Internal friction and Mössbauer study of C–Cr associates in MANET steel

1997 ◽  
Vol 12 (2) ◽  
pp. 296-299 ◽  
Author(s):  
P. Gondi ◽  
R. Gupta ◽  
R. Montanari ◽  
G. Principi ◽  
M. E. Tata
Keyword(s):  
Internal Friction ◽  
Slow Rate ◽  
Structural Model ◽  
Martensitic Steel ◽  
Experimental Results ◽  
Thermal Treatments ◽  
Mössbauer Study ◽  
Low Intensity ◽  
Magnetic Pattern ◽  
Bcc Phase

Internal friction and Mössbauer techniques have been used to investigate the structure of C–Cr associates and the arrangement of Fe atoms near them in the Cr martensitic steel MANET subjected to different thermal treatments. After slow rate cooling from the austenitic field, the Mössbauer spectra exhibit, besides the complex magnetic pattern of martensite, a low intensity singlet attributed to the presence of a Cr-rich bcc phase. In correspondence, the internal friction curves, show, among others, a Snoek-type peak due to anelastic processes involving C–Cr associates with 6 Cr atoms. To explain the experimental results, a simple structural model is suggested.

scholarly journals Hot Deformation Behavior and Dynamic Recrystallization of Ultra High Strength Steel

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1239
Author(s):  
Liping Zhong ◽  
Bo Wang ◽  
Chundong Hu ◽  
Jieyu Zhang ◽  
Yu Yao
Keyword(s):  
Martensitic Steel ◽  
High Strength ◽  
Experimental Results ◽  
Hot Deformation Behavior ◽  
Thermal Compression ◽  
Forging Process ◽  
Finite Element Software ◽  
Ultra High Strength Steel ◽  
Recrystallized Grain Size ◽  
Deform 3D

In this paper, in order to improve the microstructure uniformity of an ultra-high strength martensitic steel with a strength greater than 2500 MPa developed by multi-directional forging in the laboratory, a single-pass hot compression experiment with the strain rate of 0.01 to 1 s−1 and a temperature of 800 to 1150 °C was conducted. Based on the experimental data, the material parameters were determined, the constitutive model considering the influence of work hardening, the recrystallization softening on the dislocation density, and the recrystallized grain size model were established. After introducing the model into the finite element software DEFORM-3D, the thermal compression experiment was simulated, and the results were consistent with the experimental results. The rule for obtaining forging stock with a uniform and refinement microstructure was acquired by comparing the simulation and the experimental results, which are helpful to formulate an appropriate forging process.

Experiment on the Attenuation Characteristics of Shock Wave Interacting with Open and Closed Foam

2014 ◽  
Vol 1035 ◽  
pp. 445-452
Author(s):  
Jian Wang ◽  
Bao Gui Wang ◽  
Gang Tao
Keyword(s):  
Shock Wave ◽  
Internal Friction ◽  
Dynamic Behavior ◽  
Solid Phase ◽  
Experimental Results ◽  
Reflection And Transmission ◽  
Attenuation Characteristics

For understanding the dynamic behavior of open and closed foam subject to a shock wave, this paper through experiments, to gain a deeper understanding of the incidence, reflection and transmission of a shock wave when it interacted with cellular foam. Moreover, by analyzing the loss of the peak overpressure and positive impulse, we were able to respectively know the positive impulse of the incidence, reflection and transmission shock wave. The experimental results indicated that the attenuation capability for foam to the shock wave was caused by the internal friction and deformation of solid phase, which would absorb the energy of the shock wave. From the results we gain an understanding that the mechanical phenomenon of open foam to shock wave are not fully consistent with those of closed foam , while the attenuation of open foam to shock wave is more effective than that of closed foam.

scholarly journals An efficient three-dimensional foil structure model for bump-type gas foil bearings considering friction

Friction ◽  
2020 ◽  
Author(s):  
Yongpeng Gu ◽  
Xudong Lan ◽  
Gexue Ren ◽  
Ming Zhou
Keyword(s):  
Structural Model ◽  
Three Dimensional ◽  
Element Model ◽  
Experimental Results ◽  
Synthesis Methods ◽  
Structure Model ◽  
Foil Bearings ◽  
Static Responses ◽  
Bearing Sleeve ◽  
Shell Finite Element

Abstract This paper presents an efficient three-dimensional (3D) structural model for bump-type gas foil bearings (GFBs) developed by considering friction. The foil structures are modeled with a 3D shell finite element model. Using the bump foil mechanical characteristics, the Guyan reduction and component mode synthesis methods are adopted to improve computational efficiency while guaranteeing accurate static responses. A contact model that includes friction and separation behaviors is presented to model the interactions of the bump foil with the top foil and bearing sleeve. The proposed structural model was validated with published analytical and experimental results. The coupled elastohydrodynamics model of GFBs was established by integration of the proposed structural model with data on hydrodynamic films, and it was validated by comparisons with existing experimental results. The performance of a bearing with an angular misalignment was studied numerically, revealing that the reaction torques of the misaligned bearing predicted by GFB models with 2D and 3D foil structure models are quite different. The 3D foil structure model should be used to study GFB misalignment.

