Degree Of Load Transfer Research Articles

Investigation of Polyurethane Bonding to Steel in Sandwich Panels

Sandwich panels made of thin and stiff skins, connected by a thick and soft core are widely used in load-bearing components mainly due to their high strength to weight ratio. To improve the reliability in using sandwich beams, it is necessary to understand their responses under external mechanical and environmental stimuli. This paper investigates the construction of steel-polyurethane-steel sandwich panels and their mechanical properties. Key properties of a sandwich structure are the adhesion between the skins and the sandwich material, and the load transfer from the outer skin to the inner skin. Lap shear specimens were selected to give an indication of the bond strength of the polyurethane to steel, whilst three point bend test specimens were selected to indicate the degree of load transfer between the skins and the bending resistance provided by the sandwich structure.

Effect of load transfer on the cracking behavior at a countersunk fastener hole

The objective of this paper is to describe the effect of fastener load transfer on the cracking behavior at countersunk fastener holes. Both experimental and computational studies are described and compared when possible. Fatigue failures at previously tested mechanical joint specimens were investigated and characterized. Qualitative three-dimensional finite element analyses revealed that the degree of load transfer through the fastener could influence the cracking behavior at the countersunk fastener hole. This finding from the qualitative analysis provides one good explanation to the experimental results of the mechanical joint specimens. The cracking location’s dependence on the load transfer can be attributed to the non-uniform bearing load distribution along the straight bore caused by the load transfer.

The thermo-mechanical behaviour of Cu-Cr in-situ composite

The mechanical response of in-situ copper-chromium composite was modelled using a deformation mechanism map approach. The stresses in each phase were predicted as a function of temperature and strain rate. From this the ratio of phase stresses, and hence the degree of load transfer, was obtained. The extent of load transfer and the predicted deformation modes of the two phases were then related to the expected failure mechanisms of the composite. Three modes of composite failure were predicted. Copper-chromium in-situ composites, and pure copper, were produced by a casting and swaging route. The mechanical properties were then characterised experimentally by tensile testing. Mechanical tests confirmed that the composite showed significantly higher strength than the unreinforced material. The observed failure modes of the composite were compared with the predictions.

EXTENDING THE FATIGUE LIFE OF MULTI‐LAYER METAL JOINTS

Abstract The influences of both hole cold expansion and interference‐fit fasteners for extending the fatigue life of multi‐layer aluminium alloy joint specimens under variable‐amplitude loading have been examined experimentally. Improvements in fatigue life were markedly dependent on the degree of load transfer in the specimen joint. Secondary bending in the joint also had a major influence, reducing the effectiveness of these life improvement techniques. Depending on the joint configuration, improvements in fatigue life ranged from nothing at all to a factor of about 40. Fretting appeared to be involved in the initiation of all cracks and where this occurred on faying surfaces only small, if any, improvements in fatigue life were obtained.