2—HYGRAL CHANGES IN CURVATURE AND LENGTH IN SET KERATINS

The set developed in various wools and hairs when strained in boiling water or in monoethanolamine sulphite (MEAS) has been measured, together with the longitudinal swelling of set fibres on wetting. The changes in curvature of merino fibres on wetting are enhanced by setting in boiling water or in cold MEAS but diminished by setting in boiling 1% MEAS. The interpretation of these changes of curvature in terms of ortho–para differences throws into question the supposition that there is a specific para-type keratin (exemplified by human hair) and a specific ortho-type keratin (kid mohair). Some technological treatments diminish the hygral changes in curvature.     

7—STEELY (LOW-CRIMP,LOW-STRENGTH) AND DOGGY (LOW-CRIMP,NORMAL-STRENGTH) WOOLS—SOME NOTES ON PERFORMANCE

Steely wool has a low crimp rate and low strength and doggy wool a low crimp rate but normal strength, so that both wools are exceptionally useful experimental materials. An account is given in this paper of a comparison of the processing behaviour of wools of the two types with that of matched normal wools from yarn to fabric. The tensile properties and abrasion-resistance of the anomalous wools were as expected, but an unusual effect of the steely wool in washing shrinkage was found. The presence of steely-wool yarn in one direction (e.g., warp) caused increased shrinkage of the yam in the cross direction. Thus, in a fabric with a steely-wool warp yarn and a normal-wool weft yarn, the shrinkage index of the weft yam increased from 1.8 to 3.0; when the normal-wool yarn was used as warp with a steely-wool weft, the increase was from 1.7 to 2.4, This co-operative shrinkage did not occur with the doggy wool; it is thought to be caused by the low tensile modulus of the steely wool.     

37—THE AIR-FLOW FINENESS OF GREASY WOOL: INTER-LABORATORY TESTS OF A PROPOSED STANDARD PROCEDURE

An account is given of an inter-laboratory trial of a method of measuring the fineness of greasy wool by means of a Wira Air-flow Fineness Meter. Eight laboratories took part in two tasks: firstly, a calibration by each laboratory of its own air-flow meter in terms of internationally standardized wools; and, secondly, the measurement of the fineness of greasy-wool core samples by means of the specified method, which included a normal laboratory washing of the wool followed by opening on a wool-type Shirley Analyser.

As a result of the trial, the method was considered to be suitable for use by testing authorities, and tentative limits of precision of the method of measuring the fineness of greasy wool were established. The mean difference between any two laboratories ranged from 0.2 μm at 20-μm diameter to 0.5 μm at 28-μm diameter. This does not include sampling errors.     

Characterisation of subcritical crack growth in ceramics using indentation cracks

Abstract

The introduction of indentation cracks into brittle materials has proved to be a useful tool in characterising subcritical crack growth, notably in efficiently measuring the kinetic growth parameters and in defining whether the material exhibits a fatigue threshold. The accuracy of the subcritical crack growth parameters obtained using indentation mechanics can be excellent, provided the stress intensity factor associated with the indentation cracks is well characterised. Indentation cracks can also be used to measure crack velocity as a function of the applied stress intensity factor by direct observation. In such testing, it is critical that the changes in crack shape as the crack extends are known or accurately predicted. Numerical simulations suggest that the shape changes can be influenced not only by the testing geometry but also the growth kinetics. Finally, it is shown that the fatigue threshold can be determined by allowing median cracks to extend subcritically during indentation.     

Superconducting Bi(2223) thick film on Ba2HoNbO6: a new perovskite ceramic substrate

Abstract

Barium holmium niobate Ba₂HoNbO₆ (BHNO) has been developed as a new substrate for (Bi,Pb)₂Sr₂Ca₂Cu₃O_x (Bi(2223)) superconductor film. Ba₂HoNbO₆ has a cubic perovskite structure with lattice constant a = 8·26 Å. The dielectric constant and loss factor of this material are in a range suitable for its use as a substrate for microwave applications. The Bi(2223) superconductor shows no detectable chemical reaction with BHNO, even under extreme processing conditions. Dip coated Bi(2223) thick film on Ba₂HoNbO₆ substrate had T _c(0) of 109 K and current density of around 4 × 10³ A cm ^{- 2} at 77 K and in zero magnetic field.     

