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Featured researches published by Yanle Li.


Materials and Manufacturing Processes | 2013

Vertical Wall Formation and Material Flow Control for Incremental Sheet Forming by Revisiting Multistage Deformation Path Strategies

Zhaobing Liu; Yanle Li; Paul A. Meehan

In this article, multistage deformation path strategies for single point incremental forming (SPIF) are revisited with the purpose of controlling material flow (improving sheet thickness distribution) and forming a vertical wall surface for cylindrical cups. It is noted that stretching and thinning are two main deformation modes during SPIF. How to control material flow in an optimal way is a key point for successful forming. Multistage incremental forming shows more advantages than single-stage forming, especially dealing with shapes with steep walls. In this study, three basic multistage deformation path strategies have been proposed, that is: A. incremental part diameter; B. incremental draw angle; and C. incremental part height and draw angle. Those strategies and their combinations have been evaluated in terms of formability and compared in order to understand the material allocation mechanism and optimize the multistage forming process. In addition, approximate plane-strain analysis models have been given to provide formability predictions between single-stage and multistage strategies, and between strategies B and C, respectively. The prediction results show good agreement with the experimental results. It is demonstrated that the strategic combination A + B is the optimal way to achieve the forming target.


Materials and Manufacturing Processes | 2014

Modeling and Optimization of Surface Roughness in Incremental Sheet Forming using a Multi-objective Function

Zhaobing Liu; Sheng Liu; Yanle Li; Paul A. Meehan

As a critical product quality constraint, surface roughness is regarded as a weak point in incremental sheet forming (ISF). It is of great importance to identify the impact of forming parameters on the surface roughness and optimize the surface finish at the production stage. This paper proposes a systematic approach to modeling and optimizing surface roughness in ISF. The quantitative effects of four parameters (step down, feed rate, sheet thickness, and tool diameter) on surface roughness are analyzed using the response surface methodology with Box–Behnken design. The multi-objective function is used to evaluate the overall surface roughness in terms of the tool-sheet contact surface roughness, i.e., internal surface roughness and the noncontact surface roughness, i.e., external surface roughness. Additionally, the average surface roughness (R a) on each surface is measured along the tool-path step-down direction taking the impact of sheet roll marks into account. The optimal conditions for the minimization of overall surface roughness are determined as step down (0.39 mm), feed rate (6000 mm/min), sheet thickness (1.60 mm), and tool diameter (25 mm). This study shows that Box–Behnken design with a multi-objective function can be efficiently applied for modeling and optimization of the overall surface roughness in ISF.


Materials and Manufacturing Processes | 2014

Simulation and Experimental Observations of Effect of Different Contact Interfaces on the Incremental Sheet Forming Process

Yanle Li; Zhaobing Liu; W.J.T. Daniel; Paul A. Meehan

Incremental sheet forming (ISF) is a promising forming process perfectly suitable for manufacturing customized products with large plastic deformation by using a simple moving tool. Up to now, however, the effects of contact conditions at the sheet interface are not well understood. The aim of this work is to study the effect of tool type and size on the formability and surface integrity during the forming process. Experimental tests were carried out on aluminum sheets of 7075-O to create a straight groove with four different tools (ϕ 30,ϕ25.4,ϕ20 andϕ10mm). One tool tip was fitted with a roller ball (ϕ 25.4mm) while the other three were sliding tips. The contact force, friction and failure depth were evaluated. A finite element (FE) model of the process was set up in an explicit code LS-DYNA and the strain behavior and thickness distribution with different tools were evaluated and compared with the experimental results. This study provides important insights into the relatively high formability observed in the ISF process. Microscopic observations of the surface topography revealed that a rolling tool tip produced better surface integrity as compared with a sliding tool tip, wherein, distinct scratch patterns in the tool traverse direction were evident.


Advanced Materials Research | 2014

Experimental Study and Efficient Prediction on Forming Forces in Incremental Sheet Forming

Yanle Li; Zhao Bing Liu; Haibo Lu; W.J.T. Bill Daniel; Paul A. Meehan

Incremental sheet forming (ISF) is a promising forming process in which complex 3D shapes are formed from a sheet of metal using a simple moving tool. The efficient prediction of contact forces in ISF is desirable to monitor the forming process, prevent failure, and implement on-line control and process optimization. However, traditional Finite Element (FE) simulation used for force prediction is significantly time-consuming for complex products. The purpose of this study is to investigate the ISF force prediction and characteristics under different forming conditions and build a potential efficient model. In the present work, forces during the cone forming process with different wall angles and step down sizes were recorded and compared. Different force trends were identified and discussed with reference to bending and strain hardening mechanics. Influences of different parameters on designated formability were also qualified which should benefit the product design process. An efficient predictive model based on upper-bound approach was applied for force prediction in this case. Predicted tangential forces were then compared with the experimental results showing relatively good agreement. The limits of the proposed model were also identified and the potential of future improvements were suggested.


