Preform Design Research Articles

Design, fabrication, and optical gain performance of the gain-guided and index-antiguided Nd^3+-doped phosphate glass fiber

Design, fabrication, and optical gain performance of the gain-guided and index-antiguided (GG-IAG) fiber are studied systematically in this work. The main parameters of the GG-IAG fiber, i.e., a, Δn, g, and η, are designed by single-mode operation theories, followed by a detailed study of the fabrication of the GG-IAG fiber, including preform design and fabrication, fiber-drawing conditions, and so on. GG-IAG fibers with different core diameters (100–380 μm) are obtained and their corresponding performance is measured. In order to verify whether the parameters of the fabricated GG-IAG fiber meet the theoretical design, the laser amplifier experiments of the GG-IAG fiber and the fabricated gain-guided and index-guided (GG-IG) fiber are both demonstrated. The experimental results show that the net optical gain coefficient of the GG-IG fiber is the sum of the net optical gain coefficient and the leakage loss coefficient of the GG-IAG fiber, which indicates that the fabricated GG-IAG fiber parameters and performance are consistent with the theoretical design. This work should help further exploration of the GG-IAG fiber.

A new criterion for preform design of H-shaped hot die forging based on shape complexity factor

In this paper, a new criterion is proposed in order to determine the necessity of preform steps for axisymmetric H-shaped parts in multi-stage hot forging based on shape complexity factor. The proposed geometrical based criterion was implemented in several examples using finite element method and experimental tests to verify the presented criterion. Finally, in comparison with the existing criteria, results show that the proposed criterion is in excellent agreement with experimental results in order to estimate the optimum number of preform steps.

Thickness control in a new flexible hybrid incremental sheet forming process

Incremental sheet forming is a cost-effective process for rapid manufacturing of sheet metal products. However, incremental sheet forming also has some limitations such as severe sheet thinning and long processing time. These limitations hamper the forming part quality and production efficiency, thus restricting the incremental sheet forming application in industrial practice. To overcome the problem of sheet thinning, a variety of processes, such as multi-step incremental sheet forming, have been proposed to improve the material flow and thickness distribution. In this work, a new process has been developed by introducing multi-point forming as preforming step before conducting incremental sheet forming processing. Employing an established hybrid sheet forming system and the corresponding thickness prediction model, the preform shape can be optimized by employing a two-step optimization approach to improve the sheet thickness distribution. In total, two case study examples, including a hemisphere part and an aerospace cowling part, are fabricated using the developed hybrid flexible process in this study. The experimental results show that the hybrid flexible forming process with the optimal preform design could achieve sheet parts with more uniform thickness distribution and reduced forming time.

A new technology for production of high thickness carbon/carbon composites for launchers application

Carbon–Carbon (C/C) composites are known for their extraordinary stability and excellent mechanical properties, almost unchanged at high temperatures. Among the several advanced applications, C/C based materials can be used in engines as nozzle throat section for launchers. In particular, the main feature for such employment is the material high resistance in extreme thermal environment. On the other hand, large-size items are required for this kind of purposes, thus introducing criticalities in terms of material uniformity and final overall properties. Up to now, there no standard for the production of high thickness C/C structures. In this paper a novel manufacturing method is analyzed, following each phase of the process, from the carbon fiber preform design and preparation to the carbon densification by chemical vapor infiltration method. Five preforms of large dimensions with different characteristics have been manufactured and infiltrated. The realized prototypes have been then analyzed by means of mechanical, physical and morphological tests. Aim of the results of this preliminary work is to establish a set of guidelines for a well-defined high thickness C/C production method.

Nonisothermal glass molding for the cost-efficient production of precision freeform optics

Glass molding has become a key replication-based technology to satisfy intensively growing demands of complex precision optics in the today’s photonic market. However, the state-of-the-art replicative technologies are still limited, mainly due to their insufficiency to meet the requirements of mass production. This paper introduces a newly developed nonisothermal glass molding in which a complex-shaped optic is produced in a very short process cycle. The innovative molding technology promises a cost-efficient production because of increased mold lifetime, less energy consumption, and high throughput from a fast process chain. At the early stage of the process development, the research focuses on an integration of finite element simulation into the process chain to reduce time and labor-intensive cost. By virtue of numerical modeling, defects including chill ripples and glass sticking in the nonisothermal molding process can be predicted and the consequent effects are avoided. In addition, the influences of process parameters and glass preforms on the surface quality, form accuracy, and residual stress are discussed. A series of experiments was carried out to validate the simulation results. The successful modeling, therefore, provides a systematic strategy for glass preform design, mold compensation, and optimization of the process parameters. In conclusion, the integration of simulation into the entire nonisothermal glass molding process chain will significantly increase the manufacturing efficiency as well as reduce the time-to-market for the mass production of complex precision yet low-cost glass optics.

