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Results of Performance Tests Performed on the John Watts Casing Connection on 7" Pipe
No full textStress Engineering Services (SES) was contracted by Mr. John Watts to test his threaded connection developed for oilfield oil and gas service. This particular test required the application of a variety of loads including axial tension and compression, internal pressure (gas), external pressure (water), bending and both low and elevated temperature. These loads were used to determine the sealing and structural limits of the connection. The connection design tested had tapered threads with 10 threads per inch. A square thread form and a round thread form were tested. The square thread form had a 2{sup o} load flank and 15{sup o} stab flank. The round thread had a 0{sup o} load flank and 20{sup o} stab flank. Most of the testing was performed on the round thread form. Both a coupled connection design and an integral connection design were tested. The coupling was a pin by pin (male) thread, with the pipe having a box (female) thread. Both designs have outside and inside diameters that are flush with the pipe body. Both designs also contain a small external shoulder. The test procedure selected for this evaluation was the newly written ISO 13679 procedure for full scale testing of casing and tubing connections. The ISO procedure requires a variety of tests that includes makeup/breakout testing, internal gas sealability/external water sealability testing with axial tension, axial compression, bending, internal gas thermal cycle tests and limit load (failure) tests. This test was performed with four coupled samples and included most of these loads. Two integral samples were also included for limit load testing ISO makeup/breakout tests are divided into three types--initial makeup, IML1, repeated makeup within the same sample, MBL, and repeated makeup using several samples called round robin, RR. IMU and MBL were performed in this project. The ISO sealing and structural procedure is divided into four primary tests and identified as Series A, B, C and Limit Load (failure). Series A and B test to 95% actual yield of the pipe and Series C uses 90% of actual yield. Samples 1 and 3 were tested to Series A and the loads are shown in Figure 1. For these samples, the axial compression was limited to 75% pipe body yield, which was set by Mr. Watts at the beginning of the test. Samples 2 and 4 were tested to Series B with loads shown in Figure 2. This series included 20 degrees per 100 feet bending but no external pressure. Due to premature leaks, no samples were subjected to Series C which included mechanical and thermal cycles. Samples 5 and 6 were tested to failure. The project started with the selection and purchase of a popular size of oilfield pipe, which was 7-inch OD, 32 pound per foot, P-110 casing. While the connections were being threaded, material tensile tests were performed to get the actual strength of the 7-inch pipe. The first samples contained a square thread form. Excessive galling was experienced during the first series of makeup/breakout tests and Mr. Watts decided to change the thread form and remachine the samples. The second samples had a round thread form and performed very well in the makeup/breakout tests. Basically no galling occurred of any consequence. Samples 1 and 3 were to be tested with external water (ISO Series A) while samples 2 and 4 were to be tested with bending (ISO Series B, no external pressure). Testing of all four samples started with tension and internal gas pressure. During this initial pressure testing, samples 1, 3 and 4 developed leaks and the test was stopped before any external pressure or bending was applied. Sample 2 successfully tested to ISO Load Point 5 which included bending before developing a leak. Figure 3 shows the loads at which the samples leaked and the relative pipe body performance capability. Sample 1 and end A of sample 2 held a high pressure while samples 3, 4 and end B of sample 2 leaked at relatively low pressures. All of these leaks were with nitrogen gas pressure. After reviewing the results, it was believed that several conditions may have contributed to the premature leaks: The BOL 2000 thread lubricant contains solid particles that are larger than the solid particles in API 5A2 compound. Possibly the large particles prevented