Dynamic Young Modulus Research Articles

Collective motion of many atoms in amorphous alloys induced under passing electric current

The effects of passing a direct electric current (PEC) on the dynamic Young's modulus E of a-Cu 50Zr 50, Cu 50Ti 50 and Pd 50Si 50 were investigated for the current density i d below 4 × 10 3 A/cm 2 using a vibrating reed technique. We observed the increases in E due to PEC, and further found that the effects of PEC on E are identical to those of applied stress on E after the scaling between i d and stress. The scaling gives the effective charge number Z* which measures the electromigration force under PEC as being around the order of 10 5 for all the a-alloys, suggesting that the collective motion of many atoms is induced under PEC. From the changes in Z* and in the specific volume due to annealing, we evaluated the number of atoms associated with the collective motion as being several hundred.

Porosity expansion of tablets as a result of bonding and deformation of particulate solids

This paper describes the tabletting process of y-sorbitol on the basis of the stress-deformation curve. This curve distinguishes between small, elastic deformation and large, viscous deformation. Small deformations can be quantified by the dynamic Young's modulus. The results demonstrated an effect of both rate of strain and initial particle size on the Young's modulus. The yield strength of compacts is a quantification of large deformations. There appeared to be an effect of strain rate on yield strength, but no clear relation between initial particle size and yield strength. The study relates elastic deformation with storage of elastic energy. The amount of stored energy was found to increase with compaction speed, and is postulated to be the driving force for changes of tablet porosities after compression. The attraction between particles causes resistance against porosity expansion, and is defined as expansion capacity. The expansion capacity showed no relation to compaction speed. It is therefore concluded that the effect of compaction speed on tablet properties is purely an effect of the amount of stored energy. The reciprocal value of expansion capacity demonstrated a direct relation with the constant that fits the relation between tablet strength and porosity. The expansion capacity is hence a quantification of bonding.

Elastic behaviour and structural evolution of nanocrystalline Fe 73.5Cu 1Nb 3Si 13.5B 9 produced by thermal ageing or joule-heating

Internal friction and dynamic Young's modulus versus temperature were measured in Fe 73.5Cu 1Nb 3Si 13.5B 9 melt-spun ribbons as-prepared or after being submitted to Joule-heating treatments or to furnace annealing during isothermal modulus measurements. In Joule-heated samples the resistance was measured continuously during the heating treatments. Changes in the resistivity reflecting changes in the microstructure were correlated with room-temperature measurements of the magnetic permeability and the ΔE effect. The experimental results are discussed with specific reference to the microstructural evolution of the annealed ribbons from the initial amorphous phase to the nanocrystalline phase. A strong enhancement of the ΔE effect was found in Joule-heated ribbons just before the nanocrystalline phase formed.

Ultrasonic velocity in epoxy resin at temperatures down to 4.2 K

Results are presented from measurements of the velocity of longitudinal and shear elastic waves (f=5 MHz) in ED-20 epoxy resin, at temperatures from 4.2 to 293 K. These data were used to calculate the moduli of elasticity E′ and G′. Also, the moduli E′ (f=250 Hz) and G′ (f=2 Hz) of the ED-20 resin were measured directly. The calculated velocities of the low-frequency elastic waves ct=(E′/p)1/2 and ct=(G′/p)1/2 (where p is the density) were compared with the results from the ultrasonic measurements. The frequency dependence of elastic-wave velocity in the epoxy resin was evaluated. It was found that when the frequency was varied by four orders of magnitude, the dispersion of longitudinal-wave velocity was 18% at 4.2 K and 39% at 293 K. A quantitative criterion is proposed for estimation of the dispersion of sonic velocity from the results of measurements at any two frequencies. It was established that the sonic velocity at low temperatures varies linearly with the temperature, and in the case of longitudinal waves changes from cl-3360 m/sec at 4.2 K to 2820 m/sec at 293 K. The shear-wave velocity changes from ct=1630 m/sec at 5 K to 1340 m/sec at 293 K. The values of the dynamic Young's modulus E′ and shear modulus G′ at 4.2 K are 8.6 and 3.2 GPa, respectively. On a plot of c=f(T) for E′D-20, a transition is observed at 180 K, due to reorientational rotation of methyl groups. The activation energy of the relaxation process is 3.6 kcal/mole. Large values are obtained for the dispersion of the dynamic modulus E′:37.8% at 4.2 K and 93% at 293 K.

