The Experts below are selected from a list of 201 Experts worldwide ranked by ideXlab platform

Peijs T. - One of the best experts on this subject based on the ideXlab platform.

  • Hemp fibre as alternative to glass fibre in Sheet moulding compound. Part 2 : impact properties
    'Maney Publishing', 2015
    Co-Authors: Patel H., Ren Guogang, Hogg P.j., Peijs T.
    Abstract:

    This paper describes the results of falling weight impact tests on natural fibre reinforced polyester composites fabricated using a Conventional Sheet moulding compound (SMC) process. The influence of hemp fibre and CaCO3 filler content on the penetration energy of hemp fibre reinforced Sheet moulding compound (H-SMC) is reported and compared with glass fibre reinforced Sheet moulding compound (G-SMC). To evaluate the influence of fibre/matrix interfacial adhesion on the impact behaviour of these H-SMCs, the hemp fibres were treated with alkaline and silane treatments, as well as a combination of these treatments. A simple mechanistic model is proposed for these natural fibre composites and is used to obtain more insight into the impact behaviour of the composites as well as to provide guidelines to compare the experimental data with theory.Peer reviewe

  • Hemp fibre as alternative to glass fibre in Sheet moulding compound. Part 1 : influence of fibre content and surface treatment on mechanical properties
    'Maney Publishing', 2010
    Co-Authors: Patel H.k., Ren Guogang, Hogg P.j., Peijs T.
    Abstract:

    Original article can be found at : http://www.iom3.org/ Copyright ManeyHemp fibre mat reinforced unsaturated polyester composites were fabricated using a Conventional Sheet moulding compound process. The influence of fibre and CaCO3 filler content on strength and stiffness of these hemp fibre reinforced Sheet moulding compounds is reported and compared with data for chopped glass fibre reinforced Sheet moulding compounds. In addition the influence of alkaline and silane treatments of the hemp fibres is evaluated. The experimental data are compared to modified versions of the Cox-Krenchel and Kelly-Tyson models, supplemented with parameters of composite porosity to improve the prediction of composite tensile properties. A good agreement was found between the modified models and experimental data for strenght and stiffness. The results indicate that hemp fibre reinforced Sheet moulding compounds are of interest for low cost engineering applications that require high stiffness to weight ratios.Peer reviewe

Marion Merklein - One of the best experts on this subject based on the ideXlab platform.

  • Improvement of deep drawability of ultra-fine grained 6000 series aluminum alloy by tailored heat treatment
    Procedia Manufacturing, 2018
    Co-Authors: Jürgen Herrmann, Marion Merklein
    Abstract:

    Abstract Among other approaches like alloying, it is possible to increase the strength of aluminum Sheet material by the application of processing techniques like Accumulative Roll Bonding. However, the ductility will be reduced, which results in a limited formability in deep drawing operations. In this context, the Tailor Heat Treated Blanks technology is a well-known approach to enhance the forming limits of Conventional precipitation hardenable aluminum alloys. The local softening of a blank can be achieved by a short-term heat treatment, which causes a dissolution of the MgSi-clusters in the heat treated zones. In a subsequent deep drawing operation, the material flow can be improved from the softened towards crack-critical areas. Within this investigation, the method of Tailor Heat Treated Blanks is transferred to a multi-layered, ultra-fine grained Sheet material of the aluminum alloy AA6014 in order to investigate the effect of a local short-term heat treatment on the forming limits in deep drawing. In a first step, a material characterization in dependency of different heat treatment temperatures is carried out. The strength and ductility, as well as the bond strength of the multi-layered Sheets, are investigated. Concluding, the effect on the formability is examined by deep drawing experiments on cylindrical cups in combination with a local heat treatment of the outer flange area prior to the forming step. The results regarding the limiting drawing ratio are compared with a Conventional Sheet material in the T4 temper condition and a multi-layered Sheet material without heat treatment. The investigations indicate that the drawability can be enhanced significantly by the combination of both methods.

  • locally adapted tribological conditions as a method for influencing the material flow in Sheet bulk metal forming processes
    Key Engineering Materials, 2015
    Co-Authors: Maria Loeffler, Thomas Schneider, Ulrich Vierzigmann, U Engel, Marion Merklein
    Abstract:

    Due to ecological and economic challenges there is a growing demand for lightweight construction by using closely-tolerated complex functional components with variants. Conventional Sheet and bulk metal forming operations are often improvident in producing such parts. A promising approach is the process-class “Sheet-bulk metal forming” (SBMF). Within SBMF bulk forming operations are applied to Sheet metals, often in combination with Sheet forming operations [1]. This leads to a significant gradient in load conditions regarding stress and strain states and causes locally varying tribological conditions. Thus, the investigation of the tribological conditions and the provision of suited tribological systems are essential for the successful application of SBMF processes. The objective of the current study is the experimental investigation of the applicability of tribological adaptions by local abrasive blasting on a single-stage process combination of deep drawing and upsetting to produce a component with an external gearing. The manipulation of the local tribological conditions by the use of abrasive blasting leads to a better control of the material flow and in consequence to an improved quality of the components in terms of higher mould filling and cup heights, and a reduced thickening of the Sheet in the area of the cup bottom.