tight thread contact necessary for gas leak tightness. The BOL 2000 lubricant may have caused or at least contributed to the yielding of the pin end during makeup. Pin inward deformation was found in some pins subsequent to testing and breakout. Excessive yielding of the pin or box will contribute to poor thread contact and leakage. The connections were made up to full or near full shoulder contact. This causes the end of the pin to be stressed near the yield strength. This along with the interference caused by the thread compound may cause excessive pin hoop stresses and yielding which in turn gives relatively loose thread contact. This behavior is present when repeated makeup and breakout occurs
Daploeuros Watts 2011
No full textDaploeuros Watts, 2011 Diagnosis. Length 6–11mm. Eyes small, distance from subgenal ridge to bottom of eye a little more than diameter of eye, subantennal groove deep, with supraantennal ridge separating groove from eye, subantennal groove deep, with supraantennal ridge separating groove from eye, subgenal ridge without buttonhole; antenna without enlarged scape, antennomeres 2 & 3 not reduced; labial palpi straight (sensu Watts & Zwick 2019); mandible with one strong tooth, molar without small spines; pronotum transverse, anterolateral angles strongly produced forward; pronotal process broad at apex, corresponding notch in mesoventrite well marked; mesoventral process about twice as wide as long; mesepisternum rugose. Penis moderately elongate, trigonium bilobed, tegmen without styli (Figs 60–62 in Watts 2011). Female micropterous; ventrite 4 with a row of long setae near posterior edge; gonocoxites elongate, moderately sclerotized, gonostyli moderately long, apical; prehensor well developed (Fig. 33 in Watts 2011, Ruta 2020). Larvae not known. Included species. Daploeuros lamingtonensis Watts, 2011; D. reichertae Ruta, 2020; D. spencei (Armstrong, 1953); D. hadrostiktos Watts, 2011.Published as part of Watts, C. H. S., Bradford, T. M. & Cooper, S. J. B., 2021, A new genus, Perplexacara, and new generic placements of species of Australian marsh beetles (Coleoptera: Scirtidae) based on morphology and molecular genetic data, pp. 539-548 in Zootaxa 4927 (4) on page 542, DOI: 10.11646/zootaxa.4927.4.4, http://zenodo.org/record/454310
Dasyscyphon Watts 2011
No full textDasyscyphon Watts, 2011 Diagnosis. Length 3–5mm. Legs stout. Eyes small, head recumbent, distance from subgenal ridge to bottom of eye a little more than diameter of eye, subantennal groove deep, with supraantennal ridge separating groove from eye, antenna without enlarged scape, antennomeres 2 and 3 not reduced; labial palpi straight (sensu Watts & Zwick (2019)) or nearly so (in Dasyscyphon tasmanicus); mandible with one strong tooth, molar without small spines; pronotum transverse, anterolateral angles weakly projecting forward; elytral punctures much larger than those on pronotum; pronotal process broad at apex, corresponding notch in mesoventrite well marked; mesoventral process about twice as wide as long; mesepisternum rugose/punctate. Penis stout, simple; trigonium finger-like, as long as parameroids; tegmen without styli (Figs 63, 64 in Watts 2011). Female winged, ventrite 4 without transverse row of long setae; gonocoxites thin, moderately sclerotised, gonostyli thin, very short, apical; prehensor well developed (Figs 43, 44 in Watts (2011). Larvae not known. Included species. Dasyscyphon hadrostiktos Watts; D. victoriaensis Watts.Published as part of Watts, C. H. S., Bradford, T. M. & Cooper, S. J. B., 2021, A new genus, Perplexacara, and new generic placements of species of Australian marsh beetles (Coleoptera: Scirtidae) based on morphology and molecular genetic data, pp. 539-548 in Zootaxa 4927 (4) on page 542, DOI: 10.11646/zootaxa.4927.4.4, http://zenodo.org/record/454310
Early lowering of LDL-C is a more cost-effective strategy than lowering LDL-C later in life: a cost-effectiveness analysis using Mendelian Randomisation
No full textPreventive Cardiology - Risk Factors and Prevention, EpidemiologyAbstract not availableJ. Morton, C. Marquina, M. Lloyd, G.F. Watts, S. Zoungas, D. Liew, Z. Adem
Effects of thread features in osseo-integrated titanium implants using a statistics-based finite element method
No full textObjective
To investigate the influence of implant design factors in terms of bone integrity and implant stability.
