Search Results for Extension ladders

The central approach of human factors engineering is the systemic application of relevant information about human characteristics and behavior to the design of human-made objects, facilities, and environments that people use. This article focuses on the elements that are considered for an acceptable level of human performance. These include the state or condition of the human being; the activity, including equipment and required tools; and the context in which the activity is performed.

Distortion failure occurs when a structure or component is deformed so that it can no longer support the load it was intended to carry. Every structure has a load limit beyond which it is considered unsafe or unreliable. Estimation of load limits is an important aspect of design and is commonly computed by classical design or limit analysis. This article discusses the common aspects of failure by distortion with suitable examples. Analysis of a distortion failure often must be thorough and rigorous to determine the root cause of failure and to specify proper corrective action. The article summarizes the general process of distortion failure analysis. It also discusses three types of distortion failures that provide useful insights into the problems of analyzing unusual mechanisms of distortion. These include elastic distortion, ratcheting, and inelastic cyclic buckling.

Distortion often is observed in the analysis of other types of failures, and consideration of the distortion can be an important part of the analysis. This article first considers that true distortion occurs when it was unexpected and in which the distortion is associated with a functional failure. Then, a more general consideration of distortion in failure analysis is introduced. Several common aspects of failure by distortion are discussed and suitable examples of distortion failures are presented for illustration. The article provides information on methods to compute load limits, errors in the specification of the material, and faulty process and their corrective measures to meet specifications. It discusses the general process of material failure analysis and special types of distortion and deformation failure.

This article discusses the three legal theories on which a products liability lawsuit is based and the issues of hazard, risk, and danger in the context of liability. It describes manufacturing and design defects of various products. The article explains a design that is analyzed from the human factors viewpoint and details the preventive measures of the defects, with examples. It presents four paramount questions relating to the probability of injury which are asked even when one executes all possible preventive measures carefully and thoroughly.

This article presents an overview of fatigue crack nucleation from the point of view of the material microstructure and its evolution during cycling. It describes the sites of microcrack nucleation at the free surfaces. The article discusses the relation of dislocation structures and surface relief and reviews the mechanisms of crack nucleation. The damage of material due to crack nucleation, the extent (in terms of the number of cycles) of the nucleation stage, and the factors influencing crack nucleation are discussed.

Field ion microscopy (FIM) can be used to study the three-dimensional structure of materials, such as metals and semiconductors, because successive atom layers can be ionized and removed from the surface by field evaporation. The ions removed from the surface by field evaporation can be analyzed chemically by coupling to the microscope a time-of-flight mass spectrometer of single-particle sensitivity, known as the atom probe (AP). This article describes the principles, sample preparation, and quantitative analysis of FIM. It also provides information on the principles, instrument design and operation, mass spectra and their interpretation, and applications of AP microanalysis.

Aluminum, the second most plentiful metallic element, is an economic competitor in various applications owing to its appearance, light weight, fabricability, physical properties, mechanical properties, and corrosion resistance. This article discusses the primary and secondary production of aluminum and classification system for cast and wrought aluminum alloys. It talks about various manufactured forms of aluminum and its alloys, which are classified into standardized products such as sheet, plate, foil, rod, bar, wire, tube, pipe, and structural forms, and engineered products such as extruded shapes, forgings, impacts, castings, stampings, powder metallurgy parts, machined parts, and metal-matrix composites. The article also reviews important fabrication characteristics in the machining, forming, forging, and joining of aluminum alloys. It concludes with a description of the major industrial applications of aluminum, including building and construction, transportation, consumer durables, electrical, machinery and equipment, containers and packaging, and other applications.

This article describes the influences of the operational environments of U.S. Navy aircraft during corrosion-control process. The most widely used materials in airframe structures and components, such as aluminum, steel, titanium, and magnesium alloy systems, are reviewed. The article provides information on the inspections steps, corrosion-control issues, and corrosion-prevention strategies for naval aircraft. It contains a table that lists typical locations of corrosion on the aircraft. The article also provides examples of aircraft corrosion damage.

This article discusses the materials of construction found in pharmaceutical production facilities. The materials discussed are different stainless steels, nickel and nickel-base alloys, titanium, zirconium, impervious graphite, fluoropolymers, and glass-lined steel. The article describes the three primary causes of failure in the manufacture of pharmaceuticals: embedded iron, failures of glass linings, and corrosion under thermal insulation.

