The interphase is a region between fibers and a matrix, which has different properties from the matrix and the fibers, but is dependent on them. Considering the interphase region has a significant effect on the accuracy of obtained residual stresses. So far, in order to obtain the micromechanical residual stresses, the interphase properties are considered as an average. In this paper, the properties of the interphase are assumed variable by using a suitable UMAT code in the ABAQUS software. The equations of previous studies that have acquired interphase properties to be variable are used to write the UMAT code. A representative volume element (RVE) in polymer composites is modeled in three phases in the ABAQUS software and the interphase properties are considered as FGM by using the UMAT code. Temperature variation during curing to environment temperature is the only loading factor in the RVE. The matrix, fiber and interphase stresses are obtained in the ABAQUS software. The achieved stresses were compared with the results of previous studies that considered interphase properties as average. Finite element and energy methods were used in previous papers but in the present study just the finite element method with variable interphase properties was use. In addition, residual stress diagrams with the variable interphase properties are plotted to study the effect of the thermal expansion coefficient. The results of this study are similar to those in previous ones, and the curves are improved.

Thermal deformations can reduce the product quality that causes loss of dimensional control and structural integrity. It may increase the manufacturing cost due to unfitted component. This paper deals with the thermal deformation on AA6061 aluminum alloy T-joint after exposed to heat by gas metal arc welding (GMAW) process. In this study, two main parameters; welding speed and welding voltage were used to evaluate the angular distortion, transverse shrinkage and longitudinal shrinkage occurred in GMAW process. The results show that the angular distortion is larger with lowest welding speed. The transverse shrinkage is reduced gradually with increasing of welding speed and transverse shrinkage also linearly increasing with increasing of welding voltage. The magnitude of longitudinal shrinkage is much smaller than angular distortion and transverse shrinkage. Longitudinal shrinkage is insignificantly affected by changing the welding heat input. These findings are important to identify and minimize the unacceptable welding distortion in product manufacturing.

In this article, waste plastics (low-density polyethylene, LDPE) and crumb rubber have been utilized to solve one of the most important environmental issues and to improve bitumen performance properties by these low cost materials. At first, modified bitumen samples were made using high shear mixer, then classic and performance tests were performed on them. It has been observed that adding low-density polyethylene and crumb rubber to the bitumen leads to improvement of classical characteristics. Then, after conducting dynamic shear rheometer test on modified bitumen samples, it was found that the sample containing 3% LDPE and 3% crumb rubber has the best performance. Conducting short-term and long-term aging experiments on samples containing 3% LDPE showed improved performance at high temperature services. After BBR test, more appropriate performance grade is observed for the sample containing 3% LDPE 3% crumb rubber.

This paper deals with the elastica and buckling loads of the nonlinear elastic tapered cantilever columns subjected to an axial load at the free end. The column cross section is rectangular, where the width and depth vary linearly with the column axis. The column material is nonlinear elastic, which obeys the Ludwick’s constitutive law. The ordinary differential equations governing the elastica of buckled column are derived and solved numerically for computing the elastica and buckling loads. Parametric studies for the annealed copper, N.P. 8 aluminum alloy and steel columns are conducted

This work is focused on the influence of different friction stir welding (FSW) parameters on AA6082 T-6 and AA5083-O alloys welding quality, by using Taguchi, Grey Relational and Weight Method. Four welding parameters were investigated, namely tool rotation speed (TRS), welding speed (WS), tool pin profile (TPP) and shoulder diameter (SD). The optimized setting of these input parameters was investigated so that weld parts quality could be optimized. Analysis of variance (ANOVA) was used to investigate the effects of these welding process parameters on response variables, viz. elongation (EL) and ultimate tensile strength (UTS). Single response optimization was carried using Taguchi Technique while grey relational analysis (GRA) was used for simultaneous optimization of two responses. Once the optimal settings of control factors were identified, confirmation experiments were performed for the validation of results. In the multi-response optimization, TRS was found to have the maximum effect (57.9%), followed by WS, SD and TPP. Weight method was applied for providing the priority to the response (i.e. EL and UTS). The response with higher priority presented a weight equal to 0.7, while the lower priority given corresponds to a weight of 0.3.