Microstructural design and additive manufacturing and characterization of 3D orthogonal short carbon fiber/acrylonitrile-butadiene-styrene preform and composite

In contrast to conventional preforming techniques, additive manufacturing features direct and layer-by-layer fabrication, which provides viable new capabilities for the fabrication of reinforced composites. In this article, we explore the microstructural design as well as additive manufacturing and characterization of 3D orthogonal, short carbon fiber/acrylonitrile-butadiene-styrene (ABS) preforms and composite. First, an array of 3D orthogonal preforms is designed based on topological consideration and validated by fused filament fabrication of pure ABS wire; high fidelity between models and preforms is accomplished. Then, short carbon fibers are introduced into the designed 3D orthogonal preforms as reinforcement, using a short carbon fiber/ABS wire. Lastly, the compressive behavior of a 3D orthogonal, short carbon fiber/ABS preform and that of its silicone infused composite are characterized. The preform design methodology developed in this research as well as the preliminary effort made in composite fabrication and characterization demonstrates the feasibility of additive manufacturing of 3D orthogonal preform based fiber composites.

Topology-based preform design optimization for blade forging

Preform design plays a significant role in forging design especially for parts with complex shapes. Conventional preform design approaches include trial-and-error approach, electric field method, and shape optimization-based approaches. In this paper, by introducing the structural design optimization concept, a 3D topological preform design optimization method has been developed. In this method, a new criterion for element elimination and addition is proposed and employed for plastic deformation problems in blade forging. Based on the finite element (FE) simulation combined with optimization, the optimized preforms with and without equal cross-section constraint can be obtained. Using the optimized preform, physical experiment on forging of a blade has been implemented to validate the optimization result. Other preform-related issues, such as the feasible approaches for preparation of optimized preforms, are also discussed in detail. The result suggested that the optimized preforms could improve the deformation uniformity during forging processes with better die-filling rate and reduced waste of raw materials.

Cross dies forging: A new method to reduce forging force & price up to 80% thanks to FEM method

Purpose of this article was to introduce a new method of forging which is called Die Forging. In this method, the required force (load) is reduced to the greatest possible degree through elimination of flash channel; however, this would also decrease the positive effect of flash channel, namely filling the gaps and pores within the mold. Cross die forging procedure provides a way for providing a better preform design which ensures that the mold is filled without allowing the material to enter the flash channel. This method has been invented based on the need to decrease the production costs and to use lower tonnage pressing devices for production of heavy parts. This method is an economical method only for parts that: A) Has at least one plane of symmetry and the two ends that are perpendicular to the symmetry plane are flat; B) Has a weight that makes it impossible to be manufactured by rolling or roll forging processes. Examples of such parts are valve's body, T-junctions, etc.

Case study on the influence of kinematic hardening within a parameter-free and non-invasive form finding approach

Inverse form finding – as a type of shape optimization – aims in determining the optimal preform design of a workpiece for a specific forming process, whereby the desired target geometry is known. Recently, a novel parameter-free and heuristic approach was developed to tackle this nonlinear optimization problem. Benchmark tests already delivered promising results. As a particular note-worthy feature of the approach, a coupling to an arbitrary finite element software is feasible in a non-invasive fashion. The aim of this contribution is to investigate the effect of kinematic hardening and cyclic loading on the convergence behavior of the algorithm.

Pre-form design for hydro-forming of aluminum alloy automotive cross members

Due to the requirement of lightweight in the automotive industry, aluminum alloy components with irregular cross sections have been used for body-in-white parts. In order to obtain an aluminum alloy cross member with uniform thickness distribution and acceptable dimension accuracy, a hydro-forming process of a 6063-T4 aluminum alloy cross member was studied by experimental research and numerical simulation. To avoid severe thinning and bursting during hydro-forming, the design of experiments according to a central composite design method was carried out, and the significance of pre-form structural parameters was discussed on thinning. According to the optimum pre-form shape, experimental researches were then conducted on thickness distribution of typical sectional profiles and dimension accuracy. It is shown that the maximum thinning is 14 %, which is located on sectional profile B-B. The deviation of circumferential dimension accuracy along the axial direction is 0.33 %. The maximum dimensional deviation at sectional profiles A-A and B-B is 0.19 and 0.22 mm, respectively; accordingly, the dimension accuracy along the width direction is 0.4 and 0.31 %, respectively. Finally, a sound hydro-formed cross member is obtained.

