Friction Spinning Process Research Articles

Fibre waviness reduction in thermoplastic pultrusion by using DREF yarns

Non-reactive thermoplastic pultrusion impregnation issues are mitigated by using hybrid input materials. Co-wound (CW) and commingled yarns are an assembly of continuous polymer and reinforcement fibres. Continuous thermoplastic fibres have shown to induce waviness in the reinforcement fibres during pultrusion due to their shrinkage at high temperature. DREF yarns are composed of a core of continuous reinforcement fibres onto which discontinuous polymer fibres are applied using the friction spinning process. This study, based on the application of 3 N and 0 N tension on CW and DREF yarns, aimed to highlight the contribution of discontinuous polymer fibres on reducing reinforcement waviness in pultruded rods. CW yarns’ reaction to heating showed continuous polyethylene terephthalate (PET) fibres shrinkage resulting in wavy glass fibres (GF). Conversely, the GF in DREF yarns remained straight. Pultrusion experiments with yarn tension of 3 N were done to alleviate the GF waviness. However, the porosity was rather high at 4.2 % for CW rods and 2.3 % for DREF rods. Pultrusion experiments without tension showed lower porosity of level of 2.9 % for CW yarns and as low as 1.1 % for DREF yarns. However, CT-scan image indicated GF waviness in CW rods. GF in DREF rods remained straight. The in-plane shear strength reached 119 MPa. Thermoplastic pultrusion using DREF yarns resulted in composites without reinforcement fibre waviness, lower porosity level and superior shear strength.

Friction spun spandex/rGO/Ag/polyester core-sheath yarn with antibacterial activity for wearable sensors

Wearable sensors, which feature textile substrates integrated with conductive layers, have received increasing attention from researchers due to their huge potential in health management. However, the inevitable damage of conductive layer caused by friction and bacterial growth on the textile substrate during its direct contact with bare skin are still the issues that hinder the long-term service of wearable sensors. Herein, a core-sheath yarn was prepared by wrapping polyester (PET) fibers coated with reduced graphene oxide (rGO)/silver nanoparticles (Ag NPs) around the spandex filaments via friction spinning. The core-sheath structure guarantees good prevention of the interface composed of rGO and Ag NPs in between from friction, while the introduction of Ag NPs ensures antibacterial activity of the yarn. The morphology and chemical composition of the nanomaterials deposited on the surface of PET fibers was investigated to reveal the sensing mechanism of the yarn. Meanwhile, its sensing performance was comprehensively evaluated from the perspectives of sensitivity, durability and comparison of commercial ECG. Despite the fact that inevitable damage of the rGO/Ag layer occurred during the friction spinning process, the core-sheath yarn still featured a gauge factor of 8.11 and a threshold of sensing range up to 68.57 %. Apart from being able to detect respiratory signals, cardio signals with the frequency of 70 beat per min (bpm) was also recorded. Compared to signals with the frequency of 73 bpm recorded by a commercial ECG sensor simultaneously, the core-sheath yarn exhibited satisfying precision. Moreover, the existence of Ag NPs in the conductive interface endowed the yarn with ability to yield 13-mm and 15-mm wide growth inhibition zones of E. coli and S. aureus, respectively. The cardiorespiratory sensing ability coupled with antibacterial activity of the yarn suggested its satisfying sensitivity and prolonged service time, making it a promising wearable sensor subjected to direct skin contact for long-time cardiorespiratory monitoring.

Manufacture of Defined Residual Stress Distributions in the Friction-Spinning Process: Driven Tool and Subsequent Flow-Forming

Friction-spinning as an innovative incremental forming process enables large degrees of deformation in the field of tube and sheet metal forming due to a self-induced heat generation in the forming zone. This paper presents a new tool and process design with a driven tool for the targeted adjustment of residual stress distributions in the friction-spinning process. Locally adapted residual stress depth distributions are intended to improve the functionality of the friction-spinning workpieces, e.g. by delaying failure or triggering it in a defined way. The new process designs with the driven tool and a subsequent flow-forming operation are investigated regarding the influence on the residual stress depth distributions compared to those of standard friction-spinning process. Residual stress depth distributions are measured with the incremental hole-drilling method. The workpieces (tubular part with a flange) are manufactured using heat-treatable 3.3206 (EN-AW 6060 T6) tubular profiles. It is shown that the residual stress depth distributions change significantly due to the new process designs, which offers new potentials for the targeted adjustment of residual stresses that serve to improve the workpiece properties.