The use of cement concrete as a stronger and more durable material than asphalt concrete in construction of the pavements has been increased during the past decades. This review paper investigates the effect of various input variables for the design of continuously reinforced concrete pavements. A literature review is prepared based on the efforts performed by many researchers to investigate the effect of different factors including temperature change, shrinkage, material properties of the concrete, and concrete slab/ subbase bond properties on the displacements and stresses in the concrete slab. It is found that the important role of concrete slab/ subbase bond strength has not been investigated properly as compared to other input variables.

In this study, the behavior of two buildings designed with steel structures Buckling Restrained Braced (BRB) and conventional bending frame was studied to analyze their strengths against progressive collapse. The structures were designed and analyzed in accordance with Iranian regulation No. 2800 for the design of buildings. Using nonlinear static pushover analysis, the performance of the structure after removal of the center and the corner columns were investigated and it was demonstrated that removing the corner column provides more critical conditions for the investigated buildings. Furthermore, the use of BRB elements provides better performance for the analyzed buildings due to the ability of BRB in absorbing and dissipating more energy induced from the external loading sources like the earthquake.

This paper presents the effect of Post Weld Heat Treatment (PWHT), pulsed current welding, hybrid welding and vibratory assisted welding in the weld quality, residual stresses and mechanical properties of welded joints. At last, vibratory assisted welding has been suggested to enhance the mechanical properties of welded joints by overcoming the drawbacks in the above stated techniques. Past results showed that the welded test specimens under vibratory conditions exhibited improvements in mechanical properties than the arc welding without vibrations. Finally, some literature gaps are clearly identified and these gaps could help the future generation researchers to do work in the new direction.

Underground gas pipelines are one of the vital parts of each country which surface blasts can break down such pipelines, making destructive explosions and threatening the safety of neighborhood structures and people. In this paper, to enhance the safety of these lines, response of a buried 56-inch diameter high pressure natural gas pipeline to a surface blast was numerically investigated. Besides, the effects of: i) explosive mass, ii) pipeline thickness, iii) burial depth and iv) concrete protective layer on pipeline deformation were parametrically studied. To simulate the problem according to actual explosion events, geometries were modeled in real scales, pipeline properties were predicted with Johnson-Cook strength and failure model and soil strength was determined by Drucker-Prager model. Also, explosive charge and natural gas were modeled with JWL (Jones-Wilkins-Lee) and ideal gas equation of states. For validation of the numerical method, three bench mark experiments were reproduced. Comparison of the numerical results and the experimental data confirmed the accuracy of the numerical method. Results of parametric studies indicated that by increasing the burial depth from 1.4 to 2.2 m, deformation of the pipeline was reduced about 71%. By analyzing the deformation plots, it was found that in a constant explosive mass, burial depth has a greater effect than pipeline thickness on pipeline deformation reduction. It was also shown that using a concrete protective layer may act reversely and increase pipeline destruction. In other words, to enhance the safety of pipelines, a certain thickness of concrete must be used.

A review of some recent data from multiaxial fatigue data from different notched materials is carried out in the paper. The approach based on the strain energy density (SED) averaged over a control volume is first used to summarise uniaxial and multiaxial fatigue strength data of welded joints made of structural steel and aluminium alloys. In all welded joints, the weld toe and weld root regions are modelled like sharp, zero radius, V-notches with different opening angles. The control volume radius is 0.28 mm for structural steels, 0.12 mm for aluminium alloys. Afterwards the SED approach is applied to multi-axial fatigue data from plain and V-notched specimens made of AISI 416 stainless steel (hardened and tempered state), subjected to tension, torsion and combined tension and torsion, both in-phase and out-of-phase. Notched specimens are characterised by a very small root radius, ρ=0.1 mm, which results in high nonlinear effects ahead of the notch tips. All results are summarised in terms of Δ W-N (SED range versus cycles to failure) scatterbands. Together with the new results, a number of multi-axial fatigue data recently obtained from sharply notched specimens made of C40 steel (normalised state) and 39NiCrMo3 steel (hardened and tempered state) are represented with the aim to provide a global synthesis in terms of local SED. Finally a synthesis from Ti6Al4V alloy is carried out showing the capability of the SED approach to be applied also to light alloys.