Search Results

A typical cab used on agriculture machines is made up of a metal frame structure with large enclosing panels of glass, plastic, and metal. Acoustic treatments such as coatings, textiles and foams are used within the cab for aesthetics but also to mediate undesired noise. To develop effective designs for the cab to combat noise, accurate tools for measurement, and predictive methods for sound transmission loss are needed. This paper focuses on Sound Transmission Loss (STL) of the rear upper panel of a cab used in agriculture machines. Results from CAE based tools such as Statistical Energy Analysis (SEA), Finite Element Analysis (FEA) and Hybrid FE-SEA methods are compared to measurements. The panel studied included features such as curvature, deep drawn beads with a glass window and a damping coating. The simulation results are refined by incorporating methods for accurate modeling of ribs stiffness, curvature effect and radiation efficiency by synthetic modal approach.

RADAR Sensors are going to be an integral part of autonomous vehicles. One of the main objectives of these sensors in autonomous vehicles is to get the Doppler range profile for surrounding traffic. In this paper, we use a similar RADAR for ground speed sensing in the off-highway scenario. There are several challenges in integrating the RADAR sensor with vehicles such as sensor position from ground, location on vehicle, electromagnetic interference with other electronic devices, enclosure design etc. Ground conditions and properties are also critical in the off-highway scenario for speed sensing. We propose to use the physics based electromagnetic field solvers to understand and mitigate some of these challenges and speed up the design. Electromagnetic field solvers tend to scale poorly with distance of propagation, especially in 3D modeling.

The presence of residual stresses affects the fatigue response of welded components. In the present study of thick welded cantilever specimens, residual stresses were measured in two A36 steel samples, one in the as-welded condition, and one subjected to a short history of bending loads where substantial local plasticity is expected at the fatigue hot-spot weld toe. Extensive X-Ray Diffraction (XRD) measurements describe the residual stress state in a large region above the weld toe both in an untested as-welded sample and in a sample subjected to a short load history that generated an estimated 0.01 strain amplitude at the stress concentration zone at the weld toe. The results show that such a test will significantly alter the welding-induced residual stresses. Fatigue life prediction methods need to be aware that such alterations are possible and incorporate the effects of such cyclic stress relaxation in life computations.

The demands on improving the noise, vibration and harshness of the golf mowing machines are growing rapidly. Low frequency vibrations at the human touchpoints are one of the important factors leading to the discomfort of operators on these machines. In the present work, low frequency vibrations experienced by the operator of the golf mowing machine are reduced using finite element analysis (FEA) and validated by a physical test. Initially, testing observed high vibration at the command arm, where some of the operating controls are placed. FEA was carried out on a frame level assembly and the design was iterated to affect these vibration levels. The golf mowing machine considered in this work is powered by a gasoline engine, which is the source of excitation in the current scenario. The operational forces of the engine were measured by using blocked-force transfer path analysis at its mounts. The modal frequency response analysis used these calculated forces as an input excitation.

In lightweight structures with dissimilar metal designs, structural adhesive joining is a potential joining method. Adhesives help in reducing galvanic corrosion by minimizing physical contact between two dissimilar metals. Along with adhesives, fasteners are often used as a secondary joining method to hold the assembly together during adhesive curing. Therefore, a hybrid joint which is a combination of adhesives and mechanical fasteners is potential joining method to join dissimilar metals. However, when two dissimilar metals such as aluminum to steel are joined with hybrid joint by adhesive curing at elevated temperature, the distortion of assembly is observed when cooled at room temperature. This is due to the mismatch between coefficients of thermal expansion of aluminum vs steel. The adhesive may also experience residual stress and fracture. In this study, adhesive curing induced distortion is studied using 1.1 meter-long specimens of aluminum to steel hybrid joint assembly.

Operator noise is an important aspect for noise and vibration of off-highway vehicles and a quieter cab is critical for the operator comfort. The noise level inside the cab is influenced by structural and acoustic transfer paths. In this paper, we used hybrid FE-SEA approach to consider both structural and acoustic transfer path as FEM and SEA methods individually face limitations in high and low frequencies respectively. A hybrid FE-SEA cab model was built to predict the structural and acoustic transfer functions. The analysis model was built with the systematic approach validated at each step with the laboratory test results. For the structural transfer function, structural excitations were applied at four cab mount locations and accelerations at various locations on the cab were validated. For the acoustic transfer function, the cab was excited with the volume velocity source inside the cab and sound power output of various panels were calculated and compared to the test results.

For this latest SAE Fatigue Design and Evaluation project, fatigue tests were run by loading, in bending, both welded and machined T-Joint specimens that have the same geometry. The test rig setup consisted of a horizontally mounted actuator, with pinned joints at both ends, where the load is applied to the top of the vertical leg of the “upside down T” of a T-Joint specimen, while the horizontal legs of the “upside down T” were clamped to the bedplate. Specimens were tested until failure or until the specimen was unable to carry the commanded load. They were cycled under constant amplitude (at several load levels and R ratios), block cycle, and variable amplitude loadings. Welded and machined T-Joint specimens of the same geometry were included in the test plan such that fatigue life predictions could be compared to test lives for each case. Those comparisons would demonstrate the methodology’s relative predictive ability to manage welds, residual stress, etc...

A new total fatigue life methodology was utilized to make fatigue life predictions, where total fatigue life is defined as crack initiation and subsequent crack propagation to a crack of known size or the component’s inability to carry load. Fatigue life predictions of an A36 steel T-joint geometry were calculated using the same total fatigue life methodology for both welded and machined test specimens that have the same geometry. The only significant difference between the two analyses was the inclusion of the measured weld residual stresses in the welded specimen life predictions. Constant amplitude tests at several load levels and R ratios were analyzed along with block cycle and variable amplitude loading tests. The accuracy of the life predictions relative to experimental test lives was excellent, with most within a factor of +/- two.

The Society of Automotive Engineers Fatigue Design & Evaluation Committee [SAE FD&E] is actively working on a total life project for weldments, in which the welding residual stress is a key contributor to an accurate assessment of fatigue life. Physics-based welding process simulation and various types of residual stress measurements were pursued to provide a representation of the residual stress field at the failure location in the fatigue samples. A well-controlled and documented robotic welding process was used for all sample fabrications to provide accurate inputs for the welding simulations. One destructive (contour method) residual stress measurement and several non-destructive residual stress measurements-surface X-ray diffraction (XRD), energy dispersive X-ray diffraction (EDXRD), and neutron diffraction (ND)-were performed on the same or similarly welded samples.

The fatigue properties of gray cast iron are presented. Included in these properties are monotonic tension and compression data and cyclic strain control fatigue data. Estimations of fatigue properties determined from the measured fatigue data are compared to predicted fatigue properties based on static properties. Samples with average hardnesses of 171 and 213 Bhn iron were tested and the results compared. The results of this investigation revealed that the strain amplitude cycles-to-failure plot of gray cast iron was independent of hardness of the iron.