Methods for crack opening load and crack tip shielding determination: a review

Abstract

In this paper a review of the literature on crack closure/opening load and crack tip shielding effects determination methods is presented. Commonly used ‘subjective’ (visual) and ‘non‐subjective’ approaches have been included. Procedures associated with the determination of an effective crack driving force for both Elber type and that of partial (or incremental) crack closure models have been covered. Comparison among different methods of analyses based on compliance and fatigue crack growth rate measurements is discussed together with their implications and difficulties in fatigue crack growth correlations.

The Effects of Elasto-Plastic Behavior at the Crack Tip on Fatigue Crack Propagation

“…At this time, the value P RCPG is in the high load region, but the values P RPG , P cl and P CF are in the low load region as shown in Figure 7(b), and the hysteresis loop tail is not formed as shown in Figure 7(a) (1). When the value P RPG , P cl and P CF rise gradually, the hysteresis loop tail enlarges gradually as shown in Figure 7(a) (2) and (3), and the fatigue crack begins to propagate. When each of the value P RCPG , P RPG , P cl , and P CF tends to constants, the ε'/dp 2 dε'/dp Change of compliance on loading process dε'/dp d 2 ε'/dp .…”

“…The crack propagation decelerates in the absence of a sufficient compressive plastic zone at the crack tip. (2) The route of fatigue crack propagation P RPG~Pmax and P RCPG~PCF plays an important effect in the crack opening/closure behavior, and is also a fundamental reason for causing the acceleration, deceleration and non-propagation phenomena under variable amplitude loading.…”

“…An effective stress intensity factor range ΔK eff (=K max -K op ) was defined by an opening stress intensity factor K op , and the opening load P op was often measured by ASTM 2% offset method or curve fitting method [2], as well as an unloading elastic compliance method brought by Kikukawa et al [3]. Otherwise, Nisitani and Chen [4] defined an effective stress intensity factor range ΔK eff (=K max -K cl ) by means of a closure stress intensity factor K cl , and the closure load P cl was determined based on the inflexion point on the unloading compliance.…”

A Piezoelectric Technique for Evaluation of Crack Closure

“…The crack closure phenomenon is an important variable in fatigue crack propagation and has been extensively studied through different methods [1,2]. The effect of crack closure is also important for ultrasonic measurement of crack depth [3], structural health monitoring techniques [4,5] and for methods of crack growth detection [6,7], as closed cracks can be erroneously evaluated.…”

Control of the breathing mechanism of a cracked rotor by using electro-magnetic actuator: numerical study

“…Then, the machine can work continuously for the longest possible time, before any intervention for repair. The crack closure phenomenon is an important variable in fatigue crack propagation and has been extensively studied through different methods [11,14,15]. Usually, in industrial applications the cracked shafts can be kept under operation for many years, if correctly monitored and operated before being replaced.…”