Strain-softening material models have conventionally had a pathological mesh sensitivity in finite element simulations and composite materials are indifferent to this problem. Spurious localization is inherent to the structural problem in strain-driven softening. This limitation is caused as the partial differential equations (that govern the structural problem) become ill-posed as the tangent modulus becomes negative, for which uniqueness of the solution with respect to the spatial discretization is lost. This causes the numerical results to unrealistically concentrate in a single layer of elements. A basic theory of overcoming mesh sensitivity is the non-local continuum theory. In this work, three different non-local models with isotropic weight function have been proposed and implemented to work in conjunction with a composite micro-mechanical material model. The effect of a weighing function in each of these formulations has been studied in detail. All three non-local formulations have been observed to produce a nice smeared effect of damage unlike the local damage models.

This work shows a free-body model for tolerance analysis, that uses the force free-body diagrams and the functional equations’ sensitivities, by simulating the geometrical tolerances together with the dimensional ones. The geometrical tolerances were related to the deviations due to the manufacturing process (i.e. the manufacturing signature). Moreover, weight and friction forces were simulated too. A sensitivity analysis on the developed free body model aimed to evaluate the number of points to discretize the circular bodies and how to calculate the point clouds barycentre in order to reduce the simulation time. A case study was used to exemplify the application of the proposed free-body method with and without considering the manufacturing signature. The results show that the free body model is able to solve assembly problems and the manufacturing signature significantly influences the values of the functional requirement on the product and, therefore, it is impossible to neglect it.

This paper presents a new hybrid double mixed stress (4f-HMS) model, for the static analysis of isotropic plane structures, in which it is assumed a physically and geometrically linear behaviour. The main improvement of this model is, it approximates independently the three most important fields in the domain, more specifically the strain field, the stress field and the displacement field of each element. The displacements along the static boundary, considered to include inter-element boundaries, are also directly approximated. For the approximation functions in the space domain, a complete set of orthonormal Legendre polynomials are used. The adoption of these functions enables the use of analytical closed form solutions, for the computation of all linear structural operators, and leads to the development of very effective p- refinement procedures. The model being discussed is tested in terms of convergence capabilities using classical elastic strain energy and other common variables, in which the monotonic convergence is tested. To validate the model and to illustrate its potential, several numerical examples are discussed and comparisons are made, with solutions obtained using analytical results and other known finite element formulations.

In this research a new electronic based mechanism for vehicle suspension system is designd. The aims are to improve passengers’ safety and comfort. The proposed system is developed for proactive rapid reaction of suspension system which can readjust the height of chassis while confronting with wrong conditions of driving such as unflatted road, rainy or snowy road profile. The results show that the proposed mechanism can successfully increase the stability of the car by readjusting the height of the the chassis and center of the gravity of vehicle while turning.

Inappropriate use of gravity and lateral load-bearing system and the use of inappropriate materials may increase in weight of the structure. Thus, we see an increase in gravity and lateral forces and consequently the beam and column dimensions of elements increase. In this paper, by taking several samples of buildings with steel frames and number of different floors and use of different materials as well as various gravity and lateral load-bearing systems this issue was investigated. It was observed that by the use of steel bracing system in both directions of buildings with steel frames; each different load-bearing results in minimum weight loading per unit surface of the skeleton of structure. It was also observed more effect of lightweight construction by increasing the number of floors for all lateral load-bearing systems. Effects of lightweight construction for different lateral load-bearing systems was investigated and we observed that the effects of lightweight construction commonly used for buildings with moment frame system in both directions were more than the rest of the buildings with lateral load-bearing systems.

