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Aerospace industry was pioneered in the use of superplastic forming (SPF) process. Weight saving is the most important need in this industry. For this reason, there is special attention paid to this method. Blow forming is a common method for SPF process. Process parameters such as temperature and pressure have significant effects on part accuracy, quality and desired characteristics. The purpose of this paper is to present a numerical and experimental investigation of process parameters in superplastic free bulge forming.

In this paper, superplastic free bulge forming of Al‐5083 has been studied. First, free bulge tests have been done at two different pressures. Bulge height variations were recorded for different pressure and temperature. The forming time was determined according to the forming pressure and temperature. Then, simulation of free bulge process has been carried out using creep behavior model at high temperature. Bulge height and thickness distribution are obtained at two different pressure settings. These results have been compared with experimental results presenting a good agreement. Also the effects of temperatures and pressure on the required process time are compared for a certain bulge height. Finally, thickness distribution profile for different temperatures, pressures and initial thicknesses have been studied.

A numerical and experimental investigation has been presented that can be used to study the process parameters. These findings show the effects of temperatures, pressure and initial thicknesses on sheet forming.

The results of this work show that higher temperature and forming pressure will reduce the required process time for a certain bulge height. Reduction of these parameters can improve thickness distribution. Also, by considering the effects of both pressure and temperature, it is shown that using lower forming pressure at higher temperature is more suitable for forming. The findings of this work can provide more understanding of the process for aircraft part designers and manufacturing process planners.

THE elastic members used in flexible engine mountings are nearly always made of rubber, cither natural or synthetic, bonded or unbonded. The reason for this is that although metallic springs could be designed to have the required stiffness properties they have very little natural damping and would allow very large amplitudes to build up at resonant conditions unless some external damping device such as friction disks or oil dashpots were employed. Also it is a difficult matter to anchor a metallic spring in such a way that fretting will not occur at the fixing point. Rubber on the other hand has considerable damping properties and it is this (plus its high specific resilience) which has largely determined its pre‐eminence in this field.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics and publications of other similar research bodies as issued

A marked characteristic of rubber‐like materials is the nearly incompressible behaviour. This type of behaviour is best modelled by mixed finite elements with separate interpolation functions for the displacements and the pressure. In this contribution the performance of three‐dimensional elements is investigated using a two‐tiered strategy. First, the ability of some linear and quadratic three‐dimensional elements to deform correctly under nearly isochoric conditions is estimated using the well‐known constraint‐counting method, in which the ratio of the number of degrees‐of‐freedom over the number of kinematic constraints present in the finite element mesh is determined. Next, the performance of the elements is assessed by numerical simulations for three cuboidal rubber blocks with different shape factors. The results turn out to be quite sensitive with respect to the ratio of the number of degrees‐of‐freedom over the number of kinematic constraints, since too many pressure degrees‐of‐freedom make the element overstiff, while too few pressure degrees‐of‐freedom may cause the occurrence of spurious kinematic modes. This observation appears to be not only valid for the global structural behaviour, but also with respect to the specific parts in the structure, where the above‐mentioned ratio is different from the global number, e.g., in corners of the structure.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics and publications of other similar research bodies as issued

To provide a selective bibliography for researchers working with bulk material forming (specifically the forging, rolling, extrusion and drawing processes) with sources which can help them to be up‐to‐date.

A range of published (1996‐2005) works, which aims to provide theoretical as well as practical information on the material processing namely bulk material forming. Bulk deformation processes used in practice change the shape of the workpiece by plastic deformations under forces applied by tools and dies.

Provides information about each source, indicating what can be found there. Listed references contain journal papers, conference proceedings and theses/dissertations on the subject.

It is an exhaustive list of papers (1,693 references are listed) but some papers may be omitted. The emphasis is to present papers written in English language. Sheet material forming processes are not included.

A very useful source of information for theoretical and practical researchers in computational material forming as well as in academia or for those who have recently obtained a position in this field.

There are not many bibliographies published in this field of engineering. This paper offers help to experts and individuals interested in computational analyses and simulations of material forming processes.

The purpose of this paper is to propose a progressive inverse identification algorithm to characterize flow stress of tubular materials from the material response, independent of choosing an a priori hardening constitutive model.

In contrast to the conventional forward flow stress identification methods, the flow stress is characterized by a multi-linear curve rather than a limited number of hardening model parameters. The proposed algorithm optimizes the slopes and lengths of the curve increments simultaneously. The objective of the optimization is that the finite element (FE) simulation response of the test estimates the material response within a predefined accuracy.

