Advanced Materials Research Vols. 538-541

Abstract: Creep age forming (CAF) is an effective process to manufacture aircraft panels with better performance including improved strength and toughness, lower weight and increased resistance to fatigue and corrosion. Due to restrictions of aging cycle to create the desired property, springback in CAF is larger than other forming processes. That makes its prediction one of the key technologies in CAF. A solution is developed to predict springback in CAF of aluminium components. The studies are mainly concentrated on the pure bending of aluminium strips. Comparisons of predictions with experimental data yield agreement. Effects of T-beam’s structural factors, like width, skin thickness, rib width and transitional radius on springback are investigated. And a relationship between geometrical data and springback is given by the proposed algorithm.

Abstract: The properties of fifteen bamboo/cotton interwoven fabrics with different specifications were tested, such as static drape coefficient, dynamic drape coefficient, total bending rigidity, elastic modulus of bending, the angle of fast-elastic recovery, the angle of delayed-elastic recovery,etc. then the author taked these properties index as clustering index, fifteen bamboo/cotton interwoven fabrics as clustering object, using the grey clustering analysis to evaluate the bending, creasing and draping properties synthetically. The results show that: The first grey type included 1^#, 2^#, 3^#, 4^#, 7^#, 8^#, 10^#, 11^#, achieved optimal standard；The second grey type included 5^#, 6^#, 9^#, achieved good standard；The third grey type included 12^#, 13^#, 14^#, 15^#, their bending properties, creasing properties and draping properties were poor.

Abstract: With cold rolling base plate of low carbon steel by CSP process, the cold deformation experiments were carried out by the two-roller reverse-mill in the laboratory. The work-hardening was studied for different deformation plates through the room temperature tensile and microhardness measured, and the microstructure was also studied after deformation. It was found that the steel yield and tensile strength increased and work-hardening marked with the deformation augment, the test steel microstructure is ferrite with mingle small amount pearlite, its grain is refined and elongated with deformation increasing.

Abstract: The changes in residual surface stress state significantly affect the mechanical behaviour of the materials. In this paper, the effect of cryogenic treatment on grinding residual stress of ultra-fine grained WC-Co hardmetals has been investigated by measuring the residual stress of ground carbide surfaces before and after cryogenic treatment. The results show that the cryogenic treatment can relieve the residual stresses of ground carbide surfaces. Relaxation degree of residual stresses is highly dependent on the process parameters of cryogenic treatment, such as soaking temperature, cooling rate and warming rate. The relaxation rate of residual stresses decreases with the decreasing of soaking temperature, warming rate or increasing cooling rate, and does not change obviously with the soaking time.

Abstract: In this paper, the ultrasonic vibration uniaxial tension experiment was carried out on the 20# steel with a set of ultra-high-frequency vibration device. It showed that the material defect was the important factors of ultrasonic “soften” mechanism and obtained the crack extension mechanism under ultrasonic fatigue loading, there were：(1)The high frequency vibration of the ultrasonic fatigue loading weakened the influence of the plastic zone of the crack tip and residual stress on crack extension; (2)When the fatigue crack extension, the ultrasonic wave spread in the specimen, and reflected in the crack surface, resulting the crack closure effect decreased, the plastic zone of the crack tip decreasing; (3)The high vibration frequency and deformation velocity resulted the increase of the thermal effect, crack extension energy spread to the continuous medium in the form of heat, promoting crack extension and releasing energy. It also study the influence of different groove depth and groove curvature on the material ultrasound fatigue limit, and obtained the relation curve of fatigue limit with groove depth and groove curvature.

