Advanced Materials Research Vols. 160-162

Abstract: Field experiments were carried out to study the effect of balanced fertilization on Phyllostachys heterocycla cv. Pubescens quality in Jiangxi and Hubei province. The results showed that the diameter breast height (DBH) and quality of bamboo shoots could be significantly increased under balanced fertilization The relative increment was best and reached to 11.17 % by N2P2K2, while there was after-effects of fertilizer. The Zn content of bamboo shoots under K fertilizer was lower than one of CK. The effects of fertilization were complex on mechanical properties of bamboo, which are slightly higher than the control by K fertilization, but the difference is not significant. Therefore, measures of balanced fertilization to improve forest productivity and quality, a significant increase in economic and ecological protection.

Abstract: The mechanical properties of Ph. Pubescens were an important index to measure quality of bamboo. We research effects of soil available N (AN), available P (AP) and available K (AK) on mechanical properties of Ph. Pubescens in Jiangxi province. The results showed that there was no obvious regular between soil NPK content and mechanical properties of Ph. Pubescens. The anti-bending strength (ABS), anti-extension strength (AES) and anti-shears strength (ASS) of Ph. Pubescens were 148MPa, 98MPa and 15.6MPa, respectively, the maximum shear-force (MSF) was 2.0KN, and the anti-pressure strength (APS) was 59Mpa. The APS of all samples were higher than that of the middle timber. The APS was high why the vascular bundle of Ph. Pubescens arranges rules. The effect of AK on APS was larger than that of AN and AP. The MPF was 10.1 KN, The internal structures of bamboo determined their mechanical properties, so the anatomy of bamboo could also affect the mechanical properties of bamboo.

Abstract: In this paper, experimental and numerical analysis is used to investigate the failure modes of dual phase steels under different loading paths. Numerical models are established for uniaxial tensile tests and stretch flanging tests. Special attention has been paid to the behavior of DP780 in stretch flanging tests with small die radius. The occurrence of shear fracture is identified by comparing numerical simulation results with test data. The study suggests that traditional theory of localized necking is feasible for DP780 under uniaxial tensile condition but invalid when it is undergoing stretch flanging tests with small radius.

Abstract: The fundamental principle of the twist drill conical grinding method was introduced. The mathematical model of the twist drill was established. Mathematical model to establish drill bit is the geometric design, manufacture, cutting analysis and modeling on the basis of the drilling process. According to the twist drill grinding principle, using Pro/E the three-dimensional modeling of the twist drill was completed, and the feature of the conical grinding method was analyzed.

Abstract: An emulation study of the drilling mechanism by general purpose twist drills is conducted by using FEM analysis software Deform-3D. Application of finite element software Deform-3D, some characteristic parameters of the work piece and the cutting tool material are combined. The load boundary conditions and the friction between tool rake face and chip are analyzed and defined. The chip separation criteria are chosen. The finite element analysis simulation of pretreatments is completed. By the finite element simulation analysis, the three-dimensional FEM model of twist drill is build. The scraps forming process and the distributed situation of cutting force，cutting temperature in the drilling process are analyzed. The effect of cutting variables on drilling forces of stainless steel is analyzed. The drilling temperature and the drill wear condition are discussed. The effect of the main geometric parameters on the stainless steel twist drill drilling performance is studied.

Abstract: This study aimed at investigating the effects of the post material properties on the maximum stress in the root and maximum deformation of the restorative system. Effects of material properties of fiber post on the maximum equivalent stress in the root and the maximum deformation of the restorative system were numerically investigated. Results show that the maximum equivalent stress in the root can be decreased by 8.3% and the maximum deformation of the restorative system decreased by 10% compared with corresponding maximum values if changing Young’s modulus, Shear modulus and Poisson’s ratio in the range studied here. The maximum equivalent stress in the root is more sensitive to Young’s modulus and Poisson’s ratio while the deformation of the restorative system is more seriously affected by the Shear modulus of the post material.

Abstract: The type of I-II compound crack in bridge deck pavement is most popular. Based on the theory of fracture mechanics the least equivalent stress method is put forward and used to study the problem of concrete cracks. The method could be used to determine the fracture angle of I-II compound crack. For the cracked deck pavement, the stress state could be determined by field test or numerical simulation method and then calculate the equivalent stress near the point by Matlab. The examples show that when the equivalent stress gets to the critical value the crack will develop along fracture angle which could be calculated from the least equivalent stress method. The theory value of fracture angle is basically accurate with the test one.

Abstract: For the interface end formed after paving asphalt overlay on cement concrete pavement, the stress field of interface end is very important for both structural analysis and interface design when the temperature drops. The stress field of interface end can be gotten with the crack-tip field theory that consider displacement continuation and stress equality on each side of interface, but it needs further verification to prove whether the initial stress field can satisfy far field boundary condition when temperature dropping. In conditions of different material properties, different plane dimension and different thickness of asphalt overlay the stress field is calculated with the finite element method (FEM), and the results show that the forms of theoretical solution can exactly describe stress field of the interface end when temperature dropping. The stress field of interface end indicates that when the elastic modulus of asphalt overlay becomes lager, the stress singularity’s degree of interface end will reduce. As for the interface end formed after paving asphalt concrete overlay on the concrete pavement, improving the elastic modulus of asphalt overlay is beneficial.

Abstract: The polymerization reaction kinetics of biodegradable polyurethane extended with soy protein isolate (SPI) with dibutyltin dilaurate (DBTDL) as the curing catalyst was studied by means of non-isothermal differential scanning calorimetry (DSC). Model-free methods, Kissinger method and Ozawa method, were applied for analyzing the DSC data. The Ea and lnA obtained from Kissinger method for catalyzed reaction between toluene diisocyanate (TDI) and Polyoxypropyleneglycol (PPG) are 60.80 kJ•mol-1 and 12.09, and for catalyzed reaction among TDI, PPG, and SPI they were 65.91 kJ•mol-1and 14.04. Similarly the Ea obtained from Ozawa method for catalyzed reaction between TDI and PPG and catalyzed reaction among TDI, PPG, and SPI were 63.49 kJ•mol-1 and 64.78 kJ•mol-1, respectively. The results showed that, the incorporation of a small amount of SPI into polyurethane did not affect the reaction kinetic strongly, but increases the reaction activation energy Ea and lnA.

Abstract: The bearing capacity of bridge structure would decrease under high temperature in fire, and there is a risk of structural collapse when the bearing capacity decreased to a certain degree. The estimate of bearing capacity of concrete structure at high temperature in fire will directly influence the scheme of disaster relief. Recently, there are a few researches on evaluating the bearing capacity of concrete structure at high temperature in fire, even fewer on bearing capacity of prestressed structure. Surface temperature and temperature of internal specific position of prestressed concrete T-beam are put forward in this paper by making use of ISO 834 international standard heating curve and distribution rules of temperature field of ASCE. The degradation of mechanical properties of concrete, steel bar, steel strand and other materials at high temperature are worked out according to relationships between material mechanical properties and high temperature, and on this basis, the bearing capacity of 3 prestressed concrete T-beams are calculated and evaluated at high temperature in fire. The results show that after being under 3-hour's high temperature in fire, the bearing capacity in high temperature of prestressed concrete T-beam would decreased to it’s 25% in normal; the stronger the concrete is or the thinner the concrete cover is, the greater decrease of bearing capacity of prestressed concrete T-beam would be. Based on calculations and evaluations, a statistics regression equation of bearing capacity of prestressed concrete T-beam at high temperature in fire is obtained.