Effect Of Stored Energy Research Articles

Effect of stored energy on corrosion fatigue properties of ultrafine grained Fe-20%Cr steel by equal channel angular pressing

Corrosion fatigue properties of ultrafine grained (UFG) Fe-20%Cr steel by equal channel angular pressing was investigated in term of grain refinement and stored energy. The corrosion fatigue life of the ECAP processed and the post-ECAP annealed sample was analysed. Under annealing temperature of 773 K, due to the recrystallization stage, there was a little difference in microstructure from the four passes ECAP. After the annealing process, the strength of the samples pressed four passes decreases, while the elongation showed more ductile. Two mechanisms for crack propagation have been well recognized for stainless steel. One is slipping step dissolution mode. In this model, the slip step formed by active dislocation at a crack tip is anodic dissolution reaction, so that crack tip advance to further distance. The other is stress adsorption mechanism. The corrosion fatigue cracks initiation and cracks propagation process of iron-chromium alloy can be characterized by corrosion pits and intergranular fracture, respectively. The corrosion fatigue behaviour of non-equilibrium and equilibrium grain boundary of iron-chromium alloy was occupied by crack initiation.

Effect of microalloying elements on the Cube texture formation of Fe48%Ni alloy tapes

The effect of microalloying elements sulfur and niobium was studied in Fe48%Ni sheets on the first stages of nucleation and on recrystallization. It was shown that the addition of sulfur promotes the formation of Cube grains while the addition of niobium prevents the Cube grains formation. Regarding sulfur, it combines with manganese which is an inhibitor of recrystallization to form the MnS precipitates. The stored energy difference between Cube component and others components AEoube/other increases when sulfur is added. This stored energy difference which is the main driving energy for Cube grains formation during recrystallization explains the sharpness of the Cube texture when sulfur is added. On the contrary the niobium microalloying element addition prevents the formation of Cube grains. This could be explained by the fact that stored energy of cold-rolled components decreases with the addition of niobium and thus decreases Cube grains fraction when niobium is added. In order to explain these results, the development of Cube texture during recrystallization has been investigated in detail by EBSD, furthermore, the effect of stored energy has been studied by carrying out neutron diffraction measurements on the deformed states.

The buoyancy method—a potential new primary ultrasound power standard

The acoustic output power produced by medical ultrasound equipment is a key quantity representing the safety of exposure to ultrasound during diagnostic or therapeutic applications. At present the widely used method for estimating the total output power from ultrasound sources is by measuring the radiation force using a gravimetric balance. The method described here is a non-radiation force method using a form of calorimetry where the average temperature change in a target filled with castor oil is inferred from its volume change. This method has been previously validated using a radiation force method at frequencies of 1 MHz and 3 MHz for acoustic powers in the range 1 W to 350 W. Estimated systematic uncertainty at the 95% confidence interval was 3.4% for a frequency of 1 MHz at 50 W measured power and typical overall uncertainties were of the order of 4%. The same method is extended and validated in the frequency range 3.151 MHz to 9.541 MHz using an improved target and applied powers in the range 100 mW to 1 W. The investigation of higher frequencies and modified data analysis has improved understanding of two important systematic effects. Firstly, heat loss from the front surface of the castor oil target: this was found to be a function of insonation time and increasingly significant at higher frequencies. Secondly, the effect of stored energy in a heating element inside the target which is used to calibrate the system by electrical heating: this could be significant for heating times less than 20 s. At a 95% confidence level, the estimated systematic uncertainty in the measured power with the improved target is 2.6% for 50 W acoustic power at a frequency of 3 MHz.

Effect of stored energy and recovery on the overall recrystallization kinetics of a cold rolled low carbon steel

The evolution of recrystallization kinetics of a cold rolled low carbon steel with an initial coarse grain size and heterogeneous microstructure is studied by means of nucleation and interface-averaged grain boundary migration rate. Recrystallization is governed by two annealing time ranges, characterized by two Avrami exponents. Range 1 is associated to the recrystallization of high stored energy regions mostly belonging to the γ-fiber and Range 2 to the progression of recrystallization mainly through low stored energy α-fiber grains. The transition from Range 1 to Range 2 is consistent with the decrease of high stored energy regions. Afterwards, recrystallization is very sluggish due to the low stored energy regions remaining in the material and leads to incomplete recrystallization for annealing times of practical significance. Additionally, coercive field measurements are used to infer the evolution of concurrent recovery with recrystallization. Recovery only accounts for a small part of the decrease of the total stored energy, the rest being due to the heterogeneous distribution of the stored energy.

Studies on waveguide-fed slot antenna

The paper presents investigations of the effect of stored energy inside a waveguide, near a displaced narrow longitudinal slot, on the immittance properties of the radiating slot. It is shown that internal stored energy accounts for the discrepancy between the theoretical and experimental results of the immittance characteristics observed in earlier studies. The effect of stored energy is to contribute an additional reactive term in the expression for the immittance of the slot. By the addition of this extra reactive term to the theoretical expression for the immittance, it has been possible to predict the point of resonance with better accuracy. Further, an expression is derived for the immittance presented by a slot to the transmission-line representation of the waveguide, as a function of slot length, displacement etc. by the application of the principle of duality to the dipole antenna.