Numerical simulation of edge effect in plasma arc forming of sheet metal
Edge effect was found in plasma arc forming process of sheet metal, which reduces the forming accuracy of sheet metal seriously. In order to reveal the forming mechanism and forming laws of the edge effect. A numerical model on forming of sheet metal using plasma arc with scanning along a straight line was established and the forming mechanism and forming laws of the edge effect were studied. The results showed that the upper material and the lower material of the edge were produced shrinkage along the scanning path and both shrinkage were different. The size relationship of the two shrinkage determines the direction of edge warp. The difference of the two shrinkage affects the warpage of the edge. In the comprehensive effect of shrinkage and warpage, the non scanning region in the both sides of the scanning path appears bulge or depression. The numerical analysis results were agree well with the experimental results. The conclusions provide a theoretical basis to reduce the effect of the edge effect on the accuracy of the sheet metal forming.
Rapid prototyping of sheet metal components by plasma-jet forming
Abstract Conventional precision forming of sheet metal components requires the use of mechanical tools. However, during product development, different tools may be required to form various shapes, thus necessitating significant tool cost and lead time. If a rapid prototyping process were available such that the required shapes can be formed without the need for hard tools, the potential reduction in product development cost and lead time could be quite significant. Moreover, such a process could be used for very short run production where it would be uneconomical to amortize tooling cost over a small number of manufactured pieces. To explore the potential for flexible forming without tools, various researchers have used a laser beam as a heat source to induce deformation in sheet metals by means of thermal stresses. Some success has been demonstrated with such an approach. However, laser systems have several disadvantages, which can be circumvented by the use of a plasma-jet as a heat source. This paper describes the use of a robotic system to manipulate a non-transferred arc plasma torch as a controllable heat source to generate internal stress in sheet metals, thus causing plastic deformation without the necessity of hard tooling. Simple linear bends have been produced in several sheet materials of 0.8 mm thickness to evaluate the effect of various process and material parameters. Some evaluation of material properties resulting from the bending operation has been conducted. The key process parameters affecting the rate of bending have been identified as those governing the amount and rate of heat input to the sheet surface, and the temperature gradient developed between the front and back sheet surfaces. It has been demonstrated that the principal sheet metal physical property affecting bending behavior is the thermal conductivity. Results are presented to illustrate these various effects.
Nurse responsiveness to cancer patient expressions of emotion.
OBJECTIVE
This theoretically based study examined nurse responses to cancer patient expressions of emotion using a videotaped, simulated cancer patient.


METHODS
This study used an experimental crossover design with a videotaped patient expressing anger, sadness, and neutral emotion to elicit nurse responses. Seventy-four nurses from eight sites participated. Responses were coded using Roter interaction analysis system. Correlations explored relationships between variables that impact communication (age, gender, work experience, trait anxiety, work stress, self-efficacy). Regression models explored the effect of variables on nurse affective responsiveness.


RESULTS
Patient expressions of sadness elicited more affective responses than anger. Expressions of anger or neutral emotion elicited more instrumental behaviors than sadness. Variables such as age, work stress and work experience were significantly correlated. No variables predicted affective responsiveness to patient expressions of anger or sadness.


CONCLUSION
Nurse communication showed significant variation in response to patient emotional expressions. Understanding the relationships between demographic, personality, and work variables, and identification of new variables that influence nurse-patient communication, has implications for interventional studies.


PRACTICE IMPLICATIONS
Over 90% of the participants indicated that the videotape simulation would be a useful method for teaching and practicing communication skills with patients expressing emotions.