Materials and methods
A 3D parametric CAD model was developed. Then, once domain settings and boundary conditions were defined, a 3D FEM model was created. To simulate the physical interaction at the bone–implant interface, identity pairs were introduced. After generating different design scenarios with a DOE approach, the most significant design factors were obtained.
Results
This study showed that the geometry of the screw thread highly influenced the implant stability. In particular the degree of bone damage became minimal when adopting 0.40 mm for the thread width and 0.05 mm for the thickness.
Significance
Thread width and thickness play a crucial role to reduce induced stresses and damage in bone. Considering these preliminary results, future improvements should focus on investigating also two-factor and higher interactions to better understand the implant loading mechanism
AXIOMATICALLY SOUND POVERTY MEASUREMENT WITH SCARCE DATA AND PRICE DISPERSION
No full textWe derive a parametric formula of the Watts' poverty index for the bivariate lognormal distribution of price indices and nominal living standards. This enables us to analyze the contributions of price and nominal living standard distributions to poverty, to estimate poverty when only means and variances are known. We also derive a statistical inference framework. Using data from peasants in Rwanda in four quarters, we show that poverty estimates based on scarce information are generally not significantly different from nonparametric estimates based on full survey information.Measurement and analysis of poverty, Income distribution, Personal income distribution.
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Letter from C. D. Dawson, Tusayan Copper Mining and Smelting, to Carl Hayden
No full textLetter from C. D. Dawson to Carl Hayden urging him to consider the rights of miners and farmers when drawing up the boundaries for the proposed park
Mechanical behaviour of post-restored upper canine teeth: A 3D FE analysis
No full textObjectives. The aim was to evaluate the stress distribution, comparing an anterior sound tooth with post-endodontic restored teeth under mechanical loading.
Methods. A three-dimensional finite element analysis was performed based on micro-CT scan images of a maxillary canine. Twelve models with different crown properties and post-configurations were simulated. The model of the maxillary sound canine was also created and investigated. A load of 50 N was applied at a 63◦ angle with respect to the longitudinal axis of the tooth on the palatal surface of the crown. Principal stresses were registered. Numerical FEA results were statistically analyzed to show the influence of post shape and crown materials.
Results. All analyzed models (M1–M12) exhibited a high stress gradient, due to different material stiffnesses present at the various interfaces. The most uniform mechanical behavior of the investigated models, very similar to sound tooth, was the combination of a composite crown and a cylindrical or conical fiber-glass post.
Significance. The results of this study facilitate informed clinical choice between possible material combinations in restorative procedures of endodontically treated anterior teeth
Numerical fatigue 3D-FE modelling of indirect composite-restored posterior teeth
No full textObjective. In restored teeth, stresses at the tooth–restoration interface during masticatory processes may fracture the teeth or the restoration and cracks may grow and propagate. The aim was to apply numerical methodologies to simulate the behavior of a restored tooth and to evaluate fatigue lifetimes before crack failure.
Materials and methods. Using a CAD–FEM procedure and fatigue mechanic laws, the fatigue damage of a restored molar was numerically estimated. Tessellated surfaces of enamel and dentin were extracted by applying segmentation and classification algorithms, to sets of 2D image data. A user-friendly GUI, which enables selection and visualization of 3D tessellated surfaces,was developed in a MatLab® environment. The tooth-boundary surfaces of enamel and dentin were then created by sweeping operations through cross-sections. A class II MOD cavity preparation was then added into the 3D model and tetrahedral mesh elements were generated. Fatigue simulation was performed by combining a preliminary static FEA simulation with classical fatigue mechanical laws.
Results. Regions with the shortest fatigue-life were located around the fillets of the class II MOD cavity, where the static stress was highest.
Significance. The described method can be successfully adopted to generate detailed 3D-FE models of molar teeth, with different cavities and restorative materials. This method could be quickly implemented for other dental or biomechanical applications
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