Plasticity Modulus Research Articles

Effects of Annealing Temperature on the Microstructure and Mechanical Properties of Electrodeposited Ni-Fe Alloy Foils

AbstractThe plasticity, elastic modulus and thermal stability restrict the applications of electrodeposited nanocrystalline Ni-Fe alloy foils. To improve its mechanical properties, the electrodeposited Ni-Fe alloy foils were heat treated within the temperature 900–1,150 °C. The microstructure and texture of the samples were further analyzed with a combination of SEM, XRD and EBSD. The experimental results indicated that the electrodeposited Ni-Fe alloy foil had poor mechanical properties at about 1,000 °C, which was mainly attributed to the development of a mixed grain microstructure. At 900–950 °C, the plastic and elastic modulus were greatly improved, which were owed to the uniformed microstructure and the decrease of structure defects. At 1,050–1,150 °C, the degree of the mixed grain microstructure decreased, resulting in improved plasticity and higher elastic modulus. However, the strength of the foil obviously decreased, which was mainly associated with the increase of the average grain size.

Bendability characteristics of wood lamellae in plastic region

This article examines the effect of different factors (material thickness, degree of densification and number of loading cycles) on the selected bending characteristics of European beech (Fagus sylvatica L.) and European aspen (Populus tremula L.). The bending characteristics, including bending strength, plasticity potential and modulus of plasticity, were measured using three-point bending. Results of the four-factor analysis demonstrate that each bending characteristic is affected differently by the given factors. The bending strength, which was higher in beech wood than in aspen wood, increased along with the degree of densification. Cyclic loading had no significant effect on the bending strength. Although material thickness had some statistical significance, its effect was not unequivocal. The modulus of plasticity was significantly affected only by the wood species and material thickness. Higher modulus of plasticity values were achieved in beech wood than in aspen wood. The modulus of plasticity gradually decreased with an increase in material thickness. Again, the cyclic loading had no significant effect. The degree of densification also proved to be insignificant, especially in aspen wood. In beech wood a somewhat greater difference between various degrees of densification was found.

Investigations of Titanium Implants Covered with Hydroxyapatite Layer

Abstract To reduce unfavorable phenomena occurring after introducing an implant into human body various modifications of the surface are suggested. Such modifications may have significant impact on biocompatibility of metallic materials. The titanium and it's alloys are commonly used for joint and dental implants due to their high endurance, low plasticity modulus, good corrosion resistance as well as biocompatibility. Special attention should be given to titanium alloys containing zirconium, tantalum and niobium elements. These new generation alloys are used by worldwide engineering specialists. The experiments were performed with hydroxyapatite layer on titanium specimens with the use of electrophoresis method (different voltage and time).

Effect of annealing on the structure and properties of Al–Li–Cu–Zr–Sc–Ag alloy subjected to severe plastic deformation

Methods of transmission electron microscopy and measurements of microhardness were used to study structural and phase transformations upon low-temperature annealing (150°C) in the aluminum–lithium alloy 1469 with Ag addition subjected to severe plastic deformation by high-pressure torsion. It has been shown that the nature of the nanocrystalline structure that forms upon annealing is determined by the competing processes of recrystallization and the decomposition of the supersaturated solid solution. The effect of the structural state of the annealed alloy on the level of mechanical properties (nanohardness, modulus of elasticity, their ratio, and plasticity) is discussed.

Raman spectroscopy monitors adverse bone sequelae of cancer radiotherapy

Raman spectroscopy provides information on bone chemical composition and structure via widely used metrics including mineral to matrix ratio, mineral crystallinity and carbonate content, collagen cross-linking ratio and depolarization ratios. These metrics are correlated with bone material properties, such as hardness, plasticity and Young's modulus. We review application of Raman spectroscopy to two important irradiated animal models: the mouse tibia, a model for damage to cortical bone sites including the rib (breast cancer) and to healthy tissue adjacent to extremity sarcomas, and the rat mandible, a model for radiation damage in head and neck cancer radiotherapy. Longitudinal studies of irradiated mouse tibia demonstrate that radiation-induced matrix abnormalities can persist even 26 weeks post-radiation. Polarized Raman spectroscopy shows formation of more ordered orientation of both mineral and collagen. At 8 weeks post-radiation, irradiated rat hemimandible exhibits transient hypermineralization, increased collagen cross-linking and decreased depolarization ratios of mineral and collagen. A standard radioprotectant, amifostine, mitigates rat mandible radiation damage, with none remaining detectable 18 weeks post-radiation. Already a powerful tool to monitor radiation damage, Raman spectroscopy may be important in development of new radiotherapy protocols and radioprotective agents. Further in vivo studies of radiation effects on the rodent models are underway, as are development of methodologies for eventual use in human subjects.

