Structural analysis of a bolted joint concept for the space shuttle's solid rocket motor casing

The Space Shuttle Challenger accident is thought to have been caused by the failure of one of the tang-clevis joints joining together the casing segments of the Solid Rocket Motors (SRM). Excessive displacement between the tang and clevis, possibly unseating the O-ring seals, may have initiated the resulting accident. An effort was made at NASA Langley Research Center to design an alternative concept for mating the casing segments. A bolted flange joint concept was designed and analyzed to determine if the concept would effectively maintain a seal while minimizing joint weight and controlling stress levels. It is shown that under the loading conditions analyzed the seal area of the joint remains seated. The only potential stress problem is a stress concentration in the flange at the edge of the bolt hole, which is highly localized. While heavier than the existing joint, this concept does have some advantages making the bolted joint an attractive alternative

Finite Element Analysis of a NASA National Transonic Facility Wind Tunnel Balance

This paper presents the results of finite element analyses and correlation studies performed on a NASA National Transonic Facility (NTF) Wind Tunnel balance. In the past NASA has relied primarily on classical hand analyses, coupled with relatively large safety factors, for predicting maximum stresses in wind tunnel balances. Now, with the significant advancements in computer technology and sophistication of general purpose analysis codes, it is more reasonable to pursue finite element analyses of these balances. The correlation studies of the present analyses show very good agreement between the analyses and data measured with strain gages and therefore the studies give higher confidence for using finite element analyses to analyze and optimize balance designs in the future

Perceptions and Reactions to Tornado Warning Polygons: Would a Gradient Polygon Be Useful?

To better understand interpretations of National Weather tornado warning polygons, 145 participants were shown 22 hypothetical scenarios in one of four displays deterministic polygon, deterministic polygon + radar image, gradient polygon, and gradient polygon + radar image. Participants judged each numerical strike probability (ps ) and reported the likelihood of taking seven different response actions. The deterministic polygon display produced ps that were highest at the centroid and declined in all directions from there. The deterministic polygon + radar display, the gradient polygon display, and the gradient polygon + radar display produced ps that were high at the centroid and also at its edge nearest the tornadic storm cell. Overall, ps values were negatively related to resuming normal activities, but positively correlated with expectations of resuming normal activities, seeking information from social sources, seeking shelter, and evacuating by car. These results replicate the finding that participants make more appropriate ps judgments when polygons are presented in their natural context of radar images than when the polygons are presented in isolation and that gradient displays appear to provide no appreciable benefit. The fact that ps judgments had moderately positive correlations with both sheltering (a generally appropriate response) and evacuation (a generally inappropriate response) provides experimental confirmation that people threatened by actual tornadoes are conflicted about which protective action to take

Perceptions and Expected Immediate Reactions to Severe Storm Displays

The National Weather Service has adopted warning polygons that more specifically indicate the risk area than its previous county-wide warnings. However, these polygons are not defined in terms of numerical strike probabilities (ps). To better understand people’s interpretations of warning polygons, 167 participants were shown 23 hypothetical scenarios in one of three information conditions—polygon-only (Condition A), polygon + tornadic storm cell (Condition B), and polygon + tornadic storm cell + flanking nontornadic storm cells (Condition C). Participants judged each polygon’s ps and reported the likelihood of taking nine different response actions. The polygon-only condition replicated the results of previous studies; ps was highest at the polygon’s centroid and declined in all directions from there. The two conditions displaying storm cells differed from the polygon-only condition only in having ps just as high at the polygon’s edge nearest the storm cell as at its centroid. Overall, ps values were positively correlated with expectations of continuing normal activities, seeking information from social sources, seeking shelter, and evacuating by car. These results indicate that participants make more appropriate ps judgments when polygons are presented in their natural context of radar displays than when they are presented in isolation. However, the fact that ps judgments had moderately positive correlations with both sheltering (a generally appropriate response) and evacuation (a generally inappropriate response) suggests that experiment participants experience the same ambivalence about these two protective actions as people threatened by actual tornadoes

Immediate Behavioral Response to the June 17, 2013 Flash Floods in Uttarakhand, North India

The 2013 Uttarakhand flash flood was such a surprise for those at risk that the predominant source of information for their risk was environmental cues and, secondarily, peer warnings rather than official warnings. Of those who received warnings, few received information other than the identity of the flood threat. A survey of 316 survivors found that most people\u27s first response was to immediately evacuate but some stayed to receive additional information, confirm their warnings, or engage in evacuation preparations. Unfortunately, engaging in these milling behaviors necessarily delayed their final evacuations. Mediation analysis revealed that psychological reactions mediated the relationship between information sources and behavioral responses. Further analyses revealed that immediate evacuation and evacuation delay were both predicted best by information search and positive affect, but correlation analyses indicated that a number of other models were also plausible. Final evacuation was best predicted by immediate evacuation and, to a significantly lesser extent, household together. Overall, results suggest that the Protective Action Decision Model (PADM) should be considered a useful framework for examining household responses to flash floods in developing countries like India. It supports the conclusion that a household\u27s first warning source is a function of two distinct detection and dis- semination systems within a community—an official system and an informal system. However, it fails to capture what pre-impact emergency preparedness entails for rapid onset events in a developing country context. Further research is needed to determine the relative importance of situational and cultural characteristics in producing these observed differences

