204 research outputs found
UIU President Chauncey P. Colegrove
No full textDr. Chauncey P. Colegrove, Class of 1881, was President of Upper Iowa University from 1916 to 1920 during the time the university raised funds to erase its debt and build a new gymnasium (now Edgar Fine Arts). Chauncey’s brother was Albert Le Grande Colgrove, Class of 1882 (notice the difference in spelling, Albert dropped the ‘e’ in Colegrove). Albert married Laura May Walker. Laura had been a student in the collegiate and business college at UIU, she graduated with a bachelor’s degree in 1883, and an M. A. in 1885. Their son, Chauncey’s nephew, was Dr. Chester W. Colgrove.
Chester and his wife donated funds in honor of his parents, Albert Le Grande and Laura Walker Colgrove to build the Colgrove Walker building on campus.[Title], Upper Iowa University Digital Archives, [Reference URL]. See 'About' page for more information
Model for predicting heat generation and temperature in friction stir welding from the material properties
No full textThis paper describes a simple numerical model for predicting the heat generation
in friction stir welding (FSW) from the material hot deformation and thermal
properties, the process parameters, and the tool and plate dimensions. The model
idealises the deformation zone as a two-dimensional axisymmetric problem, but
allowance is made for the effect of translation by averaging the three-
dimensional temperature distribution around the tool in the real weld. The model
successfully predicts the weld temperature field and has been applied with
minimal recalibration to aerospace aluminium alloys 2024, 7449 and 6013, which
span a wide range of strength. The conditions under the tool are presented as
novel maps of flow stress against temperature and strain rate, giving insight
into the relationship between material properties and optimum welding
conditions. This highlights the need in FSW for experimental high strain rate
tests close to the solidus temperature. The model is used to illustrate the
optimisation of process conditions such as rotation speed in a given alloy and
to demonstrate the sensitivity to key parameters such as contact radius under
the shoulder, and the choice of stick or slip conditions. The aim of the model
is to provide a predictive capability for FSW temperature fields directly from
the material properties and weld conditions, without recourse to complex
computational fluid dynamics (CFD) software. This will enable simpler
integration with models for prediction of, for example, the weld microstructure
and properties
Numerical and artificial neural network modelling of friction stir welding
No full textThis thesis is based on the PhD work of investigating the Friction Stir Welding process
(FSW) with numerical and Artificial Neural Network (ANN) modelling methods. FSW
was developed at TWI in 1991. As a relatively new technology it has great advantages
in welding aluminium alloys which are difficult to weld with traditional welding
processes. The aim of this thesis was the development of new modelling techniques to
predict the thermal and deformation behaviour.
To achieve this aim, a group of Gleeble experiments was conducted on 6082 and 7449
aluminium alloys, to investigate the material constitutive behaviour under high strainrate,
near solidus conditions, which are similar to what the material experiences during
the FSW process. By numerically processing the experimental data, new material
constitutive constants were found for both alloys and used for the subsequent FSW
modelling work. Importantly no significant softening was observed prior to the solidus
temperature.
One of the main problems with numerical modelling is determining the values of
adjustable parameters in the model. Two common adjustable parameters are the heat
input and the coefficients that describe the heat loss to the backing bar. To predict these
coefficients more efficiently a hybrid model was created which involved linking a
conventional numerical model to an ANN model. The ANN was trained using data from
the numerical model. Then thermal profiles were abstracted (summarised) and used as
inputs; and the adjustable parameters were used as outputs. The trained ANN could then
use abstracted thermal profiles from welding experiments to predict the adjustable
parameters in the model.
The first stage involved developing a simplified FE thermal model which represents a
typical welding process. It was used to find the coefficients that describe the heat loss to
the backing bar, and the amount of power applied in the model. Five different thermal
boundary conditions were studied, including both convective and ones that included the
backing bar with a contact gap conductance. Three approaches for abstracting the thermal curves and using as inputs to the ANN were compared. In the study, the
characteristics of the ANN model, such as the ANN topology and gradient descent
method, were evaluated for each boundary condition for understanding of their
influences to the prediction. The outcomes of the study showed that the hybrid model
technique was able to determine the adjustable parameters in the model effectively,
although the accuracy depended on several factors. One of the most significant effects
was the complexity of the boundary condition. While a single factor boundary condition
(e.g. constant convective heat loss) could be predicted easily, the boundary condition
with two factors proved more difficult. The method for inputting the data into the ANN
had a significant effect on the hybrid model performance. A small number of inputs
could be used for the single factor boundary condition, while two factors boundary
conditions needed more inputs. The influences from the characteristics of the ANN
model were smaller, but again thermal model with simpler boundary condition required
a less complex ANN model to achieve an accurate prediction, while models with more
complex boundary conditions would need a more sophisticated ANN model.
