Search results for: surface stress.

Authors: Gürol Önal, Ahmet Avcı

Abstract:

This paper presented the results of an experimental investigation into the axial fatigue behavior of a 5086 aluminum alloy which have several notch-aspect ratios a0/c0 and notch thickness ratio a/t with semi-elliptical surface cracks. Tests were conducted in la b air for stress levels of 50 % of their yield strength. Experiments were carried out for various notch to thickness ratios. Crack growth rates of test specimens both in surface and depth directions were determined by using die penetration method. Fuzzy Logic method was used to predict the deep direction crack growth because the dept of the crack is considerably difficult to measure.

Keywords: Axial fatigue, Crack growth rate, surface crack, Al-Mg alloy.

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Authors: Shi-hong Lu, Chao-xun Liu, Yi-feng Zhu

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Ultrasonic shot peening (USP) on AALY12 sheet was studied. Several parameters (arc heights, surface roughness, surface topography and micro hardness) with different USP process parameters were measured. The research proposes that radius of curvature of shot peened sheet increases with time and electric current decreasing, while increases with pin diameter increasing, and radius of curvature reaches a saturation level after a specific processing time and electric current. An empirical model of the relationship between radius of curvature and pin diameter, electric current, time was also obtained. The research shows that the increment of surface and vertical micro hardness of material is more obvious with longer time and higher value of electric current, which can be up to 20% and 28% respectively.

Keywords: USP forming, surface properties, radius of curvature, residual stress.

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Authors: N. P. Dhull, K. Gupta, R. Soni, D. K. Rahi, S. K. Soni

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The aim of the present work was to statistically design an autotrophic medium for maximum biomass production by Chlorella pyrenoidosa using response surface methodology. After evaluating one factor at a time approach, K2HPO4, KNO3, MgSO4.7H2O and NaHCO3 were preferred over the other components of the fog’s medium as most critical autotrophic medium components. The study showed that the maximum biomass yield was achieved while the concentrations of MgSO4.7H2O, K2HPO4, KNO3 and NaHCO3 were 0.409 g/L, 0.24 g/L, 1.033 g/L, and 3.265 g/L, respectively. The study reported that the biomass productivity of C. pyrenoidosa improved from 0.14 g/L in defined fog’s medium to 1.40 g/L in modified fog’s medium resulting 10 fold increase. The biochemical composition biosynthesis of C. pyrenoidosa was altered using nitrogen limiting stress bringing about 5.23 fold increase in lipid content than control (cell without stress), as analyzed by FTIR integration method.

Keywords: Autotrophic condition, Chlorella pyrenoidosa, FTIR, Response Surface Methodology, Optimization.

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Authors: Elsa Eka Putri, N.S.V Kameswara Rao, M. A. Mannan

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The objective of this study is to evaluate the threshold stress of the clay with sand subgrade soil. Threshold stress can be defined as the stress level above which cyclic loading leads to excessive deformation and eventual failure. The thickness determination of highways formations using the threshold stress approach is a more realistic assessment of the soil behaviour because it is subjected to repeated loadings from moving vehicles. Threshold stress can be evaluated by plastic strain criterion, which is based on the accumulated plastic strain behaviour during cyclic loadings [1]. Several conditions of the all-round pressure the subgrade soil namely, zero confinement, low all-round pressure and high all-round pressure are investigated. The threshold stresses of various soil conditions are determined. Threshold stress of the soil are 60%, 31% and 38.6% for unconfined partially saturated sample, low effective stress saturated sample, high effective stress saturated sample respectively.

Keywords: threshold stress, cyclic loading, pore water pressure.

