Concepts of stress and strain university of arizona. Small computer software for analysis of stress concentration factors was developed at faculty of mechanical engineering sarajevo. There are different stress concentration factors for bending and torsional loads. The chart below shows the curves of these factors and the dependency on the ratios of the critical dimensions. A finite element model is used to estimate stress concentration factors induced by plain dents on pipes under internal pressure. As i understand it, the quantities commonly referred to as stress concentration factors are in fact linearelastic static stress concentration factors. A measure of stress concentration is the stress concentration factor. Stress concentration factors for circular, reinforced penetrations in pressurized cylindrical shells a dissertation presented to the faculty of the school of engineering and applied science university of virginia in partial fulfillment of the requirements for the degree doctor of philosophy civil engineering by james w. Stress concentration factors for the fatigue design of. Boltnut interaction between the bolt and both a standard nut and a special nut are investigated. Fatigue stress concentration factors lkf is normally used in fatigue calculations but is sometimes used with static stresses. Ratio of these factors represents an accurate assessment of beneficial effects of the applied weld geometry modification method. Pdf stress concentration factors download ebook for free. Jun 02, 2015 a stress concentration is a place of the mesh where the stress raises above the applied nominal stress.
Stress concentrations in keyways and optimization of. Numerical analysis of stress concentration factors article pdf available in procedia engineering 100. Notch is a general term meaning any or all of the above. It is thus defined as a ratio of the highest stress in.
Download stress concentration factors ebook free in pdf and epub format. Stress concentrations in screw threads us army armament. Stress concentration factor an overview sciencedirect topics. Pdf numerical analysis of stress concentration factors. While it is often assumed that once the bolts are preloaded they are exempt from the fatigue phenomenon, the validity of such a simplified. The apparent geometric origin of fatigue fractures in oversize shank bolts is considered in this report. Jan 14, 2008 petersons stress concentration factors establishes and maintains a system of data classification for all of the applications of stress and strain analysis and expedites their synthesis into cad applications.
When q0, kf 1, that is, no fatigue stress concentration effect when q1, kfk, that is, fatigue stress concentration has equal value of geometric stress concentration factor. For stepped, circular shafts in torsion, k ts can be found from the following table. Neubers method enables the determination of static stresses in the nonlinear region arising from stressraisers, giving rise to an effective stress static concentration factor. I is a compilation of the work included in some 378 references. Petersons stress concentration factors, 4th edition wiley. Charts of theoretical stressconcentration factors k. A stress concentration often called stress raisers or stress risers is a location in an object where stress is concentrated. Interacting stress concentration factors and their effect on fatigue of metallic aerostructures by david warren whitley a dissertation presented to. Stress concentration factors for keyways cutting keyways create stress concentrations in shafts.
Stress concentration factor kt, is a dimensionless factor which is used to quantify how concentrated the stress is in a material. Developing process of the software was presented in previous papers of same authors, in this paper testing of the software was done using numerical analysis. Stress singularities, stress concentrations and mesh. The definitive guide to stress concentration, newly revised and updated. Stepped shafts in tension, bending, and torsion a plate with opposite ushaped notches in tension and bending elastic stress concentration factors depend only on geometry independent of material and mode of. Here, this fe model, previously developed and validated for. Stress concentrations occur when the load path is deviated by the. Most stressconcentration factors are determined by experimental or finite element techniques. Stress analysis and stress concentration factors are. The ratio of the true maximum stress to the stress calculated by the ordinary formulas of mechanics flexure formula, torsion formula, etc.
Petersons stress concentration factors, fourth edition includes a thorough introduction of the theory and methods for static and fatigue design, quantification of stress and strain, research on stress concentration factors for weld joints and composite materials, and a new introduction to the systematic stress analysis approach using finite. Geometric stress concentration factors can be used to estimate the stress amplification in the vicinity of a geometric discontinuity. The frozen stress method of threedimensional stress analysis was used to determine the magnitudes and locations of points of stress concentration in plastic. An object is stronger when force is evenly distributed over its area, so a reduction in area, e.
Bar in tension or simple compression with a transverse hole. In many simple geometries, the stress concentration factor is defined for a range of geometries. Stress concentration caused by sudden change in form a change in the geometric shape of a part gives rise to additional stress over and above the calculated stress, which is known as stress concentration. Stress concentration factors are used in the design of mechanical or engineering structures and machinery and have a tremendous impact on design of virtually every product or structure subject to environmental or userelated stress. Stress concentrations in keyways and optimization of keyway. It behaves in a similar fashion than stress singularities, but the stress will converge towards a finite value, not infinite, given that the mesh is sufficiently refined. Dd 2 conclusions for the bending case of bars and shafts with central enlarged sections of width d and length l the factor of stress concentration, k, is a function of lid in addition to the other two parameters rd and dd which govern in the.
