On the Direction of Fatigue Cracks in Polycrystalline Ingot Iron

1952 ◽  
Vol 19 (1) ◽  
pp. 54-56
Author(s):  
F. A. McClintock
Keyword(s):  
Statistical Analysis ◽  
Shear Failure ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Tensile Failure ◽  
Bending Fatigue ◽  
Polycrystalline Iron

Abstract A statistical analysis is developed to show how a microscopic shear failure can result in the apparent tensile failure of polycrystalline iron in rotary bending fatigue tests.

Statistical Analysis of Pit Dimensions for Pre-Corroded AA 7075-T6

2014 ◽  
Vol 906 ◽  
pp. 259-262 ◽  
Author(s):  
Yong Fang Huang ◽  
Li Jie Chen ◽  
Xu Bin Ye
Keyword(s):  
Statistical Analysis ◽  
Fatigue Cracks ◽  
Gumbel Distribution ◽  
Fatigue Tests ◽  
Specimen Surface ◽  
Aa 7075 ◽  
Corrosion Pits ◽  
Log Normal ◽  
Aluminum Alloy 7075 ◽  
Log Normal Distribution

Aluminum alloy 7075-T6 specimens were corroded in 3.5% NaCl solution for 120 hours and 240 hours, respectively. Morphology and dimensions of corrosion pits on specimen surface were inspected with white light confocal profiler. Statistical analysis shows that pit dimensions can be fitted well with log-normal and Gumbel distribution. After surface inspections, we performed high-cycle fatigue tests for the specimens. Fracture analysis shows that fatigue cracks initiate from single pit or two adjacent pits, and the crack-initiation pit shape and dimensions were examined with SEM. It is found that initiation pit dimensions can be well described with the log-normal distribution. Additionally, initiation pit dimensions are significantly larger than those measured on specimen surface before fatigue tests.

Investigation of Very High Cycle Fatigue Behavior of TC17 Alloy

2011 ◽  
Vol 295-297 ◽  
pp. 1311-1314
Author(s):  
Li Cheng ◽  
Chao Gao ◽  
Jing Sheng Shen ◽  
Ning Li ◽  
Wei Chen ◽  
...  
Keyword(s):  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Test Technique ◽  
Bending Fatigue ◽  
Very High Cycle Fatigue ◽  
Ultrasonic Fatigue ◽  
Very High ◽  
Ultrasonic Fatigue Test

According to the loading characteristics of engine blades, a vibration bending fatigue system by using the ultrasonic fatigue test technique has been developed and the specimen is designed by finite element method, fatigue tests of TC17 between 106and 109cycles have been completed in this paper. The results show that the fatigue life of specimen increases over 107cycles and the initiation of fatigue cracks transfers from only in the surface of specimen to both in the surface and the sub-surface with loading decreasing.

scholarly journals The role of pores and microstructural heterogeneity on the tooth root fatigue strength of sintered spur gears

2018 ◽  
Vol 165 ◽  
pp. 02011
Author(s):  
Matteo Benedetti ◽  
Vigilio Fontanari ◽  
Alberto Molinari ◽  
Pietro Valcozzena ◽  
Wolfgang Pahl
Keyword(s):  
Fatigue Strength ◽  
Fatigue Cracks ◽  
High Strength ◽  
Fatigue Tests ◽  
Spur Gears ◽  
Tooth Root ◽  
Bending Fatigue ◽  
Microstructural Heterogeneity ◽  
Bainitic Microstructure ◽  
Engine Components

The automotive industry employs a considerable amount of sintered parts, mainly as transmission and engine components. Gears are the parts that mostly benefit, in terms of cost saving, from the near net shape P/M technology. However, the porosity along with the heterogeneous microstructure can detrimentally affect the mechanical behaviour, especially the fatigue strength. The possibility of increasing sintered density up to 90% and more, the use of high strength alloys, as well as post sintering treatments have been extensively investigated obtaining consistent increases in the fatigue strength. The present study focuses on the effects of porosity and microstructure on tooth root bending fatigue of small module spur gears. The aim is to investigate the synergistic contribution of pore morphology and microstructure heterogeneity to the initiation of fatigue cracks and to the following crack paths. High density parts produced by high strength pre-alloyed powders were studied. Part of the specimens was case-hardened to obtain a martensitic/bainitic microstructure in the surface layer. Bending fatigue tests up to a fatigue endurance of three million cycles were performed. A careful fractographic analysis was conducted. The obtained results were discussed using the fracture mechanics approach of Murakami, considering the pores as pre-existing defects, whose propagation strongly depends on the microstructural heterogeneity.

