composent l'ensemble ne sont pas collés les uns aux autres, ce qui permet et facilite leur déconstruction et leur réutilisation ou leur recyclage. L'article rend compte de tests menés en laboratoire sur les performances structurales de murs, de poutres et de colonnes. Des tests de charge horizontale menés sur des murs et des tests de flexion menés sur des poutres le long de leur axe fort révèlent que les capacités d'absorption d'énergie sont élevées dans les deux cas. Les tests de flexion sur des murs et des colonnes le long de leur axe faible montrent que dans les deux cas, la capacité de déformation élastique est élevée. La structure SRB-DUP est un nouveau type proposé de construction dont la résilience permet de résister aux séismes et qui est différent des autres systèmes structuraux comme les constructions antisismiques, les constructions antivibratoires et la construction d'amortisseurs de vibrations. Conforme à des normes structurales strictes japonaises, la construction de deux maisons expérimentales utilisant des structures SRB-DUP a été autorisée. Un nouveau type de brique, avec une hauteur uniforme obtenue par recouvrement d'un mortier-coulis à base de cendres volantes, a également été développé. Mots clés: technologie alternative, brique, déconstruction, maçonnerie sèche, conception antisismique, innovation, construction en maçonnerie, réutilisation

High pressure elastic and plastic deformations of silica: In situ diamond anvil cell Raman experiments

Normal silica glass is usually referred to as low density amorphous silica as it can be converted to high density amorphous silica by a hydrostatic pressure (polyamorphic transition). In this work in situ Raman experiments are performed in a diamond anvil cell up to 18GPa. The pressure effects on the structure of silica after successive compression decompression experiments are analyzed. The mode Grüneisen parameters corresponding to the elastic compression of high density amorphous silica are obtained and compared with those of normal silica. A reorganization of the high density amorphous silica below 3GPa is evidenced.

P-29 Mechanical characteristics of spectacle frames made of gum metal

Most metal frame spectacles are now made of titanium alloy. Recently, however, frames made of gum metal have started to be produced. Gum metal is a new material having a low Young's modulus, high strength and high elastic deformation. This report compares the mechanical characteristics of the full-rim and rimless spectacles made of gum metal on the market and the conventional titanium frames by using recent measuring and analytical techniques. Using the finite element method (FEM), the authors preformed detail analysis of the mechanical characteristics of these frames. Consequently, gum metal frames were found to fit slightly better than titanium ones. Irrespective of the material they are made from, however, rimless spectacles have greater risk of lens damage and require a structure that can effectively mitigate the temple opening force by the improvement of end pieces and hinges.

Stability-Based Spindle Design Optimization

Prediction of stable cutting regions is a critical requirement for high-speed milling operations. These predictions are generally made using frequency-response measurements of the tool-holder-spindle set obtained from a nonrotating spindle. However, significant changes in system dynamics occur during high-speed rotation. In this paper, a dynamic high-speed spindle-bearing system model is elaborated on the basis of rotor dynamics prediction and readjusted on the basis of experimental modal identification. The dependency of dynamic behavior on speed range is then investigated and determined with accuracy. Dedicated experiments are carried out in order to confirm model results. They show that dynamic effects due to high rotational speed and elastic deformations, such as gyroscopic coupling and spin softening, have a significant influence on spindle behavior. By integrating the modeled speed-dependent spindle transfer function in the chatter vibration stability approach of Altintas and Budak (1995, CIRPS Ann, 44(1), pp. 357–362), a new dynamic stability lobe diagram is predicted. Significant changes are observed in the stability limits constructed using the proposed approach and allow accurate prediction of cutting conditions to be established. Finally, optimization studies are performed on spindle design parameters in order to obtain a chatter vibration-free cutting operation at the desired speed and depth of cut for a given cutter.

Polycarbonate and a Polycarbonate-POSS Nanocomposite at High Rates of Deformation

Polymeric materials are known to exhibit strong time-dependent mechanical behavior, as evidenced by rate-dependent elastic moduli, yield strength, and post-yield behavior. The nature of the rate sensitivity is found to change between different temperature regimes as various primary (α) and secondary (β, γ, etc.) molecular mobility mechanisms are accessed. The ability to tailor these molecular-level mechanics through the incorporation of nanoscale particles offers new opportunities to design polymer-based material systems with different behaviors (elastic, yield, post-yield) in different frequency∕rate regimes. In this study, the macroscopic rate-dependent mechanical behavior of one particular polymer nanocomposite—polycarbonate compounded with TriSilanolPhenyl-POSS® particles—is compared with that of its homopolymer counterpart. The experimental and theoretical techniques follow those established in previous research into the rate-dependent mechanical behavior of amorphous homopolymers over a wide range of strain rates. On the experimental side, dynamic mechanical analysis tension tests were used to characterize the viscoelastic behavior of these materials, with focus on the rate-dependent shift of material transition temperatures. Uniaxial compression tests on a servohydraulic machine (10−3s−1to0.3s−1) and an aluminum split-Hopkinson pressure bar (1000s−1to3000s−1) were used to characterize the rate-dependent yield and post-yield behavior. The behaviors observed in these experiments were then interpreted within the theoretical framework introduced in previous work. It is concluded that, for this particular material system, the POSS has little influence on the polycarbonate α regime. However, the POSS clearly enhances the mobility of the β motions, significantly reducing the resistance to high rate elastic and plastic deformation. Furthermore, it is shown that the continuum-level constitutive model framework developed for amorphous homopolymers may be extended to this polymer nanocomposite material system, simply by accounting for the reduced deformation resistance in the β process.

