Young's Modulus Change Research Articles

A mechanical analysis of metallic tritide aging by helium bubble growth

A simple mechanical model is proposed for the aging of a metallic tritide. The material is assumed to be elastic–power law viscoplastic. Part of the helium atoms generated by tritium decay form spherical bubbles that weaken the elastic moduli of the overall material. By contrast, others can be stored in solid solution in the matrix and are likely to increase the moduli. Two variants of the model are compared, assuming either instantaneous or finite rate diffusion of helium. They predict globally similar evolutions of the gas pressure inside the bubbles, the geometrical parameters (bubble radius, overall swelling), as well as the matrix and overall elastic moduli. The results are in good agreement with atomistic calculations of the pressure evolution. Furthermore, recent experimental measurements of the Young modulus changes during aging are better reproduced when He diffusion rate is finite, thus supporting the second variant of the model.

Semi-inverse Method for Vibration and Buckling of Axially Functionally Graded Beams

In this study, vibration and buckling of axially functionally graded simply supported beams is analyzed by using the semi-inverse method. Euler—Bernoulli beam theory was used in the analysis. By using a pre-specified frequency and buckling loads, variation of the Young's modulus in the axial direction is obtained in terms of the axial coordinate. It is found that the Young's modulus changes exponentially between the edges of the beam for the vibration and buckling problem.

Variation of the mechanical properties of PMMA to suit osteoporotic cancellous bone

Poly(methyl methacrylate) (PMMA) is by far the most frequently used bone substitute material for vertebroplasty. However, there are serious complications, such as cement leakage and an increased fracture rate of the adjacent vertebral bodies. The latter may be related to the mechanical properties of the augmented segment within the osteoporotic spine. A possible counter-measure is prophylactic augmentation at additional levels, but this aggravates the risk for the patient. Introduction of pores is a possible method to reduce the inherent high stiffness of PMMA. This study investigates the effect of porosity on the mechanical properties of PMMA bone cement. Different fractions of a highly viscous liquid were mixed into the PMMA during preparation. An open-porous material with adjustable mechanical properties resulted after removal of the aqueous phase. Different radiopacifiers were admixed to investigate their suitability for vertebroplasty. The final material was characterized mechanically by compressive testing, microscopically and radiologically. In addition, the monomer release subsequent to hardening was measured by means of gas chromatography. The Young's modulus in compression could be varied between 2800 ± 70 MPa and 120 ± 150 MPa, and the compression ultimate strength between 170 ± 5 MPa and 8 ± 9 MPa for aqueous fractions ranging between 0 and 50% of volume. Only a slight decrease of the Young's modulus and small changes of ultimate strength were found when the mixing time was increased. An organic hydrophilic and lipophilic radiopacifier led to a higher Young's modulus of the porous material; however, the ultimate strength was not significantly affected by adding different radiopacifiers to the porous cement. The radiopacity was lost after washing the aqueous phase out of the pores. No separation occurred between the aqueous and the PMMA phase during injection into an open porous ceramic material. The monomer released was found to increase for increasing aqueous fractions, but remained comparable in magnitude to standard PMMA. This study demonstrates that a conventional PMMA can be modified to obtain a range of mechanical properties, including those of osteoporotic bone.

Low- k dielectrics on base of silicon carbon nitride films

Thin silicon carbonitride films were synthesized by PECVD using siliconorganic compound as single-source precursor within a temperature range of 373–623 K. IR and Raman spectroscopy, AES, XPS, ellipsometry, XRD using the synchrotron radiation, EDS, SEM, AFM, measurements of electrophysical, mechanical characteristics and optical properties were applied to study their physicochemical and functional properties. It was shown that low temperature films are low- k dielectrics with the following characteristics: a dielectric constant of 3.0–7.0, specific resistance, ρ = 10 13–10 16 Om × cm, E dielectric breakdown ∼ 1 MV/cm, surface state density N ss ∼ 2.4·10 11 cm − 2 ·eV − 1 and fixed charge density of about 1.6 × 10 11 cm − 2 . The bandgap of the films changes from 5.35 up to ∼ 3.30 eV. Obtained films are very flat and smooth, root mean square roughness R ms equals to ∼ 0.5–1.0 nm. Microhardness of these films changes from 1.9 up to 2.4 GPa, and Young's modulus changes from 12.2 up to 15.9 GPa.

