771 research outputs found
GRIMKE, Angelina
No full textIn honor of his aunt, Angelina Emily Grimke Weld (1805- 1875), a noted abolitionist and feminist, Archibald Grimke named his daughter, the only child: Angelina Weld Grimke. Angelina Weld Grimke (1880-1958) was a prolific author of poetry, drama, and short stories. Among her most noted writings are, the plays Rachel published in 1921, and the poem The Black Finger , first published in Opportunity in 1923
Arc welding of high strength aluminium alloys for armour systems applications
No full textThe ternary Al-Cu-Mg system 2xxx series aluminium alloys were examined as construction
materials for armour system applications based upon comparable ballistic properties to the
currently employed Al-7xxx series alloys. Utilising MIG welding solidification cracking was
evident when welding constrained Al-2024 candidate base material using Al-2319 filler, the
only available consumable wire for this series. A previously developed thermodynamic
model suggested that an incompatible weld chemistry resulted when welding with this filler
which would result in hot cracking due to a wide weld pool freezing range and a low volume
fraction of eutectic liquid. As this filler wire was the only commercially available Al-2xxx
filler this was seen as the principal limiting factor for exploiting this alloy series. The solution
was to vary and control weld chemistry. Two approaches were taken. Firstly advanced arc
welding was used to control weld dilution with the base material. A clad layer exhibiting a
less crack susceptible composition was deposited using the Cold Metal Transfer process and
the binary Al-2319 filler wire. Onto this layer the same filler could then be deposited to
provide a structural joint. Although not fully validated, by limiting weld dilution with the
base material this technique showed potential as an alternative method for suppressing
solidification cracking. The second approach, which forms the core of this work, adapted the
conventional tandem MIG welding process to mix different series consumable fillers in a
single weld pool to control weld composition. A range of ternary weld mixtures were
produced which resulted in the development of a robust thermodynamic model. Validation
using this system resulted in weld cracking being eradicated. The concept was then further
developed to weld using three filler wires; this expanded the mixing range and allowed
further model validation. A range of crack free compositions were produced with differing
mechanical properties. An optimum weld composition was determined that was then used for
characterisation of the weldment. By varying heat input, base material HAZ softening was
controlled with joint failure confined to the weld / base material interface. This was attributed
to grain boundary liquation due to the welding temperatures involved resulting in solute rich
grain boundaries. These areas did not deform easily under tensile loading initiating fracture of
the joint. Acceptable joint strengths were realised however ductility was reduced due to the
identified failure mode. Although not tested to military specifications, acceptable mechanical
test values were recorded which were closely compliant with the minimum requirements for
armour system specifications. As a consequence a filler wire composition was recommended
for future prototype development
GRIMKE, Archibald
No full textThe Archibald H. Grimke Papers contain materials that reflect his career as a lawyer, editor, author, lecturer, politician and diplomat. These papers include early correspondence with members of the Grimke-Weld and Grimke-Stanley families, other personal, general and organizational correspondence, legal files, Santo Domingo records (which contain official documents regarding his United States Consulship from 1894 to 1898), financial records, manuscripts, articles, addresses, newspaper clippings, photographs memorabilia, artifacts, and bound publications
The supposed author of the [?]
No full textPortrait of a man in a military uniform decorated with medals. The caption reads "The supposed author of the [illegible]".For more information about this item, visit https://archivesspace.mit.edu/repositories/2/digital_objects/59
Process monitoring and adaptive quality control for robotic gas metal arc welding
No full textThe aim of this research was to develop an adaptive quality control strategy for robotic
gas metal arc welding of thin steel sheets. Statistical methods were used to monitor and
control the quality of welds produced.
The quality of welds cannot be directly measured during welding. It can however be
estimated by correlating weld quality parameters to relevant process variables. It was
found sufficient to do this using welding current and voltage transient signals only.
The strategy developed was problem solving oriented with emphasis on quality
assurance, defect detection and prevention. It was based on simple algorithms developed
using multiple regression models, fuzzy regression models and subjective rules derived
from experimental trials.
The resulting algorithms were used to
control weld bead geometry;
prevent inadequate penetration;
detect and control metal transfer;
assess welding arc stability;
optimise welding procedure;
prevent undercut;
detect joint geometry variations.
Modelling was an integral part of this work, and as a feasibility study, some of the
models developed for process control were remodelled using "Backpropagation"
Artificial Neural Networks. The neural network models were found to offer no
significant improvement over regression models when used for estimating weld quality
from welding parameters and predicting optimum welding parameter.
As a result of the work a multilevel quality control strategy involving preweld parameter
optimisation, on line control and post weld analysis was developed and demonstrated
in a production environment. The main emphasis of the work carried out was on
developing control models and means of monitoring the process on-line; the
implementation of robotic control was outside the scope of this work. The control
strategy proposed was however validated by using post weld analysis and simulation in
software
Three Members of the 96th Service Group
No full textThree Members of the 96th Service Group weld and repair a disabled truck trailer at Oscoda Michigan Army Air Base. Left to Right: 2nd Lieutenant Kenneth C. Traitt, Pfc. Thomas Lee, and Pfc James G. Simmons.https://dh.howard.edu/ccjphotos_332nd/1008/thumbnail.jp
Angelina Weld Daughter of Archibald Grimke
No full texthttps://dh.howard.edu/ajc_grimke_manuscripts/1031/thumbnail.jp
American Historical Association Weld Grimke Letters
No full texthttps://dh.howard.edu/ajc_grimke_manuscripts/1005/thumbnail.jp
Measurements of fluid flow in weld pools
No full textUnderstanding the fluid flow in weld pools contributes significantly toward controlling the heat distribution in the base material and the mass distribution of molten base and additive materials. Currently, most investigations focus primarily on numerical models, due to the experimental difficulties associated with the challenging environment in and around the weld pool. Numerical simulations based on computational fluid dynamics are currently addressing the dynamic behaviour of weld pools, such as melting, solidification, temperature and velocity fields; these results provide information about conditions inside the weld pool that is impossible to gain experimentally. However, there is still a shortage of experimental validation to support these models. In this thesis, experimental methods are applied to study the fluid flow of the weld pool in both arc and laser generated weld pools. The general conclusions from the experimental study provides some suggestions for understanding the fluid flow in the weld pool, such as flow asymmetry, rotational flow and interface instabilities. For example, the interface instabilities can affect the energy and mass distribution. Describing these instabilities numerically requires three dimensional flow models. Moreover, the current experimental results question the validity of works where the surfactant concentration is assumed to be constant in the weld pool without consideration of dynamic diffusion and convection. This work has focused on experimental measurement of the fluid dynamics of weld pools, and current results provide a number of validation cases for further numerical simulations.Materials Science & EngineeringMechanical, Maritime and Materials Engineerin
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