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Authors: Mojtaba Ghodsi, Hamidreza Ziaifar, Morteza Mohammadzaheri, Payam Soltani

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In this paper, the performance of a medium power (25 kW/25 kHz) hybrid inverter with a reactive transformer is investigated. To analyze the sensitivity of the inverster, the RSM technique is employed to manifest the effective factors in the inverter to minimize current passing through the Insulated Bipolar Gate Transistors (IGBTs) (current stress). It is revealed that the ratio of the axillary inductor to the effective inductance of resonant inverter (N), is the most effective parameter to minimize the current stress in this type of inverter. In practice, proper selection of N mitigates the current stress over IGBTs by five times. This reduction is very helpful to keep the IGBTs at normal temperatures.

Keywords: Analytical analysis, hybrid resonant inverter, reactive transformer, response surface method.

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Authors: Elnaz Afshari, Siamak Najarian, Naser Simforoosh, Siamak Hajizadeh Farkoush

Abstract:

Minimally invasive surgery (MIS) is now being widely used as a preferred choice for various types of operations. The need to detect various tactile properties, justifies the key role of tactile sensing that is currently missing in MIS. In this regard, Laparoscopy is one of the methods of minimally invasive surgery that can be used in kidney stone removal surgeries. At this moment, determination of the exact location of stone during laparoscopy is one of the limitations of this method that no scientific solution has been found for so far. Artificial tactile sensing is a new method for obtaining the characteristics of a hard object embedded in a soft tissue. Artificial palpation is an important application of artificial tactile sensing that can be used in different types of surgeries. In this study, a new method for determining the exact location of stone during laparoscopy is presented. In the present study, the effects of stone existence on the surface of kidney were investigated using conceptual 3D model of kidney containing a simulated stone. Having imitated palpation and modeled it conceptually, indications of stone existence that appear on the surface of kidney were determined. A number of different cases were created and solved by the software and using stress distribution contours and stress graphs, it is illustrated that the created stress patterns on the surface of kidney show not only the existence of stone inside, but also its exact location. So three-dimensional analysis leads to a novel method of predicting the exact location of stone and can be directly applied to the incorporation of tactile sensing in artificial palpation, helping surgeons in non-invasive procedures.

Keywords: Kidney Stone, Laparoscopic Surgery, Artificial Tactile Sensing, Finite Element Method.

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Authors: N. Rezvani, A. Sorooshzadeh, N. Farhadi

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Saffron (Crocus sativus) is cultivated as spices, medicinal and aromatic plant species. At autumn season, heavy rainfall can cause flooding stress and inhibits growth of saffron. Thus this research was conducted to study the effect of silver ion (as an ethylene inhibitor) on growth of saffron under flooding conditions. The corms of saffron were soaked with one concentration of nano silver (0, 40, 80 or 120 ppm) and then planting under flooding stress or non flooding stress conditions. Results showed that number of roots, root length, root fresh and dry weight, leaves fresh and dry weight were reduced by 10 day flooding stress. Soaking saffron corms with 40 or 80 ppm concentration of nano silver rewarded the effect of flooding stress on the root number, by increasing it. Furthermore, 40 ppm of nano silver increased root length in stress. Nano silver 80 ppm in flooding stress, increased leaves dry weight.

Keywords: Flooding stress, Nano-silver, Saffron.

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Authors: Sadílek M., Čep R.

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This work deals with problems of tool axis inclination angles in ball-end milling. Tool axis inclination angle contributes to improvement of functional surface properties (surface integrity - surface roughness, residual stress, micro hardness, etc.), decreasing cutting forces and improving production. By milling with ball-end milling tool, using standard way of cutting, when work piece and cutting tool contain right angle, we have zero cutting speed on edge. At this point cutting tool only pushes material into the work piece. Here we can observe the following undesirable effects - chip contraction, increasing of cutting temperature, increasing vibrations or creation of built-up edge. These effects have negative results – low quality of surface and decreasing of tool life (in the worse case even it is pinching out). These effects can be eliminated with the tilt of cutting tool or tilt of work piece.

Keywords: CAD/CAM system, tool axis inclination angle, ballend milling, surface roughness, cutting forces.

