scholarly journals Pop-In Phenomenon as a Fundamental Plasticity Probed by Nanoindentation Technique

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1879
Author(s):  
Takahito Ohmura ◽  
Masato Wakeda
Keyword(s):  
Mechanical Response ◽  
Computational Simulation ◽  
Indentation Load ◽  
Dislocation Nucleation ◽  
Future Perspective ◽  
Small Scale ◽  
Strain Burst ◽  
Major Mechanism ◽  
Nanoindentation Technique ◽  
Incipient Plasticity

The attractive strain burst phenomenon, so-called “pop-in”, during indentation-induced deformation at a very small scale is discussed as a fundamental deformation behavior in various materials. The nanoindentation technique can probe a mechanical response to a very low applied load, and the behavior can be mechanically and physically analyzed. The pop-in phenomenon can be understood as incipient plasticity under an indentation load, and dislocation nucleation at a small volume is a major mechanism for the event. Experimental and computational studies of the pop-in phenomenon are reviewed in terms of pioneering discovery, experimental clarification, physical modeling in the thermally activated process, crystal plasticity, effects of pre-existing lattice defects including dislocations, in-solution alloying elements, and grain boundaries, as well as atomistic modeling in computational simulation. The related non-dislocation behaviors are also discussed in a shear transformation zone in bulk metallic glass materials and phase transformation in semiconductors and metals. A future perspective from both engineering and scientific views is finally provided for further interpretation of the mechanical behaviors of materials.

scholarly journals Nonlinear magneto-thermo-elastic vibration of mass sensor armchair carbon nanotube resting on an elastic substrate

2020 ◽  
Vol 7 (1) ◽  
pp. 153-165
Author(s):  
Rajendran Selvamani ◽  
M. Mahaveer Sree Jayan ◽  
Rossana Dimitri ◽  
Francesco Tornabene ◽  
Farzad Ebrahimi
Keyword(s):  
Carbon Nanotube ◽  
Mechanical Response ◽  
Scale Effects ◽  
Nonlocal Elasticity Theory ◽  
Wave Dispersion ◽  
Elastic Vibration ◽  
Ultrasonic Waves ◽  
Small Scale ◽  
Dimensionless Frequency ◽  
Mass Sensors

AbstractThe present paper aims at studying the nonlinear ultrasonic waves in a magneto-thermo-elastic armchair single-walled (SW) carbon nanotube (CNT) with mass sensors resting on a polymer substrate. The analytical formulation accounts for small scale effects based on the Eringen’s nonlocal elasticity theory. The mathematical model and its differential equations are solved theoretically in terms of dimensionless frequencies while assuming a nonlinear Winkler-Pasternak-type foundation. The solution is obtained by means of ultrasonic wave dispersion relations. A parametric work is carried out to check for the effect of the nonlocal scaling parameter, together with the magneto-mechanical loadings, the foundation parameters, the attached mass, boundary conditions and geometries, on the dimensionless frequency of nanotubes. The sensitivity of the mechanical response of nanotubes investigated herein, could be of great interest for design purposes in nano-engineering systems and devices.

Double-Sided Microchannel Cooling of a Power Electronics Module Using Power Overlay

2009 ◽  
Author(s):  
Adam G. Pautsch ◽  
Arun Gowda ◽  
Ljubisa Stevanovic ◽  
Rich Beaupre
Keyword(s):  
Power Electronics ◽  
High Performance ◽  
Mechanical Response ◽  
Thermal Contact ◽  
Small Scale ◽  
Micro Channel ◽  
Performance Technology ◽  
Actual Performance ◽  
Low Performance ◽  
Microchannel Cooling

In the continuing effort to alleviate the increasing thermal loads for power electronics devices, numerous aggressive solutions have been developed, such as small-scale micro-channel heat exchangers. Although these methods can improve overall surface heat transfer to the order of 500 W cm−2, they are limited to single-sided cooling due to the typical wire-bonded electrical connections of the devices. Power overlay (POL) technology provides a stable planar structure for electrical connection, as well as attachment of an additional top-side heat exchanger. This study presents an analysis of double-sided microchannel cooling of a power electronics module. Two optimized, integral micro-channel heat sinks were attached above and below silicon power devices, with more traditional attachment on one side and a POL interface on the other. A compliant TIM was selected for low thermal resistance and good mechanical response, which allowed top-side connection to the POL surface. A theoretical model is presented that predicts the benefit of double-sided cooling based on the known performance of a single-sided heat sink and given addition thermal contact resistance for the top side. For microchannels with water, an enhancement of 26% was predicted. An experiment was also carried out to measure the actual performance benefit seen with double-sided cooling. An enhancement of over 30% was measured for a particular design. As the theory predicts, the benefit of double-sided cooling is limited for high performance designs. However, double-sided cooling could lead to high levels of thermal performance using low-performance technology.

