Search Results for material

This article focuses on the visual or macroscopic examination of damaged materials and interpretation of damage and fracture features. Analytical tools available for evaluations of corrosion and wear damage features include energy dispersive spectroscopy, electron probe microanalysis, Auger electron spectroscopy, secondary ion mass spectroscopy, and X-ray powder diffraction. The article discusses the analysis and interpretation of base material composition and microstructures. Preparation and examination of metallographic specimens in failure analysis are also discussed. The article concludes with a review of the evaluation of polymers and ceramic materials in failure analysis.

This article discusses three types of powder-feeder systems that are commonly used throughout the thermal spray (TS) industry: gravity-based devices, rotating wheel devices, and fluidized-bed systems. It provides information on the various mechanical methods for producing powders, namely, crushing, milling, attriting, and machining. The article describes two prime methods of agglomeration. One method uses a binder by way of agglutination, while the other relies on a sintering operation. The article discusses the technology and principles of the processes that relate to thermal spraying, and offers an understanding for choosing particular feedstock materials that are classified based on the thermal spray process, material morphology, chemical nature of the material, and applications. Sieving, the most common method of separating powders into their size fractions, is also reviewed. The article also provides information on the topical areas and precautions to be undertaken to protect the operator from safety hazards.

This article discusses the corrosion characteristics of superaustenitic stainless and duplex stainless steels, which are used in pharmaceutical industry. It describes passivation treatments and the electropolishing of stainless steels. The article informs that electropolishing is not a passivation treatment, although the proper execution of the process will result in a passive surface. The article concludes with a discussion on roughing, which is a phenomenon of particular interest to the pharmaceutical industry.

The handling of billets or bars is an essential part of an induction heating system. This article describes two types of handling systems available for bar heating lines: inclined ramps with escapement, and sling feeder with inclined ramp and escapement. It focuses on the various infeed billet handling systems such as bin tippers, elevator feeders, rotary feeders, vibratory bowl feeders, magazine loaders, and rod feeders. The article provides information on the main categories of billet feeding systems, namely, dual pinch roll drive assemblies, tractor drive assemblies, billet pusher systems, walking beam assemblies, and index/continuous conveyor systems. It also discussed the hot billet handling systems used to deliver heated billets to the forging cell. These methods include billet extractor conveyors, accept/reject systems with pyrometer measurements, extractor rolls, discharge chutes, pinch roll extractors, pick-n-place systems, and robots.

This article focuses on the influence of various work material properties, namely, hardness; toughness; stiffness; ductility; thermal, electrical, and magnetic properties; and microstructure effects on finishing methods. It also addresses the relative response of work materials, such as metals, ceramics, and composites, to grinding.

There are many reasons why plastic materials should not be considered for an application. It is the responsibility of the design/materials engineer to recognize when the expected demands are outside of what the plastic can provide during the expected life-time of the product. This article reviews the numerous considerations that are equally important to help ensure that part failure does not occur. It provides a quick review of thermoplastic and thermoset plastics. The article focuses primarily on thermoset materials that at room temperature are below their glass transition temperature. It describes the motivation for material selection and the goal of the material selection process. The use of material datasheets for material selection as well as the processes involved in plastic material selection and post material selection is also covered.

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.

Examination of a damaged component involves a chain of activities that, first and foremost, requires good observation and documentation. Following receipt and documentation, the features of damage can be recorded and their cause(s) investigated, as this article briefly describes, for typical types of damage experienced for metallic components. This article discusses the processes involved in visual or macroscopic examination of damaged material; the interpretation of fracture features, corrosion, and wear damage features; and the analysis of base material composition. It covers the processes involved in the selection of metallurgical samples, the preparation and examination of metallographic specimens in failure analysis, and the analysis and interpretation of microstructures. Examination and evaluation of polymers and ceramic materials in failure analysis are also briefly discussed.

Statistical analysis of mechanical property data is the most reliable method for determination of minimum design allowables. This article describes the general procedures used to determine design allowables. It provides information on the determination of a distribution form. The article presents statistical methods which help in determining design allowables. These methods include direct computation for normal distribution, direct computation for an unknown distribution, computation of derived properties, and regression analysis. The article concludes with information on low- and elevated-temperature design properties.

This article discusses the advantages, limitations, and applications of material jetting of ceramics, focusing on two primary methods of droplet formation: continuous stream and drop on demand (thermal and piezoelectric) ink jetting processes.

