ABAQUS – Advanced use Element and Node Sets Shear Locking in solid elements Reduced Integration and Zero Energy Modes Sign Convention Integration Schemes Shell Elements – pitfalls to avoid Beam Elements General Suggestions

ABAQUS CAE - Modules PART Create part using Sketcher SKETCH sketcher ASSEMBLY Creation of instances and assembly. PROPERTY Define Material, SECTION Properties and ASSIGNS it. STEP Analysis Steps INTERACTION Interaction Properties, Constraints. Contact between 2 surfaces, LOAD Loads, Boundary Conditions and Fields. MESH Choice of element JOB Creates Job, associates job with a MODEL VISUALIZATION Post processing

Sign Convention Displacements and point loads are positive in the direction of the positive axes. Normal Stresses – Tensile stress is +ve. Shear stress – anticlockwise about element centre is +ve. Direct strains – Tensile stress is +ve Soils consolidation  ’  u

Stress Discontinuities Stresses are calculated accurately at Gauss (Integration) points. Displacements are continuous across element boundaries. Stresses jump across element boundaries.

Shell Element - Normal The direction of the +ve normal is defined by the nodal sequence and the Right hand rule. The section points are numbered in the direction of the +ve normal. The section points identify the sections.

Parts and Instances Parts are the master components. These are not directly assembled. Instances are the copies of parts which make up the assembly. In the plate example the plate is the only part and is named – Part-1 Instance is a copy of the Part. It is the instances which form the assembly. If there is only a single part then the assembly consists of just the instance of the single part.

What is the need for Instances? One might ask why there is a need for instances? Why not just have part (or parts) Which are assembled into the assembly? (a)Instance in addition to containing all the information of the Part has information about its positioning in the assembly (using a translation and rotation vector). (b) If the assembly contains multiple copies of a component (Part) then this is facilitated by having multiple instances of the part.

Example of Instance *Part, name=L-Plate *Node 1, 15., 0., 30. 2, 15., 0., 0. … *Element, type=C3D8R 1, 577, 404, 461, 576, 2417, 2244, 2301, 2416 …. *End part …….. ** ** ASSEMBLY ** *Assembly, name=Assembly ** *Instance, name=L-Plate-1, part=L-Plate *End Instance ** *Instance, name=L-Plate-2, part=L-Plate 65., 30., , 30., 0., 65., 30., 1., 180. *End Instance **

Example of Instance *Part, name=L-Plate *Node 1, 15., 0., 30. 2, 15., 0., 0. … *Element, type=C3D8R 1, 577, 404, 461, 576, 2417, 2244, 2301, 2416 …. *End part …….. ** ** ASSEMBLY ** *Assembly, name=Assembly ** *Instance, name=L-Plate-1, part=L-Plate *End Instance ** *Instance, name=L-Plate-2, part=L-Plate 65., 30., , 30., 0., 65., 30., 1., 180. *End Instance **

Parts and Instances By default instances are dependent entities. Instances then inherit all the properties from the part (Example : mesh section and material properties). However it is possible to make the instance independent when the instance is created. Then the instance can be meshed separately and assigned properties independent of the part. (Example : two parts have minor differences).