The behaviour of braided hydraulic hose reinforced with steel wires

Measurements are reported of the variation with pressure of the elastic strain in the wires of the outer braid of a two-braid high pressure hydraulic hose. Strain measurements were made with a Solex pneumatic extensometer. The performance of the extensometer was checked by comparing the measured and calculated strains for the wires in a single braid hose. Good agreement was found.Surprisingly little hysteresis was observed in the wire tensions on loading and unloading. Hysteresis in the length changes of the hose was more marked. Measurement of the relative displacement of the edges of adjacent tapes of wires led to the conclusion that frictional forces at the points where braid wires cross is a major source of hysteresis.An analysis is presented which was used to calculate both the elastic strains in the braid wires and the length change of the hose on pressurisation. The analysis takes account of the compressibility of the rubber between the two braids but ignores constraints arising from friction or from the rubber. The measured strains and length changes agreed sufficiently well with the predicted values to justify the use of the analysis for hose design. Using this analysis, information is assembled about the effect of braid angle on wire tensions and length change; this leads to a proposal for the ideal values of the inner and outer braid angles in a particular case.     

Solid particle erosion of CFRP composite with different laminate orientations

The solid particle erosion behavior of epoxy base unidirectional and multidirectional carbon fiber reinforced plastic composites was investigated. The erosion rates of these composites were evaluated at various impingement angles (15–90°) with a particle velocity of 70 m/s. Irregular SiC particles with an average diameter of 80 μm was used. The dependence of impingement angle on the erosive wear resembled the conventional ductile behavior with maximum erosion rate at 15–30° impingement angle. The erosion rate of unidirectional composites at acute impingement angle was higher for [90] than for [45] and [0] while the difference disappeared at normal impingement angle (90°). On the other hand, the erosion rates of multidirectional laminated composites ([0/90], [45/−45], [90/30/−30] and [0/60/−60]) were not much influenced by the fiber orientation except for 15° impingement angle.     

Erosive wear by silica sand on AISI H13 and 4140 steels

The erosive wear behaviour of AISI H13 tool steel and AISI 4140 steel has been investigated in this work using a sand blast-type rig. Samples of six different hardness levels (from annealed to 595 HV) were produced and subsequently tested using silica sand as the erodent material at impact angles ranging from 10° to 90°, air drag pressures of 0.689 and 1.38 bar (10 and 20 psi respectively), impact speeds ranging from 70 to 107 m s⁻¹ and various particle sizes. Results of erosion versus impact angle at different hardness levels showed three distinctive wear regions: (i) for impact angles of 10° and 20°, the amount of wear was higher at lower hardness values; (ii) for impact angles of 30° and 40° no significant changes were found in the amount of wear despite the increase in hardness; (iii) for impact angles of 60°, 75° and 90° the amount of wear was higher for higher hardness levels in the eroded material. Single curves showed typical ductile behaviour of these alloys, a transition towards brittle behaviour for the hardest specimens was also observed due to the formation of adiabatic shear bands. SEM analysis was conducted to identify the erosion mechanisms for each type of behaviour.     

Onset of matrix cracking in angle-ply ceramic matrix composites

The problem of initial damage in angle-ply [−θ_m/0_n/θ_m] and [−θ/θ] ceramic matrix composites subjected to axial tension is considered in this paper. The damage is in the form of matrix cracks that may appear in either inclined (−θ and θ lamination angle) or longitudinal layers. As follows from the analysis, if the lamination angle of the inclined layers is small, the initial failure occurs in the 0-layers of [−θ_m/0_n/θ_m] composites or in [−θ/θ] composites in the form of bridging cracks. However, if the inclined layers form a larger angle with the load direction, they fail due to tunneling cracks. It is shown that the boundary between two different modes of failure in a representative SiC/CAS composite corresponds to a lamination angle equal to 35° in the case of [−θ_m/0_n/θ_m] composites. In the case of [−θ/θ] laminates, the boundary value of the lamination angle is equal to 45°, i.e. bridging cracks form if θ<45° and tunneling cracks appear if θ>45°.     

The response of wire rope strands to axial tensile loads—Part II. Comparison of experimental results and theoretical predictions

Carefully instrumented tests were performed on straight single steel strands of seven-wire construction subjected to axial loads and with various end restraints. The strands have a practical range of lay angles between 9.2 and 17.0° with core and helical wire diameters of 3.94 and 3.73 mm, respectively. A mathematical model of a strand was developed to explore the change of helix angle under load, Poisson ratio effects in wires, wire flattening under interwire pressure and the effect of friction between the core and helical wires. A companion article (Part II) [Int. J. Mech. Sci. 29, 621–636 (1987)] compares the theoretical predictions with previously published analytical work and with the corresponding experimental results reported in this article.     

