Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
40,570
result(s) for
"Hardness."
Sort by:
Is it flexible or rigid?
Discusses the properties of matter, focusing on whether an object is flexible or not with definitions and examples to illustrate.
Book
Strengthening mechanisms in AlCoCrFeNiMo.sub.0.8-TiC composite coating based on first-principles calculations
The excellent hardness and wear resistance of AlCoCrFeNiMo.sub.0.8-TiC composite coating benefit from various strengthening mechanisms, including fine grain strengthening, dislocation strengthening, load transfer strengthening, solid solution strengthening, and precipitation strengthening. To analyze their contributions in the strength and hardness, an accurate prediction model is essential. In this work, a prediction model for the hardness increment was established based on some key elastic constants calculated by the first-principles. Subsequently, the contributions of strengthening mechanisms were quantitatively evaluated by the developed prediction model. It was found that the Young's modulus and shear modulus for B2 phase were 179.65 GPa and 67.36 GPa, respectively, and those of [sigma] phase were 354.08 GPa and 139.19 GPa, respectively. The precipitation strengthening was the predominant mechanism in the composite coating, with a strength contribution of 736.4 MPa and a hardness contribution of 225.2 HV, which accounted for 76.2% of the contribution values. The prediction model has high accuracy, which is evidenced by the small relative error (9.1%) between the total theoretical hardness contribution (295.2 HV) and the Vickers hardness tested by nanoindentation (322.1 HV).
Journal Article
Effects of Residual Stresses on the Structures and Mechanical Behavior of ZrOsub.xNsub.y/Vsub.2Osub.3 Nano-Multilayers
Residual stress plays a crucial role in determining the structural reliability and mechanical performance of nano-multilayers. In the present study, nano-multilayers composed of ZrO[sub.x]N[sub.y] and V[sub.2]O[sub.3] were deposited via magnetron sputtering, with the N:Ar flow ratio systematically varied during the process. Through the precise control of the deposition conditions, the compressive residual stress within the films was effectively reduced to approximately 0 GPa, thereby improving their mechanical robustness. It was observed that the optimization of the stress distribution was strongly influenced by the structural symmetry of the multilayer configuration. This symmetrical design not only mitigated stress accumulation but also ensured uniform mechanical response throughout the multilayer structure. The results from nanoindentation testing revealed a steady hardness value near 10.6 GPa. Furthermore, the maximum H[sup.3]/E[sup.2] and H/E ratios recorded were 0.054 GPa and 0.073, respectively, suggesting enhanced resistance to both plastic deformation and cracking.
Journal Article
Interpretation of ISO 185: \2020 Grey Cast Irons-Classification\
The overview of ISO 185: 2020 Grey Cast Irons-Classification, the main contents of standard revision and typical applications were introduced.The main contents of the standard were described in detail, including the scope, material brand, tensile strength of cast sample, tensile strength of body sample, hardness, metallographic structure, sample preparation and retests.
Journal Article
A new rock hardness classification system based on portable dynamic testing
Hardness is one of the critical physical characteristics of minerals and rocks, which indicates the resistance of the rock to penetration, scratch, or permanent deformation. As a basic concept, rock hardness has a significant role in rock mechanics and geological engineering and is an appropriate diagnostic tool for the classification of minerals and rocks. The main purpose of this study is to guide rock engineers to measure the rock hardness faster, easier, and more accurately using Leeb’s dynamic hardness test. Accordingly, this paper presents a new rock hardness classification system based on the Leeb dynamic and portable hardness testing method. It is a well-known method for its fast and straightforward procedure testing equipment. A set of 33 different rock types were collected and tested during this study. Next, in-depth microscopic mineralogical studies were performed to determine the precise Mohs hardness value. The Mohs hardness was considered the leading hardness benchmark during the experimental studies, and the Leeb hardness was adopted to classify based on this hardness. A series of laboratory studies and statistical analysis was performed to predict the Shore and Vickers hardness using Leeb hardness. Finally, based on the comparative studies, it is recommended to classify the rocks considering the Leeb hardness method in six different categories: extremely soft (1–250), soft (250–450), moderately soft (450–750), moderately hard (750–850), hard (850–920), and extremely hard (920–1000). The provided classification could be useful in a vast range of rock engineering applications, especially for feasibility studies of rock engineering projects and engineering geology.
Journal Article
Comparative investigation of Shore, Schmidt, and Leeb hardness tests in the characterization of rock materials
Prediction of physical and mechanical properties of rock materials using rebound-based hardness test methods is widely preferred in many fields of engineering and in the characterization of rock materials, because they are non-destructive, practical, and economical. In this study, 40 types of rocks with magmatic, metamorphic, and sedimentary origins, represented by travertine, limestone, marble, dolomite, granite, syenite, dunite, andesite, schist, gabbro, tuff, and ignimbrite were selected. First, dry unit weight (γd), open porosity (no), water absorption by weight (WAW), wide wheel abrasion (WA), and uniaxial compressive strength values were determined. After that, Shore C-2 scleroscope (HSC), L-type Schmidt hammer (HSL), and Leeb (HLD) rebound-based hardness tests were carried out on all samples, and then, hardness values by three methods were compared with the obtained parameters. The Leeb hardness test, which is more recent and innovative than the Shore and Schmidt hardness tests, was initially developed for metallic materials. However, the method has become increasingly popular in the determination of hardness of rock materials in laboratory as well as in field. In this study, the Leeb hardness test was found to be more useful due to its quick and precise measurement capabilities compared to Shore and Schmidt hardness tests. The results of the study reveal that the prediction of physical and mechanical properties of rocks can more precisely be determined by the HLD method than the HSL and HSC methods using the proposed equations.
