Advances in Manufacturing

Characterization of process and machine dynamics on the precision replication of microlens arrays using microinjection moulding

Hao-Yang Zhang, Nan Zhang, Wei Han, Hong-Gang Zhang, Michael D. Gilchrist, Feng-Zhou Fang

2021, 9(3): 319-341. doi:10.1007/s40436-020-00341-y

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Injection moulding has shown its advantages and prevalence in the production of plastic optical components, the performance and functionality of which rely on the precision replication of surface forms and on minimizing residual stress. The present work constitutes a systematic and comprehensive analysis of practical microlens arrays that are designed for light-field applications. Process parameters are screened and optimized using a two-stage design of experiments approach. Based on in-line process monitoring and a quantitative and qualitative evaluation being carried out in terms of geometric accuracy, surface quality and stress birefringence, the replication is shown to relate directly to machine settings and dynamic machine responses. The geometric accuracy and stress birefringence are both largely associated with screw displacement and peak cavity pressure during the packing stage, while surface quality is closely related to cavity temperature. This study provides important insights and recommendations regarding the overall replication quality of microlens arrays, while advanced injection moulding solutions may be necessary to further improve the general replication quality.

The full text can be downloaded at https://link.springer.com/article/10.1007%2Fs40436-020-00341-y

On the application of additive manufacturing methods for auxetic structures: a review

Athul Joseph, Vinyas Mahesh, Dineshkumar Harursampath

2021, 9(3): 342-368. doi:10.1007/s40436-021-00357-y

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Auxetic structures are a special class of structural components that exhibit a negative Poisson's ratio (NPR) because of their constituent materials, internal microstructure, or structural geometry. To realize such structures, specialized manufacturing processes are required to achieve a dimensional accuracy, reduction of material wastage, and a quicker fabrication. Hence, additive manufacturing (AM) techniques play a pivotal role in this context. AM is a layer-wise manufacturing process and builds the structure as per the designed geometry with appreciable precision and accuracy. Hence, it is extremely beneficial to fabricate auxetic structures using AM, which is otherwise a tedious and expensive task. In this study, a detailed discussion of the various AM techniques used in the fabrication of auxetic structures is presented. The advancements and advantages put forward by the AM domain have offered a plethora of opportunities for the fabrication and development of unconventional structures. Therefore, the authors have attempted to provide a meaningful encapsulation and a detailed discussion of the most recent of such advancements pertaining to auxetic structures. The article opens with a brief history of the growth of auxetic materials and later auxetic structures. Subsequently, discussions centering on the different AM techniques employed for the realization of auxetic structures are conducted. The basic principle, advantages, and disadvantages of these processes are discussed to provide an in-depth understanding of the current level of research. Furthermore, the performance of some of the prominent auxetic structures realized through these methods is discussed to compare their benefits and shortcomings. In addition, the influences of geometric and process parameters on such structures are evaluated through a comprehensive review to assess their feasibility for the latermentioned applications. Finally, valuable insights into the applications, limitations, and prospects of AM for auxetic structures are provided to enable the readers to gauge the vitality of such manufacturing as a production method.

The full text can be downloaded at https://link.springer.com/article/10.1007%2Fs40436-021-00357-y

Layout design of a mixed-flow production line based on processing energy consumption and buffer configuration

Cai-Xia Zhang, Shu-Lin Dong, Hong-Yan Chu, Guo-Zhi Ding, Zhi-Feng Liu, Shi-Yao Guo, Chong-Bin Yang

2021, 9(3): 369-387. doi:10.1007/s40436-021-00354-1

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Green manufacturing is a growing trend, and an effective layout design method for production lines can reduce resource wastage in processing. This study focuses on existing problems such as low equipment utilization, long standby time, and low logistics efficiency in a mixed-flow parallel production line. To reduce the energy consumption, a novel method considering an independent buffer configuration and idle energy consumption analysis is proposed for this production line's layout design. A logistics intensity model and a machine tool availability model are established to investigate the influences of independent buffer area configuration on the logistics intensity and machine tool availability. To solve the coupling problem between machine tools in such production lines, a decoupling strategy for the relationship between machine tool processing rates is explored. An energy consumption model for the machine tools, based on an optimized configuration of independent buffers, is proposed. This model can effectively reduce the idle energy consumption of the machine tools while designing the workshop layout. Subsequently, considering the problems encountered in workshop production, a comprehensive optimization model for the mixed-flow production line is developed. To verify the effectiveness of the mathematical model, it is applied to an aviation cabin production line. The results indicate that it can effectively solve the layout problem of mixed-flow parallel production lines and reduce the idle energy consumption of machine tools during production. The proposed buffer configuration and layout design method can serve as a theoretical and practical reference for the layout design of mixed-flow parallel production lines.

