Papers by Keyword: Superposition

Abstract: Residual stress measurement techniques can be categorized as either relaxation or diffraction methods. Practitioners often advocate a particular category and sometimes a specific technique (hole drilling, contour, XRD, neutron, etc) based on their experience or capability rather than using the best technique for the particular application. This paper considers some of the implications from applying this “drunkard’s search” or “streetlight” approach by examining examples where the critical stress could be hidden from both relaxation and diffraction measurements. A better approach to planning residual stress measurements would begin with a detailed consideration of why the stresses should be measured and how the results will be used. Only then can the most appropriate measurement plan be developed. Since a single measurement technique cannot reveal the full state of stress, especially in challenging parts, the use of multiple measurement types often provides the most useful information to customers.

Abstract: The purpose of this paper is to demonstrate a) application of the contour method in measuring residual stresses in large complex geometries such as a welded pipe, b) the power of combining the contour measurement approach with other measurement methods in order to map multiple components of stress tensor in structures, c) the capability of the contour method for characterising residual stresses where there are steep gradients of stress, for example in an electron beam welded plate, and d) mapping multiple components of residual stress in thick structures using multiple cuts.

Abstract: Instead of performing the integration explicitly to calculate the magnetic field from an arbitrary shaped wire, an improved method was proposed. The magnetic field generated by a straight line segment carrying steady current was calculated based on the Biot-Savart law. The new approach is to break the wire down into a number of straight line segments in its plane. According to the principle of vector superposition and coordinate rotation, the magnetic field from the complete current wire can then be calculated by summing the contribution from each of the separate straight line pieces. The simulation results show that the proposed numerical method has high accuracy and faster computational time and is efficient and convenient to the application in projects.

Abstract: To allow better machining heat transfer through mist evaporation, a new active cooling method is proposed. It is based on variable strength activation of coolant together with active cooling. A key issue in the proposed method is the use of multiple actuators of high frequency vibration for extra strength increase. This will rely on the idea of focusing and superposition. In this project, experimental tests were conducted to test the idea for the proposed variable strength activation of coolant in precision machining. Experimental test results show that the effects of ejection distance de on the vibration sensor output amplitude Aa and output frequency fa are not significant. The output amplitude Aa has a linear relationship with the number of actuator na. The effects of na on fa is not obvious. Based on the results, the idea of using multiple actuators for focusing and constructive superposition in variable strength activation is confirmed.

Abstract: We present a suppressing technique of the antisymmetric mode by superposition of Lamb waves generated by two laser beams in a thin plate. Two Lamb waves of the same frequency propagating from the opposite direction simultaneously arrive at the point of measurement and are superposed to compose one Lamb wave. The amplitude of the superposed Lamb wave depends on the distance between two laser beams. The suppressing of antisymmetric Lamb wave mode is accomplished by selecting the distance between two beams which simultaneously satisfies the condition of the anti-node(maximum) for the symmetric mode and the minimum for the antisymmetric mode. By this method, the antisymmetric Lamb wave mode is suppressed to the degree of 1.4% of the amplitude measured at zero distance between two beams.