다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Publisher Summary This chapter describes the mixed mode cracking in layered materials. There is ample experimental evidence that cracks in brittle, isotropic, homogeneous materials propagate such that pure mode I conditions are maintained at the crack tip. An unloaded crack subsequently subject to a combination of modes I and II will initiate growth by kinking in such a direction that the advancing tip is in mode I. The chapter also elaborates some of the basic results on the characterization of crack tip fields and on the specification of interface toughness. The competition between crack advance within the interface and kinking out of the interface depends on the relative toughness of the interface to that of the adjoining material. The interface stress intensity factors play precisely the same role as their counterparts in elastic fracture mechanics for homogeneous, isotropic solids. When an interface between a bimaterial system is actually a very thin layer of a third phase, the details of the cracking morphology in the thin interface layer can also play a role in determining the mixed mode toughness. The elasticity solutions for cracks in multilayers are also elaborated.

Mixed mode cracking in layered materials

http://www.tara.tcd.ie/bitstream/handle/2262/54960/Biomaterials%20and%20scaffolds%20for%20tissue%20engineering.pdf;sequence=1

Biomaterials & scaffolds for tissue engineering

Particle reinforced metal matrix composites are now being produced commerically, and in this paper the current status of these materials is reviewed. The different types of reinforcement being used, together with the alternative processing methods, are discussed. Depending on the initial processing method, different factors have to be taken into consideration to produce a high quality billet. With powder metallurgy processing, the composition of the matrix and the type of reinforcement are independent of one another. However, in molten metal processing they are intimately linked in terms of the different reactivities which occur between reinforcement and matrix in the molten state. The factors controlling the distribution of reinforcement are also dependent on the initial processing method. Secondary fabrication methods, such as extrusion and rolling, are essential in processing composites produced by powder metallurgy, since they are required to consolidate the composite fully. Other methods, suc...

Particle reinforced aluminium and magnesium matrix composites

This paper reviews the past, present, and future of the hydroxyapatite (HAp)-based biomaterials from the point of view of preparation of hard tissue replacement implants. Properties of the hard tissues are also described. The mechanical reliability of the pure HAp ceramics is low, therefore it cannot be used as artificial teeth or bones. For these reasons, various HAp-based composites have been fabricated, but only the HAp-coated titanium alloys have found wide application. Among the others, the microstructurally controlled HAp ceramics such as fibers/whiskers-reinforced HAp, fibrous HAp-reinforced polymers, or biomimetically fabricated HAp/collagen composites seem to be the most suitable ceramic materials for the future hard tissue replacement implants.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400042527

Processing and properties of hydroxyapatite-based biomaterials for use as hard tissue replacement implants

It is known for a long time that mechanical twinning occurring in FCC metal can bring about a very large work hardening rate. It is believed that deformation twins increase the work-hardening rate by acting as obstacles for gliding dislocations. This mode of plastic deformation is active, among others, in the Hadfield steel known for a very long time [1]. Fe-Mn-C grades exhibiting mechanical twinning present a renewed interest for some years since some applications are expected in the automotive industry. Several kinds of TWIP (Twinning Induced Plasticity) steels are now intensively studied.

Multiscale characterisation of the plasticity of Fe-Mn-C TWIP steels

Contribution of the nucleation and recovery of disconnections to shear viscosity in diffusional creep

Effect of shape accomodation on the equilibrium distribution of liquid in assemblies of WC/Co cermets

The possibility of reinforcing the age-hardenable aluminium alloy AS9G03 by stainless steel fibres is explored. A first part of the work concerns the composite processing by squeeze casting. Several processing parameters had to be controled in order to obtain a sound material with optimised microstructure. In a second part, the age-hardening of the composite is considered. The oxide layer on the fibres which was designed to prevent the fibre/matrix reaction during the heat-treatment is showed to strongly affect age-hardening due to the diffusion of Mg towards the oxidic fibre/matrix interface. The paper shows how precipitation hardening can be ensured in the composite by adjustment of solution treatment temperature and time and oxide layer thickness.

Hardening of an aluminium alloy matrix composite reinforced with stainless steel fibres

A critical comparison is made of improved versions of the peel test and wedge test for the measurement of the interface toughness of adhesive joints consisting of thin steel or Al-alloy plates bonded with epoxy adhesive. The opening of the plates in the wedge test is monitored by displacement sensors in such a way as to allow continuous recording of the crack length. A wide range of debond extension rates can be investigated in this way. For the peel test, the two metallic plates are attached on two rollers in such a way as to impose a constant radius of curvature during the progress of decohesion. The intrinsic character of this measured decohesion energy is validated by varying the plates thickness. Depending on the method of crack length measurement, the toughness values measured by the wedge test are upper and lower bounds enclosing the value obtained with the peel test. The physical origins of the scatter obtained with the wedge test is critically evaluated. The new peel test makes possible the control of loading mixity, which was found beneficial in order to drive the debond path toward the coating/substrate interface.

Francis Delannay

Papers

Multiscale characterisation of the plasticity of Fe-Mn-C TWIP steels

Contribution of the nucleation and recovery of disconnections to shear viscosity in diffusional creep

Effect of shape accomodation on the equilibrium distribution of liquid in assemblies of WC/Co cermets

Hardening of an aluminium alloy matrix composite reinforced with stainless steel fibres

Interface toughness of joints of adhesively bonded metallic plates measured by improved types of wedge and peel tests