Effects of passing electric current on the elastic property of amorphous Cu50Zr50 and Cu50Ti50

For both amorphous Cu50Zr50 and Cu50Ti50, the dynamic Young's modulus M was found to increase under passing electric d.c.-current (PEC) with the current density id below 5 × 103 A/cm2, suggesting that PEC induces internal stress. The id dependence of M observed at low strain amplitude εt was found to be identical to the εt dependence of M without PEC after scaling between id and εt, giving Z* in the order of 105, where Z* is the apparent charge number measuring the electromigration force (EM-force) under PEC. We surmise that such a large Z* reflects the concentration of EM-force through the collective motion of many atoms, Z* = z*ξ, for ξ atoms with the charge number z* per atom. Application of this view to the observed effect of annealing on Z* gives ξ as several hundreds in the as-quenched state. Based on the present results, the effects of PEC on the structural relaxation and crystallization processes reported are also discussed.

Elastic modulus and vibration damping in Iron/Copper- and steel-based metal matrix composites

Measurements were made of the dynamic flexural modulus, dynamic Young's modulus, damping, strain amplitude, and the strain amplitude dependence of damping in iron/copper- and steel-based metal matrix composites. Comparisons were made concerning the steel matrix specimens before and after heat treatment. The flexural modulus tests were performed using the Grindosonic technique, while the Young's modulus, damping, strain amplitude, and the strain amplitude dependence of damping were determined using the piezoelectric ultrasonic composite oscillator technique (PUCOT). Metallographic studies utilizing chemical etching, optical and electron microscopy, and microhardness testing were performed to assess the distribution of the fibres in the composites. The variation of dynamic Young's modulus with respect to percentage copper in the composites followed the rule of mixtures.

Influence of microstructure on the physical properties of concrete prepared by substituting mineral powder for part of fine aggregate

The hydration reaction of cement, hardened structure and pore structure in concrete prepared by substituting a large quantity of mineral powder including fly ash, slag, limestone and silicious stone for part of fine aggregate in concrete have been studied and the relationships between the substitution of those mineral powders and the physical properties of concrete have been investigated. Increase in viscosity and decrease in fluidity of concrete by the substitution of the mineral powder for part of fine aggregate are mainly caused by the increase of fine particles non-existent in fine aggregate. Higher strength than that of concrete without substitution in the case with the same slump is brought by the densification of hardened concrete structure by filling effect of mineral powder itself and, in some cases, of CSH produced by pozzolanic reaction. The slight increase of creep of the concrete prepared by substituting fly ash for part of fine aggregate may be caused by offsetting the increase of the practical quantity of cement paste in concrete by the improvement of strength of the hardened concrete. The reduction of dynamic Young's modulus may be caused by the increase of practical quantity of cement paste with the dynamic Young's modulus almost half that of aggregate.

Damage Evoluation and Dynamic Mechanical Properties in a SiC Fibre Reinforced Ti Alloy Composite

Damage evolution in a SiC fibre reinforced Ti alloy composite (SCS-6/Ti-6Al-4V) has been assessed by modulus loss, change in internal friction (mechanical damping) and acoustic emission (AE). Damage was introduced into unidirectionally reinforced unnotched specimens by four point bending using constant cyclic amplitude loading. Dynamic Young's modulus and internal friction were measured by a flexural resonant method after a predetermined number of cycles, and AE signals were also monitored during the tests. Damage induced in the composites changed progressively primarily as a function of the applied maximum stress levels (σ max ). Fibre fracture dominated at σ max values greater than 0.5 σB (where σ B is the flexural strength of the composite). High amplitude AE signals associated with fibre fracture were observed, and internal friction measurements increased rapidly just before failure of the specimen. In contrast, matrix cracking dominated at σ max values lower than 0.35 σ B . As matrix cracks bridged by intact fibres) grow in these composites, internal friction measurements increase. Small amplitude AE signals were observed to be associated with matrix crack growth. Also, fibre fracture occurred in the bridged zone at σ max values between 0.35 and 0.5σ B . In all tests, the Young's modulus decreased by only 1% of its initial value until just before failure of the specimen. However, internal friction measurements increased rapidly prior to catastrophic failure of the specimen at all stress levels investigated in this study. This result shows that an increase in internal friction is related to damage accumulation in the composites, and suggests that measurement of changes in internal friction may be applicable to the assessment of damage in such composites.

建設材料 構造用レジンコンクリートの熱的特性と力学特性の温度依存性

Resin concrete (REC) is a concrete in which aggregates are bonded with synthetic resin instead of cement hydrates in ordinary cement concrete. For the structual use of the resin concrete, the thermal and temperature-dependent mechanical properties of RECs were experimentally examined. RECs with various resin contents were prepared by using two kinds of unsaturated polyester resins and two kinds of epoxy resins with different heat distortion temperatures (HDT) and glass transition temperatures (Tg), and tested for thermal properties such as specific heat, thermal conductivity and coefficient of thermal expansion, and temperature-dependent mechanical properties such as dynamic Young's modulus, logarithmic decrement, creep coefficient and compressive and flexural strengths.Thermal properties of RECs were very similar to those of ordinary cement concrete. Deformation and strength properties of RECs were temperature-dependent, and showed distinct inflection points in temperature in the respective properties where temperature-dependence became dominant. The inflection points were related to the HDT of the resins used rather than Tg, and were not affected by the resin content. The points can be defined as “heat distortion temperatures of RECs”. The maximum ambient temperature must be limited to these points or lower for the structural use of RECs. Consequently, the high HDT of the resins is preferable for structural RECs.

