Dynamic Shear Stress—Analysis of Single Crystal Machining Studies

1973 ◽  
Vol 95 (4) ◽  
pp. 939-944 ◽  
Author(s):  
S. Ramalingam ◽  
J. Hazra
Keyword(s):  
Shear Stress ◽  
Single Crystal ◽  
Stress Analysis ◽  
Single Crystals ◽  
Plastic Flow ◽  
Metal Cutting ◽  
Dynamic Shear ◽  
Polycrystalline Aluminum ◽  
Cutting Problem ◽  
Good Agreement

Experimental results obtained when single crystals of aluminum of known orientation are machined under identical cutting conditions are presented. Analysis of the data obtained shows that the dynamic shear stress remains constant for all orientations tested and is in good agreement with the calculated value for polycrystalline aluminum. The implications of these results to metal cutting theory and the metal physical foundations on which the concept of dynamic shear stress, as a true material property, rests are discussed. The possible role that the dynamic shear stress may play in determining the geometry of the metal cutting problem, a problem in partially constrained plastic flow of metals, is discussed.

Some Controlled Metal-Cutting Studies With Resulfurized Steels

1961 ◽  
Vol 83 (4) ◽  
pp. 513-522 ◽  
Author(s):  
E. G. Thomsen ◽  
S. Kobayashi ◽  
M. C. Shaw
Keyword(s):  
Shear Stress ◽  
Plastic Flow ◽  
Contact Area ◽  
Metal Cutting ◽  
Flank Wear ◽  
Strength Properties ◽  
Dynamic Shear ◽  
Compression Tests ◽  
Low Sulfur ◽  
Cutting Speeds

Cutting tests, including controlled tool-chip contact area and controlled artificial flank wear-land studies, were made with five resulfurized steels having nearly identical strength properties. It was found that the dynamic shear stress was 62,700 psi and appeared to be identical for all steels at the two cutting speeds of 356 and 936 fpm with sulfur contents of the alloys ranging from 0.11 to 0.37 per cent. For the low sulfur steel (S = 0.033 per cent), the dynamic shear stress was found to be 72,000 psi. A comparison of the effective stresses obtained from compression tests with those from metal cutting tests showed good correlation at equal strains. The controlled tool-chip contact area and the controlled wear-land studies at feeds of approximately 0.005 ipr and cutting speeds of 318 to 356 fpm appear to indicate that sublayer plastic flow at the tool chip and tool work interfaces was essentially absent.

Measurement of growth rates for single crystals and pressed tablets of CuSO4.5 H2O on a rotating disc

1989 ◽  
Vol 54 (11) ◽  
pp. 2951-2961 ◽  
Author(s):  
Miloslav Karel ◽  
Jaroslav Nývlt
Keyword(s):  
Growth Rate ◽  
Single Crystal ◽  
Single Crystals ◽  
Growth Rates ◽  
Diffusion Coefficients ◽  
Preferred Orientation ◽  
Rotating Disc ◽  
Dissolution Rates ◽  
Rates Of Growth ◽  
Good Agreement

Measured growth and dissolution rates of single crystals and tablets were used to calculate the overall linear rates of growth and dissolution of CuSO4.5 H2O crystals. The growth rate for the tablet is by 20% higher than that calculated for the single crystal. It has been concluded that this difference is due to a preferred orientation of crystal faces on the tablet surface. Calculated diffusion coefficients and thicknesses of the diffusion and hydrodynamic layers in the vicinity of the growing or dissolving crystal are in good agreement with published values.

scholarly journals The Stress Induced Martensite-Austenite Interface in Fe-15Ni-15Cr Single Crystals

1973 ◽  
Vol 31 ◽  
pp. 110-111
Author(s):  
G. A. Stone ◽  
G. Thomas
Keyword(s):  
Shear Stress ◽  
Slip System ◽  
Single Crystal ◽  
Single Crystals ◽  
Habit Plane ◽  
Maximum Shear Stress ◽  
Crystal Axis ◽  
Surface Study

A single crystal stressed in the [3]𝛄 direction at 185°K was transformed to 5% 𝛂 martensite and 2% Ɛ martensite by volume. The austenite slip system of maximum shear stress is the (11)𝛄 [01)𝛄. Fig. 1 shows a two surface study using the electron and optical microscopes. The a martensite is confined between £martensite plates with the (0001)Ɛ ∥ (11)𝛄. The size of the acicular martensite crystals is controlled by the spacing of the £ martensite plates. These £ martensite plates are seen in Fig. 1A as dark vertical bands. The axes of the acicular crystals lie in the (11)𝛄 plane. The £ martensite habit plane is defined as the plane perpendicular to the (11)𝛄 containing the vector defining the crystal axis.

The Effect of Solid Solution Impurities on Dislocation Nucleation in a (001) Mo – 1.5 at.% Ir Single Crystal

2010 ◽  
Vol 662 ◽  
pp. 85-93
Author(s):  
Sergey Dub ◽  
Igor Zasimchuk ◽  
Leonid Matvienko
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Shear Stress ◽  
Elastic Modulus ◽  
Single Crystal ◽  
Single Crystals ◽  
Free Volume ◽  
Dislocation Nucleation ◽  
Initial Portion ◽  
G 12

Mechanical properties of (001) Mo and (001) Mo – 1.5 at.% Ir single crystals have been studied by nanoindentation. It has been found that the iridium addition to molybdenum leads to an increase in both hardness and elastic modulus. An abrupt elasto-plastic transition (pop-in) at a depth of about 20 - 40 nm caused by dislocation nucleation in previously dislocation-free volume has been observed in the initial portion of the loading curve. It has shown that the Ir addition essentially affects the dislocation nucleation. Mean shear stress required for the dislocation nucleation increased from 10.8 GPa (G/12) for a Mo single crystal to 18.2 GPa (G/8) for the Mo – 1.5 at% Ir solid solution. Thus, the Ir solution in a Mo single crystal affects not only the resistance to the motion of dislocations (hardness) but the nucleation of them as well. The latter is likely to occur as a result of an increase in the structure perfection of the Mo – 1.5 at% Ir solid solution as compared to the pure Mo single crystal.

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.

Accommodation of constrained deformation in f. c. c. metals by slip and twinning

1969 ◽  
Vol 309 (1499) ◽  
pp. 433-456 ◽  
Keyword(s):  
Shear Stress ◽  
Single Crystals ◽  
Plane Strain ◽  
Plane Strain Compression ◽  
Orientation Factor ◽  
Cubic Crystals ◽  
Constrained Deformation ◽  
Critical Resolved Shear Stress ◽  
Good Agreement ◽  
External Strain

The problem of accommodation of constrained deformation by slip and twinning has been analysed. The analysis is based on Taylor’s least work hypothesis. In this analysis, the operative combination of slip and twinning systems is found by minimizing the orientation factor M = (∑ i s i +α∑ i t i )/ ε , where s i and t i are the simple shears resulting from slip and twinning respectively, α is the ratio of the critical resolved shear stress for twinning against slip, and Ɛ is the external strain. Detailed calculations have been made for face-centred cubic crystals deformed by plane strain compression. Experimental observations on deformed single crystals of a Co–8% Fe alloy indicate good agreement with the analysis. Implications of the present study to the twinning observations of Heye & Wassermann on rolled Ag crystals are discussed.

scholarly journals Influence of the Non-Schmid Effects on the Ductility Limit of Polycrystalline Sheet Metals

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1386 ◽  
Author(s):  
Mohamed Ben Bettaieb ◽  
Farid Abed-Meraim
Keyword(s):  
Single Crystal ◽  
Mechanical Behavior ◽  
Single Crystals ◽  
Plastic Flow ◽  
Yield Criterion ◽  
Experimental Studies ◽  
Crystallographic Structure ◽  
Sheet Metals ◽  
Localized Necking ◽  
The Impact

