Dynamic Consolidation Research Articles

The Finite Element Method in the Static and Dynamic Deformation and Consolidation of Porous Media - R.W. Lewis and B.A. Schrefler

The Finite Element Method in the Static and Dynamic Deformation and Consolidation of Porous Media - R.W. Lewis and B.A. Schrefler

Structural Stability of Nanocrystalline NiAl

Abstract NiAl is an important high temperature structural material, with a high melting point (1640°C), low density and excellent high temperature oxidation resistance. The room temperature ductility of NiAl may potentially be improved with the use of nanocrystalline grain size. However, a key question concerning the application of nanostructured NiAl is about its structural stability at high temperature. The current study is thus focused on the investigation of the structural stability of nanocrystalline NiAl using in-situ transmission electron microscopy (TEM) and differential thermal analysis (DTA). Nanocrystalline B2-NiAl was prepared by ball milling (24 hrs) from elemental Ni and Al powders. Subsequent consolidation into bulk form was performed using dynamic consolidation employing a 3-capsule plate-impact fixture at approximately 400 m/s [1-3]. Powder nanocrystalline NiAl was dispersed on a holey carbon film for TEM observation. TEM specimens of shock compacted bulk NiAl nanocrystals were prepared by cutting, polishing, dimpling and ion milling.

Modelling of dynamic consolidation of titanium-silicon carbide powders: W. Tong et al. (University of Nebraska, USA.) Model. Simul. Mater. Sci. Eng., vol 3, no 6, 1995, 771–796

Modelling of dynamic consolidation of titanium-silicon carbide powders: W. Tong et al. (University of Nebraska, USA.) Model. Simul. Mater. Sci. Eng., vol 3, no 6, 1995, 771–796

The rate-dependent deformations of porous pure iron

Abstract A combined experimental and analytical investigation of the finite viscoplastic deformations of porous pure iron is presented. The intent is to provide information useful to the simulation of near-net-shape forming and dynamic powder consolidation processes. Samples of porous pure iron were prepared by cold-isostatic-pressing and subsequent heat-treatment. The final pore volume fractions obtained ranged from zero to 31%. The porous metal was then subjected to compressive: deformations to large strains (as high as 35%) at both quasistatic (10 −4 s −1 ) and high (>10 +3 s −1 ) rates of deformation. Stress-strain curves were obtained over the range of strain rates for each porosity. Special techniques were developed to recover the samples after loading by a single compressive pulse, so that the recovered specimens could be examined to determine the evolution of the microstructure as a result of deformation. Next, a finite deformation viscoplastic model based on the theory of composites is formulated. The model requires information on the ‘matrix’ material (obtained from the fully dense iron) and on the porosity (considered to be an internal variable). Because of the finite deformations that are developed, the evolution of the porosity has been incorporated into the model. Numerical simulations of the experiments based on this model are able to provide reasonable predictions of the observed behavior.

Dynamic consolidation of aluminium and Al-20 V/o SiCp composite powders

Aluminium powders and Al-SiCp composite powders have been compacted in the form of cylinders using explosives. The effect of processing parameters such as the explosive pad thickness and the impact energy on the density of the compacts has been investigated. The microstructural variations in the compacts have been studied with respect to the explosive pad thicknes used and pressures imparted on the powder compacts. The hardness variation over the cross section of the Al-20 V/o SiCp composite compacts have been studied with respect to the variation in the thickness of the explosive pads. The optimum processing conditions for the production of compacts of aluminium and Al-20 V/o SiCp systems by dynamic compaction have been defined.

Study of pore pressures induced in laboratory dynamic consolidation: M. Gunaratne, M. Ranganath, S. Thilakasiri, G. Mullins, P. Stinnette & C. Kuo, Computers & Geotechnics, 18(2), 1996, pp 127–143

Study of pore pressures induced in laboratory dynamic consolidation: M. Gunaratne, M. Ranganath, S. Thilakasiri, G. Mullins, P. Stinnette & C. Kuo, Computers & Geotechnics, 18(2), 1996, pp 127–143

Analytical solution for two-dimensional dynamic consolidation in frequency domain: S. Valliappan, J. T. Yazdi & C. Zhao, International Journal for Numerical & Analytical Methods in Geomechanics, 19(10), 1995, pp 663–682

Analytical solution for two-dimensional dynamic consolidation in frequency domain: S. Valliappan, J. T. Yazdi & C. Zhao, International Journal for Numerical & Analytical Methods in Geomechanics, 19(10), 1995, pp 663–682

Dynamic consolidation of mixed fill—a cost-effective alternative to piling: a case record

An offic building was to be constructed in a 15 m deep gravel pit filled about 9 m of various materials, a large percentage of which consisted of boulder accumulations and loose granular material, partly mixed with dry crust clay and waste from previous building activities. This technical note describes the considerations behind the choice of foundation method and the outcome of the chosen method.