The full text can be downloaded at https://link.springer.com/article/10.1007%2Fs40436-021-00354-1

Prediction of cutting power and surface quality, and optimization of cutting parameters using new inference system in high-speed milling process

Long-Hua Xu, Chuan-Zhen Huang, Jia-Hui Niu, Jun Wang, Han-Lian Liu, Xiao-Dan Wang

2021, 9(3): 388-402. doi:10.1007/s40436-020-00339-6

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During the actual high-speed machining process, it is necessary to reduce the energy consumption and improve the machined surface quality. However, the appropriate prediction models and optimal cutting parameters are difficult to obtain in complex machining environments. Herein, a novel intelligent system is proposed for prediction and optimization. A novel adaptive neurofuzzy inference system (NANFIS) is proposed to predict the energy consumption and surface quality. In the NANFIS model, the membership functions of the inputs are expanded into:membership superior and membership inferior. The membership functions are varied based on the machining theory. The inputs of the NANFIS model are cutting parameters, and the outputs are the machining performances. For optimization, the optimal cutting parameters are obtained using the improved particle swarm optimization (IPSO) algorithm and NANFIS models. Additionally, the IPSO algorithm as a learning algorithm is used to train the NANFIS models. The proposed intelligent system is applied to the high-speed milling process of compacted graphite iron. The experimental results show that the predictions of energy consumption and surface roughness by adopting the NANFIS models are up to 91.2% and 93.4%, respectively. The NANFIS models can predict the energy consumption and surface roughness more accurately compared with other intelligent models. Based on the IPSO algorithm and NANFIS models, the optimal cutting parameters are obtained and validated to reduce both the cutting power and surface roughness and improve the milling efficiency. It is demonstrated that the proposed intelligent system is applicable to actual highspeed milling processes, thereby enabling sustainable and intelligent manufacturing.

The full text can be downloaded at https://link.springer.com/article/10.1007%2Fs40436-020-00339-6

Failure mode analysis on compression of lattice structures with internal cooling channels produced by laser powder bed fusion

E. Virgillito, A. Aversa, F. Calignano, M. Lombardi, D. Manfredi, D. Ugues, P. Fino

2021, 9(3): 403-413. doi:10.1007/s40436-021-00348-z

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Conformal cooling coils have been developed during the last decades through the use of additive manufacturing (AM) technologies. The main goal of this study was to analyze how the presence of an internal channel that could act as a conformal cooling coil could affect compressive strength and quasi-elastic gradient of AlSi10Mg lattice structures produced by laser powder bed fusion (LPBF). Three different configurations of samples were tested in compression at 25℃ and 200℃. The reference structures were body centered cubic (BBC) in the core of the samples with vertical struts along Z (BCCZ) lattices in the outer perimeter, labelled as NC samples. The main novelty consisted in inserting a straight elliptical channel and a 45° elliptical channel inside the BCCZ lattice structures, labelled as SC and 45C samples respectively. All the samples were then tested in as-built (AB) condition, and after two post process heat treatments, commonly used for AlSi10Mg LPBF industrial components, a stress relieving (SR) and a T6 treatment. NC lattice structures AB exhibited an overall fragile fracture and therefore the SC and 45C configuration samples were tested only after thermal treatments. The test at 25℃ showed that all types of samples were characterized by negligible variations in their quasi-elastic gradients and yield strength. On the contrary, the general trend of stress-strain curves was influenced by the presence of the channel and its position. The test at 200℃ showed that NC, SC and 45C samples after SR and T6 treatments exhibited a metal-foam like deformation.

The full text can be downloaded at https://link.springer.com/article/10.1007%2Fs40436-021-00348-z

Modeling the density gradient of 3D nanofiber scaffolds fabricated by divergence electrospinning

Muhammad Adib Uz Zaman, Dilshan Sooriyaarachchi, Ying-Ge Zhou, George Z. Tan, Dong-Ping Du

2021, 9(3): 414-429. doi:10.1007/s40436-020-00307-0

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Following recent insights on structure-cellfunction interactions and the critical role of the extracellular matrix (ECM), the latest biofabrication approaches have increasingly focused on designing materials with biomimetic microarchitecture. Divergence electrospinning is a novel fabrication method for three-dimensional (3D) nanofiber scaffolds. It is introduced to produce 3D nanofiber mats that have numerous applications in regenerative medicine and tissue engineering. One of the most important characteristics of 3D nanofiber mats is the density gradient. This study provides a statistical analysis and response surface modeling framework based on experimental data to evaluate the manner by which the geometric designs of double-bevel collectors influence the fiber density gradient. Specifically, variance of analysis and sensitivity analysis were performed to identify parameters that had significant effects, and a response surface model embedded with seven location indicators was developed to predict the spatial distribution of fiber density for different collector designs. It was concluded that the collector height, bevel angle, and their interactions were significant factors influencing the density gradient. This study revealed the sensitivity of system configuration and provided an optimization tool for process controllability of microstructure gradients.