Optimization of pre-form shapes by response surface methodology for hydro-forming of 780 MPa torsion beam

With the increasing use of advanced high strength steel for automotive components, hydro-formed hollow components have the advantage of both high strength and high stiffness. In order to manufacture a 780 MPa torsion beam satisfied with both improved safety and lightweight, hydro-forming process of 780 MPa torsion beam was studied by experimental research and numerical simulation. Pre-form design according to central composite method was carried out to avoid forming flash and bursting during hydro-forming. Response surface model of the effect of pre-form structure on thickness distribution was developed, and significance of structural parameters on the response value was discussed. According to the genetic algorithm, an optimum pre-form shape has been obtained. An experiment was carried out on the basis of the optimum pre-form shape, and the effect of loading paths was deeply discussed on hydro-forming process. It is shown that the axial feeding within acceptable range can significantly improve the thickness distribution and forming accuracy. Finally, a well hydro-formed torsion beam is manufactured.

A review of carbon–carbon composites for engineering applications

Five kinds of carbon–carbon composites used in aerospace, aircraft, photovoltaics, powder metallurgy and high temperature furnaces are reviewed, whose preforms were fabricated by needle piercing, orthogonal three-direction weaving, radial weaving, axial weaving and puncture. The physical, mechanical, thermal, ablation, and wear properties and service life were compared with corresponding materials from overseas manufacturers. Correlations between the performance, type of preform and carbon matrix, and interfacial bonding state was obtained. These analyses and comparisons can lay a foundation for the construction of a database-sharing platform for C/C composites in engineering applications. Research efforts need to be focused on the fine structure and gradient design of preforms and the optimum combination of different carbon matrices for the improvement of C/C composites. [New Carbon Materials 2015, 30(2): 106–114]

Pre-form design for hydro-forming process of combined ellipsoidal shells by response surface methodology

In order to obtain a reasonable pre-form shell design for the needed sound ellipsoidal shell, a research has been conducted on variation of axis lengths during hydro-forming process of the combined ellipsoidal shell with double generating lines. Numerical simulation was carried out for parametric study of the pre-form shells with different structural parameters according to the Box-Behnken design method, and a mathematical response model between axis lengths and structural parameters was developed by multivariate quadratic regression analysis. Experiments were then carried out for hydro-forming process of the combined ellipsoidal shells with double generating lines. The deformation of the shell shape was separately reported, and the variation of axis lengths was recorded. Subsequently, comparative analysis of axis lengths between experimental data and predicted data coming from mathematical response model was deeply discussed. The comparison results show that the variation of axis lengths can be well predicted by the mathematical response model, which indicates that the needed ellipsoidal shell can be easily obtained by the optimization design of pre-form shell.

Preform design of hybrid-forming process to make sheet metal IT products with a sharp edge

Existing forging processes have limitations in forming products with sharp edges. Therefore, a new hybrid-forming process that combines drawing and forging processes was designed to form a sharp-edged product. First, a corner radius of a preform design was arranged to be smaller than the minimum bent area corner radius formed in general drawing processes. Then, the shape of the preform was planned to have the exact shape of the final product. Given that forming loads are a limiting condition in forging processes, they were set as an evaluation criterion to determine design requirements for final product shapes and the shapes of preforms. The reliability of finite element analysis results was verified by comparing analysis and experiment results, and a multistage preforming process was implemented to satisfy the determined evaluation criterion. This study demonstrates that IT products with sharp edges can be formed.

Unequal thickness billet design for large-scale titanium alloy rib-web components under isothermal closed-die forging

