Search Results for baseline isothermal fatigue testing

This article describes the phenomena of crack initiation and early growth. It examines specimen design and preparation as well as the apparatus used in crack initiation testing. The article provides descriptions of the various commercially available fatigue testing machines: axial fatigue testing machines and bending fatigue machines. Load cells, grips and alignment devices, extensometry and strain measuring devices, environmental chambers, graphic recorders, furnaces, and heating systems of ancillary equipment are discussed. The article presents technologies available to accomplish closed loop control of materials testing systems in performing standard materials tests and for the development of custom testing applications. It explores the advanced software tools for materials testing. The article includes a description of baseline isothermal fatigue testing, creep-fatigue interaction, and thermomechanical fatigue. The effects of various variables on fatigue resistance and guidelines for fatigue testing are also presented.

This article focuses on mechanical testing characterization of blended elemental powder metallurgy (PM) titanium alloys and prealloyed PM titanium alloys. It examines the tensile properties, fracture toughness, stress-corrosion threshold resistance, fatigue strength, crack propagation properties, and processing-microstructure-property relationships of these alloys. The article also reviews five considerations for powder process selection.

Wear of metals occurs by plastic displacement of surface and near-surface material, and by detachment of particles that form wear debris. This article presents a table that contains the classification of wear. It describes the testing and evaluation of wear and talks about the abrasive wear, lubrication and lubricated wear, and selection of steels for wear resistance. The article discusses the effect of alloying elements, composition, and mechanical properties of carbon and low-alloy steels at elevated temperatures. It talks about the fatigue resistance characteristics of steels, and describes the forms of embrittlement associated with carbon and low-alloy steels. The article provides information on the effect of composition, manufacturing practices, and microstructure on notch toughness of steels. Finally, it explains the effects of alloy elements, inclusion content, microstructure and heat treatment on fracture toughness of steels.

This article provides information on the thermodynamics and kinetics of high-temperature corrosion. The thermodynamics of high-temperature corrosion reactions reveals what reactions are possible under certain conditions and kinetics explains how fast these possible reactions will proceed. The article describes the diffusion process that plays a key role in oxidation and other gaseous reactions with metals. It discusses the development of stress in oxide layers. The article presents the sample preparation methods for high-temperature testing, and expounds the measurement methods of high-temperature degradation. It reviews a number of potential processes, which are responsible for high-temperature corrosion. The article details a wide range of coatings and coating processes for protecting components in a variety of operating conditions. It also discusses the testing methods used for materials at high temperatures, including furnace tests, burner rig testing, and thermogravimetric analysis, and the test methods conducted at high temperature and high pressure.

This article describes die wear and failure mechanisms, including thermal fatigue, abrasive wear, and plastic deformation. It summarizes the important attributes required for dies and the properties of the various die materials that make them suitable for particular applications. Recommendations on the selection of the materials for hot forging, hot extrusion, cold heading, and cold extrusion are presented. The article discusses the methods of characterizing abrasive wear and factors affecting abrasive wear. It discusses various die coatings and surface treatments used to extend the lives of dies: alloying surface treatments, micropeening, and electroplating.

This article presents a summary of the current and new materials and processing techniques for thermal barrier coatings (TBCs) and environmental barrier coatings (EBCs). Different thermal spraying and postspraying processing techniques are required to produce coatings with optimal performance. For TBCs and EBCs, the elastic modulus, mechanical strength, and toughness values are extremely important in predicting failure behavior under stress and strain conditions, mainly for modeling purposes. Sand and/or volcanic ash particles are molten in the hot zones of turbines and deposited over TBCs and EBCs. They form calcium-magnesium-aluminosilicate (CMAS) glassy deposits.

This article summarizes the metallurgical and environmental variables that affect fracture toughness, fatigue life, and subcritical crack growth of titanium alloys, such as chemistry, microstructure, texture, environment, and loading. The classes of titanium alloys considered in the article include alpha-beta alloys, Ti-6AI-4V; alpha alloys, Ti-8Al -1Mo-IV, Ti-5AI-2.5Sn, Ti-6242S; and beta alloys, solute-lean beta alloys and solute-rich beta alloys.

Hardening and depth of hardening of steel is a critically important material and process design parameter. This article presents a selective overview of experimental and predictive procedures to determine steel hardenability. It also covers the breadth of steel hardenability, ranging from shallow, to very difficult to harden, to air-hardening steels.

This article discusses the classification of carbon steels based on carbon content, and tabulates the compositional limits of medium- and high-carbon steels based on the AISI code and other similar codes. It describes recrystallization annealing and spheroidizing of carbon steels, and discusses the classification of carbon steels for heat treatment. The article also discusses the estimation of continuous cooling curves from isothermal transformation curves. It provides information on the Jominy end-quench test and the Grossmann method and the procedures to increase hardenabilty of carbon steels. The article includes information on the purpose of tempering and heat treating guidelines for different grades of steels, including cast carbon steels.

