Formally Correct Solutions to Local Stress Equation can be Non-Physical

In general, all BCC transition metals have been observed to twin under appropriate conditions. At the present time various experimental reports of solid solution effects on BCC metals have been made. Indications are that solid solution effects are important in the formation of twins. The formation of twins in metals and alloys may be explained in terms of dislocation mechanisms. It has been suggested that twins are nucleated by the achievement of local stress-concentration of the order of 15 to 45 times the applied stress. Prietner and Leslie have found that twins in BCC metals are nucleated at intersections of (110) and (112) or (112) and (112) type of planes.In this paper, observations are reported of a transmission microscope study of the iron manganese series under conditions in which twins both were and were not formed. High strain rates produced by shock loading provided the appropriate deformation conditions. The workhardening mechanisms of one alloy (Fe - 7.37 wt% Mn) were studied in detail.

Download Full-text

The analysis of “Gels” in polymer films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153786 ◽

1989 ◽

Vol 47 ◽

pp. 362-363

Author(s):

G. M. Brown ◽

D. F. Brown ◽

J. H. Butler

Keyword(s):

Molecular Weight ◽

Film Industry ◽

Local Stress ◽

Melt Index ◽

Polyethylene Films ◽

Crosslinked Polymer ◽

Polymeric Gels ◽

Mineral Particles ◽

Polymeric Species ◽

Special Concern

The term “gel”, in the jargon of the plastics film industry, may refer to any inclusion that produces a visible artifact in a polymeric film. Although they can occur in any plastic product, gels are a principle concern in films where they detract from the cosmetic appearance of the product and may compromise its mechanical strength by acting as local stress concentrators. Many film gels are small spheres or ellipsoids less than one millimeter in diameter whereas other gels are fusiform-shaped and may reach several centimeters in length. The actual composition of gel inclusions may vary from miscellaneous inorganics (i.e. glass and mineral particles) and processing additives to heavily oxidized, charred or crosslinked polymer. The most commonly observed gels contain polymer differing from the bulk of the sample in its melt viscosity, density or molecular weight.Polymeric gels are a special concern in polyethylene films. Over the years and with the examination of a variety of these samples three predominant polymeric species have been observed: density gels which have different crystallinity than the film; melt-index gels in which the molecular weight is different than the film and crosslinked gels which are comprised of crosslinked polyethylene.

Download Full-text

Mathematical Model of the Effective Properties of a Fiber Reinforced Composite with a Linearly Graded Transition Zone

Tire Science and Technology ◽

10.2346/1.3519536 ◽

2010 ◽

Vol 38 (4) ◽

pp. 286-307

Author(s):

Carey F. Childers

Keyword(s):

Mathematical Model ◽

Transition Zone ◽

Effective Properties ◽

Local Stress ◽

Stress And Strain ◽

Fiber Reinforced ◽

Strain Fields ◽

Shear Moduli ◽

Fiber Reinforced Composite ◽

Reinforced Composite

Abstract Tires are fabricated using single ply fiber reinforced composite materials, which consist of a set of aligned stiff fibers of steel material embedded in a softer matrix of rubber material. The main goal is to develop a mathematical model to determine the local stress and strain fields for this isotropic fiber and matrix separated by a linearly graded transition zone. This model will then yield expressions for the internal stress and strain fields surrounding a single fiber. The fields will be obtained when radial, axial, and shear loads are applied. The composite is then homogenized to determine its effective mechanical properties—elastic moduli, Poisson ratios, and shear moduli. The model allows for analysis of how composites interact in order to design composites which gain full advantage of their properties.

Download Full-text

Finite Element Modeling for Steel Cord Analysis in Radial Tires

Tire Science and Technology ◽

10.2346/tire.13.410104 ◽

2013 ◽

Vol 41 (1) ◽

pp. 60-79 ◽

Cited By ~ 1

Author(s):

Wei Yintao ◽

Luo Yiwen ◽

Miao Yiming ◽

Chai Delong ◽

Feng Xijin

Keyword(s):

Finite Element ◽

High Efficiency ◽

Force Measurement ◽

Three Dimensional ◽

Local Stress ◽

Tension Force ◽

Center Line ◽

Element Analysis ◽

Design Variables ◽

Steel Cord

ABSTRACT: This article focuses on steel cord deformation and force investigation within heavy-duty radial tires. Typical bending deformation and tension force distributions of steel reinforcement within a truck bus radial (TBR) tire have been obtained, and they provide useful input for the local scale modeling of the steel cord. The three-dimensional carpet plots of the cord force distribution within a TBR tire are presented. The carcass-bending curvature is derived from the deformation of the carcass center line. A high-efficiency modeling approach for layered multistrand cord structures has been developed that uses cord design variables such as lay angle, lay length, and radius of the strand center line as input. Several types of steel cord have been modeled using the developed method as an example. The pure tension for two cords and the combined tension bending under various loading conditions relevant to tire deformation have been simulated by a finite element analysis (FEA). Good agreement has been found between experimental and FEA-determined tension force-displacement curves, and the characteristic structural and plastic deformation phases have been revealed by the FE simulation. Furthermore, some interesting local stress and deformation patterns under combined tension and bending are found that have not been previously reported. In addition, an experimental cord force measurement approach is included in this article.