The high strain rate compression of 7039 aluminium

Aluminium alloy 7039 was compressed at strain rates between 2 × 10³ and 2·5 × 10⁴s⁻¹ using a modified Hopkinson bar. At strain rates between 2 × 10³ and 1·2 × 10⁴s⁻¹ there was a linear relationship between the flow stress and strain-rate with a slope corresponding to a macroscopic viscosity of 2·9 kPa s. At strain rates between 1·2 and 2·5 × 10⁴s⁻¹ there was a levelling out of the flow stress, but the data was too scattered to give a definite trend. Due to the opposing effects of linear work-hardening and adiabatic heating, at strains above 0·15 the specimens work-softened at a rate inversely proportional to the square root of the strain rate. At the higher strains, specimens cracked along the dominant adiabatic shear band formed during the compression.     

A full factorial investigation of the erosion durability of automotive clearcoats

A full factorial experimental investigation has been carried out into factors affecting the resistance of a commercial acrylic/melamine automotive clearcoat to erosion by silica sand particles. The factor variables and their ranges were: particle size 125–425 μm; temperature 30°C–65°C; impact angle 30°–90°; particle velocity 35 m s⁻¹–55 m s⁻¹; and the baking process applied to the coating. An empirical linear regression model for the erosion response of the coating with R²_adj=97.5% was generated from the data. The regression coefficients of this model quantify the relative strengths of the effects of each of the factors. Several interactions between the factor variables were identified. In particular, the glass transition of the coating, which occurs at 40°C, has a significant effect on its response to erosion. The study has allowed the combinations of conditions that would be of most concern for automotive paint users to be identified.     

The ricochet of spherical projectiles off sand

Plough development with time has been studied for the ricochet of 1 in. dia. spherical projectiles off sand for various entry speeds 0(10²) m/sec but with a fixed initial impact angle of 15°. Results show that retardations, of the order of 10⁵ m/sec², are associated with the penetration phase and that instantaneous longitudinal retardations are proportional to velocity squared; in the ascending phase retardations are very much smaller and the speed almost constant.The critical angle of ricochet is also shown to depend slightly on speed. For a 0·5 in. ball the critical angle reduces from 20° at 100 m/sec to 18° at 375 m/sec.     

Force, torque and plastic flow analysis in rotary upsetting of ring shaped billets

The orbital upsetting of rings has been analysed for a Mises material by using an upper bound approach. Forging forces, rocking die torques and ring profiles are calculated at each step of the process. Experiments are described in which rings made of 1045 mild steel, 52100 chromium alloyed steel and 316 stainless steel are upset at room temperature on a 1.6 MN rotary press. The main parameters are: orbital oscillation angle, 2°, upper die oscillations, 200 min⁻¹ and lower die speed, 4.10 mm s⁻¹. An experimental rocking die placed on a conventional testing machine has been used for the rotary upsetting of rings made of Plasticine as model material. The simulation parameters are: oscillation, 2°, upper die oscillations, 40 min⁻¹, speed, 98.4 mm min⁻¹. The theoretical values of forging forces, rocking torques, and ring profiles are in keeping with the experiments. So the proposed upper bound approach may be considered as a good model for rotary upsetting.     

The measurement of the axial internal stress in steel wire

Apparatus is described for the measurement of the approximate axial internal stress distribution in wires typically 0·3–0·4 mm diameter. A sensitive optical system measures the change of length of the wire as its diameter is reduced at a rate of about 0·3 μm per minute by dissolution in 0·012 M nitric acid maintained at a constant temperature. The change of area of cross section of the wire is deduced from measurement of its electrical resistance. The adoption of a continuous thinning process makes it possible to measure the internal stress at the original wire surface. The method is not able to take account of the effect on the axial strain of the relief of circumferential and radial stresses. This leads to the axial stress being underestimated by about 30%. Internal stress measurements are reported on patented and drawn steel wire which confirm the wide range of internal stress intensity that can be generated in this material by changing and drawing conditions.     

Studies of high temperature sliding wear of metallic dissimilar interfaces II: Incoloy MA956 versus Stellite 6

