Finite element analyses of 3D quadrilateral meshes for automotive body-in-white panels have stringent mesh quality requirements. Several mesh quality metrics, namely element included angles, minimum Jacobian determinant, skew, taper, warp, aspect ratio, minimum element length etc. need to be within acceptable limits. No constitutive relations exist that can tie all these parameters to a single metric that mesh post-processing can target. In the paper presented, a 3D optimization smoothing algorithm is proposed based on element included angles with the constraints of a minimum edge length and geometry fidelity envelope. A complex cost-function is set up for each element based on included element angle at the element corners. Element angle perturbation methods are devised to exercise local control on included angles of quadrilateral and mixed meshes. A minimization principle is worked out to reduce the cost function to an acceptable limit. Goal proximity is defined by acceptable error norms and ranges. Mesh nodes are repositioned iteratively but bound by a geometry fidelity envelope apart from the minimum element edge length constraint. Striking improvement in mesh quality statistics is reported with reasonably monotonic solution convergence patterns.
Cylindrical surfaces of many irregularities populate aerospace and automotive engine components. Many of these surfaces represent power transmitting shafts and rotary mating parts that require structured meshes to expedite contact and other finite element analyses with their mates. This poses a challenge to surface and volume mesh generators. In this paper a novel method of multiblocking based on 2D Cartesian slabs is proposed for the generation of predominantly structured meshes on irregular cylindrical surfaces. A seam generation technique comprises the first step, leading to the creation of an axial line of optimal length to split the 3D surface to facilitate 2D flattened or parametric space generation. The 2D parametric domain of the surface is next transformed to an axis-parallel local coordinate system for Cartesian slab generation. An intricate virtual face split operator is used to dissect the 2d parameter space into parallel rectangular slabs of uniform or varying thicknesses. A light-weight, mesher-native topology builder that uses virtual topological elements is proposed for constructing a virtual topology network of the slabs. Results demonstrate high quality, high fidelity transfinite-dominant meshes on a host of trimmed cylindrical surfaces.
A formula is presented for determining the net sum of mesh singularity indices that must occur in an all-quadrilateral (quad) mesh of a face or surface region after the mesh properties have been assigned on the face's boundaries and according to the face's Euler Characteristic. The formula is derived from Bunin's Continuum Theory for Unstructured Mesh Generation [1].
Acrylic bone cement is weakened by its porosity, which promotes the formation of microcracks, which contribute to major crack propagation and ultimately failure of the cement mantle. Bone cement mixing techniques play a significant role in determining the quality of bone cement produced. A high degree of porosity is found to exist in cement that is inadequately mixed. Current commercial bone cement mixing systems allow for the preparation of the bone cement under the application of a vacuum in a closed, sealed chamber by means of a repeatable mixing action. These mixing systems are perceived to be repeatable and reliable by orthopaedic community. In this paper, the quality of bone cement mixed using an operator independent bone cement mixing system was compared with that of cement prepared using commercially available devices. The results of the investigation highlighted that cement prepared using the automated, repeatable mixing regime that is operator independent demonstrated consistently better physical and mechanical properties in comparison with cement mixed using proprietary cement mixing devices. Furthermore, Design of Experiments software established the optimal factors that influenced the physical and mechanical properties of PMMA bone cement.
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
'/%3e%3cpath d='M200 752.362h200v300H200z' style='fill:%23fff;fill-opacity:1;stroke:none' transform='translate(0 -752.362)'/%3e%3cpath d='M400 752.362h200v300H400z' style='fill:%23ff883e;fill-opacity:1;stroke:none' transform='translate(0 -752.362)'/%3e%3c/svg%3e)
