This chapter familiarizes readers with the mechanisms involved in creep and how they are related to fatigue behavior. It explains that what we observe as creep deformation is the gradual displacement of atoms in the direction of an applied stress aided by diffusion, dislocation movement, and grain boundary sliding. It describes these mechanisms in qualitative terms, explaining how they are driven by thermal energy and how they can be analyzed using creep curves and deformation maps. In addition, it examines the types of damage associated with creep, presents a number of creep strain and strain rate equations, explains how to determine creep constants, and reviews the findings of several studies on cyclic loading. It also discusses the development of a novel test that measures the cyclic creep-rupture resistance of materials in tension and compression.

This chapter focuses on creep-rupture failure, or more precisely, the time required for such a failure to occur at a given stress and temperature. It begins with a review of creep-rupture phenomena and the various ways creep-rupture data are presented and analyzed. It then examines a large collection of creep-rupture data corresponding to different alloy designations and heat treatments, identifying key relationships, similarities, and differences. It also presents a test method developed by the authors in which twelve materials are tested over a range of temperature, stress, and time in order to determine multiheat constants that are then used to fit multiheat data from other materials and thus estimate rupture times.

Strain-range partitioning is a method for assessing the effects of creep fatigue based on inelastic strain paths or strain reversals. The first part of the chapter defines four distinct strain paths that can be used to model any cyclic loading pattern and describes the microstructural damages associated with each of the four basic loading cycles. The discussion then turns to fatigue life prediction for different types of materials and more realistic loading conditions, particularly those in which hysteresis loops have more than one strain-range component. To that end, the chapter considers two cases. In one, the relationship between strain range and cyclic life is established from test data. In the other, a rule is required to determine the damage of each concurrent strain and the total damage of the cycle is used to predict creep-fatigue life. The chapter presents several such damage rules and discusses their applicability in different situations.

This chapter demonstrates the versatility of the strain-range partitioning method and its application to creep-fatigue problems involving complex loading histories. It begins with a derivation showing that it is possible to assess the damage of hysteresis loops combining two or more strain ranges using generic loops based on fundamental data. It then explains how to treat problems involving sequential loading with both healing and damage cycles and presents a general solution for combining two loops with arbitrary amounts of the four strain-range components. The chapter also derives closed-form equations that account for interactions among any number of adjacent loops and can be used, through successive application, to analyze any loading history.

This chapter compares and contrasts empirical approaches for partitioning hysteresis loops and predicting creep-fatigue life. The first part of the chapter presents experimental partitioning methods, explaining how they can be used to partition any loading cycle into its basic strain-range components. The methods covered include rapid cycling between peak stress extremes, half-cycle rapid loading and unloading, and variations of the incremental step-stress approach. The methods are then compared based on their ability to predict creep-fatigue life. The chapter goes on from there to describe how fatigue life can be estimated from ductility measurements when cyclic data are unavailable or are likely to change. It also explains how cyclic life is influenced by the time-dependent nature of creep-plasticity and the physical and metallurgical effects of environmental exposure.

This chapter explains why it is sometimes necessary to separate inelastic from elastic strains and how to do it using one of two methods. It first discusses the direct calculation of strain-range components from experimental data associated with large strains. It then explains how the method can be extended to the treatment of very low inelastic strains by adjusting tensile and compressive hold periods and continuous cycling frequencies. The chapter then begins the presentation of the second approach, called the total strain-range method, so named because it combines elastic and inelastic strain into a total strain range. The discussion covers important features, procedures, and correlations as well as the use of models and the steps involved in predicting thermomechanical fatigue (TMF) life. It also includes information on isothermal fatigue, bithermal creep-fatigue testing, and the predictability of the method for TMF cycling.

This chapter addresses the question of how to deal with multiaxial stresses and strains when using the strain-range partitioning method to analyze the effects of creep fatigue. It is divided into three sections: a general discussion on the rationale used in formulating rules for treating multiaxiality, a concise listing of the rules, and an example problem in which axial creep-fatigue data is used to predict the torsional creep-fatigue life of type 304 and 316 stainless steel. The chapter also includes a brief introduction in which the authors outline the challenges presented by multiaxial loading and set practical limits on the problem they intend to treat.

This chapter provides a detailed review of creep-fatigue analysis techniques, including the 10% rule, strain-range partitioning, several variants of the frequency-modified life equation, damage assessment based on tensile hysteresis energy, the OCTF (oxidation, creep, and thermomechanical fatigue) damage model, and numerous methods that make use of creep-rupture, crack-growth, and void-growth data. It also discusses the use of continuum damage mechanics and includes examples demonstrating the accuracy of each method as well as the procedures involved.

Fiber-reinforced metal-matrix composites have carved out a niche in applications requiring high strength to weight ratios, but they are susceptible to failure when exposed to high temperatures and cyclic loads. This chapter discusses the obstacles that must be overcome to improve the creep-fatigue behavior of these otherwise promising materials. It addresses six areas that have been the focus of intense research, including thermal-expansion and elastic-viscoplastic mismatch, thermally induced biaxiality and interply stresses, creep and cyclic relaxation of residual stresses, and enhanced interfaces for oxidation.