Journal Article
Time-Dependent Evolution of Al–Alsub.4Csub.3 Composite Microstructure and Hardness during the Sintering Process
In this study, Al-Al[sub.4]C[sub.3] compounds were manufactured by mechanical milling followed by heat treatment. To analyze the microstructural evolution, the composites were sintered at 550 °C at different sintering times of 2, 4 and 6 h. The mechanical results suggest that dislocation density and crystallite size primarily contribute to hardening before the sintering process, with a minimal contribution from particle dispersion in this condition. The compound exhibited a significant 75% increase in hardness after 2 h of sintering, primarily attributed to the nucleation and growth of Al[sub.4]C[sub.3] nanorods. The HRTEM analysis, combined with geometric phase analysis (GPA) at and near the Al-Al[sub.4]C[sub.3] interface of the nanorods, revealed strain field distributions primarily associated with partial screw dislocations and the presence of closely spaced dislocation dipoles. These findings are consistent with the microstructural parameters determined from X-ray diffraction pattern analysis using the convolutional multiple whole profile (CMWP) method. This analysis showed that the predominant dislocation character is primarily of the screw type, with the dislocation dipoles being closely correlated. Based on these results, it is suggested that samples with a lower weight percentage of reinforcement and longer sintering times may experience reduced brittleness in Al/Al[sub.4]C[sub.3] composites. Strengthening contributions were calculated using the Langford–Cohen and Taylor equations.
Journal Article
ZrBsub.2–Copper–Graphite Composite for Electric Brushes: Positive Effect of ZrBsub.2 Addition on Composite Properties
A ZrB[sub.2]–copper–graphite composite was produced through powder metallurgy and was tested as a new electric brush material. The aim of this paper was to study the effect of ZrB[sub.2] addition on the composite’s properties. Besides its physical properties such as density and resistivity, its mechanical properties, such as hardness, bending strength and wear resistance, were studied. A scanning electron microscope (SEM) was used to study the morphology of the wear surface, and a configured energy-dispersive spectrometer (EDS) was used to research the chemical composition of the samples. The results showed that, with the addition of ZrB[sub.2], the composite’s properties such as density, resistivity, hardness, and bending strength improved significantly. Compared with samples without ZrB[sub.2], samples with the addition of 4% ZrB[sub.2] achieved a hardness of 87.5 HRA, which was improved by 45.8%, and a bending strength of 53.1 MPa, which was increased by nearly 50.0%. Composites with 1% content of ZrB[sub.2] showed the best wear resistance under non-conductive friction; however, under conductive friction, composites with 4% content of ZrB[sub.2] showed better wear resistance.
Journal Article
Microstructure and Tribo-Behavior of WC–Crsub.3Csub.2–Ni Coatings by Laser Cladding and HVAF Sprayed: A Comparative Assessment
SK5 steel is the base material used for the preparation of the wrinkle scraper, whose service life strongly affects the working efficiency and economic benefits. In this work, WC-Cr3C2-Ni coating was deposited on the SK5 steel substrate by using High-velocity air fuel spray (HVAF) and Laser cladding (LC) processes respectively, named HVAF-WC coating and LC-WC coating. The microstructure and wear resistance of both coatings were analyzed, and were compared with the substrate sample. Results showed that the coatings were adhesive well onto the substrate. More WC with fine crystals is retained in HVAF-WC coating due to low flame flow temperature, while WC of LC-WC coating is characterized by columnar crystals. The wear rate of HVAF-WC and LC-WC coating was 4.00 × 10[sup.−7] mm[sup.3]/(N*m) and 3.47 × 10[sup.−6] mm[sup.3]/(N*m), respectively, which was two and one orders of magnitude lower than SK5 steel with 3.54 × 10[sup.−5] mm[sup.3]/Nm. HVAF-WC coating exhibited the best wear resistance because of significant fine grain strengthening, which wear mechanism is mainly dominated by abrasive wear. Thus, it was thought that HVAF-WC coating is more effective ways to improve the wear resistance of SK5 steel, comparing with LC-WC coating.
Journal Article
Tungsten tetraboride, an inexpensive superhard material
Tungsten tetraboride (WBâ) is an interesting candidate as a less expensive member of the growing group of superhard transition metal borides. WBâ was successfully synthesized by arc melting from the elements. Characterization using powder X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) indicates that the as-synthesized material is phase pure. The zero-pressure bulk modulus, as measured by high-pressure X-ray diffraction for WBâ, is 339 GPa. Mechanical testing using microindentation gives a Vickers hardness of 43.3 ± 2.9 GPa under an applied load of 0.49 N. Various ratios of rhenium were added to WBâ in an attempt to increase hardness. With the addition of 1 at.% Re, the Vickers hardness increased to approximately 50 GPa at 0.49 N. Powders of tungsten tetraboride with and without 1 at.% Re addition are thermally stable up to approximately 400 °C in air as measured by thermal gravimetric analysis.
Journal Article