Manufacture of Defined Residual Stress Distributions in the Friction-Spinning Process: Investigations and Run-to-Run Predictive Control

Friction-spinning as an innovative incremental forming process enables high degrees of deformation in the field of tube and sheet metal forming due to self-induced heat generation in the forming area. The complex thermomechanical conditions generate non-uniform residual stress distributions. In order to specifically adjust these residual stress distributions, the influence of different process parameters on residual stress distributions in flanges formed by the friction-spinning of tubes is investigated using the design of experiments (DoE) method. The feed rate with an effect of −156 MPa/mm is the dominating control parameter for residual stress depth distribution in steel flange forming, whereas the rotation speed of the workpiece with an effect of 18 MPa/mm dominates the gradient of residual stress generation in the aluminium flange-forming process. A run-to-run predictive control system for the specific adjustment of residual stress distributions is proposed and validated. The predictive model provides an initial solution in the form of a parameter set, and the controlled feedback iteratively approaches the target value with new parameter sets recalculated on the basis of the deviation of the previous run. Residual stress measurements are carried out using the hole-drilling method and X-ray diffraction by the cosα-method.

Joining with versatile joining elements formed by friction spinning

Mechanical joints are an essential part of modern lightweight structures in a broad variety of applications. The reason for this is the rapidly increasing number of different material combinations needing to be joined in areas of application like the automotive industry. It is currently common to use numerous standardized elements (if necessary, from different joining technologies) instead of individually adapted joining elements. This leads to a large number of different joining elements per product and thus to high costs.An innovative approach to overcome this issue is the design and manufacturing of application adapted joining elements. A promising strategy for the manufacturing of adapted joining elements of this type is the so-called friction spinning process. The joining elements formed in this way can be specifically adapted to the application in question in terms of shape and mechanical properties. The joining process using this friction spun joint connectors (FSJC) benefits from the use of friction-induced heat and supports the process by reducing the joining forces required through a variation of the rotational speed and the feed-rate. By controlling the significant process parameter (e.g. the joining force), it is possible to substantially influence the quality of the joint or the joint properties. The following contribution will present results of ongoing research at Paderborn University and includes the process concept, the process properties, the tooling and the results of the experimental investigations of the joining of two preholed sheet metal parts with help of this new joining process.

Friction-Induced Recycling Process for User-Specific Semi-Finished Product Production

Modern forming processes often allow today the efficient production of complex parts. In order to increase the sustainability of forming processes it would be favorable if the forming of workpieces becomes possible using production waste. At the Chair of Forming and Machining Technology of the Paderborn University (LUF) research is presently conducted with the overall goal to produce workpieces directly from secondary aluminum (e.g., powder and chips). Therefore, friction-based forming processes like friction spinning (or cognate processes) are used due to their high efficiency. As a pre-step, the production of semi-finished parts was the subject of accorded research work at the LUF. Therefore, a friction-based hot extrusion process was used for the full recycling or rework of aluminum chips into profiles. Investigations of the recycled semi-finished products show that they are comparable to conventionally produced semi-finished products in terms of dimensional stability and shape accuracy. An analysis of the mechanical properties of hardness and tensile strength shows that a final product with good and homogeneously distributed properties can be produced. Furthermore, significant correlations to the friction spinning process could be found that are useful for the above-mentioned direct part production from secondary aluminum.

Influence of composite architecture and interfacial bonding on their impact properties

Resistance to impact thrust is one of the most important requirement along with many others for defining suitable applications of any composite materials. In this present work, the influence of composite architecture and composite interfacial bonding strength on the impact performance of flax reinforced PP composites have been investigated. In this regard two different composite architecture through conventional film stacking method and through DREF (DR. E. Fehrer open-end friction spinning process) yarn consolidation method have been produced and to alter the fibre–matrix interfacial bonding the flax fibres are treated with MAgPP (Maleic Anhydride grafted Polypropylene). Finally, the notch Izod impact behaviour of all composite samples are evaluated and compared.

