scholarly journals Mechanisms of Time-dependent Plastic Deformation of Eutectoid and Hypereutectoid Steels at Low T/TmTemperatures

2016 ◽  
Vol 25 (6) ◽  
pp. 359-365
Author(s):  
B.H. Choi ◽  
K.C. Chung ◽  
K.T. Park
Keyword(s):  
Plastic Deformation ◽  
Time Dependent ◽  
Hypereutectoid Steels

scholarly journals A Numerical Modelling Approach for Time-Dependent Deformation of Hot Forming Tools under the Creep-Fatigue Regime

2016 ◽  
Vol 2016 ◽  
pp. 1-13
Author(s):  
B. Reggiani ◽  
L. Donati ◽  
L. Tomesani
Keyword(s):  
Plastic Deformation ◽  
Die Design ◽  
Time Dependent ◽  
Hot Forming ◽  
Small Scale ◽  
Regression Equations ◽  
Premature Failure ◽  
Extrusion Die ◽  
Temperature State ◽  
Creep Fatigue

The present study was aimed at predicting the time-dependent deformation of tools used in hot forming applications subjected to the creep-fatigue regime. An excessive accumulated plastic deformation is configured as one of the three main causes of premature failure of tools in these critical applications and it is accumulated cycle by cycle without evident marks leading to noncompliant products. With the aim of predicting this accumulated deformation, a novel procedure was developed, presented, and applied to the extrusion process as an example. A time-hardening primary creep law was used and novel regression equations for the law’s coefficients were developed to account not only for the induced stress-temperature state but also for the dwell-time value, which is determined by the selected set of process parameters and die design. The procedure was validated against experimental data both on a small-scale extrusion die at different stress, temperature, load states, and for different geometries and on an industrial extrusion die which was discarded due to the excessive plastic deformation after 64 cycles. A numerical-experimental good agreement was achieved.

Study of the Size Dependence of Time-dependent Plastic Deformation of Gold Micro-pillars and Micro-spheres

2013 ◽  
Vol 1580 ◽  
Author(s):  
AZM Ariful Islam ◽  
Robert J. Klassen
Keyword(s):  
Plastic Deformation ◽  
Constant Load ◽  
Time Dependent ◽  
Dislocation Slip ◽  
Compression Tests ◽  
Creep Tests ◽  
Jump Frequency ◽  
Single Plane ◽  
Pillar Diameter ◽  
Micro Pillars

ABSTRACTIn this study the length scale dependence of the operative mechanisms of time-dependent plastic deformation was studied using room temperature compression tests performed on Au micro-pillars and micro-spheres of 1.0 to 5.0 µm diameter. All the samples tested displayed deformation that had a component of random strain jumps. In the case of the Au micro-pillars, the frequency of the strain jumps showed a bilinear dependence upon pillar diameter with the frequency being larger, and more sensitive to diameter, when the pillar diameter was small (and τR was high). We suggest that this indicates a transition from deformation occurring by deformation on multiple slip planes to deformation occurring predominantly by single-plane dislocation slip when the pillar diameter is less than 2 µm.The strain jump frequency during the constant-load micro-pillar creep tests showed a linear dependence upon τR. Creep tests performed on the micro-spheres of 5.0 µm diameter displayed displacement jump frequency that was essentially independent of the applied load while the jump frequency increased with increasing load for the smaller 2.5 µm diameter micro-spheres. We suggest that this difference is related to the volume of the micro-sphere. When the volume is small, the component of the deformation that occurs by a stochastic dislocation glide process is increased and becomes strongly dependent upon the magnitude of the local shear stress.

Microindentation of titanium: Dependence of plastic energy on the indentation depth and time-dependent plastic deformation

2008 ◽  
Vol 23 (4) ◽  
pp. 1068-1075 ◽  
Author(s):  
Rong Chen ◽  
Fuqian Yang ◽  
M. Ashraf Imam ◽  
C.R. Feng ◽  
Peter Pao
Keyword(s):  
Plastic Deformation ◽  
Indentation Depth ◽  
Pure Titanium ◽  
Indentation Load ◽  
Time Dependent ◽  
Indentation Hardness ◽  
Commercially Pure Titanium ◽  
Plastic Energy ◽  
Commercially Pure ◽  
Energy Dissipated

The cavity model and the dislocation mechanics were used to analyze the plastic energy dissipated in an indentation deformation. The plastic energy dissipated in an indentation cycle was proportional to the cube of the residual indentation depth. The experimental results supported the analysis for the indentation of commercially pure titanium by a Vickers indenter. Slip bands around the indentation were observed, suggesting that the indentation deformation was controlled by dislocation motion. The indentation hardness decreased with the indentation load, showing the indentation size effect. The ratio of the total energy to the plastic energy was found to be proportional to the ratio of the maximum indentation depth to the residual indentation depth. The effects of holding time were examined on the time-dependent plastic deformation of the commercially pure titanium at ambient temperature.

