Facilities built in areas affected by earthquake activity, such as tunnels, which have always been an integral part of human life, must withstand both dynamic and static loading. It has led to the need for practical studies on the effects of earthquakes on underground structures and the factors affecting their destruction. For this purpose, in this research, at first different patterns of tunnel’s excavation were investigated and by using Plaxis 2D software and based on Tabas earthquake in Iran, sensitivity analysis on geotechnical parameters of the soil surrounding tunnel such as cohesion, friction angle, unit weight and modulus of elasticity was carried out, and the parameters whose changes have the greatest and least effects on the bending moment changes on the tunnel lining are introduced. The results show that tunnel excavation patterns significantly affect the bending moment, axial forces, displacements, and surface settlement of the tunnel. Often, by dividing tunnel excavation area to small parts, the values of bending moment, axial forces, displacements, and surface settlement of the tunnel decreases in static analysis. Also, outputs of sensitivity analysis on geotechnical parameters of the soil surrounding tunnel showed that modulus of elasticity of the soil surrounding tunnel has the most effect and cohesion changes have the least effect on bending moment induced on tunnel lining..

In the present paper, gas turbine blade made of Inconel 939 superalloy Creep behavior under rotation and thermal stress which is obtained from thermoelastic analysis is studied. Four models including Larson-Miller, Orr-Sherby-Dorn, Manson-Hoferd, and Minimum Commitment Method are used for Creep analysis and their results are compared. At the first step, material constants of these four models are obtained by curve fitting of experimental results provided by COST-50. Then with use of these temperature dependent material constants, finite element model is created and stress due to temperature distribution and blade rotation is determined. Temperature range of blade is obtained from 1050 K to 1200 K. Because obtained von-Mises stress is below the yield stress of Inconel 939 at above temperature range, viscoelastic Creep analysis is done by ABAQUS Creep subroutine. Obtained results show that Larson-Miller and Minimum Commitment Method predict lower Creep rate and Creep strain relative to two other models. Also analysis results show that Creep is more important at points with higher temperature.

Pavements are considered as national heritage of every country، and each year a major part of an organizations budget is spent on repairing، upgrading and maintaining them. Providing adequate funding for this purpose is a challenge which managers and decision-makers are facing with. On the other hand، many years are that rutting as one of the most common types of damages created in this type of pavements. These damages are created over time and due to the accumulation of small permanent deformation which is caused by each load. An increase in permanent deformation that leads to an increase in the depth of groove can cause serious problems in the pavement. Thus، estimating the potential of rutting in the asphalt mixtures in laboratory gets a special significance. In this research، by identifying experiences and research methods of the world and after investigating current situation our country، in addition to determining direct influential parameters، a suitable model for estimating the depth of the groove in asphalt will be presented. The proposed model determining the rutting depth of Hot Mix Asphalt by using dynamic Creep test results. Model validation is verified by using the Artificial Neural Network (ANN).

Gotvand dam is a rock fill dam located in Khoozestan province in Iran on Karun River. It will be constructed on weak mudstone and layers of sandstone. These layers are intermittent of medium strength with uniaxial compressive strength of 15 and 25MPa respectively. Some regional factors as continuous unloading, caused by river flood washed off and horizontal tectonic loading have created a local anticline in the base of the dam. It is estimated that such deformation will last over the time. Therefore, in order to determine Creep parameters assessing the time dependent behavior of the foundation rock during the life of the dam through Numerical and analytical methods is inevitable. In this research, by conducting Creep tests under constant loads the strain- time graphs were produced for the two rock types. Applying the Burger rheological model for both rocks, their Creep parameters were determined. In order to validate the produced data Numerical Modeling was conducted. A comparison between the results of Numerical Modeling and laboratory tests showed that the difference between the two methods is less than 6%. Also the time required for both rocks to enter the tertiary Creep was determined to be 40 days for sandstone under 17.72MPa and 35 days for mudstone under 7.8MPa of load.

micro-mechanical model based on the representative volume element (RVE) is presented to study thetime-dependent and Creep behavior of fibrous composite material. To this aim a finite element model ispresented for analysis of Creep behavior of material in multi-axial Creep are presented. The generalizedplane strain condition is employed to model the behavior of the RVE in axial and transverse normalloading. The governing equations of the problem in the RVE are discretized using the presented finiteelement method and the stiffness and force matrixes are presented. Appropriate boundary conditions areimplied to the RVE in order to consider the transverse and axial loading conditions including Creepbehavior. The Euler explicit method is employed to solve the discretized equations in the time domain.The distribution of micro-stresses and the effect of Creep in re-distribution of the stresses are studied.The steady state Creep behavior of composite in macro-mechanical scale is investigated by analysis of the micromechanical behavior of the RVE. The macro-mechanical Creep behavior of metal matrixcomposite in axial and transverse loading is predicted from the presented micromechanical model.

In recent decades polymeric composites have received considerable attention from different industrial sectors due to their outstanding properties. Despite the multi-purpose properties, polymers undergo Creep even at room temperature which is considered as a disadvantage for their long-term applications.Numerous methods have been suggested by researchers in order to predict Creep in polymeric composites. In this article, a brief review is conducted on fundaments of Creep in polymers and different theoretical methods presented for Creep Modeling in long fiber reinforced laminated composites are categorized. Then, a new method for evaluating long-term Creep in polymeric composites relying on short-term experimental data on pure resin is developed. The developed model is just in need of simple tension-Creep tests on pure resin as input and Creep behavior of pure resin is evaluated accordingly. Then, the results are used to estimate Creep behavior a single composite laminate and finally Creep behavior of laminated composites with arbitrary lay-up configurations is theoretically characterized. In parallel, the capability of micromechanical rules in estimating Creep behavior of composites using its constituent's behavior is investigated. A comparison between published experimental observations and theoretically obtained results imply on proper performance of developed Modeling procedure for analyzing Creep phenomenon in polymeric composites.

