Effect of plastic deformation of bulk material on frictional shear stress

2013 ◽  
Author(s):  
Tatsuhiro Suzuki ◽  
Zhigang Wang ◽  
Yasuharu Yoshikawa
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Bulk Material ◽  
Frictional Shear Stress

scholarly journals Modelling the nucleation and propagation of cracks at twin boundaries

2021 ◽  
Author(s):  
Nicolò Grilli ◽  
Alan C. F. Cocks ◽  
Edmund Tarleton
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Cohesive Zone Model ◽  
Bulk Material ◽  
Zone Model ◽  
Fracture Path ◽  
Twin Boundaries ◽  
Interface Elements ◽  
Local Term ◽  
Good Agreement

AbstractFracture arising from cracks nucleating and propagating along twin boundaries is commonly observed in metals that exhibit twinning as a plastic deformation mechanism. This phenomenon affects the failure of macroscopic mechanical components, but it is not fully understood. We present simulations in which a continuum model for discrete twins and a cohesive zone model are coupled to aid the understanding of fracture at twin boundaries. The interaction between different twin systems is modelled using a local term that depends on the continuum twin variables. Simulations reveal that the resolved shear stress necessary for an incident twin to propagate through a barrier twin can be up to eight times the resolved shear stress for twin nucleation. Interface elements are used at the interfaces between all bulk elements to simulate arbitrary intragranular cracks. An algorithm to detect twin interfaces is developed and their strength has been calibrated to give good agreement with the experimentally observed fracture path. The elasto-plastic deformation induced by discrete twins is modelled using the crystal plasticity finite element method and the stress induced by twin tips is captured. The tensile stress caused by the tip of an incident twin on a barrier twin is sufficient to nucleate a crack. A typical staircase fracture path, with cracks propagating along the twin interfaces, is reproduced only if the strength of the twin interfaces is decreased to about one-third of the strength of the bulk material. This model can be used to help understand fracture caused by the activation of multiple twin systems in different materials.

scholarly journals Design and Optimization of a Shearing Machine Using FEA

2017 ◽  
Vol 7 (2 (S)) ◽  
pp. 181
Author(s):  
Satish Bahaley ◽  
Rasika Khairkar
Keyword(s):  
Plastic Deformation ◽  
Stainless Steel ◽  
Shear Stress ◽  
Cad Model ◽  
Design And Optimization ◽  
Steel Sheets

Shearing is the process to cut sheets using pair of blades, by applying shear stress along the thickness of the sheet. Shearing happens by extreme plastic deformation followed by breaking which propagates deeper into the thickness. The upper blade is fixed to the ram assembly that moves vertically and lower knife is fixed in the stationary table. This project is rooted on the necessity of industry to develop a shearing machine for cutting 5mm thick stainless steel sheets. In this project we will design a CAD model of shearing machine and analyze using FEA technique.

scholarly journals Mechanical Resonance Dispersion Revisited

2014 ◽  
Vol 1 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Haskell V. Hart
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Chemical Analysis ◽  
Normal Modes ◽  
Theoretical Explanation ◽  
Mechanical Resonance ◽  
Complex Shear ◽  
High Degree ◽  
Shear Compliance ◽  
Strain Responses

Mechanical resonance dispersion is the inelastic response of a solid to a periodic shear stress. Instead of the elastic Young's Modulus, the phenomenon is described by both a real J', and an imaginary J'' component of complex shear compliance, corresponding to in phase and out of phase strain responses, respectively. The experimental results are plots of J' and J'' vs. frequency, which are typically in the audiofrequency range of 10 - 5600 Hz. Resonances are observed as maxima in J'' and inversions in J' at frequencies corresponding to modes of plastic deformation, which are much lower frequencies (audiofrequency range) than elastic normal modes. The theoretical explanation of Edwin R. Fitzgerald involves particle waves and momentum transfer and leads to a particle-in-a-box frequency formula for these inelastic modes. Unfortunately, most of his and other published raw data were never analyzed by this model. The purpose of this article is to apply this formula to previously uninterpreted resonance dispersion curves and to address some of the earlier criticism of Fitzgerald's work. Results of these calculations support the Fitzgerald Theory to a high degree, demonstrate the importance of impurities and chemical analysis, largely mollify previous criticisms, and suggest the possibility of a new particle wave mass spectroscopy at great distances.