Change of Young's Modulus of Cold-Deformed Aluminum AA 1050 and of AA 2024 (T65): A Comparative Study

The knowledge of some mechanical properties of materials and their changes with thermal treatments and/or mechanical treatments are essential to obtain the best results during simulation of processes. In this paper, changes of Young's modulus at room temperature of colddeformed aluminum AA1050 carried out in a tension machine and changes of Young’s modulus and Poisson’s ratio of AA2024 (T6 and T65) have been determined. The elastics constants have been measured by the ultrasound technique in AA2024 alloy and by tensile test in AA1050. In this alloy, the Young's modulus (E) diminishes during the first step of deformation and then increases with the successive cold working. Changes in Young's modulus measured are around 6-8%. In AA2024, the Young's modulus change is about 3% between the annealed and quenched alloy (minimum value); during aging the E parameter increases with respect to quenching. These changes are correlated with the structural changes during thermal treatments. In AA2024, the E parameter remains almost constant during cold-working after the aging treatment. Poisson’s ratio of this alloy remains almost constant in all the treatments. These results are also correlated with the dislocations arrangement in both materials. This behaviour is also compared with cold-deformed pure iron in a tensile test. These results confirm that aluminum AA1050 present similar behaviour than it was observed for pure iron.

Characterization of network morphology in anion binding hydrogels used for wastewater remediation

This work reports on morphological features of hydrogels, which have been used for the ultimate removal and recovery of nutrient and toxic anions from wastewater effluents. The sorbent used was crosslinked polyamine (PAA·HCl) polymeric hydrogels. The surface topography and morphology of these hydrogels were characterized by tapping mode atomic force microscopy. The change of the gel surface in response to the degree of crosslinking was observed via phase imaging. The crosslinker amount affects both the crosslink density and uniformity. Phase images were recorded at moderate to hard tapping conditions ( A sp/ A 0=0.3–0.6) and related to surface stiffness variations associated with Young's modulus ( E) change. Bright ellipse and sponge-like domains of submicrometer scale were found on irregularly crosslinked gels, while the gel topography was uniform in gels that were prepared with a more regular distribution of crosslinks. The observed AFM domain size was strongly affected by the gel's degree of crosslinking.

Investigation on PA/PP mixture properties by means of DMTA method

Polymer mixing is presently one of the most effective and the most intensely developing methods of physical properties modification for polymers. Mixing polymers one can modify certain properties, mainly physical. In this work, investigation results for mixtures of polyamide 6 with polypropylene have been presented. Mixtures with content of 30, 50 and 70% of polyamide in relation to the polypropylene with compatibilization agent (Polibond 3150) in quantity of 2% have been produced. Ingredients of the mixtures are thermoplastic materials, which belong to the group of constructional materials, but with different properties. Polyamide 6 is characterised by quite good mechanical properties. On the other hand, polypropylene is characterised by poorer mechanical properties as compared with polyamide. Combination of favourable properties of both plastics leads to manufacturing of new plastic mixture nature but with favourable mechanical and application properties. The results of the investigation on PA/PP mixture properties by means of DMTA method shown that increase in PA concentration in mixture has not caused any crucial changes in pattern of dependencies of mechanical loss angle tangent complex modulus E *. Along with the increase in PA amount in PA/PP concentration, conservative modulus value (responsible for gathering and transmitting energy during consecutive deformation cycles) increases, while modulus connected with energy dissipation (in the form of heat) value drops. Having reduced curves for Young's and Kirchoff's modulus ( E′, E′′, G′, G) on the basis of DMTA analysis a course of Young's and Kirchoff's modulus changes with time calculation in this work have been suggested.

A New Approach to Estimating the Parameters of Piezoelectric Vibrator through Open-Circuit Transient Response

This study investigates the open-circuit transient response of a piezoelectric vibrator in order to determine the mechanical and dielectric resistances from the AC and DC response times of the transient response determined immediately after the electrical source of the vibrator is switched off. The vibrator is placed on a sponge in air. The piezoelectric resistance is then determined from the factor that relates the terminal voltage to the current at resonance. Experimental results indicate that as the terminal voltage rises, the AC response time decreases, the DC response time increases, the mechanical and piezoelectric losses and their resistances increase, the resonant frequency falls and the motional current increases. Additionally, the terminal current equals the motional current at resonance. Therefore, the resonant frequency shift is mainly caused by the Young's modulus change. The parameters of resistance are sensitive to the vibration velocity, but those of inductance and capacitance are not.

218 ポリカーボネイト樹脂を用いた常温ひずみ凍結(OS6-4 光弾性法I)(OS6 実験力学の新展開)

The frozen strain method has been carried out by long time load under the low temperature or load in the short time over glass transition temperature. The former needs the long time course, the latter causes large deformation by the load, since the Young's modulus changes small and Poisson ratio increases. For the purpose of this experimental study, using the polycarbonate, trying to reduce the days spent for the experiment and to froze the strain under the room temperature. In the industrial product, the polycarbonate used in this study is made by the extruding. Therefore, there is the residual stress. Annealing is effective measures in order to reduce the residual stress. By comparing the polycarbonate with annealing to the polycarbonate without that, the effect of annealing is confirmed.

