Torsional Dynamic Response of a Shaft With Longitudinal and Circumferential Cracks

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
H. Abdi ◽  
H. Nayeb-Hashemi ◽  
A. M. S. Hamouda ◽  
A. Vaziri
Keyword(s):  
Dynamic Response ◽  
Resonance Frequency ◽  
Torsional Rigidity ◽  
Crack Depth ◽  
Longitudinal Crack ◽  
Element Analysis ◽  
Crack Location ◽  
Circumferential Crack ◽  
Turbo Generator ◽  
Resonance Frequencies

Turbo generator shafts are often subjected to cyclic torsion resulting in formation of large longitudinal cracks as well as circumferential cracks. The presence of these cracks could greatly impact the shaft resonance frequencies. In this paper, dynamic response of a shaft with longitudinal and circumferential cracks is investigated through a comprehensive analytical study. The longitudinally cracked section of the shaft was modeled as an uncracked shaft with reduced torsional rigidity. Torsional rigidity correction factor (i.e., the ratio of torsional rigidity of the cracked shaft to that of the uncracked shaft) was obtained from finite element analysis and was shown to be only a function of crack depth to the shaft radius. The resonance frequency and frictional energy loss of a shaft with a longitudinal crack were found little affected by the presence of the crack as long as the crack depth was less than 20% of the shaft radius even if the entire shaft is cracked longitudinally. Moreover, we showed that the longitudinal crack location could be more conveniently identified by monitoring the slope of the torsional response along the shaft. The circumferential crack was modeled as a torsional spring with a torsional damping. The torsion spring and damping constants were obtained using fracture mechanics. For a shaft with both a longitudinal crack and a circumferential crack, the resonance frequency was governed by the longitudinal crack when the circumferential crack depth was less than 30% of the shaft radius.

scholarly journals The Effects of Longitudinal and Circumferential Cracks on the Torsional Dynamic Response of Shafts

2013 ◽  
Author(s):  
M. Nabian ◽  
A. Vaziri ◽  
M. Olia ◽  
H. Nayeb-Hashemi
Keyword(s):  
Dynamic Response ◽  
Resonance Frequency ◽  
Crack Surface ◽  
Torsional Rigidity ◽  
Peak Response ◽  
Torsional Spring ◽  
Turbo Generator ◽  
Resonance Frequencies ◽  
Cracked Shafts ◽  
Cracked Shaft

Turbo generator shafts are manufactured through the extrusion process. This results in formation of weak planes along the extrusion direction. Under service loading (e.g. cyclic torsion due to electrical line faults), large longitudinal cracks often form in these shafts before the appearance of any circumferential cracks. The presence of these cracks could severely compromise the shaft resonance frequencies. Here, we investigated the dynamic response of solid turbo generator shafts with longitudinal and circumferential cracks. The longitudinal cracked section of the shaft section was modeled as a shaft with reduced effective torsional rigidity. The effective torsional rigidity was found to be a function of ratio of crack depth to the shaft radius only. The circumferential cracked section was modeled as a torsional spring, with the torsional spring constant determined using fracture mechanics principles. It was found that the resonance frequency of the shaft may be little affected by the presence of a longitudinal crack. The resonance frequencies of the shaft with the circumferential crack depend on the crack length and its location. The effects of crack surface interactions for both longitudinal and circumferential cracks were also investigated. For circumferential cracked shafts, the sever crack surface interaction results in the peak response frequency approaches to that of un-cracked shafts. However the frequency where the peak response occurs for a longitudinally-cracked shaft generally exceeds that of un-cracked shaft first resonance frequency.

Torsional Dynamics Response of Shafts with Longitudinal and Circumferential Cracks

2018 ◽  
Author(s):  
Mohsen Nabian ◽  
Mohammad Ali Nabian ◽  
Hamid Nayeb Hashemi
Keyword(s):  
Crack Surface ◽  
Torsional Rigidity ◽  
Crack Depth ◽  
Longitudinal Crack ◽  
Extrusion Process ◽  
Circumferential Crack ◽  
Torsional Spring ◽  
Resonance Frequencies ◽  
Dynamics Response ◽  
Longitudinal Cracks

Turbo generators shafts are manufactured through the extrusion process. This results in formation of weak planes along the extrusion process. It has been observed that large longitudinal cracks often form in these shafts before any circumferential cracks when these shafts are subjected to cyclic torsion due to electrical line faults. The presence of these cracks could severely compromise the shaft resonance frequencies. Dynamic response of shafts with longitudinal and circumferential cracks is investigated. The longitudinal cracked section of the shaft section is modeled as a shaft with reduced torsional rigidity. The torsional rigidity is obtained as a function of the crack depth. It was found for various shaft diameters, torsional rigidity could be represented as a function of crack depth/ shaft radius only. The circumferential cracked section is modeled as a torsional spring. The torsional spring constant has been obtained using fracture mechanics. It was found the resonance frequency of the shaft may be little affected by the presence of longitudinal crack. The resonance frequencies of the shaft with the circumferential crack depend on the crack length and location. The effects of crack surface interactions for both longitudinal and circumferential cracks were also investigated.

