Papers by Keyword: Yield Stress

Abstract: The composite material is a combination of two or more materials with different physical and chemical properties. The composite has superior characteristics than those individual components. A hybrid composite is the one which contains at least three materials. When the matrix material is a metal, the composite is termed as metal matrix composites (MMC). The MMC is a composite material with two constituent parts, one being a metal. The other material may be another metal, ceramic or fiber. Among all the MMC’s, Aluminium is the most widely used matrix material due to its light weight, high strength and hardness. This paper deals with the fabrication and mechanical investigation of hybrid metal matrix composite Al - SiC. The fabrication is done by stir casting by adding the required quantities of additives into the stirred molten Aluminium. The results show significant effect of mechanical properties such as tensile strength, yield stress and flexural strength. The internal structure of the composite is observed using Scanning electron microscope (SEM) and found that are formation of pores in them.

Abstract: An experimental approach based on the conventional universal testing machine (UTM) was employed to perform low strain rate loading (0.001/s, 0.01/s and 0.1/s) in this research, to examine the reliance of natural filler contents towards HDPE/sawdust composites. By following to the low strain rate loading, static compression properties of HDPE/sawdust composites with varies filler contents of 5 wt% SD, 10 wt% SD, 15 wt% SD, 20 wt% SD and 30 wt: % SD were successfully studied. The results show that the yields stress, ultimate compression strength and the rigidity properties of HDPE/sawdust composites were sturdily affected by both filler contents and strain rate loadings. Moreover, for the post damage analysis, the results clearly show that different static loading employed to the specimens gives significant effects towards deformation behavior of HDPE/sawdust composites. The increasing of static loading employed caused the specimens to experience severe deformation.

Abstract: The paper presents the determination of the yield stress for copper, Cu_99.75, at standard ambient temperature, by means of upsetting of cilyndrical specimens, taking account the allowable degree of deformation of this material. The outcomes achieved can be used both plastic deformation processes and volumic deformation simulation of copper Cu_99.75.

Abstract: The truck that is used as running equipment for freight car support is a core structural part that supports the load of the car body and that greatly influences the safety of freights and vehicles, as well as their running performance. The running equipment is composed of truck frames, wheels and wheel axles, independent suspensions, and brakes. Among these components, the truck frame supporting the load of the vehicles and freights may be the most important one. This study was carried out to analyze the structure of truck frames and to determine whether they are safe when the maximum vertical load, breaking load, and front and rear loads are applied to them. This was done by subjecting the truck frames to stress tests and then measuring the stress on each of their parts. Before the load test, a structural-analysis program was used for the stress distribution analysis of the truck frame. To measure the stresses based on the results of the structural analysis, strain gages were attached to the surfaces of truck frames [1].

Abstract: Springback is a serious problem in the manufacturing industry due to errors that effects the appearance of the final product especially in the sheet forming process. This paper presents the review on past literature regarding factors that affects the amount of springback that occurs after the forming operation. This paper focus on 5 major elements that affects the value of springback including yield stress (σ_y), Young’s modulus (E), strain hardening exponent (n), Poisson’s Ratio (v) and thickness of the sheet (t). This 5 elements show that, increases in the value of (σ_y), (n), will increase the value of springback. The springback decreases with increasing of (t) and (E). While (v) has a small significant effect on springback. The effects of these factors can be used as a guide when considering further research on springback.

Abstract: According to von-Mises criterion, five kinds of independent slip systems are required for uniform deformation, so it is necessary to activate non-basal slip systems to show good ductility. However, it has not become clear the effect of Zn or Al for non-basal slip systems yet. To investigate deformation behavior of magnesium crystal by non-basal slip and alloying effect for the non-basal slip, pure magnesium and Mg-Al-Zn single crystals were stretched in the [110] direction. While {112}<23> second order pyramidal slip was activated at room temperature in pure magnesium, {101}<23> first order pyramidal slip became active slip at higher temperature. In Mg-Al-Zn alloy single crystal, {101} twin also activated by adding aluminum. These results indicate that active non-basal slip systems and twin in magnesium strongly depend on deformation temperature and alloying elements.

Abstract: The indentation test is one of the most common techniques for the mechanical characterization of materials. Different tests have been standardized, depending on punch geometry and indentation parameters, and different models have also been set up to predict indentation hardness and to estimate uni-axial mechanical properties for all the geometries (cone, wedge, pyramid, sphere, etc.). A flat-ended cylindrical indentation technique (FIMEC) has been developed by one of the present authors. FIMEC employs a cylindrical punch with diameter ranging from 3.0 to 0.5 mm and gives pressure-penetration curves from which yield stress and elasticity modulus can be determined. The specific characteristics of FIMEC are: 1-the high simplicity of the apparatus; 2-the possibility to get information about the local material properties on a scale large enough to include many grains (data represent bulk characteristics and are not influenced by those factors which dramatically affect micro-and nanoindentation tests); 3-the large versatility in industrial applications such as the control of welding quality, 4-the on-line monitoring of forging or extrusion processes etc.. This paper describes a new algorithm developed to calculate the yield stress from FIMEC curves. To assess the reliability of the method, it has been tested on several metals of known characteristics and the scattering of data with respect those from tensile tests resulted to be within ±7%.

Abstract: In this work it was studied the influence of recycled fine aggregate obtained from construction and demolition waste (CDW) on the rheological properties of Portland cement mortars. The CDW was initially separate in their main constituents (mortar, ceramic and concrete debris) at the laboratory and then grinded separately to the sand size in order to generate more homogeneous fine aggregates. The characterization of the natural and recycled sands was carried out through physical tests, X-ray diffraction, scanning electron microscopy (SEM), and image analysis (shape and texture description parameters). A conventional mortar and three mortars containing recycled sands were produced with a sand/cement ratio of 4 and consistency index of 255±5 mm. The consistency was kept constant by ranging the water-cement ratio from 0.58 to 1.14. The rheological study was performed using a rotating viscometer to obtain torque-rotation ratio and to calculate the yield stress and plastic viscosity. The results indicate that the presence of recycled aggregate causes a lowering of both yield stress and plastic viscosity with respect to the mortar containing natural aggregate.

Abstract: A magnetorheological fluid (MR), a suspension of micron-sized magnetic particles in a carrier fluid, has vast applications in the field of vibration dampers, seismic vibration dampers, shock absorbers, clutches, break system, vehicle suspensions, seat suspensions, Robotics, design of buildings and bridges etc. The biggest issue in MR fluid is the settling of particles under gravity. To overcome this, one of the approaches is to mix micron size particles in a magnetic fluid (MF) known as Nano-MRF. In the present paper, we report a technique to synthesis Nano-MRF suspension having high stability under gravitation as well as magnetic field. X-ray diffraction (XRD) and dynamic light scattering are used to characterize the solid/liquid system. Magnetic and Magnetorheological properties are studied and results indicate that: instead of decreasing stress with increasing temperature we have observed an increase until 40°C and thereafter, it decreases. This is explained based on, inter and intra particles/chain interaction as well as synergetic effect between small and large sized magnetic dispersion.

Abstract: Extra-heavy oil, polymer solution and some drilling fluids are typical non-Newtonian Herschel-Bulkley fluids, which behave as sheer-thinning with yield stress. In this paper, the Generalized Darcy's law for Herschel-Bulkley fluids flow in porous media was formulated, by the same way formulating the Generalized Darcy's Law for Bingham fluids. Then, the applications of the two type flow models were compared; Bingham type model was still widely applied due to its conciseness and relatively satisfied accuracy. In addition, the Generalized Darcys Law was revised to describe thixotropic non-Newtonian fluids conceptually.