Search Results for laser dimpling

Lasers evolved as a versatile materials processing tool due to their advantages such as rapid, reproducible processing, chemical cleanliness, ability to handle variety of materials, and suitability for automation. This article focuses on state-of-the-art laser applications to improve tribological performance of structural materials in lubricated and nonlubricated environments. It discusses the fundamentals of various laser materials interactions and reviews laser-based surface-modification strategies, including laser surface heating and melting, laser-synthesized coatings, and laser-based design approaches such as laser patterning and dimpling. Laser-surface modification of novel materials, such as high-entropy alloys and metallic glasses, is explored. The article provides an overview of hybrid techniques involving laser as a secondary tool, as well as a discussion on the improved capabilities of laser surface engineering for tribological applications by means of integrated computational process modeling.

This article provides an overview of surface-texturing techniques. It describes the texturing parameters, namely, shape, depth, and width of the textured pattern, its aspect ratio (depth over width), texture area density, and orientation. The article explains the effect of these parameters on tribological behavior of textured surfaces. It provides information on various modeling approaches for surface texture. The article also discusses the beneficial effect of surface texturing.

The development of quantitative fractography (QF) parameters basically requires topological data of a fracture surface that can be derived from the stereological analysis of multiple projected scanning electron microscope (SEM) images; the profilometry-based techniques that measure the fracture surface profile along x-y sections of a fracture surface from metallographic sections or nondestructive techniques; and the three-dimensional reconstruction of the fracture surface topology using imaging methods such as stereo SEM imaging and confocal scanning laser microscopy. These three general methods of assessing fracture surface topology are reviewed in this article.

The quantitative characterization of fracture surface geometry, that is, quantitative fractography, can provide useful information regarding the microstructural features and failure mechanisms that govern material fracture. This article is devoted to the fractographic techniques that are based on fracture profilometry. This is followed by a section describing the methods based on scanning electron microscope fractography. The article also addresses procedures for three-dimensional fracture surface reconstruction. In each case, sufficient methodological details, governing equations, and practical examples are provided.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of titanium alloys and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the fracture surface, fatigue crack growth, intergranular fracture, crack propagation, ductile overload fracture, dimpled rupture, microvoid coalescence, and quasi-cleavage fracture of these alloys.

This article describes the general factors that can influence fracture appearances. The focus is on the general practical relationships of fracture appearances, with factors presented in some broad categories, including: material conditions (e.g., crystal structure and microstructure); loading conditions (stress state, strain rate, and fatigue); manufacturing conditions (casting, metal-working, machining, heat treatment, etc.); and service and environmental factors (hydrogen embrittlement, stress corrosion, temperature, and corrosion fatigue).

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of wrought aluminum alloys and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the corrosion-fatigue fracture, fatigue striations, tension-overload fracture surface, ductile fracture, cone-shaped fracture surface, intergranular crack propagation, transgranular crack propagation, stress-corrosion cracking, hydrogen damage, and grain-boundary separation of these alloys. Fractographs are also provided for a forged aircraft main-landing gear wheel and actuator beam, an aircraft wing spar, a fractured aircraft propeller blade, shot peened fillet, an aircraft lower-bulkhead cap, and clevis-attachment lugs.

Many metal failures involve fracture, and fractography is an essential activity in many, if not most, failure analysis (FA) investigations. This article introduces and illustrates the role of fractography in an FA investigation. Basic guidelines are briefly presented for investigating a failure and how fractography helps the FA investigator determine evidence. Examples are given throughout this article on how the examination of fracture surfaces discerns various sources of crack initiation and mechanisms of crack growth. The procedures for analyzing fractures also include several steps and techniques that involve photographic documentation, proper specimen handling, and visual or microscopic examination. The article also briefly describes the use of metallography in fracture analysis along with case studies as illustrative examples of various fracture mechanisms and modes.

This article presents a detailed discussion on the microstructures, physical metallurgy, classification, deformation behavior, and fracture modes of titanium alloys. It illustrates the effect of microstructure and texture on the fracture topography and fracture behavior of titanium alloys with a variety of relevant examples.

This article describes the fracture toughness behavior of austenitic stainless steels and their welds at ambient, elevated, and cryogenic temperatures. Minimum expected toughness values are provided for use in fracture mechanics evaluations. The article explains the effect of crack orientation, strain rate, thermal aging, and neutron irradiation on base metal and weld toughness. It discusses the effect of cold-work-induced strengthening on fracture toughness. The article examines the fracture toughness behavior of aged base metal and welding-induced heat-affected zones. It concludes with a discussion on the Charpy energy correlations for aged stainless steels.

Engineering component and structure failures manifest through many mechanisms but are most often associated with fracture in one or more forms. This article introduces the subject of fractography and aspects of how it is used in failure analysis. The basic types of fracture processes (ductile, brittle, fatigue, and creep) are described briefly, principally in terms of fracture appearances. A description of the surface, structure, and behavior of each fracture process is also included. The article provides a framework from which a prospective analyst can begin to study the fracture of a component of interest in a failure investigation. Details on the mechanisms of deformation, brittle transgranular fracture, intergranular fracture, fatigue fracture, and environmentally affected fracture are also provided.

This article briefly reviews the forming of steel tailor-welded blanks (TWB) with a discussion on the effects of welding on forming. It presents the parameters that are monitored to control the stamping operation for tailor-welded blanks. The article discusses weld factors such as the orientation of weld relative to metal movement in dies, the formability of TWB materials, die and press considerations, and specific factors for the drawing, stretching, and bending of steel tailor-welded blanks.

This article describes different types of titanium alloys, including alloy Ti-6Al-4V, alpha and near-alpha alloys, and alpha-beta alloys. It explains the formability of titanium alloys with an emphasis on the Bauschinger effect. The article provides information on the tool materials and lubricants used in the forming process. It provides information on the cold and hot forming, superplastic forming, and combination of superplastic forming/diffusion bonding. The article discusses the various forming processes of these titanium alloys, including press-brake forming, power (shear) spinning, rubber-pad forming, stretch forming, contour roll forming, creep forming, vacuum forming, drop hammer forming, joggling, and explosive forming.

Directed-energy deposition (DED) is a kind of additive manufacturing (AM) technology based on synchronous powder feeding or wire feeding. This article provides a comprehensive coverage of DED for ceramic AM, beginning with an overview of DED equipment setup, followed by a discussion on DED materials and the DED deposition process. The bulk of the article is devoted to the discussion on the microstructure and properties of oxide ceramics, namely alumina and zirconia ceramics.

This article provides an overview of metal additive manufacturing (AM) processes and describes sources of failures in metal AM parts. It focuses on metal AM product failures and potential solutions related to design considerations, metallurgical characteristics, production considerations, and quality assurance. The emphasis is on the design and metallurgical aspects for the two main types of metal AM processes: powder-bed fusion (PBF) and directed-energy deposition (DED). The article also describes the processes involved in binder jet sintering, provides information on the design and fabrication sources of failure, addresses the key factors in production and quality control, and explains failure analysis of AM parts.