Search results

Observes that the formability of woven fabric has a major effect on the appearance of garments, in that seams sewn from fabrics with low formability are more likely to pucker than those sewn from fabric with high formability. Describes the concept of formability and illustrates the relationship between this parameter and seam pucker, the difficulty of a particular sewing operation and the appearance of structured jackets. Notes that the formability of wool fabrics is most appropriately controlled in finishing by modifying the extensibility of the fabric. Discusses the difficulties associated with engineering, the extensibility of woven fabrics and the implications for other fabric properties, such as relaxation shrinkage.

This paper aims to propose a functional methodology to produce cranial prostheses in polymeric sheet. Within the scope of rapid prototyping technologies, the single-point incremental forming (SPIF) process is used to demonstrate its capabilities to perform customized medical parts.

The methodology starts processing a patient’s computerized axial tomography (CAT) and follows with a computer-aided design and manufacture (CAD/CAM) procedure, which finally permits the successful manufacturing of a customized prosthesis for a specific cranial area.

The formability of a series of polymeric sheets is determined and the most restrictive material among them is selected for the fabrication of a specific partial cranial prosthesis following the required geometry. The final strain state at the outer surface of the prosthesis is analysed, showing the high potential of SPIF in manufacturing individualized cranial prostheses from polymeric sheet.

This paper proposes a complete methodology to design and manufacture polymer customized cranial prostheses from patients’ CATs using the novel SPIF technology. This is an application of a new class of materials to the manufacturing of medical prostheses by SPIF, which to this purpose has been mainly making use of metallic materials so far. Despite the use of polymers to this application is still to be validated from a medical point of view, transparent prostheses can already be of great interest in medical or engineering schools for teaching and research purposes.

The mechanical properties of fabric longitudinal extension and compression, shear and bending have an important influence on the performance of fabrics during tailoring and also on the performance of garments during use. Fabrics are overfed or underfed in tailoring during the sewing operations in such a way that longitudinal compression and extension are allowed in the fabric plane in order to produce the three‐dimensional shape or fullness of the garment. Fabric buckling or puckering at the seams should not occur, or if it does, should be removed during subsequent steam pressing operations. An experiment is described to measure the maximum limit of overfeeding that is possible during seaming without the subsequent formation of seam puckers. The relationships are studied between the maximum degree of overfeed, the bias angle between the feed direction and the fabric warp or weft, fibre type and fabric mechanical properties, especially fabric formability defined as the product of fabric bending rigidity and fabric longitudinal compressibility. When fabrics are extended or compressed longitudinally at a bias angle to the warp or weft direction during seaming in order to produce garment fullness, the warp and weft threads are rotated relative to each other in such a way that a local shear deformation is applied to the fabric adjacent to the seam‐line. Measurements are reported of the variations in the local shear angle along the shoulder seam‐line of a men's jacket and the measured values are related to the high degree of overfeed required in the bias direction in this area of the garment. Finally, hygral expansion measurements for wool fabrics and yarns unravelled from the fabrics are measured and compared for six different wool fabrics.

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder metallurgy and composite material processing are briefly discussed. The range of applications of finite elements on these subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE researchers/users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for 1994‐1996, where 1,370 references are listed. This bibliography is an updating of the paper written by Brannberg and Mackerle which has been published in Engineering Computations, Vol. 11 No. 5, 1994, pp. 413‐55.

The purpose of this paper is to investigate the strain distribution, stress-based fracture limit and corrosion behaviour of titanium Grade 2 sheets during single point incremental forming (SPIF) process, with various computerized numerical control (CNC) spindle rotational speeds and step depths. The development of corrosion pits in 3.5 (%) NaCl solution has also been studied during the SPIF process.

A potentiodynamic polarization (PDP) study was performed to investigate the corrosion behaviour of titanium Grade 2 deformed samples, with various spindle rotational speeds in 3.5 (%) NaCl solution. The scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis was carried out to study the fracture behaviour, dislocation densities and corrosion morphology of deformed samples.

The titanium Grade 2 sheets exhibited better strain distribution, fracture limit and corrosion resistance by increasing the CNC spindle rotational speeds, tool diameters and vertical step depths (VSD). It was recorded that varying the spindle speed affected plastic deformation which in turn affected corrosion rate.

In this study, poor corrosion rate was observed for the as-received condition, and better corrosion rate was achieved at maximum speed of 600 rpm and 0.6 mm of VSD in the deformed sheet. This indicates that corrosion rate improved with increase in the plastic deformation. The EDS analysis report of corroded surface revealed the composition to be mainly of titanium and oxides.

