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ntAb and γ(t) = |
Ab,t(t)/As(t).Finally, the welded area and fractured area during mechanical alloying was expressed as k and can be solved by combining Eqs. k=γ/τ(α(t)/(dα(t)/dt))+1γ/τ(α(t)/(dα(t)/dt))−1/2The results of theoretical analysis are provided in this section. The surface CNT length, length distribution, surface area, nominal... |
; |
μ, σ2) is the fitted normal distribution with mean of μ and variance of σ2; G(0 ; |
μ, σ2) is the value of cumulative distribution function of normal distribution g(l |
; |
μ, σ2) at l |
= 0 The fitted surface CNT length distributions at different mechanical alloying times are shown in (b). As the average length of the CNT length decreased, the CNT length variance also decreased during mechanical alloying.The SEM images of the fabricated Al6061–CNT samples are shown in . The CNT agglomerations were sho... |
= |
Aa/Aa,0), the dispersion can be written as d |
= 1 − |
Aa/Aa,0, where Aa,0 is the CNT agglomeration area when no CNT is dispersed. The dispersion, d, can be fitted with the equation shown in The SEM images of the particles mechanically alloyed for 30 min are shown in . Due to the complexity of the particle shapes, three simplified geometries as shown in (b)–(d) were used t... |
= 50 mm, thickness, B |
= 12.5 mm and initial notch, a0 |
= 13.5 mm. The dimensions chosen are in accordance with ASTM test standard The tests were conducted in both electric-actuator and servo-hydraulic test machines. The C(T) specimens were pre-cracked to an initial crack length to width ratio, a/W, of about 0.4, under cyclic loading at room temperature. The specimens were ... |
= 90°, the value of β |
≈ 0.33 and Fcr (90°, 8.24) = 0.387 where A – pre-exponent in power law-creep and η1 for C(T) specimen is given by :The first term on the right hand side of Eq. represents the small scale creep contribution and second term represents the extensive creep contribution to the value of (Ct)avg. h1(a/W, |
n) for various a/W and n are available in Kumar et al. Combined creep and fatigue crack growth may take place at elevated temperatures. In most cases fatigue dominates at higher frequencies (f > |
1 Hz) and creep dominates at lower frequencies (f |
< 0.1 Hz) and hold times where (da/dN)time is related to (da/dt)avg by:The first term on the right hand side of Eq. accounts for cycle dependent crack growth rate and the second term represent the time-dependent part. In this approach, the cycle-dependent and the time-dependent crack growth rates during creep–fatigue ... |
⩾ 0.5 ΔV and the crack growth behavior may be characterized by the stress-intensity factor. On the other hand, if ΔVe |
⩽ 0.5 ΔV, creep-ductile conditions are said to prevail and the crack growth behavior should be characterized by (Ct)avg. The former condition is expected when there is large ȧ values and higher resistance to creep deformation, and the latter occurs with low ȧ values and higher creep deformation rates in the material.... |
= |
h |
+ |
k |
+ |
l, h02 |
= |
h2 |
+ |
k2 |
+ |
l2 (Miller indices h, k, l). Following this definition u is the number of broadened components and b the number of broadened ones.To account for the overall broadening, we define an effective size Deff, computed from the domain size D, the deformation and twin fault probabilities in the following way:Peak asymmetry is ... |
+ |
x2, where 2θ0 is the center of a fully symmetric profile, the peak asymmetry can be expressed as:The values of the compound fault probability parameters [1.5(α' |
+ |
α'' |
+ |
β)] and the values of dislocation densities ρ are also calculated to estimate the overall effect of faulting the procedure as adopted in the earlier reference SP intensity of 0.30 mmA is usually regarded as industrial processing reference datum. So intensity of 30 + 0.15 mmA was chosen as research object in present wor... |
= |
nb |
· |
mb/mp is used. For a certain specific degree of refinement, it is expected thatwhere tinit is the time when the reaction is initiated.This reasoning suggests that the milling time required to trigger initiation depends on the diameter of the milling balls exclusively via the charge ratio. A similar relation was suggest... |
= 10 rather than CR |
= 2.5 as the experimental results. For CR |
= 5 and 2 g milling sample for both systems, the trends are in good agreement with the DEM prediction. The validity of Eqs. is also well represented in the DEM results with a near constant milling dose for 4.76 mm balls among all charge ratios. This intersection point represents the most efficient milling condition fo... |
s−1.The impact toughness was measured using Charpy v-notch specimens that were prepared according to ASTM standard E23. These were machined from plates at inclinations of 0°, 45°, and 90° with respect to the rolling direction. The Charpy tests were performed at RT (20 °C), 0 °C, −20 °C, −40 °C, −55 °C, and −70 °C. For ... |
rad. The apparent yield stress was determined using a stepped flow approach to measure viscosity as a function of shear stress and shear rate. To calculate the apparent yield stress, the shear-thinning regime of the data was fitted to a Hershel–Bulkley model.An aerated chocolate milk shake, stabilised using hydrophobin... |
s−1), and high temperature (until 1400 K) as encountered during high-speed machining process.Linear friction models (such as Coulomb, Coulomb–Orowan, and Tresca) and non-linear relations A set of different friction testing stand can be used to identify the friction parameters at the tool–chip interface. Pin-on-disc sys... |
K w−1 |
m−2). Tool boundaries far away from the contact zone are retained at the initial temperature (Tinit). Other surfaces of the workpiece are dealt without any heat loss either by convection or by radiation.The test parameters namely the specimen temperature T and the contactor penetration p are obtained from the finite el... |
