Friction Press Research Articles

A Study on the Bond Strength of Plastic–Metal Direct Bonds Using Friction Press Joining

Friction press joining (FPJ) is an innovative joining process for bonding plastic components and metal sheets without additives in an overlap configuration. This paper focuses on the resulting bond strength. Tensile tests showed that the direct bonds produced by FPJ have either an equivalent or a higher bond strength compared to adhesive bonds. For the material combination of HD-PE and EN AW-6082-T6, an equivalent bond strength was achieved. In contrast, for the material combinations PA6-GF30 with EN AW-6082-T6 and PPS-CF with EN AW-2024-T3, higher tensile shear strengths were achieved via the FPJ technology. In addition to the technical considerations, this paper presents an evaluation of the technological maturity of FPJ. It was found that the basics of the technology are already well developed, and prototypes for showing the applicability have already been manufactured. The last part of this paper deals with the classification of FPJ into the standard for manufacturing processes, according to DIN 8593. The authors suggest a categorization into Activation bonding (item 4.8.1.3). These investigations show the high technical potential of FPJ for joining plastic components with metals.

A Holistic, Model-Predictive Process Control for Friction Stir Welding Processes Including a 1D FDM Multi-Layer Temperature Distribution Model

Friction press joining is an innovative joining process for bonding plastics and metals without additives in an overlap configuration. This paper presents for the first time a model-based approach for designing a multi-variable model predictive control (MPC) for friction press joining. For system modeling, a differential equation based on the heat flows was proposed and modeled as a torque-dependent function. With this model, it is possible to consider cross-effects between the axial force and the friction zone temperature. With this theoretical approach, adaptive model-predictive process control was implemented and validated for different material combinations (EN AW-6082-T6; EN AW-2024-T3; PE-HD; PA6-GF30; PPS-CF). It could be shown that the MPC has excellent control accuracy even when model uncertainties are introduced. Based on these findings, a 1D Finite Differential Method multi-layer model was developed to calculate the temperature in the plastic component, which is not measurable in situ (r = 0.93). These investigations demonstrate the high potential of the multi-variable MPC for plastic-metal direct joining.

Improving of closed die-forging of transport and marine fasteners “wing nut”

The “wing nut” is a widespread transport and ship fixture designed to locking of hatches, covers and portholes. A more advanced closed die forging for the “wing nut” forgings of transport fittings was proposed with preforming by new method of bulk buckling of billet with upsetting ratio (height to diameter ratio) of 4.2...4.4. The billet and process calculation were performed based on results of researched and a new die forging was tested on a screw friction press. The results of experimental studies conducted on model lead billets at room temperature, and steel billets heated to 1180 °C, confirmed the increase in the accuracy rate of the billet material utilization ratio (one forging mass to one billet mass ratio) from 0.519 to 0.734 and metal savings up to 41% in comparison with the basic die forging without preforming of billet. It is shown that the introduction of a preforming by bulk buckling operation improves the forgings macrostructure (grainflow) even for cases the initial billets are buckled to folding defect formation, because with the further finishing die forging of semi-finished work-pieces the folding defect is displacing (or extruding) into flash. The improved die forging process and recommendations are accepted for implementation in the industry and the direction of reducing the cost of repair work for transport is noted.

Design, evaluation, and implementation of a model-predictive control approach for a force control in friction stir welding processes

Friction press joining is an innovative joining process for bonding plastics and metals without additives in an overlap configuration. A model-based approach for the design of an axial force controller for friction press joining is presented in this paper. A closed-loop control was set up on the machining center, in which the plunge depth was used as the controlling variable. In order to support the controller development, a nonparametric dynamic process model was developed via a data-based system identification. Subsequently, various control concepts were designed off-line and verified on the actual system. The most promising ones, a proportional controller, a controller created with the pole placement method, and a model predictive controller, were selected for further investigations. The three controllers were re-evaluated and compared by means of a defined input of disturbance variables and reference variables. The model predictive control (MPC) approach as well as the proportional controller were also tested for model uncertainties. For this purpose, different material combinations were joined using the different controllers. Thereby, it was shown that the MPC controller resulted in smaller standard deviations when encountering large model uncertainties. The investigations demonstrated the high potential of friction press joining of plastic components with metals. The results form the basis for future research, whereby the force can be specified as an additional input parameter instead of the plunge depth.

