Bending Stiffness Analysis of Elastic Shafts with Three Types of Transverse Cracks

2011 ◽  
Vol 356-360 ◽  
pp. 2197-2204
Author(s):  
Zhong Yi Cai ◽  
He Len Wu ◽  
Xiao Li Zhao ◽  
Jian Ping Zhang
Keyword(s):  
Transverse Crack ◽  
Crack Opening ◽  
Bending Stiffness ◽  
Transverse Cracks ◽  
Stiffness Analysis ◽  
Three Point Bending ◽  
Stiffness Variation ◽  
Opening And Closing ◽  
Published Research ◽  
Breathing Mechanism

The breathing mechanism of a transverse crack in an elastic shaft has been extensively researched. Although many different crack models have been presented, little published research has explored experimentally how the shaft crack breathing mechanism interacts with the change of stiffness during each revolution. This study addressed static analysis of the stiffness of elastic shafts with experimentally-induced fatigue, welding or wire cut transverse cracks. Bending stiffness was measured from different angles under a three point bending fixture, to efficiently define the correct periodical stiffness variation for different crack types. The opening and closing of each crack (breathing effect) were investigated for their association with shaft stiffness. It was found that width of the crack opening gap is a crucial factor which influences the crack breathing behaviour. Experimental results are expected to assist with crack diagnosis.

An Experimental Study of Breathing Mechanism for the Transversely Cracked Shafts

2011 ◽  
Vol 338 ◽  
pp. 547-552
Author(s):  
He Len Wu ◽  
Zhong Yi Cai ◽  
Ke Qin Xiao
Keyword(s):  
Fatigue Crack ◽  
Diagnostic Techniques ◽  
Transverse Cracks ◽  
On Line ◽  
Stiffness Variation ◽  
Heavy Loads ◽  
Opening And Closing ◽  
Cracked Shafts ◽  
Breathing Mechanism ◽  
Line Crack

Shaft fatigue crack is one of the most common defects in rotating equipment, due to its extensive operation with continuous heavy loads. Finding an efficient way to evaluate the true stiffness variation due to the crack rotation is the key step to develop both on-line and off-line crack diagnostic techniques. This study analyzed time-variant bending stiffness of elastic shafts with experimentally-induced fatigue, welding and wire cut transverse cracks. It was found that crack gap has a significant effect on the opening and closing behaviour of the transverse crack. As in the case of a cut crack, large crack gap could completely prevent the crack from closing during rotation. A fatigue crack without a clear gap shows a typical opening and closing behavior. Further, it remains fully closed within a small angular range and most of time it is partially closed. It was also observed that both switch and harmonic models cannot describe periodic stiffness variation well enough to represent the actual breathing function of the fatigue crack.

The Vibrational Behavior of a Multi-Shaft, Multi-Bearing System in the Presence of a Propagating Transverse Crack

1984 ◽  
Vol 106 (1) ◽  
pp. 146-153 ◽  
Author(s):  
W. G. R. Davies ◽  
I. W. Mayes
Keyword(s):  
Transverse Crack ◽  
Crack Opening ◽  
Crack Depth ◽  
Bending Moment ◽  
Theoretical Treatment ◽  
Dynamic Stresses ◽  
Vibrational Behavior ◽  
Dynamic Bending ◽  
Opening And Closing ◽  
Bearing System

The effects of a transverse crack on the dynamics of a multi-rotor, multi-bearing system have been studied experimentally using a spin rig. It is concluded that except for very large cracks, the vibrational behavior is similar to that of a slotted shaft with additional excitation due to the crack opening and closing. It confirms the theory, described elsewhere, that it is possible to calculate the behavior of a cracked and/or slotted rotor for a realistic turbogenerator model for crack depths sufficient to give a measurable vibration vector change. The dynamic stresses in the cracked shaft were also measured. The results show how the dynamic bending moment at the crack tip depends on the speed of rotation of the shaft and the crack depth. The results are compared with a theoretical treatment previously reported and good agreement obtained. It is concluded that for crack depths in excess of one third the way through, the shaft the dynamic bending moment must be used for fracture mechanics calculations.

