142 research outputs found
Hot Extrusion of Ceramics
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65963/1/j.1151-2916.1992.tb07206.x.pd
Evaluation of strain and stress states in the single point incremental forming process
Single point incremental forming (SPIF) is a promising
manufacturing process suitable for small batch production.
Furthermore, the material formability is enhanced in
comparison with the conventional sheet metal forming processes,
resulting from the small plastic zone and the incremental
nature. Nevertheless, the further development of the SPIF
process requires the full understanding of the material deformation
mechanism, which is of great importance for the effective
process optimization. In this study, a comprehensive
finite element model has been developed to analyse the state
of strain and stress in the vicinity of the contact area, where the
plastic deformation increases by means of the forming tool
action. The numerical model is firstly validated with experimental
results from a simple truncated cone of AA7075-O
aluminium alloy, namely, the forming force evolution, the
final thickness and the plastic strain distributions. In order to
evaluate accurately the through-thickness gradients, the blank
is modelled with solid finite elements. The small contact area
between the forming tool and the sheet produces a negative
mean stress under the tool, postponing the ductile fracture
occurrence. On the other hand, the residual stresses in both
circumferential and meridional directions are positive in the
inner skin of the cone and negative in the outer skin. They
arise predominantly along the circumferential direction due to
the geometrical restrictions in this direction.The authors would like to gratefully acknowledge the
financial support from the Portuguese Foundation for Science and Technology
(FCT) under project PTDC/EMS-TEC/1805/2012. The first author is
also grateful to the FCT for the postdoctoral grant SFRH/BPD/101334/2014.info:eu-repo/semantics/publishedVersio
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Congenital Diarrhea and Cholestatic Liver Disease: Phenotypic Spectrum Associated with MYO5B Mutations.
Myosin Vb (MYO5B) is a motor protein that facilitates protein trafficking and recycling in polarized cells by RAB11- and RAB8-dependent mechanisms. Biallelic MYO5B mutations are identified in the majority of patients with microvillus inclusion disease (MVID). MVID is an intractable diarrhea of infantile onset with characteristic histopathologic findings that requires life-long parenteral nutrition or intestinal transplantation. A large number of such patients eventually develop cholestatic liver disease. Bi-allelic MYO5B mutations are also identified in a subset of patients with predominant early-onset cholestatic liver disease. We present here the compilation of 114 patients with disease-causing MYO5B genotypes, including 44 novel patients as well as 35 novel MYO5B mutations, and an analysis of MYO5B mutations with regard to functional consequences. Our data support the concept that (1) a complete lack of MYO5B protein or early MYO5B truncation causes predominant intestinal disease (MYO5B-MVID), (2) the expression of full-length mutant MYO5B proteins with residual function causes predominant cholestatic liver disease (MYO5B-PFIC), and (3) the expression of mutant MYO5B proteins without residual function causes both intestinal and hepatic disease (MYO5B-MIXED). Genotype-phenotype data are deposited in the existing open MYO5B database in order to improve disease diagnosis, prognosis, and genetic counseling
Analysis of fracture modes during extrusion and drawing of bimetal rods or wire. Analytical study of drawing and extrusion of superconducting filamentary wires: fracture problems and evaluation of temperature rise. Final report
Based on the upper-bound theorem in limit analysis, a theoretical model describing sound flow, core fracture, and sleeve fracture in bimetal rods and wire during extrusion and drawing was developed. The variables affecting core and sleeve fracture are: reduction in area, die geometry, friction, relative size and strength of the core, and applied surface tractions. Within the wide range of combinations of these process variables, only a small range permits co-extrusion and codrawing without fracture. Criteria for the prevention of core and sleeve fracture during co-extrusion and core fracture during co-drawing were developed and presented graphically in this study. The results were applied to the central burst problem during extrusion and drawing of homogeneous materials
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