Analysis of Tiplock Phenomenon in Extension Ladders

2004 ◽  
Author(s):  
John S. Morse ◽  
C. Russ Rasnic
Keyword(s):  
Geometric Analysis ◽  
Mathematical Expression ◽  
Physical Measurement ◽  
Lock Mode ◽  
Serious Injury ◽  
Tip Radius ◽  
The U.S

Extension ladder accidents injure thousands of people each year in the U.S. One cause of these accidents is false lock of the flylocks. Flylocks are the devices that support the upper or fly section of an extended ladder. False locked flylocks are not fully locked, but nevertheless support a load. False lock is not stable and may release under disturbance of the ladder, e.g. from climbing. False lock modes include tiplock, flipperlock, and camlock. If a false lock releases the ladder will telescope, and may cause serious injury. One false lock mode is tiplock, where the tip of the flylock is resting on the rung of the ladder in a metastable position. The tiplock may be held in place by mechanical locking, or by friction between the tip and the rung. Tiplock may occur when the ladder is being extended and the fly section is not raised enough to fully engage the flylocks. Ladder labels usually instruct “Securely engage ladder locks before climbing,” but typically do not instuct a user how to do this. Ladder users employ various methods to securely engage flylocks. These methods do not always prevent false lock. No gravity or spring actuated flylock design is known which will completely eliminate tiplock, but various designs have different ranges of fly section travel over which tiplock can occur (tiplock “window”). A mathematical expression defines the conditions under which friction tiplock can occur. Two methods of evaluating the tiplock window are discussed: geometric analysis and physical measurement. Tiplock propensity during random ladder extension is calculated. A geometric analysis is made of two flylocks with different tip radii. The flylock with the smaller tip radius is observed to have a smaller tiplock window.

The Application of Fracture for Middle Carbon Steel in Extra-Low Cycle Rotating Bending Fatigue Loading

2004 ◽  
Vol 261-263 ◽  
pp. 1153-1158 ◽  
Author(s):  
You Tang Li ◽  
Ping Ma ◽  
Chang Feng Yan ◽  
Fu Yuan Lang
Keyword(s):  
Carbon Steel ◽  
Fatigue Fracture ◽  
Mathematical Expression ◽  
Fatigue Loading ◽  
Bending Fatigue ◽  
Cycle Times ◽  
Rotating Bending Fatigue ◽  
Rotating Bending ◽  
Tip Radius ◽  
Made In

Safety designs and fracture designs are the two important fields of crack theory. The fracture problems of middle carbon steel under extra-low cycle rotating bending fatigue loading are studied in this paper. The experiments have been made in special rotating bending fatigue fracture machine designed by us. Several problems, the relations of the cycle times of fracture and the strain amplitude near notch tip to the deflection, the effects of depth and tip radius of notch to the cycle times of fracture, are discussed through the experiments. The mathematical expression of fracture toughness to the cycle times of fracture is obtained. The suitable parameters of rotating bending fatigue fracture model for middle-carbon steel in extra-low cycle times has been proposed.

Indentation Method to Measure Plating Ductility

1990 ◽  
Vol 112 (3) ◽  
pp. 272-277 ◽  
Author(s):  
P. A. Engel ◽  
D. L. Questad
Keyword(s):  
Cone Angle ◽  
Geometric Analysis ◽  
Radial Strain ◽  
Indentation Test ◽  
Substrate Material ◽  
Ultimate Strain ◽  
Tangential Displacement ◽  
Indentation Method ◽  
X Ray ◽  
Tip Radius

The ductility of a plating is an important measure of its durability. In the present paper an indentation test for thin platings is introduced. The test is based on the fact that tensile radial strains arising at the rim of the indentation crater tend to cause cracks in a material of insufficient ductility. By a quantitative knowledge of the radial strain the ductility – i.e., ultimate strain – of the material can be determined. We use a simple geometric analysis which assumes no tangential displacement in the contact area to determine the “average radial strain” across the indentation. In the experiments sharp conical indenters (typically having a 60 degree cone angle with a 0.025 mm (0.001 in.) tip radius) are used, and the plastically deformed crater is checked by electron microscopy (SEM) for cracks. If a crack is detected, its depth is further checked by an attendant X-ray procedure (EDX) for the presence of the underlying substrate material. If a “through-crack” is found, then the ductility of the plating has been exceeded; i.e., the ductility will be equated with the strain value measured for the last indenter loading not involving a crack.