Four Point Bending Fatigue Tests of Forged Ti 6Al 4V

2009 ◽  
Vol 51 (9) ◽  
pp. 580-586 ◽  
Author(s):  
Bernd Oberwinkler ◽  
Martin Riedler ◽  
Heinz Leitner ◽  
Ataollah Javidi
Keyword(s):  
Fatigue Tests ◽  
Bending Fatigue ◽  
Four Point Bending

Bending fatigue of single-wall and double-wall corrugated paperboards under sinusoidal and random loads

2021 ◽  
pp. 109963622110204
Author(s):  
Zhi-Wei Wang ◽  
Yang-Zhou Lai ◽  
Li-Jun Wang
Keyword(s):  
Energy Dissipation ◽  
Fatigue Failure ◽  
Fatigue Tests ◽  
Stiffness Degradation ◽  
Random Load ◽  
Bending Fatigue ◽  
Random Loads ◽  
Vibration Fatigue ◽  
Sinusoidal Load ◽  
Double Wall

The bending fatigue tests of single-wall and double-wall corrugated paperboards were conducted to obtain the εrms– N curves under sinusoidal and random loads in this paper. The εrms– N equation of corrugated paperboard can be described by modified Coffin–Manson model considering the effect of mean stress. Four independent fatigue parameters are obtained for single-wall and double-wall corrugated paperboards. The εrms– N curve under random load moves left and rotates clockwise compared with that under sinusoidal load. The fatigue life under random load is much less than that under sinusoidal load, and the fatigue design of corrugated box should be based on the fatigue result under random load. The stiffness degradation and energy dissipation of double-wall corrugated paperboard before approaching fatigue failure are very different from that of single-wall one. For double-wall corrugated paperboard, two turning points occur in the stiffness degradation, and fluctuation occurs in the energy dissipation. Different from metal materials, the bending fatigue failure of corrugated paperboard is a process of wrinkle forming, spreading, and folding. The results obtained have practical values for the design of vibration fatigue of corrugated box.

Single wire fretting fatigue tests for electrical conductor bending fatigue evaluation

Wear ◽  
1995 ◽  
Vol 181-183 ◽  
pp. 537-543 ◽  
Author(s):  
Z.R. Zhou ◽  
S. Goudreau ◽  
M. Fiset ◽  
A. Cardou
Keyword(s):  
Fretting Fatigue ◽  
Fatigue Tests ◽  
Electrical Conductor ◽  
Single Wire ◽  
Bending Fatigue ◽  
Fatigue Evaluation

scholarly journals Failure Process Simulation of Interlayered Rocks under Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Chi Yao ◽  
Sizhi Zeng ◽  
Jianhua Yang
Keyword(s):  
Shear Failure ◽  
Failure Process ◽  
Strength Criterion ◽  
Tensile Failure ◽  
Strength Anisotropy ◽  
Rigid Block ◽  
Bedding Planes ◽  
Typical Experiment ◽  
Confining Pressures ◽  
Spring Method

Anisotropy in strength and deformation of rock mass induced by bedding planes and interlayered structures is a vital problem in rock mechanics and rock engineering. The modified rigid block spring method (RBSM), initially proposed for modeling of isotropic rock, is extended to study the failure process of interlayered rocks under compression with different confining pressures. The modified rigid block spring method is used to simulate the initiation and propagation of microcracks. The Mohr–Coulomb criterion is employed to determine shear failure events and the tensile strength criterion for tensile failure events. Rock materials are replaced by an assembly of Voronoi-based polygonal blocks. To explicitly simulate structural planes and for automatic mesh generation, a multistep point insertion procedure is proposed. A typical experiment on interlayered rocks in literature is simulated using the proposed model. Effects of the orientation of bedding planes with regard to the loading direction on the failure mechanism and strength anisotropy are emphasized. Results indicate that the modified RBSM model succeeds in capturing main failure mechanisms and strength anisotropy induced by interlayered structures and different confining pressures.