Mode I quasi–static and fatigue delamination characterisation of polymer composites for wind turbine blade applications

Abstract

Ambitious electricity generation targets from renewable sources set by many governments have lead to the rapid growth of the wind energy industry over the last two decades. The need for larger wind turbine blades for increasing energy generation has considerably increased the demand and use of high performance composites in wind turbine applications, mainly in blades. A common type of failure in composite materials is delamination of adjacent layers, which can occur either due to manufacturing inconsistencies or due to in service loads. Understanding and characterising delamination is very important in order to implement damage tolerant design methodologies. The present research work focuses on the assessment of the delamination behaviour of composites for wind turbine applications. Several composite systems were tested and their fracture toughness and fatigue delamination propagation behaviour under mode I (peeling) loading conditions were evaluated. Quasi–static tests were performed and delamination initiation values were evaluated. Fatigue delamination growth rate curves (da/dN versus G _Imax) were also produced. The carbon/epoxy and glass/epoxy material systems tested were compared in terms of resin type, fibre type and interfacial characteristics.     

Thermochemical surface treatment of titanium

Abstract

Titanium has very poor tribological properties. Various coatings can be used, for example, TiN, to improve them, but the loading is limited by the low strength of the substrate. Thermochemical treatments produce a layer that is sufficiently thick to support a load, but have to be carried out at high temperatures, 950 and 1050°C, for oxidation and nitriding processes respectively, degrading the core properties. An alternative treatment is desirable that could produce a substantive load bearing layer with good wear properties at 850°C or lower. The obvious candidate species were oxygen, nitrogen and carbon to form hardened diffusion layers, under a thin TiO₂, TiN or TiC surface layer. Nitrogen was not found to be sufficiently active at lower treatment temperature to have any beneficial effects and tended to block the diffusion of other species. Layers formed using various sources of nascent nitrogen, carbon and oxygen were studied. It was found that all the species forming hardened surface layers with the highest values of surface hardness and case depth (72 μm and 922 HV after 24 h at 850°C) were produced using carbon monoxide.     

Physical properties of mould powders for slab casting

Abstract

The application of mould powder for certain steel grades is mainly based on experience. In an ECSC project, an inventory was made addressing the physical properties that are the basis of this experience. It is concluded that, for each steel grade, common physical properties (e.g. viscosity, melting temperature) can be identified. There is, however, a large variation in the values of physical properties used. It is therefore not possible to find any relationship between slag properties and casting conditions, given the steel grade to be cast. Wider ranges in physical properties are possible and realistic to enable casting of a steel type at a particular speed.     

Simulation and experiment of curve irradiated laser bending process of titanium alloy sheet

Abstract

Laser bending along a curve scanning path is a complex 3D forming process. To analyse the deformation behaviour of the process and the effect of process parameters on the bending angle of sheets, numerical simulation becomes indispensable. In this paper, non-linear transient heat transfer and dynamic structural computational models including thermal mechanical coupling analysis, in which the temperature dependence of the thermal and mechanical properties of the material are taken into account, have been developed. The temperature, stress, and strain fields as well as the effect of process parameters on the bending angle were calculated on the basis of models using the finite element method. Meanwhile, an experimental parameter investigation was also carried out. The results showed that, compared with the linear laser bending, curve irradiated laser bending has a significant reduction of the bending angle and the bending angle decreases with increasing path curvature. The bending angle increases with increasing laser power and decreasing spot diameter, and decreases roughly with decreasing scanning velocity. Good correlation was found between the numerically simulated results and the experimental data.     

Influence of carbon on aging response and tensile properties of eutectoid beta titanium alloy Ti–13Cr

Abstract

The influence of carbon addition on the aging response of quenched Ti–13Cr (wt-%) has been investigated using hardness tests, tensile tests, optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It has been found that carbon refines beta grain size, leads to fine and homogenous alpha precipitation and reduces grain boundary alpha. The carbon addition accelerates the rate at which hardening occurs during aging and increases the peak hardness of the aged specimens. A significant improvement in room temperature tensile strength and ductility has also been achieved in the carbon containing alloy after aging at 500°C. The effects of carbon on the aging response appear to be attributed to dislocations introduced by carbides during quenching, elastic strain created in the matrix by carbides and gettering effect of Ti₂C carbides. The influence of each of those mechanisms has been demonstrated through experiments and the factors giving rise to the improvements in properties are also discussed in terms of the microstructural observations.