scholarly journals Discussion: “Effect of Three-Dimensional Near Surface Defects on Rolling and Sliding Contact Fatigue” (Liu, M., and Farris, T. N., 1994, ASME J. Tribol., 116, pp. 841–848)

1994 ◽  
Vol 116 (4) ◽  
pp. 849-849
Author(s):  
L. M. Keer
Keyword(s):  
Surface Defects ◽  
Three Dimensional ◽  
Contact Fatigue ◽  
Sliding Contact ◽  
Near Surface

Effect of Three-Dimensional Near Surface Defects on Rolling and Sliding Contact Fatigue

1994 ◽  
Vol 116 (4) ◽  
pp. 841-848 ◽  
Author(s):  
M. Liu ◽  
T. N. Farris
Keyword(s):  
Stress Distribution ◽  
Fatigue Limit ◽  
Surface Defects ◽  
Near Field ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
The Body ◽  
Sliding Contact ◽  
Element Formulation ◽  
Near Surface

The effect of three-dimensional defects such as voids and inclusions on the sliding contact subsurface stress distribution and fatigue limit is investigated. Three-dimensional finite-infinite boundary elements are utilized to model the body by discretizing its surface and the interface between the solid and the defect. The multidomain boundary element formulation is employed to accurately model the effect of the inclusion on the stress distribution. It is shown that the void has a greater near field effect on the stress distribution while the effect of a stiff inclusion applies over a larger distance. The critical stress points during a load passage are predicted based on a search of the maximum distortional strain energy. The stresses at the critical points are used for the fatigue limit pressure estimation by incorporating the equivalent stress concept with the Haigh diagram. The model predicts that a near surface spherical void of given size and depth reduces the maximum allowable fatigue limit design pressure by 75 percent while a stiff inclusion of the same size, shape, and location reduces it by 25 percent.

scholarly journals Rolling and Rolling-Sliding Contact Fatigue Failure Mechanisms in 32 CrMoV 13 Nitrided Steel—An Experimental Study

2021 ◽  
Vol 11 (21) ◽  
pp. 10499
Author(s):  
Luís Coelho ◽  
António C. Batista ◽  
João Paulo Nobre ◽  
Maria José Marques
Keyword(s):  
Residual Stress ◽  
Fatigue Failure ◽  
Failure Mechanisms ◽  
Contact Fatigue ◽  
Fatigue Tests ◽  
Sliding Contact ◽  
Surface Layers ◽  
Near Surface ◽  
Nitrided Steel ◽  
Inclined Cracks

The aim of this work is to characterize the rolling and rolling-sliding contact fatigue failure mechanisms on the 32CrMoV13 nitrided steel. During rolling contact fatigue tests (RCF), two general features were observed: specimens presenting short lives and rough and sharpened spalling damage and specimens presenting long lives and only microspalling marks. It was possible to determine a contact fatigue limit of 3 GPa. During rolling-sliding contact fatigue tests (RSCF), a clearly different behaviour between the two specimens in contact has been observed: the driver shows circumferential and inclined cracks and only inclined cracks appear in the follower. This behaviour can be understood if the effect of the residual stress state in near-surface layers is considered. Before RCF tests, the residual stresses are compressive in all near-surface layers. After RCF tests, strong residual stress relaxation and even reversing behaviour was observed in the axial direction, which facilitates the surface crack initiation in the circumferential direction at rolling track borders.

Effect of Three-Dimensional Random Surface Roughness on Fatigue Life of a Lubricated Contact

1998 ◽  
Vol 120 (2) ◽  
pp. 159-164 ◽  
Author(s):  
Xiaolan Ai
Keyword(s):  
Surface Roughness ◽  
Fatigue Life ◽  
Effective Stress ◽  
Three Dimensional ◽  
Contact Fatigue ◽  
Random Surface ◽  
Near Surface ◽  
Contact Fatigue Life ◽  
Finishing Processes ◽  
Stress Variations

A means of evaluating the surface roughness effect on contact fatigue life has been proposed. To account for stress variations caused by random surface roughness, an effective stress concept based on damage accumulation theory was employed. A point EHL analysis along with a comprehensive interior stress analysis has been performed to obtain the effective stress field under lubricated conditions. Numerical simulations were performed for surfaces produced by different finishing processes. Results show that surface roughness can cause significant stress variations in the near-surface. As a result, the effective stress at the near-surface is increased. The increased effective stress is responsible for the life reduction of the contact. Life reduction factors for contact surfaces with different finishing processes were compared.

Electron Channelling Contrast Imaging of Dislocations

1990 ◽  
Vol 48 (1) ◽  
pp. 600-601
Author(s):  
J.T. Czernuszka ◽  
N.J. Long ◽  
P.B. Hirsch
Keyword(s):  
Field Emission ◽  
Secondary Electron ◽  
Surface Defects ◽  
Spot Size ◽  
Beam Divergence ◽  
Contrast Imaging ◽  
Scattered Electron ◽  
Near Surface ◽  
Filter System ◽  
Electron Channelling

In the 1970s there was considerable interest in the development of the electron channelling contrast imaging (ECCI) technique for imaging near surface defects in bulk (electron opaque) specimens. The predictions of the theories were realised experimentally by Morin et al., who used a field emission gun (FEG) operating at 40-50kV and an energy filter such that only electrons which had lost no more than a few 100V were detected. This paper presents the results of a set of preliminary experiments which show that an energy filter system is unneccessary to image and characterise the Burgers vectors of dislocations in bulk specimens. The examples in the paper indicatethe general versatility of the technique.A VG HB501 STEM with a FEG was operated at 100kV. A single tilt cartridge was used in the reflection position of the microscope. A retractable back-scattered electron detector was fitted into the secondary electron port and positioned to within a few millimetres of the specimen. The image was acquired using a Synoptics Synergy framestore and digital scan generator and subsequently processed using Semper 6. The beam divergence with the specimen in this position was 2.5 mrads with a spot size of approximately 4nm. Electron channelling patterns were used to orientate the sample.