This study discusses the strain distribution, stress-based fracture limit and corrosion behaviour by using titanium Grade 2 sheets during SPIF process.

This study is useful in the field of automobile and industrial applications.

With an increase in the spindle rotational speeds and VSD, the titanium Grade 2 sheets showed better strain distribution, fracture limit and corrosion behaviour; the same is evidenced in fracture limit curve and PDP curves.

Evaluates the mechanical properties of 60 different shirting materials: fabric extensibility, formability, shear rigidity, bending rigidity, relaxation shrinkage, and hygral expansion by the adoption of the fabric assurance by simple testing (FAST) system. Investigates manufacturing processes comprising spreading, cutting, sewing, handling, pressing and packaging and correlates the measured properties of the shirting fabric with their actual performance during making up. Claims this overall evaluation of respective fabric performance enables manufacturers to identify the range of mechanical properties ideal for high‐quality shirt production. Adds that specific manufacturing instructions can be prepared, based on the results of fabric property evaluation, for fabrics which tend to present difficulties in production. Points out that these can considerably expedite the manufacture of garments, avoiding the alternative – expensive “trial and error” – solution to problems.

The current work aims to propose a finite element (FE) simulation methodology to predict the formability of friction stir processed (FSPed) tubes by end forming. Moreover, a strain mapping method is also presented to predict the end forming instabilities.

In this work, FE simulation of end forming of raw tubes and FSPed AA6063-T6 tubes are done using Abaqus (explicit) incorporating anisotropic properties of the raw tube and FSPed zone. Actual thickness of the FSPed zone is also implemented. Expansion, reduction and beading are the end forming operations considered. Load requirement and instabilities are predicted. A new method “strain mapping method” is followed to predict the failure instabilities in expansion and beading, while during reduction, wrinkling is predicted by FE simulations. Lab scale experiments on FSP and end forming are done for validation at various rotational speeds.

Results reveal that in the case of expansion and reduction of FSPed tubes, forming load predictions are accurate, while in beading, after initiation of bead, predictions are not accurate. Experimental observation on the type of instability is consistently predicted during numerical simulations. Prediction of displacement at failure by strain mapping method is encouraging in most of the cases including those that are FSPed. Hence, it is suggested that the method can be utilized to evaluate the onset of failure during tube expansion and beading.

FE simulation methodology including anisotropic properties of raw tube and FSPed tubes is proposed, which is not attempted until now even for normal tubes. Strain mapping method is easy to implement for instability predictions, which is done usually by failure theories and forming limit diagram.

THE modern aeroplane is constructed largely from sheet metal. As such, the most important production problems are those of sheet metal forming, and assembling. Production is here considered as not only the act of forming and assembling the required number of parts, but also the making of forming tools, and all processing of parts such as heat‐treating. Only that phase of the above concept of production which deals with the tooling for production and the forming and heat‐treating will be considered here. The design of the aircraft parts will also be discussed somewhat, for it is obvious that the design of the part (designed shape and materials used) frequently determines whether the part can or cannot be readily made.

Sheet metal forming is a process of shaping thin sheets of metal by applying pressure through male or female dies or both. In most of used sheet‐formating processes the metal is subjected to primarily tensile or compressive stresses or both. During the last three decades considerable advances have been made in the applications of numerical techniques, especially the finite element methods, to analyze physical phenomena in the field of structural, solid and fluid mechanics as well as to simulate various processes in engineering. These methods are useful because one can use them to find out facts or study the processes in a way that no other tool can accomplish. Finite element methods applied to sheet metal forming are the subjects of this paper. The reason for writing this bibliography is to save time for readers looking for information dealing with sheet metal forming, not having an access to large databases or willingness to spend own time with uncertain information retrieval. This paper is organized into two parts. In the first one, each topic is handled and current trends in the application of finite element techniques are briefly mentioned. The second part, an Appendix, lists papers published in the open literature. More than 900 references to papers, conference proceedings and theses/dissertations dealing with subjects that were published in 1995‐2003 are listed.

AT Lockheed (Ref. 18) the double‐acting press has been used toad vantage in this work, as it permits the part to be held at the edges while the punchforms it, thereby building up the desired tensile stress. This is illustrated by Fig. 32. The same general effect may be obtained in the single‐acting press with rubber punch by the use of special concave blocks in which the sheet is clamped at the edges by means of beaded plates or other devices. Mechanical stretching machines are also available for this type of work. These methods are generally not as satisfactory as the double‐acting press, however, as the latter permits greater control over the edge restraint conditions.