scholarly journals The critical shear stress of mercury single crystals

1937 ◽  
Vol 163 (912) ◽  
pp. 34-53 ◽  
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Melting Point ◽  
Single Crystal ◽  
Single Crystals ◽  
Critical Shear Stress ◽  
Impurity Content ◽  
Thermal Agitation ◽  
Plastic Yield ◽  
Metal Single Crystals

The influence of very small quantities of impurity on the critical shear stress of metal single crystals has an important bearing on the mechanism of their plastic deformation. For investigations in this field, mercury is a very suitable metal: its impurity content can easily be reduced to an extremely low level (Hulett 1911) and it contains no dissolved gases (Hulett 1911). Also, as first pointed out by Andrade (1914), single crystal wires of this metal can be prepared without difficulty. The low melting point of mercury (-38∙8° C.) is far from being a disadvantage. The crystals can be maintained at -60° C., and at a temperature so near the melting point the thermal agitation may be expected to accentuate phenomena not observable at lower temperatures, if such agitation plays the important part in the mechanism of glide ascribed to it (Taylor 1934; Polanyi 1934; Orowan 1934). As a possible instance of this, the experiments to be described have revealed the existence of a preliminary “set” preceding the true plastic yield. Widely differing forms of slip band have also been observed, and are described elsewhere (Greenland 1937). It is hoped that these results will throw further light on the mechanism of glide.

Non-Destructive Evaluation of 304 Stainless Steels Using a Scanning Hall-Sensor Microscope: Visualization of Strain-Induced Austenite-Phase Breakdown

1999 ◽  
Vol 591 ◽  
Author(s):  
A. Oota ◽  
K. Miyake ◽  
D. Sugiyama ◽  
H. Aoki
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Stainless Steels ◽  
Driving Force ◽  
Room Temperature ◽  
Martensite Phase ◽  
Hall Sensor ◽  
Austenite Phase ◽  
Non Destructive Evaluation ◽  
Non Destructive

ABSTRACTUsing a scanning Hall-sensor microscope with an active area 50pμm × 50μm, we succeeded in visualizing a breakdown of paramagnetic austenite-phase in 304 stainless steels induced by a plastic strain at room temperature, resulting from a transformation to ferromagnetic martensite-phase. Magnetic images of spontaneous magnetic fields on a surface of strained sample show the degree and the place (and/or the extent) of phase breakdown. Furthermore, the images nearly agree with the calculated results for the principal shear stress rather than the principal stress under plastic deformation, indicative of the driving force of this breakdown. The study should open a way for non-destructive evaluation of 304 stainless steels.

Aperiodic Deformation Occurring as a Result of Thermoplastic Instability of Metals

2007 ◽  
Vol 537-538 ◽  
pp. 541-548 ◽  
Author(s):  
Zoltán Pálmai
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Shear Strain ◽  
Three Dimensional ◽  
Experimental Results ◽  
Reverse Effect ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Periodic Fluctuation ◽  
Linear Nature

The author developed a three-dimensional model for the description of fast plastic deformation of metals in the case of cutting. Shear strain occurring as a result of shear stress has a reverse effect on stress, while the temperature of the material is increasing. These counteracting effects may lead to thermomechanic instability, which may result in aperiodic chaotic conditions besides periodic fluctuation due to the non-linear nature of the process. Apart from bifurcation and multi-cycle periodic deformation, the model also describes aperiodic chaotic deformation, which is proven by experimental results.

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