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Authors: S. Farid F. Mojtahedi, Ali Khosravi, Behnaz Naeimian, S. Adel A. Hosseini

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Land subsidence is a gradual settling or sudden sinking of the land surface from changes that take place underground. There are different causes of land subsidence; most notably, ground-water overdraft and severe weather conditions. Subsidence of the land surface due to ground water overdraft is caused by an increase in the intergranular pressure in unconsolidated aquifers, which results in a loss of buoyancy of solid particles in the zone dewatered by the falling water table and accordingly compaction of the aquifer. On the other hand, exploitation of underground water may result in significant changes in degree of saturation of soil layers above the water table, increasing the effective stress in these layers, and considerable soil settlements. This study focuses on estimation of soil moisture at surface using different methods. Specifically, different methods for the estimation of moisture content at the soil surface, as an important term to solve Richard’s equation and estimate soil moisture profile are presented, and their results are discussed through comparison with field measurements obtained from Yanco1 station in south-eastern Australia. Surface soil moisture is not easy to measure at the spatial scale of a catchment. Due to the heterogeneity of soil type, land use, and topography, surface soil moisture may change considerably in space and time.

Keywords: Artificial neural network, empirical method, remote sensing, surface soil moisture, unsaturated soil.

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Authors: Ali Baladi, Alireza Fallahi Arezoodar

Abstract:

in dissimilar material joints, failure often occurs along the interface between two materials due to stress singularity. Stress distribution and its concentration depend on materials and geometry of the junction. Inhomogenity of stress distribution at the interface of junction of two materials with different elastic modules and stress concentration in this zone are the main factors resulting in rupture of the junction. Effect of joining angle in the interface of aluminum-polycarbonate will be discussed in this paper. Computer simulation and finite element analysis by ABAQUS showed that convex interfacial joint leads to stress reduction at junction corners in compare with straight joint. This finding is confirmed by photoelastic experimental results.

Keywords: Elastic Modules, Stress Concentration, JoiningAngle, Photoelastic.

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Authors: Felipe V. Díaz, Claudio A. Mammana, Armando P. M. Guidobono, Raúl E. Bolmaro

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Through a proper analysis of residual strain and stress distributions obtained at the surface of high speed milled specimens of AA 6082–T6 aluminium alloy, the performance of an improved indentation method is evaluated. This method integrates a special device of indentation to a universal measuring machine. The mentioned device allows introducing elongated indents allowing to diminish the absolute error of measurement. It must be noted that the present method offers the great advantage of avoiding both the specific equipment and highly qualified personnel, and their inherent high costs. In this work, the cutting tool geometry and high speed parameters are selected to introduce reduced plastic damage. Through the variation of the depth of cut, the stability of the shapes adopted by the residual strain and stress distributions is evaluated. The results show that the strain and stress distributions remain unchanged, compressive and small. Moreover, these distributions reveal a similar asymmetry when the gradients corresponding to conventional and climb cutting zones are compared.

Keywords: Residual strain, residual stress, high speed milling, indentation methods, aluminium alloys.

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Authors: Md Abdullah Al Faruque, Ram Balachandar

Abstract:

The present study was carried out to understand the extent of effect of roughness and Reynolds number in open channel flow (OCF). To this extent, four different types of bed surface conditions consisting smooth, distributed roughness, continuous roughness, natural sand bed and two different Reynolds number for each bed surfaces were adopted in this study. Particular attention was given on mean velocity, turbulence intensity, Reynolds shear stress, correlation, higher order moments and quadrant analysis. Further, the extent of influence of roughness and Reynolds number in the depth-wise direction also studied. Increasing Reynolds shear stress near rough beds are noticed due to arrays of discrete roughness elements and flow over these elements generating a series of wakes which contributes to the generation of significantly higher Reynolds shear stress.

Keywords: Bed roughness, ejection, sweep, open channel flow, Reynolds Shear Stress, turbulent boundary layer, velocity triple product.