Investigation of dynamic Young's modulus for molybdenum disilicide-titanium trisilicide (MoSi2-Ti5Si3)

Molybdenum disilicide-titanium trisilicide (MoSi2-Ti5Si3) is a ceramic matrix composite (CMC) created for the purpose of improving the mechanical properties of molybdenum disilicide. Five alloys of this CMC were prepared by varying the ratio of volume per cent Ti5Si3 to volume per cent MoSi2. Evaluation of the specimens using the piezoelectric ultrasonic composite oscillator technique (PUCOT) determined the values of Young's modulus to range from 303 to 378 GPa at room temperature increasing with volume fraction of MoSi2. The values of Young's modulus for temperatures up to about 400 °C for each alloy decrease linearly with respect to increasing temperature. Damping within the specimens is independent of strain amplitude at room temperature, but shows some strain amplitude dependence at higher temperatures. The values of density for the alloys, determined using Archimedes' method, range from about 5200 to 5900 kg m−3, and compare favourably with the values determined by the rule of mixtures.

Description of the Nanocrystallization Process in Fe73.5Cu1Nb3Si13.5B9 Through the Study of the Anelastic and Magnetoelastic Behavior

A description of the nanocrystallization process of the amorphous Fe 73.5 Cu l Nb 3 S 13.5 B 9 alloy as deduced by a study of the anelastic and magnetoelastic behavior is reported. bE effect measurements were performed on the as-prepared alloy and on samples previously submitted to heating treatments in furnace at selected temperatures. The results were coupled to internal friction and dynamic Young's modulus vs. temperature measurements performed both in saturating magnetic field and in zero field. Different stages of the structural evolution towards the final crystalline state have been distinguished and their strict relationship with the observed changes in the magnetoelastic response has been pointed out. In particular a strong hE effect was observed in samples annealed at temperatures very close to the one at which the crystallization process starts.

Amplitude Dependence of Dynamic Young's Modulus of CuZnAl Alloys near Martensitic Transformation

The dynamic Young's modulus E of CuZnAl alloys displays non-linear behaviour in the vicinity of the martensitic transition as it decreases with increasing the amplitude of vibration.The difference AE between the Young's modulus measured at the lowest strain e0 and that at the current strain e shows a double peak in the transition region, both during heating and cooling.These peaks are believed to be associated with some lattice instabilities such as those leading from the austenitic β1 and β2 phases to the β’1 and β’2 martensites, respectively.The observed elastic non-linearity appears to be a bulk lattice effect.as it occurs even over temperature regions far above Ms’ where the system is a homogeneous single phase.

Measurement of elastic and anelastic properties of reaction-formed silicon carbide-based materials

The dynamic Young's modulus and the strain amplitude dependence of damping, at room temperature as well as at elevated temperatures, were determined for reaction-formed SiC (RFSC) ceramics, and the results are compared with those for other SiC materials. The method used was the piezoelectric ultrasonic composite oscillator technique (PUCOT). Five specimens were studied: NC 203 (a commercially produced SiC by Norton, Co.); RFSC No. 1 and RFSC No. 2 (each containing residual Si); RFSC No. 3 and RFSC No. 4 (both containing residual Si and MoSi2). Metallographie observations showed that the microstructure of the RFSC is essentially isotropic with a uniform distribution of phases. The “rule of mixtures” calculations cannot be used to predict accurately the elastic modulus of the RFSC, but they can be used to predict the density to within 5%. It was determined that for the RFSC, the dynamic Young's modulus decreases as temperature increases, in a manner similar to that for other SiC materials. It was also found that the damping of the RFSC is generally independent of strain amplitude and is weakly affected by temperature. The activation energy was determined for the change in damping with change in temperature of RFSC No. 2 and RFSC No. 3.