Influence of the laser-based surface modification on the bond strength for friction press joining of aluminum and polyethylene

Friction press joining is an innovative joining process for the production of plastic-metal joints without additives, in an overlap configuration. In order to achieve a high bond strength, the metallic joining partner is pretreated with laser radiation. Subsequently, heat is induced by friction and pressure during the joining process, causing the thermoplastic material to melt and adhere to the metallic joining partner. In this work, the temperature distribution during the process in the composite is analyzed and characterized. It was found that the occurring temperatures and temperature differences are not only dependent on the rotational speed, but also on the feed rate. It is also shown that the friction surface temperature can be used as an indirect control variable for a model-based, closed-loop control. Based on these findings, various surface modifications forthe metallic joining partner were investigated and analyzed with regard to the maximum strength of the joint. It was observed that the highest tensile shear strength can be achieved with a quasi-chaotic nano structure. In addition, the joining compound was characterized by a thin section, facilitating the identification of specific zones in the joint. These investigations show the high potential for friction press joining of plastics and metals, and form the basis for a model-based control of the joining zone temperature.

Short-Cut Method to Assess a Gross Available Energy in a Medium-Load Screw Friction Press

The present study proposed a rapid method, based on a previous universal compression tests, to estimate the required load capacity to cold forge different specimen quantity in a screw press. Accordingly, experimental and theoretical approach are performed to check new adjustable drive motor of the modified forging machine to achieve a gross available energy to deform the specimens preventing damage of the forging machine. During the forging experiments, two screw friction presses (as-received and modified) are used to validate the theoretical approach. The modified press exhibits an increase of 51% of gross energy and 11% of maximum load capacity compare to the as-received press. This method is used to improve the effective of the forging process avoiding excessive loads that could promote machine failure. Therefore, a low-cost and easy to implement methodology is proposed to determine the energy and load capacity of a screw friction press to forge different specimen quantities with symmetry pattern configurations.

Multi-field coupling finite element analysis for determining the influence of temperature field on die service life during precision-forming process of steel synchronizer ring

Failure analysis shows that increased die temperature caused by severe plastic deformation of material and heat conduction between hot billet and cavity significantly affects the distortion of gear cavity in steel synchronizer ring forging process. The forging process of steel synchronizer ring and die temperature distribution under different forging conditions are analyzed through finite element method. Simulation results show that severe plastic deformation occurs in the gear cavity. The improvement of lubrication condition results in decreased die temperature. When the initial billet temperature is high, the die temperature is also high. Increasing forging speed in a certain range facilitates the die temperature decrease. The distribution of die temperature in synthetic forming technology is more reasonable than that of one step forging. The synthetic forming technology is adopted in production to reduce the effects of severe plastic deformation caused by die temperature. The ejection mechanism and control system of the double disc friction press are improved to reduce the contact time between the hot billet and cavity. Experimental results show that synthetic forming technology is reasonable, and that the die service life is prolonged.

Friction Press Joining of Laser-Texturized Aluminum with Fiber Reinforced Thermoplastics

Friction Press Joining (FPJ) is a suitable method for producing composites of aluminum and thermoplastics in lap joint configuration, which is based on modified Friction Stir Welding (FSW). During the joining process, a rotating cylindrical tool is pressed onto an aluminum surface. The resulting friction generates heat that is conducted to the bonding zone, leading to localized softening of the thermoplastics. In combination with the tool’s axial force and a suitable pre-treatment of the aluminum surface, a resilient composite compound is created. This paper presents the results of a surface pre-treatment of aluminum using laserradiation. The textures are essential for a strong connection, as they can significantly influence effective joining mechanisms, such as microscopic and macroscopic form fit. The experiments were carried out using different surface treatments by means of a single-mode laser for joints of aluminum (EN AW-6082 T6) and glass fiber reinforced polyamide (PA6 GF15). The aim of the study was an increased understanding of process behavior and joining mechanisms. The shear strength could be increased by 40 % compared to previous studies with the presented laser surface treatment.