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Authors: Ali. Marjani, M. Farsi, M. Rahimizadeh

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Chickpea (Cicer arietinum L.) is one of the important grain legume crops in the world. However, drought stress is a serious threat to chickpea production, and development of drought-resistant varieties is a necessity. Field experiments were conducted to evaluate the response of 8 chickpea genotypes (MCC* 696, 537, 80, 283, 392, 361, 252, 397) and drought stress (S1: non-stress, S2: stress at vegetative growth stage, S3: stress at early bloom, S4: stress at early pod visible) at different growth stages. Experiment was arranged in split plot design with four replications. Difference among the drought stress time was found to be significant for investigated traits except biological yield. Differences were observed for genotypes in flowering time, pod information time, physiological maturation time and yield. Plant height reduced due to drought stress in vegetative growth stage. Stem dry weight reduced due to drought stress in pod visibly. Flowering time, maturation time, pod number, number of seed per plant and yield cause of drought stress in flowering was also reduced. The correlation between yield and number of seed per plant and biological yield was positive. The MCC283 and MCC696 were the high-tolerance genotypes. These results demonstrated that drought stress delayed phonological growth in chickpea and that flowering stage is sensitive.

Keywords: Chickpea, drought stress, growth stage, tolerance.

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Authors: M. H. Kargarnovin, K. Momeni

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The study of the stress distribution on a hollow cylindrical fiber placed in a composite material is considered in this work and an analytical solution for this stress distribution has been constructed. Finally some parameters such as fiber-s thickness and fiber-s length are considered and their effects on the distribution of stress have been investigated. For finding the governing relations, continuity equations for the axisymmetric problem in cylindrical coordinate (r,o,z) are considered. Then by assuming some conditions and solving the governing equations and applying the boundary conditions, an equation relates the stress applied to the representative volume element with the stress distribution on the fiber has been found.

Keywords: Axial Loading, Composite, Hollow CylindricalFiber, Stress Distribution.

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Authors: T. H. Young, Y. J. Tsai

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A method for determining the stress distribution of a rectangular plate subjected to two pairs of arbitrarily distributed in-plane edge shear loads is proposed, and the free vibration and buckling of such a rectangular plate are investigated in this work.  The method utilizes two stress functions to synthesize the stress-resultant field of the plate with each of the stress functions satisfying the biharmonic compatibility equation. The sum of stress-resultant fields due to these two stress functions satisfies the boundary conditions at the edges of the plate, from which these two stress functions are determined. Then, the free vibration and buckling of the rectangular plate are investigated by the Galerkin method. Numerical results obtained by this work are compared with those appeared in the literature, and good agreements are observed.

Keywords: Stress analysis, free vibration, plate buckling, nonuniform in-plane edge shear.

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Authors: Nao-Aki Noda, Yu Zhang, Ken-Tarou Takaishi, Hiroyuki Shibahara

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In this paper the strength of adhesive joint under tension and bending is discussed on the basis of intensity of singular stress by the application of FEM. A useful method is presented with focusing on the stress at the edge of interface between the adhesive and adherent obtained by FEM. After analyzing the adhesive joint strength with all material combinations, it is found that to improve the interface strength, thin adhesive layers are desirable because the intensity of singular stress decreases with decreasing the thickness.

Keywords: Adhesive, Adherent, Intensity of singular stress, Bonded strip

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Authors: A. Kurşun, M. Tunay Çetin, E. Çetin, H. Aykul

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In this investigation an elastic stress analysis is carried out a woven steel fiber reinforced thermoplastic cantilever beam loaded uniformly at the upper surface. The composite beam material consists of low density polyethylene as a thermoplastic (LDFE, f.2.12) and woven steel fibers. Granules of the polyethylene are put into the moulds and they are heated up to 160°C by using electrical resistance. Subsequently, the material is held for 5min under 2.5 MPa at this temperature. The temperature is decreased to 30°C under 15 MPa pressure in 3min. Closed form solution is found satisfying both the governing differential equation and boundary conditions. We investigated orientation angle effect on stress distribution of composite cantilever beams. The results show that orientation angle play an important role in determining the responses of a woven steel fiber reinforced thermoplastic cantilever beams and an optimal design of these structures.

