摘要:

AbstractIn many engineering applications, elastomers are employed in multilayered and/or multicomponent composite structures. Rigid reinforcements are used to constrain the elastomer laterally, thus increasing the stiffness and load bearing capacity in the axial direction while retaining flexibility in other directions. Good, durable, adhesion is required between different elastomer layers and between elastomer and reinforcement to maintain these constraints. Owing to molecular characteristics, bonding processes for some elastomers can be spontaneous. Genuine spontaneity is exhibited in the phenomenon of tack when portions of the long elastomeric molecules interdiffuse across the interface between two contacting rubber surfaces. In addition,‘indirect spontaneity’can occur, e.g. when chemical bonding takes place between elastomer and brass plated steel wires at the same time as chemical crosslinks are formed between elastomer molecules during vulcanisation. Elastomers can be bonded to many substrates in various ways. Associated bonding mechanisms usually involve contributions from diffusion processes (of molecular portions, vulcanisation additives, adhesive or substrate constituents, etc.) and/or chemical reactions of widely varying form.MST/987

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.3.209

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractA computer assisted modelling method has been applied to determine the true grain size of a commercial WC–15Co (wt-%) alloy on the basis of measurements made on a two dimensional section. In the method, account is taken of the irregular grain shape of the grains, thus inaccuracies inherent to conventional grain size distribution analyses are avoided. The grain size distribution was found to be wider than predicted by theoretical grain growth models.MST/910

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.3.222

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractStrengthening in the pearlite of 0·75C–1·2Mn (wt-%) steels resulting from microalloying with 0·09–0·16% V was examined. The steels were transformed by controlled cooling in a dilatometer at an average transformation temperature of 600°C, which produced a pearlite interlamellar spacing of 0·11–0·12μm. Using electron microscopy no hardening precipitates in the as transformed specimens were revealed, but after additional aging V(CN) precipitates were observed. In the investigation of the hardening caused by V(CN) precipitation, a limiting value was found, which could not be increased by a further addition of V. The limit of the precipitation hardening is suggested to be a consequence of the limited amount of C and N dissolved in the ferrite, since no interphase precipitation occurred. The maximum hardness obtained was 400 HV20 and an increment of 75 HV20 (or 260 MN m−2in strength) was found in comparison with the comparable pearlite structure of a steel containing no V. From examination of the effect of the thermomechanically processed austenite structure on the pearlite morphology, it was found that transformation from fine grained unrecrystrallised austenite produced an ultrafine colony pearlite from which it can be stated that this transformation would result in improved toughness in pearlitic steels.MST/847

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.3.227

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractIt is still possible to optimise the newly developed continuous annealing process for sheet steel production with respect to the properties of the product. In the present contribution, the development of the texture under continuous annealing conditions (very rapid heating, short annealing time, and high annealing temperatures of intercritical range) has been investigated. The orientation distribution function method has been applied to study the detailed effect of the parameters and the underlying mechanisms. It is found that the important {111} recrystallisation components are strengthened on further annealing at higher subcritical or at intercritical temperatures. This is a result of the successive or simultaneous occurrence of oriented grain growth and partialα→γ→αorientation selective transformation. After complete austenitisation, the strong {111} fibre is weakened, which can be attributed to the operation of several crystallographic variants during the course of phase transformations. The transformation textures are calculated according to Bain (B) and Kurdjumov;amp;#x2013;Sachs (KS) and it is shown that the experimental transformation textures can be predicted by the B mechanism without variant selection or by the KS mechanism with variant selection.MST/838

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.3.238

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractHot extrusion of an AA 7178 based composite reinforced with alumina short fibres (FRM) was examined in the temperature range between 723 K (a solid state) and 773 K (a semisolid state). Although alumina fibres became well aligned along the extrusion direction for the entire temperature range, a higher extrusion temperature made the FRM stronger by suppressing the chopping of fibres during extrusion. The longitudinal tensile strength at 573 K was improved by 70% compared with the AA 7178 alloy with no reinforcement. Semisolid state extrusion, resulted in tears on the surface of the rod. To suppress tearing, a clad extrusion method involving an AA 6061 surface layer was developed. By this method, semisolid extrusion could be performed without tearing.MST/737

