Mechanism of Chip Segmentation in Orthogonal Cutting of Zr-Based Bulk Metallic Glass

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Naresh Kumar Maroju ◽  
Xiaoliang Jin
Keyword(s):  
Shear Stress ◽  
Large Strain ◽  
Orthogonal Cutting ◽  
Amorphous Structure ◽  
Experimental Result ◽  
Thermomechanical Model ◽  
Stress Variation ◽  
Highly Sensitive ◽  
Shear Transformation ◽  
Shear Transformation Zones

Abstract Bulk metallic glasses (BMGs) are a series of metal alloys with an amorphous structure. The deformation of BMGs occurs in localized regions and is highly sensitive to the applied stress, strain rate, and temperature. This paper presents a coupled thermomechanical model to analyze the chip segmentation mechanism due to material shear localization in orthogonal cutting of Zr-BMG. The shear stress variation in the primary shear zone is modeled considering the tool-chip friction and large strain of the material. The constitutive property of BMG corresponding to the inhomogeneous deformation through shear transformation zones is modeled. The oscillations of shear stress, temperature, and free volume are simulated based on the cutting conditions. The predicted chip segmentation frequency is compared with the experimental result under different cutting speeds and uncut chip thicknesses. The developed model provides the fundamental mechanism of material deformation and chip formation in cutting Zr-BMG with an amorphous structure.

scholarly journals Effect of Hydrogen Charging on Pop-in Behavior of a Zr-Based Metallic Glass

Metals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 22 ◽  
Author(s):  
Lin Tian ◽  
Dominik Tönnies ◽  
Moritz Hirsbrunner ◽  
Tim Sievert ◽  
Zhiwei Shan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Metallic Glass ◽  
Spatial Correlation ◽  
Hydrogen Content ◽  
Amorphous Structure ◽  
Homogeneous Deformation ◽  
Hydrogen Charging ◽  
Shear Transformation ◽  
Shear Transformation Zones ◽  
Clear Increase

In this work, structural and mechanical properties of hydrogen-charged metallic glass are studied to evaluate the effect of hydrogen on early plasticity. Hydrogen is introduced into samples of a Zr-based (Vit 105) metallic glass using electrochemical charging. Nanoindentation tests reveal a clear increase in modulus and hardness as well as in the load of the first pop-in with increasing hydrogen content. At the same time, the probability of a pop-in occurring decreases, indicating that hydrogen hinders the onset of plastic instabilities while allowing local homogeneous deformation. The hydrogen-induced stiffening and hardening is rationalized by hydrogen stabilization of shear transformation zones (STZs) in the amorphous structure, while the improved ductility is attributed to the change in the spatial correlation of the STZs.

scholarly journals Numerical Study on Shear Stress Variation of RC Wall with L Shaped Section

2015 ◽  
Vol 59 (1) ◽  
pp. 15-25 ◽  
Author(s):  
Ali Ahmed Chaouch ◽  
Ramdane Boutemeur ◽  
Hakim Bechtoula ◽  
Abderrahim Bali
Keyword(s):  
Shear Stress ◽  
Numerical Study ◽  
Stress Variation ◽  
Shaped Section

A Novel Single-Photon Counting Technique Applied to Highly Sensitive Measurement of [Ca2+]i Transient in Human Aortic Smooth Muscle Cells

2006 ◽  
Vol 128 (5) ◽  
pp. 777-781
Author(s):  
Shigeru Tada ◽  
Ken Okazaki
Keyword(s):  
Shear Stress ◽  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Single Photon ◽  
Photon Counting ◽  
Muscle Cells ◽  
Single Photon Counting ◽  
Aortic Smooth Muscle Cells ◽  
Aortic Smooth Muscle ◽  
Highly Sensitive

This study demonstrates that aequorin, a luminescent natural dye, is useful for vascular cell intracellular Ca2+ concentration ([Ca2+]i) determination. A new single-photon counting technique was developed to resolve the effects of fluid flow shear stress on [Ca2+]i in human aortic smooth muscle cells (HASMCs). Confluent HASMCs were grown on petri dishes loaded with aequorin. Then the dishes were placed in a luminometer chamber after the physiological level of shear stress was applied to the HASMC surfaces. The chamber was housed inside a highly sensitive photomultiplier tube. It detected ultraweak photon emission in response to the [Ca2+]i transient. In the presence of 2.0mM extracellular Ca2+, a shear stress of 12dyn∕cm2, applied for 60s to the top surface of the HASMC monolayer, elicited a sharp increase in [Ca2+]i.

The Effect of Material Flow Stress on Analytical Simulation of Machining

2010 ◽  
Vol 29-32 ◽  
pp. 1809-1814
Author(s):  
Bing Lin Li ◽  
Ling Ling ◽  
Yu Jin Hu ◽  
Xue Lin Wang
Keyword(s):  
Flow Stress ◽  
Shear Zone ◽  
Analytical Model ◽  
Material Flow ◽  
Model Simulation ◽  
Orthogonal Cutting ◽  
Shear Plane ◽  
Thermomechanical Model ◽  
Workpiece Material ◽  
Flow Stress Data

The flow stress data of the workpiece are extremely crucial for the cutting simulation. The study shows how the input data affect the analytical predictions of cutting force and temperature. The Johnson-Cook material model is used to represent workpiece flow stress in the primary shear zone. A thermomechanical model of orthogonal cutting is proposed based on the main shear plane divides the primary shear zone into two unequal parts. Five different sets of workpiece material flow stress data used in the Johnson-Cook’s constitutive equation are chosen and make the sensitivity analysis for analytical model. Simulation results were compared to orthogonal cutting test data from the available literature, and find the effects of flow stress on analytical model was different from that for finite element model.

Characterization of Thermally Induced Stress in IC Packages Using PiFETs Over a Temperature Range of −180°C to 80°C

2014 ◽  
Vol 2014 (1) ◽  
pp. 000500-000504 ◽  
Author(s):  
Francy J. Akkara ◽  
Uday S. Goteti ◽  
Richard C. Jaeger ◽  
Michael C. Hamilton ◽  
Michael J. Palmer ◽  
...  
Keyword(s):  
Shear Stress ◽  
Stress Component ◽  
Shear Stress Component ◽  
Thermally Induced ◽  
Temperature Changes ◽  
Temperature Range ◽  
Induced Stress ◽  
Highly Sensitive ◽  
Stress Components

In certain applications, IC packages may be exposed to extreme temperatures and knowledge of thermally induced stress aids the prediction of performance degradation or failure of the IC. In the devices that are used in extreme conditions, the stress is caused mainly by the mismatch in expansion of various materials triggered by the different coefficients of thermal expansion. This work performed in this study is conducted using NMOS current mirror circuits that are cycled through a wide temperature range of −180°C to 80°C. These circuits are highly sensitive to stress and provide well-localized measurements of shear stress. The sensors are fabricated in such a way that the effects of certain stress components are isolated. These sensors are also temperature compensated so that only the effect of mechanical stress components is observed and changes in device performance due to temperature changes are minimal. Current readings obtained from the sensors are used to extract the shear stress component. Finite element simulations, using expected materials performance parameter information were also performed for similar packages and these results are compared to the measured results.

Stimulation of shear-transformation zones in metallic glasses by cryogenic thermal cycling

2020 ◽  
Vol 548 ◽  
pp. 120299 ◽  
Author(s):  
C.M. Meylan ◽  
F. Papparotto ◽  
S. Nachum ◽  
J. Orava ◽  
M. Miglierini ◽  
...  
Keyword(s):  
Thermal Cycling ◽  
Metallic Glasses ◽  
Shear Transformation ◽  
Shear Transformation Zones ◽  
Stimulation Of