TRIBOLOGICAL PROPERTIES OF HIGH CARBON STEELS IN AN AS-CAST STATE AND AFTER PLASTIC DEFORMATION

Tribologia ◽  
2017 ◽  
Vol 276 (6) ◽  
pp. 19-26
Author(s):  
Łukasz FROCISZ ◽  
Janusz KRAWCZYK ◽  
Marcin MADEJ
Keyword(s):  
Plastic Deformation ◽  
Carbon Steels ◽  
Track Length ◽  
Cast State ◽  
Secondary Carbides ◽  
Heat Treated ◽  
The Matrix ◽  
Disk Friction ◽  
Hypereutectoid Steels ◽  
Friction Method

The aim of the study was to conduct dry sliding tests on the designed hypereutectoid steels with the controlled contents increase of carbon, chromium, and manganese. Chromium and manganese were used to balance the changes related to the higher secondary carbides’ precipitation in the chemical composition of the matrix. Samples were investigated by the use of the block on disk friction method under the load of 100 N. The duration of each test was 2000 s with the wear track length approx. 500 m. The samples were investigated in the as-cast state and after hot plastic deformation. Two sets of four samples were prepared from the ingots and plastically deformed material. The heat treated (quenched and tempered) 100Cr6 steel was used as the counter-sample, with a new counter-sample used for each test. The obtained results show a decrease of the average friction coefficient for samples after plastic deformation. The phenomena that influenced this effect the most, observed in the alloy with the higher concentration of alloying elements, were grain boundary net defragmentation of secondary carbides and the elimination of Widmannstaten needles. The main wear mechanisms occurring during the tribological tests were sliding wear and material spalling.

Time-dependent deformation behavior of interfacial intermetallic compound layers in electronic solder joints

2010 ◽  
Vol 25 (4) ◽  
pp. 629-632 ◽  
Author(s):  
Jenn-Ming Song ◽  
Chien-Wei Su ◽  
Yi-Shao Lai ◽  
Ying-Ta Chiu
Keyword(s):  
Crystal Structure ◽  
Plastic Deformation ◽  
Deformation Behavior ◽  
Solder Joints ◽  
Time Dependent ◽  
Creep Stress ◽  
Interfacial Intermetallic Compound ◽  
Creep Stress Exponent ◽  
Work Hardening Exponent ◽  
Good Agreement

Using nanoindentation, this study develops the criteria to evaluate the creep performance of the intermetallic compounds (IMCs) formed at the interface of microelectronic solder joints. Regardless of crystal structure and melting point, the creep stress exponent (X), one of the parameters determining creep resistance, is in good agreement with tendencies of the work-hardening exponent (n) and also the ratio of yield stress (Y) to Young's modulus (E), which reveals the ability against plastic deformation.

scholarly journals Revealing the Plastic Mode of Time-Dependent Deformation of a LiTaO3 Single Crystal by Nanoindentation

Micromachines ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 878
Author(s):  
Shengyun Zhou ◽  
Xianwei Huang ◽  
Congda Lu ◽  
Yunfeng Liu ◽  
Taihua Zhang ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Single Crystal ◽  
Room Temperature ◽  
Time Dependent ◽  
High Shear ◽  
Compression Stress ◽  
Creep Flow ◽  
Secondary Cracks ◽  
Loading Sequence ◽  
Surface Morphologies

Recently, instrumental nanoindentation has been widely applied to detect time-dependent plastic deformation or creep behavior in numerous materials, particularly thin films and heterogeneous materials. However, deformation mechanism at nanoindentation holding stage has not been well revealed hitherto. In the current work, nanoindentation holding tests with high loads were performed on a brittle LiTaO3 single crystal. The surface morphologies of residual impressions with various holding times were investigated. It was indicated that generation of secondary cracks and propagation of both main and secondary cracks were the dominating mechanism for time-dependent plastic deformation at the initial holding stage, and the density and length of cracks were invariable at the steady-state holding stage, which suggested a nonlocalized plastic deformation beneath the indenter. It could be concluded that time-dependent plastic deformation of brittle ceramic under nanoindentation is composed of instant cracking as the continuation of loading sequence and homogeneous creep flow by high shear-compression stress at room temperature.

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