Pressure Stress Distributions Research Articles

Modeling and analysis of compaction roller deformation for fiber placement

The fiber reinforced resin-based composite materials have the characteristics of high specific modulus and strength, impact resistance, creep resistance, and seismic resistance, which are widely used in the aviation, automotive, and marine industries. As one of the advanced composite material forming technologies, the fiber placement can manufacture the large-curvature composite parts with the high efficiency, high quality, high repeatability and low cost. The rubber compaction roller will deform under the pressure, in which the deformation will increase the contact area between the pressure roller and the substrate, and improve the interlaminar bonding degree. Due to the different deformation of the compaction roller caused by the different laying pressures, the deformation process of the fiber compaction roller was analyzed. By establishing the pressure stress distribution model for the compaction roller, the contact pressure, the downward deformation of the compaction roller and the deformation contact area between the compaction roller and the substrate are obtained. The mapping relationship among the contact curves of the substrate is verified by using the experiments.

Characteristics of unsteady lubrication film in metal-forming process with dynamic roll gap

Based on the theory of unsteady hydrodynamic lubrication and relevant mathematic and physical methods, a basic model was developed to analyze the unsteady lubrication film thickness, pressure stress and friction stress in the work zone in strip rolling. The distribution of pressure stress and friction stress in the work zone was obtained. A numerical simulation was made on a 1850 cold rolling mill. The influence of back tension stress and reduction on the distribution of pressure stress and friction stress between the roll gaps was qualitatively analyzed by numerical simulation. The calculated results indicate that the higher the back tension, the lower the pressure stress and the friction stress in the work zone, and the largest friction stresses are obtained at the inlet and outlet edges. The pressure and friction gradients are rather small at high back tension. The pressure-sensitive lubricant viscosity increases exponentially with the increase of pressure. The unsteady lubrication phenomenon in the roll bite is successfully demonstrated.

Simulation Study and Optimization of Process Parameters in Precision Forming of the Nut Plate

For researching the stress and strain field distribution and the effect of process parameters on forming quality in the precision forming process of mid-thick nut plate, this paper builds the nut plate 3d parts of precise forming finite element entity model in ABAQUS software, and then uses Johnson-cook model to describe the material constitutive relationship and metal material damage and fracture. The ALE adaptive technology has been used to control material large deformation in finite-element analysis of elastic-plastic. Based on this model, this paper analyzes the stress and strain field distribution,average pressure stress distribution and metal material plastic flow rates distribution, and the influence of the process parameters on the forming quality in the forming process.

Three-dimensional finite element model of thoracolumbar spine with osteoporotic vertebral compression fracture

To build a three-dimensional finite element model of thoracolumbar spine with osteoporotic vertebral compression fracture (OVCF) and analyze its biomechanical change. The T10-L2 segment data were obtained from computed tomography (CT) scans of an elderly female with a single T12 OVCF. A three-dimensional finite element model of thoracolumbar spine was constructed with the MIMICS and ABAQUS software. The model was composed of bony vertebrae, articulating facets, intervertebral disc and associated ligaments. The basic stress analysis of T10-L2 motion segment was made for different material properties of bone, ligaments and facet joints contacting frictional property. The stress on the annulus fiber, nucleus pulposus, endplate and facet joints under axial pressure (0.3 MPa, 1.0 MPa, 4.0 MPa) were analyzed. A three-dimensional finite element model of human T12-L2 motion segment had 617468 elements. And the stress was higher in vertebral body than posterior structure. The distribution of pressure stresses in intervertebral disc was asymmetrical. The stress increased with a rising axial pressure. 3D finite element model of thoracolumbar OVCF and adjacent segments are successfully established. The results of stress analysis are both feasible and reliable.

Thermal and pressure stresses in cylindrical reactor pressure vessels

Transient thermal stresses and steady pressure stresses developed in long, cylindrical pressure vessels of nuclear reactors are determined analytically. The computed results of the tangential thermal and pressure stress distributions in elastic and plastic states of the pressure vessels are obtained and shown by curves. For purpose of comparison, the maximum tangential thermal and pressure stresses for different absorption coefficients (or attenuation parameters) and combined tangential thermal and pressure stresses are also found. The conditions of creep and thermal fatigue for limit design which prevent a fracture failure of the reactor pressure vessels is discussed.