δ leading to accurate quantitative values for the Tg. By accurately determining the reduced Tg, the foaming temperature could be chosen to control the foam morphology. Foams were produced which ranged in density from 290 to 1100 kg/m3. The foams had cell nucleation densities between 109 and 1010 |
cells/cm3, two orders of magnitude higher than unreinforced PAES foam, suggesting that the CNFs acted as heterogeneous nucleating agents. The CNF–PAES foam exhibited improved compressive properties compared to unreinforced PAES foam produced from a similar method. Both the specific compressive modulus and strength incr... |
δ was determined as a function of temperature from 50 to 240 °C.The foam density was determined using the water displacement method. A foam specimen was weighed and submerged in water. The displaced water was measured to determine the volume of the foam. Because the foam has a thin skin layer on the surface and a predo... |
δ are shown in for CNF–PAES saturated with 7.6% CO2 and water and CNF–PAES which had not been saturated. The data from the storage modulus suggests that the bulk of the sample remained saturated with the blowing agents until the CNF–PAES was heated to the lowered Tg due to plasticization. If a considerable amount of b... |
δ. The storage modulus and tan |
δ exhibited only one transition in the CNF–PAES samples containing no blowing agents. This transition was observed at 227 °C, which was close to the Tg of the PAES. When the CNF–PAES sample was saturated with CO2 and water, three distinct transitions were observed as peaks in the tan |
δ. The first transition was observed at 160 °C, which is attributed to the plasticized Tg of the CNF–PAES due to the presence of both the CO2 and water. Once 160 °C was reached, the CO2 was able to rapidly diffuse out of the PAES matrix while a majority of the water remained in the polymer. The broadening of the decrea... |
cells/cm3. The cell nucleation density was two orders of magnitude higher than neat PAES foam produced with water and CO2 under the same saturation and foaming conditions . In the micrograph, it can be seen that a CNF protrudes from the initially nucleated cell. The presence of heterogeneous nucleation produces a large... |
δ provided more quantitative results than in the DSC. The loss of the blowing agents yielded a large endothermic peak did the DSC thermograms, which overlapped with the reduced Tg, and hindered quantitatively determining the Tg.The DMTA results were used to quantitatively determine the thermal transitions of the satura... |
MPa. From the results, it is observed that the joint strength of the bonded shrink fitted joint is greater than that of the shrink fitted joint. shows the comparisons of the joint strength of the bonded shrink fitted joint in which a ring is fitted at the middle of a shaft between the numerical and the experimental re... |
Tm; Tm is about 3100 K suggested by experiments As a typical ceramic oxide, UO2 is expected to experience cleavage fracture at low temperature, with the {1 1 1} plane being one of the natural cleavage plane To represent the load–displacement curves, the responses of nominal stress σzz and system volume V with respect t... |
− |
PbO2) phase. As shown in c, the crack extension takes place along the interface between the Fluorite and the newly formed Scrutinyite regions (c) at 6.2% strain. As the crack extends, the Scrutinyite region in c transforms back to the Fluorite phase, and new lattice structures develops around the crack tips (d) at 7.0%... |
MPam0.5, close to the experimental value of 0.2–0.45 |
MPam0.5 in sintered UO2 where intragranular fracture is dominant a), since the new structure forms primarily along the (1 0 0)F planes, 54° from the X((2¯11)F) direction. However, the shape of the stress field changes as a result of the phase transformation (a–c). High tensile stress develops along the non-coherent (0 ... |
J/cm2) when cementite growth is driven by bulk and grain boundary diffusion, respectively. These values match the measured activation energy for Stage II softening of 35±4 kJ/mol determined in the present study. When it is considered that the dominant diffusion mode was grain boundary diffusion, the low activation ener... |
K−1local pressure on the surface of cylinder, PaRayleigh number ≡ρc2cpgβΔTd3μBk, dimensionlessvelocity component in x-direction, dimensionlessvelocity component in y-direction, dimensionlessvelocity component in z-direction, dimensionlessWithin the framework of time-independent fluid behavior, yield-stress fluids displ... |
= 0) and/or free convection without the heated circular cylinder placed at the axis of the enclosure filled with a Bingham fluid.Consider a horizontal circular cylinder of diameter d (infinitely long in z-direction) whose surface is maintained at a constant temperature, Th, and it is positioned collinearly in a square ... |
= (d/L) was varied in the range 0.125⩽B⩽0.5. Due to the existing temperature difference between the wall and the cylinder, the density of the fluid will be minimum near the cylinder and it will increase gradually away from the cylinder ultimately reaching the value ρc corresponding to the wall temperature Tc. This, in ... |
= |
Th |
− |
Tc) imposed here never exceeded 5 K, it is thus justified to use the physical properties of the fluid at the mean film temperature of (Th |
+ |
Tc)/2. The variation of the fluid density with temperature is treated by the well known Boussinesq approximation as:where ρc is the fluid density at the reference temperature Tc and β is the coefficient of thermal expansion at a constant temperature defined as:Under these assumptions, the coupled governing equations fo... |
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