Fluid Acoustic Properties of Improved Hydraulic Mufflers with Extended Necks

The acoustic properties of three improved hydraulic mufflers with extended necks are investigated theoretically and experimentally. The effect of length and slope of the conical tube, and the perforations on the extended tube is studied on the resonance frequency and the insertion loss. The plane wave approach is used for the constant and the variable area tubes, while Sullivan and Peat's method is applied for the perforation tube unit. Theoretical predictions are compared with experiments for these three different hydraulic noise suppressors, which are fabricated. It is shown that the resonance frequency and the insertion loss characteristics may be controlled by the length and the slope of the conical tube and perforation porosity of the extended tube without changing the expansion chamber volume. Finally, the effect of the cross-sectional shape of the expansion chamber is investigated.

Pulsation Attenuation Analysis of Double-Chamber Composite Hydraulic Suppressors with Inserted Conical Tubes

A one-dimensional analytical approach is developed to predict the pulsation attenuation performance of doublechamber compound hydraulic suppressors. The theoretical insertion loss agreed well with experimental results. The need for broadband pressure pulsation attenuation has led to extensive research on the structure improvement. In the present work, the straight-through tube has been replaced by a conical tube and two improved hydraulic attenuator configurations are presented. A parametric study to investigate the effects of different parameters on the research frequencies is included as well. The validity of the models of the improved structures is demonstrated theoretically and experimentally.

Crushing analysis and multi-objective crashworthiness optimization of multi-cell conical tube subjected to oblique loading

In this article, a novel multi-cell conical tube is designed. First, a detail analysis about the crashworthiness of three structures, that is, the multi-cell conical tube, multi-cell square tapered tube, and fourfold-cell conical tube, is made and compared at the condition of keeping the same mass with different oblique load angles. Then, the influences of the internal cell walls, load angle, the cone angle, and wall thickness on the performances of crashworthiness are investigated. The multi-cell conical tube has better energy absorption capacity than multi-cell square tapered tube and fourfold-cell conical tube at small load angles. The normalization of average gradients of the cone angle on specific energy absorption reached 48.25% compared with the wall thickness. The full factorial design and the optimal Latin hypercube design method are adopted to define the sample points and error analysis points. A numerical simulation on the sample points and error analysis points are performed using Abaqus/Explicit. According to different working conditions, different optimization objects are determined, and corresponding surrogate models with different indicators are constructed using Kriging method. The accuracy of surrogate model is evaluated. The non-dominated sorting genetic algorithm-II is utilized to optimize the multi-objective problem. Finally, the influence of structural parameters on crashworthiness is discussed.

Investigation of Friction Conditions in Dry Metal Forming of Aluminum by Extended Conical Tube-Upsetting Tests

In cold forming of aluminum, various lubricants and coatings are typically used to reduce friction and wear, resulting in higher workpiece surface quality. The preparation of the workpiece surfaces and the cleaning of the products after the forming step generate a significant amount of environmentally hazardous residues. Therefore, current research focuses on the realization of dry metal forming processes. Instead of lubricants, modified tool surfaces can also optimize tribological conditions in the interaction zone of forming tool and workpiece. The applicability of these surfaces needs further examination before usage within an industrial manufacturing process. In this paper, different surface modifications are examined by using a conical tube-upsetting test setup that is based on the concept of the well-known ring-compression test. The conical tool surface homogenizes the relative displacement between tool and workpiece and suppresses the appearance of a neutral point. Conical tools from AISI H11 / DIN 1.2343 and AISI D2+ / DIN 1.2379+ are laser polished and functionalized with self-assembled monolayers. Friction conditions resulting from different surface modifications are analyzed and evaluated by the use of nomograms. Moreover, the applicability of different friction laws for dry metal forming of aluminum is investigated.