Internal friction and the Young's modulus change associated with amorphous to nanocrystalline phase transition in Mg-Ni-Y alloy

The internal friction and Young's modulus of amorphous Mg 84Ni 12.5Y 3.5 alloy obtained by the melt spinning technique have been measured by a vibrating reed method at heating and cooling runs from 300K to 625K. The crystallization kinetics of the alloy was studied by the calorimetric methods. The structure of the samples was determined by the X-ray diffraction technique. The Young 's modulus measurements have revealed its significant (up to 50%) irreversible multi-step changes accompanied by the irreversible internal friction peaks. These changes were observed in the same temperature intervals where the anomalies of thermal properties were found out. The results obtained are explained by the structural rearrangement (mainly, a topological ordering and crystallization processes) from amorphous to nanocrystalline state.

Phase imaging and stiffness in tapping-mode atomic force microscopy

The dependence of phase angles in tapping-mode atomic force microscopy on the magnitude of tip-sample repulsive interactions was investigated, and phase images of several hard and soft samples were recorded as a function of the free amplitude A 0 and the set-point tapping amplitude A sp. The phase angle of probe oscillation increases with decreasing the set-point amplitude ratio A sp A 0 . Phase imaging at moderate tapping ( A sp A 0 = ∼ 0.5 ) allows one to distinguish different surface features of both multicomponent materials and one-component systems with different density distributions. Phase images recorded at moderate tapping are related to surface stiffness variations associated with Young's modulus change.

Radiation damage of graphite and carbon-graphite materials

The results of the study of graphite and carbon-graphite materials obtained in the Russian Research Center “Kurchatov Institute” during a period of fifteen years are presented. The main structural effects and changes in pyrographites, nuclear (polycrystalline) graphites and carbon-graphite materials under irradiation are investigated. Irradiation temperatures and neutron fluences have been taken from wide ranges: ≈ 500–1200°C, and ≈ (0.01–2) × 10 26 n/m 2 respectively, ( E > 0.18 MeV). The following characteristics of materials are discussed: linear and volume changes in size, lattice parameters, radiation defect parameters, pore structure evolution, Young's modulus change, etc. Particular attention is given to mechanisms, governing material radiation stability as a function of processing and irradiation conditions. The widely known effect of radiation dimensional change in irradiated graphite has been observed in the experiment. It has been demonstrated that the radiation defect parameters and magnitudes of radiation dimensional change are defined by initial sizes of graphite crystallites (for irradiation temperatures ≥ 500°C). It has been shown also that this effect determines the radiation stability in polycrystalline nuclear graphites. Distinctions in behavior of carbon-graphite materials under irradiation are shown.

金属板材の知能化Ｖ曲げ加工の高精度化に関する研究 塑性変形による弾性係数の変化とスプリングバックへの影響

An intelligent V-bending process developed by the authors is briefly described and the importance of change in Young's modulus due to plastic deformation, which influences the amount of springback and therefore the accuracy, is emphasized. The change in Young's modulus in simple tension of a cold rolled steel sheet is experimentally investigated by affixing strain gauges on the specimen. It is shown that the Young's modulus changes drastically with plastic deformation and that this is much larger than that estimated from the change in apparent density. A model that explains this phenomenon is presented. By using the experimentally derived Young's modulus, V-bending process of the same metal is simulated by the finite element method in plane strain; the amount of springback is calculated and compared with the experimental results. It is shown that the springback calculated with the commonly used value of Young's modulus is far less than the experimentally derived one and that the calculation with varying modulus provides the better results. It is thus concluded that, for a better accuracy in sheet bending, the change in Young's modulus due to plastic deformation should be taken into consideration.

Young's modulus dependence on magnetic bias field in Fe/sub 73.5/Si/sub 16.5/B/sub 6/C/sub 1/Nb/sub 3/ alloy after successive annealings

Both as-quenched and annealed (in transverse magnetic field for 1 and 2 h in temperature range from 300 up to 500/spl deg/C) samples of the amorphous alloy of composition F/sub 73.5/Si/sub 16.5/B/sub 6/C/sub 1/Nb/sub 3/ were investigated. The aim of this work was to study the influence of the annealing time and temperature on Young's modulus changes (/spl Delta/E effect) versus magnetic bias field after successive heat treatment up to neighborhood of the nanocrystallization temperature. Elasticity moduli were measured using resonant-antiresonant method. A considerable improvement of the piezomagnetic properties was observed by increasing the annealing temperature up to 480/spl deg/C. Maximum /spl Delta/E effect reached 0.57 after one hour annealing. Annealing at 500/spl deg/C caused sudden drop of the piezomagnetic properties, which can be explained by the decrease of the magnetostriction accompanying the appearance of the nanocrystalline phase.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The glass transition in basalt