Micro scale laser shock forming of pure copper and titanium sheet with forming/blanking compound die

A new process fabricating micro parts of thin metal foils by laser shock waves with forming/blanking compound die is reported in this article, in which flexible rubber material was used as the soft punch to act on the thin metal sheet. Systematic studies were carried out experimentally on the process with different laser energies and materials. The formed parts were examined in terms of their morphology, surface roughness, forming depth and mechanical properties (including nanohardness, plasticity and elastic modulus) characterized by nanoindentation test. According to the results, the ablation states of confinement medium and the surface roughness of the different regions change with energies. Additionally, the proper energies are necessary to form complex parts and the forming process can be applied to manufacture parts with good surface quality. What׳s more, the nanoindentation test results showed that the nanohardness, plasticity and elastic modulus of material were increased after impact. The increase in nanohardness and plasticity can attribute to higher stiffness of the parts. The enhanced elastic modulus indicates an increased stiffness of the parts, providing an evidence for the reduced spring back of copper during laser shocking.

Buckling and post-buckling of gradient and nonlocal plasticity columns experiencing softening

The buckling and the post-buckling behaviors of a perfect axially loaded column are analytically investigated through a global bilinear moment–curvature elastoplastic constitutive law. Three plasticity cases are studied, namely the linear hardening plasticity law, the perfect elastoplastic case and the softening case. The applications of such a study can be found in various structural engineering problems, including reinforced concrete, steel, timber or composite structures. It is analytically shown that for all kinds of elastoplastic behaviors, the plasticity phenomena lead to a global softening branch in the load–deflection diagram. The propagation of the plasticity zone during the post-buckling process is analytically characterized in case of linear hardening or softening plasticity laws. However, it is shown that the unphysical elastic unloading solution necessarily occurs in presence of local softening moment–curvature constitutive law. A nonlocal plasticity moment–curvature softening law is then used to control the localization branch in the post-buckling stage. This nonlocal plasticity law includes the explicit and the implicit gradient plasticity law. Higher-order plasticity boundary conditions are derived from an extended variational principle. Some parametric studies finally illustrate the main findings of this paper, including the plasticity modulus effect on the post-buckling behavior of these plasticity structural systems.

Inter-Granular Phase Formation during Reactive Diffusion of Gallium with Al Alloy

Peculiarities of formation of solid-state joining of the parts for bimetallic heat exchanger are considered. For solid-state activation of the surfaces, being joined, the layer-activator (liquid gallium) is used. Inter-granular segregation of an activator along the grain of the alloy-matrix is rapid and deep, which leads to polygonal structure in the diffusion zone. A negative fact for such joints is the brittleness of materials after intermetallic phase transformation of the chemical elements of alloy-matrix with gallium. The joint formed with an increasing of volume of the diffusion zone after rotation of newly formed phases at growth. Rotation of grains leads to emergence of high local internal stresses. Excess of an activator may be a reason for generation and distribution of main cracks. Indentation allows recording an abnormal decrease of the micro-hardness in grain boundary area. Obtained data of the Young's modulus, micro-hardness and coefficient of plasticity, with spectral mapping of chemical elements and phase analysis are allowed to exactly specify structural components that are the initiators of the materials stress state and are the reason for local cracks.

β-Type Zr–Nb–Ti biomedical materials with high plasticity and low modulus for hard tissue replacements

In order to develop new biomedical materials for hard tissue replacements, Zr–20Nb–xTi (x=0, 3, 7, 11 and 15) alloys with required properties were designed and prepared by using the vacuum arc melting method for the first time. Phase analysis and microstructural observation showed that all the as cast samples consisted of equiaxed β-Zr phase. The mechanical properties and fracture behaviors of the Zr–20Nb–xTi alloys have been analyzed. It is found that these alloys exhibit high plasticity, moderate compressive strength (1044–1325MPa) and yield stress (854–1080MPa), high elastic energy (12–20MJ/m3) and low Young's modulus (28–31GPa). This good combination of mechanical properties makes them potential biomedical materials for hard tissue replacement.