Variable Control of DNA Nanostructures

Structural DNA nanotechnology is a promising approach for the fabrication of precise nanostructures with potential applications in drug delivery, disease detection, and templating or active assembly of nanoscale components. Current research has largely focused on static DNA nanostructures. To expand functional scope, the Nanoengineering and Biodesign Laboratory (NBL) is using a technique called DNA origami to develop nanoscale machinery with designed mechanical motion and establishing methods to control their behavior. This work focuses on controlling the dynamic behavior of DNA nanohinges by changing ionic conditions in solution. We modify the hinge design by adding additional single-stranded DNA overhangs on both arms that can close the hinge in the presence of a desired solution. Results consistently showed that hinges with complementary DNA overhangs closed more readily as solution ion concentration increased, with sensitivity to hinge stiffness, length of overhangs, number of overhang connections, and location of overhangs. We also designed and fabricated an oscillator hinge for the incorporation of two-way actuation mechanisms. These findings suggest that dynamic DNA nanostructures can be designed to interact predictably with a given ionic environment based on modified structural properties. Future experiments will include the further study of overhang spatial distribution and expansion of hinge actuation studies to real-time fluorescence trials. The oscillator hinge will be used for possible theranostic applications as well as for signal propagation through polymerized chains.The Undergraduate Honors Committee in the College of EngineeringA one-year embargo was granted for this item.Academic Major: Chemical Engineerin

Predicting Residents’ Responses to the May 1-4, 2010, Boston Water Contamination Incident

This study examined 110 local residents’ warning sources, warning channels, warning receipt times, message content, risk perception, and behavioral responses (warning confirmation, and consumption of untreated tap water, boiled water, bottled water, and personally chlorinated water) during the May 1-4 2010 Boston water contamination incident. Most residents received warnings from peers and news media and these warnings mentioned 2.35 of five recommended elements of a warning message—most commonly the threat and the recommended protective action. TV was the most frequent channel for additional information, partly because it was the most frequent channel of routine information, but the Internet was also a common channel for additional information. Consumption of untreated tap water declined, consumption of personally chlorinated water remained negligible, and consumption of boiled water and bottled water increased during the incident. Warning receipt from an authority increased consumption of boiled water, whereas receipt of a less specific warning tended to increase consumption of bottled water. The distribution of warning times followed a logistic (S-shaped) distribution, with the largest increase taking place during prime TV news time (4-6pm). These results call attention to the need to increase the number of comprehensive warning response studies on rapid onset disasters to provide the basis for developing a comprehensive theory that can explain similarities and differences in responses to the full range of environmental hazards

Toward a Multi-stage Model of Hurricane Evacuation Decision: An Empirical Study of Hurricanes Katrina and Rita

This study extended previous research by testing the Protective Action Decision Model (PADM) on hurricane evacuation decisions during Hurricanes Katrina and Rita. An examination of this mediation model shows that a household’s evacuation decision, as predicted, is determined most directly by expected wind impacts and expected evacuation impediments. In turn, expected wind impacts and expected hydrological impacts are primarily determined by expected storm threat and expected rapid onset. Finally, expected storm threat, expected rapid onset, and expected evacuation impediments are determined by households’ personal characteristics, their reception of hurricane information, and their observations of social and environmental cues. These results are generally consistent with the PADM and reinforce the importance of testing multi-stage multi-equation models of hurricane evacuation

Does Updating Natural Hazard Maps to Reflect Best Practices Increase Viewer Comprehension of Risk?

In this study, we examine whether updating an interactive hazard map using recommendations from the literature improves user map comprehension. Analyses of experimental data collected from 75 university students revealed that map comprehension scores were not significantly better for those who viewed a “best practices” map compared to those who viewed an existing version. This may be because the existing map was itself better than most other interactive maps. Additionally, we found map comprehension levels to have significant positive relationships with objective tests, but not self-reported measures of spatial ability. Moreover, self-reported spatial ability had statistically significant, but only moderately strong, correlations with objective tests. These results indicate that spatial ability should be measured objectively rather than through self-reported methods in research on map comprehension. Further research is needed to examine the cognitive processes involved in hazard map comprehension, especially using a broader range of map characteristics and population segments with more diverse cognitive abilities

Test and Analysis of a Hyper-X Carbon-Carbon Leading Edge Chine

During parts production for the X43A Mach 10 hypersonic vehicle nondestructive evaluation (NDE) of a leading edge chine detected on imbedded delamination near the lower surface of the part. An ultimate proof test was conducted to verify the ultimate strength of this leading edge chine part. The ultimate proof test setup used a pressure bladder design to impose a uniform distributed pressure field over the bi-planar surface of the chine test article. A detailed description of the chine test article and experimental test setup is presented. Analysis results from a linear status model of the test article are also presented and discussed. Post-test inspection of the specimen revealed no visible failures or areas of delamination