Comparison of noise generated from simplex and duplex configurations of drum brake using non-linear vibro-acoustic models

The drum brakes used on the rear wheels of automobiles have various configurations. These contribute to the differences in kinematic (geometry) and dynamic (contact, friction) aspects, eventually leading to significantly different vibration and acoustic response. This work attempts to estimate the difference in the vibro-acoustic noise generated by the drum brake's simplex and duplex variants using a combination of non-linear analytical vibration models and a numerical acoustic model. Four degrees-of-freedom lumped parameter models developed for the simplex and the duplex configurations with conformal contact predict the contact and reaction forces during braking. These forces act as the sources for the finite element based acoustic models developed for the two configurations to obtain the sound pressure to force transfer functions. The sound pressure levels are estimated by the product of the predicted forces with the respective transfer functions in the frequency domain. The sound pressure levels of the simplex and duplex drum brakes are quantitatively compared under different braking conditions, and the results are presented. It is expected that this vibro-acoustic analysis will help in designing quieter drum brakes.

Reintroduction in the Process of Operation of Worn Metal Assemblies, from the Composition of Public Transport Vehicles, Using Mechanized MIG/MAG (GMA) Welding Reconditioning, in Conditions of Guaranteeing Traffic Safety

Replacing worn or damaged parts implies high material costs and financial expense for public tram transportation services, especially for the imported units and that is why it is preferable to recondition them, taking into consideration the safety requirements. In this paper, ISIM initiatives and achievements are presented in the field of cost reduction and maintenance during operation of trams, by introduction in the operation process of worn parts, within the safety limits. Aspects are presented regarding the possibilities for reconditioning and repair of parts with a circular geometry (e.g. wheel bands, axles, drum brakes). Some of these are being applied and implemented. Also, innovative ideas are presented for increasing the performance of equipment used for reconditioning.

Sensitivity analysis and Taguchi optimization procedure for a single-shoe drum brake

Drum brakes have dominated the braking industry for many years and will most likely continue to do so for the foreseeable future due to their low cost and adequate operating performance. Basic equations for conventional brake are presented, while complicated analysis has been published using finite element methods to predict brake squeal and instability. This paper seeks to step away from the complexity of numerical models to consider the fundamental braking phenomenon of a single-shoe drum brake, using nondimensional, closed-form analysis and a Taylor series expansion to examine the effects of perturbing dimensionless design parameters. In addition, an optimal design for the conventional brake is achieved using Taguchi method. In conclusion, this paper shows that the braking torque is dependent upon only four dimensionless groups, and that two of these groups dominate the physics of braking. Furthermore, it is shown that adjustments to these two dominating groups have a direct impact on the contact pressure between that shoe material and the brake drum, and that this pressure must be kept below the yield strength of the braking material in order to prevent a mechanical failure of the brake. Since the results are nondimensional, they are generally applicable to all single-shoe drum brakes having a design with mechanical features that are similar to the one analyzed in this paper. There is very good agreement between the results of both Taguchi and sensitivity regarding the significance and insignificance of the design parameters.

Experimental Investigation and Analysis on Dynamic Strain of Leading Trailing Shoe Drum Brake

The research on the dynamic strain of drum brakes is of great significance in performance evaluation, structure optimization and fatigue prediction. Based on current research of strain experiments and measuring technology, a new test procedure is proposed to investigate strain and temperature information of a working drum. Wireless data acquisition system and high-temperature strain gauges are applied. The strain-time and temperature-time curves are studied on the conditions of emergency brake and continuous brake. A tribological and thermo-mechanical analysis are conducted by using software ABAQUS. Results show that the strain is uneven when the drum contacts different zones of friction plates. Seasonal variation is another feature and a set of four wave crests repeats during the rotation. Meanwhile, thermal effect is proved important to strain. The simulation results coincide well with experiments, proving that this method provides a practical way to verify the calculation. The study also lays the foundation for the following fatigue analysis and optimization design.