Abstract: Reinforcing rib structure in the aluminum heating-plate automatic casting system was modeled by ANSYS, the static and dynamical problems were studied. Deformation and stress were calculated by static analysis, the front ten orders inherent frequency, critical rotating-speed and vibration modes were analyzed by modal analysis technology, vibration amplitude responses were obtained by harmonic response analysis. The maximum deformation value of reinforcing rib structure was less than 2mm (irrespective of the structure self-weight); the maximum equivalent stress was about 64.8MPa. It showed that the reinforcing rib structure could effectively avoid the resonance region, and the maximum vibration mode according to its inherent frequency appeared at the edge of the structure, some vibration modes were orthogonal, the main vibration modes appeared in the forms of bending, torsion, but the stretching vibration mode was scarce. The low orders inherent frequency greatly effected more than the high orders inherent frequency by harmonic response analysis, and the maximum deformation value was 25μm in low order vibrations. The conclusion is that the reinforcing rib structure fulfills design requirements and operates softly.

Abstract: Results of an experimental investigation to study the structural behavior of new GSZ panels are reported. Three half-scale new GSZ panels with variable reinforcement ratio were cast and tested under vertical loading and low cycle reversed horizontal loading. The failure process, strains in vertical steel bars and surface–concrete, load–displacement curve under increasing load were recorded and analyzed. Result obtained showed that the entirety performance of new GSZ panel is excellent. And the reinforcement ratio has a great influence on the lateral stiffness of the panel.

Abstract: The C₆ reservoir of YC formation is shallowly buried in QiLiCun oilfield, Ordos basin. It’s a layered, ultra-low permeable and low pressure oil pool with poor productivity. Hydraulic fracturing is the necessary and only effective stimulation way for economic oil production. There are several calcareous interbeds in it, the thin and heterogeneous oil-bearing layers here are poorly connected or even unconnected in vertical. And it is prone to forming artificially horizontal hydraulic fracture for its particular payzone in-situ stresses. In conventional fracturing stimulation, only 1 or 2 fractures are feasible. Then few producing layers were employed only in production. Aiming at multiple horizontal fractures should be located exactly in hole, based on its affecting factors intensive analyzing in fracturing and field technological stimulation mechanism research, a study and application of hydraulic jet fracturing (HJF) has been introduced. A 2 stage fracturing of 2.5m space has been finished. It’s a breakthrough or milestone for conventional operation. The successful pilot test has proved that fracture can be located exactly by HJF and then well productivity is enhanced obviously also. According to the operation practice, some feasible operation measures improvement has been discussed in detail. HJF should be the predominant technology for the field.

Abstract: The delamination at the interface between the aluminium and prepreg layers has greater influence on the fatigue crack growth in fiber metal laminates. To study delamination propagation property of one kind of new fiber metal laminates, by using 2/1 lay-up specimen, this article accomplished delamination propagation test under various stress levels at R=0.1 by optical method and compliance method respectively. The delamination propagation property of this laminate is obtained by analyzing and calculating. A modified compliance equation is created to calculate the delamination size of this laminate more accurately by adding a non-dimensional factor.

Abstract: Boiler is a closed vessel in which the water is heated up to convert it from the liquid phase to superheat steam at specified pressure by addition of heat. The tubes are operated continuously at high temperature due to the formation of scale which has lower conductivity than that of steel. The scale can be formed for various reasons of which tube geometries, flue gas and steam temperature are prominent. The remaining wall thickness decreases due to the formation of scale which eventually causes failure of the boiler tubes. In this investigation an iterative technique was used to determine the temperature distribution across the tube with the increase of operating time. The operating time was considered up to 160,000 hours. The remaining life of the steam generator tube was found by finding hoop stress and Larson Miller Parameter from the Larson Miller Parameter curve for SA213-T22 material. The remaining life of the steam generator tube was used to find cumulative creep damage. By utilizing finite element modelling software, ANSYS 9/ ANSYS 11 the temperature distribution across the steam generator tube was evaluated. The temperature distribution along with Larson Miller Parameter predicted the oxide scale thickness. It was also observed that different input parameters have pronounced affect on the formation of oxide scale inside the steam generator tube. By increasing the heat transfer rate across the wall, the oxide scale thickness was increased more rapidly than normal condition. It was also observed that due to formation of scale the thermal conductivity in the boiler tubes was affected and the remaining life of boiler tubes was decreased and accelerated creep damage.