Variation of Electrical Resistance and the Elastic Modulus of Shape Memory Alloys under Different Loading and Temperature Conditions

Shape memory alloys (SMA) have recently been proposed and demonstrated for several active control applications. However, there is only limited experimental information available on the properties of the SMA. The present paper focuses on variations of the dynamical Young's modulus, the damping characteristics, and the electrical resistance as a function of the various parameters, such as temperature and applied stresses and strains. Tests were performed to measure the dynamic Young's modulus and damping characteristics of various Smas using the Dynamical Mechanical Analysis (DMA) method. The experimental results show that the curve of the dynamic Young's modulus exhibits a trough shape, while the damping curve has a maximum peak during the martensite = austenite transformation. The variation of the electrical resistance of the SMAS was also measured during the phase transformation under the action of an applied stress. The results show that the applied stress plays a significant role on the electrical resistance, which not only affects its value, but also changes the phase transformation sequence. Furthermore, the effect of the strain on the electrical resistance of the SMA at different phase states (martensite, austenite, and stress induced martensite transformation) was observed. In the initial stage of deformation,, the electrical resistivity decreases as the strain increases, and demonstrates a unique functional relationship.

A study of nanocrystalline iron and aluminium metals and Fe3Al intermetallic by mechanical alloying

Pure iron and aluminium powders and a mixture of composition Fe75Al25 were treated mechanically in a high-energy mill for up to 40 h. X-ray diffraction and analytical transmission electron microscopy were coupled to elastic energy dissipation and dynamic Young's modulus measurements to study the structural transformation of the specimens induced by the mechanical treatment. A quantitative comparison between the structural behaviour of the pure elements and of the mixture was carried out. The role of the parameters such as the composition, the grain size and the activation energy during the process was examined in relation to the competing mechanisms of plastic deformation and recovery.

Effects of ionizing radiation on the viscoelasticity of glassy polyethylene terephthalate films

Abstract The viscoelastic properties of Gamma-ray irradiated polyethylene terephthalate (PET) sheets, extruded in the glassy state, were measured by a method of forced resonance oscillations. Density variations due to γ-irradiation with different doses were found suitable to describe changes of the cross-linking rate. The dynamic Young's modulus of PET-films showed a decrease within the dose range 200-500 kGy which has anomalous behaviour related to the glass transition (alpha-relaxation) by γ-irradiation to a rubberlike state at a dose of 200 kGy. The low frequency velocity of sound showed no correlation with the density of irradiated PET-films.

Anelastic and magnetoelastic effects and microstructural evolution of the Fe73.5Cu1Nb3Si13.5B9 alloy

Abstract Internal friction, dynamic Young's modulus and δ E effect have been measured in Fe73.5Cu1Nb3Si13.5B9 ribbons obtained by melt spinning and subsequently submitted to furnace annealing or Joule heating. The measurements have provided informations on the different microstructural states and related magnetic behaviour.

Dependence of Vibrational Properties of Wood on Varnishing during Its Drying Process in Violin Manufacturing

The influence of varnishing for violins on the vibrational properties of wood strips was investigated during the drying process by vaporization of solvent. The changes of weight, specific dynamic Young's modulus (E/r), and loss factor (tan δ) by varnishing with natural varnish (shellac) and artificial ones (cellulose nitrate: CN) were measured and their subsequent changes were traced for 1 to 2 years. For both varnishes, though the remarkable weight decrease just after varnishing ceased after 3 to 5 months, a slight weight decrease continued even after then. The change of E/r became almost undetectable within several months, whereas the decrease of tan δ continued for a longer period. Acoustic converting efficiency (ACE) fell down drastically just after varnishing, but it recovered extending for 1 year. The recovery of ACE was more largely for shellac varnished specimen than the CN lacquered one. The frequency dependencies of E/r and tan δ changed by applying the CN lacquer, whereas those by shellac varnish did not change significantly. These results suggested the superiority of shellac varnish to CN lacquer

コンクリートの強度特性が破壊力学パラメータに及ぼす影響

Influence of microstructural changes in high strength concrete on toughening mechanism is studied. Load-displacement curves of notched beams of various types of concrete are analyzed by means of an inverse analysis technique to obtain the tension softening diagrams. Parameters of the bilinear tension softening diagram are discussed in relation to dynamic Young's modulus, compressive strength, tensile strength and porosity. A brittleness index was also proposed, which is defined as a function of fracture energy, tensile strength and Young's modulus. These results are useful to determine the tension softening diagram of concrete on the basis of general standard test results.

Dynamic Young's Modulus And Loss Factor Of Plastic Foams For Impact Sound Isolation

The frequency and amplitude dependences of the dynamic Young's modulus and loss factor of polystyrene (PS) and polyethylene (PE) foams usable for impact sound isolation in floating floors, measured at room temperature, in the frequency range of 100-3000 Hz, and in the range of strain amplitude of 10 -5-10 -2 respectively, are given in the paper. It is shown that the frame loss factor of the PS and PE foams is low (∼0·01 and ∼0·1, respectively), and that of the foam sheets including air is also low (∼0·1). The frame dynamic Young's modulus of both foams slightly increases with frequency. The dynamic behaviour of the foams is linear up to the strain amplitude of about 10 -3, above which the dynamic Young's modulus decreases, whereas the loss factor increases with increasing strain.