Download Full-text

Measuring Earwax Cortisol Concentration Using a Non-Stressful Method (Preprint)

10.2196/preprints.19383 ◽

2020 ◽

Author(s):

Andrés Herane-Vives

Keyword(s):

Cortisol Level ◽

Local Stress ◽

Extraction Methods ◽

Cortisol Concentration ◽

The Novel ◽

Sampling Device ◽

Related Factors ◽

Novel Device ◽

Cortisol Levels ◽

The Right

BACKGROUND “Short-term” samples are not the most appropriate for reflecting Chronic Cortisol Concentration (CCC). Although hair is used for reflecting the systemic cortisol level over “long-term”, its use appears clinically problematic. Local stress and non-stress related factors may release a circumscribed cortisol secretion that is accumulated in hair. Non-stressful earwax extraction methods may provide a more accurate specimen to measure CCC. OBJECTIVE Correlate cortisol levels using hair, serum and earwax samples METHODS Earwax from both ears of 37 controls were extracted using a clinical procedure commonly associated with local pain. One month later, earwax from the left ear side was extracted using the same procedure, and earwax from the right ear side was comfortably extracted, using an earwax self-sampling device. Participants also provided one centimetre of hair that represented the retrospective month of cortisol output, and one serum sample that reflected the effect of systemic stressors on cortisol levels. Earwax (ECC), Hair (HCC) and Serum (SCC) Cortisol Concentration were correlated and compared. Confounders´ effect on cortisol levels were studied. RESULTS Serum showed the largest and hair the lowest cortisol concentration (p<0.01). Left-ECC was larger than Right-ECC (p=0.03). Right-ECC was the only sample unaffected by confounders (all p>0.05). Right-ECC and HCC showed the only significant association (r=0.39; p=0.03). CONCLUSIONS The self-sampling device did not represent a local stressor for the ceruminous glands. It provided the cortisol level with the least likely to be affected by confounding factors over the previous month. ECC using the novel device may constitute another accurate, but more suitable and affordable specimen for measuring CCC.

Download Full-text

Reliability Simulation and Forecast Based on Virtual Prototype for the Running System of Complicated Equipments

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.543-547.195 ◽

2014 ◽

Vol 543-547 ◽

pp. 195-198

Author(s):

Li Jun Cao ◽

Hui Bin Hu ◽

Gui Bo Yu ◽

Shu Hai Wang

Keyword(s):

Probability Density ◽

Local Stress ◽

Virtual Prototype ◽

Probability Density Distribution ◽

Stress And Strain ◽

Load Spectrum ◽

Density Distribution Function ◽

Running System ◽

Maintenance Cycle ◽

Damage Theory

The running system is the key part to finish training or battle tasks of complicated equipments. But formidable working conditions influence the measurement of load spectrums and it is difficult to analyze and forecast the reliability of running system. Actual vehicle experiments and virtual prototype are firstly combined to obtain complete load spectrum of running system. According to the materials S-N curve, stress and strain spectrums can be computed. Nominal stress method and local stress and strain method are combined with probability density accumulation damage theory to compute the probability density distribution function. Then, the reliability of running system can be forecasted, which provide adequate reference for the maintenance cycle confirmation and mission reliability prediction.

Download Full-text

Preliminary Evaluation of the Influence of Surface and Tooth Root Damage on the Stress and Strain State of a Planetary Gearbox: An Innovative Hybrid Numerical–Analytical Approach for Further Development of Structural Health Monitoring Models

Computation ◽

10.3390/computation9030038 ◽

2021 ◽

Vol 9 (3) ◽

pp. 38

Author(s):

Franco Concli ◽

Athanasios Kolios

Keyword(s):

Structural Health Monitoring ◽

Health Monitoring ◽

Analytical Approach ◽

Surface Defects ◽

Local Stress ◽

Computational Effort ◽

Preliminary Evaluation ◽

Tooth Root ◽

Planetary Gearbox ◽

Structural Health

Wind turbine gearboxes are known to be among the weakest components in the system and the possibility to study and understand the behavior of geared transmissions when subject to several types of faults might be useful to plan maintenance and eventually reduce the costs by preventing further damage. The aim of this work is to develop a high-fidelity numerical model of a single-stage planetary gearbox selected as representative and to evaluate its behavior in the presence of surface fatigue and tooth-root bending damage, i.e., pits and cracks. The planetary gearbox is almost entirely modelled, including shafts, gears as well as bearings with all the rolling elements. Stresses and strains in the most critical areas are analyzed to better evaluate if the presence of such damage can be somehow detected using strain gauges and where to place them to maximize the sensitivity of the measures to the damage. Several simulations with different levels, types and positions of the damage were performed to better understand the mutual relations between the damaged and the stress state. The ability to introduce the effect of the damage in the model of a gearbox represents the first indispensable step of a Structural Health Monitoring (SHM) strategy. The numerical activity was performed taking advantage of an innovative hybrid numerical–analytical approach that ensures a significant reduction of the computational effort. The developed model shows good sensitivity to the presence, type and position of the defects. For the studied configuration, the numerical results show clearly show a relation between the averaged rim stress and the presence of root cracks. Moreover, the presence of surface defects seems to produce local stress peaks (when the defects pass through the contact) in the instantaneous rim stress.

Download Full-text