Analysis of the Bonding Behavior and Joining Mechanism during Friction Press Joining of Aluminum Alloys with Thermoplastics

Friction Press Joining (FPJ) is a joining process for the production of multi material combinations of aluminum alloys and (fibre- reinforced) thermoplastics in lap joint configuration. It is based on a modified Friction Stir Welding (FSW) process. This study investigated the influence of the main process parameters (axial force, rotational speed, feed rate) of FPJ on the bonding behavior and joining mechanisms of glass fiber reinforced polyamide 6 with the aluminum alloy EN AW-6082.

Laser-generated Macroscopic and Microscopic Surface Structures for the Joining of Aluminum and Thermoplastics using Friction Press Joining

Structural lightweight construction is increasingly utilized in the aerospace and automotive industry. Hybrid structures have great potential, especially with regard to load-specific component layouts. Usually, a surface pre-treatment is applied prior to joining dissimilar materials to improve bonding mechanisms such as form closure. In previous studies pulsed wave (pw) lasers were used for structuring metals. This paper presents the results of aluminum pre-treatment via a continuous wave (cw) single-mode fiber laser: macroscopic and microscopic structures were generated on the aluminum surface; the samples were joined with glass fiber reinforced polyamide using Friction Press Joining (FPJ), a method for joining metals and thermoplastic polymers in lap joint configuration. Using these new methods for surface structuring, shear strength was increased by 40% compared to previous studies with pw lasers.

Study on the Rules and Effects of Wear on Die Service Life in Steel Synchronizer Gear Ring Forging Process

The die accuracy and die service life reduce due to die wear during precision forming processes of steel synchronizer gear ring. The most serious part of wear is the middle between two tooth shapes. The rules of the wear and initial die hardness and frictional coefficient are analyzed based on numerical simulation. It shows that the higher of the initial die hardness, the better antiwear and good lubrication is benefit to reduce wear and prolong the die service life. The effect of the temperature on die life is reflected through hardness. The relationship of die hardness and die temperature, forming time is deduced. The higher of the die temperature and the longer of the forging time, the more serious of die wear. To prolong the die life and improve the quality of forgings, the synthetic forming technology is adopted and the ejection way and control system of the Plate Friction Press are improved. Experiment verification shows that the die service life has been prolonged.

Mechanics of continuous equal-channel angular extrusion

The paper discusses possible approaches for realization of continuous equal-channel angular extrusion (ECAE). A practical interest presents Conform ECAE (CECAE) converting an inlet channel into a friction press. Slip line solutions and plastic zones are analyzed for different cases of active and passive frictions. It is shown that CECAE provides lower extrusion pressure, higher effective strains and better approximation to simple shear deformation mode than ordinary ECAE. Specific distributions of plastic friction depending on a slip between material and roll are introduced for the beginning stage, steady CECAE and during slippage. The paper describes a few designs of CECAE. Optimization of the main characteristics is performed for the concept of CECAE with an additional coining roll.

Materials based on highly concentrated ceramic binding suspensions (HCBS). Evaluation of methods for molding bauxite ceramic concretes

The processes of molding and vibromolding of laboratory samples and large-sized nested blocks for intermediate ladles are studied using bauxite mixtures of the same composition. The ceramic concretes obtained exhibit comparable porosity and strength characteristics, namely, substantial starting strength, significant strengthening upon low-temperature heat treatment, and insignificant shrinkage in service. An effect of substantial grinding of the bauxite filler in the structure of the mold is found even under conditions of a relatively low (25 MPa) molding pressure for nested-block molding on a friction press.

Semiautomatic batching and pouring compound into molds on a friction press

Semiautomatic batching and pouring compound into molds on a friction press

Mechanizing removal of dinas from a friction press

Mechanizing removal of dinas from a friction press

Fail-safe device for the yoke of the friction press

Fail-safe device for the yoke of the friction press

Automating friction press working for ceramics manufacture

Automating friction press working for ceramics manufacture