Experimental Analysis of Steel Plasticity Parameters during Quenching

The paper presents the results of longitudinal investigations of transformation plasticity, kinetic plasticity, elastic-plastic strain and auto deformation of different grades of steel during quenching. A special device was used to evaluate transformation plasticity and determine the maximum normal bending stress, modulus of transformation plasticity for high alloyed and high corrosion resistance steel. Other targets of experiments were to determine relations between magnitude of normal bending stresses and plastic deformation of test pieces, to examine influence of hardening temperature on the transformation plasticity, to calculate modulus of transformation plasticity Etp. As a complimentary survey we study the mechanical behaviour of high chromium and medium chromium steels during quenching. Understanding phenomenon of steel behaviour during quenching it is possible to renovate and restore the details and components deformed during exploitation, for production of steels with high formability, and to predict properties of steel.

Effect of Oil Contamination on Particle Size Distribution and Plasticity Characteristics of Lateritic Soil

This paper presents the results of a laboratory study on the effect of oil contamination on the particle size distribution and plasticity characteristics of lateritic soil. The soil was artificially contaminated with a maximum 6 % oil content by weight of dry soil. The results show that there was a substantial reduction in the amount of fines content with higher amounts of oil in the soil matrix. The percentage of fine fraction in the natural soil was 86.9 % and on contamination with maximum 6 % oil content by weight of dry soil at optimum moisture content (OMC) the fine fraction reduced to 1.4 %. The plasticity index decreased from 16.0 to 8.5 % when contaminated with 6 % oil content by weight of dry soil. The plasticity modulus (PM), plasticity product (PP), the shrinkage modulus (SM) and the grading modulus (GM) decreased with increasing amounts of oil content.

Amoxicillin-Loaded Sponges Made of Collagen and Poly[(methyl vinyl ether)-co-(maleic anhydride)] for Root Canal Treatment: Preparation, Characterization and In Vitro Cell Compatibility

The difficulty of eliminating Enterococcus faecalis and other bacteria infecting dental root canals makes it desirable to develop formulations capable of sustained release of antibiotics within the canal. With this function in view, in this work we compared the mechanical, drug release and biocompatibility properties of amoxicillin-loaded collagen (CL) and CL complexed with poly[(methyl vinyl ether)-co-(maleic anhydride)] (PVMMA), with or without glutaraldehyde (GTA) or the natural product genipin (GN) as cross-linker. Collagen was not denatured by complexation with PVMMA. Only CL–PVMMA–GN sponges did not disintegrate during 7 days exposure to cell culture medium (un-cross-linked CL disintegrated within 24 h and un-cross-linked CL–PVMMA within 4 days), and CL–PVMMA–GN sponges also exhibited the most appropriate combination of mechanical properties (hardness, modulus of deformability and plasticity). CL–PVMMA–GN sponges absorbed aqueous medium faster than other cross-linked formulations, but their maximum uptake was less; and drug release from CL–PVMMA–GN sponges tended to be faster than from any other, except un-cross-linked CL–PVMMA, maximum release taking about 4 days. No formulation significantly altered the viability of L929 fibroblast-like mouse connective tissue cells, but cells growing on sponges showed signs of non-adherence. It is concluded that genipin-cross-linked CL–PVMMA sponges merit further investigation as antibiotics vehicles and aids to tissue regeneration in the dental root canal.

Microstructures and properties of biomedical TiNbZrFe β-titanium alloy under aging conditions

A metastable β-titanium alloy Ti–28Nb–13Zr–0.5Fe (TNZF alloy for short) was designed for implant biomedical application. The forged specimens were solute-treated at 850 °C followed by water quenching and then aged at 350 °C, 450 °C, and 550 °C for 2–6 h in order to evaluate the effect of phase transformation during ageing on the biomechanical compatibility of the alloy. The quenched microstructure consists of lath α″ martensite and β phase. A large quantities of shuttle-like ω phase precipitate at 350 °C, leading to the drastic increase of strength and elastic modulus and the decrease of plasticity. Ageing at 450 °C for 4 h, small amount of elliptic ω phase and dot α phase precipitate from β matrix. With increasing ageing time α precipitations begin to coarsen and precipitation free zones (PFZs) form around prior β grain boundaries. Needle-like α phase precipitates on grain boundaries and intra-grains when aged at 550 °C. Both PFZs and grain boundary α precipitates are prone to bring about the intergranular fracture and thus have adverse effects on the tensile strength and fracture plasticity. The quenched microstructure has good combination properties of high strength, high plasticity and low elastic modulus.