Study of pore pressures induced in laboratory dynamic consolidation

Knowledge of the pore pressure behavior during dynamic impacts on moderately low permeability soils is essential in averting possible liquefaction and effective field implementation of dynamic consolidation. Although field observations of dynamically induced pore pressures are abundant in the literature, analytical or numerical approaches for pore pressure prediction are scarce. Herein, the authors advance a simple technique to analytically model the laboratory dynamic consolidation by modifying the classical Terzaghi's static consolidation theory. Since the analytical prediction of dynamic surface stress and experimental verification are performed in a companion paper, the surface stress due to a dynamic impact is assumed to be known in this work. Then, the time dependent stress pulse is de-synthesized into a number of constant load steps to predict the subsequent pore pressure behavior. Since this methodology accounts for even the dynamic stress attenuation within the soil sample, a rigorous closed form solution has to be replaced by a numerical solution. It is shown how this solution rapidly converges when the load steps are made sufficiently small. Finally, the analytical predictions of dynamic pore pressure are verified by well controlled laboratory experiments performed on a special apparatus set up at the University of South Florida.

Dynamic Permeability, Consolidation and Deformation Structures in Accretionary Prism Sediments: ABSTRACT

Dynamic Permeability, Consolidation and Deformation Structures in Accretionary Prism Sediments: ABSTRACT

Particle-level modeling of dynamic consolidation of Ti-SiC powders

Shock wave processing of Ti-SiC powders has been numerically analyzed at the particle level using an Eulerian finite-element methodology. The analysis reveals that the shock consolidation is dominated by the viscoplastic deformation of Ti particles and that inertia plays a significant role in setting the magnitude of the shock rise time (i.e. the consolidation time). The addition of SiC particles is found to reduce slightly the degree of the localized deformation and the temperature rise around the Ti particle surfaces (the hot spots). The local temperature distribution and the thermal history of the hot spots from the simulation are found to be useful in estimating the initiation and growth of the interfacial reaction layer between Ti and SiC. The final particle packing configuration of Ti/SiC powder mixtures and the Ti-SiC reaction layer thickness predicted by the simulations are found to be consistent with experimental observations. Our study indicates that a combination of shock wave processing of powders by plate impact experiments with soft recovery capabilities and the accompanying numerical simulation of these experiments at the particle level holds promise for understanding thermal-mechanical mechanisms during shock consolidation of reactive powders.

Analytical solution for two‐dimensional dynamic consolidation in frequency domain

AbstractAn analytical solution to the two‐dimensional wave propagation in fluid‐saturated half‐space subjected to a strip load with vertical harmonic oscillation at the surface is presented. The basic equations have been derived on the basis of Biot's linear theory of poro‐elasticity and then solved using Fourier complex transform for the horizontal direction. The importance of a number of soil characteristics including compressibility, degree of saturation and soil permeability has been examined. It is shown that the effect of pore fluid is dominant only for fully saturated soils with incompressible solid grains and low permeability. For partially saturated, compressible or very permeable soils, the stresses would be mainly transferred to solid part and there will be considerable reduction in pore pressure amplitude.

Dynamic consolidation of metastable nanocrystalline powders

Nanocrystalline metal powders synthesized by mechanical alloying in a ball mill resulted in micron-sized powder particles with a nanosized (5 to 25 nm) substructure. Conventional consolidation methods resulted in considerable coarsening of the metastable nanometer crystallites, but dynamic consolidation of these powders using explosive techniques produced fully dense monoliths while retaining the 5- to 25-nm substructure. Numerical modeling, used to guide the experimental phase, revealed that the compression wave necessary for suitable consolidation was of the order of 10 GPa for a few tenths of a microsecond. The consolidation process is described, and the retention of the metastable nanostructure is illustrated.

