Strain Energy Cumulation at Increased Temperatures

This paper presents results of strain energy ΔWpl cumulation tests on cast steel specimens under constant-amplitude isothermal stress conditions and programed block stress conditions at three different temperatures (20, 400, 600°C). Programed loads (blocks) were composed of five stages of different sequences which included the same strain as during the constant-amplitude isothermal tests. Through the constant-amplitude tests the author demonstrated effect of temperature and the strain level on the fatigue life, strain energy value ΔWpl and accumulated energy ΣΔWpl. While no influence of the load program form on the value of the energy accumulated in the specimen was found.

Cumulation of a spherically converging shock wave in metals and its dependence on elastic-plastic properties, phase transitions, spall and shear fractures

Consideration is given to results of experimental and theoretical investigations how alpha-epsilon phase transition in the unalloyed iron and the 30 KhGSA steel and its absence in the austenitic 12Kh18N10T stainless steel influence processes under explosive deformation of spheres made of these materials. Polymorphous transition is shown to significantly effect on: amount of explosion-products energy transferred to a sphere, evolution of the converging-wave structure and its parameters, profiles of stress wave and temperature T(R, t) for some Lagrangian particles along the sphere radius, character of energy cumulation under spherical convergence of waves.

Joint Estimation of Doppler and Time Delay of Wideband Echoes for LFM Pulse Radar Based on Fractional Correlation in Impulse Noise Environment

A new method to estimate the Doppler and multipath time delay is presented in impulse noise environment. First, the Doppler is estimated by energy cumulation of multipath component based on fractional lower-order-frational correlation transform. Then, an order-reduced signal is reconstructed combining the Doppler with the prior knowledge of the transmitted signal, and the echoes signal is converted to many single-frequency signals. Finally, the multipath time delay is obtained by the fractional lower-order power spectrum method. The method is adapted for low SNR noise, can restrain the affection of the cross-items, and has a high time-delay estimation resolution. Some computer simulations are given in this paper and the results show that the new method is valid.

Joint Estimation of Doppler and Multipath Time Delay of Wideband Echoes for LFM Pulse Radar Based on Fractional Correlation

A new method based on fractional correlation theory for estimating the Doppler and multipath time delay of the wideband echoes for LFM pulse radar by only one pulse signal is presented. First, the Doppler is estimated by energy cumulation of multipath component based on fractional correlation transform. Then, an order-reduced signal is reconstructed combining the Doppler with the prior knowledge of the transmitted signal, and the echoes signal is converted to many single-frequency signals. Finally, the multipath time delay is obtained by the dechirping method. The method is adapted for low SNR noise, can restrain the affection of the cross-items, and has a high time-delay estimation resolution. Some computer simulations are given in this paper and the results show that the new method is valid.