Abstract: The drill pipe near the surface stands the largest tension and torsion load for the full hole during drilling operation. And fatigue crack growth is always the major cause of failure of drill string. As an example, 5ʺ drill pipe that was near the well head of an ultra-deep straight well and made of 30CrMo, whose constitutional relation was fitted by experiment, was analyzed here. Simplifying the initial crack of the drill pipe as circumferential semi-elliptical surface crack, we simulated the elastic-plastic fracture feature of the drill string with surface crack, partly through-wall crack and fully through-wall crack under combined loading of axial force and torsion. Crack front geometry evolvement is simulated for the different stages of crack propagation. This work would provide a basis for the full-range analysis of fatigue crack growth.
Abstract: Structural insulated panel (SIP) is considered as a green panel in construction industry because of the low thermal conductivity of the sandwiched EPS core (i.e extended polystyrene). It is a lightweight composite structure and is widely used in commercial, industrial and residential buildings to construct the building envelop including roof and wall. The windborne debris driven by cyclone or hurricane usually imposes intensive localized impact on the structural panel, which might create opening to the structure. The opening on the building envelope might cause internal pressures increase and result in substantial damage to the building structures, such as roof lifting up and wall collapse. The Australian Wind Loading Code (version 2011)  requires structural panels to resist projectile debris impact at a velocity equal to 40% of the wind speed, which could be more than 40 m/s in the tropical area with the wind speed more than 100m/s. In this study, two kinds of SIP under projectile debris impact were investigated, i.e. “Corrolink” and “Double-corrolink” composite panels shown in Fig. 1. Laboratory tests were carried out by using pneumatic cannon testing system to investigate the dynamic response of composite panels subjected to wooden projectile impacts. The failure modes were observed. The structural dynamic responses were also examined quantitatively based on the deformation and strain time histories measured in the tests. The penetration resistance capacity of panels subjected to windborne debris impact was assessed. Fig. 1 Schematic diagrams (L) Corrolink panel; (R) Double-corrolink panel 
Abstract: To evaluate the effect of the size of the microstructure on the mechanical property of the cavitated rubber blended (voided) amorphous polymer, the FEM simulation based on the rate form second-order homogenization method, in which rates of the macroscopic strain and strain gradient are given to the microstructure, was performed. Computational simulations of micro-to macroscopic deformation behaviors of amorphous polymers including different sizes and volume fractions of the voids were performed. Non-affine molecular chain network theory was employed to represent the inelastic deformation behavior of the amorphous polymer matrix. With the increase in the volume fraction of the void, decrease and periodical fluctuation of stress and localized deformation in the macroscopic field were observed, and were more emphasized with the increase in the size of the void. These results were closely related to the non-uniform deformation and volume increase of the void in the microscopic field.
Abstract: A numerical model of dynamic strain-induced ferrite transformation (DSFT) was developed by combining the multi-phase field model with the Kocks–Mecking model. Using the developed model, a three-dimensional simulation of the DSFT in a Fe-C alloy was performed to study the correlation between the variation in flow stress and the microstructure evolution during the DSFT. The simulation results indicated that the developed model successfully simulated the characteristic DSFT behavior, i.e., both the stress–strain curve with a single peak and the formation of an ultrafine-grained ferrite microstructure. The variation in the flow stress during the DSFT was characterized by the volume fraction of the ferrite phase.
Abstract: The paper aimed at the behavior identification of a stainless steel sheet treated by surface mechanical attrition (SMAT). From tensile testing results on specimen after removing different depth of treated surface, a multi-layered model can be built. Therefore, the SMAT treated sheet is divided into five layers along thickness direction: the top and bottom hard layers of 0.15mm, the soft middle layer of 0.5mm, and two medium layers of 0.1mm in between. An elastic-plastic damageable constitutive model is adopted to describe the behavior of each layer. The parameters for each layer are identified using an inverse calculation technique. The three-dimensional ABAQUS/Explicit models with mass scaling are built for the SMAT treated tensile specimen with and without removed external harder layer. The best fit of parameters for each layer is obtained by minimizing the scatter between measured stress and calculated stress for the prescribed strain history. Finally, the identified material model is validated by the numerical simulation of a penetration test of SMAT treated sheet metal.