Keywords: Cantilever beam, elastic stress analysis, orientation angle, thermoplastic.

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Authors: Mirigul Altan, Huseyin Yildirim

Abstract:

Plastics occupy wide place in the applications of automotive, electronics and house goods. Especially reinforced plastics become popular because of their high strength besides their advantages of low weight and easy manufacturability. In this study, mechanical and morphological properties of polypropylene (PP) and high density polyethylene (HDPE) matrix composites reinforced with surface modified nano titan dioxide (TiO2) particles were investigated. Surface modification was made by coating the nano powders with maleic anhydride grafted styrene ethylene butylene styrene (SEBS-g-MA) and silane, respectively. After surface modification, PP/TiO2 and HDPE/TiO2 composites were obtained by using twin screw extruder at titan dioxide loading of 1 wt.%, 3 wt.% and 5 wt.%. Effects of surface modification were determined by thermal and morphological analysis. SEBS-g-MA provided bridging effect between TiO2 particles and polymer matrix while silane was effective as a dispersant. Depending on that, homogenous structures without agglomeration were obtained. Mechanical tests were performed on the injection moldings of the composites for obtaining the impact strength, tensile strength, stress at break, elongation and elastic modulus. Reinforced HDPE and PP moldings gave higher tensile strength and elastic modulus due to the rigid structure of TiO2. Slight increment was seen in stress at break. Elongation and impact strength decreased due to the stiffness of the nano titan dioxide.

Keywords: High density polyethylene, mechanical properties, nano TiO2, polypropylene.

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Authors: T. K. V. Iyengar, Punnamchandar Bitla

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The paper deals with the pulsating flow of an incompressible couple stress fluid between permeable beds. The couple stress fluid is injected into the channel from the lower permeable bed with a certain velocity and is sucked into the upper permeable bed with the same velocity. The flow between the permeable beds is assumed to be governed by couple stress fluid flow equations of V. K. Stokes and that in the permeable regions by Darcy-s law. The equations are solved analytically and the expressions for velocity and volume flux are obtained. The effects of the material parameters are studied numerically and the results are presented through graphs.

Keywords: Pulsating flow, couple stress fluid, permeable beds, mass flux, shear stress.

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Authors: Jocelyn Sackey, Priscilla Boahemaa, Mohammed A. Sanda

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This study explored the relationship between occupational stress and the perceived effectiveness of men and women managers in Ghanaian organizations. The exploration is underlined by attempt to understand the degree to which male and female managers in Ghanaian organizations experience occupational stress at the workplace. The purpose is to examine the sources and extents of occupational stress experienced by male and female managers in Ghana. Data was collected using questionnaires and analyzed using both descriptive statistics and correlation analysis. The results showed that female managers in Ghana are more likely to report of more stress experiences in the workplace than their male counterparts. The female managers are more likely to perceive role conflict and alienation as job stressors while the male managers perceived blocked career as a major source of workplace stress. It is concluded that despite the female managers experiencing enormous level of occupational stress, there was no significant differences between their managerial effectiveness and that of the male.

Keywords: Gender, job stress, managerial effectiveness, organizational environment

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Authors: Md Abdullah Al Faruque, Ram Balachandar

Abstract:

An experimental study with four different types of bed conditions was carried out to understand the effect of roughness in open channel flow at two different Reynolds numbers. The bed conditions include a smooth surface and three different roughness conditions, which were generated using sand grains with a median diameter of 2.46 mm. The three rough conditions include a surface with distributed roughness, a surface with continuously distributed roughness and a sand bed with a permeable interface. A commercial two-component fibre-optic LDA system was used to conduct the velocity measurements. The variables of interest include the mean velocity, turbulence intensity, correlation between the streamwise and the wall normal turbulence, Reynolds shear stress and velocity triple products. Quadrant decomposition was used to extract the magnitude of the Reynolds shear stress of the turbulent bursting events. The effect of roughness was evident throughout the flow depth. The results show that distributed roughness has the greatest roughness effect followed by the sand bed and the continuous roughness. Compared to the smooth bed, the streamwise turbulence intensity reduces but the vertical turbulence intensity increases at a location very close to the bed due to the introduction of roughness. Although the same sand grain is used to create the three different rough bed conditions, the difference in the turbulence intensity is an indication that the specific geometry of the roughness has an influence on turbulence structure.