Implementation of the Wideband Autoparametric Vibration Absorber on a Flexible Structure

2003 ◽  
Author(s):  
Ashwin Vyas ◽  
Anil K. Bajaj ◽  
Arvind Raman
Keyword(s):  
Slow Rate ◽  
Excitation Frequency ◽  
Response Amplitude ◽  
Control Signal ◽  
Experimental Results ◽  
The Other ◽  
Flexible Structure ◽  
Vibration Absorber ◽  
Governing Equations ◽  
Near Resonance

The dynamics of a resonantly excited thin cantilever with an active controller are investigated experimentally. The controller mimics a passive wideband absorber discussed in [1]. PZT patches are bonded to both sides of the beam to actuate it, while an electromagnetic shaker drives the beam near resonance. An active controller consisting of an array of uncoupled controllers is developed, such that the governing equations for the controller are quadratically coupled to the resonating system. The control signal, in terms of the motion of the controllers, is quadratically nonlinear. The controller is implemented using a modelling software and a controller hardware board. Two sets of experiments are performed: one with a constant excitation frequency and the other with a linearly varying excitation frequency at a slow rate (non-stationary excitation). The experimental results verify the analysis presented for the passive wideband autoparametric vibration absorber. They also demonstrate the effectiveness of the absorber in reducing the response amplitude of structures, and its robustness to frequency mistuning.

A Cluster Modelling Study of Conductivity of Yttria-Stabilized Zirconia

1992 ◽  
Vol 293 ◽  
Author(s):  
Laura E. Depero ◽  
Marcello Zocchi ◽  
Fulvio Parmigiani
Keyword(s):  
Structural Model ◽  
Fixed Number ◽  
Yttria Stabilized Zirconia ◽  
Experimental Results ◽  
Stabilized Zirconia ◽  
Number Of Clusters ◽  
Cluster Modelling ◽  
Modelling Study

AbstractOn the basis of a previously described structural model for the Yttria-Stabilized Zirconia, the conductivity for this material can be calculated. A fixed number of clusters is generated in a structure of 70×28 polyhedra to simulate different Y contents in the structure. The results are compared with the experimental results obtained by others and discussed.

scholarly journals Influence of light intensity on the lifetime of carriers in silicon investigated by a photoacoustic method

2016 ◽  
Vol 24 (2) ◽  
Author(s):  
L. Bychto ◽  
M. Maliński
Keyword(s):  
Light Intensity ◽  
Measurement Method ◽  
Experimental Results ◽  
Low Intensity ◽  
Photoacoustic Method ◽  
Type Silicon ◽  
Silicon Crystals

AbstractThe paper presents experimental results of the lifetime of light induced excess carriers in the n−type silicon. The lifetimes of carriers of silicon crystals were analysed as a function of the intensity of light illuminating the sample. As a measurement method of the lifetime of carriers, the photoacoustic method in a transmission configuration with different surfaces was used. The dependence character was next analysed in the frame of the Shockley Reed Hall statistics in approximation of the light low intensity.

scholarly journals Generating Robust Audio Adversarial Examples with Temporal Dependency

2020 ◽  
Author(s):  
Hongting Zhang ◽  
Pan Zhou ◽  
Qiben Yan ◽  
Xiao-Yang Liu
Keyword(s):  
Speech Recognition ◽  
Automatic Speech Recognition ◽  
Defense Mechanisms ◽  
User Study ◽  
State Of The Art ◽  
Temporal Structure ◽  
Human Perception ◽  
Experimental Results ◽  
Low Intensity ◽  
Adversarial Examples

Audio adversarial examples, imperceptible to humans, have been constructed to attack automatic speech recognition (ASR) systems. However, the adversarial examples generated by existing approaches usually incorporate noticeable noises, especially during the periods of silences and pauses. Moreover, the added noises often break temporal dependency property of the original audio, which can be easily detected by state-of-the-art defense mechanisms. In this paper, we propose a new Iterative Proportional Clipping (IPC) algorithm that preserves temporal dependency in audios for generating more robust adversarial examples. We are motivated by an observation that the temporal dependency in audios imposes a significant effect on human perception. Following our observation, we leverage a proportional clipping strategy to reduce noise during the low-intensity periods. Experimental results and user study both suggest that the generated adversarial examples can significantly reduce human-perceptible noises and resist the defenses based on the temporal structure.

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