Plastic Strain Effect in Progressive Multi-Cycle Nano-Indentation Measurement

2015 ◽  
Vol 645-646 ◽  
pp. 675-680 ◽  
Author(s):  
Qi Long Wei ◽  
Xiao Yuan Li ◽  
Xiao Bin Yue ◽  
Da Jiang Lei
Keyword(s):  
Plastic Strain ◽  
Austenitic Steel ◽  
Steel Sample ◽  
Fused Silica ◽  
Strain Effect ◽  
High Plasticity ◽  
Silica Sample ◽  
Depth Direction ◽  
Indentation Process ◽  
Properties Of Materials

Properties of materials and their variations in depth direction in the same location could be measured directly by progressive multi-cycle (PMC) nanoindentation method. But influences of strain-hardening on measured results in this process haven’t been researched thoroughly. Measurements on an austenitic steel sample and a fused silica sample were conducted by PMC nanoindentation and standard nanoindentation methods, and differences of the results by two methods of the two materials were analyzed. It was found that hardness of austenitic steel measured by PMC method decreased monotonously with increased depth, while hardness measured by standard method decreased to stable value with increased depth. And properties of fused silica measured by both methods accorded much well. Based on analysis of plastic strain during indentation process, it was deduced that austenitic steel with high plasticity could introduce second convergence of plastic strain and stress in PMC indentation process, which made measured hardness decrease monotonously with increased depth.

Large plasticity in magnesium mediated by pyramidal dislocations

Science ◽  
2019 ◽  
Vol 365 (6448) ◽  
pp. 73-75 ◽  
Author(s):  
Bo-Yu Liu ◽  
Fei Liu ◽  
Nan Yang ◽  
Xiao-Bo Zhai ◽  
Lei Zhang ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Electron Microscope ◽  
Plastic Strain ◽  
Crystal Size ◽  
High Stress ◽  
High Strength ◽  
High Plasticity ◽  
Transmission Electron ◽  
Small Crystal Size

Lightweight magnesium alloys are attractive as structural materials for improving energy efficiency in applications such as weight reduction of transportation vehicles. One major obstacle for widespread applications is the limited ductility of magnesium, which has been attributed to 〈c+a〉 dislocations failing to accommodate plastic strain. We demonstrate, using in situ transmission electron microscope mechanical testing, that 〈c+a〉 dislocations of various characters can accommodate considerable plasticity through gliding on pyramidal planes. We found that submicrometer-size magnesium samples exhibit high plasticity that is far greater than for their bulk counterparts. Small crystal size usually brings high stress, which in turn activates more 〈c+a〉 dislocations in magnesium to accommodate plasticity, leading to both high strength and good plasticity.

scholarly journals Development of a novel nanoindentation technique by utilizing a dual-probe AFM system

2015 ◽  
Vol 6 ◽  
pp. 2015-2027 ◽  
Author(s):  
Eyup Cinar ◽  
Ferat Sahin ◽  
Dalia Yablon
Keyword(s):  
Scanning Probe Microscopy ◽  
Tuning Fork ◽  
Vertical Movement ◽  
Fused Silica ◽  
Scanning Probe ◽  
Depth Sensing ◽  
New Approach ◽  
Probe System ◽  
Properties Of Materials ◽  
Dual Probe

A novel instrumentation approach to nanoindentation is described that exhibits improved resolution and depth sensing. The approach is based on a multi-probe scanning probe microscopy (SPM) tool that utilizes tuning-fork based probes for both indentation and depth sensing. Unlike nanoindentation experiments performed with conventional AFM systems using beam-bounce technology, this technique incorporates a second probe system with an ultra-high resolution for depth sensing. The additional second probe measures only the vertical movement of the straight indenter attached to a tuning-fork probe with a high spring constant and it can also be used for AFM scanning to obtain an accurate profiling. Nanoindentation results are demonstrated on silicon, fused silica, and Corning Eagle Glass. The results show that this new approach is viable in terms of accurately characterizing mechanical properties of materials through nanoindentation with high accuracy, and it opens doors to many other exciting applications in the field of nanomechanical characterization.

