Method to Increase the Accuracy of Large Crankshaft Geometry Measurements Using Counterweights to Minimize Elastic Deformations

Large crankshafts are highly susceptible to flexural deformation that causes them to undergo elastic deformation as they revolve, resulting in incorrect geometric measurements. Additional structural elements (counterweights) are used to stabilize the forces at the supports that fix the shaft during measurements. This article describes the use of temporary counterweights during measurements and presents the specifications of the measurement system and method. The effect of the proposed solution on the elastic deflection of a shaft was simulated with FEA, which showed that the solution provides constant reaction forces and ensures nearly zero deflection at the supported main journals of a shaft during its rotation (during its geometry measurement). The article also presents an example of a design solution for a single counterweight.

Virtual Model of Gear Shaping—Part II: Elastic Deformations and Virtual Gear Metrology

Elastic deflection of cutting tools relative to the workpiece is one of the major factors contributing to dimensional part inaccuracies in machining. This paper examines the effect of tool deflection in gear shaping and its effect on the gear's profile form error, which can cause transmission error and noise during gear operation. To simulate elastic tool deflection in gear shaping, the tool's static stiffness is estimated from impact hammer testing. Then, based on simulated cutter-workpiece engagement and predicted cutting forces, the elastic deflection of the tool is calculated at each time-step. To examine the effect of tool deflection on the profile error of the gear, a virtual gear measurement module is developed and used to predict the involute profile deviations in the virtually machined part. Simulated and measured profile deviations were compared for a one-pass external spur gear process and a two-pass external spur gear process. The simulated profile errors correlate very well with the measured profiles on the left flanks of the workpiece teeth, which are cut by the leading edges of the cutter teeth. However, additional research is needed to improve the prediction of the right flanks, which are cut by the trailing edges of the cutter teeth.

Electrostatic pull-in analysis of a nonuniform micro-resonator undergoing large elastic deflection

Pull-in analysis of an electrostatically actuated nonuniform micro-resonator under large elastic deflection has been investigated with a focus on qualitative analysis to understand the essence of nonuniform cross-section on the determination of pull-in voltage. Here, a microcantilever beam with nonuniform cross-section has been adopted to develop a mathematical model considering the important features such as structural nonlinearities, nonlinear electrostatic distribution, and linear viscous effect. The individual effect of each design variables on the diagnosis of the critical voltage and corresponding critical deflection due to pull-in has been graphically depicted. The results in the static condition have been verified with the findings obtained via COMSOL multi-physics software. Present result indicates that a nonuniform microbeam configuration strengthens the structural stability by switching the pull-in voltage up to a higher value. Similarly, stable pull-in deflection within the restriction of pull-in instability has been also augmented. In addition, it has been shown that the nonuniformity within the beam structure is highly sensitive to the nonlinear effects. Hence, outputs provide a useful insight of pull-in behavior and enable an understanding of safe and smooth operating range of microelectromechanical system devices.

Mathematical Models for Interrelation of Characteristics of the Developing Defects with the Parameters of Acoustic Emission Signals

Mathematical models and mechanisms of acoustic emission signal generation are presented. It is shown that the reasons of acoustic emission signal origin are related to the local alterations of microstructure of materials and processes of movement of distribution at formation of tensions in solids. It is proved that the origination of signals is based on the analysis of acoustic wave energy released per load cycle and the work of the external forces at elastic deflection.