This chapter explains how the authors assessed the potential risks of creep-fatigue in several aerospace applications using the tools and techniques presented in earlier chapters. It begins by identifying the fatigue regimes encountered in the main engines of the Space Shuttle. It then describes the types of damage observed in engine components and the methods used to mitigate problems. It also discusses the results of analyses that led to changes in design or approach and examines fatigue-related issues in turbine engines used in commercial aircraft.

The hot-working process extrusion is used to produce semifinished products in the form of bar, strip, and solid sections, as well as tubes and hollow sections. The first part of this chapter describes the composition, properties, and applications of tin and lead extruded products with a deformation temperature range of 0 to 300 deg C and magnesium and aluminum extruded products with a working temperature range of 300 to 600 deg C. The second part focuses on copper alloy extruded products, extruded titanium alloy products, and extruded products in iron alloys with a working temperature range of 600 to 1300 deg C.

This chapter opens with a discussion of the classification of rod and tube extrusion processes. The standard processes involve hot working (extrusion at temperatures above room temperature), but some specialized cold working processes are also used for rod and tube extrusion. The next section reviews principles, variations, thermal conditions, axial load calculation, material flow, and applications of direct extrusion and indirect extrusion, with examples provided for extrusion of aluminum and copper alloys. Next, the chapter focuses on the process principles, advantages, and applications of conventional hydrostatic extrusion and thick film processes. This is followed by sections providing information on the special extrusion processes, namely conform process and cable sheathing. The chapter ends with a discussion on direct and indirect tube extrusion.

Compared with other deformation processes used to produce semifinished products, the hot-working extrusion process has the advantage of applying pure compressive forces in all three force directions, enhancing workability. The available variations in the extrusion process enable a wide spectrum of materials to be extruded. This chapter focuses on the processes involved in the extrusion of semifinished products in various metals and their alloys, namely tin, lead, lead-base soft solders, tin-base soft solders, zinc, magnesium, aluminum, copper, titanium, zirconium, iron, nickel, and powder metals. It discusses their properties and applications as well as suitable equipment for extrusion. It further discusses the processes involved in the extrusion of semifinished products in exotic alloys and extrusion of semifinished products from metallic composite materials.

This chapter begins with a description of the requirements of tooling and tooling material for hot extrusion. It covers the processes of designing tool and die sets for direct and indirect extrusion. Next, the chapter provides information on extrusion tooling and die sets for direct external and internal shape production and tools for copper alloy extrusion. Further, it addresses design, calculation, and dimensioning of single-piece and two-part containers and describes induction heating for containers. Information on static- and elastic-based analysis and dimensioning of containers loaded in three dimensions is provided. Examples of calculations for different containers, along with their stresses and dimensions, are presented and the manufacture, operation, and maintenance of containers are described. The chapter further discusses the properties and applications of hot working materials for the manufacture of extrusion tooling and of different extruded materials for the manufacture of extrusion tooling for direct and indirect forming.

This appendix contains tables listing the approximate composition of materials for the extrusion process. The materials covered are aluminum alloys, magnesium and magnesium alloys, copper and copper alloys, cobalt alloys, nickel and nickel alloys, iron alloys, steels, lead, tin, zinc alloys, molybdenum, niobium, tantalum, zirconium alloys, titanium, and titanium alloys.

This chapter provides an overview of the basic principles and historic development of metal extrusion processes. It starts by illustrating the two major process categories: direct extrusion and indirect extrusion. It then briefly defines hydrostatic extrusion and the conform process. The history coverage addresses early patents for extrusion of lead at the turn of the 17th century up through the major process innovations in the 20th century.

This chapter explains the basic terminology and principles of metallurgy as they apply to extrusion. It begins with an overview of crystal structure in metals and alloys, including crystal defects and orientation. This is followed by sections discussing the development of the continuous cast microstructure of aluminum and copper alloys. The discussion provides information on billet and grain segregation and defects in continuous casting. The chapter then discusses the processes involved in the deformation of pure metals and alloys at room temperature. Next, it describes the characteristics of pure metals and alloys at higher temperatures. The processes involved in extrusion are then covered. The chapter provides details on how the toughness and fracture characteristics of metals and alloys affect the extrusion process. The weld seams in hollow profiles, the production of composite profiles, and the processing of composite materials, as well as the extrusion of metal powders, are discussed. The chapter ends with a discussion on the factors that define the extrudability of metallic materials and how these attributes are characterized.

The machinery and equipment required for rod and tube extrusion is determined by the specific extrusion process. This chapter provides a detailed description of the design requirements and principles of machinery and equipment for direct and indirect hot extrusion. It then covers the presses and auxiliary equipment for tube extrusion, induction furnaces for billet processing, handling systems for copper and aluminum alloy products, extrusion cooling systems, and age-hardening ovens. Next, the chapter describes the principles and applications of equipment for the production of aluminum and copper billets. Then, it focuses on process control in both direct and indirect hot extrusion of aluminum alloys without lubrication. The chapter describes the technology of electrical and electronic controls in the extrusion process. It ends with a discussion on the factors that influence the productivity and quality of the products in the extrusion process and methods for process optimization.

The aim of every extrusion plant is the efficient production of competitive products that meet the appropriate quality requirements. This chapter discusses the processes involved in the selection and introduction of a quality management system, along with its application, advantages, and disadvantages. It describes the process chain for order processing within the quality circle and provides information on product liability legal issues. In addition, the chapter discusses the processes involved in quality control, along with its organization, responsibilities, audits, and testing.