Search Results for truncated cones

This article discusses the mill products most often formed by the three-roll forming process. It schematically illustrates some of the shapes commonly produced from flat stock by the three-roll forming process. The article describes the two basic types of three-roll forming machines, namely, the pinch-roll type and the pyramid-roll type. It also lists the advantages of the pinch-roll machine, as compared to the pyramid-roll machine. The article analyzes the hot forming and cold forming processes for carbon or low alloy steel. It explains the procedure for forming truncated cones, bars, and bar sections by utilizing the pyramid-roll machine.

Resistance spot welding (RSW) is a process in which faying surfaces are joined in one or more spots by the heat generated by resistance to the flow of electric current through workpieces that are held together under force by electrodes. This article discusses the major advantages of spot welding and the three principal elements, such as electrical circuit, control circuit, and mechanical system, of RSW machines. It reviews the three basic types of RSW machines: pedestal-type welding machines, portable welding guns, and multiple spot welding machines. The article provides information on weldabilily of uncoated steels and zinc-coated steels, as well as aluminum alloys.

Workability in forging depends on a variety of material, process-variable, and die-design features. A number of test techniques have been developed for gaging forgeability depending on alloy type, microstructure, die geometry, and process variables. This article summarizes some common workability tests and illustrates their application in practical forging situations. Workability tests for open-die forging of cast structures, hot and cold open-die forging of recrystallized structures, fracture-controlled defect formation, establishing effects of process variables and secondary tensile stresses on forgeability, and flow-localization-controlled failure are some common tests. The workability test used for closed-die forging is also summarized.

The gas-tungsten arc welding (GTAW) process is performed using a welding arc between a nonconsumable tungsten-base electrode and the workpieces to be joined. The arc discharge requires a flow of electrons from the cathode through the arc column to the anode. This article discusses two cases of electron discharge at the cathode: thermionic emission and nonthermionic emission, also called cold cathode, or field emission. It schematically illustrates relative heat transfer contributions to workpiece in the GTAW process. The article provides information on the effects of cathode tip shape and shielding gas composition in the GTAW process.

Rheology is defined as the study of the flow and deformation of matter. This article begins with an examination of flow behavior. It describes the geometries and methods employed for rheological testing of polymers in their molten state. It also discusses materials that are predominantly in the solid state and the methods employed for solids testing. Examples of unidirectional and dynamic oscillatory testing are provided for different mechanical behaviors.

A material is flammable if it is subject to easy ignition and rapidly flaming combustion. The plastics that are most widely used are the least expensive and tend to be the most flammable. This article describes the two basic approaches to improving the fire resistance of a polymeric material: modifying or substituting the basic polymer so that exposure to heat and oxygen will not produce rapid combustion, and using flame-retardant additives. It also provides an overview of the burning process and presents two flammability test methods.

Flammability is the ability of a material to undergo easy ignition and rapid flaming combustion. This article provides information on flammability tests of polymers and codes and regulations that cite these tests. Many organizations are involved in the characterization and specification of flammability properties, resulting in several categorization strategies for flammability tests, including tests for specific fire response characteristics, research tests versus acceptance tests, tests for different levels of severity, and tests for basis of origin. The article presents an overview on the basic approaches in improving the fire resistance of polymers and the burning process (heating, decomposition, ignition, combustion, and propagation). It provides a brief description on the test methods which are classified into two types, one based on fire response characteristics and the other on particular applications of polymeric materials.

This article discusses the bulk formability or workability of steels. It describes their formability characteristics and presents procedures for various formability tests used for carbon and alloy steels. Tests for bulk formability can be divided into two main categories: primary tests and specialized tests. The article compares the processing of microalloyed plate and bar products. The article focuses on the use of torsion testing to evaluate the forgeability of carbon and alloy steels and presents information on measuring flow stress. The article discusses the metallurgy and thermomechanical processing of high-strength low-alloy (microalloyed) steels and the various parts of the rolling operation. The article summarizes some of the common tests for determining formability in open-die and closed-die forgings.

Resistance spot welding (RSW) is the most widely used joining technique for the assembly of sheet metal products. This article discusses the process description, evaluation methods, and applications of RSW. It describes the equipment needed for RSW and explicates the major functions of electrodes in RSW and effect of surface condition on the technique. The article concludes with information on the safety precautions to be followed during the welding process.

A key differentiator between friction stir welding (FSW) and other friction welding processes is the presence of a nonconsumable tool in FSW, often referred to as a pin tool to differentiate it from other tooling associated with the process. This article discusses materials for friction stir welding (FSW) pin tools, various tool geometries that have been used, designs for specific applications, predicting and measuring tool performance, and other considerations in FSW pin tool design. The tool materials include tool steels, superalloys, refractory metals, carbides and ceramics, and superabrasives.

Designing composites for structural performance initially involves meeting a set of desired performance specifications at a minimum cost. This article discusses the factors that are considered in designing the manufacturing of polymeric composites. It describes the various aspects of manufacturing, forming process, and post-processing and fabrication for designing the composites.

The goal of design is to improve the overall performance of the metal or ceramic matrix rather than to create a material with different response than the base matrix. This article focuses on the design for manufacturing polymeric composites. Specially developed methods including contact molding, compression-type molding, resin-injection molding, and pultrusion are described. The article also discusses the various factors to be considered in designing for composite manufacturing.

This article discusses the application of friction stir processing (FSP) and friction surfacing for tribological components. It describes the three critical aspects involved in the application of FSP for near-surface material modifications intended for tribological applications. These include tools, processing parameters, and machines. The article also discusses the equipment and processing parameters for friction surfacing. It describes various hybrid stir processing techniques that involve preheating of the workpiece material, especially relatively hard and high-strength ones. The article presents a partial list of surface-modification methods based on FSP. The partial list includes surface hardening, surface composites, and additive coating. The article also provides information on generation of residual stresses in metallic materials and alloys form different variants of FSP.

Fractography is the means and methods for characterizing a fractured specimen or component. This includes the examination of fracture-exposed surfaces and the interpretation of the fracture markings as well as the examination and interpretation of crack patterns. This article describes the former of these two parts of fractography. It presents the techniques of fractography and explains fracture markings using glass and ceramic examples. The article also discusses the fracture modes in ceramics and provides examples of fracture origins.

This article describes the general root causes of failure associated with wrought metals and metalworking. This includes a brief review of the discontinuities or imperfections that may be the common sources of failure-inducing defects in bulk working of wrought products. The article discusses the types of imperfections that can be traced to the original ingot product. These include chemical segregation; ingot pipe, porosity, and centerline shrinkage; high hydrogen content; nonmetallic inclusions; unmelted electrodes and shelf; and cracks, laminations, seams, pits, blisters, and scabs. The article provides a discussion on the imperfections found in steel forgings. The problems encountered in sheet metal forming are also discussed. The article concludes with information on the causes of failure in cold formed parts.