Al2O3/ZrO2-8Y2O3 and (Cr,Ti)AlSiN tool coatings to influence the temperature and surface quality in friction-spinning processes

Friction-spinning is an incremental forming process, which is accompanied by complex thermal and mechanical loads in the tool and the formed part. To influence the process temperature, two main process parameters, i.e. the rotation speed and the feed rate, can be adapted. With the objective to improve the tool performance and the quality of the workpiece, this study focuses on a coating concept for friction-spinning tools made of high speed steel (HS6 5 2C, 1.3343). On the one hand, atmospheric plasma sprayed (APS) Al2O3 and ZrO2-8Y2O3 coatings serve as a thermal insulator, and, on the other hand, physically vapor deposited (PVD) TiAlSi7.9N and CrAlSi7.5N films are applied to increase the hardness and wear resistance of the tools. In addition, duplex coatings, combining the APS and PVD technique, are synthesized to influence both the heat transfer and the tribological properties of friction-spinning tools. Subsequently, all coated tools are tested in a friction-spinning process to form flanges made of AW-6060 (AlMgSi 3.3206) tube materials. The tool temperatures are determined in-situ to investigate the impact of the tool coating on the process temperature. Compared to an uncoated tool, the alumina and zirconia coatings contribute to a reduction of the tool temperature by up to half, while the PVD films increase the hardness of the tool by 20 GPa. Furthermore, it is shown that the surface quality of thermally sprayed (TS) or PVD coated tools is directly related to the surface roughness of the resulting workpiece.

Friction-spinning—Grain structure modification and the impact on stress/strain behaviour

The friction-spinning process is an innovative incremental forming technique that enables high degree forming operations in the field of tube and sheet metal forming. The integration of friction-sub-processes from friction welding in a metal spinning process permits selfinduced heat generation of the part. Compared with conventional spinning processes, this in-process heat treatment allows the extension of existing forming limits and the production of more complex geometries from tubes and sheets. Additionally, the material/part properties like hardness, stress, grain structure/orientation, surface conditions etc. can be adjusted in a defined way during the forming process. This can be achieved using appropriate process parameter settings in combination with the degree of deformation. The choice of feed rate, relative motion and friction coefficient gives rise to a defined temperature profile and allows the use of specific process control strategies to produce parts with different material properties in different areas. Thus, the production of a new class of individually adjustable components is enabled. For example, these parts could be designed for load-optimized applications like complex hollow parts in aluminium or steel. This paper presents the results of the grain structure investigations and clarifies the influence of different process parameters in aluminium tube processing, especially during flange forming operations. A flange will thus be formed from an aluminium tube and, by using an additional tool system, its wall thickness can be adjusted in a defined manner. The paper addresses the influence of the significant process parameters (feed rate, rotation speed, temperature, wall thickness reduction and forming time) on grain structure refinement during flange forming. In addition, the impact of the material properties (hardness, stress/strain behaviour) is considered.

Friction-Spinning – Possibility of Grain Structure Adjustment

Abstract The friction spinning process is an innovative incremental forming technique that enables high degree forming operations in the field of tube and sheet metal forming. The integration of friction-sub-processes from friction welding into a metal spinning process permits the self-induced heat generation of the part. Compared with conventional spinning processes, this in-process heat treatment allows the extension of existing forming limits and also the production of more complex geometries from tubes and sheets. Additionally, the material/part properties like hardness, stress, grain structure/orientation, surface conditions etc. can be adjusted in a defined way during the forming process. This can be achieved through the use of appropriate process parameter settings in combination with the degree of deformation. The choice of feed rate, relative motion and friction coefficient gives rise to a defined temperature profile and allows the use of specific process control strategies to produce parts with different material properties in different areas. Thus, the production of a new class of individually adjustable components is enabled. For example, these parts could be designed for load optimized applications like complex hollow parts in aluminium or steel. This paper presents the results of the grain structure investigations and clarifies the influence of different process parameters in aluminium tube processing especially during flange forming operations. A flange will thus be formed from an aluminium tube and, using to further tool systems, the wall thickness of the flange can be adjusted in a defined manner. The paper addresses the influence of the significant process parameters (feed rate, rotation speed, temperature, wall thickness reduction and forming time) on the grain structure refine-ment during flange forming. In addition, the impact of the material properties (hardness, stress/strain behaviour) will be considered.