Direct Plan View FIB Liftout for Near-Surface Defect Analysis in TEM

2013 ◽  
Author(s):  
Max L. Lifson ◽  
Carla M. Chapman ◽  
D. Philip Pokrinchak ◽  
Phyllis J. Campbell ◽  
Greg S. Chrisman ◽  
...  
Keyword(s):  
Failure Analysis ◽  
Silicon Germanium ◽  
Focused Ion Beam ◽  
Surface Defects ◽  
Ion Beam ◽  
Misfit Dislocations ◽  
Tem Analysis ◽  
Plan View ◽  
Near Surface ◽  
Straightforward Method

Abstract Plan view TEM imaging is a powerful technique for failure analysis and semiconductor process characterization. Sample preparation for near-surface defects requires additional care, as the surface of the sample needs to be protected to avoid unintentionally induced damage. This paper demonstrates a straightforward method to create plan view samples in a dual beam focused ion beam (FIB) for TEM studies of near-surface defects, such as misfit dislocations in heteroepitaxial growths. Results show that misfit dislocations are easily imaged in bright-field TEM and STEM for silicon-germanium epitaxial growth. Since FIB tools are ubiquitous in semiconductor failure analysis labs today, the plan view method presented provides a quick to implement, fast, consistent, and straightforward method of generating samples for TEM analysis. While this technique has been optimized for near-surface defects, it can be used with any application requiring plan view TEM analysis.

Thermomechanical Coupling of a Hyper-viscoelastic Truck Tire and a Pavement Layer and its Impact on Three-dimensional Contact Stresses

2021 ◽  
pp. 036119812110171
Author(s):  
Angeli Jayme ◽  
Imad L. Al-Qadi
Keyword(s):  
Contact Stress ◽  
Contact Area ◽  
Three Dimensional ◽  
Interaction Model ◽  
Rolling Resistance ◽  
Contact Stresses ◽  
Thermomechanical Coupling ◽  
Temperature Profiles ◽  
Near Surface ◽  
Truck Tire

A thermomechanical coupling between a hyper-viscoelastic tire and a representative pavement layer was conducted to assess the effect of various temperature profiles on the mechanical behavior of a rolling truck tire. The two deformable bodies, namely the tire and pavement layer, were subjected to steady-state-uniform and non-uniform temperature profiles to identify the significance of considering temperature as a variable in contact-stress prediction. A myriad of ambient, internal air, and pavement-surface conditions were simulated, along with combinations of applied tire load, tire-inflation pressure, and traveling speed. Analogous to winter, the low temperature profiles induced a smaller tire-pavement contact area that resulted in stress localization. On the other hand, under high temperature conditions during the summer, higher tire deformation resulted in lower contact-stress magnitudes owing to an increase in the tire-pavement contact area. In both conditions, vertical and longitudinal contact stresses are impacted, while transverse contact stresses are relatively less affected. This behavior, however, may change under a non-free-rolling condition, such as braking, accelerating, and cornering. By incorporating temperature into the tire-pavement interaction model, changes in the magnitude and distribution of the three-dimensional contact stresses were manifested. This would have a direct implication on the rolling resistance and near-surface behavior of flexible pavements.

scholarly journals Topological correlators and surface defects from equivariant cohomology

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Rodolfo Panerai ◽  
Antonio Pittelli ◽  
Konstantina Polydorou
Keyword(s):  
Quantum Mechanics ◽  
Equivariant Cohomology ◽  
Surface Defects ◽  
Star Product ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Dimensional System ◽  
The Novel ◽  
One Dimensional ◽  
Dual Quantum

Abstract We find a one-dimensional protected subsector of $$ \mathcal{N} $$ N = 4 matter theories on a general class of three-dimensional manifolds. By means of equivariant localization we identify a dual quantum mechanics computing BPS correlators of the original model in three dimensions. Specifically, applying the Atiyah-Bott-Berline-Vergne formula to the original action demonstrates that this localizes on a one-dimensional action with support on the fixed-point submanifold of suitable isometries. We first show that our approach reproduces previous results obtained on S3. Then, we apply it to the novel case of S2× S1 and show that the theory localizes on two noninteracting quantum mechanics with disjoint support. We prove that the BPS operators of such models are naturally associated with a noncom- mutative star product, while their correlation functions are essentially topological. Finally, we couple the three-dimensional theory to general $$ \mathcal{N} $$ N = (2, 2) surface defects and extend the localization computation to capture the full partition function and BPS correlators of the mixed-dimensional system.

Reemitted positron spectroscopy of near-surface defects

1990 ◽  
Vol 42 (4) ◽  
pp. 1910-1916 ◽  
Author(s):  
T. McMullen ◽  
M. J. Stott
Keyword(s):  
Surface Defects ◽  
Near Surface ◽  
Positron Spectroscopy
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