Mesut Uyaner

Dynamic Response of Laminated Composites Subjected to Low-velocity Impact

The dynamic response of E-glass/epoxy composite laminates under low velocity impact was experimentally investigated. Uni-directionally reinforced E-glass/epoxy laminates with the stacking sequence of [0°/-45°/45°/0°/ 90°/0°/45°/-45°/0°] s were studied with the aim of an impact test. The impact tests performed at impactor mass (30 kg) for three different impact velocities (2.0, 2.5, and 3.0 m/s) were conducted with a specially developed vertical drop weight testing machine. The radius of the impactor with a semispherical nose was 12 mm. Sample plate specimens that had dimensions of 180 × 50, 180 × 100, and 180 × 150 mm were clamped from two opposite sides while the other two sides were free. The center of each plate was exposed to impact loading. The differences in the impact responses of specimens with varying width are characterized. Moreover, it was shown that the peak force increased with the increase of the width of the specimen.

Plastic zones in a transversely isotropic solid cylinder containing a ring-shaped crack

In this study, a problem of a ring shaped-crack contained in a infinitely long solid cylinder of elastic perfectly-plastic material is considered.The problem is formulated for a tranversely isotropic matrial by using integral transform technique under uniform load. Due to the geometry of the configuration, Hankel and Fourier integral transform techniques are chosen and the problem is reduced to a singular integral equation. This integral equation is solved numerically by using Gaussian Quadrature Formulae and the values are evaluated for various for discrete points. The plastic zone widths are obtained by using the plastic strip model. They are plotted for various ring-shaped crack sizes and transversely isotropic matrials. It is found that the width of the plastic zone at the inner tip of the crack is greater than the outer one.

The Effects of Cutting Speed and Depth of Cut on Machinability Characteristics of Austempered Ductile Iron

Ductile iron can acquire enhanced thermal and mechanical properties from austempering heat treatment. The present study aims to identify the function of different cutting parameters affecting machinability and to quantify its effects. Turning was performed to test machinability according to the ISO3685-1993 (E) standard. After austenitizing at 900 C for 90 min, austempered ductile iron (ADI) specimens were quenched in a salt bath at 380 C for 90 min. The cutting force signals along three directions were measured in real time, whereas flank wear and surface roughness were measured offline. For the cutting parameters, the cutting speed and depth of cut were varied, but the feed rate was kept constant. In the flank wear tests, machining length was corresponded to tool life. In addition, in order to find out the effect of cutting parameters on surface roughness (Ra), tangential force (Ft), and flank wear (VB) during turning, response surface methodology (RSM) was utilized by using experimental data. The effect of the depth of cut on the surface roughness was negligible but considerable in the cutting forces. The increased cutting speed produced a positive effect on surface roughness. It is found that the cutting speed was the dominant factor on the surface roughness, tangential force, and flank wear. [DOI: 10.1115/1.4005805]

Elastic-Plastic Stress Analysis of Woven Cr-Ni-reinforced Composite-laminated Plates with a Hole under In-plane Loading

An elastic-plastic stress analysis and the expansion of plastic zone in layers of woven steel fiber-reinforced thermoplastic matrix-laminated plates are studied by using the Finite Element Method and the First-order shear deformation theory for small deformations. Composite structures consisting of woven Cr-Ni wire as a fiber and F2.12 low-density polyethylene as a thermoplastic matrix were manufactured by hot-press molding. The mechanical properties were experimentally determined. The effect of orientation angle and symmetric-antisymmetric structures were investigated. It is assumed that the laminated plates are subjected to in-plane uniform loads. Loading is gradually increased from yield point of the plate as 0.01 MPa at each load step. Load steps are chosen as 300, 400, and 500.

Elasto-plastic stress analysis of aluminum metal-matrix composite plate under in-plane loading

Composite structure consisting of stainless steel fiber and aluminum matrix is manufactured by hot-press molding. The mechanical properties were determined experimentally. The effect of orientation angle is investigated under in-plane loading. An elastic-plastic numerical solution has been carried out by finite element method (FEM). The expansion of plastic zones has been illustrated in figures.

