Experimental Validation of a Proposed Effective Linear Variable Differential Transducer Bogie Mounting Bracket for Circle Line Trains

The Linear Variable Differential Transducer (LVDT) system plays a critical role in condition monitoring (CDM) of the Circle Line's (CCL) third rail and facilitating comprehensive network-wide visibility. However, recurring failures in the bolts attached to the LVDT Bogie Mounting Bracket (BMB) have compromised the system's intended function, impairing its availability and reliability. To address these issues, a redesign of the LVDT BMB that reduced stress concentrations, frequency resonances, and vibrations was proposed. Before live implementation, the LVDT BMB must be experimentally validated with Hammer impact tests, incremental tensile tests, and fatigue tests to evaluate the effectiveness of the redesigned LVDT BMB as compared to the existing solution. The hammer impact tests demonstrated a reduction in vibrations of 3% to 26% across eight points of incremental excitations. The incremental tensile tests revealed that the redesigned LVDT BMB outperformed the current design at all displacement levels (-1 mm to +1 mm), achieving stress reductions of 75 % to 97 % due to strategic chamfers that minimized stress concentration. Run-to-failure fatigue tests showed that the current LVDT BMB failed at 139,717 cycles (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 0.4 \text{mm}, 700 \mathrm{N}$</tex>) and 526,368 cycles (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 0.5 \text{mm}, 900 \mathrm{N}$</tex>). Attempts to recreate the forces with similar displacement values resulted in elevated forces that exceeded operational boundaries. These tests have successfully validated the redesigned LVDT BMB's resistance to fatigue failure and its potential to enhance the reliability of the LVDT BMB, reduce corrective maintenance, and increase CCL network train availability.