Stress Analysis

PACS. 05.40.-a – Fluctuation phenomena, random processes, noise, and Brownian motion. PACS. 45.70.Cc – Static sandpiles; granular compaction. PACS. 83.80.Fg – Granular solids. Abstract. – We study the stress profile of an ordered two-dimensional packing of beads in response to the application of a vertical overload localized at its top surface. Disorder is introduced through the Coulombic friction between the grains which gives some indeterminacy and allows the choice of one constrained random number per grain in the calculation of the contact forces. The so-called “multi-agent ” technique we use lets us deal with systems as large as 1000×1000 grains. We show that the average response profile has a double-peaked structure. At large depth z, the position of these peaks grows with cz, while their widths scales like Dz. c and D are analogous to “propagation ” and “diffusion ” coefficients. Their values depend on that of the friction coefficient µ. At small µ, we get c0 − c ∝ µ and D ∝ ...

As well as acting as a moderator and reflector, graphite is used as a structural component in many gas-cooled fission nuclear reactors. Therefore the ability to predict the structural integrity of the many graphite components which make up a graphite reactor core is important in safety case assessments and reactor core life prediction. This involves the prediction of the service

A finite difference technique is developed to predict the second stage creep displacement rates and stress analysis of a short fiber metal matrix composite subjecting to a constant axial load through a micromechanical approach. The technique is capable to take into account the presence of interfacial debonding as one of the main factors affecting the creep performance of short fiber composites. The exponential law is adopted to describe the matrix creep behavior. Also, a model for prediction of interfacial debonding at fiber/matrix interface is developed using a stress based method. The obtained results could greatly help to better understand the flow pattern of matrix material and the load transfer mechanism between fiber and matrix with and without the presence of interfacial debond. The predicted strain rate by the proposed approach exhibits good agreement with the experimental results.

In Industries the Turbines are used for convertin g the forms of energy, the Blades are the key eleme nts for turbines where the blades of the turbines experienc es different types of failures. The common reason o f these types of failures is the thermal stress which is experien ced by the blades. The breakage point of blades dep ends upon the material used to make it. If we can have thermal st ress analysis of the blade materials then it is eas y to determine that under different conditions & up to which point , materials can resist. Having this information, a system having turbine can be analysed, according to that material s can be used to make blades. These blades can resi st better than any other blades which can be used. In this work, m odels have been generated based on actual measurement of the blades which are used in industries for steam turbi nes. Applying the properties of different materials on these models, the simulation of thermal stress has been o bserved in this pa...

Une nouvelle approche du dimensionnement des structures de chaussees, qui repose sur un algorithme de minimisation integrant les exigences mecaniques classiques et un critere cout de structure, est proposee. Un probleme d'optimisation non lineaire avec contraintes est ainsi pose et traite. Dans cette modelisation, la demarche suivie pour l'optimisation est fondee sur une methode iterative de minimisation (methode de Han Powel). Le programme Alize III developpe par le LCPC est adopte pour la modelisation mecanique de la structure de chaussees alors que, pour la modelisation des parametres exterieurs, la demarche retenue est analogue a celle de l'approche francaise. Certaines caracteristiques sont ainsi determinees de maniere a adapter les calculs aux besoins specifiques de la Tunisie. Un nouveau programme de calcul de structures de chaussees est ainsi propose et valide. Deux exemples de dimensionnement sont presentes. Le premier est un calcul comparatif relatif a une stru...

Stress is a condition of mental pressure for particular individual facing problems from envi­ronmental and social well-being which leads to so many diseases. Young age is the critical period because at this time youth faces lots of changes in his/her life. They are expected to be the elites in the society. Thus, they should enhance their stress management abilities so as to live a healthy life after entering the society. When a child enters into the youth age, they need to not only adapt themselves to the new life and new environment but also be familiar with many new people, events, and things. The life stress on them is considerable. Therefore, understanding the sources of stress among them and how they can cope with the stress is very important. The researcher found that the stress mainly comes from academic tests, interpersonal relations, relationship problems, life changes, and career exploration. Such stress may usually cause psychological, physical, and behavioral problems. T...

A variety of package parameters impact package reliability. One of the parameters that does not get much attention is the variations in package design that are assembly and vendor related. It was shown in this study that the solder pad size plays a big role in solder joint reliability. The difference in solder pad size due to different vendors and processes can affect the reliability considerably. In certain cases, the pad size effect can be so significant that it will override the effect of substrate thickness. Our work indicates that in order to obtain good correlations between predictive engineering results and reliability tests data, this factor should not be ignored. In this paper, finite element analysis was used to study the impact of substrate thickness on solder reliability for flip-chip PBGA (plastic ball grid array) packages. The simulation results were experimentally validated with moire interferometry. Both numerical and experimental results indicated that better solder reliability could be achieved by using thicker substrate. However, the size of BGA solder pad was found to be crucial to BGA life. In order to achieve higher C5 (controlled collapse chip carrier connection) reliability, a larger solder pad is preferred