Fatigue in Compression

Reid, C.N.; Williams, Keith; Hermann, R.

doi:10.1111/j.1460-2695.1979.tb00382.x

Cited by 57 publications

(17 citation statements)

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“…This agrees with the assumption that T should be proportional to the plastic zone size. w in equation (2) is about 6 times greater than fin equation (4). But it has to be noticed that w in equation ( 2 ) is calculated for plane stress conditions.…”

Section: Crack Growth Behaviourmentioning

confidence: 85%

The Growth of Short Cracks Under Cyclic Compression

Pippan

1987

Fatigue Fract Eng Mat Struct

106

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The fatigue crack growth behaviour, the length of the arrested cracks and the shape of the crack front were investigated for cyclic compression. Specimens with deep sharp notches were used. The experiments were performed for different load amplitudes and load ratios under conditions of small scale yielding. The material used was ARMCO-iron. The growth rate and length of the arrested cracks were estimated and compared with the experimental results. The crack growth rate of very short cracks is determined by the stress intensity and is independent of the stress ratio. The length of the arrested cracks depends on the stress ratio and is bounded by the size of the cyclic and the monotonic plastic zones. NOMENCLATURE a = crack length ( = uo + I ) a, = notch depth K = stress intensity factor AK = stress intensity factor range K,,, = maximum stress intensity factor K,,, = minimum stress intensity factor K,, = closure stress intensity factor AK,,,, = effective threshold stress intensity factor range I =crack length measured from the notch root r= length of the arrested crack measured from the notch root dljdN = crack growth rate ( = dajdN) N = number of cycles R = ratio = Km,,/Km,, p = radius of the notch root ay = yield stress w = size of the monotonic plastic zone w, = size of the monotonic plastic zone after the first cycle. Aw = size of the cyclic piastic zone Atu, = size of the cyclic plastic zone after the first cycle

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Section: Crack Growth Behaviourmentioning

confidence: 85%

The Growth of Short Cracks Under Cyclic Compression

Pippan

1987

Fatigue Fract Eng Mat Struct

106

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“…A fatigue crack propagates under residual tensile stress governed greatly by plastic strains in the direction of free surface [4]. Large low-strength and plastic nonmetallics composed mostly of manganous sulphide contribute to plastic deformation of metals.…”

Section: Materials and Methods Of The Researchmentioning

confidence: 99%

Influence of nonmetallic inclusions on endurance of percussive machines

et al. 2011

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Based on the results of the industrial testing of downhole hammers with underreamers and on the analysis of the influence exerted by nonmetallic inclusions in steel on the steel fatigue endurance under the impact load, it has been shown that the stringer-type nonmetallics greatly aggravate the steel endurance both under compression and bending, although have no effect on the steel hardness and strength indexes.It is simple and efficient to make large diameter holes by reaming out a small diameter, pioneer hole using light weight drilling machines. For example, downhole hammer P150, designed at the Institute of Mining SB RAS (IM SB RAS) in the 1990s and batch-produced by the Serovsky Machine Plant (SMP), found application in mines of Russia and the former USSR countries in the capacity of an underreamer in driving holes for water passes or for backfilling. In 2008 EVRAZRUDA Co. started to use P150 hammer equipped with a 250-mm diameter underreamer in blasthole drilling, with the appropriate designer's service.Downhole hammers are placed in a confined environment and therefore are to be maximum small in size, also they must possess high impact effect to break hard rocks. The most stressed elements of hammers operate at their strength limit. Thus, the choice of material to manufacture hammer elements and the selection of the manufacturing technology are extremely important.Russian plants produce a variety of percussion machines for the mineral mining and construction industries at the moment. The materials such machines are made of should satisfy exclusive standards. For instance, percussive mechanisms, such as a striking bar or a bit, must have high hardness index and yield limit to retain geometrical dimensions. Percussive elements can be thermally strengthened depending on their size and impact energy: small component parts are usually subjected to heat hardening and then low-temperature tempering [1]; large-size elements exposed to high impact load undergo surface impregnation, namely, casehardening, and then low-temperature tempering.Being of equal performance, Russian machines are usually exhibit low reliability and operational life. High performance indexes of machines manufactured by leading foreign companies ensue from high durability steel. Recent testing of P150 hammers in Russia revealed noticeable reduction in life of the machines, which forced the Institute of Mining, SB RAS (IM SB RAS) to initiate a research into the quality of materials the hammers are made of, at the Novosibirsk State Technical University, Division of Materials Sciences in Engineering. The present article's authors have set a task to find out whys of the low reliability operation of Russian percussive machines and to develop the machine material selection guidelines. The research was carried out on the parts of the broken striking bars of different hammers.

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“…In the figure, the hatched area indicates the fatigue fracture surface and the arrow indicates the direction of crack growth. The crack length of a nonpropagating crack on the surface under a plane stress condition is longer than that at mid-thickness which is under a plane strain condition [7,8,121. As the maximum applied stress increases, the nonpropagating crack length becomes longer, and the crack front becomes parallel to the notch as seen in Fig.…”

Section: Crack Propagation Behaviourmentioning

confidence: 97%

Propagation and Closure of Short Fatigue Cracks at Notches Under Compressive Mean Stresses

Akiniwa

Tanaka

Taniguchi

1988

Fatigue Fract Eng Mat Struct

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Single-edge-notched specimens of a low-carbon steel were fatigued under cyclic in-plane bending with compressive mean stresses. The development of crack closure with crack growth was studied both experimentally and theoretically. The relation between the crack opening stress and the crack length was a function of the minimum (compressive) applied stress, irrespective of the maximum stress. The efl-ective stress intensity range was a unique parameter in correlating the crack growth rate, even if the crack wdS embedded in the compressive plastic zone. Under a constant minimum stress, the length of nonpropagating cracks became longer with increasing maximum applied stress. A theoretical model was proposed for predicting the crack opening stress on the basis of the compressive stress distribution at the minimum applied stress. The predicted value agreed fairly well with the experimental result. The model gave upper bounds of the crack growth rate and the length of nonpropagating Fatigue cracks within the plastic zone. NOMENCLATURE a =crack length including notch depth u', c'. n' =coefficients of the stress-strain relation c =crack length from the notch-tip c,. c,. cnp = mean, surface and non-propagating crack length dc/dN =crack propagation rate F. F , , F2 =geometrical correction factors for the stress intensity factor (SIF) K = SIF value due to applied stress K,,,, K,,, = SIF value due to minimum and maximum applied stress Kop = SIF value at crack opening K,, = SlF value due to residual stress Kr = stress concentration factor K*. K:," = true SIF value and SIF value calculated from the stress distribution at minimum applied nominal stress AKen, AK,,, =effective SIF range and its threshold value M = weight function R = ratio of minimum to maximum stress I = notch depth W = specimen width x =distance from the edge of specimen to load point p = notch-root radius 6 = von Mises equivalent stress u, = applied nominal stress amplitude u, = applied nominal mean stress = von Mises equivalent plastic strain urnax. u,,, = maximurn and minimum applied nominal stresses u:," =stress at minimum applied nominal stress u, = applied nominal stress uy = yield stress w, w * = plastic zone size at urnin and reversed plastic zone size at umrl 343 344 Y. AKINIWA er a1

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Fatigue in Compression

Cited by 57 publications

References 0 publications

The Growth of Short Cracks Under Cyclic Compression

The Growth of Short Cracks Under Cyclic Compression

Influence of nonmetallic inclusions on endurance of percussive machines

Propagation and Closure of Short Fatigue Cracks at Notches Under Compressive Mean Stresses

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