Search Results for chemical effects

This article discusses the use of a shaped electrode for electrical discharge machining (EDM). It describes the operational methodology of the EDM. Topography, metallurgical and chemical effects, and surface integrity of the EDM surface are reviewed. The article provides information on the characteristics of electrodes and the process features of electrode manufacturing. Functions of the dielectric fluids and applications of the EDM are discussed. The article reviews the advancement in EDM such as no-wear EDM and computer numerically controlled vertical EDM. It analyzes the applications and process of the traveling wire EDM. Health and safety measures for the EDM process are also discussed.

This article discusses the basic principles of and chemical effects in Auger electron spectroscopy (AES), covering various factors affecting the quantitative analyses of AES. The discussion covers instrumentation and sophisticated electronics typically used in AES for data acquisition and manipulation and various limitations of AES. Various examples highlighting the capabilities of the technique are also included.

While there are many fracture mechanisms that can lead to the failure of a plastic component, environmental stress cracking (ESC) is recognized as one of the leading causes of plastic failure. This article focuses on unpacking the basic concepts of ESC to provide the engineer with a better understanding of how to evaluate and prevent it. It then presents factors that affect and contribute to the susceptibility of plastic to ESC: material factors, chemical factors, stress, and environmental factors. The article includes the collection of background information to understand the circumstances surrounding the failure, a fractographic evaluation to assess the cracking, and analytical testing to evaluate the material, design, manufacturing, and environmental factors.

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.

With any polymeric material, chemical exposure may have one or more different effects. Some chemicals act as plasticizers, changing the polymer from one that is hard, stiff, and brittle to one which is softer, more flexible, and sometimes tougher. Often these chemicals can dissolve the polymer if they are present in large enough quantity and if the polymer is not crosslinked. Other chemicals can induce environmental stress cracking (ESC), an effect in which brittle fracture of a polymer will occur at a level of stress well below that required to cause failure in the absence of the ESC reagent. Finally, there are some chemicals that cause actual degradation of the polymer, breaking the macromolecular chains, reducing molecular weight, and diminishing polymer properties as a result. This article examines each of these effects. The discussion also covers the effects of surface embrittlement and temperature on polymer performance.

True alkaline chemicals include caustic soda or sodium hydroxide (NaOH), caustic potash or potassium hydroxide (KOH), and soda ash or sodium carbonate (Na2CO3). This article reviews alkaline chemicals and provides a basis for a general discussion on various alkaline exposures. It describes the corrosion effects of caustic soda on aluminum and aluminum alloys, iron and steel, carbon and low-alloy steels, stainless steels, high-performance austenitic alloys, nickel and nickel alloys, copper and copper alloys, titanium and titanium alloys, and zirconium and zirconium alloys. The article discusses the corrosion effects of caustic soda on nonmetallic materials: plastics, thermoplastics, thermosetting resin materials, carbon and graphite, and ceramics. It concludes with information on the effects of contamination of and by caustic and of admixtures of caustic with other chemicals, including chlorates, chlorides, chlorine/hypochlorite, mercury, sulfur, and iron.

This article discusses the wrought product forms of titanium and titanium-base alloys, which include forgings and the typical mill products with tabulations for various specifications, and compares specifications for pure titanium, titanium alloys for mechanical, physical properties and chemical properties, including chemical composition, corrosion resistance, and chemical reactivity. The article discusses the effects of alloying elements in titanium alloys, and describes the classes of titanium alloys, namely, alpha alloys, alpha-beta alloys, and beta alloys. It also describes the typical applications of various titanium-base materials, and explains the crystal structure, effect of impurities, and microstructural constituents of titanium alloys. The article provides a brief description on the processing of wrought titanium alloys, including primary fabrication in which ingots are converted into general mill products and secondary fabrication (forging, extrusion, forming, machining, chemical milling and joining) of finished shapes from mill products and the heat treatment of titanium alloys.

Hygrothermal behavior of cured composite materials relates to the combined and commonly synergistic effects of moisture absorption and temperature on various physical, chemical and mechanical properties. This article focuses on the influence of resins or matrices, reinforcements, processing, and diffusion on hygrothermal behavior of polymer-matrix composites and provides an outline on general considerations in assessing them. It discusses the hygrothermal testing and conditioning of polymer-matrix composites to assess fundamental hygrothermal behavior. The article provides information on the accelerated aging process for understanding the degradation mechanisms and failure modes in composites. It also describes the effect of moisture absorption on mechanical properties of polymer-matrix composites.

A wide range of mechanical properties can be obtained with a given composition of cast iron, depending on the microstructural constituents that form during solidification and subsequent solid-state processing. This article discusses the mechanical properties of gray iron and provides some general property comparisons with malleable, ductile (nodular), and compacted graphite irons. The mechanical properties of gray iron are determined by the combined effects of its chemical composition, processing technique in the foundry, and cooling rates during solidification. The article provides information on the classification of gray irons based on ASTM International specification A48/A48M. It discusses the loading effect, surface effect, notch sensitivity, and environmental effect on the mechanical properties of gray iron. The chemical composition ranges of some of the more widely used heat-resistant gray irons suitable for elevated-temperature service are presented in a table.

Chemical analysis is a critical part of any failure investigation. With the right planning and proper analytical equipment, a myriad of information can be obtained from a sample. This article presents a high-level introduction to techniques often used for chemical analysis during failure analysis. It describes the general considerations for bulk and microscale chemical analysis in failure analysis, the most effective techniques to use for organic or inorganic materials, and examples of using these techniques. The article discusses the processes involved in the chemical analysis of nonmetallics. Advances in chemical analysis methods for failure analysis are also covered.