Phase Transformation of Biomedical Metastable β Titanium Alloy during Aging

A kind of metastable β type Ti-30Nb-13Zr-0.5Fe (wt.%) alloy for biomedical application was newly designed and developed. In order to exam the phase transformation during aging and its effects on the mechanical properties, the alloy was β solubilized and aged at 350°C-550°C for 4 hours. The microstructures were observed by OM and TEM, and the phase structures were identified by XRD. The tensile tests were performed with various aged microstructures. The results show that a lot of ω phase precipitates during aging at 350°C, leading to the increase of strength and elastic modulus and drastic decrease of plasticity. Aging at 450°C, dot α phase uniformly precipitates from metastable β phase. The good combination of high strength 、high plasticity and low elastic modulus was obtained under this aging condition. With increasing aging temperature and aging time α precipitations coarsen and precipitation free zones (PFZ) along prior β grain boundaries form, which are the main reasons to lower the strength and plasticity.

Transformation Plasticity of Hot-Die Steel During Hardening

The paper presents the results of investigations of transformation plasticity of hot-die steel (high temperature–resistant steel used in high-temperature deforming) during hardening. A special device was used to evaluate transformation plasticity and determine the maximum normal bending stress, modulus of transformation plasticity for medium alloyed and medium carbon steel.

Properties of Ironstone Lateritic Gravels in Relation to Gravel Road Pavement Construction

A laboratory investigation was conducted to determine properties of five samples of ‘oolitic ironstone’ lateritic gravel aggregates which are relevant to their use as road construction materials. Measured values of physico-chemical, physico-mechanical as well as index properties and compaction characteristics are similar to those of other lateritic, gravels occurring in West Africa which are used in road pavement applications. These lateritic clayey gravels have good workability as engineering construction materials and are rated fair to good as road aggregates in terms of probable in-situ behaviour based on water absorption values. Relationships between maximum dry unit weight and optimum moisture content as well as those between California bearing ratio and some derived soil parameters such as grading modulus, plasticity product or plasticity modulus can be described using a third-order polynomial function. The maximum dry unit weight has a bimodal frequency distribution and can be predicted from logarithm to base 10 of compaction energy with fairly good accuracy.

Design of Compacted Lateritic Soil Liners and Covers

Laboratory tests were conducted on three lateritic soil samples to illustrate some pertinent considerations in the design of compacted lateritic soil liners and covers. The three design parameters investigated are hydraulic conductivity, desiccation-induced volumetric shrinkage, and unconfined compressive strength. Test specimens were compacted at various molding water contents using four compactive efforts. The compaction conditions were shown to have some relationship with soil compaction using either the plasticity modulus or the plasticity product (i.e., clay index). For construction quality assurance purposes, the traditional approach was compared with the modern criterion. Deficiencies associated with the traditional approach for soil liners found in literature also apply to lateritic soils. Overall acceptable zones were constructed on the compaction plane to meet design objectives for hydraulic conductivity, volumetric shrinkage strains, and unconfined compressive strength. The line of optimums was identified as a suitable lower bound for overall acceptable zones of lateritic soils. The volumetric shrinkage strain was also identified as the second most important design parameter for lateritic soils. The shapes of the acceptable zones were affected by the fines contents of the soils.

Effect of cross-link density on strain gradient plasticity in epoxy

The variation of specific strain gradient plasticity modulus in epoxy has been examined as a function of cross-link density in epoxy. Cross-link density is controlled by varying the hardener content in the epoxy and the moduli are determined from nanoindentation data. Nanoindentation revealed that hardness increased with decreased indent depth. Specific strain gradient plasticity moduli and the characteristic lengths were found to increase with cross-link density in the epoxy. Data analysis revealed that the characteristic length is inversely proportional to the square root of the kink density. Consequently, material that has a higher cross-link density will have a higher specific strain gradient modulus and a lower kink density at yield.

Physicochemical mechanisms controlling the periodic release of flammable gases from hanford tanks

