Research on cracking mechanism of the thin shell mould in expendable pattern shell casting during pattern removal process

Aiming at the cracking phenomenon of the thin shell mould in the expendable pattern shell casting during the pattern removing process, some systemic researches are presented.The influence of the pattern removing method and temperature on the pattern removing were investigated.The shell mould cracking mechanism was analyzed by using thermo-gravimetric analysis (TGA), and combining the temperature field and the volume change of the expanded polystyrene (EPS) foam pattern being tested.The results indicated that the shell mould was not easily cracked when the pattern removing process was carried out with the furnace being heated little by little because of the shell slowly shrinking with dehydration and shell strength gradually increasing.The shell mould was soon destroyed when it was set directly into the furnace at above 400 oC because of the thin shell mould rapidly shrinking and the foam pattern hindering.However, the shell mould had no cracking when it had been preheated for a long time even if the furnace temperature was above 400 oC and the shell was put into the furnace directly.Moreover, when the shell mould was directly set into the furnace at lower temperatures, 250 to 300 ℃, the shell would shrink slowly and the foam pattern would stay at the maximum expansion stage temperature of 100 to 110 ℃ for a long time; and the shell mould would experience an expansion force from the foam pattern for a long time.The expansion force is related to the pattern removing temperature, holding time, foam pattern thickness and density.Therefore, the foam pattern with higher density could make the shell crack.

Heuristic Method for Job Shop Scheduling Problem with Combination Processing

A job shop scheduling problem with a combination processing in complex production environment is proposed. Based on the defining of ＂non-elastic combination processing relativity＂ and ＂virtual process＂, the problem can be simplified and transformed to a traditional one. On the basis of the dispatching rules select engine and considered factors of complex production environment, a heuristic method is designed. The algorithm has been applied to a mould enterprise in Shenzhen for half a year. The practice showed that by using the method suggested the number of delayed orders was decreased about 20% and the productivity was increased by 10 to 20%.

Effects of Ce and Sb on the microstructure and properties of AZ91D magnesium alloy prepared by the EPC process

The effects of small amounts of cerium and antimony additions on the microstructure and the mechanical properties of AZ91D（Mg-9Al-Zn） based alloy were researched via the expendable pattern casting（EPC） process.The results show that the microstructure is obviously refined and the tensile strength of the AZ91D based alloy at ambient temperature is significantly improved.When compared to AZ91D,the AZ91D-1.0%Ce-0.4%Sb alloy has higher ultimate tensile strength and elongation.Its ultimate tensile strength and elongation are enhanced by 39% and 47%,respectively.The morphology of the tensile fracture of the AZ91D-1.0%Ce-0.4%Sb alloy has more characteristics of quasi-cleavage.This indicates that it has had a larger plastic deformation before failure.The tensile strength and elongation decrease with the increase of Ce and Sb contents because of the coarsening and volume increase of CeSb and Al11Ce3 phases.

Effect of bonding process on the properties of isotropic epoxy resin-bonded Nd-Fe-B magnets

Bonded NdFeB magnets were prepared by compression molding. The effect of preparation technology on their magnetic and mechanical properties was studied through the analysis of density, Br, Hcj, （BH）max, bending strength, and compressive strength of the bonded magnets. The results showed that the magnetic properties decreased with increasing binder content, whereas the mechanical properties increased. Br and （BH）max increased with rising pressure, whereas Hcj decreased. For a fixed mass fraction of the binder, the optimal pressure was 620 MPa and the best thermosetting temperature was 160°C. These conditions made the bonded magnets have the optimal mechanical properties. Scanning electron microscopy （SEM） analyses of the fracture surfaces indicated that the epoxy resin bonded magnets exhibited brittle behavior.

Derivation and application of time step model in solidification process simulation

The heat transfer during the casting solidification process includes the heat radiation of the high temperature casting and the mold,the heat convection between the casting and the mold,and the heat conduction inside the casting and from the casting to the mold. In this paper,a formula of time step in simulation of solidification is derived,considering the heat radiation,convection and conduction based on the conservation of energy. The different heat transfer conditions between the conventional sand casting and the permanent mold casting are taken into account in this formula. The characteristics of heat transfer in the interior and surface of the casting are also considered. The numerical experiments show that this formula can avoid computational dispersion,and improve the computational efficiency by about 20% in the simulation of solidification process.

Simulation of Induction Heating Process of Continuous Casting Slab

Induction heating of steel in continuous casting/rolling process is an important means to reduce energy consumption, decrease cost and improve efficiency, thus becoming an attractive research direction. A mathematical model with Finite Difference Method （FDM） was developed to describe the electromagnetic field and predict the temperature distribution in the steel slab for the whole induction heating process. To validate feasibility of the model, computational results were compared with the ANSYS simulation results. According to the comparing results, the temperature distributions of the slab cast under different technical parameters were investigated, which may provide useful information to optimize the parameters of technology in heating process.