Research on Mechanical Response of Copper Treated by Micro Laser Shock Peening Using Nanoindentation Technique

2011 ◽  
Vol 38 (6) ◽  
pp. 0603026 ◽  
Author(s):  
樊玉杰 Fan Yujie ◽  
周建忠 Zhou Jianzhong ◽  
黄舒 Huang Shu ◽  
范金荣 Fan Jinrong ◽  
王呈栋 Wang Chengdong ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Nanoindentation Technique ◽  
Shock Peening

Thin Film Fracture During Nanoindentation of Hard Film – Soft Substrate Systems

2001 ◽  
Vol 695 ◽  
Author(s):  
M. Pang ◽  
K.D. Weaver ◽  
D.F. Bahr
Keyword(s):  
Mechanical Response ◽  
Film Formation ◽  
Permanent Deformation ◽  
Dislocation Nucleation ◽  
Titanium Oxides ◽  
Soft Substrate ◽  
Aluminum Oxides ◽  
Anodic Titanium Oxide ◽  
Formation Conditions ◽  
Film Cracking

ABSTRACTNanoindentation testing of hard film – soft substrate systems can exhibit permanent deformation prior to a yield excursion, indicating that the occurrence of this sudden discontinuity is predominantly controlled by the hard film cracking rather than dislocation nucleation and multiplication. In a previous paper, a model was developed to predict the mechanical response prior to hard film fracture. In the current study a this model, which superimposes large deflection of the hard film and plastic deformation of the substrate the model, is further refined by testing a variety of materials with different film formation conditions. The tested materials include anodic titanium oxide on titanium, thermal aluminum oxide on aluminum and sputtered tungsten films on aluminum. The film fracture strength of titanium oxides on titanium is estimated as 15 GPa and that of aluminum oxides on aluminum is around 10 GPa. In the case of vacuum sputtered tungsten film on aluminum, the tungsten layer is likely plastically deformed. The strain at film fracture is roughly estimated to be 3.4%.

Mechanical Response and Incomplete Filling in Compression Molding With Microscale Double-Punch Sets

2019 ◽  
Author(s):  
Bin Zhang ◽  
M. Dodaran ◽  
S. Shao ◽  
W. J. Meng
Keyword(s):  
Mechanical Response ◽  
Ion Beam ◽  
Compression Molding ◽  
Molding Pressure ◽  
Small Scale ◽  
Width Ratio ◽  
Significant Dependence ◽  
Incomplete Filling ◽  
Surface Patterns ◽  
Scale Surface

Abstract Forming nano-/micro-scale surface patterns on metal surfaces by direct compression molding is an important means for achieving small scale surface features with potential usage in wide ranging technological applications. Geometric fidelity of molded features and the corresponding molding response are of critical importance in determining the usefulness of the molding replication technique. In this paper, two series of microscale punches made of tool steels were fabricated using Ga+ focused ion beam (FIB). In one series, the punch consists of a single protruding rectangular strip of different width, w (dubbed the “single punch”). In the other series, the punch consists of two rectangular strips of identical dimensions separated by a spacing in between, s (dubbed the “double punch”). These so-fabricated punches were used to mold elemental single crystal Al. The mechanical response during compression molding was measured and analyzed. For the double-punch experiments, measured characteristic molding pressure exhibited a significant dependence on the spacing to punch width ratio, λ = s/w, as well as a significant dependence on s when λ was fixed. The molded features were examined and the phenomenon of incomplete filling was observed to occur at λ < 0.5.

scholarly journals Investigation of thermo-mechanical response of a geothermal pile through a small-scale physical modelling

2020 ◽  
Vol 205 ◽  
pp. 05016
Author(s):  
Hussein Hashemi Senejani ◽  
Omid Ghasemi-Fare ◽  
Davood Yazdani Cherati ◽  
Fardin Jafarzadeh
Keyword(s):  
Mechanical Response ◽  
Thermal Response ◽  
Physical Modelling ◽  
Elastic Response ◽  
Small Scale ◽  
Thermal Cycles ◽  
Prolonged Heating ◽  
Excessive Heat ◽  
Head Displacement ◽  
Bed Changes

Energy piles have been used around the world to harvest geothermal energy to heat and cool residential and commercial buildings. In order to design energy geo-structures, thermo-mechanical response of the geothermal pile must be carefully understood. In this paper, a small scale physical model is designed and a series of heating thermal cycles with various vertical mechanical loads are performed. The instrumented pile is installed inside a dry sand bed. Changes in pile head displacement, shaft strains and pile and sand temperatures are monitored using an LVDT, strain gauges and thermocouples, respectively. Prolonged heating cycles, which would continue until boundary temperature changes, would allow the investigation of excessive heat injection when service loads are active on the pile. The thermal response is discussed including confirmation of a temperature influence zone around the pile, the increase in soil temperature, and minimum vertical heat dispersion in the soil. The mechanical response includes plastic settlements when the vertical load passes 20% of ultimate capacity. Plastic settlements have been observed at the half of the capacity reported for the shorter thermal cycles in similar models. The decrease in the capacity indicates a reduction in elastic response of the soil during longer thermal cycles.