Corrosion modeling is an essential benchmarking element for the selection and life prediction associated with the introduction of new materials or processes. These models are most naturally expressed in terms of differential equations or in other nonexplicit forms of mathematics. This article discusses the principles and applications of various models developed for understanding the corrosion mechanism. These models include mechanistic models, including Pourbaix model, thermophysical module, electrochemical module, and ion association model; risk-based models; and knowledge models. The risk-based model and knowledge models are illustrated with examples for better understanding. The article also describes boundary-element modeling and pitting corrosion fatigue models.

The structural efficiency of a composite structure is established by its joints and assembly. Adhesive bonding, mechanical fastening, and fusion bonding are three types of joining methods for polymer-matrix composites. This article provides information on surface treatment and the applications of adhesive bonding. It discusses the types of adhesives, namely, epoxy adhesives, epoxy-phenolic adhesives, condensation-reaction PI adhesives, addition-reaction PI adhesives, bismaleimide adhesives, and structural adhesives. The article provides information on fastener selection considerations, including corrosion compatibility, fastener materials and strength, head configurations, importance of clamp-up, interference fit fasteners, lightning strike protection, blind fastening, and sensitivity to hole quality. Types of fusion bonding are presented, namely, thermal welding, friction welding, electromagnetic welding, and polymer-coated material welding.

Additive manufacturing, or three-dimensional printing technologies, for biomedical applications is rather different from other engineering components, particularly for biomedical implants that are intended to be used within the human body. This article contains two sections: "Design and Manufacturing Considerations of 3D-Printed, Commercially Pure Titanium and Titanium Alloy-Based Orthopedic Implants" and "Device Testing Considerations Following FDA Guidance" for additive-manufactured medical devices. These are further subdivided into five major focus areas: materials; design, printing, printing characteristics and parameters as well as postprinting validation; removal of the many manufacturing material residues and sterilization; physical, chemical, and mechanical assessments of the final devices; and biological considerations of all the final devices including biocompatibility.

This article describes testing and characterization methods of ceramics for chemical analysis, phase analysis, microstructural analysis, macroscopic property characterization, strength and proof testing, thermophysical property testing, and nondestructive evaluation techniques. Chemical analysis is carried out by X-ray fluorescence spectrometry, atomic absorption spectrophotometry, and plasma-emission spectrophotometry. Phase analysis is done by X-ray diffraction, spectroscopic methods, thermal analysis, and quantitative analysis. Techniques used for microstructural analysis include reflected light microscopy using polarized light, scanning electron microscopy, transmission electron microscopy, energy dispersive analysis of X-rays, and wavelength dispersive analysis of X-rays. Macroscopic property characterization involves measurement of porosity, density, and surface area. The article describes testing methods such as room and high-temperature strength test methods, proof testing, fracture toughness measurement, and hardness and wear testing. It also explains methods for determining thermal expansion, thermal conductivity, heat capacity, and emissivity of ceramics and glass and measurement of these properties as a function of temperature.

This article focuses on the principles and applications of thermal desorption spectroscopy (TDS) use to study adsorption, desorption, and reaction of adsorbed atoms and molecules on surfaces. The discussion provides information on various components of and specimen preparation processes for a TDS experiment. The factors that must be considered when performing TPD experiments and several methods of analyzing TPD data are covered. A few studies where TPD was used to elucidate surface reactions that impact the tribological performances of materials are also discussed.

Superalloys are nickel, iron-nickel, and cobalt-base alloys generally used for high-temperature applications. Superalloys are used in aircraft, industrial, marine gas turbines, nuclear reactors, spacecraft structures, petrochemical production, orthopedic and dental prostheses, and environmental protection applications. This article discusses the material characteristics, phases, structures, and systems of superalloys. It describes the processing of superalloys, including primary and secondary melting, deformation processing (conversion), powder processing, investment casting, and joining methods. The article also describes the properties, microstructure, and thermal exposure of superalloys. It further discusses the effects of environmental factors on superalloys, including oxidation and hot corrosion. Protective coatings are also discussed. The article provides information on the mechanical properties and chemical composition of nickel, iron, and cobalt-base superalloys in both the cast and wrought forms.

Tool steels are carbon, alloy, and high-speed steels that can be hardened and tempered to high hardness and strength values. This article discusses the classifications of commonly used tool steels: water-hardening tool steels, shock-resisting tool steels, cold-work tool steels, and hot-work tool steels. It describes four basic mechanisms of tool steel wear: abrasion, adhesion, corrosion, and contact fatigue wear. The article describes the factors to be considered in the selection of lubrication systems for tool steel applications. It also discusses the surface treatments for tool steels: carburizing, nitriding, ion or plasma nitriding, oxidation, boriding, plating, chemical vapor deposition, and physical vapor deposition. The article describes the properties of high-speed tool steels. It summarizes the important attributes required of dies and the properties of the various materials that make them suitable for particular applications. The article concludes by providing information on abrasive wear and grindability of powder metallurgy steels.

This article discusses bismaleimide (BMI) chemistry and the use of BMI in composites. An analysis of the applications illustrates how the advantages of BMIs have been exploited and perhaps suggests how these advantages might be extended to other applications. The article describes the mechanical properties of BMI composites. BMIs suitable for resin transfer molding processing are provided. The article concludes with information on the elevated-temperature applications of 5250-4 BMI system.