Advanced Materials Research Vol. 1016

Abstract: The compressive properties of open-cell aluminum foams are numerically studied using representative volume elements by means of the finite element method. Four face body centered cubic cell arrangements are analyzed, namely uniform-size with spherical pores and dual-size with spherical pores. The results demonstrated that a cell configuration with dual-size pore arrangement presents improved properties for applications subjected to compression loading. This is attributed to the introduction of secondary pores in the cell structure that provide an increase in the specific stiffness and strength of open-cell aluminum foams.

Abstract: The feasibility of friction stir spot welding was studied on AA5754-H22 and AA2024-T3 aluminum alloys which have widespread applications in aircraft and automotive industries. The quality of the joint was evaluated by examining the characteristics of the joint as a result of lap-shear fracture load. Taguchi approach of the parameter design was used as a statistical design of experiment technique to set the optimal welding parameters. The experiments were arranged by using Taguchi’s L9 orthogonal array. The signal-to-noise ratio and the analysis of variance were utilized to obtain the influence of the friction stir spot welding parameters on the lap-shear fracture load. Finally, the results were confirmed by further experiments.

Abstract: In this paper, firstly the characteristics and discrete mathematics method of Nurbs curve were studied in-depth, and a NC processing method based on De Boor-Cox algorithm was presented. Then, dedicated data-processing software for NC system was developed with VC++ 6.0. This software has been well applied in practice production, and the production efficiency is improved as well.

Abstract: An experimental investigation into CNC turning operation on Brass C36000 alloy as work piece material which is widely used for various industrial applications is performed. Multi objective optimization is carried out to find out the influencing machining parameters among spindle speed (rpm), feed (mm per revolution) and depth of cut (mm) for CNC turning of Brass C36000 alloy with surface finish and Material Removal Rate as performance parameters using Taguchi method. Taguchi orthogonal array [L₂₇ (3³)] is used for the experimental design. All experiments are conducted using EMCO Concept Turn 250 machine tool with carbide insert cutting tool. The optimization result shows that feed is the most significant turning machining parameter for surface roughness while depth of cut has high influence on material removal rate followed by spindle speed during CNC turning of Brass C36000 alloy. Above results is further validated using ANOVA approach.

Abstract: —Pure copper was deposited with Ti6Al4V alloy via laser metal deposition (LMD) process to produce Ti6Al4V/Cu composites. This paper reports the effect of powder flow rate (PFR) and gas flow rate (GFR) of laser metal deposited Ti6Al4V/Cu composites. The deposited samples were characterised through the evolving microstructure and microhardness. It was observed that the PFR and GFR have an influence on the percentage of porosity present in the samples. The higher the flow rates of the powder and the gas, the higher the degree of porosity and vice versa. The widmanstettan structures were observed to be finer as the flow rate reduces which in turn causes a decrease in the hardness values of the deposited composites. The hardness values varied between HV381.3 ± 60 and HV447.3 ± 49.

Abstract: This paper proposes a simplified finite element model to represent a riveted lap joint in structural dynamic analysis field. The rivet is modeled by spring-damper elements. Several numerical models are studied with different quantities of rivets (1, 3 and 5) and spring-damper elements (4, 6, 8, 12, 16 and 20) per rivet. In parallel, samples of two aluminum material plates connected by different quantities of rivets (1, 3 and 5) are built and tested in order to be known its modal characteristics – natural frequencies and mode shapes. The purpose of the different settings is to get the best numerical riveted lap joint representation relatively to the experimental one. For this purpose a finite element model updating methodology is used. An evaluation of the best numerical riveted lap joint is carried out based on comparisons between the numerical model after updating and the experimental one. It is shown that the riveted lap joints composed by eight and twelve spring-damper elements per rivet have the best representation. A stiffness constant value k is obtained for the riveted lap joints in study.

Abstract: In this paper, a novel method is proposed to address the non-linear dynamic response of a beam-like structure supported by a tensionless foundation due to moving loads. A lattice spring model (LSM) is developed to describe the structure as a discrete assembly of particles interacting via shear and rotational springs while the tensionless foundation is simulated using a chain of one-way normal springs connecting the particles to the ground. The total time for the travelling load to traverse the beam is divided into a number of steps and the generalised explicit matrix equation can be solved for each time step to obtain the time-history response of the structure. An iterative procedure is adopted to obtain the correct sign of lateral displacement for all particles at each time step, which determines the lift-off regions throughout the beam.

Abstract: In this paper, the model of hydraulic vibration system is established and sinusoidal vibration control algorithm is discussed and studied. A sinusoidal control hydraulic vibration system is designed. By simulation, this system has good frequency response characteristic and sine sweep control function.

Abstract: In this paper, the application background and function of vibration test is introduced. Besides, the composition and working principle of vibration test system is also introduced simply. Furthermore, the characteristic of water and oil is compared with each other in the paper. It is discussed if the water hydraulic is able to be used in the hydraulic vibration test-bed or not. The capability of hydraulic vibration test-bed based on water is simulated by Matlab software. The feasibility of this project is also analyzed.

Abstract: In this study, dynamic analysis of carbon plain weave square plates with different damage patterns including pattern of post-low velocity impact and patterns of post-ballistic impact is considered. For this purpose, vibration tests are performed to present the vibration characteristics of the four-edge clamped square plates. Effects of bullet-tip geometry, projectile velocity and impact damage location on the vibration characteristics are examined experimentally. Results are given in graphical form.