The yield criterion in rate-independent single crystal plasticity is most often defined by the classical Schmid law. However, various experimental studies have shown that the plastic flow of several single crystals (especially with Body Centered Cubic crystallographic structure) often exhibits some non-Schmid effects. The main objective of the current contribution is to study the impact of these non-Schmid effects on the ductility limit of polycrystalline sheet metals. To this end, the Taylor multiscale scheme is used to determine the mechanical behavior of a volume element that is assumed to be representative of the sheet metal. The mechanical behavior of the single crystals is described by a finite strain rate-independent constitutive theory, where some non-Schmid effects are accounted for in the modeling of the plastic flow. The bifurcation theory is coupled with the Taylor multiscale scheme to predict the onset of localized necking in the polycrystalline aggregate. The impact of the considered non-Schmid effects on both the single crystal behavior and the polycrystal behavior is carefully analyzed. It is shown, in particular, that non-Schmid effects tend to precipitate the occurrence of localized necking in polycrystalline aggregates and they slightly influence the orientation of the localization band.

scholarly journals EXPERIMENTAL STUDY ON THE DYNAMIC SHEAR MODULUS AND DAMPING RATIO OF SATURATED SAND UNDER CYCLIC LOADING

2021 ◽  
Vol 55 (5) ◽  
Author(s):  
Jian Zhang ◽  
Jiuting Cao ◽  
Sijie Huang ◽  
Baocun Shi
Keyword(s):  
Shear Stress ◽  
Shear Modulus ◽  
Shear Strain ◽  
Vibration Frequency ◽  
Damping Ratio ◽  
Test System ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Saturated Sand ◽  
Good Agreement

Initial shear stress is inevitable in actual engineering slopes, subgrades and foundations, and soils exhibit different dynamic characteristics under the influence of initial shear stress. Using a dynamic triaxial test system, this study explores the dynamic shear modulus and damping ratio of saturated sand from Wenchuan, investigates the effects of the initial shear stress and vibration frequencies on the dynamic shear modulus and damping ratio of saturated sand and proposes a normalised dynamic shear modulus formula that considers the initial shear stress and vibration frequency. Results show a threshold dynamic shear strain of the saturated sand. When the dynamic shear strain is below this threshold, the dynamic shear modulus significantly increases with the initial shear stress and vibration frequency. Otherwise, the influence of the initial shear stress and vibration frequency gradually decreases and eventually stabilises. The initial shear stress significantly affects the normalised dynamic shear modulus/strain curves where a larger initial shear stress corresponds to a higher curve. Meanwhile, the vibration frequency only exerts a slight influence. The curves under different frequencies are generally within the same band and fall near the Seed upper envelope. The initial shear stress also has a significant influence on the damping ratio where a larger initial shear stress corresponds to a smaller damping ratio. On the basis of the experimental results, a normalised dynamic shear modulus/shear strain formula that considers the influence of the initial shear stress and vibration frequency is established. Fitting results indicate that this formula shows good agreement with the test data.

Controlled Contact Cutting Tools

1959 ◽  
Vol 81 (2) ◽  
pp. 139-147 ◽  
Author(s):  
B. T. Chao ◽  
K. J. Trigger
Keyword(s):  
Shear Stress ◽  
Surface Finish ◽  
High Speed ◽  
Metal Cutting ◽  
Cutting Tools ◽  
Substantial Reduction ◽  
Cutting Fluids ◽  
Dynamic Shear ◽  
Effective Utilization ◽  
High Speed Cutting

A substantial reduction in power consumption, an increase in tool life, more effective utilization of cutting fluids, and improved surface finish on the machined workpiece have been achieved by suitably controlling the length of tool-chip contact. Reasons for these findings are discussed in terms of basic variables in chip formation mechanics. Artificially restricted contact tools open new avenues for metal cutting research. Machining data obtained with such tools provide further evidence of the invariant behavior of the dynamic shear stress of metals under high-speed cutting conditions, and unfold interesting information on the intricate nature of tool-chip contact.

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