Warm powder compaction substitutes conventionally double pressed and double sintered synchroniser hubs

Abstract

Within a project supported by the European Union a consortium consisting of the companies Fraunhofer Institute for Structural Durability LBF, AMES, Miba, GKN, Federal Mogul, Höganäs, RWTH Aachen, Peugeot/Citroën and Fiat worked on the realisation of heavyduty gearbox components by warm powder compaction technology. In this paper, part of this work will be reported, namely the manufacturing of synchroniser hubs by this new technology. Until now these hubs were manufactured by the double pressing and double sintering route.

Based on service load measurements in a gearbox of a Peugeot 506, vehicle fatigue tests were carried out with conventionally and warm pressed hubs. The results of fatigue tests with hubs as well as the durability tests carried out in the gearboxes of Peugeot/Fiat revealed the same performance for both technologies. As a consequence, the hubs produced by warm powder compaction can substitute for the ones produced conventionally. Further, the new technology reveals economic advantages with regard to the powder price as well as production costs.     

Fast sinter crystallisation of waste glasses

Abstract

Two glasses, belonging to the CaO–Al₂O₃–SiO₂ system and corresponding to the melting of mixtures of industrial wastes (recycled glasses, mining residues, ashes, asbestos containing cements, etc.), have been successfully converted into dense glass ceramics by sintering with concurrent crystallisation. The usage of fine glass powders (<37 μm) allowed very short sintering treatments, due to the enhanced nucleating activity of glass surfaces. In particular, dense glass ceramics could be produced by direct insertion of pressed glass powders in the furnace at the sintering temperature, followed by rapid cooling at room temperature after a 30 min holding time. The proposed approach evidences the feasibility of sintered glass ceramics by the fast and economic processes employed for traditional ceramics, with the advantage of superior mechanical properties (bending strength exceeding 100 MPa, Vickers' microhardness exceeding 6 GPa). Like in traditional ceramics, clay and water could be used for the shaping of pressed tiles, thus posing the conditions for massive industrial production.     

Bright zinc–nickel alloy deposition from alkaline non-cyanide bath

Abstract

Zinc–nickel alloy deposition with polyvinyl alcohol and piperonal as bath additives has been investigated. The effects of additive concentration, triethanolamine concentration and other parametric variables on the deposit and solution properties have been studied. Polarisation studies were carried out under different conditions to understand the effect of triethanolamine and the brighteners on the co-deposition. Results indicated that the additives lead to bright alloy deposition containing ～10% nickel. The deposit produced at the optimum conditions with the additives has a nanograined structure with a γ phase.     

Effect of Structural Parameters on the Thermal Stress of a NiFe2O4-Based Cermet Inert Anode in Aluminum Electrolysis

Inert anode has been a hot issue in the aluminum industry for many decades. With the help of FEA(finite element analysis) software ANSYS,a model was developed to simulate the thermal stress distribution working condition of an inert anode. To reduce its thermal stress,the effect of some parameters on the thermal stress distribution was investigated,including the anode height,the anode radius,the hole depth,the hole radius,and the radius of inner chamfer and outer chamfer. The results showed that in the actual working condition of an inert anode,there existed a large axial tensile stress near the tangent interface between the anode and bath,which was the major cause of anode breaking. Increasing the anode height and reducing the hole depth properly seemed to be beneficial for the stress distribution. With the increase of anode radius,the stress distribution became better first and then deteriorated,the reasonable value was between 0.045 to 0.06m. The hole radius had a significant effect on the stress and a smaller radius would reduce the thermal stress. The effect of the radius of the inner chamfer and the outer chamfer was less than other parameters.     

Liquid crystalline adhesives for polypropylene joints

This study was devoted to the investigation of the adhesion of epoxy resins to polypropylene adherends. In particular, the study was carried out as follows: synthesis of both a liquid crystalline (LC) and a bisphenol-A-based resin, their characterization and their further evaluation as adhesives for polypropylene adherends. This was done in order to evaluate the difference between an LC epoxy resin and an isotropic one in adhesive applications. The adherends chosen were neat polypropylene (PP) and polypropylene reinforced with 20 and 40 wt% talc (PP20 and PP40, respectively). The effect of two different pre-treatments (simple degreasing and acid etching) on the polypropylene adherends was also evaluated. It was shown that the adhesion strength of the liquid crystalline adhesive was higher compared to that of the isotropic one. The higher adhesion was related to the extra ductility demonstrated by the LC epoxy resin, which was due to its particular microstructure. Moreover, the acid etching pre-treatment performed on polypropylene adherends prior to bonding improved the adhesion at the interface with the resin. The increased stiffness of the adherends due to the presence of talc turned out to be beneficial to obtain more resistant joints.     

Effects of strain aging on the structure and mechanical properties of PM 92·5W–5Ni–2·5Fe heavy alloys

Abstract

This paper describes the effects of strain aging on the mechanical properties and the microstructure of forged 92·5W–5Ni–2·5Fe and its heavy alloys microalloyed with cobalt. The investigation was performed on cold rotary forged rods deformed 15, 20 and 30% and strain aged at temperatures from 673 to 1273 K for 1·8–32·4 ks. The results show that for these alloys, there is a temperature range from 773 to 873 K in which maximum ultimate strength and hardness can be attained. Furthermore, the strain aged alloys have shown strength and hardness increase at a temperature of 973 K in a time period of 10·8 ks. The fracture analysis has shown the presence of predominant transgranular fracture of the tungsten phase and γ-phase in the strain-aged alloys in comparison with the forged alloys. The results indicate that interface and tungsten phase strengthening are predominant mechanisms of strain aging.     

Effect of alloying elements on properties and microstructures of Ti–V–Cr burn resistant alloys

Abstract

Burn resistant Ti alloys have been developed over the last 10 years. The aim of the present paper is to study the effects of alloying elements on properties and microstructures of Ti–V–Cr burn resistant alloys. The alloys Ti–35V–15Cr, Ti–25V–15Cr, and Ti–25V–15Cr–3Al usually show simple β phase structures, and recrystallisation finishes at 800°C. The Ti–25V–15Cr alloy has good workability, tensile properties, and thermal stability compared with the Ti–35V–15Cr and Ti–25V–15Cr–3Al alloys. There are α precipitates in the Ti–25V–15Cr alloy after exposure at 500°C for 100 h, which leads to a decrease in the thermal stability.     

Durability of metal joints bonded with aluminium powder filled epoxy adhesive

Abstract

Durability of the metal joints bonded with aluminium powder filled epoxy adhesive was investigated by measuring the joint strength by the single lap shear test before and after exposure to distilled water and the hot and humid Arabian Gulf atmosphere. Fractured specimens were examined by photography. The epoxy adhesive retained its strength with as much as 50 wt-% addition of aluminium filler. Moreover, varying the Al filler content in the adhesive did not have a significant effect on adhesive behaviour in either of the two environments studied. Exposure to atmosphere for as long as 6 months did not cause a deterioration of strength for metal joints bonded with aluminium powder filled epoxy. They failed almost completely within the adhesive, similar to the cohesive mode of unexposed specimens. However, a significant strength decrease was observed in adhesive joints after exposure to distilled water for 6 months. The joints failed in more than a single mode. The interior part of the adhesive lap area failed in cohesive mode while an adhesion failure mode was observed near the edges of the adhesive lap area, which is believed to be a result of moisture diffusion through the edges.     

Effect of thermal treatment of wood lumbers on their adhesive bond strength and durability

Wood used in outdoor applications needs to undergo either chemical or thermal treatment to improve its decay resistance. Thermal treatment permits to avoid the use of toxic chemicals, increases the dimensional stability and gives a dark color to the wood. However, this process deteriorates the mechanical properties of wood, i.e., the wood becomes more fragile and rigid. The chemical transformation of wood that takes place during the heat treatment changes the interaction between the wood surface and the adhesive. In this work, the interfacial bonding strength (the resistance to the shear stress by compression in parallel direction to the glued interface) and cyclic delamination (resistance to delamination during accelerated exposure) for different wood species and adhesives were tested in accordance with the ASTM D2559 standard. Four wood species: scott pine (Pinus sylvestris), aspen (Populus tremuloides), yellow poplar (Liriodendron tulipifera) and jack pine (Pinus banksiana) both treated and non-treated, and two structural adhesives, phenol resorcinol formaldehyde (PRF) and polyurethane (PUR), were used in the testing. Among the studied species, jack pine is found to be the easiest to bond, while aspen is found to be the most difficult. With the wood species and adhesives evaluated in this study, non-treated wood is found to provide a better bonding strength than the treated wood.     

Modeling of cohesive failure processes in structural adhesive bonded joints

This paper presents an approach to predicting the strength of joints bonded by structural adhesives using a finite element method. The material properties of a commercial structural adhesive and the strength of single-lap joints and scarf joints of aluminum bonded by this adhesive were experimentally measured to provide input for and comparison with the finite element model. Criteria based on maximum strain and stress were used to characterize the cohesive failure within the adhesive and adherend failure observed in this study. In addition to its simplicity, the approach described in this paper is capable of analyzing the entire deformation and failure process of adhesive joints in which different fracture modes may dominate and both adhesive and adherends may undergo inelastic deformation. It was shown that the finite element predictions of the joint strength generally agreed well with the experimental measurements.