Analysis of the surface roughness obtained in a friction spinning process based on empirical models

In this paper, an new way to analyze and empirically model the surface roughness of a flange geometry after a friction spinning process is presented. The friction spinning process is an innovative incremental forming technology. This new process combines thermomechanical friction elements of the friction welding process within a conventional metal spinning process. The friction allows a self-inducted heat generation and as a consequence a defined increase of formability. It is possible to produce multifunctional, complex parts from standard tubes and sheets. The process thus readily meets the demands placed on efficiency and the manufacturability of complex lightweight components. By choosing the appropriate process parameters, e.g., axial feed rate or relative motion, the contact conditions between the tool and the workpiece can be influenced in a defined way. A further advantage is the feasibility of influencing the grain structure and the hardness in a locally defined manner. It offers the possibility to manufacture finished components with the required surface roughness. Since not all parameter settings of the parameters rotation speed, head radius, feed, and tool infeed width lead to a measurable surface of the component, a gradient boosting machine will be used as classifier for predicting the valid areas of the design space. Furthermore, the influence of the tool temperature is taken into account. For the empirical modeling of the spatial distribution of the surface roughness, methods from the design and analysis of computer experiments are employed.

Influence of Friction Spinning Process Parameters on Spinnability of Pergularia/Cotton-Blended Yarns

In this study, spinnability of Pergularia daemia seed fiber (70%) and cotton fiber (30%) core/100% cotton fiber sheath DREF-3 core yarns of 74 tex were studied using different spinning parameters in order to understand their effect on yarn properties. Box-Behnken Design was used for the optimization of core ratio, drum speed, and suction pressure and to evaluate the effects and interactions of the process variables on the yarn properties at a constant opening roller speed of 12,000 rpm and delivery rate of 100 m/min. The effect of the core/sheath ratio on yarn quality index is significant. With an increase in the core/sheath ratio, yarn tenacity, and elongation decreases due to insufficient wrapper fibers in the yarn and yarn unevenness increases due to higher feed rate and draft at higher core ratio. An increase in the spinning drum speed increases the yarn quality index up to certain range and then decreases at higher speed due to damaging of fibers in the sheath and more number of hooks at the end of fibers. At a higher air suction pressure, yarn tenacity and the elongation at break increases which ultimately increases the yarn quality index. From the regression analysis, it is observed that the drum speed and suction pressure has no significant effect on yarn unevenness.

Friction-spinning – Interesting Approach to Manufacture of Complex Sheet Metal Parts and Tubes

Friction-spinning is an innovative incremental forming process that permits the defined adjustment of material properties in a particularly precise manner. The process is characterised by the use of process elements from both metal spinning and friction welding. As the workpieces are being processed, friction sub-processes are employed to achieve self-induced heat generation. Compared with conventional spinning processes, this in-process heat treatment permits the extension of existing forming limits and allows more complex geometries to be achieved, together with defined, favourable part properties. The process thus holds a high potential for the manufacture of functionally graded workpieces, such as complex hollow parts made from tubes and sheets. In order to achieve functional gradation, i.e. to influence the material properties (strength or grain size) in a defined manner, it is essential to be able to set specific temperature profiles. It would be possible to influence these profiles by selecting appropriate process parameters like the feed rate, relative motion and the coefficient of friction. The process characteristics of friction-spinning make it eminently suited to tube processing. A further approach to the manufacture of parts with functionally graded areas is the use of sheet metal blanks as another semi-finished product. The paper will present the corresponding results of basic research into the manufacture of sheet metal parts with the aid of friction-spinning. Here, the influence of significant process parameters, forming strategies and tool systems on both the course and the outcome of the friction-spinning process will be shown. In addition, the differences and correlations that exist between tube and sheet processing will be described and discussed on the basis of parts made of tubes and sheets. These parts are manufactured by the friction-spinning process employing different process strategies and tool setups.

Model identification of the bundle thickness dynamics in drum friction spinning

The dynamics of the friction yarn formation process is described in terms of the dynamic behavior of the process state variables. Production efficiency and product quality of friction spinning are influenced by these process state variables. This study was performed with the intention of setting up a dynamic model based on mass balance in order to delineate the dynamic behavior of the cross-sectional area of the in-process bundle on the friction drum surface and to attain the distribution profiles of the cross-sectional area in transient state and in steady state as well. Then, simulation results were compared with those of the experiment, while the input variation was used as a test signal. Theoretical model shows that the bundle thickness on the friction drum has the dynamic characteristics of an integrating system with interval due to the finite length of the input fleece zone, and is in good correspondence with the results of the experiment. A periodic change in the fleece feeding rate led to the fact that there was a specific range of the fluctuation wavelength in the fleece feeding rate, whereas a change in the in-process bundle thickness completely disappeared or became locally maximized in certain wavelength areas. This could lead to a magnification or inaction of the perturbations with the corresponding wavelength in the bundle thickness; a bundle thickness irregularity. Experiments also identified that the theoretical model accurately described the fiber accumulation dynamics in a friction spinning process.

