WJ TOC 2005-09-toc
 September 2005FEATURES How to Avoid Cracking in Aluminum Alloys The majority of aluminum base alloys can be successfully arc welded without cracking-related problems; however, using the most appropriate filler alloy and conducting the welding operation with an appropriately developed and tested welding procedure are significant to success. In order to appreciate the potential for problems associated with cracking, it is necessary to understand the many different aluminum alloys and their various characteristics. Having this advance knowledge will help avoid cracking situations. The Primary Reason Aluminum Welds Crack There are a number of cracking mechanisms associated with the welding of metallic alloys. T. Anderson Update: Using Transparent Welding Curtains Welding and cutting arcs produce ultraviolet, visible, and infrared radiation, which together are known as optical radiation. It is now known that the most important optical radiation parameters associated with welding/cutting events are the length of time a person views the arcs without any protection, the magnitude of the welding current, the distance from the arc, and the intensity of the optical radiation exposure. Awareness of these parameters is why welders wear eye and skin protection such as gloves, tinted welding shades, helmets, etc. Personnel other than welders — for instance, people just passing by — could be protected by surrounding the immediate welding/cutting area with an opaque enclosure. Historically, these enclosures were made of opaque canvas or, in some cases, black-painted wood or metal partitions. D. R. Wilson Delayed Cracking in Multipass Welds Hydrogen-induced cracking is a significant problem that often arises after welding of steels. It can occur long after the weld has cooled to ambient temperature since hydrogen cracks do not form above 200°C. The delay in crack formation is due primarily to the rate of hydrogen diffusion through the weldment, preferentially to high stress locations. The rate of hydrogen diffusion (movement) is a function of the steel’s microstructure and temperature, with slower diffusion rates observable at lower temperatures. This delay phenomenon makes it particularly difficult to schedule weld inspection intended to ensure structural integrity, as one would not want to inspect the weld and then later find that the weld had cracked. R. Lazor et al. Work Cell Safety Begins at the Borders Automation is on the increase in industry, and with this increase is a growing need to prevent workers from entering a potentially dangerous automated cell. Although an automated machine can be safeguarded with walls or fences, or mechanical guards with safety interlock switches, at least one side or entrance must still be guarded with a nonphysical barrier to allow quick access when a malfunction or part jam occurs — Fig. 1. Safety Light Curtain vs. Infrared Perimeter-Access Guard Nonmechanical safety devices such as infrared perimeter-access guards and safety light curtains are two choices for barrier protection. Safety light curtains are designed to protect operators from material positioning or other hazardous processes, often referred to as point-of-operation guarding. B. Wheeler Robot Boosts Productivity for Custom Bike Builder When 17-year-old Randy Simpson first tinkered with an old Harley-Davidson® Panhead in the Virginia backcountry town of Lynchburg, he never imagined the hobby would elevate him to celebrity status with his own television series 30 years later. Simpson’s fame and popularity didn’t hatch overnight, though. It grew steadily throughout the years and so, too, did demand for his custom motorcycle parts produced by hand in his hometown shop, Milwaukee Iron. But with fewer than a dozen employees, Simpson eventually needed to speed production to keep up with demand — and he needed to do it without increasing labor costs. The solution was a small robot capable of welding and cutting thousands of custom fenders each year in a fraction of the time his employees could. When Simpson made the move, productivity jumped 300%, he noted. Protecting Welders from Head to Toe The two types of materials most commonly used in welder protective apparel are chrome tanned leather and specially treated flame-resistant cotton. Leather is durable and will last several years if dry cleaned regularly after the garment becomes noticeably stiffened from accumulated dirt and grime. Treated-cotton garments come in a range of material weights, allowing the welder a variety of choices. To work in hot environments, welders can select a lighter-weight material, otherwise they can opt for a heavier-weight, more-durable garment. All but the most inexpensive treated- cotton garments can be laundered using normal temperatures and cycles without affecting the flame-resistant treatment. Selecting the Proper Wrist Support Supplementing an ergonomics program with wrist supports can be an important step toward helping to reduce the stress and pain associated with repetitive wrist motions. Selecting the proper wrist support is even more important to obtain essential support and comfort without compromising dexterity, flexibility, or productivity. It is estimated that people may flex their wrists as much as 5000 times in the course of a normal workday. The repetitive downward and upward, and side to side motions the wrists endure can result in pain and stiffness. Over time, the stress and strain may result in more serious injuries such as carpal tunnel syndrome and tendinitis. Designing Joints for Ultrasonic Welding of Plastics Ultrasonic welding of components has become an important joining process in the automotive, electrical, medical, consumer appliances, and toy industries owing to its flexibility in product design. As a result, extensive research work is carried out on joint design, horn design, product design, energy utilization, and interaction of the material (base material) with the ultrasonic waves. Research on joint design has been concentrated on the ideal joints suitable for a particular type of thermoplastic material, as is evident from the literature survey. But it seems that there is no comprehensive information available on the joints used by industry and the reason for arriving at those joint designs. This article discusses some on the joints used by industry in welding molded thermoplastic parts. M. R. Rani, K. Prakasan, and R. Rudramoorthy WELDING RESEARCH SUPPLEMENT *Influence of Procedure Variables on C-N-Mn-Ni-Mo Metal Cored Wire Ferritic All-Weld Metal (.pdf) Different shielding gases, welding position, number of weld passes, and arc energy were all studied to assess their influence on the all-weld-metal properties of a metal cored filler metal N. M. Ramini DE Rissone et al. |
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