scholarly journals Mechanical Deconvolution of Elastic Moduli by Indentation of Mechanically Heterogeneous Materials

2021 ◽  
Vol 9 ◽  
Author(s):  
J. N. M. Boots ◽  
R. Kooi ◽  
T. E. Kodger ◽  
J. van der Gucht
Keyword(s):  
Mechanical Properties ◽  
Accurate Determination ◽  
Finite Size ◽  
Heterogeneous Materials ◽  
Heterogeneous Material ◽  
Length Scale ◽  
Mechanical Heterogeneity ◽  
Force Microscopy ◽  
Probe Size ◽  
Stress Signal

Most materials are mechanically heterogeneous on a certain length scale. In many applications, this heterogeneity is crucial for the material’s function, and exploiting mechanical heterogeneity could lead to new materials with interesting features, which require accurate understanding of the local mechanical properties. Generally used techniques to probe local mechanics in mechanically heterogeneous materials include indentation and atomic force microscopy. However, these techniques probe stresses at a region of finite size, so that experiments on a mechanically heterogeneous material lead to blurring or convolution of the measured stress signal. In this study, finite element method simulations are performed to find the length scale over which this mechanical blurring occurs. This length is shown to be a function of the probe size and indentation depth, and independent of the elastic modulus variations in the heterogeneous material, for both 1D and 2D modulus profiles. Making use of these findings, we then propose two deconvolution methods to approximate the actual modulus profile from the apparent, blurred measurements, paving the way for an accurate determination of the local mechanical properties of heterogeneous materials.

scholarly journals A Study on Strengthening Mechanical Properties of a Punch Mold for Cutting by Using an HWS Powder Material and a DED Semi-AM Method of Metal 3D Printing

2020 ◽  
Vol 4 (4) ◽  
pp. 98 ◽  
Author(s):  
Seong-Woong Choi ◽  
Yong-Seok Kim ◽  
Young-Jin Yum ◽  
Soon-Yong Yang
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
Powder Material ◽  
Hot Stamping ◽  
Heterogeneous Materials ◽  
Heterogeneous Material ◽  
High Strength ◽  
High Wear Resistance ◽  
Metal 3D Printing ◽  
Directed Energy

The post-processing (punching or trimming) of high-strength parts reinforced by hot stamping requires punch molds with improved mechanical properties in hardness, resistance to wear, and toughness. In this study, a semi-additive manufacturing (semi-AM) method of heterogeneous materials was proposed to strengthen these properties using high wear resistance steel (HWS) powder and directed energy deposition (DED) technology. To verify these mechanical properties as a material for the punch mold for cutting, specimens were prepared and tested by a semi-AM method of heterogeneous material. The test results of the HWS additive material by the semi-AM method proposed in this study are as follows: the hardness was 60.59–62.0 HRc, which was like the Bulk D2 specimen. The wear resistance was about 4.2 times compared to that of the D2 specimen; the toughness was about 4.0 times that of the bulk D2 specimen; the compressive strength was about 1.45 times that of the bulk D2 specimen; the true density showed 100% with no porosity. Moreover, the absorption energy was 59.0 J in a multi-semi-AM specimen of heterogeneous materials having an intermediate buffer layer (P21 powder material). The semi-AM method of heterogeneous materials presented in this study could be applied as a method to strengthen the punch mold for cutting. In addition, the multi-semi-AM method of heterogeneous materials will be able to control the mechanical properties of the additive material.

Accurate determination of the mechanical properties of thin aluminum films deposited on sapphire flats using nanoindentations

1999 ◽  
Vol 14 (6) ◽  
pp. 2314-2327 ◽  
Author(s):  
Y. Y. Lim ◽  
M. M. Chaudhri ◽  
Y. Enomoto
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Accurate Determination ◽  
Direct Methods ◽  
Polycrystalline Aluminum ◽  
Aluminum Films ◽  
Force Microscopy ◽  
Contact Areas ◽  
Atomic Force