The under-filling defect is prone to occur in the forging of large-scale titanium alloy rib-web components (LTRC). A rigorous preform design with accurate volume distribution is required for a desirable LTRC. The unequal thickness billet (UTB) design divides the preform into multiple regions of varying thickness and can not only adjust the volume distribution effectively but also control forming defects with low cost and high efficiency. The purpose of this paper is to attain LTRC without any under-filling defects using the UTB methodology. Firstly, cross sections are extracted from a desirable LTRC so as to create the initial UTB according to the calculated neutral layer of material flow between ribs. Then a finite element (FE) model is established, using the Deform-3D software for the isothermal closed-die forging to study the material flow and die cavity filling. Finally, three schemes to modify the initial UTB are proposed for those areas where there is under-filling: (I) increase the number of regions in affected areas, (II) adjust the size parameters of the regions around affected areas, and (III) increase the thickness of the regions in affected areas. In conclusion, it is found that scheme I and scheme II are based on the constancy of volume principle and can be adopted if the distribution of the ribs on those affected areas is quite simple. However, scheme I increases the complexity of the UTB, so scheme II is preferred. Alternatively, if the distribution of ribs on those regions is more complicated, scheme III can be adopted. Although the volume of the UTB is increased slightly, all ribs can be completely filled, allowing the most accurate LTRC to be produced.

Application of Ant Colony Algorithm in Optimal Preform Design of Forging Process

For the forging with complex shape, the preform design is a difficult problem in the process and die design. It has an enormous influence on the quality of the forging. In this paper, combining with the FEM, the Ant Colony Algorithm was used for the preform optimization design. The general Ant Colony Algorithm was improved to fit for the multivariate continuous function optimization. The preform die shape was represented by B-spline and the coordinates of the control point of the B-spline were taken as the optimization design variables. The optimization program was developed. Finally, aimed to decrease the material cost of the forging, the preform optimization of a typical H-section forging was obtained using the self-developed program. The optimization results show that the improved Ant Colony Algorithm is suitable for the preform optimization design of forging.

Design and optimization of turbine blade preform forging using RSM and NSGA II

Forging is one of the production methods of turbine blades. But, because of the complexities of the blades, they cannot be produced in one stage and using preforms is necessary. In this paper, an extruded elliptical cross section was considered as blade preform, then response surface method and multi-objective genetic algorithm was used to optimize this preform. Maximum filling ratio of the final die and minimum flash volume, forging force and strain variance of final blade were considered as objectives of optimization. Design Expert software was used for design of experiment and optimization. Also Deform-3D software was applied to simulate the forging process. The optimized preform was compared with the preform resulted from conventional preform designing method. Results show that optimization method gives better results than conventional method. Also physical modeling was used for verification of simulation results. Results show simulation results have a good corresponding with experimental results.

Preform design in forging process of complex parts by using quasi-equipotential field and response surface methods

The preform design is the key to bulk metal forming. An approach to optimize 3D preform shape in multi-stepdieforgingbasedonquasi-equipotentialfieldmeth- od and response surface method is employed. Firstly, opti- mum preforging shape is determined by means of quasi- equipotential field method and response surface optimization. Secondly, longitudinal and cross-section curve methods are introduced to design advisable blocking blank based on the optimized preforging shape. Using the method, the optimized preforging shape is determined in the hot forging of the pendulum mass. Based on the optimized preforging shape, the advisable blocking blank is constructed. The final preform design, including the advisable blocking blank and preforging shape, is completed. The desired pendulum mass forging without any defects and with smaller flash is obtained.

3 차원 프린팅 기술의 열간 체적 성형 공정 적용에 관한 기초 연구 - 예비형상 설계 예 및 열간 금형강으로 적층된 표면 특성 분석

【The goal of this paper is to investigate preliminary the applicability of 3D printing technologies for the development of the hot bulk forming process and die. 3D printing technology based on the plastic material was applied to the preform design of the hot forging process. Plastic hot forging dies were fabricated by Polyjet process for the physical simulation of the workpiece deformation. The feasibility of application of Laser-aided Direct Metal Rapid Tooling (DMT) process to the fabrication of the hot bulk metal forming die was investigated. The SKD61 hot-working tool steel was deposited on the heat treated SKD61 using the DMT process. Fundamental characteristics of SKD 61 hot-working tool steel deposited specimen were examined via hardness and wear experiments as well as the observation of the morphology. Using the results of the examination of fundamental characteristics, the applicability of the DMT process to manufacture hot bulk forming die was discussed.】

Cold Forging Die Design and Process Simulation of a Disk with Inner Ring Gear

Cold forging die design and process simulation were studied in this paper for a disk with center boss and outer ring gear. The complexity of part geometry results in defects of under-filling and folding. The material flow interference in the radial and the axial directions at the corner areas is the main reason of the occurrence of defects. A multi-stage cold forging process was proposed to control the material flow and volume distribution simultaneously. FEM simulations were carried out to evaluate the designs of process and die. The proposed preform and web geometry designs were able to decrease the forging load and control the material flow. The simulation results showed the proposed methods were able to make this forged part without defects.