Papers by Keyword: 3D

Abstract: It is a serious problem that short carbon fiber reinforced polyamide 66 (SCFRPA66) cannot be easily shaped by 3D-printing for practical usages. In order to improve on the brittleness, homogeneous low potential electron beam irradiation (HLEBI) to both sides of 3D-SCFRPA66 samples was found to increase strain at tensile strength (εts), corresponding to homogeneous deformation and fracture strain (εf), as well as resistant energy of homogeneous deformation (Ehd), whereas the HLEBI decreased the tensile strength (σts). This improvement in ductility can be explained by lone pair electrons, dangling bond generation, shortening and relaxation of the polymeric chains by the HLEBI.

Abstract: In this study to the authors knowledge 1^st time, Metal Injection Molding (MIM) technique was used to introduce the magnesium alloy WE43 into binder-based powder metallurgical (PM) processing. Towards later adoption to binder-based 3D-printing technologies, Fused Granular Fabrication (FGF) technique, respectively for biomedical application. Metal Injection Moulding (MIM) is a binder based economic near net shape prototyping technique for production of complex shaped parts in high number and high reproducibility, and hence perfect as a “gold standard” for the introduction of new Mg-alloys into binder passed PM processing. In doing so, dogbone shape tensile test specimen were manufactured by MIM, subsequently solvent debound and conventional sintered in argon atmosphere. Next to the as sintered specimens (asS), solid solution heat treatment (T4) and precipitation hardening heat treatment (T6) were performed on additional specimens. Tensile tests pointed out high strength and ductility of as sintered and heat treaded specimens of up to 226 MPa UTS at 7.6% elongation at fracture. The microstructure was investigated using SEM imaging technique equipped with energy disperse x-ray energy analysis (EDX) for secondary phase analysis. Hence, the magnesium alloy WE43 could be identified as a high strength and ductility alloy for binder based PM processing for future additive manufacturing approaches in biomedical applications of patient adapted implants.

Abstract: The problem of the effect of a normal harmonic force on a porous beam in a 3D formulation is solved using the boundary-element method. A homogeneous fully saturated elastic porous medium is described using Biot’s mathematical model. The effect of the porosity and permeability parameters on the deflection of the beam and the distribution of pore pressure over the beam thickness is investigated. The comparison of the boundary-element solution with a 2D numerical-analytical one is given.

Abstract: In this paper, a Laplace domain boundary element method is applied for transient dynamic analysis of three-dimensional multi-domain linear piezoelectric structures. Piezoelectric materials of homogeneous sub-domains may have arbitrary degree of anisotropy. The boundary element formulation is based on a weakly singular representation of the piezoelectric boundary integral equations in the Laplace domain. To compute the time-domain solutions a convolution quadrature formula is applied for the numerical inversion of Laplace transform. Presented multi-domain boundary element method is tested on a three-dimensional problem of nonhomogeneous column which is made of two dissimilar piezoelectric materials and subjected to dynamic impact loading.

Abstract: We work with the numerical solution of the turbulent compressible gas flow, and we focus on the numerical solution of these equations, and on the boundary conditions, particularly on the outlet boundary condition with the preference of given mass flow. Usually, the boundary problem is being linearized, or roughly approximated. The inaccuracies implied by these simplifications may be small, but it has a huge impact on the solution in the whole studied area, especially for the non-stationary flow. The boundary condition with the preference of mass flow is sometimes being implemented with the use of some iterative process, guessing the correct values (for the pressure, density, velocity) in order to match the given mass flow through the boundary. In our approach we try to be as exact as possible, using our own original procedures. We follow the exact solution of the initial-value problem for the system of hyperbolic partial differential equations. This complicated problem is modified at the close vicinity of boundary, where the conservation laws are supplied with the additional boundary conditions. We complement the boundary problem suitably, and we show the analysis of the resulting uniquely-solvable modified Riemann problem.The resulting algorithm was coded and used within our own developed code for the solution of the compressible gas flow (the Euler, NS, and RANS equations). The examples show good behaviour of the analyzed boundary condition.

Abstract: This study used test frames were purposely detailed and constructed with observed deficiencies in investigated dormitory buildings of Turkey. In this study, four reinforced concrete frames were produced two storeys, one bay and 3D in 1/6 geometric scale was tested. Since the studied frame was the external frame of the structure, brick infill wall with a window opening was also included. The first specimen was the reference specimen and contained no strengthening and no brick wall. The second specimen was contained brick wall. The third specimen was strengthened with internal steel panel. Finally fourth specimen’s was strengthened with infilled RC shear wall. The test specimens were subjected to reversed cyclic quasi-static lateral loading. Strength of the test specimens were measured and compared. Test results indicated that the strengthened specimens displayed significantly higher lateral strength than the reference specimen considerably.

Abstract: In order characterize the outstanding performance of the three dimensional (3D) hybrid composites, the charpy and flexural test has been carried out. 3D fiber structures have been achieved by using hand lay-up process and machine stitching method. Materials for hand lay-up and machine stitching process were glass fiber, jute fiber, and epoxy resin and nylon fiber respectively. Two dimensional (2D) glass fiber composite and 2D hybrid composite with the same stacking sequence as three dimensional (3D) counterparts have also been fabricated for the comparison of impact and flexural strength. The impact strength of 3D hybrid composite was increased (5-10%) compared with that 2D glass fiber and 2D hybrid composites. The flexural strength and modulus of 3D hybrid composite were increased (5-10%) compared with that of 2D hybrid composites.

Abstract: It is important to obtain the 3d coordinate in the field of measuring. How accurate, fast, convenient to obtain the 3d coordinate affects the accuracy and reliability of measurement directly. Through studying the basic theories of machine vision this paper focus on the study of a stereo vision measurement model based on the intersecting axis. In view of the parameters in the model of binocular stereo vision, this paper uses the Zhang Zhengyou calibration method to calibrate the system of Stereo vision. In order to test the accuracy of the system, this paper measures the distance of two standard circular. Finally, the machining experiment validates the proposed method.

Abstract: 3D dynamic boundary-value problems of linear viscoelasticity and poroelasticity are considered. Laplace integral transform and its numerical inversion are used. Classical viscoelastic models, such as Maxwell model, KelvinVoigt model, standard linear solid model, and model with weakly singular kernel (Abel type) are considered. Boundary integral equations (BIE) method is developed to solve three-dimensional boundary-value problems. A numerical modelling of wave propagation is done by means of boundary element approach.

Abstract: The paper contains a brief introduction to the state of the art in poroelasticity models, in BIE & BEM methods application to solve dynamic problems in Laplace domain. Convolution Quadrature Method is formulated, as well as Runge-Kutta convolution quadrature modification and scheme with a key based on the highly oscillatory quadrature principles. Several approaches to Laplace transform inversion, including based on traditional Euler stepping scheme and Runge-Kutta stepping schemes, are numerically compared. A BIE system of direct approach in Laplace domain is used together with the discretization technique based on the collocation method. The boundary is discretized with the quadrilateral 8-node biquadratic elements. Generalized boundary functions are approximated with the help of the Goldshteyn’s displacement-stress matched model. The time-stepping scheme can rely on the application of convolution theorem as well as integration theorem. By means of the developed software the following 3d poroelastodynamic problem were numerically treated: a Heaviside-shaped longitudinal load acting on the face of a column.