  • bulk forming of Sheet metal
    Cirp Annals-manufacturing Technology, 2012
    Co-Authors: Marion Merklein, Bernd-arno Behrens, Julian M. Allwood, Alexander Brosius, Hinnerk Hagenah, Karl Kuzman, Kenichiro Mori, A E Tekkaya, A Weckenmann
    Abstract:

    Abstract Ever increasing demands on functional integration of high strength light weight products leads to the development of a new class of manufacturing processes. The application of bulk forming processes to Sheet or plate semi-finished products, sometimes in combination with Conventional Sheet forming processes creates new products with the requested properties. The paper defines this new class of Sheet-bulk metal forming processes, gives an overview of the existing processes belonging to this class, highlights the tooling aspects as well as the resulting product properties and presents a short summary of the relevant work that has been done towards modeling and simulation.

Fadi Abufarha - One of the best experts on this subject based on the ideXlab platform.

  • calibration of barlat yld2004 18p yield function using cpfem and 3d rve for the simulation of single point incremental forming spif of 7075 o aluminum Sheet
    International Journal of Mechanical Sciences, 2018
    Co-Authors: Rasoul Esmaeilpour, Hyunki Kim, Taejoon Park, Farhang Pourboghrat, Bassam Mohammed, Fadi Abufarha
    Abstract:

    Abstract In Conventional Sheet metal forming processes, such as stamping, application of a two-dimensional (2D) plane stress yield function is sufficient as the out-of-plane stresses (σzz, σxz, σyz) are negligible and the deformation occurs under plane stress condition. However, in incremental Sheet forming (ISF) processes, significant through-the-thickness shears necessitates the use of a three-dimensional (3D) yield function to account for out-of-plane stress components. However, to calibrate the parameters of the non-quadratic anisotropic 3D yield function Yld2004-18p, out-of-plane normal and shear stresses are needed which are very difficult to obtain experimentally. In this study, the out-of-plane stresses were found using a three-dimensional (3D) representative volume element (RVE) developed from Electron Backscattered Diffraction (EBSD) images. By applying the crystal plasticity (CP) material model to these 3D RVEs, it was possible to perform computational experiments to generate the out-of-plane stresses required for the calibration of the Yld2004-18p yield function. To simulate the single point incremental forming (SPIF) of 7075-O aluminum alloy Sheet, two different yield functions namely; Hill's 1948 and Yld2004-18p were used. A detailed comparison of the two yield functions’ predictions was made with respect to different parameters, such as the tool force and moment, part thickness, development of stress and strain tensor components, and effective plastic strain distribution.

Dongkai Xu - One of the best experts on this subject based on the ideXlab platform.

  • mechanism investigation for the influence of tool rotation and laser surface texturing lst on formability in single point incremental forming
    International Journal of Machine Tools & Manufacture, 2013
    Co-Authors: Weichao Wu, Dongkai Xu, Bin Lu, Rajiv Malhotra, J. Chen, Jian Cao
    Abstract:

    Abstract Single point incremental forming (SPIF) is a new Sheet metal forming process which achieves higher formability, greater process flexibility and reduced forming force compared to Conventional Sheet forming operations due to its characteristic of localized deformation. In recent years, a novel SPIF process assisted by localized friction heat is developed to further improve the material formability. Physically, the frictional heat is generated by the high relative motion at tool–workpiece interface resulted from tool rotation. However, the mechanisms behind formability difference induced by tool rotation at both low and high speed ranges are required to investigate in detail. In this paper, a series of experiments with an increase of tool rotation speeds ranging from 0 to 7000 rpm are conducted to form AA5052-H32 aluminum alloy Sheets into a truncated funnel. Additionally, the obtained results are analyzed in terms of formability, forming forces and temperature trends to find out the different roles of friction and heat during the forming process. As a result, the formability behaviors at varying tool rotation speeds can be categorized into four stages according to different reasons. It indicates that friction is the dominant factor in low tool rotation speed range (0–1000 rpm) but will be substituted by thermal effect and potential dynamic recrystallization in high tool rotation speed range (2000–7000 rpm). Furthermore, due to the proved lubrication enhancement and hydrodynamic enhancement generated by surface textures, a laser surface textured forming tool is also utilized to show its influence on forming forces, measured temperatures and the corresponding formability. Finally, it demonstrates that the fabricated laser surface texturing (LST) is capable to reduce the friction at tool–workpiece interface and change the magnitude of heat generation.