In this paper, the first and second stage compressor blades of a gas turbine were studied by the experimental and numerical modal analyses. At first, the geometric models of these blades were generated by the 3D scanner and then the mode shapes and the natural frequencies of each blade were extracted by a series of numerical modal analyses. The numerical results were compared with the data obtained from the experimental modal analysis and the validity and accuracy of the developed numerical models were confirmed. Unlike most studies that use fixed-free boundary condition for performing a modal analysis, this objective was pursued by applying a free-free boundary condition. This study also investigated the effect of using wax or glue for mounting the accelerometer on the blade by assessing the FRF curves obtained from the modal tests in the frequency range of 0-10000 Hz. The sensitivity of the test results to applying free-free boundary condition, the number of accelerometers and their positions were investigated by defining three modal test configurations. The results obtained by these test configurations were compared with the results of numerical analyses and finally, the best configuration for the modal test of the studied compressor blade was determined.

The problem of interaction of rod centralizers of casing with a well wall is considered. The paper aims at studying the ways of fastening of centralizer’s ends on the parameters of its rigidity and strength. Knowledge of these characteristics is necessary for the assessment of casing column drift and well completion quality. For simulation of the working links of the centralizers, the classical linear theory of smooth rods, rigid along the axis and elastic on bending is used. Stress-strain state of bow-type rod with six different variants of fastening under conditions of point contact is studied. The analytical relations between the contact force and the mutual approach of the column and the well wall, as well as the expressions for the admissible contact loads, are established. The way of fastening the rod significantly influences these characteristics; in particular, the fact of the presence or absence of freedom of mutual movement of its ends along the pipe is decisive. The engineering formulas, which serve as two-side estimations of the rigidity and strength of the real structures of centering devices, are obtained. A comparative analysis of mechanical properties of centralizers has been conducted.

The low cycle fatigue (LCF) resistance of two different metal matrix composite (MMC) of AA6063 with 2% and 8% by volume silicon carbide (SiCp) particles having particulate size of 37 micron (400 mesh) at room temperature condition has been evaluated under fully reversed strain control testing. The influence of volume fraction (2 and 8 vol%) and strain ratio (R= -1) are examined. Increasing the content of SiCp results in the degradation of strain control fatigue properties while the transition fatigue life increases. Fatigued samples are examined using scanning electron microscopy in order to understand the failure mechanism (SEM). Microstructural features and failure mechanisms studied through scanning electron microscopy (SEM) confirmed low cycle fatigue failure nature.

This research presents detailed notes on the penetrating geological formations of the wellbore. Logs can be presented in two forms of good geological logs, means visual inspection of surface-carrying samples, and geophysical logs, means physical measurements by instruments that are lowered into holes. Logs that are created during drilling are called real-time logs. LWD tool is produced from real-time data transmitted to the surface computer from downhole. Three common services are Natural Gamma Ray, Resistivity, and Porosity and Bulk Density. The output of an LWD service is a log. A log is a graphical representation of the properties of the formation. Some factors that affect data quality are Depth Calculation, Sensor Malfunction and LWD Tools Measurements Fault. During drilling, borehole path monitoring is the important thing to be maintained because the quality of LWD data is critical for the success of any LWD job. Therefore, the field engineer has to understand the factors that affect data quality. Quality Control Process is the key to ensure that the tools are working properly.

The main aim of this paper is to present a novel multi-objective gray wolf optimization (MOGWO) by utilizing the Kriging meta-model. To this end, surrogate models are used in Multi-Objective Gray Wolf Optimizer as the fitness function. The meta-model is obtained based on exact analysis and numerical simulations. Inheritable Latin Hypercube Design (ILHD) is used as the design of experiments for generation and testing the Kriging model. Then, sensitivity analysis is done to evaluate the effect of design parameter on system responses. The sensitivity analysis leads to appropriate selection of optimization design variables. Hence, the MOGWO algorithm is applied to the problem, the set of non-dominated optimal points are obtained as Pareto Front and one optimal point is selected based on the minimum distance approach. The most important purpose of the methodology is to improve the time consuming in multi-objective optimization problems. In conclusion, for the design of hydrazine catalyst bed was utilized from the proposed methodology. In case, design variables are catalyst bed pellet diameter, loading factor, thrust chamber pressure and Reaction efficiency and objective functions are increasing performance and reducing mass and pressure drop. The results of optimal catalyst bed parameters and also corresponding value of objective functions are shown the performance of methodology in the space propulsion system applications.