Three-Dimensional Rigid-Plastic FEM Simulation of Bulk Forming Processes with New Contact and Remeshing Techniques

Some techniques such as die surface description, contact judgement algorithm and remeshing are proposed to improve the robustness of the numerical solution. Based on these techniques, a three-dimensional rigid-plastic FEM code has been developed. Isothermal forging process of a cylindrical housing has been simulated. The simulation results show that the given techniques and the FEM code are reasonable and feasible for three-dimensional bulk forming processes.

Quantitative Prediction of Fracture Distribution of the Longmaxi Formation in the Dingshan Area, China using FEM Numerical Simulation

Fracture prediction is a technical issue in the field of petroleum exploration and production worldwide.Although there are many approaches to predict the distribution of cracks underground,these approaches have some limitations.To resolve these issues,we ascertained the relation between numerical simulations of tectonic stress and the predicted distribution of fractures from the perspective of geologic genesis,based on the characteristics of the shale reservoir in the Longmaxi Formation in Dingshan;the features of fracture development in this reservoir were considered.3 D finite element method(FEM)was applied in combination with rock mechanical parameters derived from the acoustic emissions.The paleotectonic stress field of the crack formation period was simulated for the Longmaxi Formation in the Dingshan area.The splitting factor in the study area was calculated based on the rock breaking criterion.The coefficient of fracture development was selected as the quantitative prediction classification criteria for the cracks.The results show that a higher coefficient of fracture development indicates a greater degree of fracture development.On the basis of the fracture development coefficient classification,a favorable area was identified for the development of fracture prediction in the study area.The prediction results indicate that the south of the Dingshan area and the DY3 well of the central region are favorable zones for fracture development.

Numerical and Experimental Study of the Roughness Effects on Mechanical Properties of AISI316L by Nanoindentation

Surface roughness is a commonly used criterion for characterization of surface quality in a machining operation. In the study of micro-scale mechanical properties of machined surface and cutting tool using nanoindentation method, perfect surface finish on the specimen is often required for the reliable indentation result. However, the perfect surface finish is often difficult to obtain from the machining operation due to the dynamic behavior of the machining and the limitation of the cutting tool geometry. In the presented paper, the effect of surface roughness on the nanoindentation measurements is investigated by using finite element method. A 3D finite element model with seven levels of surface roughness is developed to simulate the load-displacement behavior in an indentation process with a Berkovich indenter. The material used in the simulation is AISI 316 L stainless steel, modeled as an elastic-plastic material. The mechanical properties were calculated by combining simulations with the Oliver-Pharr method. The hardness and reduced modulus from the simulation were found to decrease with an increase of roughness. The study showed that the scatter of the load-depth curves and the deviation of the hardness and the reduced modulus are significant affected by the variation of roughness. It was also found that the height of pile-up was little affected by the surface roughness from the simulation. The combined effect of indenter tip radius and surface roughness was also investigated. The study was complemented with experimental tests and the results from these tests support the results from the simulation.

Damaging of cemented carbide end mill with different grain sizes:experimental and simulation

The main purpose of the current study was to investigate the effects of the size of WC grains on the damage evolution of WC-Co junk mills.The finite element method(FEM) simulation results showed that the finegrain(FG) tool retained its cutting edges radii longer than the coarse-grain(CG) tool.This event leads to the larger wear rate in the CG tool.Moreover,FEM analysis indicated that through increasing the feeding rate,the wear rate and the cutting forces increased as well.The observation of worn tool surface revealed that the formation of micro-pits,micro-cracks,scratching grooves and broken WC grains was among the common signs of the damage for both CG and FG tools.However,it was found that the defects are more intensive in the CG tool.This can be due to the lower boundary strength and less WC connectivity in the CG milling tool.The finer grains also decreased the mean free path in the Co binder and impeded the micro-cracks propagation in the material.

The optimal shapes of piles in integral abutment bridges

Integral abutment bridges(IABs) can be used to avoid the durability issues associated with bearings and expansion joints. For this type of bridge, the design of the optimal pile foundation, especially with respect to the horizontal stiffness, is a challenging issue. A structural optimization approach is proposed in this paper to optimize the pile foundation shape in integral abutment bridges. A procedure was implemented based on linking MATLAB, where an optimization code was developed, and OpenSees, which was used as the finite element solver. The optimization technique was compared with other techniques developed in previous researches to verify its reliability; the technique was then applied to a real 400 m-long IAB building in Verona, Italy, as a case study. The following two possibilities were considered and compared:(a) a pile with two different diameters along the depth and(b) a pile with a pre-hole. In fact, to increase the lateral and rotational flexibilities of the pile head, piles for an integral abutment bridge foundation are often driven into predeep holes filled with loose sand. Finally, the case of super-long integral abutment bridges(L = 500 m) with a corresponding displacement on one bridge end of approximately 50 mm was analysed. The following four pile design optimization cases were considered with similar study criteria as the Isola della Scala Bridge:(a) a pinned pile head for semi-integral abutment,(b) a fixed pile head without a pre-hole,(c) a fixed pile head with a pre-hole of any depth,(d) a fixed pile head of a pre-hole with a depth limit(< 2 m) allowing for enough embedded length for the friction pile. The case studies confirmed the potential of the proposed optimization techniques for finding the optimal shape of piles in integral abutment bridges.

Towards total protection from impact:a viability study using EPE foam to protect falling eggs

Total protection of fragile goods and equipment during transport has become critically important as fast delivery systems are growing rapidly due to the rise of mass online commerce worldwide.This paper therefore studies the protection of falling eggs—one of the most fragile goods—through packaging.Intensive experiments are first conducted to obtain the critical stress at which the eggshell is damaged by falling impact.Tests are first conducted of unpackaged eggs dropping onto a granite platform from various heights.Finite element method(FEM)models of unpackaged eggs are then built to simulate the behaviour of eggs and compute their stress levels.The experimental data is compared with the results of FEM simulations to determine the critical stress at which the eggshell is damaged.A series of tests and numerical simulations are then carried out for eggs wrapped in expanded polyethylene(EPE)foam.The stress distribution of both a single egg and multiple eggs in packaging are studied.An empirical formula between the drop speed(or height)and the bottom thickness of the EPE foam packaging is obtained,which can be useful in the design of packaging for the total protection of eggs that may fall during usual transport and delivery operations.The experimental and numerical results from this study show that it is viable to protect fragile goods,as long as the EPE form packaging has sufficient thickness.The proposed study and design procedure are helpful for the selection of key parameters of foam packaging to protect fragile industry products from impact.

Design and analysis of a shear mode piezoelectric energy harvester for rotational motion system

A shear mode piezoelectric energy harvester for harvesting energy from rotary motion is developed.The kinetic energy in the form of rotation is converted into electrical form of energy by piezoelectric principle with oscillation of piezoelectric patch through magnetic shear force.Efforts have been made to increase the output power using shear mode of operation.In order to estimate the induced voltage of piezoelectric patch,a mathematical model and an Finite Element(FE)model are developed.Considering various parameters,optimization of the harvester was made.Analytical and Finite Element Method(FEM)results are compared and good agreement has been found.The total average output power of 358.44 Wis generated when rotary speed of hub of about 600 RPM.