Electrochemical oxidation analysis for dressing bronze-bonded diamond grinding wheels

Electrochemical dressing of fine-grained metal-bonded diamond grinding wheels enables to grind hard and brittle materials in the ductile mode. Optical surfaces can be manufactured by grinding, which reduces the need for subsequent, time-consuming polishing work. When using metal-bonded grinding wheels, the emerging oxides regulate the electrochemical dissolution. Bronze-bonded grinding wheels are more suitable for grinding cemented carbides and ceramics than iron-bonded grinding wheels, as it is easier to modify their chemical composition to suit a specific grinding task. They can also be sintered at lower temperatures, which reduces the risk of thermal damage to the diamond. In this paper, the dissolution and the oxidation of different bronze alloys are characterized for the electrochemical dressing process. The relevant evaluation criteria are the oxide layer thickness, the electrical behavior and the different emerging bronze alloy oxides. This work is funded by the German Research Association DFG within the Transregional Collaborative Research Center SFB/TR4 “Process Chains for the Replication of Complex Optical Elements”.     

Robust flexible LCDs with paintable technology

Abstract— In this article, second‐generation liquid‐crystal displays (LCDs) made by Paintable LCD technology is presented. With this technology, LCDs are manufactured by a sequence of simple coating and UV curing processes. Since the process can be carried out on plastic substrates and the stack of optical layers is only tens of micrometers thick, the resulting LCDs are ultra‐thin and flexible.     

Embeddable strain gage units for measuring strains in concrete

This paper presents the development of three types of embeddable strain gage units for measuring normal strains of concrete respectively in one, two, and three orthogonal directions. The construction of the units is described in detail and tests are performed to check the reliability of strain readings obtained from them. Strains from the embeddable units and from surface bonded strain gages are compared. The advantages and applications of the gage units are discussed.     

Anomalous influence of polarity in sink EDM of titanium alloys

An anodic tool polarity is generally adopted in sink electrical discharge machining (EDM) to maximize material removal relative to tool wear. Sink EDM of Ti and Ti6Al4V is however atypical in that these materials necessitate a cathodic tool polarity. Adding to the intrigue is γ-TiAl, which machines better under the conventional anodic polarity. This research focused on clarifying the phenomena behind this interesting behavior by investigating removal mechanisms over a range of relevant process conditions. The anomaly is demonstrated to arise from the polarity-dependent nature and extent of TiC formation on the work surface, which significantly affects material removal.     

Development of an automated global solarradiation network in Ohio

During 1981, Miami University and the Ohio Agricultural Research and Development Center (OARDC)cooperatively initiated the operation of eight automated, DC-powered global radiation stations which are well distributed throughout Ohio. Each station is lócated in a relatively open, grassy site at a rurally situated state or federal research facility. Personnel at each facility provide security and assistance in station maintenance. A processor-based data logger at each station scans sensors at one-minute intervals, processes the one-minute observations on an hourly and a 24-hr basis, and stores the processed data. Miami University and OARDC use telephone dial-up telemetry to collect the data at 36 and 24-hr intervals, respectively. Both have developed procedures for checking data quality, data archival, and producing summaries which are made available to individuals and organizations placing requests. Through 31 December 1981, the eight stations had collectively operated a total of 68 months. A total of just 4:5 days of global solar radiation data were lost during that period. A single data logger failure accounted for 1.5 days of that loss; the remainder resulted from modifications of the data loggers to improve data processing and retrieval flexibility. Side-by-side comparisons of the station pyranometers (Eppley PSPs) with “working standards” and inter-station comparisons of clear-day transmissivities indicate that pyranometer performance is very comparable throughout the network.     

Axial strain variations in concrete under uniform uniaxial compressive stress

This paper presents the results of an experimental study to determine the variations of axial strain in concrete under a uniform uniaxial compressive stress. Surface bonded and especially developed embeddable strain gage units are used for measuring axial strains in cylindrical concrete specimens under uniaxial compressive loads. Test results show that the axial strain decrease with the distance from the specimen face becoming uniform at a distance equal to about six times the maximum size aggregate used. These variations, reaching 40 percent in this investigation are confirmed by tests on drilled core cylinders obtained from the test specimens.     

Microstructural and chemical surface and rim zone changes of ferrite-perlite 42CrMo4 steel after electrochemical machining

Electrochemical machining is based on the anodic dissolution of most metals and generates high quality polished surfaces. However, ferrite-perlite 42CrMo4 steel reveals local optical changes at the surface after electrochemical finishing, such as a widely variable surface finish from shiny (reflective) to rough (dark) surfaces even after one processing step. The optical different surface areas of ferrite-perlite 42CrMo4 steel (AISI 4140) are studied by different electron microscopy techniques, x-ray diffraction and x-ray photoelectron spectroscopy to gain information about the local chemistry of the reaction layers and residual stresses of the rim zone. The results show that the rim zone for the different surface areas are about 50 nm–100 nm thick and contain oxygen. Selected area diffraction reveals the formation of iron(II/III) oxide (Fe₃O₄) and x-ray photoelectron spectroscopy confirms the formation of a mixed iron oxide (Fe_3-xO₄) with a variation of the oxidation state for both near-surface rim zones. Furthermore, the reflective surfaces reveal a homogeneous dissolution of ferrite and cementite lamellae whereas the rough surfaces show a preferred dissolution of cementite and an inhomogeneous dissolution of ferrite within the rim zone. X-ray diffraction measurements do not show any introduced residual stresses in the rim zone.