Stress concentration and stress concentration factors grooves, fillets, holes, or other abrupt changes in cross section or any disruption of a smooth surface causes increased stresses around these areas. Pressure vessel technol october, 2015 surface texture, fatigue, and the reduction in stiffness of fiber reinforced plastics. Dec 26, 2007 petersons stress concentration factors establishes and maintains a system of data classification for all of the applications of stress and strain analysis and expedites their synthesis into cad applications. K is used to relate the maximum stress at nom t ts t t. Stress concentration factor important parameter for the safety. These two stress concentration factors are related to each other by a material property called sensitivity index or notch sensitivity q in the following way. Petersons stress concentration factors ebook, 2008. Scribd is the worlds largest social reading and publishing site.
Mar 20, 2018 stress factors diabetes risk factors stress mechanics stressstrain analysis stress biology factors of production concentration sir walter lawn posttraumatic stress disorder similar documents 12965732 petersons stress concentration factors. Assume, for example, that you have a rotating, round. Apr 06, 2017 the stress concentration factor is defined as the ratio of highest stress in the body to the reference stress. A number of different factors will have an influence on the needed fe analysis complexity and on the resulting maximum stresses found by the analyses. A stress concentration also called a stress raiser or a stress riser is a location in an object where the stress is significantly greater than the surrounding region.
Interacting stress concentration factors and their effect. Table a15 charts of theoretical stress concentration factors kt figure a151. Imagine that the flow of force is like the flow of water. Substantially revised and completely updated, this book presents stress concentration factors both graphically and with formulas. The stress concentration factor is defined as the ratio of highest stress in the body to the reference stress. Pdf petersons stress concentration factors loa carter. Compendiums of stress concentrations factors such as stress concentration factors, r. Stress concentration caused by sudden change in form. The value of the stress concentration factor is calculated by. Stress concentration of periodic collinear square holes in an infinite plate in tension j.
These may be reduced by using key seats made with bull end mills. Carvill, in mechanical engineers data handbook, 1993. It also employs computergenerated art in its portrayal of. Approximate stressconcentration factor kt for bending of a round bar or tube with a transverse round hole source. Approximate stressconcentration factors kts for a round bar or tube having a transverse round hole and loaded in torsion source.
L if notch sensitivity data is not available, it is conservative to use kt in fatigue calculations. Interacting stress concentration factors and their effect on fatigue of metallic aerostructures by david warren whitley a dissertation presented to the faculty of the. The keyway related stress is indeed fully three dimensional as also stated in peterson 18. Stress concentrations in boltthread roots springerlink. E stress concentration factors, john wiley, new york, 1974 2 neuber h theory of notch stresses, j. Rudolph earl peterson petersons stress concentration factors establishes and maintains a system of data classification for all of the applications of stress and strain analysis and expedites their synthesis into cad. Petersons stress concentration factors, 3rd edition wiley. Stress concentration article about stress concentration. T are not related to the properties of the material but rather depend on the type of stress concentrator, on its sharpness, absolute size, and size relative to the specimen. What is stress concentration definition, causes, effects. Discontinuities in the components that lead to local increase of stress is referred to as stress concentration. The combined effect of these misalignments induces a local secondary bending stress that augments the otherwise plain nominal stress in the pipe section, as the nominal bending moment and axial forces are transferred across the weld. Geometric stress concentration factors shigley, fig. We will use the standard mechanicsofmaterials stress formulas for the nominal stresses.
Stress concentration factors are given for various common discontinuities. The effective fatigue stress concentration factors of the machined surfaces were determined using the neuber rule 7 and arolaramulu model 8. Estimating the fatigue stress concentration factor of. Effects of stress raisers the stress raising effects of a circular groove in a tensile bar are shown in fig. Roarks formulas for stress and strain, 8th edition. Interacting stress concentration factors and their effect on. The stress concentration in a body happens because of sudden change in the geometry of the body due to cracks, sharp corners, holes, decrease in the cross section area. General values are also given for keyways, gear teeth, screw threads and welds. Stress concentration factor an overview sciencedirect. Stress concentration 20022014 darrell socie, all rights reserved 2 of 63 stress concentration factor. Charts of stress concentration factors are available in the literature. In addition, k is dependent only on ratios of geometric. L convenient to think of kf as a stress concentration factor reduced from kt because of lessened sensitivity to notches.
Stress concentrations occur when there are irregularities in the geometry or material of a structural component that cause an interruption to the flow of stress. The maximum stress occurs on the inside of the hole, slightly below the shaft surface. Peterson, stress concentration factors, wiley, new york, 1974, pp. Due to these irregularities, there is an increase in the intensity of stress in the body. Stress concentration and stress concentration factors. Petersons stress concentration factors establishes and maintains a system of data classification for all of the applications of stress and strain analysis and expedites their synthesis into cad applications. Approximate stressconcentration factors k ts for a round bar or tube having a transverse round hole and loaded in torsion source. The actual fatigue notch factors for the machined surfaces were estimated using experimental results from tensiontension fatigue tests. The ratio of smooth to net notched fatigue strengths, based on.