The glass transition has been experimentally detected in basalt as (1) an increase in the aggregate linear thermal expansion coefficient αL, (2) an abrupt change in the temperature dependence of Young's modulus dE/dT, and (3) a change in stress relaxation behavior that effectively separates the T&gt; TG and T &lt; TG creep regimes. Transition temperatures determined by the respective experimental methods are (1) 730° ± 15°C, by expansion dilatometry, (2) 725° ± 10°C, by acoustic spectroscopy, and (3) 725° ± 25°C, by stress relaxation. For olivine tholeiite from Kilauea Iki lava lake, Hawaii, thermal expansivity rises through the glass transition interval, attaining αυ = 39.0 × 10−6 °C−1 at 850°C. For olivine tholeiites with moderate glass contents, the temperature dependence of the Young's modulus changes on either side of the inferred TG of 725°C, and dE/dT= −0.071 kbar °C−1 for T&lt; TG, while dE/dT = − 0.21 kbar °C−1 for T &gt; TG. Collectively, the mechanical results suggest that for Hawaiian olivine tholeiite at 1‐atm pressure, the principal material responses are (1) elastic (T ≤ 600°C), (2) reduced creep (600 &lt; T &lt; 725°C), (3) glass transition (T ≃ 725°C), (4) enhanced creep (725 &lt; T&lt; 980°C), and (5) partial melt (T &gt; 980°C). Fracture surface morphologies developed during solidification suggest that the presence of the supercooled melt grain boundary phase may participate in the regulation of the thermal cracking process. Well‐preserved fracture surfaces formed by incremental crack growth are found to be covered with striations that correspond to the inferred sequential stopping positions of the advancing fracture front. These striae may be rationalized in terms of experimental analogues that have been produced in viscoelastic polymers by cyclic tension‐tension loading. The fracture surface morphology, mechanical data, and the controlled crack growth analogues suggest that thermal fracture in solidifying basalt is an incremental and cyclic process, involving three steps: (1) the accumulation of elastic strain energy in cooling rock at temperatures below that required for stress relaxation due to viscous flow in the intercrystalline liquid phase, (2) fracture at a ΔT determined primarily by the aggregate thermal expansion coefficient αυ and Young's modulus E, (3) the penetration by the advancing crack tip, of the thermal horizon capable of relaxing stress due to the creep of intercrystalline supercooled melt, producing the rough surface texture associated with the termination of a striation. Further crack growth must now await the migration of the solidus. The cycle then repeats. Striations measured in deep Hawaiian lava lakes have been compared with the crack advance increments expected in the vicinity of the glass transition, based on two tests: (1) thermal gradients measured in Kilauea Iki, combined with the mechanical properties of olivine tholeiite evaluated near TG, and (2) the crack advance required to match the recorded seismic stopping phases for prexisting cracks of the dimensions expected for Kilauea Iki. The observed versus predicted comparisons are (1) 31 versus 36 cm; and (2) 31 versus 30 cm. We envision this incremental crack growth process as contributing to the control on the downward movement of the thermal cracking front—and its associated hydrothermal circulation zone—in the upper portions of solidifying subaerial and submarine ponded basalt.

Biologic effects of materials derived from Staphylococcus: Further studies

FGMs are regarded as one of the most promising candidates for future advanced composites in many engineering sectors, but they may suffer the problem of delamination. Delaminations in structures may significantly reduce the stiffness and strength of the structure and may affect their vibration characteristics. In the present study, an analytical solution is developed to study the free vibration of exponential functionally graded beams with a single delamination. Kirchhoff-Love hypothesis, the ‘free mode’ and ‘constrained mode’ assumption in delamination vibration are adopted. The shifting of neutral axis due to asymmetrical distribution of material property (in thickness direction) is also taken into consideration. This is the first study on the influences of delamination (its length and location) on the vibration of exponential functionally graded beams. Results show that the natural frequency increases as the Young's modulus ratio increases, but such increase is smaller when the beam suffers a longer delamination. Furthermore, the effect of delamination length and longitudinal location on reducing natural frequency is aggravated when the material property (Young's modulus and density) changes less dramatically from the bottom to the top. The difference of natural frequency between ‘free mode’ and ‘constrained mode’ becomes smaller with a decreasing Young's modulus ratio. The analytical results of this study can serve as the benchmark for FEM and other numerical solutions.