Manufacturing of complex functional graded workpieceswith the friction -spinning process

In recent years, the demands on lightweight constructions with respect to their functional qualities and their potential to save resources by reducing weight have increased significantly. Tailor-made components with functionally graded properties manufactured by a novel so-called friction-spinning process meet these demands very well. This new process combines elements from metal spinning and friction welding to a new thermo-mechanical process for the manufacturing of complex hollow parts made of tubes, profiles, or sheet metals. In the process a workpiece, for example a tube, is set into rotation in a conventional spinning machine while a pressure or friction plate works in axial direction on the tube end. In the contact zone the temperature increases strongly by friction. A further movement of the friction plate and optional supplemental forming tools allow the deformation of the warm material and the generation of the desired geometry. With this new process it is possible to extend existing forming limits and to produce complex geometries like flanges or hollow structures, which are not producible by conventional processes. Furthermore, it is possible to influence the workpiece properties or grain structure locally in a defined way. It is possible to realize intense grain refinement in the deformation zone during this thermo-mechanical forming operation.

Effects of yarn constitutions and fabric specifications on electrical properties of hybrid woven fabrics

Abstract This paper reports a fabrication method for conductive open-end friction core-spun yarn (OFCY), which, as described, are constructed from open-end friction spun yarn (OFSY) and core stainless steel wire (SW) combined within the yarn twisting zone of the friction drum during the open-end friction spinning process. To facilitate weaving of SW and reduce the material cost, initially, the sheath stainless steel (SS), Kevlar (KS) or rayon (RS) staple fiber and core stainless steel wire are combined to form the OFCY yarn by using a DREF III open-end friction spinning method. The OFCY yarns were successfully woven into a variety of woven structures produced from a semi-automatic loom. The primary objects of this research are to develop new conductive yarns and fabrics, which could be suitable for shielding home electronic devices, electrical appliances from electromagnetic fields. Such fabrics could be incorporated into prepreg systems used for composite manufacture. In these fabrics, SW is used as a core component that is wrapped around a sheath SS and KS or RS to form an OFCY yarn in which OFCY yarn strength remains the same and electrical properties are better than for an equivalent OFSY yarn. Stainless steel staple fibers (SS) and wire (SW) are incorporated as conductive fillers to enhance the electromagnetic shielding properties of the woven fabric. The electromagnetic shielding effectiveness (EMSE) of various woven fabrics was obtained using a coaxial transmission line holder in the frequency range of 300 kHz–3 GHz. The variations of EMSE, the surface and volume resistivities of the woven fabric structure, and blend ratios of the OFCY yarns are also described.

The Twisting Dynamic Analysis of Friction Spinning

The theoretical analysis of twisting in the yarn formation zone of the friction spinning process is presented in this paper. By setting up and solving the twisting dynamic differential equation of the forming yarn that has a variable diameter and is undergoing a linear drawing movement along its axis direction, we obtained the distribution rules of the twist and the rotation speed of the friction-spun yarn in its formation zone. The analysis showed that the twisting zone of the forming yarn undergoing friction spinning consisted of three parts: the tip of the taper; the thick end of the taper; and the cylinder region. The yarn twist reached its maximum at the exit point of the yarn on the friction roller, and the emerging yarn from the friction roller did not obviously rotate.

Fibre Behaviour in the Twisting Zone of a Friction-spinning Process

A simple model of a fibre landing in the twisting zone of a friction spinner is described. The effects of fibre properties, air flow in the feeding tube, landing angle, and initial fibre configuration on the shape of the fibre after landing are considered.

A Theoretical Approach to the Fundamental Relationships in the Friction-spinning Process

The friction-spinning process involves a number of parameters, some of which may be the key factors to which attention is directed during the design of a commercial spinning frame or in carrying out adjustments required to make it operate successfully. It is of primary importance to explore the essential relationships between all these main physical factors and particularly to have an exact knowledge of factors affecting the yam tension during yarn formation. For this reason, a study of this problem based upon the principle of conservation of energy in a system is made and an approximate equation derived to relate all the parameters involved.