Extrusion Through Controlled Strain Rate Dies

The workability of a material during deformation processing is determined by (a) the die geometry which, in turn, determines the flow field during deformation, and, (b) the inherent workability of the material under the imposed processing conditions of strain rate and temperature. Most common alloys have good inherent workability and can be successfully formed over wide ranges of temperature and strain rate. Products can be successfully formed from these alloys even with dies which impose large variations in strain rate during deformation. However, many of the new alloys and composites can be deformed only in very narrow processing regimes, and control of the strain rate during deformation of such materials becomes important. For example, extrusion of a whisker-reinforced aluminum alloy composite is possible only when the strain rate is controlled to within one order of magnitude. This paper describes the development of a method for obtaining preliminary shapes of controlled strain rate extrusion dies, a special case being the constant strain rate die. The theoretical basis for such die design processes is presented, followed by some examples of die geometries. Since this design procedure ignores the material flow properties, the designed die shapes must be verified using the finite element method or physical modeling. Results of simulations with the program ALPID are also presented

Extrusion Through Controlled Strain Rate Dies

The workability of a material during deformation processing is determined by (a) the die geometry which, in turn, determines the flow field during deformation, and, (b) the inherent workability of the material under the imposed processing conditions of strain rate and temperature. Most common alloys have good inherent workability and can be successfully formed over wide ranges of temperature and strain rate. Products can be successfully formed from these alloys even with dies which impose large variations in strain rate during deformation. However, many of the new alloys and composites can be deformed only in very narrow processing regimes, and control of the strain rate during deformation of such materials becomes important. For example, extrusion of a whisker-reinforced aluminum alloy composite is possible only when the strain rate is controlled to within one order of magnitude. This paper describes the development of a method for obtaining preliminary shapes of controlled strain rate extrusion dies, a special case being the constant strain rate die. The theoretical basis for such die design processes is presented, followed by some examples of die geometries. Since this design procedure ignores the material flow properties, the designed die shapes must be verified using the finite element method or physical modeling. Results of simulations with the program ALPID are also presented

Deformation processing of an aluminum alloy containing particles: studies on AI-5 pct Si alloy 4043

Al-5 wt pct Si alloy is processed by upset forging in the temperature range 300 K to 800 K and in the strain rate range 0.02 to 200 s−1. The hardness and tensile properties of the product have been studied. A "safe" window in the strain rate-temperature field has been identified for processing of this alloy to obtain maximum tensile ductility in the product. For the above strain rate range, the temperature range of processing is 550 K to 700 K for obtaining high ductility in the product. On the basis of microstructure and the ductility of the product, the temperature-strain rate regimes of damage due to cavity formation at particles and wedge cracking have been isolated for this alloy. The tensile fracture features recorded on the product specimens are in conformity with the above damage mechanisms. A high temperature treatment above ≈600 K followed by fairly fast cooling gives solid solution strengthening in the alloy at room temperature

Chagas disease screening using point-of-care testing in an at-risk obstetric population

Congenital transmission is the most important mode of transmission of Chagas disease (CD) in non-endemic countries. Identifying CD in reproductive-aged women is essential to reduce the risk of transmitting the disease to their children and offer treatment to women and their children, which could cure the disease. We evaluated the use of point-of-care (POC) testing for CD in postpartum patients. In our patient population, 16.7% (23/138) tested positive by POC testing, but confirmatory testing was negative for all patients. Among those considered high risk, 30% declined participation. Our results suggest limited utility of the point-of-care test used in our study and identify an opportunity for improvement to broaden diagnostic testing options. Our study also highlights the need to develop strategies to increase subject participation in future research

Development of an Intelligent Apprentice System for Extrusion Die Design and Process Simulation

The costly build-and-test methods used by the experts today for optimizing extrusion die design increase lead time before production which, in turn, adversely affects operation of the aerospace factory. The success of such designs is strongly dependent upon having an experience base available. Also, the recent work on the computer aided engineering (CAE) approach to extrusion of difficult-to-extrude materials, carried out by the current investigators, reveals that the build-and-test methods are not feasible for extrusion of new aerospace alloys. To overcome these difficulties a prototype intelligent apprentice system was developed using an approach which synthesizes the available techniques from software engineering (SE), data base management systems (DBMS), operating systems (OS), and artificial intelligence (AI) to exploit the power of existing analytical techniques with the help of heuristic rules. The system offers a potential capability for prompting and aiding the design engineer in his task of finding effective solutions to complex problems. In this paper, the extrusion die design criteria and methodology, the approach and the various steps used in the development of the system, and the results of the validation are discussed. The results clearly indicate that the current engineering approach to using AI is more practical and beneficial for solving immediate problems in automation of die design than a pure AI approach

Development of an Intelligent Apprentice System for Extrusion Die Design and Process Simulation

The costly build-and-test methods used by the experts today for optimizing extrusion die design increase lead time before production which, in turn, adversely affects operation of the aerospace factory. The success of such designs is strongly dependent upon having an experience base available. Also, the recent work on the computer aided engineering (CAE) approach to extrusion of difficult-to-extrude materials, carried out by the current investigators, reveals that the build-and-test methods are not feasible for extrusion of new aerospace alloys. To overcome these difficulties a prototype intelligent apprentice system was developed using an approach which synthesizes the available techniques from software engineering (SE), data base management systems (DBMS), operating systems (OS), and artificial intelligence (AI) to exploit the power of existing analytical techniques with the help of heuristic rules. The system offers a potential capability for prompting and aiding the design engineer in his task of finding effective solutions to complex problems. In this paper, the extrusion die design criteria and methodology, the approach and the various steps used in the development of the system, and the results of the validation are discussed. The results clearly indicate that the current engineering approach to using AI is more practical and beneficial for solving immediate problems in automation of die design than a pure AI approach