Products liability is a legal term for the action whereby an injured party (plaintiff) seeks to recover damages for personal injury or property loss from a producer and/or seller when the plaintiff alleges that a defective product caused the injury or loss. This article provides information on the legal bases for products liability and definitions for two types of defects: manufacturing defects and design defects. It summarizes other possible defects in design as well as preventive measures.

Value analysis (VA) is a team problem-solving process to improve the value of a product from the viewpoint of a user. This article presents a comparison between VA and total quality management in materials selection and design. It discusses the key attributes, concepts, and activities of the VA. The application of value engineering in U.S. government contracts and the construction industry is reviewed. The article describes the eight phases of the VA process: preparation, information, analysis, creation, synthesis, development, presentation and report, and implementation and follow-up. It presents case studies that illustrate the materials-related aspects of the VA process.

This article discusses the advantages and disadvantages of field metallography and describes the important material characteristics and other aspects to be considered before performing any metallographic procedure. It investigates the various stages of sample preparation in the metallographic laboratory: grinding, polishing, etching, preparing a replica, and obtaining a small sample. The article also illustrates the applications of field metallography with case studies.

This article identifies the coatings applied to many substrates for both beautification and protection, and the inherent conflicts that exist between the coatings and the buildings they are designed to protect; emphasis is placed on masonry walls. It provides information on the purposes of the coatings in the commercial buildings. The article briefly describes some of the most common types of substrates found in buildings and the coatings commonly associated with each substrate. The selection of the coating system depends on the substrate and service expectations. The article addresses the primary causes of masonry coating problems and also provides a detailed discussion on the wall design considerations, moisture considerations, and coating system challenges in the masonry buildings.

Thin sections save weight and thus contribute to a more favorable strength-to-weight ratio. By requiring a smaller volume of metal, thin walls may also lower casting costs, particularly when an expensive alloy is being poured. This article discusses the design problems in thin-wall steel sand castings, thin-wall aluminum and magnesium castings, thin-wall permanent mold castings, and thin-wall investment castings, with schematic illustrations.

Any threat to personal safety should be regarded as a hazard and treated as such. This article discusses threats from several sources, such as kinematic/mechanical hazards, electrical hazards, energy hazards, human factors/ergonomic hazards, and environmental hazards. It describes hazard analysis in terms of failure modes and effects analysis, failure modes and criticality analysis, fault tree analysis, fault hazard analysis, and operating hazards analysis. The article examines fail-safe designs, such as fail-passive designs, fail-active designs, and fail-operational designs. It also provides information on various types of warnings, such as visual warning, auditory warnings, olfactory warnings, tactile warnings, and tastable warnings.

This article is an informative primer on sealants and the role they play in engineered assemblies. It discusses the physical, thermal, chemical, and electrical properties of sealant materials and the various forms in which they are applied, including liquids, pastes, and extruded tapes. It also describes classifications and types, comparing and contrasting sealants made from oil-based caulks, asphalts, coal tar resins, latex acrylic sealants, polyvinyl acetate caulks, solvent acrylics, butyl sealants, polysulfides, polyurethanes, modified silicones, anaerobics, vinyl plastisols, and polypropylenes. In addition, the article provides practical design insight, addressing application requirements, seal configurations, and joint stresses. It concludes with a brief discussion on the use of sealants in aerospace, automotive, electrical, and construction applications.

The process of transferring coating materials from the container to the surface to be coated can be accomplished in a number of ways. This article describes seven methods of coating application: brushes, rollers, and daubers; conventional air spray; high-volume low-pressure spray; airless spray; air-assisted airless spray; plural-component spray; and electrostatic spray. Factors to be considered when deciding on an application method include the size and configuration of the surfaces to be coated, the type of coating being applied, environmental regulations/restrictions, the proximity to other operations or personnel, and the recommendations of the coating manufacturer.

Dew-point corrosion occurs when gas is cooled below the saturation temperature pertinent to the concentration of condensable species contained by a gas. This article discusses dew-point corrosion problems in the susceptible areas of dry flue gas handling systems. The corrosion problems associated with the nitrate stress-corrosion cracking in heat-recovery steam generators are also discussed. The article presents general comments on the materials selection; plant operation; use of neutralizing additives; and maintenance, good housekeeping, and lagging (insulation). It concludes with information on guidance for maintaining specific sections of the plant.