A1-3.85% Cu single crystals were studied by means of the back-reflection divergent X-ray beam method after solution treatment, various modes of quenching and various stages of age-hardening. A complete strain analysis was developed by which the principal strains in a crystal or polycrystalline material can be determined provided the changes of d-spacings of more than six independent (hkl)reflections are recorded. The analysis applied to the various stages of age-hardening of crystals subjected to a fast quench after solution treatment disclosed an anisotropy of strain distribution in the matrix. The maximum strain corresponding to the ageing stage associated with the formation of G. P. zones coincided with one of the [100] directions and shifted about 20 ° when the 0' phase was predominant. The anisotropy of strain distribution was interpreted in terms of a preferred vacancy migration due to thermal and concentration gradients introduced by quenching.

In Resin Transfer Molding (RPM), which is a process to manufacture polymer composites, the impregnation of fibrous reinforcement In the form of mats by a thermosetting resin is modeled as the flow of a Newtonian liquid through a single length‐scale porous medium. While this approach is sufficiently accurate for random fiber‐mats, it can lead to appreciable errors when applied to woven, braided, or stitched fiber‐mats that contain two length scales. This work investigates the primary factors governing the isothermal unsaturated flow through such dual‐scale porous media. Two studies were conducted to better understand this phenomenon: the first experimenatally investigated the flow, while the second theoretically modeled the flow and identified important parameters affecting such a flow with the help of dimensionless analysis. In the first study, one‐dimensional constant injection rate experiments were performed using various fiber mats. The unsaturated flow behavior of various mats was characterized using a constant “sink” term in the continuity equation. Results indicated that for a given fiber‐mat, the magnitude of the sink effect was a function of the capillary number. In the second study, a numerical model was developed to describe flow through dual‐scale preforms in which the two flow domains, the inter‐ and intra‐tow regions, were coupled. We identified a dimensionless number called the sink effect index ψ that characterizes the magnitude of liquid absorption by the tows and is a function of the relative resistance to flow in the tow and inter‐tow regions, and the packing density of the tows. The parametric study of this index with the help of numerical simulations reveals its influence on the flow and identifies the distinct transient and steady‐state flow regimes.

The Resin Transfer Molding (RTM) manufacturing process is frequently used to fabricate parts consisting of doubly curved shells. Woven and stitched bi-directional fabrics deform when draped over tooling surfaces with double curvatures. This deformation results in a corresponding change in the preform's permeability tensor, which will change the fluid impregnation pattern during mold filling stage. This paper presents the results of a study in which flow through deformed preforms was investigated. Experiments were conducted in which two different preforms were radially injected after being sheared to a specified angle. The resulting elliptical flowfronts were used to determine the change in the orientation and degree of anisotropy of the permeability tensor caused by the preform's deformation. The experimental results were then compared with a numerical model developed to describe flow through typical RTM preforms using a deformable unit cell. The anisotropy ratio of the principal permeability tensor was found to increase with the shearing angle as observed experimentally and was verified by the numerical model. The success of the RTM mold design and the accuracy of mold filling simulations are dependent on the use of the correct spatial permeability tensor inside the mold. A predictive model that can provide the permeability changes as a function of local shearing deformation within the draped and compacted preforms should move us closer to a realistic simulation of mold filling in net-shaped composite structures.

A stress-strain analysis of single cubic crystals is developed which utilizes the strain data supplied by the x-ray back-reflection divergent beam method. The principal strains and their directions are determined and from the principal strains and the known elastic constants the complete stress-strain configuration is obtained. Thus the maximum magnitude and the direction of the shearing strain on a given set of crystallographic planes are obtained and the set of planes on which the maximum value of the shearing maxima occurs is also determined. From a knowledge of the stress-strain configuration, the stored elastic energy of the crystal is deduced; it can be partitioned into two components, that due to shearing strains and that due to a mixture of normal and shearing strains. The conditions under which the principal stress system coincides with the principal strain system are also investigated. Furthermore, a number is constructed that measures the distortion of the crystal in terms of the energy increments associated with the elastic constants. The stress-strain analysis applied to the ordering of a CuAu crystal at 125°C corroborates quantitatively the qualitative results previously obtained by transmission electron microscopy. The dependence of stored elastic energy on annealing time is determined and it is shown that the first maximum and decline are associated with the maximum and decline of coherency strains set up between the ordered CuAu I nuclei and the disordered matrix. Upon increasing the annealing time, twinning occurs to relieve the tetragonality strains introduced by the ordered CuAu I domains. The second maximum is compounded by twinning on certain (110) planes and delayed ordering on other (110) planes of the matrix. The subsequent decline of the stored elastic energy is associated with twinning on all (110) planes. The shearing stress necessary to initiate microtwinning does not exceed 7×108 dyn/cm2.

The technique of the new x-ray double spectrometer method as described in a former paper1 is applied to the study of angular misalignment of crystal structure in alloys. To obtain a better statistical evaluation of the x-ray intensity data the method is extended to include arrays of spots on the Debye-Scherrer lines at high elevations. A complete mathematical discussion of the photometric transformation of the crystallite rocking curves is presented. The specimens investigated include a low carbon alloy annealed at 850°C and three silicon ferrite samples annealed at 980°, 1100°, and 1200°C. The quantitative data obtained disclose a significant dependence of crystal perfection on annealing temperature, and demonstrate clearly that the angular misalignment of the coherently reflecting regions within the grains decreases with annealing temperature provided this temperature is not excessive. Valuable information regarding the influence of cold rolling on the subsequent annealing process is obtained. Thus, the extent of partial recrystallization of the silicon ferrite is deduced from the statistical data, and the differential grain size between the surface layers and the interior of the specimen is revealed through the study of the diffraction effects with radiation of different wavelengths. A mechanism of grain bending during plastic deformation is suggested and a relationship between magnetic properties, annealing temperature, and crystal perfection of the silicon ferrite is pointed out.