Keywords: Open channel flow, smooth bed, rough bed, Reynolds number, turbulence.

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Authors: Didik Nurhadiyanto , Moch Agus Choiron , Ken Kaminishi , Shigeyuki Haruyama

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At the previous study of new metal gasket, contact width and contact stress were important design parameter for optimizing metal gasket performance. However, the range of contact stress had not been investigated thoroughly. In this study, we conducted a gasket design optimization based on an elastic and plastic contact stress analysis considering forming effect using FEM. The gasket model was simulated by using two simulation stages which is forming and tightening simulation. The optimum design based on an elastic and plastic contact stress was founded. Final evaluation was determined by helium leak quantity to check leakage performance of both type of gaskets. The helium leak test shows that a gasket based on the plastic contact stress design better than based on elastic stress design.

Keywords: Contact stress, metal gasket, plastic, elastic

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Authors: Ehsan Shahrabian, Ali Soleymani

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Several yield-based stress indices have been developed that may be more applicable to work on drought tolerance. In this study, we investigate possibility of using stress susceptibility index (SSI), tolerance index (TOL), yield stability index (YSI), yield index (YI), stress tolerance index (STI), geometric mean productivity (GMP), harmonic mean (HARM), mean productivity (MP) to identify genotypic performance of some maize cultivars under normal and stressed condition. The results indicate that it was possible to identify superior genotypes for drought tolerance based on their stress indices and generally SSI indices which showed the lowest negative correlation with dry matter yield can be used as the best index for maize breeding programs to introduce drought tolerant hybrids. It was found that SC 647 showed the best behavior under drought stress condition based on TOL and SSI. A higher STI, GMP, and HARM values were attained for ko_6. It can be suggested that ko₆ should be cultivated in moderate stressful environment of Iran.

Keywords: Index, productivity, stress, susceptibility tolerance, yield.

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Authors: Kaman M. O., Celik N.

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In this study, stress distributions on dental implants made of functionally graded biomaterials (FGBM) are investigated numerically. The implant body is considered to be subjected to axial compression loads. Numerical problem is assumed to be 2D, and ANSYS commercial software is used for the analysis. The cross section of the implant thread varies as varying the height (H) and the width (t) of the thread. According to thread dimensions of implant and material properties of FGBM, equivalent stress distribution on the implant is determined and presented with contour plots along with the maximum equivalent stress values. As a result, with increasing material gradient parameter (n), the equivalent stress decreases, but the minimum stress distribution increases. Maximum stress values decrease with decreasing implant radius (r). Maximum von Mises stresses increases with decreasing H when t is constant. On the other hand, the stress values are not affected by variation of t in the case of H = constant.

Keywords: Functionally graded biomaterials, dental implant finite element method.

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Authors: Soheil Karimi, Abbas Yadollahi, Kazem Arzani, Ali Imani

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This study was conducted to evaluate the response of almond genotypes to osmotic stress in vitro in order to screen drought tolerance. Explants subjected to polyethyleneglycol osmotic stress (0, 3.5, and 7.0% WV) on the MS medium. Concentrations of photosynthesis pigments, anthocyanins, and carothenoids were significantly reduced under osmotic stress. Under osmotic stress, leaf water content, cellular membrane stability and pigments concentrations were significantly higher in the leaves of drought tolerant genotypes. The results revealed that carotenoids and anthocyanins may act as photoprotectant compounds in almond leaves and involved in drought tolerance system of the plant.

