Search Results

This paper presents an investigation into the behavior of spot-welded steel connections based on a DOE approach. This work is a part of spot-weld modeling methodology development work being performed at Ford. Control factors such as material, coating, gage size, and noise factors such as loading direction (angle), and speed are considered in this study. Different levels of each variable are included to cover a wide range of practical applications. The test methodology used to generate the responses for the spot-weld coupons have been discussed in a companion paper [1]. From the force-displacement curves obtained from the test, the responses such as peak force, displacement at peak force, and rupture displacement are identified. These responses are then statistically analyzed to identify the relative importance and effect of the design factors. Finally, response surface models are developed to determine responses across different levels of each variable.

The authors have proposed a new formulation to characterize the mechanical properties of spot welds under dynamic loadings including separation. In this paper, the authors primarily discuss a systematic procedure to determine the parameters of the proposed spot weld model from test data using a Design of Experiment (DOE) approach and statistical analyses. All analysis pertaining to the spot weld modeling under impact loading has been performed using RADIOSS, a commercially available explicit FE crash solver. In this study, the spot weld connection was modeled using a two-node beam-type spring element with 6 DOF at each node, and the sheet metal was modeled using a four-node shell element. The main objective was to develop a spot weld modeling methodology that is accurate and robust enough to be used in a full vehicle model which is composed of hundreds of different parts and will be crashed under different test conditions.

Specific energy absorption (SEA) is a quantitative measure of the efficiency of a structural member in absorbing impact energy. For an extruded aluminum crash can, SEA generally depends upon the topology of its cross-section. An investigation is carried out to determine the optimal cross-sectional topologies for maximizing SEA while considering manufacturing constrains such as, permissible die radii, gauges, etc. A comprehensive DOE type matrix of cross-sectional topologies has been developed by considering a wide variety of practical shapes and configurations. Since it is critical to include all feasible topologies, much thought and care has been given in developing this matrix. Detailed finite element crash analyses are carried out to simulate axial crushing of the selected crash cans topologies and the resulting specific energy absorption (SEA) is estimated for each case.

Spot welding is the primary joining method used for the construction of the automotive body structure made of steel. A major challenge in the crash simulation today is the lack of a simple yet reliable modeling approach to characterize spot weld separation. In this paper, an attempt has been made to develop a spot weld modeling methodology to characterize spot weld separation in crash simulation. A generalized two-node spring element with 6 DOF at each node is used to characterize the spot weld nugget. To represent the connection of the nugget with the surrounding plates, tied contacts are defined between the spring element nodes and the shell elements of the plate. Three general separation criteria are proposed for the spot weld that include the effects of speed and coupled loading conditions. The separation criteria are implemented into a commercially available explicit finite element code.

The present investigation details an experimental procedure for frontal impact responses of a generic steel front bumper crush can (FBCC) assembly subjected to a rigid full and 40% offset impact. There is a paucity of studies focusing on component level tests with FBCCs, and of those, speeds carried out are of slower velocities. Predominant studies in literature pertain to full vehicle testing. Component level studies have importance as vehicles aim to decrease weight. As materials, such as carbon fiber or aluminum, are applied to vehicle structures, computer aided models are required to evaluate performance. A novel component level test procedure is valuable to aid in CAE correlation. All the tests were conducted using a sled-on-sled testing method. Several high-speed cameras, an IR (Infrared) thermal camera, and a number of accelerometers were utilized to study impact performance of the FBCC samples.

Spot-welds are the primary joining methods for steel sheet metals used in the manufacturing of automobile body structure. Often the impact responses are significantly affected by the characteristic properties, such as stiffness, failure strength, etc of spot-welds. In view of this, understanding the behavior and the properties of spot-welds under static and impact loadings are critical for accurate CAE analysis of vehicle impact events. To this end, a comprehensive DOE based spot-weld testing has been undertaken by considering a wide variety of variables. The test data thus obtained were analyzed to determine the requisite mechanical properties of spot-welds as a function of the key variables such as gage, yield strengths, speed, etc. Spot-weld connections have been tested for gages ranging from 0.7 to 3.0 mm using a unique specimen configuration developed at Ford.

Spot weld is the primary joining method to assemble the automotive body structure. In any crash events some separation of spot-welds can be expected. However, if this happens in critical areas of the vehicle it can potentially affect the integrity of the structure. It will be beneficial to identify such issues through CAE simulation before prototypes are built and tested. This paper reports a spot weld modeling methodology to characterize spot weld separation and its application in full vehicle crash simulation. A generalized two-node spring element with 6 DOF at each node is used to model the spot weld. Separation of spot welds is modeled using three alternative rupture criteria defined in terms of peak force, displacement and energy. Component level crash tests are conducted using VIA sled at various impact speeds to determine mean crush load and identify possible separation of welds.