Dimensionless stress intensity factors were determined for single-edge-crack solid and hollow round bars loaded in tension. These factors were calculated from experimental compliance (inverse slope of load-displacement curve) measurements made over a range of dimensionless crack depths (lengths) from 0.05 to 0.65. The tests were made with 76-mm (3-in.) diameter solid and hollow round bars notched on one side and loaded in axial tension. The hollow bar had an inner to outer diameter ratio of 0.33. A comparison was made with data in the literature for rectangular bars; for a crack depth to diameter ratio of 0.0001 the dimensionless stress intensity factor for a solid round bar is 0.55 compared with 2.0 for a rectangular bar.

This paper surveys the current state of knowledge concerning multiaxial fatigue. Developments are presented in chronological order and are discussed so as to supplement existing reviews in this field. Emphasis is placed primarily on the criteria or methods of evaluation of fatigue strength under general multiaxial loading at room temperature. The survey indicates that the early development of the criteria was based on extensions of static yield theories to fatigue under combined stresses. These are stress-based criteria limited primarily to high-cycle fatigue. Most of the later criteria are strain-based. These criteria fall into two broad groups: the equivalent stress or strain type and the critical plane type. Most of these criteria commonly lack considerations of the cyclic stress-strain response. Their application to nonproportional loading suffers from difficulties in implementation or from inconsistencies with results of experiments. Recent approaches fall in the category of continuous damage evaluation methods. At present, these appear to be abstract or difficult to implement. All the above criteria are critically examined and compared. With this background, a new plastic work approach, proposed by the author, is discussed briefly.

Fatigue crack growth at intermediate rates was measured in compact tension specimens of the microstructurally contrasting alloys Ti-6Al-4V (Imperial Metal Industries, Ltd. [IMI] titanium 318) and Ti-6Al-5Zr-0.5Mo-0.25Si (IMI titanium 685). Sinusoidal loading was used with a ratio of minimum load to maximum load R of 0.1. The incidence of crack closure was examined during fatigue with both direct current potential drop and crack-opening-displacement (COD) methods; COD was found to be more reliable for closure measurement than potential drop. In contract to the fine-grained IMI 318, the coarse-structured IMI 685 showed substantial load transfer across the crack faces during fatigue and this was attributed to mismatch of the fracture faces. It was shown that the large differences in crack growth rate between the two alloys could be substantially accounted for by an effective stress intensity factor range concept. Marked reductions in growth rate produced by variable amplitude loading of the IMI 318 could not be explained in terms of crack closure.

Standard Charpy calibration specimens designed for verification of pendulum impact machines have been tested on a vertical drop tower impact machine. Two different test techniques (optical velocity measurement and integrated digital load-time response) for measuring the fracture energy of these specimens have produced equivalent sets of data which match the range of expected pendulum machine results. The more flexible vertical drop tower machine can therefore be used to measure Charpy impact energies with the same reliability as the conventional pendulum machines.

Laboratory testing was conducted to determine the effects of aggregate gradation and asphalt content on the stability and permeability of open-graded asphalt concrete. Test results indicate that permeability increases and stability decreases as the aggregate gradation becomes more open-graded, that is, includes less of the smaller sized particles. Also, permeability decreases as asphalt content increases whereas maximum stability occurs at an optimum asphalt content. Open-graded asphalt concrete was installed in the field for a porous pavement parking lot. The pavement has been serviceable for over two years, including exposure to winter conditions.