The development of wear surfaces formed during limited debris retention sliding wear of Incoloy MA956 against Stellite 6 between room temperature and 750 °C, and sliding speeds of 0.314 and 0.905 m s⁻¹ (7 N applied load, 4522 m sliding distance) were investigated. At 0.314 m s⁻¹, mild oxidational wear was observed at all temperatures, due to oxidation of Stellite 6-sourced debris and transfer to the Incoloy MA956; this debris separated the Incoloy MA956 and Stellite 6 wear surfaces. Between room temperature and 450 °C, the debris mainly took the form of loose particles with limited compaction, whilst between 510 °C and 750 °C the debris were compacted and sintered together to form a Co–Cr-based, wear protective ‘glaze’ layer. The behaviour was identical to that previously observed on sliding Nimonic 80A versus Stellite 6 at 0.314 m s⁻¹.At 0.905 m s⁻¹, mild oxidational wear was only observed at room temperature and 270 °C and dominated by Incoloy MA956-sourced debris. At 390 and 450 °C, the absence of oxide debris allowed ‘metal-to-metal’ contact and resulted in intermediate temperature severe wear; losses in the form of ejected metallic debris were almost entirely Incoloy MA956-sourced. This severe wear regime was also observed from 510 up to 630 °C, but increasingly restricted to the early stages of wear by development of a wear protective Incoloy MA956-sourced ‘glaze’ layer. This ‘glaze’ layer formed so rapidly at 690 °C and 750 °C, that severe wear was all but eliminated and wear levels were kept low.The behaviour observed for Incoloy MA956 versus Stellite 6 at 0.905 m s⁻¹ contrasts sharply with that previously observed for Nimonic 80A versus Stellite 6, in that the Incoloy MA956-sourced high Fe–Cr debris formed a protective oxide ‘glaze’, whilst the Nimonic 80A-sourced Ni and Cr oxides formed an abrasive oxide that at high sliding speeds assisted wear. The data indicates that the tendency of oxide to form a ‘glaze’ is readily influenced by the chemistry of the oxides generated.     

Numerical investigation of deformed layout and fatigue life of automotive braking hose to the helix angle of fabric braided layers

The fabric braided rubber hose used in the automotive hydraulic braking system exhibits the anisotropic large deformation while its movable end is moving along the cyclic path during the steering and bump/rebound motions of vehicle. The complicated large deformation may cause not only the interference with other neighboring parts but also the durability problem resulting in the fatal micro cracking. In this regard, the design of high-durable braking hose with the interference-free layout becomes a hot issue in the automotive industry. However, it has been traditionally relied on the cost-/time-consuming trial and error experiments because the computational methodology for the large deformation and fatigue evaluation of the braking hose with the fabric braided layers in complex micro structure pattern has not been fully developed. Furthermore, the hose deformed layout and fatigue life are significantly influenced by the helix angle of braided layers, so that their characteristic investigation becomes an important research subject. As a preliminary step for the optimum design of high-durable and interference-free braking hose, this study investigates the hose deformed layout and the fatigue life cycle with respect to the helix angle of braided layers.

     

Micro-Raman depth analysis of residual stress in machined germanium

Raman spectroscopy has proved to be a useful nondestructive technique for measuring residual stresses in semicondutors. The Raman microprobe is used to investigate the effects of machine parameters on residual stresses in single point diamond turned germanium (Ge). A profiling technique that provides a method of obtaining the residual stress information as a function of depth with depth resolutions of 10.0 nm is discussed. This method is used to analyze the asymmetrically broadened and shifted spectral features in the machined samples. Residual stresses are sampled across ductile feed cuts in (100) Ge wafers, which were single point diamond turned using various feed rates (12.5, 25 nm/rev), rake angles (0°, −10°, −30°), and clearance angles (6°, 16°). In general a region of plastically deformed material that shows slight compressive stresses exist near the surface of the diamond turned sample. The compressive surface stress increases to a maximum at a depth of ≈ 50 nm beneath the surface at which point the stress rapidly changes sign. The rapid sign change is indicative of the transition from plastic to elastic deformation. Deeper probe regions exhibit increasing tensile stresses, which reach a maximum and then relax to zero at greater depths in the sample. A related study of the stress field occurring around Vicker's hardness indents provides a link between theoretical and experimental stress profiles and demonstrates the accuracy of the micro-Raman profiling technique.     

High temperature erosion of Ti(Mo)C–Ni cermets

The resistance of Ti(Mo)C–Ni cermets of different binder content to solid particle erosion was evaluated at 25, 350 and 650 °C. The elevated temperature erosion of cermets containing 40, 50, 60, 70 and 80 wt.% of titanium carbides and produced from the powder of initially different ratios of Ni to Mo were tested with the help of specially designed centrifugal particle accelerator using silica as the abrasive. Erosion rate was related to both microstructure developed during sintering and materials removal mechanisms operating at the test conditions (impact angle of particles jet was 30° and 90° and velocity was 50 ms⁻¹). The erosion rate decreases with the increase of TiC and Mo contents in the composite. At 650 °C the process of tribo-oxidation affected the material performance to a great extent. The morphology of the worn surface was analyzed with SEM to determine the erosion mechanisms.     

The friction behavior of Ni-, SiO2- and mica sodium silicate-based solid lubrication composites

The friction behavior of Ni⁻-, SiO⁻₂- and mica sodium silicate-based lubricant composites, which included BN, WS₂ and graphite as lubricants, were examined. A ring-on-disk apparatus, in which a solid lubricant composite disk was held against a rotating stainless ring, was used as the test configuration. The tests were run with a load from 62 to 250 N in temperatures from 20 to 800°C in the laboratory environment. The wear surface was characterized by scanning electron microscope and X-ray photo spectroscopy. The major findings were that both mica sodium silicate- and SiO⁻₂-based composites failed at above 500°C due to severe wear and surface damage; in contrast, Ni⁻-based composite showed a stable friction coefficient and low wear from 20 to 800°C.     