Keywords: Almond, Anthocianins, Carotenoids, in vitro; Leaf Osmotic Stress, Leaf Pigments, Polyethylene Glycol.

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Authors: Parveen K. Saini, Tarun Agarwal

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An investigation into the effect of countersunk depth, plate thickness, countersunk angle and plate width on the stress concentration around countersunk hole is carried out with the help of finite element analysis. The variation of stress concentration with respect to these parameters is studied for three types of loading viz. uniformly distributed load, uniformly varying load and functionally distributed load. The results of the finite element analysis are interpreted and some conclusions are drawn. The distribution of stress concentration around countersunk hole in isotropic plates simply supported at all the edges is found similar and is independent of loading. The maximum stress concentration also occurs at a particular point irrespective of the loading conditions.

Keywords: Stress Concentration Factor, Countersunk hole, Finite element, ANSYS.

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Authors: Anuchit Uchaipichat

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A comprehensive program of laboratory testing on a compacted kaolin in a modified triaxial cell was perform to investigate the influence of hydraulic hysteresis on effective stress in unsaturated soils. The test data are presented on a range of constant suction shear tests along wetting and drying paths. The values of effective stress parameter χ at different matric suction were determined using the test results. The effect of hydraulic hysteresis phenomenon on the effective stress was observed. The values of effective stress parameter χ obtained from the experiments were compared with those obtained from the expressions proposed in literature.

Keywords: Unsaturated soils, Hydraulic hysteresis, Effectivestress

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Authors: Aqsa Akbar, Waheed Akhter

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Job stress is one of the most important concepts for the today-s corporate as well as institutional world. The current study is conducted to identify the causes of faculty stress at Higher Education in Pakistan. For the purpose, Public & Private Business Schools of Punjab is selected as representative of Pakistan. A sample of 300 faculty members (214 males, 86 females) responded to the survey. Regression analysis shows that the Workload, Student Related issues and Role Conflicts are the major sources contributing significantly towards producing stress. The study also revealed that Private sector faculty members experienced more stress as compared to faculty in Public sector Business Schools. Moreover, females, younger ages, lower designation & low qualification faculty members experience more stress as compared to males, older ages, higher designation and high qualification. The study yield many significant results for the policy makers of Business Institutions.

Keywords: Faculty Stress, Higher Education, Stress Coping Strategies, Work Load

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Authors: A.V. Hoseini, A. Bidi, M. H. Pol, M.Jalali azizpour

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In this paper stress and strain for two rotating thin wall cylinder fitted together with initial interference and overlap are computed. Also stress value for variation of initial interference is calculated. At first problem is considered without rotation and next angular velocity increased from 0 to 50000 rev/min and stress in each stage is calculated. The important point is that when stress become very small in magnitude the angular velocity is critical and two cylinders will separate. The critical speed i.e. speed of separation is calculated in each step.

Keywords: Thin walled cylinder, high angular velocity, twofitted thin walled

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Authors: Tejeet Singh, Ishavneet Singh

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The present study focused on carrying out the creep analysis in an isotropic thick-walled composite cylindrical pressure vessel composed of aluminum matrix reinforced with silicon-carbide in particulate form. The creep behavior of the composite material has been described by the threshold stress based creep law. The values of stress exponent appearing in the creep law were selected as 3, 5 and 8. The constitutive equations were developed using well known von-Mises yield criteria. Models were developed to find out the distributions of creep stress and strain rate in thick-walled composite cylindrical pressure vessels under internal pressure. In order to obtain the stress distributions in the cylinder, the equilibrium equation of the continuum mechanics and the constitutive equations are solved together. It was observed that the radial stress, tangential stress and axial stress increases along with the radial distance. The cross-over was also obtained almost at the middle region of cylindrical vessel for tangential and axial stress for different values of stress exponent. The strain rates were also decreasing in nature along the entire radius.

Keywords: Steady state creep, composite, cylinder, pressure.

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