Search Results for tolerance

This article addresses the issue of the implementation of composite damage tolerance requirements as it relates to military aircraft. It presents a brief introduction on the durability impact threat, damage tolerance impact threat, and other damage tolerance damage threats. The article summarizes damage tolerance criteria and durability criteria for military aircraft. It discusses the damage tolerance design philosophy for metallic structures and composite structures of the aircraft. The article describes the implementation of a damage tolerance analysis methodology in terms of the mechanics based model, the regression algorithm, and the semi-empirical analysis.

This article describes two analysis methods that are used to determine the life of aircrafts: fatigue life and fracture mechanics methods. The life limiting factors that control the durability of the aircraft are also discussed. The article provides an overview of the various approaches to corrosion identification and prevention. These include safe-life, fail-safe, and damage tolerance approaches. The article discusses their application to the process of extending the life of aircraft structural components.

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.

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.

Damage tolerance analysis consists of three parts such as the calculation of the residual strength diagram to obtain the permissible crack size, calculation of the crack growth curve, and calculation of the inspection interval. This article discusses the aspects of obtaining material property data and geometry factors to analyze any fracture or crack growth problem. It describes the integration of crack growth rates in terms of constant-amplitude loading and cycle-by-cycle counting with variable-amplitude loading. The article concludes with information on the classification of sources of error in damage tolerance analysis.

The objective of dimensional management is to create a design and process that absorbs as much variation as possible without affecting the function of the product. This article describes the steps followed by the dimensional management process. These include defining product dimensional requirements, determining process and product requirements, ensuring accurate documentation, developing a measurement plan that validates product requirements, establishing manufacturing capabilities versus design intent, and establishing production-to-design feedback loop. The article discusses the simulation model in terms of a functional feature product model, component part variation, assembly method variation, measurement schemes, and assembly sequences.

The design of forging operations; consisting of dies, fixturing, and parts; requires a consistent and unambiguous method for representing critical dimensions and tolerances. This article presents a dimensioning process, based on tooling points and datum planes, with the potential to simplify geometries while minimizing tolerance stack-ups. The method also facilitates inspection liaison between vendors and users because fixturing is easy to duplicate and tooling points are consistent from forging to finish-machined part. The article focuses on the most common dimensional tolerances for closed-die forgings, including finish allowances for machining, length and width tolerances, die-wear tolerance, match tolerances, die-closure or thickness tolerances, straightness and flatness tolerances, radii tolerances, flash-extension tolerances, and surface tolerances. It also contains a convenient summary in the form of a checklist.

Alloy 2624 was developed by Alcoa as a plate product to replace alloy 2024 and 2324 in applications requiring moderate or high strength and the highest levels of damage tolerance. This datasheet provides information on composition limits, processing effects on physical and mechanical properties, and applications of this alloy. Figures provide comparisons of plane stress R-curves of 2624 with 2024-T351 and 2324-T39 and fatigue crack growth resistance of 2624 with 2024-T351 and 2324-T39.