In the next chapter, the hybrid method was applied to a FSW process model developed
for the Flexi-stir FSW machine. This machine has been used to analyse the complex
phase changes that occur during FSW with synchrotron radiation. This unique machine
had a complex backing bar system involving heat transfer from the aluminium alloy
workpiece to the copper and steel backing bars. A temperature dependent contact gap
conductance which also depends on the material interface type was used. During the
investigation, the ANN model topologies (i.e. GFF and MFF) were studied to find the
most effective one. Different abstracting methods for the thermal curves were also
compared to explore which factors (e.g. the peak temperature in the curve, cooling slope
of a curve) were more important to be used as an input. According to close matching
between the simulation and experimental thermal profiles, the hybrid model can predict
both the power and thermal boundary condition between the workpiece and backing bar.
The hybrid model was applied to six different travel speeds, hence six sets of heat input
and boundary condition factors were found. A universal set was calculated from the six
outcomes and a link was discovered between the accuracy of the temperature
predictions and the plunge depth for the welds. Finally a model with a slip contact condition between the tool and workpiece was used
to investigate how the material flow behaviour was affected by the slip boundary
condition. This work involved aluminium alloys 6082-T6 and 7449-T7, which have
very different mechanical properties. The application of slip boundary condition was
found to significantly reduce the strain-rate, compared to a stick condition. The slip
condition was applied to the Flexi-stir FSW experiments, and the results indicated that a
larger deformation region may form with the slip boundary condition.
The thesis successfully demonstrates a new methodology for determining the adjustable
parameters in a process model; improved understanding of the effect of slip boundary
conditions on the flow behaviour during FSW and insight in to the behaviour of
aluminium alloys at temperatures approaching the solidus and high strain-rates
A comparison of track initiation with PDAF and PMHT
No full text© 2002 Institution of Electrical EngineersA problem with many algorithms for target tracking is that they are designed to update tracks under the assumption that the tracks correspond to real targets, and that the initial conditions of the targets are known. In practice, this is not the case, and practical algorithms must be capable of track initiation and termination. One method of solving these problems is to introduce a Markov model to estimate the validity of each track. This approach has been referred to as target visibility. This paper compares the single target track initiation performance of the probabilistic data association filter (PDAF) with the probabilistic multi-hypothesis tracker (PMHT) when each uses the visibility target model.S.J. Davey, S.B. Colegrove, and D.A. Gra
Supplemental Material, DS1_VET_10.1177_0300985819829526 - Polyphasic Rhabdomyositis in California Sea Lions (<i>Zalophus Californianus</i>): Pathology and Potential Causes
No full textSupplemental Material, DS1_VET_10.1177_0300985819829526 for Polyphasic Rhabdomyositis in California Sea Lions (Zalophus Californianus): Pathology and Potential Causes by Mauricio Seguel, Kathleen M. Colegrove, Cara Field, Sophie Whoriskey, Tenaya Norris and Padraig Duignan in Veterinary Pathology</p
Measuring the process efficiency of controlled gas metal arc welding processes
No full textThe thermal or process efficiency in gas metal arc welding (GMAW) is a crucial
input to numerical models of the process and requires the use of an accurate
welding calorimeter. In this paper, the authors compare a liquid nitrogen
calorimeter with an insulated box calorimeter for measuring the process
efficiency of Fronius cold metal transfer, Lincoln surface tension transfer and
RapidArc, Kemppi FastRoot and standard pulsed GMAW. All of the controlled dip
transfer processes had a process efficiency of ∼85% when measured with the
liquid nitrogen calorimeter. This value was slightly higher when welding in a
groove and slightly lower for the RapidArc and pulsed GMAW. The efficiency
measured with the insulated box calorimeter was slightly lower, but it had the
advantage of a much smaller random err
Welding process impact on residual stress and distortion
No full textResidual stress and distortion continue to be important issues in shipbuilding
and are still subject to large amounts of research. This paper demonstrates how
the type of welding process influences the amount of distortion. Many shipyards
currently use submerged arc welding (SAW) as their welding process of choice. In
this manuscript we compare welds made by SAW with DC gas metal arc welding,
pulsed gas metal arc welding, Fronius Cold Metal Transfer (CMT), autogenous
laser and laser hybrid welding on butt welds in 4mm thick DH36 ship plate. Laser
and laser hybrid welding were found to produce the lowest distortion.