The authors employ the algorithm to identify flow stress of a 304 stainless steel tube in a tube bulge test as an example to illustrate application of the algorithm. Comparing response of the FE simulation using the obtained flow stress with the material response shows that the method can accurately determine the flow stress of the tube.

The obtained flow stress can be employed for more accurate FE simulation of the metal forming processes as the material behaviour can be characterized in a similar state of stress as the target metal forming process. Moreover, since there is no need for a priori choosing the hardening model, there is no risk for choosing an improper hardening model, which in turn facilitates solving the inverse problem.

The proposed algorithm is more efficient than the conventional inverse flow stress identification methods. In the latter, each attempt to select a more accurate hardening model, if it is available, result in constructing an entirely new inverse problem. However, this problem is avoided in the proposed algorithm.

Barreling contour variations on the free surfaces of cylindrical upset specimen are to handle measuring for different upsetting reductions and different lubrication conditions in this study. The purpose of this paper is to address this issue.

The materials flow for various materials using different lubricants in upsetting was investigated in this study. SAE 1020 steel, commercially pure copper and CuZn40Pb2 brass were used as the test materials. Upsetting process was applied to the cylindrical specimens using flat end dies. Three types of lubricants, namely grease, graphite and SAE 40 oil, were used in this study. Experiments were performed using a hydraulic press, which has 5 mm/s ram speed, and with a capacity of 150 metric tons.

Variations of barrel radius change clearly with increasing deformation ratio depending on lubricant type. Radius values are different to each other for SAE 1020, Cu and brass specimens. It was understood that surface roughness effect is negligible at material types. The highest radius values were obtained for the brass among all the materials for the same deformation ratio. The materials flow is hard for brass specimens because of its brittleness which is due to cold drawing so its barrel radii are high. On the contrary, SAE 1020 and copper are more suitable for the plastic deformation. As shown in the Figures, the higher radius values were obtained especially with grease lubricant for brass specimens.

It would be interesting to search material flow for different materials and lubricants. It could be a good idea for future work could be concentrated material flow on upsetting using different lubricants.

The friction at the faces of contact retards the plastic flow of metals and the surfaces and in its vicinity. A conical wedge of a relatively undeformed metal is formed immediately below it, while the rest of the cylinder metal suffers high strain hardening and bulges out in the form of a barrel. This demonstrates that the metal flows most easily towards the nearest free surface which is the point of least resistance. However, the use of lubricants reduces the degree of bulging and under the conditions of ideal lubrication, the bulging can be brought down to zero.

The main value of this paper is to contribute and fulfil the detailed the dependency of barrel radius on material type by upsetting of specimen of various materials using different lubricants that are being studied so far in the literature.

The purpose of this paper is to provide an axisymmetric model of tube hydroforming using a Fourier Series based finite element method.

Fourier series interpolation function, which considerably reduces the size of the global stiffness matrix and the number of variables, is employed to approximate displacements. The material of the tube is assumed to be elastic‐plastic and to satisfy the plasticity model that takes into account the rate independent work hardening and normal anisotropy. Numerical solution obtained from an updated Lagrangian formulation of the general shell theory is employed. The axial displacement stroke (a.k.a. axial feed) during tube hydroforming is incorporated using Lagrange multipliers. Contact constraints and boundary friction condition are introduced into the formulation based on the penalty function, which imposes the constraints directly into the tangent stiffness matrix. A forming limit curve based on shear instability and experimental measurements are used as fracture criteria.

The results obtained from this new formulation are compared against the nonlinear finite element code ABAQUS and experimental measurements for isotropic and transversely anisotropic tube materials. The hoop and axial strains predicted with AXHD code compared excellently with those from ABAQUS FEM code using plane stress axisymmetric (SAX1) and four‐node shell (S4R) elements. However, in the case of aluminum, the numerically predicted maximum hoop strain underestimated the actual hoop strain measured from the tube bulging experiment.

The axisymmetric hydroforming program (AXHD) developed in this work is very efficient in simulating the free‐forming stage of the tube hydroforming process under simultaneous action of internal pressurization and displacement stroke.

Although Fourier Series based finite element method has been used in metal forming, the extended application presented in this paper is novel in the finite element analysis of tube hydroforming.

A technique for computing free surfaces by a steady state approach has been included in the hot rolling code ROLL3. It has been described in a previous paper, along with applications to some simple rolling passes. In the present text, new developments are included to deal with more complex geometries, in particular when several potentially free surfaces exist. The problem of contact with flanks of grooves is given special care. Application to dog bone formation and flattening is presented. Then a case with two free surfaces is computed and compared to experiments. An application is then performed to beam roughing passes.