Micro-Mechanical Testing of Metal Foam Cell Walls Using Miniature Three-Point Bending

2013 ◽  
Vol 586 ◽  
pp. 120-124 ◽  
Author(s):  
Tomáš Fíla ◽  
Daniel Kytýř ◽  
Petr Koudelka ◽  
Tomáš Doktor ◽  
Petr Zlámal ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cell Wall ◽  
Single Cell ◽  
Metal Foam ◽  
Metal Foams ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Three Point Bending ◽  
Micro Scale ◽  
Aluminium Metal

This paper is focused on determination of micro-mechanical material properties of aluminium metal foam at level of single cell wall. For the purpose of homogenization, complex and heterogenous inner structure of metal foams requires deep understanding of its deformation mechanisms and local mechanical properties. Therefore, a series of micro-scale bending tests of specimens prepared from foam's cells wall were performed. Initially, a technique of specimen preparation was developed. Dimensions and geometry of the specimens were inspected using scanning electron microscopy (SEM). Custom-designed three-point bending device suitable for testing at micro-scale was used for loading. Thin pure aluminium metal sheets were used for calibration of the described method. Six single cell wall specimens were tested. It can be concluded that the developed specimen preparation technique and loading method are suitable to determine local mechanical properties of thin walled metal foams.

Preparation and Characterization of Amorphous Al-Based Metal Foams

2015 ◽  
Vol 816 ◽  
pp. 682-687
Author(s):  
Cong Bo Li ◽  
Wei Wei Chen ◽  
Lu Wang
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Intermetallic Compounds ◽  
Dwell Time ◽  
Metal Foam ◽  
Metal Foams ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Xrd Patterns

Amorphous Al-Cu-Ti metal foams with the porosity of 65% were prepared by spark plasma sintering with both the diameter and height of 10 mm. The SPS process was carried out under the pressure, the dwell time and the temperatures of 300 MPa, 5min and 623-673K, respectively. The microstructure and mechanical behavior of the amorphous Al-Cu-Ti metal foams were investigated. The results showed that sintering at high temperatures improved the crystallinity and adhesion between particles. The intermetallic compounds, i.e. Al-Ti, Al-Cu and Al-Cu-Ti were identified from the XRD patterns. It was found that weak adhesion and irregular shape of NaCl might reduce the mechanical properties. The highest strength of amorphous Al-based metal foam sintered at 653K, 300MPa was 7.97MPa.

scholarly journals SEMI–AUTOMATED ASSESSMENT OF MICROMECHANICAL PROPERTIES OF THE METAL FOAMS ON THE CELL-WALL LEVEL

2016 ◽  
Vol 7 ◽  
pp. 72
Author(s):  
Nela Krčmářová ◽  
Jan Šleichrt ◽  
Tomáš Doktor ◽  
Daniel Kytýř ◽  
Ondřej Jiroušek
Keyword(s):  
Cell Wall ◽  
Vickers Hardness ◽  
Metal Foam ◽  
Filter Material ◽  
Deformation Energy ◽  
Metal Foams ◽  
Aluminium Foam ◽  
Plastic Properties ◽  
Wide Range ◽  
Two Samples

Metal foams are innovative porous material used for wide range of application such as deformation energy or sound absorption, filter material, or microbiological incubation carrier. To predict mechanical properties of the metal foam is necessary to precisely describe elasto–plastic properties of the foam on cell–wall level. Indentation with low load is suitable tool for this purpose. In this paper custom designed instrumented microindentation device was used for measurement of cell-wall characteristics of two different aluminium foams (ALPORAS and ALCORAS). To demonstrate the possibility of automated statistical estimation of measured characteristics the device had been enhanced by semi-automatic indent positioning and evaluation procedures based on user-defined grid. Vickers hardness was measured on two samples made from ALPORAS aluminium foam and one sample from ALCORAS aluminium foam. Average Vickers hardness of ALPORAS foam was 24.465HV1.019 and average Vickers hardness of ALCORAS was 36.585HV1.019.

scholarly journals Thickness-dependent stiffness of wood: potential mechanisms and implications

Holzforschung ◽  
2020 ◽  
Vol 74 (12) ◽  
pp. 1079-1087 ◽  
Author(s):  
Fei Guo ◽  
Clemens M. Altaner ◽  
Michael C. Jarvis
Keyword(s):  
Mechanical Properties ◽  
Cell Wall ◽  
Composite Materials ◽  
Tensile Stress ◽  
Single Cell ◽  
Single Cells ◽  
Axial Plane ◽  
Cellulose Microfibrils ◽  
Tensile Stiffness ◽  
Thin Samples