Influence of mechanical vibration on the solidification of a lost foam cast 356 alloy

Mechanical vibration was applied to the solidification of a lost foam cast(LFC) 356 aluminum alloy.Effects of mechanical vibration,with different peak acceleration,on the size and morphology of α-Al phase,and also on the mechanical properties of the castings were studied.Results indicated that α-Al dendrites gradually grow into equiaxed grains as the peak acceleration of vibration is increased.When the peak acceleration is between about 1 to 4 g,α-Al phase distribution is uniform and is refined obviously.α-Al dendrites are reduced and the mechanical properties of the castings are improved significantly when compared to those of the castings that are produced without vibration.However,when the peak acceleration is higher than 4 g,strong vibration will lead to defects formation,such as sand adhesion,while the amount and size of pores will be increased.And due to the turbulent flow that caused by strong vibration,the chance of forming large pores in the matrix has been increased significantly.The increase in defects will result in the deterioration of mechanical properties.

Improvement of humidity resistance of water soluble core by precipitation method

Water soluble core has been widely used in manufacturing complex metal components with hollow configurations or internal channels;however,the soluble core can absorb water easily from the air at room temperature.To improve the humidity resistance of the water soluble core and optimize the process parameters applied in manufacturing of the water soluble core,a precipitation method and a two-level-three-full factorial central composite design were used,respectively.The properties of the cores treated by the precipitation method were compared with that without any treatment.Through a systematical study by means of both an environmental scanning electron microscope(ESEM) and an energy dispersive X-ray(EDX) analyzer,the results indicate that the hygroscopicity can be reduced by 20% and the obtained optimal process conditions for three critical control factors affecting the hygroscopicity are 0.2 g·mL-1 calcium chloride concentration,4% water concentration and 0 min ignition time.The porous surface coated by calcium chloride and the high humidity resistance products generated in the precipitation reaction between calcium chloride and potassium carbonate may contribute to the lower hygroscopicity.

Performance characteristics of EZhou bentonite of Hubei province and its modification

Both the chemical compositions and performance characteristics of the bentonite raw ores in Ezhou area of Hubei province and Honghuoshan area of Liaoning province were compared and analyzed.The properties of these two kinds of bentonites were tested before and after Na+-and Li +-modification.The results show that the Ezhou bentonite ore possesses higher montmorillonite content than the Honghuoshan bentonite ore,but the Ezhou Na-bentonite has weaker castability(e.g.wet compression strength and hot wet tensile strength)than the Honghuoshan Na-bentonite,while the performance of Ezhou Li-bentonite,such as colloid index,swelling value,swelling volume and mould coating performance,is equivalent to that of the Honghuoshan Na-bentonite.

DEFORMATION ANALYSIS OF SHEET METAL SINGLE-POINT INCREMENTAL FORMING BY FINITE ELEMENT METHOD SIMULATION

Single-point incremental forming （SPIF） is an innovational sheet metal forming method without dedicated dies, which belongs to rapid prototyping technology. In generalizing the SPIF of sheet metal, the deformation analysis on forming process becomes an important and useful method for the planning of shell products, the choice of material, the design of the forming process and the planning of the forming tool. Using solid brick elements, the finite element method（FEM） model of truncated pyramid was established. Based on the theory of anisotropy and assumed strain formulation, the SPIF processes with different parameters were simulated. The resulted comparison between the simulations and the experiments shows that the FEM model is feasible and effective. Then, according to the simulated forming process, the deformation pattern of SPIF can be summarized as the combination of plane-stretching deformation and bending deformation. And the study about the process parameters＇ impact on deformation shows that the process parameter of interlayer spacing is a dominant factor on the deformation. Decreasing interlayer spacing, the strain of one step decreases and the formability of blank will be improved. With bigger interlayer spacing, the plastic deformation zone increases and the forming force will be bigger.

Some problems in the production of ductile irons by investment casting

Because of the excellent performance of ductile irons and the unique superiority of investment casting, thepreparation of complicated and thin-wall ductile iron castings by investment casting shows a good developmentprospect. In this present work, combined with the actual product experiments, the characteristics of shell making,spheroidization, inoculation and defect prevention are presented, and some suggestions are given for investmentcasting of ductile iron.

Event-Driven SOA Based Integration Platform for Mold Making Industry

The platform consists of three administers the infrastructure of the whole platform; layers： the management service layer the integration service layer provides the core integration functions and the user service layer satisfies the enterprise integration demands. For the purpose of accommodating the characteristics of mold making companies, an event-driven enterprise service bus working as the heart of the platform is realized. A prototype system combining Web services, Business Process Execution Language （BPEL） and Web Ontology Language （OWL） is implemented. The clients and suppliers and the applications of mold making company are integrated in a loosely-coupled way through the services provided by the platform. Meanwhile the sharing of data and knowledge, and the coordination of business process are realized. By adopting the platform, a new approach is provided to solve the problem of design and manufacture integration for intra and inter mold making companies.