scholarly journals Fuel Tank Crashworthiness: Loading Scenarios

2011 ◽  
Author(s):  
Karina Jacobsen
Keyword(s):  
Oblique Impact ◽  
Fuel Tank ◽  
Passenger Rail ◽  
Equipment Safety ◽  
Impact Location ◽  
Fuel Tanks ◽  
Serious Injury ◽  
Conducting Research ◽  
Railroad System ◽  
The U.S

The Federal Railroad Administration’s Office of Research and Development is conducting research into fuel tank crashworthiness. The breaching of fuel tanks during passenger rail collisions and derailments increases the potential of serious injury and fatality due to fire. This paper identifies and describes common collision loading scenarios for locomotive fuel tanks on the U.S. general railroad system. Developing scenarios that characterize this situation is the first step in crashworthiness research methodology for improving rail equipment safety. A survey of accidents within the U.S. between 1995 and present was used to identify fuel tank impact scenarios as follows: impact with adjacent railcar component; oblique impact with another railcar; rollover leading to impact with another railcar; derailment or rollover leading to grounding; and impact with rail. These collision scenarios are further categorized by the types of collision modes experienced by the fuel tank, i.e. impact type and impact location. These loading conditions establish targets for evaluating current levels of fuel tank integrity and potentially developing improved strategies for enhancing fuel tank integrity.

Tooth Root Strength of Spur and Helical Gears Manufactured With Gear-Shaper Cutters

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Andrzej Kawalec ◽  
Jerzy Wiktor
Keyword(s):  
Geometric Analysis ◽  
Strength Analysis ◽  
Tooth Root ◽  
Element Analysis ◽  
Iso Standard ◽  
Transmission Design ◽  
Root Strength ◽  
Gear Manufacturing ◽  
Tip Radius ◽  
Root Stress

At the beginning of gear transmission design, mainly simplified methods of gear strength analysis based on ISO or AGMA standards are used. However, they allow for calculation of approximate and sometimes biased stresses. Moreover, ISO standard is generally focused on using racks for gear manufacturing. A method proposed in this paper allows for computation of the parameters of critical section, strength coefficients YF, YS, and tooth root stress σF according to the procedure from ISO standard also in the case of machining gears with gear type tools. The proposed improvement of ISO standard leads to replacement of real gear tool with rack with substitute tip radius ρa0*. The developed method maintains basic assumptions and advantages of ISO standard, including its simplicity. Simultaneously, it allows for computing the maximum tooth root stresses σF: (i) very close to results of accurate geometric analysis and finite element analysis, and (ii) much closer, compared to conventional ISO procedure, to results obtained using AGMA standard.

Historical Introduction

1977 ◽  
Vol 35 ◽  
pp. 2-5
Author(s):  
R. D. Heidenreich
Keyword(s):  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
50Th Anniversary ◽  
Secondary Emission ◽  
Wave Nature ◽  
Nobel Prize In Physics ◽  
Primary Electrons ◽  
The U.S ◽  
Mutual Agreement

This program has been organized by the EMSA to commensurate the 50th anniversary of the experimental verification of the wave nature of the electron. Davisson and Germer in the U.S. and Thomson and Reid in Britian accomplished this at about the same time. Their findings were published in Nature in 1927 by mutual agreement since their independent efforts had led to the same conclusion at about the same time. In 1937 Davisson and Thomson shared the Nobel Prize in physics for demonstrating the wave nature of the electron deduced in 1924 by Louis de Broglie.The Davisson experiments (1921-1927) were concerned with the angular distribution of secondary electron emission from nickel surfaces produced by 150 volt primary electrons. The motivation was the effect of secondary emission on the characteristics of vacuum tubes but significant deviations from the results expected for a corpuscular electron led to a diffraction interpretation suggested by Elasser in 1925.

Variations in Surface Textures of Quartz Sand using Electron Microscopy

1970 ◽  
Vol 28 ◽  
pp. 494-495
Author(s):  
Eugene J. Amaral
Keyword(s):  
Electron Microscopy ◽  
Glass Industry ◽  
Glass Slide ◽  
Distilled Water ◽  
Early Paleozoic ◽  
Secondary Effects ◽  
Surface Textures ◽  
High Silica ◽  
Sand Deposit ◽  
The U.S

Examination of sand grain surfaces from early Paleozoic sandstones by electron microscopy reveals a variety of secondary effects caused by rock-forming processes after final deposition of the sand. Detailed studies were conducted on both coarse (≥0.71mm) and fine (=0.25mm) fractions of St. Peter Sandstone, a widespread sand deposit underlying much of the U.S. Central Interior and used in the glass industry because of its remarkably high silica purity.The very friable sandstone was disaggregated and sieved to obtain the two size fractions, and then cleaned by boiling in HCl to remove any iron impurities and rinsed in distilled water. The sand grains were then partially embedded by sprinkling them onto a glass slide coated with a thin tacky layer of latex. Direct platinum shadowed carbon replicas were made of the exposed sand grain surfaces, and were separated by dissolution of the silica in HF acid.