The Effect of Build Up Edge Formation on the Machining Characteristics in Austempered Ferritic Ductile Iron

In this study, chip formation mechanism during the machining of austempered ferritic DI and the effect of the emerging chip morphology on such machining properties as surface roughness and cutting forces has been scrutinized. After austenitizing at 900 °C for 90 min, DI specimens were austempered in a salt bath at 380 °C for 90 min. Chip roots were produced by using a quick stop device during the machining of austempered specimens in different cutting speeds. The metallographies of these specimens were performed and chip morphologies were examined. The fact that the cutting speed increased led to a decrease in built-up edge formation. Depending on this fact, it was detected that the change in built-up edge thickness substantially affected the surface roughness and cutting forces. It was also detected that during the machining, with the effect of cutting forces and stress, spheroidal graphites were broken off in the chip and lost their sphericity and so that the chip became fragile and unstable and grafites here displayed a lubricant feature.© 2013 ASME

Contact Problem for a Transversely Isotropic Cylinder Radially Compressed by a Rigid Toroidal Indenter

In this study, an elastostatic contact problem for a radially compressed transversely isotropic cylinder subjected to radial compression through a circumferential indenter is considered. The extent of the contact region and the stress distribution are sought. The problem is formulated for an elastic cylinder in the absence of body forces. It is assumed that the contact between the cylinder and the rigid indenter is frictionless and only compressive normal tractions can be transmitted through the interface. Due to the geometry of the configuration, Fourier transform techniques are chosen. The problem is reduced to a singular integral equation. It is reduced to linear algebraic equations system by using Gauss Chebyshev Integration Formulae. This system is solved by using the Gauss Elimination method. The values are evaluated for various discrete points. Numerical results for the radial stress and the distance characterizing the contact area are given in graphical form for single circular smooth indenter.

Plastic zones for a penny-shaped crack in a transversely isotropic layer bonded between two isotropic half spaces☆

In this paper, a problem in an elastic-perfectly plastic dissimilar layered medium is considered. It is assumed that a transversely isotropic layer is sandwiched between two isotropic semi-infinite half spaces, and contains a penny-shaped crack located in its mid-plane. The problem is formulated by using integral transform technique under uniform load and reduced to a singular integral equation. This integral equation is solved numerically by using Gaussian Quadrature Formulae. The plastic zones are evaluated by using the plastic strip model. They are plotted for various penny-shaped crack sizes and transversely isotropic materials.

Impact resistance of gypsum board subjected to low velocity impact

Original scientific paper The aim of this study was to investigate the impact resistance and damage behaviour of gypsum and composite gypsum boards subjected to low velocity impact. Low velocity impact tests were performed on four different board materials which can be listed as gypsum boards, gypsum+75 gr/m2 mesh boards, gypsum+wallpaper boards and gypsum+75 gr/m2 mesh+wallpaper boards. Indenter used in the impact tests was 24 mm in diameter and has semi spherical tip geometry. Gypsum and composite gypsum boards were bonded in 500×400 mm sizes and simply supported at four sides. Various energy levels, i.e. 2, 4, 6, 8, 10 and 12 J were applied to the centre of each board. As a result of low speed impact tests, impact force-time and force-displacement variations were obtained and the damaged regions of the samples were examined. Penetration thresholds and perforation thresholds of gypsum and composite gypsum board samples were determined by using Energy Profile Method (EPM). The effect of adding mesh and wallpaper into the gypsum board on stab and puncture limits was evaluated. Around 62.40 % increase occurred on gypsum+mesh+wallpaper board comparing to gypsum board in perforation thresholds.

Experimental study of the impact behavior of laminated composites stricken by sharp impactors

Abstract In this study, the influence of the impactor shape on the dynamic response of E-glass/epoxy laminates was investigated. Composite samples were impacted using steel 90° and 120° conical, 24 mm and 12 mm in diameter hemispherical, pyramidal impactors via a specially developed drop weight test machine. The impact tests were performed at impactor mass (20 kg) for impact velocity (2.5 m/s). Plate specimens consisting of 18 plies for tests (180×50 mm) with a nominal thickness (7 mm) were used. Contact force-time and contact force-deflection data obtained from the experiments were interpreted. It was found that the contact force was smaller in the 90° conical impactor while it was bigger in the 24 mm hemispherical one. Absorbed energies were also investigated. The absorbed energy obtained for pyramidal impactor was greater than that of the others. Furthermore, overall damage areas caused by the impactor were evaluated.