Nevertheless a considerable improvement can be achieved with the pulsed gas
metal arc welding and CMT processes. The paper seeks to understand the
relationship between heat input, fusion area, measured distortion and the
residual stress predicted from a simple numerical model, and the residual
stresses validated with experimental data
Modelling distortion reduction on pre- and post-weld rolled gas metal arc welded plates
No full textResidual stress generated during welding can cause distortion, especially when
appliedon relatively thin plates. There are several standard and well documented
techniquesto reduce distortion and residual stress after welding, however these
techniques areoften costly and time consuming to implement on an industrial
scale. In this paper wedemonstrate the pre- and post-weld rolling techniques for
reducing weld distortion. Pre-Weld Rolling (PWR) can be applied before
fabrication, potentially by the steelmanufacturer. An experimental investigation
indicated that there was an average 38%reduction of distortion with this
technique. Finite element analysis (FEA) was used todetermine the stress
distribution to understand the phenomenon
Comparison of joining efficiency and residual stresses in laser and laser hybrid welding
No full textLaser welding is a high energy density process, which can produce welds with
less energy input and thereby lower residual stress generation compared to arc
welding processes. However, the narrow beam dimension makes it extremely
sensitive in terms of fit up tolerance. This causes a problem in achieving high
quality welds. Laser with arc hybrid process overcomes such issues. In this
paper, longitudinal residual strains were compared for autogenous laser welding
and laser/TIG hybrid processes. Joining efficiency, which is defined by the
penetration depth achieved per unit of energy input, was correlated with the
residual strain generation. It has been shown that to achieve a specific
penetration depth, there is an optimum welding condition for each of the welding
processes, which will give minimum tensile residual stress generation. The
results imply that for the same penetration depth, hybrid process resulted in
similar to 50% higher tensile longitudinal domain compared to autogenous laser
First detection of otarine herpesvirus-1 in South America: Characterizing the epidemiology in a Peruvian pinniped population
No full textOtarine herpesvirus-1 (OtHV-1) is associated with high rates of urogenital carcinoma in free-ranging California sea lions (Zalophus californianus), but rarely considered a conservation concern in the southern hemisphere. The objective of this study was to survey free-ranging South American sea lions (Otaria byronia) and Peruvian fur seals (Arctocephalus australis unnamed subspecies) in Punta San Juan, Peru for OtHV-1 and to determine prevalence by demographic factors. Twenty-one percent (14/67) of urogenital swabs collected over three years (2011, 2014, 2015) from live pinnipeds tested positive with a pan-herpesvirus conventional PCR. Sequencing revealed 99% homology to OtHV-1 at the DNA polymerase gene. Urogenital, conjunctival, and oropharyngeal swabs collected from 136 live pinnipeds at Punta San Juan between 2011-2018 were then assayed using quantitative PCR for a segment of the OtHV-1 DNA polymerase gene. In total, 38.6% (51/132) of urogenital swabs, 5.6% (4/71) of conjunctival swabs, and 1.1% (1/90) of oropharyngeal swabs were positive for OtHV-1. Agreement in OtHV-1 detection between sampling sites was minimal to non-existent (Cohen’s Kappa=0.027-0.386). The most parsimonious multivariable logistic regression model predicting OtHV-1 detection (P < 0.0001) included species and age class, with South American sea lions (32/81, 39.5%) having a higher prevalence of OtHV-1 in urogenital swabs than Peruvian fur seals (19/51, 37.2%), and adults (46/95, 48.4%) having a higher prevalence than pups (5/37, 13.5%). In addition, female South American sea lions had higher copy numbers (median=8,819 copies/ng DNA) than males (median: 27 copies/ng DNA, P=0.012), and adult South American sea lions (median=219 copies/ng DNA) had higher copy numbers than pups (median: 3 copies/ng DNA, P=0.008). The much higher prevalence in adults compared with pups, as well as the higher sensitivity in urogenital swabs, suggests a sexual transmission, which is similar to California sea lions. These data provide insight into dynamics of the potentially oncogenic OtHV-1 in a novel ecosystem, emphasizing the importance of continued disease surveillance in vulnerable Peruvian marine mammal populations.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-05-01The student, Karisa Tang, accepted the attached license on 2019-04-10 at 15:28.The student, Karisa Tang, submitted this Thesis for approval on 2019-04-10 at 16:01.This Thesis was approved for publication on 2019-04-23 at 15:50.DSpace SAF Submission Ingestion Package generated from Vireo submission #13553 on 2019-08-22 at 16:21:00Made available in DSpace on 2019-08-23T20:44:42Z (GMT). No. of bitstreams: 2
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