In this paper, recommended spiral passive micromixer was designed and simulated. spiral design has the potential to create and strengthen the centrifugal force and the secondary flow. A series of simulations were carried out to evaluate the effects of channel width, channel depth, the gap between loops, and flowrate on the micromixer performance. These features impact the contact area of the two fluids and ultimately lead to an increment in the quality of the mixture. In this study, for the flow rate of 25 μl/min and molecular diffusion coefficient of 1×10-10 m2/s, mixing efficiency of more than 90% is achieved after 30 (approximately one-third of the total channel length). Finally, the optimized design fabricated using proposed 3D printing method.

In many construction projects, it is necessary to excavate the land so that its walls are vertical or close to vertical. Lateral pressure is exerted on these walls due to the movement of the soil behind it. In order to prevent the collapse of the walls of the excavated site and its possible consequences, temporary or permanent structures are implemented, which is called stabilization. Excavations are secured for various reasons. They may be stabilized to protect personnel entering and working in the excavation or to protect buildings or municipal services adjacent to excavation. Over the past years, there have been a large number of excavations in large cities, including Tehran, which were abandoned due to some problems. Furthermore, while some excavations need to be designed for a long time, long-term design basics are not observed during such processes. Stabilization of most of these excavations has been done using anchors. In this method, after placing and implementing the anchors, they are prestressed by applying force. Observations and long-term surveys of these excavations show that in some cases, locking force of anchors decreases, leading to dangers. Therefore, it is very important to know the long-term behavior of anchors in excavations to investigate the stability of these excavations that are prolonged or abandoned for a long time. In this study, field data of the long-term behavior of a excavation in Tehran is used and Numerical Modeling is done based on this case study. Verification and calibration of the Numerical model has been done based on field measurements. Also in this article, relationships based on the results of the Numerical model have been proposed to predict the anchor load in the long term in cohesive coarse-grained soil. The proposed relationships predict well the anchors load at one year after the end of excavation. These relationships are separated to three categories of five strands anchors, six strands anchors and six strands anchors with short length. In the following, the variables affecting the long-term behavior of the anchor loads embedded in the excavation have been studied. These variables include soil properties, depth of the excavation and neighbor surcharge of the excavation. The results of this article, in addition to presenting the relationship for anchor load prediction, include the introduction of variables that affecting long-term behavior. The parametric study shows that with the increase of the angle of internal friction or the increase of soil cohesion, the amount of anchors load decreases over the time. Also, by increasing the depth of the excavation or increasing the neighbor surcharge of the excavation, the load of the anchors decreases less over time. Of course, the impact of excavation depth occurs mostly in the lower anchors and does not affect the anchors of the first row and close to the ground. Studies showed that anchors close to the earth surface have a greater rate of load reduction over time among anchors with the same length and number of strands. Also, among the same anchors, anchors with shorter length experience more load reduction over time.

In this article, the Creep behavior of the AlSiCuNiMg alloy, which has been widely utilized in the piston component of the vehicle engine, has been modelled at different temperatures and various stresse levels. For this objective, the Creep test was done on casted standard specimens, under a constant temperature and a constant tensile loading condition. Temperatures in Creep testing were considered as 250, 275 and 300° C and stress levels were 75, 100 and 125 MPa. Experimental data showed that at a constant stress level, by increasing the temperature, the minimum true strain rate increased and the final true strain decreased; however, at a constant temperature, by increasing the stress level, both mentioned values increased. Based on Modeling results, the temperature-dependent power law was the superior strain rate-based model, with the lowest value for the relative error and the scatter-band. In addition, the Bailey-Norton model had better Modeling results between strain-based models.

Background: To study the Creep behavior for a series of biodegradable nanocomposites, which are used as implantable devices in the body such as bioscrews, is a crucial factor. In the current paper, we are investigating these biomaterials ‐, short‐, time Creep and Creep recover manners‐,in several classic models. Methods: The Creep and Creep recovery behaviors of nanocomposites composed of biodegradable polymer blends, poly (D/L) lactic acid (PDLLA) and polycaprolactone (PCL) reinforced with three different contents of 1, 3 and 6 percent weight percentage bioactive glass nanoparticles (m‐, BGn) were modeled. Several theoretical models including Findley power law, Burgers and Weibull models were used to establish the relations between m‐, BGn dispersion and final Creep and Creep‐, recovery behaviors of nanocomposites. Results: The Findley power law model confirmed that the lowest ‘, A’,and highest ‘, n’,parameters ( A is the amplitude of the transient Creep strain and n is the time exponent) belong to the sample with the highest young modulus and the nanocomposites compared to PDLLA/PCL blends have the lower ‘, A’,and higher ‘, n’,which can be related to retardation effect of m‐, BGn on Creep strains. Besides, the burgers model results illustrated that all viscoelastic and viscoplastic parameters for nanocomposites possess higher values than those of the neat PDLLA/PCL blend. It means that the addition of glass nanoparticles leads to decrease Creep strain, increasing the Burgers model prediction values which have inverse trend with. Moreover, the weibull distribution model results acknowledge that the introduction of m‐, BGn into PDLLA/PCL polymeric blends cause decrease in the viscoelastic strain recovery values. This is due to hindering effects of m‐, BGn on Creep recovery behavior of nanocomposites. Conclusion: The results obtained from Modeling of Creep‐, recovery manners of PDLLA/PCL blend and its nanocomposites approved that the bioactive glass reinforcement nanoparticles play impeding role on Creep and Creep recovery behaviors. Level of evidence: I