Search Results for flat-pattern evaluation

Continuous fiber composite materials offer dramatic opportunities for producing lightweight laminates with tremendous performance capabilities. This article describes the kinematics of fabric deformation and explains the algorithms used in draping simulation. It discusses the basic components, such as laminate and ply, of continuous fiber composite. The article provides information on the core sample and ply analysis. It details producibility, flat-pattern evaluations, and laminate surface offset. The article discusses various interfaces, such as the structural analysis interface, the resin transfer molding interface, the fiber placement and tape-laying interface, and the laser projection interface.

Optical testing of plastics includes the characterization of materials and the analysis of optical components. If a material is tested for transmission, haze, yellowness, and refractive index, the knowledge of its optical properties is nearly complete. For optical components, surface irregularity, birefringence, and internal contamination must also be considered. These characteristics are a function of the material and the fabrication method. Gloss and color also are affected by the base material and measured as optical properties.

Optical testing of plastics includes characterization of materials and analysis of optical components. This article focuses on procedures for testing various characteristics of optical components, including transmission and haze, yellowness, refractive index, birefringence, as well as surface irregularity, contamination, gloss, and color. It provides a short note on ad hoc testing, which is beneficial for practical applications in which lenses, prisms, and light pipes are being used and tested, as other test instruments are often not available.

This article illustrates typical fractographic features for a number of different composite materials. It describes the differences in fracture characteristics due to different loading, material processing, and environmental conditions. The article presents fractographic data obtained from epoxy matrix materials. Minimal fractographic data from other brittle thermoset resin systems are also presented. The article discusses the interlaminar fracture of composites with ductile thermoplastic matrices. It also provides information on the translaminar fracture features of the composite materials.

Tooling and assembly methodologies for advanced composites have steadily improved as a result of advancements in materials, through the use of computer-aided design/computer-aided manufacturing technology, and through application of sophisticated design for manufacturing and assembly concepts. This article reviews techniques and technologies that are used to control the quality of tooling and assembly methods for composite components.

Ultrasonic inspection is a nondestructive technique that is useful in both quality control and research applications for flaw detection in fiber-reinforced composite materials. This article describes ultrasonic nondestructive analysis by outlining its three basic types of scans. It reviews the important quality control techniques used during the manufacture of composite components by analyzing tooling control, material control, pattern orientation control, and in-process control.

Optical metallography, one of the most common materials characterization techniques, uses visible light to magnify structural features of interest. This article discusses the use of optical methods to evaluate micro and macrostructure and relate it to process conditions and material behavior. It covers the steps involved in sample preparation, including sectioning, mounting, grinding, polishing, and etching, and presents several examples of macro and microanalysis on various metals and alloys.

Most surfaces have regular and irregular spacings that tend to form a pattern or texture on the surface. This article provides information on the general background of surface topography and discusses the different methods for measuring surface topography, namely, contact and noncontact techniques, and the focus-follow method. Examples of different types of parameters obtained and how they are applied can best be described by discussing the various types of surfaces generated by finishing methods. The surfaces include ground, turned, and milled machined surfaces; surfaces subjected to stress; bearing surfaces; plateau honed and tapped surfaces; and reflective, painted, elastic, and wear-resistant surfaces.

Surface damage from sliding contact is related to the adhesion of mating surfaces in contact. This article describes the methods for evaluation of surface damage caused by sliding contact. It defines adhesive wear in terms of asperity, cold welding, galling, scuffing, seizure, and wear coefficient. The article discusses various galling testing methods, such as button-on-block galling test, pin-on-flat galling test, and threaded connection galling test. It provides an overview of fretting wear that occurs between two tight-fitting surfaces subjected to a cyclic, relative motion of extremely small amplitude. The article also reviews the fretting rig for investigating fretting wear.

This article describes the process and advantages of no-bond methods of vacuum molding and magnetic molding, with schematic illustrations. It also discusses the characteristics of plastic film and dimensional specifications of vacuum molding.

This article discusses the types of patterns used for a specific application such as loose patterns, match plate patterns, cope and drag patterns, and special patterns. It describes the principles of the patternmaking techniques used to make expendable molds and for metal casting processes such as die casting and permanent mold casting. The article reviews the pattern features and mold production considerations used in the pattern design, namely, parting line considerations, addition of gates and risers, core prints, and locating points. It examines the pattern allowances for ensuring a dimensionally correct final pattern. A variety of materials and advanced composite materials used in the manufacture of patterns are discussed. The article evaluates the factors influencing the selection of type of patterns for specific castings.

