Key Engineering Materials Vols. 324-325

Abstract: Recently, people devote to the development of beta titanium alloys which have better biocompatibility because of the addition of Mo, Nb, Ta, Zr, Sn, et al. In this paper, the effects of heat treatment and cold roll deformation on the mechanical properties of the Ti-11.3Mo-6.6Zr-4.3Sn alloy (TMZS) are investigated by tensile test. The results show that the excellent combination of strength and ductility can be obtained by heat treatment or cold deformation. The TMZS alloy can obtain intermediate modulus, stronger than nickel titanium, weaker than stainless steel. The corrosion resistance of this alloy in the Hank's solution, 0.9% NaCl physiological solution and artificial saliva with different pH values at 37
are investigated by means of open-circuit potential (OCP), Tafel and potentiodynamic anodic polarization techniques. All the test results suggest that the TMZS alloy has excellent corrosion resistance in the three simulated solutions especially in the artificial saliva and has a large potential for biomedical application. In addition, the pH value and simulated solutions have some influence on the corrosion resistance of the TMZS alloy.

Abstract: Based on full layerwise displacement shell theory, the vibration and damping characteristics of cylindrical sandwiched panels with viscoelastic layers are investigated. The transverse shear deformation and the normal strain of the cylindrical hybrid panels are fully taken into account for the structural damping modeling. The layerwise finite element model is formulated by using Hamilton’s virtual work principle and the cylindrical curvature of hybrid panels is exactly modeled. Modal loss factor and frequency response functions are analyzed for various structural parameters of cylindrical sandwich panels. Present results show that the full layerwise finite element method can accurately predict the vibration and damping characteristics of the cylindrical hybrid panels with surface damping treatments and constrained layer damping.

Abstract: To consider the corrosive effects on aircraft structural life under natural environments, we have the calendric life to represent its impact. A new concept of Aircraft Structural Life Envelope (ASLE) to consider the combined effects of fatigue loads and corrosive conditions is developed and the sketch of ASLE is presented, then the basic determining methods of ASLE under different corrosive conditions are obtained too. Finally the linear damage cumulative rules are employed to analyze the usage of aircraft in different corrosive conditions, and the residual fatigue life and calendric life of aircraft structures can be predicted and supervised.

Abstract: Biaxial compressive tests of plain concrete specimens under normal temperature and suffering high temperature(200
600
)were completed under four lateral constant stress rates. The tests were completed by using the large static-dynamic triaxial test system for concrete in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. The biaxial compressive strength and deformation characteristics of concrete confined by lateral stress after suffering different temperature were studied in a systematic way. On the basis of the tests, the failure criterion of concrete subjected to constant lateral compressive stress after suffering different temperature was established in the Octahedral stress space. The conclusions can provide the testing and theoretical basis for deeper study of the concrete construction subjected to biaxial compressive combined loads suffering different temperature such as chimney, building after fire and safety shell for nuclear reactor.

Abstract: The paper deals with the problem of service life evaluation of counterweight bar bolted connection by means of computational analysis and experimental testing. Computational analysis has been performed using the local strain-life approach (ε-N), where appropriate material properties for treated high strength steel S1100Q has been determined previously. Experimental fatigue tests of bars were carried out in a specially constructed hydraulic pulsation machine. Comparison of computational and experimental results shows a reasonable agreement.

Abstract: Five twisted steel fibers (steel cord, SC) are used to improve the post-cracking behavior of cement composites. In addition to these steel cord macrofibers, microfibers are used to enhance the pre- and post-cracking strength and behavior. The three specific hybrid fiber blends pursued in this investigation are SC and polyethylene (PE), SC and polypropylene (PP) as well as SC and polyvinyl alcohol (PVA) fibers. The research results show that SC macrofibers with high ultimate strain, strength and bond stress can bridge the macrocracks in the matrix. Therefore, cement-based composites reinforced with SC fibers exhibit a pseudo-strain hardening in tension as a result of the formation of multiple cracks. The microfibers improved pre-peak mechanical performance, strength, and fracture process by delaying the formation of a macrocrack. The tensile strength, energy consumption capacity and ductility of SC macrofibers and high elastic modulus microfiber PE reinforced cement-based composites are tremendously improved compared to SC macrofibers with lower elastic modulus microfibers PVA and PP.

Abstract: Fatigue test on a full scale panel with complex loading and geometry has been carried out by using a tri-axial test machine located in the laboratory of the University of Naples. The aeronautical test panel was designed and manufactured by Alenia. The demonstrator is made up of two parts which are linked by a transversal joint that is parallel to the stringer direction. A fatigue load was applied in the normal direction to the longitudinal joint, while a constant load was applied in the joint direction. The full scale panel was equipped with strain gauges for deformation state measurements. Preliminary static load tests were performed in order to provide deformation measurements for numerical correlation. The outcomes confirmed that the applied load level is consistent with a linear elastic material behaviour. Three intermediate failures occurred before the final one: the first two under a clip, while in the third case a panel frame failed. Finally after about 177,000 cycles the demonstrator broke down. A non linear finite element analysis was also carried out in order to correlate failure events that occurred during the demonstrator testing.

Abstract: This paper investigates the effect of the ductile deformation behavior of high performance hybrid fiber-reinforced cement-based composites (HPHFRCCs) on the shear behavior and damage of diagonally reinforced coupling beams under reversed cyclic loading. The effects of matrix ductility on deflections, crack widths, crack patterns, failure modes, and ultimate shear load of the coupling beams have been examined. The combination of a ductile cement-based matrix and steel reinforcement is found to result in improved energy dissipation capacity and damage-tolerant inelastic deformation behavior. Test results showed that the coupling beam constructed with an HPHFRCC material exhibited excellent strength, deformation capacity, and damage tolerance capacity, in comparison with the regular reinforced concrete beam.

Abstract: In order to understand the effects of the metal components embedded in adhesive fillets on the strength of adhesively bonded single lap joint, the failed surfaces were studied with diagrams of scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectrometer. The stress distribution along the length of the bondline of single lap steel joints was also studied with an elasto-plastic finite element analysis (FEA) model to understand its effect in the view of mechanics. The SEM images and the FT-IR spectra diagrams revealed that the failure in the interface was primarily mixture mode with fillets and they also presented the interface strength being higher and there were more polar links formed in the adhesive fillets with metal components. The result obtained from the numerical modeling is in compliance with it from experiment that the stress distributed in lap zone of the joint is gentler when a couple of steel wires embedded in fillet.

Abstract: The mechanical behaviors were investigated by nonlinear creep tests of poly(methyl methacrylate) under different temperatures. The test duration was 4000 seconds. The corresponding temperature shift factors, stress shift factors and temperature-stress shift factors were obtained according to time-temperature superposition principle, the time-stress superposition principle and the time-temperature-stress superposition principle (TTSSP). The master creep compliance curve up to about 1-month at a reference temperature 22 degrees centigrade and a reference stress 14 MPa was constructed, and the effect of stress-induced damage evolution on the long-term creep behavior of polymeric material was accounted. It was shown that TTSSP provides an effective accelerated test technique in the laboratory, the results obtained from a short-term creep test of poly(methyl methacrylate) specimen at high temperature and stress level can be used to construct the master creep compliance curve for prediction of the long-term mechanical properties at relatively lower temperature and stress level, and the master creep compliance curve with damage considered can be applied to accurately characterize the long-term creep behavior of nonlinear viscoelastic polymer.