Analytical Buckling Loads of Columns Weakened Simultaneously with Transverse Cracks and Partial Delamination

2019 ◽  
Vol 19 (03) ◽  
pp. 1950027 ◽  
Author(s):  
Igor Planinc ◽  
Simon Schnabl
Keyword(s):  
Mathematical Model ◽  
Analytical Solution ◽  
Boundary Conditions ◽  
Parametric Study ◽  
Transverse Crack ◽  
Transverse Cracks ◽  
Buckling Loads ◽  
Crack Location ◽  
Benchmark Solution ◽  
First Time

This paper focuses on development of a new mathematical model and its analytical solution for buckling analysis of elastic columns weakened simultaneously with transverse open cracks and partial longitudinal delamination. Consequently, the analytical solution for buckling loads is derived for the first time. The critical buckling loads are calculated using the proposed analytical model. A parametric study is performed to investigate the effects of transverse crack location and magnitude, length and degree of partial longitudinal delamination, and different boundary conditions on critical buckling loads of weakened columns. It is shown that the critical buckling loads of weakened columns can be greatly affected by all the analyzed parameters. Finally, the presented results can be used as a benchmark solution.

Evaluation of Microscopic Deformation in CFRP Laminates with Delamination by Micro-Grid Methods

1998 ◽  
Vol 32 (1) ◽  
pp. 83-100 ◽  
Author(s):  
Nobuo Takeda ◽  
Shinji Ogihara ◽  
Satoshi Suzuki ◽  
Akira Kobayashi
Keyword(s):  
Crack Opening ◽  
Displacement Fields ◽  
Transverse Cracks ◽  
Opening Displacement ◽  
Cfrp Laminates ◽  
Edge Surface ◽  
Micro Grid ◽  
Microscopic Deformation ◽  
Micro Grids ◽  
Specimen Edge

Micro-grid methods were applied to measure displacements in 90° ply in CFRP cross-ply laminates with only transverse cracks or with both transverse cracks and delaminations. The COD (crack opening displacement) of the transverse cracks were also measured. Micro-grids were printed on the specimen edge surfaces by using the photo-lithography technique. The displacement fields of the specimen edge surface obtained from the experiment were compared with McCartney's [1] and Lee et al.'s [2] analyses which predicted the displacement field of a cross-ply laminate with only transverse cracks. Furthermore these analyses were modified to consider the existence of delamination.

scholarly journals Crack Opening and Closing Behaviors under Cyclic Loadings in Annealed Copper.

2002 ◽  
Vol 45 (4) ◽  
pp. 487-494
Author(s):  
Kenji HATANAKA ◽  
Junji OHGI ◽  
Akio TOMIOKA ◽  
Katsuhito KAJI
Keyword(s):  
Crack Opening ◽  
Opening And Closing ◽  
Annealed Copper

Investigation and Analysis on Transverse Crack Spacing Distribution in Continuously Reinforced Concrete Pavement in China

2013 ◽  
Vol 690-693 ◽  
pp. 1817-1820
Author(s):  
Quan Man Zhao ◽  
Hong Liang Zhang ◽  
Yan Hui Wang
Keyword(s):  
Reinforced Concrete ◽  
Transverse Crack ◽  
Concrete Pavement ◽  
Crack Spacing ◽  
Transverse Cracks ◽  
Spacing Distribution ◽  
Field Investigations ◽  
The Us

The longterm field investigations in the US showed that punchouts were the most important distress in continuously reinforced concrete pavement (CRCP) and often developed in the cluster cracking with the crack spacing of 0.3m-0.6m. But, it was not sure whether punchouts were the most important distress in CRCP in China, so this paper carried out field investigations on several CRC pavements in China. Results showed that punchouts were the most serious distress and often occurred in cluster crack regions. Furthermore, this paper analyzed the transverse crack spacing distribution. Results showed that the transverse cracks spacing distribution followed Weibull’s distribution.

