A stress concentration factor kt is a dimensionless factor that is used to quantify how concentrated the stress is in a material. In this paper an improved model is proposed which takes the tube radial deformations into account. L if notch sensitivity data is not available, it is conservative to use kt in fatigue calculations. A measure of stress concentration is the stress concentration factor.
Stress concentration factors for the fatigue design of. Stress concentration factor k t was assumed as the characteristic value determined during the calculations. Substantially revised and completely updated, this book presents stress concentration factors both graphically and with formulas. It is thus defined as a ratio of the highest stress in the element to the reference stress. It is defined as the ratio of the highest stress in the element to the reference stress. Numerical analysis of stress concentration factors in order to verify the accuracy of the alfak soft ware, analysis of stress concentration factor was performed using numerical analysis in catia.
Pdf evaluation of stress concentration factor using ansys. 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. 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. Comparison between the concentration factor data obtained through the simulation and the theoretical found in the bibliography. Stress concentration caused by sudden change in form. It can be noticed that the bigest increase of stress concentration factor occurs at rt pdf free download as pdf file. Mechanical engineers reference book twelfth edition, 1994. As a base for estimating the effect of other parameters we estimate the fatigue notch factor k f for. Approximate stressconcentration factor kt for bending of a round bar or tube with a transverse round hole source. A formula is developed to predict the peak stress concentration factor scf for analysis andor design in conjunction with the asme boiler and pressure vessel code, section viii, divisions 1 and 2. Charts of theoretical stressconcentration factors k. Stress concentrations locally high stresses can arise due to abrupt changes in section properties hole, corner contact stresses bearing, gear, etc material discontinuities initial stresses due to manufacturing process. Determination of stress concentration factor by different.
Stress concentration factor important parameter for the safety. The stress concentration factor for a circular hole in an infinite plate. Reference stress is the total stress within an element under the same loading conditions without the stress concentrators. 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. If the effective stress concentration factor for surface roughness is obtained from eq. 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. Stress concentration factor theories of elastic failure strength of materials duration. The formula is rationally derived to include all of the parameters that are required to define the various penetration configurations used in. Stress concentration factor an overview sciencedirect. The stress concentration factor for isotropic materials, such as metals and plastics, is determined using the procedure described in 18. As a base for estimating the effect of other parameters we estimate the fatigue notch factor k f for zero mean stress and long life 106108 cycles. Stress concentration 20022014 darrell socie, all rights reserved 1 of 63 outline 1. Stress concentration and stress concentration factors.
The stress concentration factor is defined as the ratio of highest stress in the body to the reference stress. The frozen stress method of threedimensional stress analysis was used to determine the magnitudes and locations of points of stress concentration in plastic. Stress concentration factor kt, is a dimensionless factor which is used to quantify how concentrated the stress is in a material. Peterson, stressconcentration factors, wiley, new york, 1974, pp. A stressconcentration factor is then applied to the data of box 3 and combined with the palmgrenminer damage rule and a material sn curve to yield the annual cumulative damage, d, and fatigue life of 1d years. Petersons stress concentration factors wiley online books. The apparent geometric origin of fatigue fractures in oversize shank bolts is considered in this report. Imagine that the flow of force is like the flow of water.
Figure 1 distribution of stress for any cross section for an object in pure tensioncompression. Stress concentration factors are given for various common discontinuities. Determination of stress concentration factors on flat. L convenient to think of kf as a stress concentration factor reduced from kt because of lessened sensitivity to notches. The stress concentration factor calculators presented in this section calculate. Fatigue stress concentration factors lkf is normally used in fatigue calculations but is sometimes used with static stresses. Notch sensitivity and fatigue notch factor, k f the fatigue notch factor,k f,is not necessarily equal to the elastic stress concentration factor. Stress concentration introjxjction factorshavebeen universallycomputedon the basis of the theoryof elasticity. Stress concentration factor defined in this fashion is called k n. Table a16 approximate stressconcentration factor kt for bending of a round bar or tube with a. The effects of stress raisers are usually given in terms of a stress concentration factor, k, which is the factor by which the stress at the considered discontinuity is raised over the nominal stress in the area of the discontinuity.
Stress concentration article about stress concentration. Experimentally, the stress concentration factor can be found by using universal testing machine, instron test machine, polar scope system, etc. What is stress concentration definition, causes, effects. These may be reduced by using key seats made with bull end mills. When evaluating the effect of notches on the fatigue resistance of a part, we use the fatigue stress concentration factor. Stress concentration factor defined this way is denoted as k g. Notch is a general term meaning any or all of the above. The situation is somewhat different with anisotropic materials, such as fibrepolymer composites, because the stress concentration factor is dependent on the elastic modulus in different directions. Boltnut interaction between the bolt and both a standard nut and a special nut are investigated. Stress concentration near a circular hole stresses at the edge of the hole at x a. Pdf numerical analysis of stress concentration factors. Stress concentrations in boltthread roots springerlink. There are different stress concentration factors for bending and torsional loads.
Corrosionpedia what is a stress concentration factor kt. Although the most preferred method is by using the utm. 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. We obtained stress concentration factor from this method as 2. For a notch sensitivity ratio of 1, the full stress concentration factor is used. Estimating the fatigue stress concentration factor of. 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. In the fatigue analysis the peak stress at the critical region of a structure is computed as a product of nominal stress and the stress concentration factor kt. 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.
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