Liquid crystalline ordering of paired helical filaments in neurofibrillary tangles of Alzheimer's disease

1986 ◽  
Vol 44 ◽  
pp. 348-349
Author(s):  
D.F. Clapin ◽  
V.J.A. Montpetit
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Neurofibrillary Tangles ◽  
Liquid Crystalline ◽  
Amyloid Fibrils ◽  
Geometric Analysis ◽  
Paired Helical Filaments ◽  
Microscopic Level ◽  
Light Microscopic Level ◽  
Regular Spacing

Alzheimer's disease is characterized by the accumulation of abnormal filamentous proteins. The most important of these are amyloid fibrils and paired helical filaments (PHF). PHF are located intraneuronally forming bundles called neurofibrillary tangles. The designation of these structures as "tangles" is appropriate at the light microscopic level. However, localized domains within individual tangles appear to demonstrate a regular spacing which may indicate a liquid crystalline phase. The purpose of this paper is to present a statistical geometric analysis of PHF packing.

The Effects of Estradiol on Chronically Damaged Human Fallopian Tubes: A SEM Study

1985 ◽  
Vol 43 ◽  
pp. 648-649
Author(s):  
A. Toledo ◽  
G. Stoelk ◽  
M. Yussman ◽  
R.P. Apkarian
Keyword(s):  
Menstrual Cycle ◽  
Epithelial Cell ◽  
Secretory Cell ◽  
Estrogen Therapy ◽  
Fallopian Tubes ◽  
Cell Surfaces ◽  
Proliferative Phase ◽  
Cyclic Patterns ◽  
Sem Study ◽  
The U.S

Today it is estimated that one of every three women in the U.S. will have problems achieving pregnancy. 20-30% of these women will have some form of oviductal problems as the etiology of their infertility. Chronically damaged oviducts present problems with loss of both ciliary and microvillar epithelial cell surfaces. Estradiol is known to influence cyclic patterns in secretory cell microvilli and tubal ciliogenesis, The purpose of this study was to assess whether estrogen therapy could stimulate ciliogenesis in chronically damaged human fallopian tubes.Tissues from large hydrosalpinges were obtained from six women undergoing tuboplastic repair while in the early proliferative phase of fheir menstrual cycle. In each case the damaged tissue was rinsed in heparinized Ringers-lactate and quartered.

Antitrust: U.S. Supreme Court Affirms FTC Jurisdiction but Vacates Scope of Analysis on CDA Policy

1999 ◽  
Vol 27 (2) ◽  
pp. 197-198
Author(s):  
Joseph R. Zakhary
Keyword(s):  
Public Relations ◽  
Supreme Court ◽  
Federal Trade Commission ◽  
Ninth Circuit ◽  
Court Of Appeals ◽  
For Profit ◽  
Rule Of Reason ◽  
Antitrust Analysis ◽  
Business Financing ◽  
The U.S

In California Dental Association v. FTC, 119 S. Ct. 1604 (1999), the U.S. Supreme Court reviewed a decision by the U.S. Court of Appeals for the Ninth Circuit that a nonprofit affiliation of dentists violated section 5 of the Federal Trade Commission Act (FTCA), 15 U.S.C.A. § 45 (1998), which prohibits unfair competition. The Court examined two issues: (1) the Federal Trade Commission's (FTC) jurisdiction over the California Dental Association (CDA); and (2) the proper scope of antitrust analysis. The Court unanimously held that CDA was subject to FTC's jurisdiction, but split 5-4 in its finding that the district court's use of abbreviated rule-of-reason analysis was inappropriate.CDA is a voluntary, nonprofit association of local dental societies. It boasts approximately 19,000 members, who constitute roughly threequarters of the dentists practicing in California. Although a nonprofit, CDA includes for-profit subsidiaries that financially benefit CDA members. CDA gives its members access to insurance and business financing, and lobbies and litigates on their behalf. Members also benefit from CDA marketing and public relations campaigns.

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