This work is devoted to the experimental study of a glass/polyester composite laminate under impact shock. Based on a thermodynamic approach, the objective is the evaluation of specific interlaminar delamination energy in a multi-layer composite material under impact loading causing damage to it by cracking. For modeling impact loading, it is used an experimental device based on the principle of Charpy test which is to measure residual energy of a mass movement following a shock at speeds generally between 1 and 4 m/s, on a test piece cut of standardized dimensions requested in bending. Some of available energy is consumed by the rupture of the test piece. The results of this work showed that for impact test, mode I fracture energy is function of impact speed and the load fall energy. These results could be useful in the design of multilayer structures in composite materials subjected to impact loads.

Nano composite materials based on polymers are widely used in restoration martials like dental. Poly methyl methacrylate (PMMA) is one of the most used polymers as dental material. PMMA has disadvantages such as low flexural strength properties and impact strength. In this paper, the influences of additive aluminum oxide and hydroxyapatite nanoparticles on the mechanical and strength properties of PMMA (including flexural strength, impact strength, surface hardness and shrinkage behavior) is studied experimentally. For this purpose, nine standard mechanical testing samples of pure PMMA, PMMA/5HA and PMMA/10HA with various amounts of Nano aluminum oxide (3,6,8 wt.%) were prepared. The results showed that the mechanical properties of hybrid Nano-composites were significantly improved in comparison with the pure samples in a way that optimal Nano-composite with convenience flexural properties and impact strength is obtained. Moreover, the use of nanoparticles results in shrinkage reduction of hybrid Nano-composites in comparison with pure PMMA.

In this paper, the effects of specimen size and crack length on the fracture toughness of polycrystalline graphite are studied. The experimental results reported in the previous studies showed that the fracture toughness of graphite increase in bigger specimen. It has been also demonstrated that the fracture toughness of graphite is nearly identical in specimens with crack length ratio less than 0.7 but decreases for grater crack length ratios. To justify the size and crack length dependency of fracture toughness, the modified form of maximum tangential stress (MMTS) criterion, which makes the use of higher order terms in calculating the stress field around the crack tip is employed. It is shown that the MMTS criterion can provide good estimates for the fracture toughness of graphite obtained from specimen with different sizes. It is also indicated that the MMTS criterion can predict very good the reported experimental fracture toughness data for samples with the crack length ratios less than 0.7.

Beams are the constituent elements of several machine parts and sophisticated structures. In this paper, efforts are made to develop suitable methods that can serve as the basis to detect crack location and to crack size from measured axial vibration data. This method is used to address the inverse problem of assessing the crack location and crack size in various beam structure. The method is based on measurement of axial natural frequencies, which are global parameter and can be easily measured from any point on the structure. In theoretical analysis, the relationship between the natural frequencies, crack location, and crack size has been developed. For identification of crack location and crack size, it was shown that data on the variation of the first two natural frequencies is sufficient. The experimental analysis is done to verify the practical applicability of the theoretical method developed.

Lightweight concrete is a suitable constructional material, which can decrease the weight of buildings and the hazards of earthquake loads. Hence, a large number of research studies have been focused on designing and manufacturing high strength lightweight concretes. In this research using the natural and industrial lightweight aggregates frequently found in the south-east region of Iran (Kerman province), high strength and low cost light weight concretes were manufactured. The effects of aggregate type, aggregate size, and concrete mixture were studied experimentally on the compressive strength of concretes and the density and cost of manufactured samples.

In the present study, the nonlinear forced vibration of symmetric laminated rectangular plates, including Glare fiber metal laminated rectangular plate, is investigated based on the first order shear deformation theory. The boundary condition is considered to be immovable simply support. The Galerkin method is used to obtain the nonlinear ordinary differential equation in terms of an unknown time function. The obtained equation is solved analytically by the multiple time scales method. The obtained results are compared with the numerical solution of the nonlinear ordinary differential equation of motion and a good agreement is found between them.

Finite element method is used to study the free vibration analysis of functionally graded skew plates. The material properties of the skew plates are assumed to vary continuously through their thickness according to a power-law distribution of the volume fractions of the plate constituents. The first order shear deformation theory is used to incorporate the effects of transverse shear deformation and rotary inertia. Convergence study with respect to the number of nodes has been carried out and the results are compared with those from past investigations available in the literature. Two types of functionally graded skew plates - Al/ZrO2 and Al/Al2O3 are considered in this study and the effects of the volume fraction, different external boundary conditions and thickness ratio on the natural frequencies are studied in detail.

In this paper, butt joining of Al5083 to commercially pure copper is investigated by friction stir welding method. The effects of transverse welding speed of the tool on the mechanical properties and microstructure of the joint were studied, experimentally. By examining different circumstances, changes in the joint strength were studied and optimized in term of transverse speed. Based on the obtained results, welding speed can improve or reduce the joint strength and an optimum value can be found for the welding speed. Welded Joint that was conducted at the rotation speed of 800 RPM and tool traverse speed of 60 mm min?1 had the highest tensile strength (i.e. about 98% of the weak base metal). Intermetallic compounds were formed in the stir zone and XRD results indicated that Al4Cu9 and Al2Cu were the intermetallic compounds in the stir zone. Micro-cracks formed around the intimatelic particles were observed in the section of joint.

A new fracture test specimen is suggested and analyzed using finite element method. The mode I and mode II stress intensity factors as well as the T-stress were calculated for three geometries and loading conditions. It is shown that the specimen, called single edge cracked ring (SECR), covers different mixed mode loading conditions from pure mode I to pure mode II. The SECR specimen also covers negative and positive values of T-stresses. From the practical view point, the suggested specimen can be used easily for mixed mode II fracture tests.

In this paper, an extended forming limit stress diagram (EFLSD) was applied to predict neck initiation failure in tube hydroforming of metal bellows. The proposed EFLSD was used in conjunction with ABAQUS/ EXPLICIT finite element simulations to predict the onset of necking in tube hydroforming of metal bellows. The amount of calibration pressure and axial feeding required to produce an acceptable part in finite element method (FEM) were compared with the published experimental data and a satisfactory agreement between the FEM and published test results was achieved. Therefore, the present approach can be used as a reliable criterion for designing metal bellows hydroforming processes and reducing the number of costly trials.