Material jetting (MJ) is a classification of additive manufacturing processes that involves the selective jetting and subsequent solidification of liquid droplets onto a substrate in a layerwise manner. This article focuses solely on MJ of polymers, providing a process overview and describing the functional characteristics that distinguish it from other AM technologies. It provides information on the properties and design considerations of both build and support materials. Process-related effects on final part properties and overall quality, as well as corresponding design considerations are also covered. The article also discusses the applications and future scope of polymer MJ systems.

This article is a review of the material extrusion-based ceramic additive manufacturing (MECAM) processes. The discussion begins with details of extrusion with filament and paste, covering the most popular variants of paste extrusion-based MECAM techniques that can be differentiated based on paste type and the method of shape retention of the deposited layer: extrusion freeforming, robocasting ceramic on-demand extrusion, and freeze-form extrusion fabrication. The article then focuses on post-processing considerations and the mechanical properties of sintered ceramic parts. It concludes with information on innovation opportunities in ceramic additive manufacturing, such as incorporating UV-curing and gelation in the process and producing geometrically complex structures from shapeable green bodies.

Material extrusion systems are the most common types of additive manufacturing systems, also known as three-dimensional (3D) printers. This article focuses on the general 3D printing processes as can be demonstrated and manipulated in desktop printers. The discussion includes details of the components involved in material extrusion as well as the melt extrusion solidification (during cooling) process, the underlying mechanism of road bonding, and the factors affecting good part quality. The discussion also covers support material, postprocessing, and road-quality considerations and the addition of infill in melt extrusion to the hollow spaces inside an object to give it structural strength. Information is also provided on different materials and associated material properties that affect the rate the printer is able to advance and retract material, thereby affecting the quality and rate at which a part is printed. The final section provides information on the mechanism of viscous extrusion 3D printing.

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.

This article presents the background to the CALculation of PHAse Diagrams (CALPHAD) method, explaining how it works, and how it can be applied in industrial practice. The extension of CALPHAD methods as a core basis for the modeling of generalized material properties is explored. It informs that one of the aims of CALPHAD methods has been to calculate phase equilibria in the complex, multicomponent alloys that are used regularly by industry. The article discusses the application of CALPHAD calculations to industrial alloys. Modeling of general material properties, such as thermophysical and physical properties, temperature- and strain-rate-dependent mechanical properties, properties for use in the modeling of quench distortion, and properties for use in solidification modeling, is also reviewed. The article also describes the linking of thermodynamic, kinetic, and material property models.

This article focuses specifically on material modeling applied to structure-property predictions. It provides general guidelines and considerations in terms of modeling the salient material features that ultimately impact the mechanical performance of parts produced by additive manufacturing (AM). Two of the primary ingredients needed to predict structure-property relationships via material modeling include a geometrical representation of the microstructural features of interest (e.g., grain structure and void defects) and a suitable constitutive model describing the material behavior, both of which can be scale and resource dependent. The article also presents modeling challenges to predict various aspects of (process-) structure-property relationships in AM.

The article presents an in-depth discussion on the various additive manufacturing techniques such as binder jetting, directed-energy deposition, material extrusion, material jetting, powder-bed fusion, sheet lamination, and vat polymerization processes. This article then discusses the different critical material aspects of additively manufactured medical devices, beginning with the preprinting phase (material consistency and recycling), the printing phase (build orientation), and the postprinting phase (part evaluation, biocompatibility, and sterilization) with supporting materials.

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.

Properties of an engineering material have a characteristic range of values that are conveniently displayed on materials selection charts. This article describes the plotting of data on these charts. It discusses the features of various types of material property charts, namely, modulus-density, strength-density, fracture toughness-density, modulus-strength, specific stiffness-specific strength, fracture toughness-modulus, fracture toughness-strength, loss coefficient-modulus, thermal conductivity-thermal diffusivity, thermal expansion-thermal conductivity, thermal expansion-modulus, and normalized strength-thermal expansion charts. The article examines the use of material property charts in presenting information in a compact and easily accessible manner.

In-process inspection during composite material lay-up is essential if the structural, dimensional, and environmental performance designed into a part is to be consistently achieved. This article discusses the requirements to be met by the facilities and equipment to produce high-quality composites. It reviews the procedures that are allowed and prohibited in controlled-contamination areas of lay-up. The article emphasizes significant areas, such as material control and lay-up process, in which quality-control personnel can be effective in preventing production problems. It concludes with a discussion on automated tape laying and fiber placement, as well as the numerically aided lay-up process.