Recent Developments in LS-DYNA to close the Virtual Process Chain for Forming, Press Hardening and Welding

2015 ◽  
Vol 651-653 ◽  
pp. 1312-1318 ◽  
Author(s):  
Thomas Klöppel ◽  
Andrea Erhart ◽  
André Haufe ◽  
Tobias Loose
Keyword(s):  
Material Properties ◽  
Manufacturing Industry ◽  
Plastic Material ◽  
Base Material ◽  
Process Chain ◽  
Press Hardening ◽  
Multistage Processes ◽  
Recent Developments ◽  
Material Formulation ◽  
Virtual Process

Forming, press hardening and welding are a well-established production processes in manufacturing industry, but predicting the finished geometry and the final material properties of the processed parts is still a major issue. In particular, deformations caused by welding are often neglected in the virtual process chain, although they have to be compensated for in order to fulfill the requirements on shape tolerance. This presentation will give an overview on novel features of LS-DYNA implemented particularly for welding simulations.To begin with, new keywords will be presented that allow applying the heat generated by the weld torch. LS-DYNA offers a very convenient way to define the well-known Goldak heat source, but it is also possible to define arbitrarily shaped torch geometries.In order to obtain a predictive model for welding simulations, specific material models have been devised in LS-DYNA. The properties of filler material in weld seams are accounted for by a ghost material approach. Material is initialized as ghost material and is activated, i.e. it is given base material properties, when the temperature reaches the melting point. This approach has been implemented for a relatively simple thermo-elasto-plastic material formulation *MAT_CWM as well as for the more complex material law *MAT_UHS_STEEL. The latter has initially been implemented for press hardening simulations and is able to predict the microstructure of steel alloys including phase transformations and the resulting mechanical properties.In this contribution, details of the material formulations and novel features are presented. Examples will demonstrate how these features can be applied to multistage processes including several forming and welding stages.

Structural Integrity Research for Reactor Pressure Vessel Under In-Vessel Retention of a Core Melt

2016 ◽  
Author(s):  
Yongjian Gao ◽  
Yinbiao He ◽  
Ming Cao ◽  
Yuebing Li ◽  
Shiyi Bao ◽  
...  
Keyword(s):  
Pressure Vessel ◽  
Material Properties ◽  
Power Plants ◽  
Structural Integrity ◽  
Plastic Material ◽  
Plastic Region ◽  
Reactor Pressure Vessel ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Reactor Pressure

In-Vessel Retention (IVR) is one of the most important severe accident mitigation strategies of the third generation passive Nuclear Power Plants (NPP). It is intended to demonstrate that in the case of a core melt, the structural integrity of the Reactor Pressure Vessel (RPV) is assured such that there is no leakage of radioactive debris from the RPV. This paper studied the IVR issue using Finite Element Analyses (FEA). Firstly, the tension and creep testing for the SA-508 Gr.3 Cl.1 material in the temperature range of 25°C to 1000°C were performed. Secondly, a FEA model of the RPV lower head was built. Based on the assumption of ideally elastic-plastic material properties derived from the tension testing data, limit analyses were performed under both the thermal and the thermal plus pressure loading conditions where the load bearing capacity was investigated by tracking the propagation of plastic region as a function of pressure increment. Finally, the ideal elastic-plastic material properties incorporating the creep effect are developed from the 100hr isochronous stress-strain curves, limit analyses are carried out as the second step above. The allowable pressures at 0 hr and 100 hr are obtained. This research provides an alternative approach for the structural integrity evaluation for RPV under IVR condition.

Mechanical Event Simulation of Drop Testing for Toy Product

2006 ◽  
Vol 532-533 ◽  
pp. 993-996
Author(s):  
Anthony Yee Kai Yam ◽  
Kai Leung Yung ◽  
Chi Wo Lam
Keyword(s):  
Material Properties ◽  
Impact Analysis ◽  
Plastic Material ◽  
Free Fall ◽  
Drop Impact ◽  
Local Analysis ◽  
Element Analysis ◽  
Event Simulation ◽  
Long Time ◽  
The Impact

Toys that are free from drop failures normally take a long time to develop. It is often time and cost consuming after the production tooling is built to detect drop test failure. This paper introduces a new drop testing analysis method for Toys. The method uses a simple approach with a local analysis that based on the linear and non linear finite element analysis. Modeling and transient drop analysis of a pre-school toy is used as a case study to demonstrate the method. The impact analysis of the product hitting the solid concrete floor after a free fall is presented. The analysis focuses on the deformation of the housing for a product with electronic circuit and mechanical mechanism inside. Experimental data has been obtained for drop simulation of the housing and its correlation with the plastic material properties. The stress and strain of the housing during drop impact tests are noted. The effects of the material properties to the housing deflection under drop/impact shock have been investigated. Numerical results are compared with experimental results to validate the method.