AbstractWhen wood is split or cut along the grain, a reduction in tensile stiffness has been observed. The averaged mechanical properties of wood samples, veneers or splinters therefore change when their thickness is less than about 1 mm. The loss of stiffness increases as the thickness approaches that of a single cell. The mechanism of the effect depends on whether the longitudinal fission plane is between or through the cells. Isolated single cells are a model for fission between cells. Each cell within bulk wood is prevented from twisting by attachment to its neighbours. Separation of adjacent cells lifts this restriction on twisting and facilitates elongation as the cellulose microfibrils reorientate towards the stretching direction. In contrast when the wood is cut or split along the centre of the cells, it appears that co-operative action by the S1, S2 and S3 cell-wall layers in resisting tensile stress may be disrupted. Since much of what is known about the nanoscale mechanism of wood deformation comes from experiments on thin samples, caution is needed in applying this knowledge to structural-sized timber. The loss of stiffness at longitudinal fracture faces may augment the remarkable capacity of wood to resist fracture by deflecting cracks into the axial plane. These observations also point to mechanisms for enhancing toughness that are unique to wood and have biomimetic potential for the design of composite materials.

scholarly journals Syntactic Iron Foams’ Properties Tailored by Means of Case Hardening via Carburizing or Carbonitriding

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4358
Author(s):  
Jörg Weise ◽  
Dirk Lehmhus ◽  
Jaqueline Sandfuchs ◽  
Matthias Steinbacher ◽  
Rainer Fechte-Heinen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Surface Hardening ◽  
Metal Foam ◽  
Mechanical Performance ◽  
Syntactic Foam ◽  
Metal Foams ◽  
Metal Injection Molding ◽  
Case Hardening ◽  
Two Phase ◽  
Gear Wheels

Metal foam inserts are known for their high potential for weight and vibration reduction in composite gear wheels. However, most metal foams do not meet the strength requirements mandatory for the transfer of sufficiently high levels of torque by the gears. Syntactic iron and steel foams offer higher strength levels than conventional two-phase metal foams, thus making them optimum candidates for such inserts. The present study investigates to what extent surface hardening treatments commonly applied to gear wheels can improve the mechanical properties of iron-based syntactic foams. Experiments performed thus focus on case hardening treatments based on carburizing and carbonitriding, with subsequent quenching and tempering to achieve surface hardening effects. Production of samples relied on the powder metallurgical metal injection molding (MIM) process. Syntactic iron foams containing 10 wt.% of S60HS hollow glass microspheres were compared to reference materials without such filler. Following heat treatments, the samples’ microstructure was evaluated metallographically; mechanical properties were determined via hardness measurements on reference samples and 4-point bending tests, on both reference and syntactic foam materials. The data obtained show that case hardening can indeed improve the mechanical performance of syntactic iron foams by inducing the formation of a hardened surface layer. Moreover, the investigation indicates that the respective thermo-chemical treatments can be applied to composite gear wheels in exactly the same way as to monolithic ones. In the surface region modified by the treatment, martensitic microstructures were observed, and as consequence, the bending limits of syntactic foam samples were increased by a factor of three.

Contrast from epitaxially sandwiched macromolecules

1978 ◽  
Vol 36 (2) ◽  
pp. 226-227
Author(s):  
M. Talianker ◽  
D.G. Brandon
Keyword(s):  
Gold Film ◽  
Lattice Defect ◽  
Gold Foil ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Resolution Limit ◽  
Transmission Electron ◽  
Crystal Lattice Defect ◽  
Void Effect ◽  
Lattice Resolution

A new specimen preparation technique for visualizing macromolecules by conventional transmission electron microscopy has been developed. In this technique the biopolymer-molecule is embedded in a thin monocrystalline gold foil. Such embedding can be performed in the following way: the biopolymer is deposited on an epitaxially-grown thin single-crystal gold film. The molecule is then occluded by further epitaxial growth. In such an epitaxial sandwich an occluded molecule is expected to behave as a crystal-lattice defect and give rise to contrast in the electron microscope.The resolution of the method should be limited only by the precision with which the epitaxially grown gold reflects the details of the molecular structure and, in favorable cases, can approach the lattice resolution limit.In order to estimate the strength of the contrast due to the void-effect arising from occlusion of the DNA-molecule in a gold crystal some calculations were performed.

The ionic strength dependence of chromatin folding

1978 ◽  
Vol 36 (2) ◽  
pp. 220-221
Author(s):  
F. Thoma ◽  
TH. Koller
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Ionic Strength ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Carbon Supports ◽  
Ionic Strength Dependence ◽  
Chromatin Folding ◽  
Strength Dependence ◽  
Preparation Techniques

Under a variety of electron microscope specimen preparation techniques different forms of chromatin appearance can be distinguished: beads-on-a-string, a 100 Å nucleofilament, a 250 Å fiber and a compact 300 to 500 Å fiber.Using a standardized specimen preparation technique we wanted to find out whether there is any relation between these different forms of chromatin or not. We show that with increasing ionic strength a chromatin fiber consisting of a row of nucleo- somes progressively folds up into a solenoid-like structure with a diameter of about 300 Å.For the preparation of chromatin for electron microscopy the avoidance of stretching artifacts during adsorption to the carbon supports is of utmost importance. The samples are fixed with 0.1% glutaraldehyde at 4°C for at least 12 hrs. The material was usually examined between 24 and 48 hrs after the onset of fixation.

