Measuring Co-Axial Hole Size of Finite-Size Metallic Disk Based on a Dual-Constraint Integration Feature Using Multi-Frequency Eddy Current Testing

This paper presents a new approach of eddy current methods for determining the size of the co-axial hole in the metallic circular disk. In recent decades, for the air-cored sensor probe, the impedance change due to the presence of an infinite metal plate can be calculated by the Dodd-Deeds model. However, in practical measurements, the sample cannot match with the condition required - ‘infinite’, thus the Dodd-Deeds model could not be applied to the disk with finite size and certainly not a co-axial hole in the center. In this paper, a dual-constraint analytical method is proposed. That is, the upper and lower limits of the integration are substituted with specific values instead of the original 0 and . Besides, it is found that, once the outer radius of the disk is fixed (i.e. the lower limit of integration is fixed), the upper limit reduces linearly as the size of the coaxial hole increases. Both the FEM simulation and experiments have been carried out to validate this method. The radius of the hole can be estimated based on the dual-constraint integration feature.

Comparison Measurement of the Distance between Axes of Holes with the Roundtest RA-120 and Thome Präzision-Rapid

In this article are compared two ways of measuring axial hole distance. The first method was implemented for measuring equipment Roudtest RA 120. The second method was implemented on the device Thome Präcision.

Numerical Simulation of the Extrusion Process with Feeder Plate Die

The direct extrusion process by using a newly designed die with different angle and feeder plate numbers has been simulated to systematically investigate the effects of different geometric parameters angle and feeder plate number on the strain distribution, the load and the axial hole defect. The simulation results show that the extrusion process with multiple feeder plate die is similar to that of the extrusion for many times. The angle and feeder plate make the material flow more fluently and ameliorate the axial hole defect. The larger angle reduces the load while the feeder plate increases it. Suitable geometrical parameters can significantly enhance strain in workpiece.

Improvement of performance of bolt–nut connections, Part II: Experimental investigation

In this work, bolt and nut geometries are modified for the improvement of fatigue life of the bolt–nut connections. The modifications are aimed at reducing the stress concentration at the thread roots by factors such as reducing the shank diameter, making axial hole in bolt, stepping the nut and their combinations. The effect of modifications is studied by experiment and simulation. The experimental results show that all types of modifications considered result in an improvement in the fatigue resistance of bolt–nut connections but to different extents. However, the effects of the two latter types are more significant. The most improvement is achieved for the case when all types of modifications are combined together. In this case, fatigue life can be increased by almost 100%. Numerical results also show that all types of modifications lead to the reduction of stress concentration.