AbstractHanford tanks contain more than 60 million gallons of high‐level wastes produced by decades of extracting plutonium from irradiated uranium fuel. The wastes were concentrated to a thick slurry consistency by evaporation prior to storage to minimize space. The resulting concentrated waste properties introduced unanticipated, detrimental conditions affecting workers' and the public's health and safety and involving the release of potentially flammable gases. The released gases consist primarily of hydrogen, nitrous oxide, and ammonia.Dilution and sluicing were initially proposed to mitigate the flammable gas safety conditions. As a result of evaluations, the mechanisms and conditions that are thought to control the accumulation and spontaneous release of flammable gases were identified and confirmed. The technical rationale was established for developing operational approaches to mitigate the periodic generation of flammable gases in existing tanks and to avoid any reoccurrence of this serious safety problem during future waste management activities. The chemistry of the two highest risk tanks was examined to test the potential for reversing the conditions causing gas buildup and the consequences of sluicing without appropriate chemical conditioning. The identified mechanisms apply equally to the remaining flammable gas tanks at Hanford as well as to other waste tanks in the DOE complex, particularly those at Savannah River. Passive means of mitigating the flammable gas condition require less than 1:1 dilution, and sluicing wastes from tank 106‐C can be accomplished without creating a flammable gas condition.Carbonate equilibria reactions and their effect on aluminum speciation are largely overlooked and provided the key for explaining the episodic release of flammable gases from tank wastes. The reaction of atmospheric carbon dioxide with a sodium hydroxide‐rich waste solution produces carbonate precipitates. More importantly, this reaction lowers the pH of the waste and precipitates aluminum hydroxide as a gel. The wastes contain substantial amounts of complexing agents such as ethylene diamine tetraacidicacid (EDTA), hydroxy ethylene diamine triacidic acid (HEDTA), and their degradation products. These complexing agents stabilize the aluminum hydroxide gel together with chromium, manganese and iron hydroxides, and oxybydroxides under the resulting pH conditions. These complex species may coprecipitate and accumulate as a metastable layer in the middle and lower levels of th tank. The complexed aluminum hydroxide acts as a binding agent trapping other particulates in a microcrystalline mat. Microcrystalline particles such as sodium nitrite provide the structural strength for the mat.Once the gas accumulation below the gel layer achieves a critical buoyancy sufficient to rupture the microcrystalline mat, a gas release event occurs. The cycle of gas buildup and release continues each time the buoyancy of the trapped gas exceeds the hydrostatic pressure and the gels' plasticity modulus. Stokes Law predicts a particle settling rate in the tank of less than 50 days, well within the bistorical periodicity of GREs.Laboratory tests, forming the basis of a recent patent application, verify that large quantities of complexed aluminum hydroxide gel are produced by passing carbon dioxide through simulated waste solutions (Hobl, 1993) equivalent to those found in tank 101‐SY. It was confirmed that a simple adjustment of pH witll redissolve the gel, thereby reducing viscosity and safely facilitating continuous flammable gas release. Additional experiments were undertaken to provide a basis for understanding the role of complexed aluminum hydroxides in the CO2/NaOH/Al(OH)3 (complexing agents)/NaAlO2 system.This article examines a plausible mechanism for the periodic release of flammable gas and considerations for: (1) remediating existing flammable gas tanks through a combination of chemical treatment and mixer pumps; (2) diluting, combining, retrieving, and storing wastes; (3) preventing clogging of transfer lines; (4) sludge and soil washing; and (5) cribs, ponds, basins, and ground‐water cleanup. This study provides a singificant breakthrough for tank waste management by explaining key mechanisms controlling episodic release of flammable gases. The breakthrough provides the bases for removing the tanks classified as flammable gas from the wathclist and has broad operational applications with a potential for billions of dollars in cost savings.

A practical stress-strain-strain rate-temperature constitutive relation of the power form

Many technical processes have been analysed using a double-power constitutive relation of the form: σ = B σ ϵ n ϵ ̇ m Such an equation can be used, for example, in the simulation of many bulk metal-forming processes, in forming-limit diagrams, and in many other situations. The problem, however, arises when this constitutive relation has to be used at different temperatures. Earlier analysis has indicated that in such relations, material constants such as the plasticity modulus B(T), the strain-hardening exponent n(T) and the logarithmic rate-sensitivity m(T) are temperature-dependent. A new approximation for these parameters as a function of temperature is proposed. Within the framework of temperature generalization all material constants are identified for three materials: commercially pure polycrystalline aluminium, OFHC copper and steel. Special attention is paid to 1018 cold-rolled steel (1018 CRS) where the response of the material to plastic deformation is more complicated. These three materials are analysed over a wide range of temperatures: θ < T < T m/2 and a wide range of shear strain rates: 5×10 −4 s −1 < Γ ̇ < ∼5×10 2 s −1 , where T m is the melting temperature. In addition, the generalized form of the constitutive relation is discussed for the whole temperature range, i.e. θ < T < T m . For the purpose of demonstration, several characteristic material responses during plastic deformation at different temperatures and different strain rates have been simulated using a computer program and computer graphics: the program is available from the author. Results are shown in the form of plots, along with experimental points. The predictions of the calculations are confirmed by experimental data.