Measuring Microscopic Properties of a Single-Crystalline Diamond by Nano-Indentation Technology

2015 ◽  
Vol 1120-1121 ◽  
pp. 378-382 ◽  
Author(s):  
Qi Long Wei ◽  
Xiao Bin Yue ◽  
Xiao Yuan Li ◽  
Bo Liu ◽  
Xiao Feng Zhang ◽  
...  
Keyword(s):  
Great Influence ◽  
Fused Silica ◽  
Diamond Surface ◽  
Measurement Properties ◽  
Indentation Hardness ◽  
Silica Sample ◽  
Single Crystalline ◽  
Nano Indentation ◽  
Indentation Force ◽  
Before And After

Nano-indentation technology was brought to study microscopic mechanical properties of a single-crystalline diamond (SCD). Nano-indentation measurement was conducted on the {100} plane of SCD, and influences of various factors on measured results were analyzed, from which methods were confirmed to improve veracity of measurement. Properties of the indenter were checked with a fused silica sample both before and after indentation on diamond, which provided guarantee to veracity of results on diamond. It was found that tilt of diamond surface had so great influence that it could damage the indenter, and make the indentation curves anomalous. While damage of indenter could be avoided and valid measurement results could be obtained when tilt of diamondsurface was decreased below 0.10º and the maximal indentation force was less than 10 mN. Deformation of the diamond was almost full-elastic during indentation process. Indentation hardness of {100} plane of the SCD was about 70 GPa with standard deviation less than 3 GPa. And there had good reproducibility between two groups of measurements.

scholarly journals Micro-Machining of Diamond, Sapphire and Fused Silica Glass Using a Pulsed Nano-Second Nd:YVO4 Laser

Optics ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 169-183
Author(s):  
David G. Waugh ◽  
Chris D. Walton
Keyword(s):  
Silica Glass ◽  
Surface Engineering ◽  
Laser System ◽  
Laser Wavelength ◽  
Fused Silica ◽  
Threshold Fluence ◽  
Diode Pumped ◽  
Properties Of Materials ◽  
Fused Silica Glass

Optically transparent materials are being found in an ever-increasing array of technological applications within industries, such as automotive and communications. These industries are beginning to realize the importance of implementing surface engineering techniques to enhance the surface properties of materials. On account of the importance of surface engineering, this paper details the use of a relatively inexpensive diode-pumped solid state (DPSS) Nd:YVO4 laser to modify the surfaces of fused silica glass, diamond, and sapphire on a micrometre scale. Using threshold fluence analysis, it was identified that, for this particular laser system, the threshold fluence for diamond and sapphire ranged between 10 Jcm−2 and 35 Jcm−2 for a laser wavelength of 355 nm, dependent on the cumulative effects arising from the number of incident pulses. Through optical microscopy and scanning electron microscopy, it was found that the quality of processing resulting from the Nd:YVO4 laser varied with each of the materials. For fused silica glass, considerable cracking and deformation occurred. For sapphire, good quality features were produced, albeit with the formation of debris, indicating the requirement for post-processing to remove the observed debris. The diamond material gave rise to the best quality results, with extremely well defined micrometre features and minimal debris formation, comparative to alternative techniques such as femtosecond laser surface engineering.

Modeling the Ratcheting Phenomenon in an Austenitic Steel at Room Temperature

2000 ◽  
Author(s):  
A. S. Zaki ◽  
H. Ghonem
Keyword(s):  
Plastic Strain ◽  
Constitutive Model ◽  
Austenitic Steel ◽  
Room Temperature ◽  
Polycrystalline Material ◽  
Kinematic Hardening ◽  
Experimental Results ◽  
Experimental Program ◽  
Model Parameters ◽  
Proposed Model

Abstract This paper describes the cyclic accumulative plastic strain in a polycrystalline material when subjected to loading conditions promoting ratcheting behavior. For this purpose, a unified viscoplastic constitutive model based on non-linear kinematic hardening formulation is implemented. Identification of the model parameters was carried out using an experimental program that included monotonic, cyclic and relaxation testing. Simulation of the material response using the proposed model is compared with experimental results for the same loading. This comparison is used to evaluate the model validity.

scholarly journals Lattice Strain Effect in Structural, Magnetoresistance and Electrical Properties of La0.67Sr0.33MnO3 Bulk and Thin Film System