The full text can be downloaded at https://link.springer.com/article/10.1007%2Fs40436-020-00307-0

Three-dimensional modeling and reconstructive change of residual stress during machining process of milling, polishing, heat treatment, vibratory finishing, and shot peening of fan blade

Ji-Yin Zhang, Chang-Feng Yao, Min-Chao Cui, Liang Tan, Yun-Qi Sun

2021, 9(3): 430-445. doi:10.1007/s40436-021-00351-4

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Residual stress during the machining process has always been a research hotspot, especially for aero-engine blades. The three-dimensional modeling and reconstructive laws of residual stress among various processes in the machining process of the fan blade is studied in this paper. The fan blades of Ti-6Al-4V are targeted for milling, polishing, heat treatment, vibratory finishing, and shot peening. The surface and subsurface residual stress after each process is measured by the X-ray diffraction method. The distribution of the surface and subsurface residual stress is analyzed. The Rational Taylor surface function and cosine decay function are used to fit the characteristic function of the residual stress distribution, and the empirical formula with high fitting accuracy is obtained. The value and distribution of surface and subsurface residual stress vary greatly due to different processing techniques. The reconstructive change of the surface and subsurface residual stress of the blade in each process intuitively shows the change of the residual stress between the processes, which has a high reference significance for the research on the residual stress of the blade processing and the optimization of the entire blade process.

The full text can be downloaded at https://link.springer.com/article/10.1007%2Fs40436-021-00351-4

Surface integrity evolution of machined NiTi shape memory alloys after turning process

Yan-Zhe Zhao, Kai Guo, Vinothkumar Sivalingam, Jian-Feng Li, Qi-Dong Sun, Zhao-Ju Zhu, Jie Sun

2021, 9(3): 446-456. doi:10.1007/s40436-020-00330-1

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Owing to their shape memory effect and pseudoelasticity, NiTi shape memory alloys (SMAs) are widely used as functional materials. Mechanical processes particularly influence the final formation of the product owing to thermal softening and work-hardening effects. Surface integrity is an intermediate bridge between the machining parameter and performance of the product. In this study, experiments were carried out on turning NiTi SMAs at different cutting speeds, where surface integrity characteristics were analyzed. The results show that a higher cutting speed of 125 m/min is required to turn NiTi SMAs based on the evaluation of surface integrity. The degree of work hardening is higher at 15 m/min. Consequently, as a primary effect, work hardening appears on the plastic deformation of the machined samples, leading to dislocations and defects. As the cutting speed increases, the thermal softening effect exceeds work hardening and creates a smoother surface. A stress-induced martensitic transformation is considered during the turning process, but this transformation is reversed to an austenite from the X-ray diffraction (XRD) results. According to the differential scanning calorimetry (DSC) curves, the phase state and phase transformation are less influenced by machining. Subsequently, the functional properties of NiTi-SMAs are less affected by machining.

The full text can be downloaded at https://link.springer.com/article/10.1007%2Fs40436-020-00330-1

Parameter identification and blanking simulations of DP1000 and Al6082-T6 using Lemaitre damage model

Sheng Cai, Lin Chen

2021, 9(3): 457-472. doi:10.1007/s40436-021-00350-5

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This work provides numerical and experimental investigations of blanking process, where the shear-enhanced Lemaitre's damage model is fully characterized and successfully applied in blanking process to predict the cutting force and cutting edge geometry under different blanking process parameters. Advanced high strength steel DP1000 and an aluminum alloy Al6082-T6 are selected for series of experiments. To obtain the damage parameters in Lemaitre's damage model the flat rectangular notched specimens tensile test was conducted and the inverse parameter identification procedure was performed. For characterizing the crack closure parameter h in the shear enhanced Lemaitre's damage model, an in-plane torsion test with novel specimen design was conducted. The finite element model (FEM) of this test was established with the minimum mesh size of 0.01 mm which was consistent with the minimum mesh size in the shear zone of the FEM for blanking process simulation. The longitudinal strain distributions of four kinds of initial notch radius or centralhole specimen were measured and compared with simulation results to validate the FEMs for these four tests. Deformation analysis of blanking of a circular work piece also was performed under three clearances. The effects of blanking conditions on sheared part morphology were detected. Stress triaxiality distribution of the blank sheet was revealed taking advantage of the successfully established FEM. The availability of the testing method and the determination method of the parameters was investigated.

The full text can be downloaded at https://link.springer.com/article/10.1007%2Fs40436-021-00350-5

Novel evaluation method for metal workability during cross wedge rolling process

Ming Cheng, Ming-Jie Shi, Petrenko Vladimir, Rui-Xue Wang, Shi-Hong Zhang

2021, 9(3): 473-481. doi:10.1007/s40436-020-00344-9

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This study presents a novel method using a disklike sample to assess the workability of metal during the cross wedge rolling (CWR) process. Using this method, we can quantitatively evaluate the moment destruction which occurs at the center of the sample during CWR. In this study, 45 steel was selected to demonstrate the proposed method. Firstly, we designed a model for the tools and sample, conducted finite element simulations to analyze the distribution regulations of metal flow, stress, and strain, and evaluated the relationship between the damage and moving distance of the tool during the forming process. Then, we obtained the optimal deformation temperature range, rolling speed, and geometry parameters for the tool. Finally, experiments were conducted from 20℃ to 1 200℃ to verify the accuracy of the developed model. It was demonstrated that the model was significantly accurate in accessing the workability of 45 steel in the CWR process. The proposed method could be generalized to investigate the CWR process for other materials, such as aluminum alloys, superalloys, titanium alloys, etc.

The full text can be downloaded at https://link.springer.com/article/10.1007%2Fs40436-020-00344-9

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