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Properties of Polymers - Their Correlation with Chemical Structure; Their Numerical Estimation and Prediction from Additive Group Contributions (4th, Completely Revised Edition)
This authoritative, widely cited book has been used all over the world. The Fourth Edition incorporates the latest developments in the field while maintaining the core objectives of previous editions: To correlate properties with chemical structure and to describe methods that permit the estimation and prediction of numerical properties from chemical structure, i.e. nearly all properties of the solid, liquid, and dissolved states of polymers.
eBook
A Transforming Metal Nanocomposite with Large Elastic Strain, Low Modulus, and High Strength
Freestanding nanowires have ultrahigh elastic strain limits (4 to 7%) and yield strengths, but exploiting their intrinsic mechanical properties in bulk composites has proven to be difficult. We exploited the intrinsic mechanical properties of nanowires in a phase-transforming matrix based on the concept of elastic and transformation strain matching. By engineering the microstructure and residual stress to couple the true elasticity of Nb nanowires with the pseudoelasticity of a NiTi shape-memory alloy, we developed an in situ composite that possesses a large quasi-linear elastic strain of over 6%, a low Young's modulus of ∼28 gigapascals, and a high yield strength of ∼1.65 gigapascals. Our elastic strain-matching approach allows the exceptional mechanical properties of nanowires to be exploited in bulk materials.
Journal Article
Anomalous Strength Characteristics of Tilt Grain Boundaries in Graphene
Graphene in its pristine form is one of the strongest materials tested, but defects influence its strength. Using atomistic calculations, we find that, counter to standard reasoning, graphene sheets with large-angle tilt boundaries that have a high density of defects are as strong as the pristine material and, unexpectedly, are much stronger than those with low-angle boundaries having fewer defects. We show that this trend is not explained by continuum fracture models but can be understood by considering the critical bonds in the strained seven-membered carbon rings that lead to failure; the large-angle boundaries are stronger because they are able to better accommodate these strained rings. Our results provide guidelines for designing growth methods to obtain sheets with strengths close to that of pristine graphene.
Journal Article
Ultrahard nanotwinned cubic boron nitride
The hardness, toughness and chemical stability of the well-known superhard material cubic boron nitride have been improved by using a synthesis technique based on specially prepared ‘onion-like’ precursor materials.
How to make superhard materials ultrahard
Superhard polycrystalline cubic boron nitride, second only to diamond in hardness, is superior to diamond in terms of thermal and chemical stability and is used widely as an abrasive. The hardness of many materials can be improved by decreasing the grain size, and here Yongjun Tian and colleagues use this principle in a new synthesis technique — based on specially prepared 'onion-like' precursor materials — capable of increasing the hardness of cubic boron nitride. The structure of the resulting polycrystalline material is dominated by nanometre-scale twin domains, yielding a solid combining ultrahigh hardness (exceeding that of a synthetic diamond single crystal) with a high oxidization temperature and extreme fracture toughness. If nanotwins at similar scales can be reproduced in polycrystalline diamond, it may be possible to raise diamond itself to new levels of hardness and stability.
Cubic boron nitride (cBN) is a well known superhard material that has a wide range of industrial applications. Nanostructuring of cBN is an effective way to improve its hardness by virtue of the Hall–Petch effect—the tendency for hardness to increase with decreasing grain size
1
,
2
. Polycrystalline cBN materials are often synthesized by using the martensitic transformation of a graphite-like BN precursor, in which high pressures and temperatures lead to puckering of the BN layers
3
. Such approaches have led to synthetic polycrystalline cBN having grain sizes as small as ∼14 nm (refs
1
,
2
,
4
,
5
). Here we report the formation of cBN with a nanostructure dominated by fine twin domains of average thickness ∼3.8 nm. This nanotwinned cBN was synthesized from specially prepared BN precursor nanoparticles possessing onion-like nested structures with intrinsically puckered BN layers and numerous stacking faults. The resulting nanotwinned cBN bulk samples are optically transparent with a striking combination of physical properties: an extremely high Vickers hardness (exceeding 100 GPa, the optimal hardness of synthetic diamond), a high oxidization temperature (∼1,294 °C) and a large fracture toughness (>12 MPa m
1/2
, well beyond the toughness of commercial cemented tungsten carbide, ∼10 MPa m
1/2
). We show that hardening of cBN is continuous with decreasing twin thickness down to the smallest sizes investigated, contrasting with the expected reverse Hall–Petch effect below a critical grain size or the twin thickness of ∼10–15 nm found in metals and alloys.
Journal Article
Mechanics of materials for dummies
Provides plain-English explanations of all the topics you'll encounter in a typical undergraduate course, including principles of equilibrium, geometric compatibility, and material behavior; stress and its relation to force and movement; strain and its relation to displacement; and methods for calculating deformations and indeterminate systems.
Book
A Review of the Effect of Plasticizers on the Physical and Mechanical Properties of Alginate-Based Films
In recent years, there has been a growing attempt to manipulate various properties of biodegradable materials to use them as alternatives to their synthetic plastic counterparts. Alginate is a polysaccharide extracted from seaweed or soil bacteria that is considered one of the most promising materials for numerous applications. However, alginate potential for various applications is relatively limited due to brittleness, poor mechanical properties, scaling-up difficulties, and high water vapor permeability (WVP). Choosing an appropriate plasticizer can alleviate the situation by providing higher flexibility, workability, processability, and in some cases, higher hydrophobicity. This review paper discusses the main results and developments regarding the effects of various plasticizers on the properties of alginate-based films during the last decades. The plasticizers used for plasticizing alginate were classified into different categories, and their behavior under different concentrations and conditions was studied. Moreover, the drawback effects of plasticizers on the mechanical properties and WVP of the films are discussed. Finally, the role of plasticizers in the improved processing of alginate and the lack of knowledge on some aspects of plasticized alginate films is clarified, and accordingly, some recommendations for more classical studies of the plasticized alginate films in the future are offered.
Journal Article