2016 ◽  
Vol 846 ◽  
pp. 635-640
Author(s):  
Kean Pah Lim ◽  
Han Ming Albert Gan ◽  
Soo Kien Chen ◽  
Zainal Abdib Talib ◽  
S.A. Halim ◽  
...  
Keyword(s):  
Thin Films ◽  
Lattice Strain ◽  
Hexagonal Structure ◽  
Fused Silica ◽  
Strain Effect ◽  
Conventional Solid State Reaction ◽  
Corning Glass ◽  
Lower Temperature ◽  
Pellet Form ◽  
Induced Structure

Polycrystalline La0.67Sr0.33MnO3 (LSMO) powder prepared via conventional solid state reaction was pressed into pellet form. The pellets became target to growth thin films on corning glass (LSMO-C), fused silica (LSMO-FS) and MgO (100) (LSMO-M) substrate via pulsed laser deposition (PLD) method. XRD results showed that all samples were hexagonal structure with R-3C space group. Thin films showed relatively smaller crystallite size compared to bulk samples. From Rietveld Refinement analysis, all thin films experienced lattice strain when deposited on different substrate. LSMO compound deposited in different substrate induced structure distortion and lattice strain. Compression along c-axis occurred when the lattice strain increased thus shifted the metal-insulator transition temperature to lower temperature and increased its resistivity.

Measurement of relaxation of electrical charge distribution on fused silica sample

2007 ◽  
Vol 366 (1-2) ◽  
pp. 145-149 ◽  
Author(s):  
L.G. Prokhorov ◽  
P.E. Khramchenkov ◽  
V.P. Mitrofanov
Keyword(s):  
Charge Distribution ◽  
Fused Silica ◽  
Electrical Charge ◽  
Silica Sample

scholarly journals Optical freeform generation by laser machining and plasma-assisted polishing

2019 ◽  
Vol 215 ◽  
pp. 03003
Author(s):  
Thomas Arnold ◽  
Anne Maiwald ◽  
Georg Böhm ◽  
Martin Erhrhard ◽  
Klaus Zimmer
Keyword(s):  
Dwell Time ◽  
Plasma Jet ◽  
Fused Silica ◽  
Surface Shape ◽  
Laser Machining ◽  
Ablation Process ◽  
Silica Sample ◽  
Laser Ablation Process ◽  
Alternative Approach ◽  
Fs Laser

Tailored optical freeform lenses are required for different applications. Sub-aperture deterministic machining techniques such as plasma jet machining have shown great potential to generate freeform surfaces. However, depending on the required local slopes of the surface shape geometrical limitations occur due to the lateral tool function width. In the paper an alternative approach to fabricate freeform shapes exhibiting steep local slopes is presented. A first step involves a dwell time based fs-laser ablation process to generate the surface contour on a fused silica sample. Since the resulting roughness after laser machining lies in the range of 400 nm RMS which does not match optical requirements a subsequent plasma jet based polishing step is performed where micro-roughness is drastically reduced to values below 0.3 nm RMS.

Fracture Analysis of Ductile-Brittle Transition Temperature Region Considering Specimens With Different Constraints

2018 ◽  
Author(s):  
Kiminobu Hojo ◽  
Takatoshi Hirota ◽  
Naoki Ogawa ◽  
Kentaro Yoshimoto ◽  
Yasuto Nagoshi ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Plastic Strain ◽  
Flat Plate ◽  
Damage Mechanics ◽  
Tensile Load ◽  
Fracture Analysis ◽  
Strain Effect ◽  
Term Operation ◽  
Brittle Transition ◽  
Brittle Transition Temperature

Fracture toughness from a CT specimen is used as a material constant for fracture evaluation, but it has a large constraint, which provides too conservative evaluation results. In ductile to brittle transition temperature (DBTT) region ferritic steel which is material of RPV has a large scatter and it becomes important to know the accurate scatter of an irradiated material because of less margin of RPV’s integrity after a long term operation. In this paper to establish a more precise fracture evaluation method in DBTT region for an irradiated RPV with a postulated surface flaw, fracture analysis procedures considering constraint effect, the Beremin model and damage mechanics model and a coupled model of these models were applied to the specimens with different constraints, which were 1/2TCT specimens and flat plate specimens with a semicircular flaw under tensile load. For evaluation of pure cleavage fracture of flat plate specimens, a Beremin model with plastic strain effect was applied with incorporation of plastic strain effect. Further, for ductile fracture, the local strain criterion of ASME Section VIII was applied to the specimens with different geometries and its applicability was discussed.

Sign in / Sign up

Export Citation Format

Share Document