scholarly journals ROADWAY ROUGHNESS RESEARCH AND CAUSES DETERIORATION ANALYSIS

2017 ◽  
Vol 1 (48) ◽  
pp. 251-257
Author(s):  
D. O. Pavlyuk ◽  
V. P. Tereshchuk ◽  
V. S. Chapovskyi
Keyword(s):  
Detailed Analysis ◽  
Transverse Crack ◽  
Road Construction ◽  
Transverse Cracks ◽  
Research Results ◽  
The Road ◽  
Road Profile ◽  
On The Road ◽  
The City

The article deals with modern directions of domestic and foreign smoothness research coverage on the roads.  The problem of causes changes establishing in smoothness coverage related to the irregularities in the procedure of road construction layers is highlighted. The research results of the trafficway smoothness and its causes deterioration analysis, performed by operation of roads and airfields laboratory at National Transport University on research road area H-18 around the city Buchach is shown.  By the research results the road profile is drawn and the detailed analysis of road topping smoothness changes during road operation is done. Samples at the specific points on the road topping is taken: in one place it is a transverse crack, in another – without noticeable defects. It is established that road profile hollows and transverse cracks caused by black layers uneven thickness along the road.

scholarly journals The Influence of Crack Modes on the Elastic Wave Propagation Characteristics in a Non-uniform Rotating Shaft

2018 ◽  
Author(s):  
Yimin Wei ◽  
Xuan Shi ◽  
Qi Liu ◽  
Wenhua Chen
Keyword(s):  
Elastic Wave ◽  
Elastic Waves ◽  
Transverse Crack ◽  
Propagation Characteristics ◽  
Mode Iii ◽  
Transverse Cracks ◽  
Rotating Shaft ◽  
Rotating Speed ◽  
Local Flexibility ◽  
The Media

The vibration propagates in a media such as a shaft in the form of elastic waves. The propagation characteristics of the waves are affected by the geometry of the media, the material properties as well as the cracks. The study to elastic waves propagating in a shaft with transverse cracks can help to detect them. The transverse crack possesses different crack modes due to different external loads. The influence of the crack mode, the location and the depth to the propagation characteristics is investigated in this paper. Firstly, the local flexibility coefficients with three different modes are deduced. And then, the transfer matrix of the elastic wave can be obtained. Finally, the influence of the crack mode, the location and the depth of the transverse crack as well as the rotating speed to the propagation characteristics is then studied, both in a numerical and an experimental way. It’s found that mode III is the most suitable mode in this paper, the location of the crack will make the stopbands fluctuating, the depth mainly affects the bandwidth of the stopbands, and the increase of the rotating speed will shift up the stopbands without changing their bandwidths.

Time-varying mesh stiffness analysis of a single-roller enveloping hourglass worm gear

2018 ◽  
Vol 233 (2) ◽  
pp. 578-592
Author(s):  
Qibin Wang ◽  
Bo Zhao ◽  
Xianguang Kong ◽  
Hongbo Ma ◽  
Jiantao Chang
Keyword(s):  
Shear Stiffness ◽  
Bending Stiffness ◽  
Worm Gear ◽  
Mechanical Transmission ◽  
Radial Compression ◽  
Time Varying ◽  
The Finite Element Method ◽  
Mesh Stiffness ◽  
Stiffness Analysis ◽  
New Type

As a new type of transmission, the single-roller enveloping hourglass worm gear (SEHWG) is widely used in precision mechanical transmission systems. Time-varying mesh stiffness (TVMS) is one of the most important excitations, which has great influences on the dynamic characteristics of SEHWG systems. In this paper, a model for calculating the TVMS of the SEHWG is proposed, in which bending stiffness, shear stiffness, radial compression stiffness, and foundation stiffness are considered in the worm stiffness calculation. And bending stiffness, shear stiffness, and foundation stiffness are considered in the worm wheel stiffness calculation. The process of calculating the periodical TVMS of the SEHWG is also presented. Then, the TVMS of the SEHWG by the proposed method is compared with that of the finite element method for the model validation. Finally, the influences of the roller radii on TVMS are analyzed. The results show that the mesh stiffness of the TVMS has a tendency to rise first and then fall with the increasing roller radii.

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