K. K. Tong’s research while affiliated with Singapore Institute of Manufacturing Technology (SIMTech) and other places

Flow forming, one of the rotary-forming processes, is used mainly to produce thin-walled high-precision tubular components. Due to its flexibility and low tool load requirement, the process has great potential to be extended to the forming of net-shape components for thin and intricate features from bulk raw materials, such as solid bar ingot, cast and forged performs. In the work reported in this paper, a flow-forming facility was established to investigate the feasibility of forming thin-walled cups from flat-disc blanks by investigating the effects of roller geometry, degree of material reduction and roller geometry on material flow. In addition, a 3D Finite Element (FE) model was developed to simulate the ‘bending’ process, based on the experimental conditions.The results showed that it is possible to adopt a two-step forming process, ‘bending’ and flow forming to enable material flow along the mandrel in order to form a thin-wall cup component using two different profiles and adopting an axial roller movement. Quality of the cups formed depends on the diameter reduction, starting disc thickness of the blank and the number of pass in the flow-forming stage. The results predicted by the FE simulation was compared with the experimental results and showed close agreement. This work illustrates the possibility of adopting flow-forming processes for the production of thin section, which would be difficult and expensive to produce by press forming. In addition, it also showed that although FEM is an effective tool to optimize process parameters, computational time remains as the main barrier for its prevalent usage especially for incremental processes such as flow forming and spinning processes.

In the current metal forming product development paradigm, the simultaneous and optimal design of product, process and forming system is a non-trivial issue as there are many affecting factors which interact and interplay each other. In the up-front design process, the systematic evaluation and verification of design solution is critical as this could shift the product development paradigm from traditionally trial-and-error and heuristic know-how to more scientific calculation, analysis and simulation. To ensure the efficient and accurate assessment and evaluation of design solution generation, state-of-the-art technologies need to be developed. In this paper, a methodology for systematic evaluation and verification of the simultaneous design of metal forming product, process, and forming system is presented. The factors which affect these designs are first articulated and how they interact and interplay are described. The importance of the systematic evaluation of designs is, thus, figured out. In addition, the role that CAE simulation plays in this process is explained. To evaluate the design, detailed evaluation criteria are developed and how the criteria are used through CAE simulation technology to reveal the behaviors and performances of designs is articulated. Through case studies, the developed technology is illustrated and its efficiency is finally verified.

This research project investigated the process conditions of using squeeze casting process to produce aluminium alloy preforms or billets for subsequent cold forging process. The comparative effects of heat treatments, their microstructures and mechanical properties were evaluated. Through these studies and experiments, the main emphasis is on the study of commercial material Al 6061, Al 2014 and Al 356 alloys. The formability of the alloys was carried out using forward and backward extrusion test at 50% area reduction at room temperature (cold extrusion). It was found that when wrought aluminium 6061, 2014 and 356 alloys were squeeze cast to form the preforms, the preform microstructures revealed very fine microstructures that are feasible to be cold extruded. In addition, after thermal annealing treatment of 6061 squeeze cast preforms, the samples showed a similar value of work hardening exponent value of 0.20 as compared to the wrought aluminium alloy 6061, with a workhardening exponent value of 0.21 obtained from the static compression test. Wrought aluminium alloys generally cost twice the amount as compared with casting ingots. The microstructures of the squeeze cast 6061 alloy showed no visible cracks or inclusions after the deformation by extrusion. The results of the studies showed that Al 6061 preforms via squeeze cast technique may be cold extruded or formed, which provide an alternative means for the production of billets for the cold extrusion or forging process.

Rolling is a process of reducing the thickness or changing the cross-section of a long work-piece by compressive forces applied through a set of rolls. It accounts for about 90% of all metals produced by metal working processes and is a conventional method to produce metal strip. This process involves several processing steps resulting in high production cost and interior productivity. A approach by casting-cum-rolling process has been developed in this paper. An apparatus has been built which consists of casing unit and melt delivery unit for this process. A forming belt and the two pinch rolls are utilized in the casting unit. An extended contacting point between forming belt and the lower pinch roll in this unit makes it possible to cast thin metal strips of alloys with wider freezing range. Tin alloy, aluminium alloys and magnesium alloys had been tested on the apparatus. The results showed that it was feasible to produce crack-free cast strips of tin alloy and aluminium alloys. However, crack region was found in magnesium strip, which possibly attributed to slow solidification rate and non-uniformity temperature and melt distribution. Effects of processing parameters on the surface roughness and strip thickness were studied too. It was found that the texture of cast strips on their roll sides was less affected by the processing parameters. Their surface roughness was inherited from the roll surface condition. The strips' texture on their belt side, however, was closely dependent on the processing parameters. The average cast strip thickness made of tin, aluminium and magnesium alloy is 0.31 mm, 0.95 mm and 1.17 mm, respectively.