SEM evaluation of the TEM cold-stage double-film specimen

1984 ◽  
Vol 42 ◽  
pp. 272-273
Author(s):  
Jayesh Bellare
Keyword(s):  
Spatial Distribution ◽  
Sample Preparation ◽  
Sample Thickness ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Liquid Sample ◽  
Thin Specimen ◽  
Sample Preparation Technique ◽  
Cold Stage ◽  
Film Specimen

Seeing is believing, but only after the sample preparation technique has received a systematic study and a full record is made of the treatment the sample gets.For microstructured liquids and suspensions, fast-freeze thermal fixation and cold-stage microscopy is perhaps the least artifact-laden technique. In the double-film specimen preparation technique, a layer of liquid sample is trapped between 100- and 400-mesh polymer (polyimide, PI) coated grids. Blotting against filter paper drains excess liquid and provides a thin specimen, which is fast-frozen by plunging into liquid nitrogen. This frozen sandwich (Fig. 1) is mounted in a cooling holder and viewed in TEM.Though extremely promising for visualization of liquid microstructures, this double-film technique suffers from a) ireproducibility and nonuniformity of sample thickness, b) low yield of imageable grid squares and c) nonuniform spatial distribution of particulates, which results in fewer being imaged.

Ultramicrotomy as a Technique for Materials Specimen Preparation

1990 ◽  
Vol 48 (2) ◽  
pp. 428-429
Author(s):  
S.R. Glanvill
Keyword(s):  
Materials Science ◽  
Structural Information ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Cross Sectional ◽  
Surfaces And Interfaces ◽  
Beam Analysis ◽  
Flat Embedding ◽  
20 Nm ◽  
Sectional Analysis

This paper summarizes the application of ultramicrotomy as a specimen preparation technique for some of the Materials Science applications encountered over the past two years. Specimens 20 nm thick by hundreds of μm lateral dimension are readily prepared for electron beam analysis. Materials examined include metals, plastics, ceramics, superconductors, glassy carbons and semiconductors. We have obtain chemical and structural information from these materials using HRTEM, CBED, EDX and EELS analysis. This technique has enabled cross-sectional analysis of surfaces and interfaces of engineering materials and solid state electronic devices, as well as interdiffusion studies across adjacent layers.Samples are embedded in flat embedding moulds with Epon 812 epoxy resin / Methyl Nadic Anhydride mixture, using DY064 accelerator to promote the reaction. The embedded material is vacuum processed to remove trapped air bubbles, thereby improving the strength and sectioning qualities of the cured block. The resin mixture is cured at 60 °C for a period of 80 hr and left to equilibrate at room temperature.

Applications of ultramicrotomy for materials characterization

1993 ◽  
Vol 51 ◽  
pp. 232-233
Author(s):  
R.T. Blackham ◽  
J.J. Haugh ◽  
C.W. Hughes ◽  
M.G. Burke
Keyword(s):  
Materials Science ◽  
Microstructural Analysis ◽  
Analytical Electron Microscopy ◽  
Austenitic Stainless Steels ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Thermally Induced ◽  
Radiation Induced ◽  
Characterization Of Materials

Essential to the characterization of materials using analytical electron microscopy (AEM) techniques is the specimen itself. Without suitable samples, detailed microstructural analysis is not possible. Ultramicrotomy, or diamond knife sectioning, is a well-known mechanical specimen preparation technique which has been gaining attention in the materials science area. Malis and co-workers and Glanvill have demonstrated the usefulness and applicability of this technique to the study of a wide variety of materials including Al alloys, composites, and semiconductors. Ultramicrotomed specimens have uniform thickness with relatively large electron-transparent areas which are suitable for AEM anaysis.Interface Analysis in Type 316 Austenitic Stainless Steel: STEM-EDS microanalysis of grain boundaries in austenitic stainless steels provides important information concerning the development of Cr-depleted zones which accompany M23C6 precipitation, and documentation of radiation induced segregation (RIS). Conventional methods of TEM sample preparation are suitable for the evaluation of thermally induced segregation, but neutron irradiated samples present a variety of problems in both the preparation and in the AEM analysis, in addition to the handling hazard.

A COMBINED TEM/FIM EXAMINATION OF FIELD EMISSION AS A FIM SPECIMEN PREPARATION TECHNIQUE

1986 ◽  
Vol 47 (C7) ◽  
pp. C7-459-C7-462 ◽  
Author(s):  
M. G. BURKE ◽  
D. D. SIELOFF ◽  
S. S. BRENNER
Keyword(s):  
Field Emission ◽  
Specimen Preparation ◽  
Preparation Technique
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