Advanced Materials Research Vol. 702

Abstract: Casting design is chosen by Soedarsono et al to maintain cooling rate in producing thin wall ductile iron (TWDI). Cooling rate should be maintained to prevent carbide formation. This paper discusses the effect of gating system design on microstructure and mechanical properties of 4 mm TWDI plate. A casting design based on vertical gating system is made to produce TWDI plates with the thickness of 1, 2, 3, 4, and 5 mm. This vertical system allows plates to function as runner which will helps in preventing premature solidification. Three designs were made. These designs are coded as T1, T2, and T3. These three designs were also used in making 1, 2, 3, and 5 mm TWDI plates of which the result has been published. Z-Cast is used to conduct a casting design simulation for filling flow and solidification. The result of flow simulation shows that the filling flow is resulted in two kinds. The result of solidification specifies that the 4 mm TWDI plates solidify in the third place. The result of the experiment highlights that in all of the designs, which have microstructure and consisted of nodule graphite in ferrite matrix, no trace of carbide and skin effect are formed. The length of skin effect varies in all of the designs. The highest nodularity is only 80% while nodule count is 931 nodules/mm2. Brinell hardness number for all of the design is beyond the standard given by JIG G5502. As for UTS, yield strength and elongation none of the designs exceeds the minimal standard. The result of the experiment does not confirm the result of the simulation. In sum, compared to the previous result, the curve trends of 4 mm TWDI plates look similar to 2 mm TWDI plates.

Abstract: A new sandwich beam theory is proposed by introducing independent variables of the displacements of face sheets, middle plane of soft core according to the incompression in transverse direction of traditional sandwich beam theory. Based on Hamilton principal, the governing equation of the system is established. Galerkin truncation method was used to solve the governing equation. It was found that (1) the first mode of the system displays that it is consistent with the traditional sandwich beam theory; (2) the second mode of the system shows that the soft core is in the state of tension or in compression; (3) the third mode of the system displays that the upper part and lower part of soft core are in different state (tension or compression); (4) The incompressible model of sandwich beam is the special form of soft sandwich beam we establish in this paper.

Abstract: FCC Unit (Fluid Catalytic Cracking Unit) is a mechanical device used to convert bunker C oil into high quality gasoline. During the refining operation, pressure vessel of FCC unit operates in high-temperature and high-pressure environment. Careful structural analysis and design are necessary for such equipment.In this paper, FEA (Finite element analysis) of the FCC unit was performed to evaluate its structural stability. The equivalent stress of the FCC unit was investigated and compared against the ASME code design specifications.The area of high stress concentration with maximum stress higher than the prescribed value was analyzed locally to carefully evaluate the stress.CA nozzle in the FCC unit was found to have significant margins for factor of safety and was redesigned for weight reduction. Tensile test was carried out to verify the integrity of the welded parts. Tensile strength of the welded partssatisfies all design requirements.

Abstract: In order to meet the further requirements that study diamond-like carbon (DLC) films as rigid protective coating, a three-stage ultrahigh vacuum system composed of rotary vane pump and diffusion pump in parallel with TSP ( titanium sublimation pump) was designed mainly for getting limiting vacuum of 1.0×10^-6Pa within 30 minutes in the vacuum chamber of about 0.23m³. The chamber is a horizontal cylinder supported by a saddle-shaped bracket and it has been proved to satisfy the requirements of strength and stiffness, it can be easy to get ultrahigh vacuum by TSP. Initiation pressure of the TSP was set to 10^-3Pa vacuum after optimization analysis and the diffusion pump simultaneously was closed for the proper use. The system can be used as deposition equipment with the assistance of high and low vacuum measuring instruments and other accessories.

Abstract: The paper is devoted to simulation of nonlinear dynamic processes in mechanical systems with nonlinear characteristics of the physical nature. As an example torsional oscillation of rubber-cord muff, which connects rotating shafts of a drive of machines, is investigated. Influence of nonlinear properties of a muff on amplitude-frequency characteristics of a kinematic circuit is established. The research results are in accord with experimental data of other works.

Abstract: Removed at authors request

Abstract: The Stochastic Finite Element Method (SFEM) represents a new approach to solve mechanical systems with stochastic characteristics. The SFEM is based on the deterministic Finite Element Method in which some variables related to the structural state (variables involved in the stiffness matrix) and to the applied actions (involved in the load vector) are uncertain. In other words, the SFEM tries to look for the stochastic properties of the mechanical response. The solution of a stochastic mechanical system is completely defined through the evaluation of the probability density function of the response process. This cannot be analytically achieved through most of the available methods and techniques such as Fokker-Planck equation, Wiener-Hermite expansion, perturbation methods, stochastic linearization, WHEP technique, decomposition method and stochastic finite element methods [1; 2]. Some exact solutions are available for the mean and standard deviation, not for the Probability Density Function (pdf), of the solution process. In this paper, we develop the theory of method named the Stochastic Transformation Method (STM) in order to determine the pdf of the response of a stochastic mechanical system with random excitation and/or stiffness. The Stochastic Transformation Method is based on one-to-one mapping between the random output(s) and input(s) where the transformation Jacobean J can be computed. The pdf of the output(s) is then computed through the known joint pdf of the inputs multiplied by the determinant of transformation Jacobean matrix. The one-to-one mapping condition can be relaxed through some mathematical tricks. This STM allows us to express the “exact” pdf of the mechanical response [3], provided that the transformation Jacobean can be defined. For many cases, the pdf of the response can be obtained in a closed-form in terms of the joint distribution of the input random variables.

Abstract: To improve the vibration isolation performanceof an air spring system,the characteristics of the dynamic stiffness and damping of adual chamber air springwere first analyzed. A theoretical model ofa four dual chamber air springs system wasthen constructed,and through experimental verification,the theoretical and experimental curves showedthe same change trend.Based on the theoretical models, anobjective function used to optimize the structural parameters of an air springwas constructed. It was demonstrated that the vibration isolation performance of the air spring system was improved with the optimized parameters.

Abstract: Mandible defect and the lack of dentition may result in facial deformity and chewing organ defects. It happens after the surgery of oral and maxillofacial tumors. This study aims at this problem. In this study, Finite Element Analysis (FEA) was employed to reconstruct the implanted mandible for customized patient. The 3D FEA model has great importance for biomechanical analysis. Though the analysis of the biomechanical situation with different numbers of dental implants, we can optimize the location and quantity of the implants. In this way, we can improve the quality of the implants, reduce the pain of patients, reduce the operation cost and avoid secondary surgery.