Nanoindentations using a Berkovich diamond indenter have been made on 1, 2, and 5 μm thick 99.99% purity polycrystalline aluminum films thermally evaporated in vacuum on to 2 mm thick R-cut polished sapphire flats. The projected contact areas of the residual indentations were estimated from the unloading load-displacement curves, and some of the indentations were imaged with an atomic force microscope (AFM). It was found that a large majority of indents showed material pileup, and the projected areas of these indents, as measured with the AFM, were up to 50% greater than those calculated from the unloading curves. This discrepancy between the calculated and directly measured indentation areas has a strong influence on the derived values of Young's modulus and hardness of the aluminum films. Using a new analytical model, Young's modulus of the aluminum films has been determined to be in the range of 50–70 GPa, independent of the relative indentation depth. The composite nanohardness of the 1 and 2 μm thick films was found to have a load-independent value of 1 GPa, whereas the composite nanohardness of the 5 μm film decreased from 1 to 0.7 Gpa with increasing indenter penetration. Finally, it has been suggested that in order to improve the accuracy with which the mechanical properties of thin films or bulk specimens can be determined by nanoindentation techniques, the projected contact areas should be measured by direct methods, such as atomic force microscopy.

Mechanical Properties of Membrane Surface of Cultured Astrocyte Revealed by Atomic Force Microscopy

2000 ◽  
Vol 39 (Part 1, No. 6B) ◽  
pp. 3711-3716 ◽  
Author(s):  
Hatsuki Shiga ◽  
Yukako Yamane ◽  
Etsuro Ito ◽  
Kazuhiro Abe ◽  
Kazushige Kawabata ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Atomic Force Microscopy ◽  
Membrane Surface ◽  
Force Microscopy ◽  
Atomic Force

scholarly journals Microstructure and Mechanical Properties of Al-Mg-Si Similar Alloy Laminates Produced by Accumulative Roll Bonding

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4200
Author(s):  
Zhigang Li ◽  
Hao Jiang ◽  
Minghui Wang ◽  
Hongjie Jia ◽  
Hongjiang Han ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Accumulative Roll Bonding ◽  
Thin Sheet ◽  
Heterogeneous Materials ◽  
Thick Sheet ◽  
Subsequent Aging ◽  
Roll Bonding ◽  
Roll Casting ◽  
Promotive Effect ◽  
Similar Materials

As the applications of heterogeneous materials expand, aluminum laminates of similar materials have attracted much attention due to their greater bonding strength and easier recycling. In this work, an alloy design strategy was developed based on accumulative roll bonding (ARB) to produce laminates from similar materials. Twin roll casting (TRC) sheets of the same composition but different cooling rates were used as the starting materials, and they were roll bonded up to three cycles at varying temperatures. EBSD showed that the two TRC sheets deformed in distinct ways during ARB processes at 300°C. Major recrystallizations were significant after the first cycle on the thin sheet and after the third cycle on the thick sheet. The sheets were subject to subsequent aging for better mechanical properties. TEM observations showed that the size and distribution of nano-precipitations were different between the two sheet sides. These nano-precipitations were found to significantly promote precipitation strengthening, and such a promotive effect was referred to as hetero-deformation induced (HDI) strengthening. Our work provides a new promising method to prepare laminated heterogeneous materials with similar alloy TRC sheets.

scholarly journals Corrosion Behavior and Mechanical Properties of a Nanocomposite Superhydrophobic Coating

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 652
Author(s):  
Divine Sebastian ◽  
Chun-Wei Yao ◽  
Lutfun Nipa ◽  
Ian Lian ◽  
Gary Twu
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Scanning Electron Microscopy ◽  
Atomic Force Microscopy ◽  
Nanocomposite Coating ◽  
Superhydrophobic Coating ◽  
Force Microscopy ◽  
Atomic Force ◽  
Microscopy Images ◽  
Scanning Electron

In this work, a mechanically durable anticorrosion superhydrophobic coating is developed using a nanocomposite coating solution composed of silica nanoparticles and epoxy resin. The nanocomposite coating developed was tested for its superhydrophobic behavior using goniometry; surface morphology using scanning electron microscopy and atomic force microscopy; elemental composition using energy dispersive X-ray spectroscopy; corrosion resistance using atomic force microscopy; and potentiodynamic polarization measurements. The nanocomposite coating possesses hierarchical micro/nanostructures, according to the scanning electron microscopy images, and the presence of such structures was further confirmed by the atomic force microscopy images. The developed nanocomposite coating was found to be highly superhydrophobic as well as corrosion resistant, according to the results from static contact angle measurement and potentiodynamic polarization measurement, respectively. The abrasion resistance and mechanical durability of the nanocomposite coating were studied by abrasion tests, and the mechanical properties such as reduced modulus and Berkovich hardness were evaluated with the aid of nanoindentation tests.