Impact of material concentration and distribution on composite parts manufactured via multi-material jetting

2018 ◽  
Vol 24 (5) ◽  
pp. 872-879 ◽  
Author(s):  
Nicholas Alexander Meisel ◽  
David A. Dillard ◽  
Christopher B. Williams
Keyword(s):  
Material Properties ◽  
Viscoelastic Properties ◽  
Design Space ◽  
Base Material ◽  
Material Design ◽  
Mechanical Analysis ◽  
Material Composition ◽  
Significant Shift ◽  
Content Type ◽  
Property Changes

Purpose Material jetting approximates composite material properties through deposition of base materials in a dithered pattern. This microscale, voxel-based patterning leads to macroscale property changes, which must be understood to appropriately design for this additive manufacturing (AM) process. This paper aims to identify impacts on these composites’ viscoelastic properties due to changes in base material composition and distribution caused by incomplete dithering in small features. Design/methodology/approach Dynamic mechanical analysis (DMA) is used to measure viscoelastic properties of two base PolyJet materials and seven “digital materials”. This establishes the material design space enabled by voxel-by-voxel control. Specimens of decreasing width are tested to explore effects of feature width on dithering’s ability to approximate macroscale material properties; observed changes are correlated to multi-material distribution via an analysis of ingoing layers. Findings DMA shows storage and loss moduli of preset composites trending toward the iso-strain boundary as composition changes. An added iso-stress boundary defines the property space achievable with voxel-by-voxel control. Digital materials exhibit statistically significant changes in material properties when specimen width is under 2 mm. A quantified change in same-material droplet groupings in each composite’s voxel pattern shows that dithering requires a certain geometric size to accurately approximate macroscale properties. Originality/value This paper offers the first quantification of viscoelastic properties for digital materials with respect to material composition and identification of the composite design space enabled through voxel-by-voxel control. Additionally, it identifies a significant shift in material properties with respect to feature width due to dithering pattern changes. This establishes critical design for AM guidelines for engineers designing with digital materials.

Heuristic-Based Evaluation of Energy Flows in Press Hardening Process Chains

2011 ◽  
Vol 473 ◽  
pp. 816-823 ◽  
Author(s):  
Reimund Neugebauer ◽  
Frank Schieck ◽  
Angela Göschel ◽  
Julia Schönherr
Keyword(s):  
Qualitative Evaluation ◽  
Resource Efficiency ◽  
Process Chain ◽  
Press Hardening ◽  
Whole Process ◽  
Quantitative Calculation ◽  
Hardening Process ◽  
Energy Flows ◽  
Process Chains ◽  
The Press

Energy and resource efficiency is a pressing issue for technological markets in the 21st century. In the field of production technology the development of energy and resource efficient processes and process chains is of particular importance. In order to meet these needs sustainable methods and standards have to be developed. This paper presents a new procedure to calculate and evaluate the energy and resource efficiency of process chains. The method consists of 4 stages that proceed from the real world to the quantitative calculation and qualitative evaluation of material and energy flows. The method is explained and validated using press hardening process chains as an example. The procedure enables the user to systematically capture and structure the press hardening process chain and subsequently develop a comprehensive model of the whole process chain. As a result, it allows to calculate the energy requirements for each stage of the process chain, and later on the process chain as a whole. The intention of the developed procedure is to provide a tool to detect the most energy efficient variant from a range of possible process chains.

Distributed Design of Two-Scale Structures With Unit Cells

2019 ◽  
Author(s):  
Xingchen Liu
Keyword(s):  
Material Property ◽  
Material Properties ◽  
Volume Fraction ◽  
Base Material ◽  
Structure Design ◽  
Unit Cell ◽  
Steady Increase ◽  
Coarse Scale ◽  
Cell Structures ◽  
Wide Range

Abstract The use of unit cell structures in mechanical design has seen a steady increase due to their abilities to achieve a wide range of material properties and accommodate multi-functional requirements with a single base material. We propose a novel material property envelope (MPE) that encapsulates the attainable effective material properties of a given family of unit cell structures. The MPE interfaces the coarse and fine scales by constraining the combinations of the competing material properties (e.g., volume fraction, Young’s modulus, and Poisson’s ratio of isotropic materials) during the design of coarse scale material properties. In this paper, a sampling and reconstruction approach is proposed to represent the MPE of a given family of unit cell structures with the method of moving least squares. The proposed approach enables the analytical derivatives of the MPE, which allows the problem to be solved more accurately and efficiently during the design optimization of the coarse scale effective material property field. The effectiveness of the proposed approach is demonstrated through a two-scale structure design with octet trusses that have cubically symmetric effective stiffness tensors.

Tolerances and Measuring Strategies in the Virtual Process Chain for Spot Welded Structures; Substitute Modeling and Automating the Calibration Procedure

2015 ◽  
Vol 794 ◽  
pp. 3-10
Author(s):  
Patrick Ackert ◽  
Christian Schwarz ◽  
Reinhard Mauermann ◽  
Dirk Landgrebe
Keyword(s):  
Spot Welding ◽  
Computing Time ◽  
Numerical Procedure ◽  
Calibration Procedure ◽  
Welding Distortion ◽  
Process Chain ◽  
Welded Structures ◽  
Body Construction ◽  
Calibration Samples ◽  
Virtual Process

This paper presents a method with whose help it is possible, to quickly and precisely predict the influence that thermal spot-shaped joining processes has on the dimensional stability of complex component structures even in early planning phase. The welding distortion is calculated in the context of reduced computing time, based upon an experimentally calibrated mechanical substitute model. This expands existing approaches of substitute models and defines both an experimental and numerical procedure for creating adequate calibration samples. In turn, this makes use of the potential obt ained for standardizing the experimental basis for calculating and modelling the distortion to automatically carry out painstaking calibration processes in simulations and experiments in future based upon mathematical model functions. Finally, the limits to applying the substitute spot welding model are verified with reference to its predictability using a complex joining situation of a car body construction.

Sign in / Sign up

Export Citation Format

Share Document