Response of Cracked Cantilever Beam Subjected to Traversing Mass

2015 ◽  
Author(s):  
Shakti P. Jena ◽  
Dayal R. Parhi ◽  
Devasis Mishra
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Dynamic Response ◽  
Numerical Method ◽  
Cantilever Beam ◽  
Crack Depth ◽  
Numerical Procedure ◽  
Element Analysis ◽  
Crack Location

The present work emphasizes the dynamic response of double cracked cantilever beam subjected to a traversing mass. The cracks are located at different positions of the beam with random crack depths. The response of the damaged structure has been evaluated employing a numerical procedure of Runge-Kuuta method. The effects of crack depth, traversing mass, traversing speed and crack location on the response of the structure are studied. Finite element analysis (FEA) using the commercial ANSYS 15 has been presented to validate the adopted numerical method.

Parametric Evaluation on the Response of Damaged Simple Supported Structure Under Transit Mass

2017 ◽  
Author(s):  
Shakti P. Jena ◽  
Dayal R. Parhi ◽  
B. Subbaratnam
Keyword(s):  
Finite Element Analysis ◽  
Integral Method ◽  
Critical Speed ◽  
Crack Depth ◽  
Element Analysis ◽  
Simply Supported ◽  
Crack Location ◽  
Integral Converge ◽  
Duhamel Integral ◽  
Ansys Workbench

In the present article, the responses of a double cracked simply supported beam have been investigated. The responses of the structure are determined using Duhamel integral method numerically and validated with finite element analysis (FEA) using ANSYS WORKBENCH 2015 along with experimental verifications. The mass is moving on the structure in terms of critical speed of the structure. The normalized deflections of the structure at different damaged configurations are calculated. The influences of speed, mass, crack depth and crack location on the structures response are investigated. It is observed that the results obtained from Duhamel integral converge well with FEA and experimental verifications.

Finite Element Analysis and Experimental Studies on the Thickness Resonance of Piezocomposite Transducers

1996 ◽  
Vol 18 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Wenkang Qi ◽  
Wenwu Cao
Keyword(s):  
Finite Element ◽  
Resonance Frequency ◽  
Electromechanical Coupling ◽  
Effective Medium Theory ◽  
Experimental Studies ◽  
Effective Medium ◽  
Electromechanical Coupling Coefficient ◽  
Element Analysis ◽  
Medium Theory ◽  
Resonance Frequencies

Finite element method (FEA) has been used to calculate the thickness resonance frequency and electromechanical coupling coefficient kt for 2–2 piezocomposite transducers. The results are compared with that of the effective medium theory and also verified by experiments. It is shown that the predicted resonance frequencies from the effective medium theory and the unit cell modeling using FEA deviate from the experimental observations for composite systems with a ceramic aspect ratio (width/length) more than 0.4. For such systems, full size FEA modeling is required which can provide accurate predictions of the resonance frequency and thickness coupling constant kt.

Crack Growth in Twisted Rubber Disks. Part 3. Effects of Crack Depth and Location

2003 ◽  
Vol 76 (5) ◽  
pp. 1276-1289 ◽  
Author(s):  
A. N. Gent ◽  
O. H. Yeoh
Keyword(s):  
Fracture Energy ◽  
Crack Depth ◽  
Element Analysis ◽  
Crack Location ◽  
Crack Behavior ◽  
Disk Size ◽  
Shallow Crack ◽  
Deep Crack ◽  
Disk Height ◽  
Long Cylinder

Abstract A simple analysis of the fracture energy for a shallow ring crack in a twisted rubber disk is presented and compared to a linear fracture mechanics solution for a similar crack in an infinitely long cylinder. The analysis predicts that the fracture energy increases linearly with crack depth. Since a previous analysis shows that the fracture energy subsequently decreases with crack depth when the crack is deep, it follows that the fracture energy passes through a peak as it transitions from shallow crack to deep crack behavior. The transition occurs when the crack depth becomes comparable to a fraction of the disk height. The analysis is supported by the results of finite element analysis. In addition, the effects of disk size, crack location (in the middle of the cylinder vs. at the bonded ends) and material properties are also considered.

scholarly journals Residual life estimation of structural beam using experimental and numerical modal analysis methods

2020 ◽  
Vol 4 (2) ◽  
pp. 135-146
Author(s):  
Ganda Anand Siva ◽  
Shinigam Ramakrishna
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Residual Life ◽  
Crack Depth ◽  
Common Element ◽  
Cracked Beam ◽  
Element Analysis ◽  
Crack Location ◽  
Parametric Studies ◽  
Ship Propeller

A structural beam is a common element in many mechanical structures such as ship propeller shaft, crane boom, and air craft wings. In the present paper experimental and numerical modal analysis are carried out for estimating the damage detection, geometric location of the damage, severity of damage and residual life of structural beam to prevent unexpected failures of the mechanical structures. Experimental and numerical modal analysis results for healthy and cracked beam are compared for validation of numerical methodology used in the present paper. Experimental modal analysis is performed on both healthy and cracked beam with the help of impact hammer, acceleration sensor and FFT analyzer associated with EDM (Engineering Data Management) software. Modal tests are conducted using impact method on selected locations of the entire healthy and cracked beam to find the first three natural frequencies, which are used to detect the presence of damage and geometric location of the damage. Three parametric studies are carried out to know the effect of crack depth, crack location and crack orientation on the natural frequencies of the cracked beam. Finally,  residual life of a healthy and cracked beam was estimated using Basiquin’s equation and finite element analysis software called ANSYS 18.1.