Carbohydrate Polymers | 2018

A new biodegradable sisal fiber–starch packing composite with nest structure

Qi Xie; Fangyi Li; Jianfeng Li; Liming Wang; Yanle Li; Chuan-wei Zhang; Jie Xu; Shuai Chen

A new completely biodegradable sisal fiber-starch packing composite was proposed. The effects of fiber content and alkaline treatment on the cushioning property of the composites were studied from energy absorption efficiency, cellular microstructure and compatibility between fiber and starch. With increasing fiber content, the nest structure of composites becomes dense first and then loosens, resulting in initial enhancement and subsequent weakening of the cushioning property of the composites. The composite with 4:13 mass ratio of fiber and thermoplastic starch (TPS) exhibit the optimal cushioning property. Alkaline treatment increases the compatibility between sisal fiber and TPS, promotes the formation of dense nest structure, thereby enhances the cushioning property of the composites. After biodegradability tests for 28 days, the weight loss of the composites was 62.36%. Its found that the composites are a promising replacement for expandable polystyrene (EPS) as packing material, especially under large compression load (0.7-6 MPa).


Materials Science Forum | 2013

Taguchi optimization of process parameters for forming time in incremental sheet forming process

Zhao Bing Liu; Yanle Li; W.J.T. Bill Daniel; Paul A. Meehan

ncremental sheet forming (ISF) is a new promising technology due to its flexibility and low-cost tooling properties compared with conventional forming processes. However, it is only suitable for small-batch production because of its incremental feature inducing relative long forming time. Presently, widespread usage of the process is restricted by a lack of predictive understanding of the process due to its complexity. In this paper, the aspect of forming time is studied by investigating the effects of four distinctive process parameters (step over, feed rate, sheet thickness and tool diameter). An effective analysis tool, Taguchi method together with design of experiment (DOE) and analysis of variance (ANVOA) is utilized to study the effects of the four process parameters on forming time and further to optimize parameter combinations in order to minimize forming time. Using these techniques, experimental results show that the step over of spiral tool path is the most important process parameter affecting forming time followed by feed rate. Sheet thickness and tool diameter have little effect on forming time. The comparison between the prediction of optimized parameter combination and the confirmation test result has further demonstrated the effectiveness of the proposed method. It is worth noting that the results of this study will indicate a further direction on how to optimize process parameters to find a balance between forming efficiency (forming time) and forming quality (forming accuracy and surface roughness).


Advanced Materials Research | 2014

Study on Step Depth for Part Accuracy Improvement in Incremental Sheet Forming Process

Haibo Lu; Yanle Li; Zhao Bing Liu; Sheng Liu; Paul A. Meehan

Incremental Sheet Forming (ISF) is a new-emerging sheet forming process well suited for small batch production or prototyping because it does not need any dedicated dies or punches. In this forming process, sheet metal parts are formed by a smooth-end tool in a stepwise way, during which plastic deformation is highly localized around the tool end. The part geometric accuracy obtained in the current ISF process, however, has not met the industry specification for precise part fabrication. This paper deals with a study on step depth, a critical parameter in ISF, for improving the geometric accuracy, surface quality and formability. Two sets of experiments were conducted to investigate the influence of step depth on part quality. Dimensional accuracy, surface morphology and material fracture of deformed parts were compared and analysed. An optimum value of step depth was suggested for forming a truncated cone. The present work provided significant fundamental information for the development of an advanced ISF control system on tool path control and optimization.


Materials Science Forum | 2016

A Brief Review of Forming Forces in Incremental Sheet Forming

Yanle Li; Jie Sun; Jianfeng Li

Investigation of forming forces in incremental sheet forming (ISF) is of great importance since it provides understanding of the deformation mechanics, monitoring of the forming process, failure prediction, and future means of on-line control and optimization. This paper provides a review of studies on the contact conditions and the effects of the process parameters on forming forces in ISF, followed by the current status on forming force prediction and its potential role in the improvement of ISF technology.


Advanced Materials Research | 2014

An Analytical Model for Deformation Path Design in Multistage Incremental Sheet Forming Process

Zhao Bing Liu; Yanle Li; W.J.T. Bill Daniel; Paul A. Meehan

Incremental sheet forming (ISF) is a new promising technology due to its flexibility and low-cost tooling properties compared with conventional forming processes. However, a common technical problem encountered in ISF is non-uniform thickness variation of formed parts, particularly excessive thinning on severely sloped regions, which may lead to the part fracture and limit the process formability. Design of multistage deformation paths (intermediate shapes or preforms) before the final part is a desirable and practical way to control the material flow in order to obtain more uniform thickness distribution and avoid forming failure. Based on the shear deformation and the strain compensation idea, an analytical model for designing multistage deformation paths and predicting the thickness strain distribution is proposed. The feasibility of the proposed model is validated by the finite element analysis (FEA) and experimental tests in terms of the comparison of prediction, simulation and experimental results on the thickness strain distribution and the process formability.


Journal of Materials Processing Technology | 2015

Deformation mechanics and efficient force prediction in single point incremental forming

Yanle Li; W.J.T. Daniel; Zhaobing Liu; Haibo Lu; Paul A. Meehan

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Paul A. Meehan

University of Queensland

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Zhaobing Liu

University of Queensland

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W.J.T. Daniel

University of Queensland

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Haibo Lu

University of Queensland

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Sheng Liu

University of Queensland

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Zhao Bing Liu

University of Queensland

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