Abstract: This paper provides an introduction of existing fatigue and fracture behavior studies about high performance steel (HPS). This paper is emphasis on the crack propagation studies of HPS 485W, which is a new kind of structural weathered steel produced by Wuyang Steel Company using quenching and tempering (Q&T) in China. HPS has more advantages than traditional steel, such as high fracture toughness and cracking tolerance, high strength, low preheating weld or no preheating, recycle using and so on, so it can be used in sustainable bridge and building structures with low carbon releasing. To ensure the using safety and extend applying area of the new green civil material, the key material properties of HPS should be studied, such as fatigue crack growth rate. Fatigue crack growth rate characterizes the material resistance to stable crack extension under cyclic loading. A set of 5 compact specimens were made from 8mm and 14mm thick HPS 485W separately. Fatigue crack growth rate function of crack-tip stress-intensity factor range, da/dN versus ΔK, is proposed based on the test results, which shows HPS has high cracking tolerance ability.
Abstract: The modern steel orthotropic decks have been used in steel bridges for 60 years all over the world because of its super structural advantages. Recently, more bridge owners, engineers and researchers pay more attention to the fatigue problem of orthotropic steel decks for a large number of fatigue cracks found in steel bridges. For example, bridge engineers have detected hundreds of fatigue cracks in steel orthotropic deck on the 888-meter long box girder of Humen Bridge only ten years after opening to traffic. How to design or repair the fatigue details in orthotropic steel decks is the critical question to be solved at first step. In current paper, the elaborate numerical analysis model of the orthotropic steel bridge decks was developed using ANSYS software with different floor-beam web cutouts shapes, such as conventional ellipse, circular, trapezoid and Haibach web cutouts. The finite element models were calibrated by static test of one full size orthotropic steel bridge deck model. According to the analysis results, it should select the rational cutout shapes based on actual load and structural conditions in steel bridge deck design and strengthening.
Abstract: Induced forces in secondary steel bridge members such as diaphragms and cross-bracing can cause out-of-plane distortion in webs that may lead to fatigue cracking. Such cracking is most likely to occur if the distortion must be accommodated in a short length of the web, such as in the gap between the end of transverse stiffeners and girder flanges, because the web gap is subject to double curvature. In this paper, the numerical analysis model of a real 3-span continue steel bridge was established using ANSYS software to calculate the real fatigue stress at the web gaps. Some key structural parameters, for example, web gap depth and web thickness, have been considered in the numerical models. The results show that web thickness and web gap depth give the great affection on the out-of-plane distortion fatigue stress at web gaps.
Abstract: In the present work, the structure optimum design and simulation analysis of automobile side-door impact beam was carried out by using Finite Element (FE) method. The model of the side-door impact beam impacting with the rigid pole was set up according to the requirement of the Federal Motor Vehicle Safety Standards intensity test of side door (FMVSS214). The numerical simulations were carried out using the software LS-DYNA. Attention was focused upon finding an optimum cross- section shape of the beam in order to improve the energy absorption character. Several types of impact beams were studied and compared. Results show that the energy absorption characters of the beam improved obviously when square cross section with the wall slope 10° and a 9 mm long curled edge was adopted.
Abstract: Some results of 3D finite element analyses of the all fracture modes (AFM) specimen on mixed-mode II and III fracture are presented in this paper. The computational fracture analysis is based on the calculation of separated strain energy release rates (SERRs) along the crack front by the modified virtual crack closure integral (MVCCI)-method and the commercially available FE-code ANSYS. Calculation results show that under pure in-plane shear loading (mode II), not only the mode II, but also the mode III loading conditions, are generated owing to the Poission’s ratio effects. Similarly, under pure out-of-plane shear loading (mode III), besides the mode III, the mode II loading conditions are induced due to the global deformation. Nevertheless, once in-plane and out-of-plane shear loadings are superimposed, the fracture behavior appears more complex. Further discussion is given associate with some previous study.
Abstract: The self-oscillation device has many advantages and is therefore suggested to be used in the pipeline supercharger. Simulation and analysis on the pressure-increasing effect of the pipeline supercharging caused by self-oscillation cavity were carried out by finite element method. The cavity structure of self-oscillation device was designed using the fluid network theory, natural frequency calculation, resonance conditions and Large Eddy Simulation Theory. A series of flow field distribution chart of the self-oscillation cavity were obtained. Results validate that the self-oscillation device is effective to increase the pressure of the pipeline supercharger. The relation curves of pressure-increasing effect with different structure parameters of the cavity were further analyzed. Previous experimental results are accordant with the present simulation results. It shows that the numerical analyses are reliable.
Abstract: The microbiological influenced corrosion (MIC) behavior of the low alloy steel with Zn-rich epoxy coating and micaceous iron oxide epoxy coating in the sterilized medium and sulfate-reducing bacteria (SRB) solution was investigated by using both full-coated and nicked-coated specimens. Results show that for steel coated with Zn-rich epoxy, the corrosion resistance of both full-coated and nicked-coated specimens was improved obviously. The Zn-rich epoxy coating protected the test steel effectively in the microbial environment with the cathodic protection in the earlier period and physical barrier protection in the later period. For steel coated with micaceous iron oxide epoxy coating, the corrosion resistance of full coated specimens was improved greatly. However, for nicked-coated specimens, corrosion was aggravated because the small anodic area around the nick accelerated the corrosion. It is concluded that the basic low alloy steel may be effectively protected by the micaceous iron oxide epoxy coating only when the steel is perfectly coated with the coating, breakage must be avoided.
Abstract: In this paper, a series of numerical simulations have been conducted to investigate the penetration performance of tungsten alloy segmented rods with various connectors and different design parameters, and corresponding continuous rod penetrate into semi-infinite thick steel target at velocities from 1.5 km/s to 3.1 km/s. The SPH hydrocode of AUTODYN was used in this paper to reveal the influences of design parameters on the penetration performance of segmented-rod projectiles. A non-ideal segmented rod projectile includes not only segmented rods but also carrier tube and connectors for assembly and integrity purposes. The penetration performance of penetrator is evaluated by examining the crater depth in thick steel targets.
Abstract: Steel and concrete are poured together with a certain way which can be regarded as a fiber reinforced composite material. For this composite material, the issues of bond and pull-out are very important. The bond property of reinforced concrete at normal temperature is different from the property at elevated temperature. The exposure of reinforced concrete structural elements to high temperatures during an aggressive fire leads to significant losses in its structural capacity due to the reduction in the strength of the concrete, possible plastic deformation of embedded steel and most importantly loss of bond between reinforcing steel and concrete. This paper aims to investigate the influence of high temperature to the bond slip of reinforced concrete. The bond behavior between reinforced concrete and reinforcing steel bars was evaluated under elevated temperatures. Based on the energy principle, the debonding criterion of the steel bars and concrete at a high temperature is derived. It was concluded that the bond slip should be included in order to reflect the unloading of the concrete surrounding the reinforcing steel exposed to fire temperature.
Abstract: In this study, specimens were prepared by mixing expanded polystyrene (EPS) beads with mortar to simulate degradation, and sound specimens include no beads. Measurement of acoustic emission (AE) was performed using an AE transducer. The changes in AE behavior with increase in strain were measured for a uniaxial compression test and a splitting test. The behaviors were investigated in comparison to the change in the damage variable. The AE parameters (rise time, reverberation frequency and average signal level (ASL) ) were evaluated by the average every ten seconds.