Part quality in additive manufacturing (AM) is highly dependent on process control, but there is a lack of adequate AM control methods and standards. Laser powder-bed fusion (L-PBF) is one of the most-used metal AM techniques. This article focuses on the following laser control parameters: laser focus, laser power, laser position, and laser power-position synchronization. It then provides a discussion on laser scan strategies. The article also provides an overview of the AM control framework, the two major sections of which are software and hardware.

Sheet forming failures divert resources from normal business activities and have significant bottom-line impact. This article focuses on the formation, causes, and limitations of four primary categories of sheet forming failures, namely necks, fractures/splits/cracks, wrinkles/loose metal, and springback/dimensional. It discusses the processes involved in analytical tools that aid in characterizing the state of a formed part. In addition, information on draw panel analysis and troubleshooting of sheet forming failures is also provided.

X-ray diffraction techniques are useful for characterizing crystalline materials, such as metals, intermetallics, ceramics, minerals, polymers, plastics, and other inorganic or organic compounds. This article discusses the theory of x-rays and how they are generated and detected. It also describes the crystalline nature of certain materials and how the geometry of a unit cell, and hence crystal lattice, affects the direction and intensity of diffracted x-ray beams. The article concludes with several application examples involving measurements on single and polycrystalline materials.

This article addresses macroscale fracture appearances, microscale fracture-surface appearances or morphologies, fracture mechanisms, and those factors that influence fractures and fracture appearances. Some of the macroscopic and microscopic features identified by the failure analyst to evaluate the fracture surfaces of metals and plastics are described and compared.

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 discusses the inspection/reference standards that are absolutely critical for proper application of ultrasonic inspection systems. Many of the standards and specifications for ultrasonic inspection require the use of standard reference blocks. The article lists the variables that should be considered when selecting standard reference blocks and describes the three types of standard blocks ordinarily used for calibration or reference: area-amplitude blocks, distance-amplitude blocks, and blocks of the type sanctioned by the International Institute of Welding. It reviews the determination of area-amplitude and distance-amplitude curves of a straight-beam pulse-echo ultrasonic inspection system. The article discusses the three principal conventional manual ultrasonic sizing techniques: 6 dB drop technique, maximum-amplitude technique, and 20 dB drop technique. It provides information on the dimension-measurement applications of ultrasonic inspection methods.

Shell molding is used for making production quantities of castings that range in weight from a few ounces to approximately 180 kg (400 lb), in both ferrous and nonferrous metals. This article lists the limitations or disadvantages of shell mold casting. It describes the two methods for preparation of resin-sand mixture for shell molding, namely, mixing resin and sand according to conventional dry mixing techniques, and coating the sand with resin. Shaping of shell molds and cores from resin sand mixtures is accomplished in machines. The article discusses the major steps in producing a mold or core and describes the problems most frequently encountered in shell-mold casting. The problems include mold cracking, soft molds, low hot tensile strength of molds, peelback, and mold shift. The article concludes with information on examples that provide some relative cost comparisons between shell molding and green sand molding.

Hot extrusion is a process in which wrought parts are formed by forcing a heated billet through a shaped die opening. This article discusses nonlubricated and lubricated hot extrusion. The two nonlubricated hot extrusion methods are forward or direct extrusion and backward or indirect extrusion. The article illustrates the significance of extrusion speeds and temperatures in hot extrusion. It describes the basic types of presses used in the hot extrusion of metals. The article provides information on the characterization of extruded shapes and explains the operating parameters, including extrusion velocity, amount of pressure required, and type of lubricant, for successful and efficient hot extrusion. The article concludes with a discussion on applications and design methodology that provides insight into CAD/CAM of extrusion dies.

This article discusses the development of a welding procedure for friction stir welding (FSW), including the process of defining a preliminary procedure, the optimization of parameters, the development of supporting data, and other key features to ensure a successful procedure. The critical features of FSW tool design, initial process parameters, systematic welding trials, and robustness testing are reviewed. The article provides information on the common features of welding procedure qualification. It also includes a table that lists the procedures used in the production of sound friction stir welds in various aluminum alloys.