1,427 research outputs found
Exploiting the Design Freedom of RM
This paper details how Rapid Manufacturing (RM) can overcome the restrictions imposed by the
inherent process limitations of conventional manufacturing techniques and become the enabling
technology in fabricating optimal products. A new design methodology capable of exploiting
RM’s increased design freedom is therefore needed. Inspired by natural world structures of trees
and bones, a multi-objective, genetic algorithm based topology optimisation approach is
presented. This combines multiple unit cell structures and varying volume fractions to create a
heterogeneous part structure which exhibits a uniform stress distribution.Mechanical Engineerin
Statistical physics of cerebral embolization leading to stroke
We discuss the physics of embolic stroke using a minimal model of emboli
moving through the cerebral arteries. Our model of the blood flow network
consists of a bifurcating tree, into which we introduce particles (emboli) that
halt flow on reaching a node of similar size. Flow is weighted away from
blocked arteries, inducing an effective interaction between emboli. We justify
the form of the flow weighting using a steady flow (Poiseuille) analysis and a
more complicated nonlinear analysis. We discuss free flowing and heavily
congested limits and examine the transition from free flow to congestion using
numerics. The correlation time is found to increase significantly at a critical
value, and a finite size scaling is carried out. An order parameter for
non-equilibrium critical behavior is identified as the overlap of blockages'
flow shadows. Our work shows embolic stroke to be a feature of the cerebral
blood flow network on the verge of a phase transition.Comment: 11 pages, 11 figures. Major rewrite including improved justification
of the model and a finite size scalin
<i>d</i>-wave superconductivity from electron-phonon interactions
I examine electron-phonon mediated superconductivity in the intermediate coupling and phonon frequency regime of the quasi-two-dimensional Holstein model. I use an extended Migdal-Eliashberg theory that includes vertex corrections and spatial fluctuations. I find a d-wave superconducting state that is unique close to half filling. The order parameter undergoes a transition to s-wave superconductivity on increasing filling. I explain how the inclusion of both vertex corrections and spatial fluctuations is essential for the prediction of a d-wave order parameter. I then discuss the effects of a large Coulomb pseudopotential on the superconductivity (such as is found in contemporary superconducting materials like the cuprates), which results in the destruction of the s-wave states, while leaving the d-wave states unmodified
Recommended from our members
Rapid Manufactured Textiles
Rapid Manufacturing (RM) is increasingly becoming a viable manufacturing process due
to dramatic advantages that are achievable in the area of design complexity. Through the
exploration of the design freedom, this paper introduces the concept of manufacturing textiles for
potential smart and high performance textile applications. This paper discusses the current
limitations associated with the manufacture of textiles through RM and presents a novel
methodology for the generation of 3D conformal RM textile articles. The paper concludes that
through RM it is entirely possible to manufacture a structure that incorporates drape and free
movement properties directly comparable to conventional textiles.Mechanical Engineerin
Recommended from our members
Impact Absorbent Rapid Manufactured Structures (IARMS)
Rapid Manufacturing (RM) is increasingly becoming a viable manufacturing process due
to dramatic advantages that it facilitates in the area of design complexity. Through the
exploration of the design freedom afforded by RM, this paper introduces the concept and initial
research surrounding Impact Absorbent Rapid Manufactured Structures (IARMS), with an
application in sports personal protective equipment (PPE). Designs are based on the cellular
structure of foams; the inherent advantages of the cellular structure are used as a basis to create
IARMS that have the potential to be optimised for a specific impact absorbent response. The
paper provides some initial results from compression testingMechanical Engineerin
Recommended from our members
Analysis of Droplet Train/Moving Substrate Interactions in Ink-Jetting Processes
Ink-jetting technology has been applied to several processes in solid free-form
fabrication (SFF) wherein droplets impinge onto a substrate to deposit the build material.
Droplet impact behaviour on a surface has been the interest of many researchers; however,
few studies have been undertaken to investigate the interaction of droplets with the moving
substrate. This paper reports the impact behaviour of the droplets jetted at different
frequencies onto a substrate moving over a range of velocities. The phenomena associated
with the interaction were classified into three main regimes.Mechanical Engineerin
Recommended from our members
High Viscosity Jetting of Conductive and Dielectric Pastes for Printed Electronics
Ink-jet printing of multiple materials in 3 dimensions is a promising alternative to
traditional patterning methods due to its flexibility, scalability and accuracy. However, the
printability of the inks is strongly restricted by material properties such as surface tension and
viscosity. Dispensing high viscosity fluids on a drop-on-demand approach is a potential solution
that can facilitate the incorporation of new materials to the jetting catalogue. Consequently, in
this study 2 micro-dispensing valves are used in combination with a mechanical stage to deposit
conductive and dielectric pastes with viscosities of 15.3 ± 0.2 and 0.638 ± 0.005 Pa·s (at 25°C
and 10 s-1 shear rate) respectively. Crucial printing parameters such as pressure, temperature,
pulse shape and drop spacing are studied in order to optimise the process. Additionally, post-printing characteristics such as contact angle of different materials and cured layer profiles are
also measured and taken into account during the designing of the 3D patterns to minimise the
negative effects of the thickness miss-match of different materials. Finally, the manufacturing
capability of the set-up is demonstrated by the fabrication of a functional device using a
combination of “pick-and-place” components and high viscosity jetting.Mechanical Engineerin
- …