Rajiv Malhotra - One of the best experts on this subject based on the ideXlab platform.

  • a mixed double sided incremental forming toolpath strategy for improved geometric accuracy
    Journal of Manufacturing Science and Engineering-transactions of The Asme, 2015
    Co-Authors: Zixuan Zhang, Rajiv Malhotra, Huaqing Ren, Newell Moser, Jacob Smith, Ebot Ndipagbor, Cedric Z Xia, Kornel F Ehmann
    Abstract:

    Double-sided incremental forming (DSIF) is a relatively new dieless forming process which uses two hemispherical ended tools, one on each side of the Sheet, moving along a predefined trajectory to locally deform a peripherally clamped Sheet of metal. DSIF provides greater process flexibility, higher formability, and eliminates the tooling cost when compared to Conventional Sheet forming processes. While DSIF provides much improved geometric accuracy compared to other incremental forming processes, current toolpath planning strategies suffer from long forming times. A novel mixed double-sided incremental forming (MDSIF) toolpath strategy is proposed in the present study. It simultaneously reduces the total forming time by half while preserving the best currently achievable geometric accuracy. The effect of the forming parameters, i.e., of the incremental depth and of tool positioning on the geometric accuracy of the parts formed with MDSIF was investigated and compared to those formed by traditional DSIF strategies.

  • effects of incremental depth and tool rotation on failure modes and microstructural properties in single point incremental forming of polymers
    Journal of Materials Processing Technology, 2015
    Co-Authors: Mohammad Ali Davarpanah, Rajiv Malhotra, Amin Mirkouei, Xiaoyan Yu, Srikanth Pilla
    Abstract:

    Abstract Single Point Incremental Forming (SPIF) is a Sheet forming process characterized by advantages that include low-cost and part-shape-independent tooling, higher formability and greater process flexibility as compared to Conventional Sheet forming. While recent work has demonstrated the possibility of SPIF of polymers the effects of incremental depth and tool rotation speed, key process parameters in SPIF, have rarely been examined. This work experimentally examines how incremental depth and tool rotation speed affect the failure mode during forming, forming forces as well as the void structure and crystallinity of the formed material in polymer SPIF. The dependence of both tearing and wrinkling on the incremental depth and tool rotation speed is uncovered. It is shown that contrary to SPIF of metals, greater incremental depths result in increased formability in polymer SPIF, but this advantage is limited by the occurrence of Sheet wrinkling at excessively high incremental depths. Further, the occurrence of Sheet wrinkling depends not just on the incremental depth but also on the part shape being formed. Microstructural examination of the formed material shows that greater incremental depth results in greater void densities and that the material formed with SPIF has greater crystallinity than the unformed material. Additionally, it is shown that higher tool rotation speed can cause earlier onset of wrinkling. The implications of these observations on SPIF of polymers are discussed.

  • mechanism investigation for the influence of tool rotation and laser surface texturing lst on formability in single point incremental forming
    International Journal of Machine Tools & Manufacture, 2013
    Co-Authors: Weichao Wu, Dongkai Xu, Bin Lu, Rajiv Malhotra, J. Chen, Jian Cao
    Abstract:

    Abstract Single point incremental forming (SPIF) is a new Sheet metal forming process which achieves higher formability, greater process flexibility and reduced forming force compared to Conventional Sheet forming operations due to its characteristic of localized deformation. In recent years, a novel SPIF process assisted by localized friction heat is developed to further improve the material formability. Physically, the frictional heat is generated by the high relative motion at tool–workpiece interface resulted from tool rotation. However, the mechanisms behind formability difference induced by tool rotation at both low and high speed ranges are required to investigate in detail. In this paper, a series of experiments with an increase of tool rotation speeds ranging from 0 to 7000 rpm are conducted to form AA5052-H32 aluminum alloy Sheets into a truncated funnel. Additionally, the obtained results are analyzed in terms of formability, forming forces and temperature trends to find out the different roles of friction and heat during the forming process. As a result, the formability behaviors at varying tool rotation speeds can be categorized into four stages according to different reasons. It indicates that friction is the dominant factor in low tool rotation speed range (0–1000 rpm) but will be substituted by thermal effect and potential dynamic recrystallization in high tool rotation speed range (2000–7000 rpm). Furthermore, due to the proved lubrication enhancement and hydrodynamic enhancement generated by surface textures, a laser surface textured forming tool is also utilized to show its influence on forming forces, measured temperatures and the corresponding formability. Finally, it demonstrates that the fabricated laser surface texturing (LST) is capable to reduce the friction at tool–workpiece interface and change the magnitude of heat generation.