Search Results for structural safety

Damage tolerance is a philosophy used for maintaining the structural safety of commercial transport aircrafts. This article describes the structural evaluations necessary to comply with the regulations contained in the Federal Air worthiness Requirements 25.571 whose guidance is given in Advisory Circular 25.571-1A from the Federal Aviation Administration. It provides an overview of the historical evolution of damage tolerance philosophy and presents a discussion of the design philosophies and a summary of the evaluation tasks for damage tolerance certification.

This article discusses the safety issues associated with the design and operation of thermal spray booths and spray box structures and the equipment or systems required for operating thermal spray processes. It describes the design elements necessary to mitigate sound, dust and fume, ultraviolet light, and mechanical hazards. The means selected for safeguarding personnel must be based on a formal risk assessment that meets ANSI/RIA standards. The safeguards include sensing devices, barriers, awareness signals, procedures, and training. It also provides guidelines that are intended to increase the safety awareness and the use of safety practices for gas and liquid piping and electrical equipment within thermal spray installations.

The selection of materials for welded construction applications involves a number of considerations, including design codes and specifications. Mobile structures have quite different materials requirements for weight, durability, and safety than stationary structures, which are built to last for many years. This article provides an overview of the service conditions. It offers guidance for material selection applications, including bridges and buildings, pressure vessels and piping, shipbuilding and offshore structures, aerospace systems, machinery and equipment, automobiles, railroad systems, and sheet metal. Material properties and welding processes that may be significant in meeting design goals are also described.

Painting is a generic term for the application of a thin organic coating to the surface of a material for decorative, protective, or functional purposes. This article provides a detailed account of the types and selection factors of paints and the various application methods, including conventional air atomized, airless, and electrostatic spray; roller coating; dip coating; flow coating; curtain coating; tumble coating; electrocoating; and powder coating. Surface preparation methods and prepaint treatments for coating systems are also discussed. The article includes information on quality control procedures, causes of paint film defects, cost calculation, and safety and environmental precautions. The composition and characteristics of organic coatings, coating system selection factors, the types of paints for structural steel, and the applications of paint on structural steel are also reviewed.

Soldering technology has been used in applications ranging from the packaging of integrated circuit chips to the fabrication of industrial heat exchangers and consequently in structural or electronic applications. This article provides information on various soldering parameters, including types of solder alloy in terms of selection process; selection of substrate base material; flux selection based on adequate wettability by the solder; solder joint assembly; combined substrate, solder, and flux properties; and manufacturing procedures. Each of these parameters is explored using examples of both structural and electronic applications. The article concludes with a discussion on the environmental, safety, and health issues to be considered during soldering.

Fatigue failure is a critical performance metric for additively manufactured (AM) metal parts, especially those intended for safety-critical structural applications (i.e., applications where part failure causes system failure and injury to users). This article discusses some of the common defects that occur in laser powder bed fusion (L-PBF) components, mitigation strategies, and their impact on fatigue failure. It summarizes the fatigue properties of three commonly studied structural alloys, namely aluminum alloy, titanium alloy, and nickel-base superalloy.

Beryllium possesses an unusual combination of physical and mechanical properties, suiting it for specialized applications where its relatively high cost can be justified. It has very low density, a moderately high melting point, high elastic modulus, and good electrical and thermal conductivity. The article describes structural, instrument, and optical grade beryllium and the corresponding compositional ranges. It also discusses processing and product forms as well as factors affecting corrosion resistance. The article concludes with a short note on health and safety considerations when handling beryllium.

This article discusses the advantages of polymer matrix composite for automotive application in terms of design drivers, noise, vibration, harshness efficiency, process materials property constraints, safety and reliability, design optimization, structural and appearance requirements, recyclability, and processability. It describes the properties of high-volume composites used in automotive industries. The article provides a discussion on state-of-the-art and developing technologies in automotive field.

Vat polymerization (VP) is an additive manufacturing (AM), or three-dimensional (3-D) printing process in which 3-D objects are produced by hardening a liquid polymer into the desired shape. With the introduction of new materials and improvements in material properties, VP offers a good alternative for AM for low-volume production. This overview of the VP process begins with an introduction to two main processes of VP, namely stereolithography apparatus and digital light processing, and then moves on to discuss the characteristics of the feedstocks used as well as their selection criteria. The article then covers safety issues associated with feedstock handling and the manufacturing constraints related to part orientation and design, providing some key tips for VP support structures. This is followed by a discussion on postprocessing/finishing of VP parts. A brief concluding section considers some special topics related to AM process.