Study on Failure of Rock Mass around Deep Tunnel

2011 ◽  
Vol 99-100 ◽  
pp. 370-374 ◽  
Author(s):  
Yue Hong Qian ◽  
Ting Ting Cheng ◽  
Xiang Ming Cao ◽  
Chun Ming Song
Keyword(s):  
Rock Mass ◽  
Stress Field ◽  
Failure Modes ◽  
Shear Failure ◽  
Simple Function ◽  
Tensile Failure ◽  
Deep Tunnel ◽  
Main Mode

During excavating the problem of unloading is a dynamic one essentially. Assuming the unloading ruled by a simple function and based on the Hamilton principal, the distribution of the stress field nearby the tunnel is obtained. The characteristics of the failure nearby the tunnel are analyzed considering the shear failure and tensile failure. The results show that the main mode of the shear failure, intact and tensile failure occurs from the tunnel. The characteristic of the shear failure, intact and tensile failure are one of the likely failure modes.

scholarly journals Failure Characteristics and Mechanism of Multiface Slopes under Earthquake Load Based on PFC Method

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Tao Yang ◽  
Yunkang Rao ◽  
Huailin Chen ◽  
Bing Yang ◽  
Jiangrong Hou ◽  
...  
Keyword(s):  
Moisture Content ◽  
Failure Mechanism ◽  
Failure Modes ◽  
Shear Failure ◽  
Shaking Table ◽  
Tensile Failure ◽  
Particle Flow Code ◽  
Shear Cracks ◽  
Local Shear ◽  
Shear Slip

Understanding the failure mechanism and failure modes of multiface slopes in the Wenchuan earthquake can provide a scientific guideline for the slope seismic design. In this paper, the two-dimensional particle flow code (PFC2D) and shaking table tests are used to study the failure mechanism of multiface slopes. The results show that the failure modes of slopes with different moisture content are different under seismic loads. The failure modes of slopes with the moisture content of 5%, 8%, and 12% are shattering-shallow slip, tension-shear slip, and shattering-collapse slip, respectively. The failure mechanism of slopes with different water content is different. In the initial stage of vibration, the slope with 5% moisture content produces tensile cracks on the upper surface of the slope; local shear slip occurs at the foot of the slope and develops rapidly; however, a tensile failure finally occurs. In the slope with 8% moisture content, local shear cracks first develop and then are connected into the slip plane, leading to the formation of the unstable slope. A fracture network first forms in the slope with 12% moisture content under the shear action; uneven dislocation then occurs in the slope during vibration; the whole instability failure finally occurs. In the case of low moisture content, the tensile crack plays a leading role in the failure of the slope. But the influence of shear failure becomes greater with the increase of the moisture content.

Gear root bending strength: a comparison between Single Tooth Bending Fatigue Tests and meshing gears

2021 ◽  
pp. 1-17
Author(s):  
Luca Bonaiti ◽  
Ahmed Bayoumi Mahmoud Bayoumi ◽  
Franco Concli ◽  
Francesco Rosa ◽  
Carlo Gorla
Keyword(s):  
Failure Modes ◽  
Bending Strength ◽  
Gear Tooth ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Gear Design ◽  
Single Tooth ◽  
Actual Strength ◽  
Meshing Gears ◽  
Definition Of

Abstract Gear tooth breakage due to bending fatigue is one of the most dangerous failure modes of gears. Therefore, the precise definition of tooth bending strength is of utmost importance in gear design. Single Tooth Bending Fatigue (STBF) tests are usually used to study this failure mode, since they allow to test gears, realized and finished with the actual industrial processes. Nevertheless, STBF tests do not reproduce exactly the loading conditions of meshing gears. The load is applied in a pre-determined position, while in meshing gears it moves along the active flank; all the teeth can be tested and have the same importance, while the actual strength of a meshing gear, practically, is strongly influenced by the strength of the weakest tooth of the gear. These differences have to be (and obviously are) taken into account when using the results of STBF tests to design gear sets. The aim of this paper is to investigate in detail the first aspect, i.e. the role of the differences between two tooth root stress histories. In particular, this paper presents a methodology based on high-cycle multi-axial fatigue criteria in order to translate STBF test data to the real working condition; residual stresses are also taken into account

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