Dynamic magnetic consolidation for compaction of advanced materials: B. Chelluri (IAP Reasearch Inc, Dayton, Ohio, USA) Mater. and Manuf. Process., vol 9, no 6, 1994, 1127–1142

Dynamic magnetic consolidation for compaction of advanced materials: B. Chelluri (IAP Reasearch Inc, Dayton, Ohio, USA) Mater. and Manuf. Process., vol 9, no 6, 1994, 1127–1142

Dynamic magnetic consolidation and compaction of tungsten alloy powders: B. Chelluri et al (IAP Research Inc, USA)

Dynamic magnetic consolidation and compaction of tungsten alloy powders: B. Chelluri et al (IAP Research Inc, USA)

Dynamic Magnetic Consolidation (DMC) Process for Powder Consolidation of Advanced Materials

Abstract This paper describes a novel rapid consolidation technique called Dynamic Magnetic Compaction (DMC) for consolidating advanced material powders. DMC utilizes pressures generated from pulsed electromagnetic fields to form net shape parts. The consolidation occurs rapidly in less than a millisecond via pressure wave propagation through the powders. Powders of different materials such as intermetallics, refractory alloys, ceramics, nano materials and composites can be fabricated into full density parts using DMC. The principles and benefits of the DMC technique for advanced material fabrication along with a summary of feasibility results on tungsten steel composites will be described.

Explosively consolidated PVC-alumina powder mixtures

The ever-increasing interest in the manufacture of cheap, highly abrasive, but, at the same time, very strong materials possessing good wear-resistant properties has focused attention on the explosive powder-consolidating technique. This particular route has been exploited industrially in the areas of metallic and ceramic blends, but it is only more recently that the possibility of using polymeric particulate matrices has been investigated. The main attraction of dynamic consolidation lies in its ability to create conditions under which, as a result of the passage of a shock wave, inter-particle bonding becomes possible where, in consequence, the strength of the compact is enhanced. A relatively soft polymeric matrix, in conjunction with a hard, abrasive alumina material, forms a blend that combines strength with low manufacturing costs.

Dynamic consolidation of superhard materials

Shock consolidation experiments were conducted via flyer impact on synthetic diamond (6–12 μm) and cubic boron nitride (c-BN) (4–8 μm) admixed with SiC whisker (SCW), Si3N4 whisker (SNW), SiC powder, and Si powder contained in stainless steel capsules under the shock pressure range of 10–30 GPa. Scanning electron microscopy and transmission electron microscopy imaging of the samples revealed no plastic deformation or melting of diamond and virtually no deformation of c-BN, whereas the SCW and SNW were extensively melted and recrystallized into bundle-shaped crystallites. In contrast, SiC powder mixed with diamond was also melted but demonstrated equant grain growth. A new method to calculate the shock temperature and melt fraction is formulated on the basis of Milewski's sphere-rod packing data. The new method assigns excess bulk volume to the zone around whiskers and yields a better description of the energy deposition mechanism of the consolidation of powder-whisker systems. Some of the experiments employed Sawaoka's post-shock annealing technique, in which the sample is sandwiched between two layers of a mixture of titanium powder plus carbon. Very well consolidated samples were obtained with post-shock heating under shock pressures of only about 11 GPa. Micro-Vickers hardness values up to 27 GPa were obtained for c-BN plus SCW at a low impact velocity of 1.45 km/s with post-shock heating. This hardness is similar to that obtained at a higher impact velocity of 1.95 km/s without post-shock heating. To understand the post-shock heating process, one-dimensional time dependent temperature profile calculations were conducted for the sample and Ti + C layers. Post-shock heating appears to be very important in the consolidation of powder and whisker admixture. The calculated optimum Ti + C thickness is about 0.8–1.7 mm at a porosity of 40% for a typical sample thickness of 2 mm. The heating and cooling time is a few milliseconds. Good compacts with micro-Vickers hardness values up to 28 GPa were also obtained upon shock consolidation of diamond plus Si admixtures.

Dynamic consolidation of porous copper iron and tungsten : C.N. Elias. (Institute of Military Engineering, Rio de Janeiro, Brasil.)

Dynamic consolidation of porous copper iron and tungsten : C.N. Elias. (Institute of Military Engineering, Rio de Janeiro, Brasil.)

Peculiarities and applications of dynamic consolidation in ground treatment of collapsible loess deposits : Yihui Qui; Yuling Guo; Shaobin Zhou; Meiyun Shi; Weiyuan Fan; Shuju Fan Proc 6th International Congress International Association of Engineering Geology, Amsterdam, 6–10 August 1990V3, P1761–1768. Publ Rotterdam: A A Balkema, 1990

Peculiarities and applications of dynamic consolidation in ground treatment of collapsible loess deposits : Yihui Qui; Yuling Guo; Shaobin Zhou; Meiyun Shi; Weiyuan Fan; Shuju Fan Proc 6th International Congress International Association of Engineering Geology, Amsterdam, 6–10 August 1990V3, P1761–1768. Publ Rotterdam: A A Balkema, 1990