Elastic Deformation Behavior of Multi-Functional Ti–Nb–Ta–Zr–O Alloys

We investigated the effect of cold working on the elastic properties of a newly developed multi-functional β titanium alloy, GUM METAL, using in-situ XRD and EBSP analysis. Mechanical and physical properties are changed dramatically by cold working. The alloy has a low elastic modulus (40GPa), high strength (more than 1100MPa), high elastic deformability (2.5%) and super-plastic like deformability at room temperature without work hardening. The elastic behavior of the cold worked specimen shows non-linearity, with the gradient of the stress-strain curve in the elastic region continuously decreasing with a stress increase. In-situ XRD measurements during tensile loading show that all β peaks shift monotonically to higher 28 angles with increasing tensile strain up to 2.7%. This result suggests that the elastic behavior in the alloy is not accompanied by phase transformations, such as stress-induced a. Additionally, EBSP analysis reveals that the deformation mode in the alloy does not relate to {112} or {332} twinning. The microstructure of the alloy during deformation is characterized by localized distorted regions ranging in size from several tens of micrometers to submicrometers, with elastic strain located hierarchically in the alloy. It is likely that this microstructure is attributable to its elastic anomaly, which arises at this specific alloy composition of the multifunctional alloy. The above elastic anomaly in the alloy seems to contribute to the development of the unique microstructure during plastic deformation, as well as to its macroscopic elastic behavior.

Inversion Features of the High-Elastic Deformability of Epoxy Polymers

Inversion Features of the High-Elastic Deformability of Epoxy Polymers

In situ electron energy-loss spectroscopy on carbon nanotubes during deformation

Local modifications to the electronic structure during the bending deformation of carbon nanotubes are probed by in situ electron energy-loss spectroscopy. Reversible changes in the carbon K(1s) absorption near-edge fine structures are detected at the inner bending side for a multiwalled carbon nanotube and attributed to the curvature-induced electronic structure alteration of the graphite layers. More intensive changes in the carbon K edge across an abrupt kink of a bundle of single-walled carbon nanotubes are observed over a region of 4–5 nm around the kink. These results clearly demonstrate the unique deformation behavior of the carbon nanotube, namely, a high elastic deformability and variable electronic properties associated with bending.

Development of High Impact Acrylic Graft PVC.

PVC has fine mechanical properties, but it also shows poor impact strength in low temperature region. We have succeeded in designing new PVC materials grafted to acrylic rubber particles aiming at strengthening surface bonding, dispersing particle homogeneously and achieving high speed elastic deformation of the particles on the basis of the Craze theory. The acrylic graft PVC gives high impact energy absorption. We have discovered the correlation among the surface of molding products and flow properties of melting resin, relaxation modulus, shear stress on the die wall, adhesion and slip-stick behavior, and consequently stabilized processing.

Some features of relationships between physico-chemical and technological parameters in the orientation of polyethylene terephthalate films

The limits and conditions of manifestation of the various mechanisms of plastic and elastic deformation have been determined for PETP films on the basis of data on tensile stress and degrees of orientation. The activation energy and the entropy change during stretching of the films have been estimated. In the case of deformation under a time-temperature regime, when a structural transition of high-elastic deformation occurs, the PETP film may be regarded as a fluctuational network containing from five to seven chain units between the crosslinks.

Thermodynamics of high-elastic deformation of filled polyvinylchloride

A study was made of the effect of a number of fillers of different types and surface on thermodynamics of high-elastic deformation of PVC. In their effect on thermodynamic stress components the fillers studied form two groups: 1-polar active filler influencing both energy and entropy stress components; 2-nonpolar filler which cause basically conformation changes in the polymer. In small amounts with slight deformation fillers of group 1 contribute to structure formation of PVC, with high concentrations the filler “inhibits” structure formation. Fillers of group 2 do not influence process of structure formation during deformation of PVC.

The development of defects in plasticized polyvinylchloride

It has been ascertained by several different methods that the heating of PVC may lead to the development of defects. The appearance of micro- and macrodefects in plasticized PVC is the result of high elastic deformations and stresses remaining after the fabrication of specimens.