scholarly journals Characterization of Mechanical Heterogeneity in Dissimilar Metal Welded Joints

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4145
Author(s):  
He Xue ◽  
Zheng Wang ◽  
Shuai Wang ◽  
Jinxuan He ◽  
Hongliang Yang
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Welded Joints ◽  
Structural Integrity ◽  
Material Interfaces ◽  
Mechanical Heterogeneity ◽  
Finite Element Software ◽  
Dissimilar Metal ◽  
Stress Changes

Dissimilar metal welded joints (DMWJs) possess significant localized mechanical heterogeneity. Using finite element software ABAQUS with the User-defined Material (UMAT) subroutine, this study proposed a constitutive equation that may be used to express the heterogeneous mechanical properties of the heat-affected and fusion zones at the interfaces in DMWJs. By eliminating sudden stress changes at the material interfaces, the proposed approach provides a more realistic and accurate characterization of the mechanical heterogeneity in the local regions of DMWJs than existing methods. As such, the proposed approach enables the structural integrity of DMWJs to be analyzed in greater detail.

scholarly journals The Infuence of Salicin on Rheological and Film-Forming Properties of Collagen

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1661
Author(s):  
Katarzyna Adamiak ◽  
Katarzyna Lewandowska ◽  
Alina Sionkowska
Keyword(s):  
Mechanical Properties ◽  
Atomic Force Microscopy ◽  
Infrared Spectroscopy ◽  
Rheological Properties ◽  
Silver Carp ◽  
Shear Tests ◽  
Force Microscopy ◽  
Atomic Force ◽  
Film Forming ◽  
Potential Applications

Collagen films are widely used as adhesives in medicine and cosmetology. However, its properties require modification. In this work, the influence of salicin on the properties of collagen solution and films was studied. Collagen was extracted from silver carp skin. The rheological properties of collagen solutions with and without salicin were characterized by steady shear tests. Thin collagen films were prepared by solvent evaporation. The structure of films was researched using infrared spectroscopy. The surface properties of films were investigated using Atomic Force Microscopy (AFM). Mechanical properties were measured as well. It was found that the addition of salicin modified the roughness of collagen films and their mechanical and rheological properties. The above-mentioned parameters are very important in potential applications of collagen films containing salicin.

Does preconditioning lower the rupture resistance of chorioamniotic membrane?

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Arash Dadkhah ◽  
Ata Hashemi
Keyword(s):  
Mechanical Properties ◽  
Cesarean Delivery ◽  
Fetal Membrane ◽  
Premature Rupture ◽  
Rupture Stress ◽  
Probe Diameter ◽  
Healthy Pregnancy ◽  
Probe Size ◽  
Puncture Force ◽  
The Mean

AbstractPremature rupture of fetal membrane occurs in about 3% of all pregnancies. The physical integrity of chorioamnion (CA) membrane should be retained until delivery for a healthy pregnancy. To explore the effect of pre-conditioning and probe size on the mechanical properties of human chorioamniotic sac, the mechanical properties of 17 human chorioamniotic membranes, collected from cesarean delivery, were examined using biaxial puncture tests with and without preconditioning by different probe sizes. For preconditioned samples, the mean ± std. of ultimate rupture stress was calculated to be 1.73 ± 0.13, 1.61 ± 0.29 and 1.78 ± 0.26 MPa for the probe sizes of 3, 5 and 7 mm, respectively. For samples with no preconditioning, these values were calculated to be 2.38 ± 0.29, 2.36 ± 0.37, and 2.59 ± 0.43 MPa for the above-mentioned probe sizes. The force to probe diameter for samples with no preconditioning was in the range of 1087–1301 N/m for the three probe diameters, well in the range of 850–1580 N/m reported by previous studies. Our results show that the preconditioned samples had significantly lower ultimate puncture force and ultimate stress compared to non-preconditioned samples. In addition, a correlation between the probe size and the magnitude of puncture force was observed, while the stress values were not significantly affected by changing probe size.

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