Preform heating is one of the most important steps in the polymer fibre fabrication process due to the potential distortion that can be introduced when exposing the structure to high temperatures. Such heating is further complicated when internal air-structures are introduced into the preform such as in Microstructured Polymer Optical Fibre (MPOF) preforms. The aim of this study was thus to inv...

Preform design in multi-stage forging processes is critical to ensure the production of defect-free parts. Moreover, owing to the geometry and material-flow complexities in forging processes, finding the optimal preform shapes could be difficult and time consuming. This paper proposes an efficient preform design methodology based on geometrical resemblance, which requires several finite element...

An integrated modelling approach of Chemical Vapour In ltration of a brous preform by methyltrichlorosilane, featuring coupled reactor uid mechanics and porous medium gas transport has been developed. The coupling between transport/reaction phenomena inside and outside the preform is rather strong, both physically and numerically. An important counter-e ect of the reactive preform on the surrou...

To develop an effective process for tantalum powder production, a new preform reduction process (PRP) based on the magnesiothermic reduction of feed preform containing tantalum oxide (Ta2O5) was investigated. The feed preformwas fabricated from slurry, which was made by mixing Ta2O5 powder, flux (e.g., CaCl2), and binder. Various compositions of preform in the form of plates were prepared using...

Industrial glass blowing is an essential stage of manufacturing glass containers, i.e. bottles or jars. An initial glass preform is brought into a mould and subsequently blown into the mould shape. Over the last few decades, a wide range of numerical models for forward glass blow process simulation have been developed. A considerable challenge is the inverse problem: to determine an optimal pre...

in a closed die forging process, it is impossible to form complex shapes in one stage, and thus it becomes necessary to use preform dies. in the present study, backward deformation method and fe simulation via abaqus software has been used in order to design preform die of the h-shaped parts. in the backward deformation method, the final shape of the part is considered as a starting point and u...

In a closed die forging process, it is impossible to form complex shapes in one stage, and thus it becomes necessary to use preform dies. In the present study, Backward Deformation Method and FE simulation via ABAQUS software has been used in order to design preform die of the H-shaped parts. In the Backward Deformation Method, the final shape of the part is considered as a starting point and u...

North American lithic analysis often assigns biface preforms to discrete, successive stages defined in Callahan's influential study. Yet recent research questions the stage concept, emphasizing instead a continuous view of the reduction process. To compare stage and continuum approaches, their assumptions are tested in experimental replicas, including Callahan's, and empirical Paleoindian prefo...

In vacuum assisted resin transfer molding (VARTM) process, fiber preform defects result very often from inappropriate placement at edge regions when the fiber preform has three-dimensional shape. The unintentional permeability variation is difficult to detect by viewing through the transparent vacuum bag. In this paper, a method was proposed for detecting the local permeability variation of the...

A non-destructive technique is presented to determine the refractive index profile of holey fiber preforms. The holes are filled with index matching oil and the holey preform deflection data is measured. An improved optical path-length formula and back projection method is used to reconstruct the two-dimensional filled holey fiber preform refractive index distribution.