In the current metal forming product development paradigm, product cost, time-to-market and product quality are three overriding issues, which determine the competitiveness of the developed products. In the up front design process, the first 20% of design activities commits to about 80% of product development cost and product quality issues. How to conduct ‘right the first time’ design is critical to ensure low development cost, high product quality and short time-to-market. To address these issues, state of the art technologies are needed. Traditionally, computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies provide solutions for representation of design intent and realization of design solution physically. However, it is difficult to address some critical issues in the design of forming process, tooling structure, material selection and properties configuration, and finally the product quality control and assurance. Computer-aided engineering (CAE) technology fills this gap as it helps practitioners generate, verify, validate and optimize design solutions before they are practically implemented and physically realized. In this paper, a methodology for evaluation of metal forming system design and performance via CAE simulation is developed. The concept of metal forming system and its design is first articulated and how the CAE technology helps design and design solution evaluation is then presented. To assess and evaluate the performance of metal forming systems, quantitative design evaluation criteria are developed. Through industrial case study, how the developed methodology helps metal forming system design and evaluation is illustrated and its efficiency and validity is finally verified.

Die performance and its service life are a non-trivial issue in metal-forming industry due to three overriding issues in this industry cluster: productivity, cost and quality are mainly dependent on it. Many factors in die life cycle from design and fabrication to downstream service all affect die performance and its service life. These factors could include die design and structure, material properties, dies manufacturing and metal-forming processes, and die service conditions. The issue about how to develop an efficient and practical methodology for die life assessment and improvement has not yet been fully addressed despite the fact that dies have been used in industry for many decades. In this paper, the metal fatigue theory and FEM technique are used as the basis for the development of a methodology for die fatigue life analysis and improvement. The stress–life or S-N approach is used for die fatigue analysis. To explore extensively and reveal the dynamic die stress state panorama during the forming loading cycle, a CAE-based approach is deployed for stress analysis. Based on the S-N approach and CAE analysis, a CAE-enabled methodology is then orchestrated and finally implemented in this research. Using an industrial part as a case study, the validity, robustness and efficiency of the developed methodology are verified. The methodology can provide a satisfactory solution for die life assessment and improvement in metal-forming industry.

In the current metal forming product development paradigm, the first 20% of design ac- tivities commits to about 80% of product development cost and product quality issues. Knowing how to efficiently generate the optimal design solution in up-front design processes is crucial for "right the first time design". To address these issues, state-of-the-art technologies are needed. Traditional heuristic know-how and expertise cannot accurately evaluate the design solutions in metal formed product devel- opment and it needs more scientific calculation and analysis. Computer-Aided Engineering (CAE) tech- nology provides approaches for practitioners to gen- erate, verify, validate and optimise the design solu- tions before they are physically realised. In this paper, how CAE simulation supports design solution gen- eration for metal-formed part design, process deter- mination, tooling design, product quality assurance and die fatigue life design is presented. The related processes, procedure and methodologies for solution generation are proposed and presented. Using indus- trial parts as case studies, how CAE simulation sup- ports design solutions generation for metal forming product development is illustrated and demonstrated.

The die life of the cold forging tools are largely determined by the principle stress states and its distribution. A large majority of cold forging tools and dies failed as a result of fatique, i.e. cracking under a cyclic loading. Reliable predictions of the die life under a forging load is important, since it will affect such as the down time of the tools, production cost and unit part cost. In order to control the die failures and predicting the die life of forging tools, a predictive and improvement methods are used to increase the die life in cold forging. In this study, a proposed method to predict die life in cold forging using finite element solutions and experimental results obtained from fatique testing were suggested. Increasing the pre-stress reinforcement pressure on the outer surface of the die insert was one of the improvements made to stress distribution resulting in a better die life performance.

Components with complicated geometries that are conventionally made by complex, time-consuming and expensive processes such as machining and electron-beam welding can be produced as near net shape parts using metal injection moulding, then completed by shrink-fit or adhesive bonding at the sintering stage. This was the route taken by a team at the Singapore Institute of Manufacturing Technology.

Die performance and its service life is a non-trivial issue in metal forming industry as many factors in die life cycle from design, fabri- cation, to downstream service, all affect it. In this report, a simulation-based approach for die life estimation and improvement is developed by employing the FEM technology and metal fa- tigue theory. Using industrial part as case study, the validity, robustness and efficiency of the de- veloped approach is tested and verified. The approach is proven to be able to provide satis- factory solution for die life assessment and im- provement in metal forming industry.