Abstract: Thin-walled honeycombs have been extensively investigated and they are often used as sandwich panels to enhance the energy absorption in many applications including vehicles. In this study, axial compressive tests at three different velocities (3, 30 and 300 mm/min, respectively) by using an MTS machine were conducted with both empty and hybrid aluminium tubes filled with aluminium honeycomb. The aim of this work is to study the contribution of aluminium honeycomb in square hybrid tubes in terms of the deformation mode and energy absorption. Square aluminium tubes made of AA 6060-T5 with two different side lengths, 40 and 50 mm, were used. Two types of honeycombs made of AA 5052 with different cell wall thicknesses were used in this study. The force and displacement of the tubes were recorded during the test. The specific energy absorption (SEA) of honeycomb-filled tubes was compared with the sum of the SEA of an empty tube and honeycomb. It was noticed that the SEA of the hybrid tubes depended on the honeycomb density and the loading velocity within the velocity range studied.
Abstract: Titanium is widely used in biomedical implants because of its excellent mechanical properties, good biocompatibility and high resistance to corrosion. However, the fabrication of titanium components often involves high cost due to the long processing time and difficulty in metalworking. Powder metallurgy is a near-net-shape processing method which has the advantage of high production rate with low unit cost. In this study, a technique comprising microwave sintering with powder metallurgy has been developed to fabricate titanium components. Commercially pure titanium powdered compacts, prepared by three initial particle size groups of 10±2 μm, 30±2 μm, and 50±2 μm, were sintered in a 1.4 kW, 2.45 GHz microwave multi-mode furnace for 2 minutes using silicon carbide particles as the microwave susceptor to assist the heating. The room temperature deformation behavior of titanium components was investigated. Metallographic studies of the porosity and pore size were undertaken by optical microscopy. The results of this study indicate that irregular shaped pores were uniformly distributed within the sintered specimens. Furthermore, the pore size and porosity of the sintered specimens decrease with decreasing initial particle size. The compressive yield strength showed a linear relationship with the porosity, and was found to follow the Hall-Petch relationship with the initial particle size. This study demonstrated that it is feasible to microwave sinter titanium components having various compressive yield strengths by controlling the initial powder size of the titanium.
Abstract: In this paper, the deformation behavior of adhesive layer in die-bending for adhesively bonded sheet metals was investigated by experiments and finite element method (FEM). We paid special attention to the bending/unbending shear deformation of the adhesive layer during the die-bending of adhesively bonded sheet metals by using highly ductile acrylic adhesive. Major results obtained are summarized as follows: (1) The bending/unbending shear deformation of the adhesive layer was observed during the die-bending. (2) The punch radius has a large influence on the die-bending in the adhesively bonded sheet metals. (3) It is desirable to perform die-bending at high speed as well as air-bending.
Abstract: Hurricane, typhoon and cyclone take place more and more often around the world with changing climate. Such nature disasters cause tremendous economic loss and casualty. Various kinds of windborne debris such as compact-like, plate-like and rod-like objects driven by hurricane usually imposes localized impact loading on the structure envelopes such as cladding, wall or roof, etc. The dominant opening in the envelope might cause serious damage to the structures, even collapse. To withstand the impact of such extreme event, the requirements on panel capacity to resist windborne debris impact has been presented in the Australian Wind Loading Code (2011) . Corrugated metal panels are widely used as building envelop. In a previous study, laboratory tests have been carried out to investigate the performance of corrugated metal panels subjected to a 4kg wooden projectile by considering various impact locations, impact velocities and boundary conditions. In this study, numerical models were developed to simulate the responses of the corrugated metal panels subjected to wooden debris impacts by using commercial software LS-DYNA. The predicted data from the numerical simulations were compared with the experimental results. The validated numerical model can be used to conduct intensive numerical simulation to study the failure probabilities of corrugated structural panels subjected to windborne debris impacts.
Abstract: Titanium alloys have received great interest in the engineering applications requiring light weight and high impact resistance components. It is necessary to understand the mechanical properties of titanium alloys at high strain rates and various temperatures in the structural design. In the present paper, uniaxial tension tests at strain rates of 190, 500 and 1150s-1 and temperatures of 20, 150, 300°C are carried out using a modified split hopkinson tension bar system to investigate the effects of strain rate and temperature on tension behavior of the Ti-6.6Al-3.3Mo-1.8Zr-0.29Si alloy. Experimental results indicate that the alloy has the rate and temperature sensitivity and still keeps high strengths and toughness at temperature up to 300°C under high strain rate. SEM observations reveal that ductile fracture is the major fracture mode when the alloy is deformed at high strain rates.