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.3.249

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractThe effect of soft additives (Pb, Bi) on the machinability of low carbon resulphurised free machining steels has been investigated using the plunge machinability test. The cutting and thrust forces and chip thickness were measured as a function of cutting speed in the steels having various contents of Pb and Bi. Unexpected results, such as very thick chips and formation of groove wear, were observed for 0·2%Bi at low cutting speeds. Such results have been attributed mainly to the lack of a stable built-up edge (BUE). As a result of these unexpected results, the effects of soft additives on various aspects of machinability differ depending on cutting speed. At high speeds, the effects of soft additives are in accordance with general understanding, i.e. machinability improves with increasing Pb or Bi content, with Bi being more effective. At low cutting speeds, some results very different from those at high cutting speeds were observed. It is obvious from these results that machinability test results may misrepresent the overall capability of steels when only a limited number of machining conditions are used. Finally, the observations made on the chips and theoretical considerations have suggested that liquid metal embrittlement by Pb or Bi could play a significant role in reducing the force in the secondary shear zone and in enhancing chip breaking. However, no definite conclusions can be made concerning whether or not the effective shear strength in the primary shear zone is reduced by liquid metal embrittlement. Solid metal embrittlement has been excluded from a possible mechanism in the primary shear zone.MST/870

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.3.255

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractA study has been carried out on the modification of ingot microstructure of commercial Al–Mg alloys by homogenisation treatments. A marked change in the hardness of the alloy ingots was produced after homogenisation. A relatively coarse distribution of the particles was produced by high temperature soaking. In the alloy of high Mn content (AA 5083), a non-uniform distribution of the precipitates was produced. An attempt was made to control this non-uniform distribution by varying the thermal sequences. Changes in the recrystallisation kinetics, the recrystallised structure of subsequent hot rolled material, and the recrystallised structure were also produced in these alloys after homogenisation.MST/843

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.3.268

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractIn this paper, electromagnetic induction bonding and ultrasonic welding are evaluated as two methods of bonding high strength, roll drawn polypropylene. In the first part, the use of electromagnetic induction bonding is considered. Joint regions had strength properties exceeding the cohesive strength of oriented polypropylene (OPP) material in the transverse direction. The percentage thickness of the disoriented region (the weld zone) was directly related to the reduction in tensile strength of parallel ply OPP laminates. In the second part, the use of ultrasonic welding using a range of tie layer materials is considered. Tie layers comprising ethylene–propylene copolymer (EPC) and small additions of amorphous polypropylene (APP) produced the most satisfactory results.MST/905

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.3.281

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractIn studies of the fracture surfaces of tensile, Charpy V-notch, and crack opening displacement (COD) fracture toughness specimens, taken from metal inert gas (MIG) welds fabricated in commercial purity titanium plate, an unusual form of fracture mode was observed. The feature took the form of shallow troughlike grooves and has been termed‘fluting’. By careful matching of the opposite faces of sectioned fractured specimens, and using stereofractography, it has been shown that the flutes consist of the ruptured halves of hexagonal shaped voids that formed before the final failure of the specimen. Titanium hydrides, which occur in the weld metal as impurities, have been used to show that there is a definite crystallographic relationship between the occurrence of flutes and the matrix. Although flutes were observed both with cleavage and with dimpled areas of fracture, they are the manifestation of a ductile fracture mode and form by a dislocation mechanism involving {1010}〈1210〉slip.MST/916

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.3.288

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractComputations using simplified mathematical models were performed to predict weld geometries and penetration depth for grooved butt joints in CO2welding. Weld metal geometry can be predicted within±10% accuracy using a fundamental equation derived from Wells' concept. From the computations, it was shown that the widest tolerance is obtained with root gap 1·3–1·8 mm at which the most flexible combination of welding parameters can be selected. The flank angle at the‘toe’can be calculated best using the circular arc model for I-butt joints and the normal distribution model for V-butt joints.MST/902

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.3.293

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor