Papers by Keyword: Preform

Abstract: Textile reinforcements have outstanding load-bearing capabilities due to the excellent tensile properties of high performance multifilament yarns (e.g. carbon fibers). However, in order to take full advantage of their high potential, it is necessary to ensure that the filaments run in a straight line. In order to guarantee this straight filament course, the highly efficient multiaxial warp knitting process is used for the production of 2D non-crimp fabrics (NCF) as textile preforms. In various industrial applications, most structures have complex 3D geometries. Therefore, the 2D textile needs to be shaped for reinforcement, which often results in a rearrangement of the filament orientation. Consequently, the 3D shaping process has to be taken into account during the textile production or in the shaping process itself in order to guarantee the highest mechanical properties. Using the example of lattice girders for concrete reinforcement, a new approach for the fabrication of 3D textile lattice girders in a continous shaping process is presented. The results of the production tests of the developed technology approach show no apparent filament damage and exact roving orientation with no inadvertent deflection, compression or bulging, indicating a precise and gentle shaping process. The developed technology contributes to the future reduction of the production costs of 3D textile reinforcements.

Abstract: High volume fraction SiC/Al composite material, with its excellent thermal properties and flexible preparation process, has been widely used in the field of electronic packaging. In the paprer, the development of SiC/Al materials for electronic packaging and their preparation methods are reviewed. The preparation processes for preparing SiC/Al by liquid infiltration are mainly introduced. The advantages and disadvantages of several important processes are analyzed. Finally, the development trend of SiC/Al for electronic packaging prepared by liquid infiltration is prospected.

Abstract: There is a growing demand for more efficient and economic manufacturing process to improve product quality, reduce production cost, reduce lead time and increase productivity. The application of computer aided design and manufacturing (CAD/CAM) techniques to forging is becoming increasingly popular as the resulting improvements in yield and productivity. Modeling and simulation have become a major concern in recent and advanced research. In this paper die design for forging of an automobile component “Stub Axle” is presented. In die forging process, complex shape component cannot be made in one stage and therefore, the use of preform die becomes essential. The initial preform design was carried out by conventional method. The simulation has been carried out using software DEFORM-3D. The main goal of this study is to design an optimal preform shape resulting an optimal initial billet selection. Keywords:CAD/CAM, Preform, DEFORM-3D, Simulation, Forging

Abstract: The wall thickness of plastic bottle is a major consideration for engineers in designing products with strength. For injection blow molding, the thickness depends on the preform size, and shape of the required product. The polyethylene terephthalate (PET) is injected in a mold with the shape of the preform. A stretch injection blow molding machine is used for processing the preform to the shape of the bottle. This research applied finite-element analysis for the process simulation; started from applying the air pressure inside the heated perform – until the PET expanded to the required bottle shape. While most studies were interested in axis-symmetry shape, this paper concentrated on a bottle with uniform flat wall thickness on four sides of a squared section bottle. Several finite-element models were studied and compared the simulation efficiency. Under the investigated area of ±15 mm x 90 mm, the thickness deviation found to be within 3.573%.

Abstract: This study aims to reduce brake pad thickness and density variations by pressure equalization in the preforming process. Brake pads consist of fillers, lubricants, abrasives, reinforcing fibers, and binders. These are compacted together as raw materials. Each component is responsible for a different specific property to help the brake pad reduce the speed of the vehicle. The forming of a brake pad begins with compression of friction powder in a rigid mold with a complicated contour. It is then compacted by vertically pressing punches to form a body of complicated shape and homogeneous density. The strength of the brake pad, which is a main property in the compacted material, primarily depends on the type of fiber reinforcing material. Since the ability of fiber to flow is poor due to its high internal friction and its random arrangement. These two characteristics cause non uniformity in density and elastic modulus. Pressure equalization is an adjustment of the filling depth of the powder which otherwise would have an uneven fill inf the cavity of the mold. The pressure equalization of the filled powder is shown to correlate with the brake pad dimensional accuracy and uniformity of density.

Abstract: Transverse compaction and in-plane shear deformartion are the dominative deformation mode for woven preform during forming process. A full finite element model of the 2.5D woven composites has been established by the computed tomography (CT) in this paper. Based on the energy method, the effective orthotropic/anisotropic stiffness coefficients C_ij are calculated by performing a finite element analysis (FEA) of this full cell model. Using this model, the effects of the compaction and shear deformation of the 2.5D woven preform on the composites stiffness are investigated in detail. Compared the results of the static tensile tests, the rationality of the model and the method is verified.

Abstract: Lead-foam is a type material holding high porosity and specific surface area and can be used as grid material of storage battery and anode material in zinc electrolysis. Based on the infiltration casting system designed according to Pascal's and pressure infiltration principle, lead-foam with porosity 58-61%, cell diameter 1.18-3.35mm was successfully manufactured via infiltration casting method where industrial sodium chloride (NaCl) particles were used as porogens. As preparation of preform is a key step in infiltration casting process, orthogonal tests were performed to study the some process parameters’ effects on the porosity of the preform and the orthogonal test results revealed that the rank from high to low of the parameters’ effects on the porosity of preform was porogen size, cold-compacting pressure, sintering time and sintering temperature.

Abstract: Taking the geometric configuration of complex-shape forging into account, the isothermal split-die forging method, which is one multi-way die forging technology and can be operated on the general hydraulic press, is employed. The temperatures of billed and dies are 420°C and 380°C in the isothermal forging process. The coupled thermo-mechanical finite element method (FEM) is used to analyze the forging process. FEM calculation results show several folds had been formed in the final forging process due to unreasonable geometric configuration of preform. The folds mechanism is that direction of velocities become cross on the surface of billet, and the folds can be avoided if the direction would be kept convex. And then the preform is redesigned. A set of isothermal precision forming equipment is designed and manufactured. The experimental results verify the selected process and preform configuration. And all of the hardness, dimensional accuracy and surface quality of the forgings obtained by the equipments satisfy the requirements.

Abstract: Mesoscopic simulations of the transverse compression of textile preforms are presented in this paper. They are based on 3D FE models of each yarn in contact with friction with its neighbours. The mesoscopic simulations can be used as virtual compression tests. In addition they determine the internal geometry of the reinforcement after compaction. The internal geometry can be used to compute the permeability of the deformed reinforcement and to calculate the homogenised mechanical properties of the final composite part. A hypoelastic model based on the fibre rotation depicts the mechanical behaviour of the yarn. The compression responses of several layer stacks with parallel or different orientations are computed. The numerical simulations show good agreement when compared to compaction experiments.

Abstract: This paper presents a series of injection process simulations for blow molding preforms by using MoldFlow. The injection-blowing system was used and this consists 3 stages on the same machine; (1) preform injection, (2) blowing and (3) ejection. The quality of preform injection process is an important factor that can dominate the whole process efficiency. The injection mold system consists of 10 cavities and a hot runner system. The hot runner system has 10 cavities and temperature of each cavity can be independently controlled. Through several filling analyses, suitable temperature of each gate was determined so that all cavities could be simultaneously filled. Weld lines on the bottom of preforms were predicted. This fact can be an important aspect because preforms will be blown. To improve cooling efficiency, ''Floody Cooling Type" channels were applied. Conventional cooling channels were straight-line types and then distances between cooling channels and cavities cannot be uniformed. Floody cooling type channels were uniformly placed around cavities as far as possible. To compare two different types of cooling channels, cooling tests of MoldFlow were carried out and certain advantages of floody cooling type channels were evaluated.