This article describes the historical background, uncertainties in structural parameters, classifications, and application areas of probabilistic analysis. It provides a discussion on the basic definition of random variables, some common distribution functions used in engineering, selection of a probability distribution, the failure model definition, and a definition of the probability of failure. The article also explains the solution techniques for special cases and general solution techniques, such as first-second-order reliability methods, the advanced mean value method, the response surface method, and Monte Carlo sampling. A brief introduction to importance sampling, time-variant reliability, system reliability, and risk analysis and target reliabilities is also provided. The article examines the various application problems for which probabilistic analysis is an essential element. Examples of the use of probabilistic analysis are presented. The article concludes with an overview of some of the commercially available software programs for performing probabilistic analysis.

Fracture control is a systematic process to prevent fracture during operation that depends on the criticality of the component, the economic consequences of the structures being out of service, and the damage that would be caused by a fracture failure. This article describes the key principles of fracture control and reviews the concepts of damage tolerance analysis. It further presents practical guidelines to obtain useful and reasonable answers from damage tolerance analysis. The article concludes with information on fracture mechanics and fatigue design.

The inclusion of damage tolerance design and a systematic review of design procedures allow the U.S. Air Force to design, manufacture, and maintain systems that are structurally safe and economically prudent. After a brief introduction of fracture mechanics, this article describes the particular aspects that relate to damage tolerance in aircraft design. It discusses the use of fracture mechanics as a method of predicting failure, understanding failure mechanisms, and suggesting inspection methods to protect against failure in pressure vessels. Various programs of U.S. Air Force to design aircraft structure, namely, airframe structural integrity programs, engine structural integrity program, and mechanical subsystems structural integrity program are also discussed.

There are two parts to deal with uncertainty in fatigue design: determining the distributions of possible values for all uncertain inputs and calculating the probability of failure due to all the uncertain inputs. This article discusses the sources of uncertainty in a fatigue analysis, such as the material properties, distribution of applied stress levels within a given environment, environments or loading intensities, and modeling or prediction. It presents a probabilistic approach for analyzing the uncertainties and determining the level of reliability (probability of failure).

Life assessment of structural components is used to avoid catastrophic failures and to maintain safe and reliable functioning of equipment. The failure investigator's input is essential for the meaningful life assessment of structural components. This article provides an overview of the structural design process, the failure analysis process, the failure investigator's role, and how failure analysis of structural components integrates into the determination of remaining life, fitness-for-service, and other life assessment concerns. The topics discussed include industry perspectives on failure and life assessment of components, structural design philosophies, the role of the failure analyst in life assessment, and the role of nondestructive inspection. They also cover fatigue life assessment, elevated-temperature life assessment, fitness-for-service life assessment, brittle fracture assessments, corrosion assessments, and blast, fire, and heat damage assessments.

This article discusses the need, purposes, and objectives of codes and standards. It describes several types of codes, such as safety and trade codes, and the different types of standards, namely, industry consensus standards, product definition standards, and commercial standards. The article provides information on organizations that prepare codes and standards. It tabulates sponsoring organizations for the standards published by the American National Standards Institute and concludes with a discussion on a designer's responsibilities.

High-frequency (HF) welding is a welding process in which the heat source used to melt the joining surfaces is obtained from HF alternating current (ac) resistance heating. This article discusses the advantages and disadvantages and applications of HF welding. It describes the equipment used for HF welding and the safety aspects to be considered during welding. The article concludes with a discussion on inspection and quality control.

This article provides a background to the biological evaluation of medical devices. It discusses what the ISO 10993 standards require for polymeric biomaterials and presents examples of qualitative and quantitative tests that can be used to satisfy these requirements. The article describes infrared (IR) and thermal analyses that are used extensively to fingerprint polymeric materials. It also presents a discussion on the chemical characterization and risk assessment of extracts. Background information on risk assessments of extracts is also included. The four basic steps that are commonly used in the risk assessment process are discussed. These include hazard identification, dose-response assessment, and exposure assessment, and risk characterization.

Maintainability is a function of the durability, damage tolerance, and repairability of a structure. This article discusses the configurations of composite structures, such as sandwich, stiffened-skin, and monolithic structures, used in commercial aircraft composites. It describes the considerations for maintainability of the composite structures during the conceptual design phase. Sources of the defects and damage, such as manufacturing defects and in-service defects, are reviewed. The article describes the nondestructive inspection methods that are used in the repair of composite structures to locate damage, characterize the extent of damage, and ensure post-repair quality. It lists suggestions that can be used as design guidelines for adhesive bonding, general composite structure, sandwich structure, material selection, and lightning-strike protection. The article also provides the basic considerations for personnel, facilities, and equipment during maintenance.

This article describes common design criteria and identifies the design considerations that have a significant effect on the end product. The design criteria include cost, size, mechanical properties, repeatability and precision of parts, damage tolerance and durability, and environmental constraints.