James W. Dally

Bio: James W. Dally is an academic researcher from IIT Research Institute. The author has contributed to research in topics: Elasticity (physics) & Fixture. The author has an hindex of 1, co-authored 2 publications receiving 1323 citations.

Experimental Stress Analysis

Abstract: Part 1: Elementary elasticity and fraction mechanics stress strain and the stress-strain relationships basic equations and plane-elasticity theory. Elementary fracture mechanics. Part 2: Strain-measurement methods and related instrumentation introduction to strain measurements electrical resistance strain gages strain gage circuits recording instruments strain analysis methods. Part 3: Optical methods of stress analysis basic optics moire methods theory of plasticity applied photoelasticity - two and three dimensional stress analysis optical methods for determining fracture parameters coating methods - photoelastic coatings and brittle coating statistical analysis of experimental data.

Rigidity and Strength of Composite Plates

Abstract: The objective of the experimental study described was to determine the rigidity, load carrying capability, and mode of failure for several composite (steel and concrete) circular plates. The models used for the study consisted essentially of an 18-3/4 in. diameter steel base plate overlaid with 3-1/2 in. of concrete. The concrete was constrained within a steel confining ring that was butt welded to the base plate. A special fixture was designed and built to apply loads to the models. In the fixture the models were simply-supported around the periphery of the steel base plate. A uniform lateral pressure sufficient to produce plastic deformation in the steel was applied to the concrete face. The results of the study indicate that concrete can be used with a confining ring and shear rings at the steel-concrete interface to increase the rigidity as well as the load carrying capability of the plates. The use of concrete as a load carrying component of the plate permits a reduction in the amount of steel for a given pressure level and results in a less expensive more easily fabricated design.

A carbon nanotube strain sensor for structural health monitoring

Abstract: A carbon nanotube polymer material was used to form a piezoresistive strain sensor for structural health monitoring applications. The polymer improves the interfacial bonding between the nanotubes. Previous single walled carbon nanotube buckypaper sensors produced distorted strain measurements because the van der Waals attraction force allowed axial slipping of the smooth surfaces of the nanotubes. The polymer sensor uses larger multi-walled carbon nanotubes which improve the strain transfer, repeatability and linearity of the sensor. An electrical model of the nanotube strain sensor was derived based on electrochemical impedance spectroscopy and strain testing. The model is useful for designing nanotube sensor systems. A biomimetic artificial neuron was developed by extending the length of the sensor. The neuron is a long continuous strain sensor that has a low cost, is simple to install and is lightweight. The neuron has a low bandwidth and adequate strain sensitivity. The neuron sensor is particularly useful for detecting large strains and cracking, and can reduce the number of channels of data acquisition needed for the health monitoring of large structures.

Review: Current international research into cellulosic fibres and composites

Abstract: The following paper summarises a number of international research projects being undertaken to understand the mechanical properties of natural cellulose fibres and composite materials. In particular the use of novel techniques, such as Raman spectroscopy, synchrotron x-ray and half-fringe photoelastic methods of measuring the physical and micromechanical properties of cellulose fibres is reported. Current single fibre testing procedures are also reviewed with emphasis on the end-use in papermaking. The techniques involved in chemically modifying fibres to improve interfacial adhesion in composites are also reviewed, and the use of novel fibre sources such as bacterial and animal cellulose. It is found that there is overlap in current international research into this area, and that there are complementary approaches and therefore further combining of these may make further progress possible. In particular a need to measure locally the adhesion properties and deformation processes of fibres in composites, with different chemical treatments, ought to be a focus of future research.

Introduction to carbon nanotube and nanofiber smart materials

Abstract: The potential use of carbon nanotubes and nanofibers as smart composite materials is discussed in this paper. An overview of the properties of carbon nanotube materials is presented, and then four applications under development are briefly discussed. The first application is electrochemical actuation in dry and aqueous environments. The second is a carbon nanotube polymer piezoresistive strain sensor developed for structural health monitoring. Third, nanotubes are used with an electrolyte for harvesting power from structural vibration. Fourth, a carbon nanotube bioelectronic sensor is discussed. Tying all this together, a vision is presented for using nanoscale smart materials to synthesize intelligent electronic structures with prescribed elastic and electrical properties for a wide range of new applications. Hurdles to be overcome to achieve this goal are also discussed.

Bone deformation recorded in vivo from strain gauges attached to the human tibial shaft.

Abstract: (1975). Bone Deformation Recorded in vivo from Strain Gauges Attached to the Human Tibial Shaft. Acta Orthopaedica Scandinavica: Vol. 46, No. 2, pp. 256-268.

Stress and strain in the mandibular symphysis of primates: a test of competing hypotheses.

Abstract: The primary purpose of this study was to test various hypotheses about symphyseal stress in primates. First, those patterns of symphyseal strain that would be associated with various hypothetical patterns of symphyseal stress were formulated. Then these hypothetical patterns of stress and strain were tested by comparing the formulated bone strain pattern with actual in vivo symphyseal bone strain patterns. Patterns of in vivo symphyseal bone strain were determined by bonding rosette and/or single-element strain gages to the midline of the middle and lower third of the labial aspect of the symphysis of six adult Macaca fascicularis. Following recovery from the anesthetic, bone strain was recorded during mastication, incision, and isometric biting. Symphyseal bone strain was also recorded during yawning, licking, and threat behaviors. The data suggest that during the power stroke of mastication, the macaque symphysis is predominately sheared dorsoventrally and/or twisted about a transverse axis and bent by lateral transverse bending of the mandibular corpora. During lateral transverse bending of the mandibular corpora, the labial aspect of the macaque symphysis experiences compressive bending stress, while the lingual aspect experiences tensile bending stress. During the opening stroke of mastication and during other jaw opening behaviors, the macaque symphysis is bent by medial transverse bending of the mandibular corpora. At this time the labial aspect of the symphysis experiences tensile bending stress, while its lingual aspect experiences compressive bending stress. During both the power and opening strokes of mastication, the macaque mandible is bent in the plane of its curvature, and therefore the mandible acts as a curved beam. This is important because it results in elevated levels of stress along the lingual aspect of the macaque symphysis, particularly during the power stroke of mastication. During the power stroke of incision, the local effects of the bite force are unknown; however, at this time the lower half of the macaque symphysis is both sheared dorsoventrally and bent due to twisting of the mandibular corpora about their long axes. The results of this stress analysis have implications for understanding the mechanical attributes of symphyseal structure. In order to counter dorsoventral shear, the most important symphyseal attribute is to have adequate cross-sectional area of bone in the plane of the applied stress. In contrast, both the cross-sectional area of bone and symphyseal shape is important in order to counter stress effectively during symphyseal torsion and the three symphyseal bending regimes.(ABSTRACT TRUNCATED AT 400 WORDS)