Date of Award

Spring 2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering - (Ph.D.)

Department

Mechanical Engineering

First Advisor

E. S. Geskin

Second Advisor

Bernard Koplik

Third Advisor

R. S. Sodhi

Fourth Advisor

Avraham Harnoy

Fifth Advisor

N. M. Ravindra

Abstract

The objective of this research is developmentof aknowledge base of materials processing by the impact of high-speed liquid projectiles. The work involved experimental study of generation and applications of high-speed liquid projectiles. The projectiles were generated by the launchers, which used gunpowder as an energy source. The experiments were carried out at the low (O.35g of the powder), middle (1.2g) and high (10g to 70g) levels of energy consumptions and at several different launchers modification.

Experimental investigation of effect of gun powder mass on energy of projectile was conducted for ductile and brittle targets. An array of experimental techniques for projectile's external ballistics investigation was developed. Laser Particle Velocitimeter (PIN) and high speed filming were used for velocity measurements and visualization of images of water projectiles high speed filming revealed pulsing nature of projectile. A piezoelectric sensor and a pendulum were used to monitor the impact force and the projectile momentum.

Range of materials was investigated in this study. Namely, investigation of deformation, forming, micro-forming, and welding of ductile materials was carried out. Demolition and boring of brittle materials was performed. Modes and mechanisms of deformation of ductile and brittle materials were studied and explained. High plasticity, high rate of deformation, temperature at the impact zone, hardness and micro-hardness distribution and degree of deformation work for ductile materials were determined and materials behavior knowledge base needed for materials processing was acquired. Modes and mechanisms of failure of ductile, brittle and composite materials were studied. Fractography study revealed three mechanisms: ductile overload fracture, brittle fracture and combination of the two. Six failure modes: brittle fracture, radial fracture, ductile hole growth, plugging, fragmentation and petaling were identified.

An array of material processing operations using high speed projectiles impact was investigated. Full scale experimental investigation of terminal ballistics of high speed water projectiles was performed. Material processing operations included: piercing of metals, piercing of composite targets, explosive set ups neutralization, demolition of brittle materials, boring of granite and marble, punching of steel plates, complex shape punching in steel, forging of metals on macro and meso scale. Mechanisms of punching and forming of metals were identified and proposed. Welding of similar and dissimilar metals was conducted and high potential for novel stitch and spot welding formations was confirmed. Micro scale materials processing investigation involved range of studies. Submilimeter geometry scale forming of metals, fine stamping, micron scale forming and micron scale extrusion investigation were conducted and validation of novel technologies was achieved. Full scale topography and surface characterization of generated geometries was conducted and obtained quality proved to be at a competitive level with existing technologies. State of the art methods were used for investigation of generated samples. Scanning electron microscopy, infinite focus microscopy, 3 D digital microscopy, optical microscopy, 3-D digital profiler, Knoop and Vickers micro hardness testers, nano hardness indenter were used for characterization of generated samples. Full scale characterization on all levels of conducted materials processing was conducted and effect of high speed water projectile impact on mechanical properties of impacted materials was quantified and presented. Investigation of peculiarities of impact based micro-forming was conducted. The info acquired as result of investigation of geometry and topography of micro-forming processing. Accuracy of micro scale deformation was estimated, particularly it was shown that deviation of actual part from the die was at the acceptable level. Also was shown that size of generated parts was rather stable and roughness and waviness of the generated surfaces was in the acceptable range.

The foundation of knowledge base for liquid based forming, welding and demolition processes was developed and the process technology will be developed on the base of the acquired knowledge. Theory of impact based high rate material deformation was enhanced. The emerging industrial scale demolition, forming and welding technologies will utilize the acquired knowledge.

Share

COinS