Crake Effect on the Dynamic Characteristics of Elastically Coupled Beams

2011 ◽  
Vol 110-116 ◽  
pp. 328-336
Author(s):  
Samer A. M. Al-Said
Keyword(s):  
Dynamic Characteristics ◽  
Crack Depth ◽  
Three Dimensional ◽  
Model Verification ◽  
Elastic Coupling ◽  
Element Analysis ◽  
Crack Location ◽  
Dimensional Finite Element ◽  
Coupled Beams ◽  
Three Dimensional Finite Element

Simple mathematical model that describes the lateral vibration of elastically coupled cracked cantilever beams carrying rigid disk at their tips is derived. The derived model is used to study the effect of elastic coupling, crack depth and location on the dynamic characteristics of the system. The cracked beam is presented as two beams connected with torsional spring at the crack location. Model verification is carried out using three dimensional finite element analysis using ANSYS program, the verification results showed good agreement with that obtained from the proposed model. The study reveals that the first system natural frequency is affected by the crack and the elastic coupling.

Survey and Analysis of the Regularity of the Surface Crack in the Loess Tunnel of the Special Passenger Line

2011 ◽  
Vol 90-93 ◽  
pp. 2258-2264 ◽  
Author(s):  
Xin Qiang Gao ◽  
Yong Quan Zhu ◽  
Chao Liang Ye
Keyword(s):  
Surface Crack ◽  
Seismic Reflection ◽  
Field Survey ◽  
Crack Depth ◽  
Longitudinal Crack ◽  
Electrical Method ◽  
Geophysical Exploration ◽  
Circumferential Crack ◽  
Shallow Area ◽  
Tunnel Entrance

We have done a survey about the surface crack of the loess tunnel of Zheng-xi passenger railway by field survey, geophysical exploration test and pit detection and also have researched the produced regularity of the surface crack of the loess tunnel, especially about in the depth. The result of the survey and the detection indicates that: (1)The surface crack is mostly visible in the shallow area of the loess tunnel entrance. The visible width of the surface is extensive (0.2~200mm) and it is mostly visible in the tunnel, the depth of which is below 60m. The visible or wide cracks mostly appear in the area whose surface settlement is above 80mm. The width of the surface crack of the tunnel, which has a more shallow depth and a larger settlement, is much wider. (2)The effect of the High-density electrical method reflecting the development of the surface crack is obvious. The method of seismic reflection wave and seismic imaging is more accurate than Rayleigh wave in interpreting depth development of the crack. (3)There are two kinds of performance of the surface crack: longitudinal crack that inclines to the inside on both side of the tunnel and circumferential crack perpendicular to the axis of the tunnel. (4)The visible crack depth of the surface crack is limited, which is about 3.0~10m and it always doesn't reach the top of the tunnel. The depth by the geophysical exploration test is much more depth, which is about 10~15m.

scholarly journals Fault Diagnosis of Beam-Like Structure Using Modified Fuzzy Technique

2014 ◽  
Vol 2014 ◽  
pp. 1-18 ◽  
Author(s):  
Dhirendranath Thatoi ◽  
Sasanka Choudhury ◽  
Prabir Kumar Jena Jena
Keyword(s):  
Finite Element ◽  
Fuzzy Logic ◽  
Fuzzy Controller ◽  
Crack Depth ◽  
Research Work ◽  
Mode Shapes ◽  
Engineering Structures ◽  
Element Analysis ◽  
Crack Location ◽  
Vibration Signatures

This paper presents a novel hybrid fuzzy logic based artificial intelligence (AI) technique applicable to diagnosis of the crack parameters in a fixed-fixed beam by using the vibration signatures as input. The presence of damage in engineering structures leads to changes in vibration signatures like natural frequency and mode shapes. In the first part of this work, a structure with a failure crack has been analyzed using finite element method (FEM) and retrospective changes in the vibration signatures have been recorded. In the second part of the research work, these deviations in the vibration signatures for the first three mode shapes have been taken as input parameters for a fuzzy logic based controller for calculation of crack location and its severity as output parameters. In the proposed fuzzy controller, hybrid membership functions have been taken. Several fuzzy rules have been identified for prediction of crack depth and location and the results have been compared with finite element analysis. A database of experimental results has also been considered to check the robustness of the fuzzy controller. The results show that predictions for the nondimensional crack location, α, deviate ~2.4% from experimental values and for the nondimensional crack depth, δ, are less than ~−2%.

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