Experimental Analysis of Dynamic Effects in Different Crack Arrest Test Specimens

Abstract

For different crack arrest test specimens, the influence of dynamic effects on the crack arrest process is investigated. Utilizing the shadow optical method of caustics, actual dynamic stress-intensity factors directly before, at, and after arrest were measured. In the first part of the investigation, specimens made from the model material Araldite B were analyzed. It was found that the dynamic effects, that is, the difference between statically and dynamically determined crack arrest stress-intensity factors, are largest for longitudinal wedge-loaded rectangular double cantilever beam specimens, considerably smaller for machine-loaded tapered double cantilever beam specimens, and smallest for transverse wedge-loaded compact specimens. In the second part of the paper, the behavior of arresting cracks in high-strength steel specimens was investigated. The overall dynamic effects on the crack arrest process were found to be similar to those in Araldite B, but in steel the oscillation of the dynamic stress-intensity factor after arrest shows higher-frequency disturbances and is damped out only after much longer times.

Finite element simulation of fast fracture in steel DCB specimen

“…1 corresponds to that reported in Ref. [4], and a plane-stress condition is invoked in the present two-dimensional analysis.…”

“…(4), that the variation of a.. and u. must be known in the finite 1) 3 1 1 1 element mesh at time t 2 . However, a j and u., and U. were solved for, in the finite element mesh at t .…”

“…In Ref. [4], the crack initiation stress intensity factor for a blunt -1.5 notch, KIQ' was quoted as 224 MNm . Prior to the dynamic analysis, a static analysis of the specimen is performed to obtain the critical load-point deflection which produces the initiation stress intensity factor K .=224 MNm -1 .…”

“…In the experiments, stress intensity factors for fast running cracks were measured by means of the shadow optical method of caustics. This method was later applied for a nontransparent specimen [4]. Thestress intensity factors were measured by the caustics reflected from the mirrored surface of a high strength steel specimen.…”

“…[4], insufficient data for crack propagation history which are required in the present generation phase study [calculation of dynamic K-factors for a given crack-propagation history] have been measured in the experiment.…”