Modeling of a Simple Rotor With a Switching Crack and Its Experimental Verification

1992 ◽  
Vol 114 (2) ◽  
pp. 217-225 ◽  
Author(s):  
Chong-Won Lee ◽  
Jong-Seop Yun ◽  
Oh Sung Jun
Keyword(s):  
Numerical Simulations ◽  
Experimental Verification ◽  
Necessary Conditions ◽  
Crack Opening ◽  
Crack Identification ◽  
Crack Model ◽  
Identification Scheme

The switching crack model having two different stiffnesses, depending upon the crack status, is developed. The necessary conditions for the crack opening/closing states are then analytically derived from a simple rotor with a switching crack. The validity of the switching crack model and the crack opening/closing conditions is proved through numerical simulations and experiments, and a crack identification scheme based on the analysis is also proposed.

Crack Identification by Jointly Time-Frequency Analysis

2006 ◽  
Vol 324-325 ◽  
pp. 161-164
Author(s):  
Xin Feng ◽  
Jing Zhou
Keyword(s):  
Frequency Analysis ◽  
Crack Opening ◽  
Sampling Frequency ◽  
Dynamic Responses ◽  
Crack Identification ◽  
Crack Model ◽  
Breathing Crack ◽  
Time Frequency Analysis ◽  
Time Frequency ◽  
Novel Approach

A novel approach for crack identification based on jointly time-frequency analysis is presented in the paper. A bilinear stiffness model for the breathing crack was introduced to represent the nonlinear dynamics of a cracked beam. The nonlinearity of the dynamic responses due to the crack opening-closing is used to identify the occurrence of the crack. The Wigner-Wille distribution technique is applied to analyze the response signals and the instantaneous frequency is extracted as damage-sensitive feature. The numerical simulations of a breathing crack model were carried out to validate the possibility and effectiveness of the proposed approach. The effects of crack severity and sampling frequency on crack identification were also studied in the simulations respectively. The results show that the proposed method can effectively identify the crack with slight severity without any baseline model or data, and the better the identification obtains as the larger the sampling frequency. The study demonstrates that the proposed approach by using of jointly time-frequency analysis is a promising technique for crack identification.

Dynamics of an autonomous Gilpin–Ayala competition model with random perturbation

2021 ◽  
pp. 2050043
Author(s):  
Jing Fu ◽  
Qixing Han ◽  
Daqing Jiang ◽  
Yanyan Yang
Keyword(s):  
White Noise ◽  
Numerical Simulations ◽  
Positive Solution ◽  
Necessary Conditions ◽  
Random Perturbation ◽  
Sufficient Conditions ◽  
Competition Model ◽  
Interacting Species ◽  
Sufficient And Necessary Conditions ◽  
Global Positive Solution

This paper discusses the dynamics of a Gilpin–Ayala competition model of two interacting species perturbed by white noise. We obtain the existence of a unique global positive solution of the system and the solution is bounded in [Formula: see text]th moment. Then, we establish sufficient and necessary conditions for persistence and the existence of an ergodic stationary distribution of the model. We also establish sufficient conditions for extinction of the model. Moreover, numerical simulations are carried out for further support of present research.

Xây dựng lược đồ chữ ký số an toàn từ các lược đồ định danh

2020 ◽  
Vol 8 (2) ◽  
pp. 27-33
Author(s):  
Võ Đình Linh
Keyword(s):  
Digital Signature ◽  
Necessary Conditions ◽  
Sufficient Condition ◽  
Signature Scheme ◽  
Identification Scheme ◽  
Identification Schemes ◽  
Digital Signature Scheme ◽  
Chosen Message Attack

 Tóm tắt— Trong tài liệu [3], khi trình bày về phương pháp xây dựng lược đồ chữ ký số dựa trên các lược đồ định danh chính tắc nhờ phép biến đổi Fiat-Shamir, tác giả đã chỉ ra “điều kiện đủ” để nhận được một lược đồ chữ ký số an toàn dưới tấn công sử dụng thông điệp được lựa chọn thích nghi là lược đồ định danh chính tắc phải an toàn dưới tấn công bị động. Tuy nhiên, tác giả của [3] chưa chỉ ra “điều kiện cần” đối với các lược đồ định danh chính tắc nhằm đảm bảo tính an toàn cho lược đồ chữ ký số được xây dựng. Do đó, trong bài báo này, chúng tôi hoàn thiện kết quả của [3] bằng việc chỉ ra điều kiện đủ đó cũng chính là điều kiện cần.Abstract— In [3], the author shows that, in order to the digital signature scheme Π' resulting from the Fiat-Shamir transform applied to a canonical identification scheme Π is existentially unforgeable under chosen-message attack then a “sufficient” condition is that the scheme Π has to be secure against a passive attack. However, the author of [3] has not shown the “necessary” conditions for the canonical identification schemes to ensure security of the digital signature scheme Π'. In this paper, we complete this result by showing that sufficient condition is also necessary. 

On the crack opening and energy dissipation in a continuum based disconnected crack model

2020 ◽  
Vol 170 ◽  
pp. 103333 ◽  
Author(s):  
Yiming Zhang ◽  
Zhiran Gao ◽  
Yanyan Li ◽  
Xiaoying Zhuang
Keyword(s):  
Energy Dissipation ◽  
Crack Opening ◽  
Crack Model

A Comparison of Cohesive Crack Model and Crack Band Model in Concrete Fracture

2012 ◽  
Vol 170-173 ◽  
pp. 3375-3380
Author(s):  
Liang Wu ◽  
Ze Li ◽  
Shang Huang
Keyword(s):  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Crack Opening ◽  
Cohesive Crack ◽  
Band Model ◽  
Crack Model ◽  
Concrete Fracture ◽  
Cohesive Crack Model ◽  
Crack Band

The cohesive crack model and the crack band model are two convenient approaches in concrete fracture analysis. They can describe in full the fracture process by the different manner: The entire fracture process zone is lumped into the crack line and is characterized in the form of a stress-displacement law which exhibits softening; or the inelastic deformations in the fracture process zone are smeared over a band of a certain width, imagined to exist in front of the main crack. The correlation of the two models is developed based on a characteristic width of crack band. The analysis shows that they can yield about the same results if the crack opening displacement in the cohesive crack model is taken as the fracturing strain that is accumulated over the width of the crack band model. Some basic problems are also discussed in finite element analysis.

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