Simulation Research of a Type of Pressure Vessel under Complex Loading Part 2 Complex Load of the Numerical Analysis

2013 ◽  
Vol 756-759 ◽  
pp. 4662-4667
Author(s):  
Jun Chen Li ◽  
Jie Sheng ◽  
Zhang Yu Fu
Keyword(s):  
Pressure Vessel ◽  
Large Scale ◽  
Mechanical Response ◽  
Simulation Analysis ◽  
Complex Loading ◽  
Operating Conditions ◽  
Small Scale ◽  
Simulation Research ◽  
Complex Load ◽  
Calculation Results

Loading of pressure vessel was usually complicated in practical service operating conditions. Simulation model of pressure vessel was built by method of finite element simulation analysis, and structured mesh generation was realized. Numerical calculation was come true, stress/strain distribution of pressure vessel was obtained in applying of the multi-load. On this basis, this condition compared with alone applied many loadings. The calculation results indicate the validity of this model, and results are evaluated according to relevant standards, which provide a way to study mechanical response in the actual working conditions. In addition, sub-model is analyzed for key part of pressure vessel, and transition is come true from large scale simulation to small scale simulation.

Modeling and Simulation of an Externally Fired Micro-Gas Turbine for Standalone Polygeneration Application

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Moksadur Rahman ◽  
Anders Malmquist
Keyword(s):  
Gas Turbine ◽  
Dynamic Model ◽  
Computational Simulation ◽  
Control Point ◽  
Membrane Distillation ◽  
Vital Role ◽  
Environmental Benefits ◽  
Small Scale ◽  
Micro Gas Turbine ◽  
Polygeneration System

Small-scale distributed generation systems are expected to play a vital role in future energy supplies. Subsequently, power generation using micro-gas turbine (MGT) is getting more and more attention. In particular, externally fired micro-gas turbine (EFMGT) is preferred among small-scale distributed generators, mainly due to high fuel flexibility, high overall efficiency, environmental benefits, and low maintenance requirement. The goal of this work is to evaluate the performance of an EFMGT-based standalone polygeneration system with the help of computational simulation studies. The main focus of this work is to develop a dynamic model for an EFMGT. The dynamic model is accomplished by merging a thermodynamic model with a mechanical model of the rotor and a transfer function based control system model. The developed model is suitable for analyzing system performance particularly from thermodynamic and control point of view. Simple models for other components of the polygeneration systems, electrical and thermal loads, membrane distillation unit, and electrical and thermal storage, are also developed and integrated with the EFMGT model. The modeling of the entire polygeneration system is implemented and simulated in matlab/simulink environment. Available operating data from test runs of both the laboratory setups are used in this work for further analysis and validation of the developed model.

Comparative Study of the Dynamic Response of Different Materials Subjected to Compressed Gas Blast Loading

2011 ◽  
Author(s):  
Brandon J. Hinz ◽  
Matthew V. Grimm ◽  
Karim H. Muci-Ku¨chler ◽  
Shawn M. Walsh
Keyword(s):  
Dynamic Response ◽  
High Speed ◽  
Mechanical Response ◽  
Blast Loading ◽  
Test Sample ◽  
Blast Waves ◽  
Small Scale ◽  
Acceleration Time Histories ◽  
Compressed Gas ◽  
Brain Tissue Damage

Understanding the dynamic response of materials under blast and impact loading is of interest for both military and civilian applications. In the case of blast loading, the mitigation characteristics of materials employed in personal protective equipment (PPE) is of particular importance. Without adequate protection, exposure of the head to blast waves may result in or contribute to brain tissue damage leading to traumatic brain injury (TBI). The development of simple but representative laboratory experiments that can be used to study the mechanical response of different materials and/or material combinations to blast loading could be very useful for the design of PPE such as helmets. This paper presents a basic experimental setup that can be conveniently used to perform such studies using small scale compressed gas blasts. An open end shock tube is employed to generate the blasts used to load flat plate samples placed in a special rigid holder. Acceleration time histories at selected locations in the sample are used to generate data to compare the dynamic response and blast mitigation effectiveness of different specimens. High speed schlieren video is used to correlate the arrival of the shock wave and air flow that follows with the motion of the test sample.

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