The ricochet of dumb-bell shaped projectiles

Retardations and rotations were measured for five double-ended or dumb-bell shaped (d.s.) projectiles having spheres separated by a light weight rod at specific distances. The projectiles were fired into sand at approximately 100 m/sec and at an impact angle of 10°. Experimental data indicate that for identical sizes of sphere, initial speed, impact angle and projectile mass, the forces of ricochet are independent of the interspherical distance and seem to depend only on the geometry of the leading face.Tests were also carried out with two spherical and five d.s. projectiles at various entry speeds with 5°, 10° and 15° impact angles and it was found that the crater volume in sand is proportional to the initial momentum of the projectile.     

Experimental study of the effects of rough texture on surface deformation during cold metal forming

Both longitudinal and transverse frictions arising from plane strain during cold metal forming are of crucial importance for the accurate modelling, optimum design, and control of industrial processes. However, the influence of the friction and roughness along the transverse direction has been neglected in much previous research. Oblique roughness textures are considered, and the scale of roughness asperities is enlarged in this study. Four types of prism patterns, in which the angles between the longitudinal direction and the top line of prism are 90°, 60°, 30°, and 0°, and three types of pyramid patterns, in which the top angles are 151.9°, 161.1°, and 168.6°, were designed and manufactured using samples of annealed Al 6060T5. All compression tests were completed in 10 passes, and the total displacement of the pressure head was 5.4 mm. The first five passes were carried out on an Instron 8033 Materials Testing Machine, and the last five passes on a 500-ton compression-testing machine. The surface morphologies of the deformed peak were analysed, and the top areas of the deformed peak were measured. The effects of the angle between the longitudinal direction and the top line of the prism texture or the top angle of the pyramid texture on the surface morphology of the deformed peak are not obvious. The angles have a relatively significant effect on the deformation behaviour of the surface layer during cold metal forming when the deformation is small. The pattern with a top angle of 161.1°, which is the closest to the real value, shows the highest deformation resistance when the displacement of the pressure head is less than 1.2 mm.     

Long-term relative stability of thermistors

The relative stability of four glass-bead thermistors has been analyzed for 44 months to determine if thermistors have sufficient relative stability to be used as feedback sensors for milliKelvin levels of temperature control. The thermistors were measured at 20 ± 0.1 °C using commercial two-wire instrumentation. The thermistors have a nominal resistance of 12.5 kΩ and sensitivity of −4.5%/°C at 20°C. They are nested together inside several layers of thermal resistance and capacitance, which are held at nominal 20°C with a temperature-controlled, recirculating air chamber. After correction for instrumentation drift with two high-stability reference resistors, the average relative rms drift of the thermistors is 50 ± 15 μK, with an rms fitted drift rate of 0.26 ± 0.16 μK/week.     

Mechanical behaviour of brittle materials under hydrostatic pressure (on torsion of chalk cylinders)

Torsion tests were carried out on black-board chalk under hydrostatic pressures of up to 4·0 kgf/mm² in order to investigate the pressure effect on the deformation and fracture of brittle materials. Chalk, which is very weak (the tensile strength is about 0·1 kgf/mm²), was chosen as test material because the ratio of the applied hydrostatic pressure to the tensile strength of the material could be easily raised to high values.It is shown that there is a distinct difference in the characteristics of deformation and fracture between specimens under a pressure which is higher than a critical value of 0·3 kgf/mm² and those under a pressure less than that value. It is also shown that under relatively high pressure a macroscopic crack is formed around the twist angle yielding the maximum torque and thereafter it propagates helically with increase of twist angle.     

Finite element analysis of the rake angle effects in orthogonal metal cutting

The plane-strain finite element method is developed and applied to model the orthogonal metal cutting of annealed low carbon steel with continuous chip formation. Four sets of simulation results for cutting with −2°, 0°, 5°, and 15° rake angle are summarized and compared to analyze the effects of rake angle in the cutting processes. The initial and deformed finite element meshes, as the cutting reaches steady-state condition, are first presented. Simulation results of the cutting forces and residual stresses, along with the X-ray diffraction measurements of the residual stresses generated using a worn cutting tool with 5° rake angle, are used to identify the influences of the rake angle and tool sharpness. Elements are selected to represent three sections along the shear and contact zones and under the cut surface. The normal and shear stresses, distributions of parameters along these three sections, and contours of temperature, plastic strain, and effective stress are then presented. Limitations of the finite element method for metal cutting simulation are discussed.