Burring Process and Fracture Criterion of Large Diameter Steel Pipe

2020 ◽  
Vol 846 ◽  
pp. 139-145
Author(s):  
Shinichi Nishida ◽  
Daichi Uematsu ◽  
Naoki Ikeda ◽  
Kyohei Ogawa ◽  
Makoto Hagiwara ◽  
...  
Keyword(s):  
Shear Stress ◽  
Fracture Criterion ◽  
Maximum Shear Stress ◽  
Large Diameter ◽  
Branch Pipe ◽  
Fem Analysis ◽  
Equivalent Strain ◽  
Steel Pipe ◽  
Experimental Result ◽  
Forming Limit

This paper describes finite element method analysis (FEM analysis), results of burring processing of large diameter steel pipe and fracture criterion in burring process of large diameter steel pipe. In this study, the pipe is the 150A SGP pipe with a diameter of 165.2 mm and a wall thickness of 5 mm. The pipe is used for a plant as a flow channel of gas and liquid. A burring process of pipe is generally for forming the branch. The burring process is achieved by drawing of die from prepared hole. And the branch pipe is welded to the formed pipe. This process has some problem. One is the forming limit of pipe, and the other is needed to machining the end surface to be welded. Therefore, in this study, the forming limit of SGP pipe was estimated by FEM analysis of burring process. The parameters used for criteria for forming limit are the maximum shear stress and the equivalent strain. As a result of comparing the analysis result and the experimental result, the forming limit of the 150A SGP pipe was estimated that the maximum shear stress is 350 MPa and the equivalent strain is around 0.8.

The Strength of Thick-Walled Cylinders

1959 ◽  
Vol 81 (2) ◽  
pp. 95-111 ◽  
Author(s):  
B. Crossland ◽  
S. M. Jorgensen ◽  
J. A. Bones
Keyword(s):  
Shear Stress ◽  
Mild Steel ◽  
Close Agreement ◽  
Large Strain ◽  
Tension Test ◽  
Experimental Results ◽  
Maximum Pressure ◽  
Strain Behavior ◽  
Pressure Tests ◽  
Strain Data

Comprehensive pressure tests have been carried out on thick-walled, closed-ended cylinders made from a mild steel and a hardened and tempered steel, the maximum pressure reached being 94,000 lb/in.2 The complete theoretical behavior of the cylinders is computed from shear stress-strain data obtained from torsion tests and is shown to be in very close agreement with the experimental results. In addition, a method is given for deriving the large strain behavior of the cylinders from tension test data. When compared with the experimental results this approach gives larger errors, the theoretical values of pressure being consistently high. Finally, ultimate pressures have been calculated from two empirical expressions.

scholarly journals Shear-Transformation Zone Activation during Loading and Unloading in Nanoindentation of Metallic Glasses

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1477 ◽  
Author(s):  
Karina E. Avila ◽  
Stefan Küchemann ◽  
Iyad Alabd Alhafez ◽  
Herbert M. Urbassek
Keyword(s):  
Dynamics Simulation ◽  
Minor Effect ◽  
Rate Analysis ◽  
Loading And Unloading ◽  
Shear Transformation ◽  
Shear Transformation Zones ◽  
Experimental Findings ◽  
A Minor ◽  
Increasing Temperature ◽  
Activity Cluster

Using molecular dynamics simulation, we study nanoindentation in large samples of Cu–Zr glass at various temperatures between zero and the glass transition temperature. We find that besides the elastic modulus, the yielding point also strongly (by around 50%) decreases with increasing temperature; this behavior is in qualitative agreement with predictions of the cooperative shear model. Shear-transformation zones (STZs) show up in increasing sizes at low temperatures, leading to shear-band activity. Cluster analysis of the STZs exhibits a power-law behavior in the statistics of STZ sizes. We find strong plastic activity also during the unloading phase; it shows up both in the deactivation of previous plastic zones and the appearance of new zones, leading to the observation of pop-outs. The statistics of STZs occurring during unloading show that they operate in a similar nature as the STZs found during loading. For both cases, loading and unloading, we find the statistics of STZs to be related to directed percolation. Material hardness shows a weak strain-rate dependence, confirming previously reported experimental findings; the number of pop-ins is reduced at slower indentation rate. Analysis of the dependence of our simulation results on the quench rate applied during preparation of the glass shows only a minor effect on the properties of STZs.

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