Papers by Keyword: LS-DYNA

Abstract: Geopolymer, with its notable benefit of low carbon dioxide emissions, holds the potential to substantially curtail environmental pollution. According to the existing related research on geopolymer materials, it is obvious that it has great development potential in many engineering application fields, and it is a new generation of green and environmentally friendly recycled materials. Nowadays, there is a growing concern regarding explosion protection. Explosions near buildings can cause catastrophic damages on the building external and internal structure, and the most important thing is that can cause injuries and loss of life to the occupants of these buildings. This study investigates the mechanical performance of the fiber-reinforced geopolymer concrete under explosive testing. Furthermore, the finite element analysis models have been established through LS-DYNA software to simulate the explosive testing using Structure-Arbitrary Lagrangian Eulerian Method (S-ALE). The model is used to assess the dynamic mechanical behavior of geopolymer materials.

Abstract: Warm deep-drawing of pre-aged (under-aged) blanks of 7xxx series aluminum alloys (Al-Zn-Mg) at moderate temperatures of roughly 120–230°C is a promising route for producing parts with considerable geometrical complexity, good paint bake hardening response, and, thus, excellent final mechanical properties. Furthermore, oil-based lubricants can be used, eliminating the need for elaborate cleaning routines. However, finite element (FE) simulation of the process is challenging: time-temperature regimes during coupon testing for material cards should closely follow the real conditions in the press because the material undergoes significant changes at warm-forming temperatures, such as recovery and precipitation/coarsening/reversion of hardening phases. When convective heating is used for Nakajima or tensile testing, heating rates are usually too low to adequately represent real process conditions (where inductive or contact heating may be used). Here we present a method for establishing FE material cards and calibrating the GISSMO damage model using miniaturized tensile specimens for a dilatometer with inductive heating. The simulations are compared with warm deep-drawing experiments of pre-aged 7xxx and good agreement of minimum draw temperature for two alloys is achieved. The findings are discussed with regards to transmission electron microscopy investigations and final mechanical properties published earlier. It was found that warm-forming is suitable to produce complex 7xxx parts with high final strength. Conditions in the press can be represented by using miniaturized tensile specimens and inductive heating for calibration of material cards/damage models.

Abstract: Single point incremental forming (SPIF) is a choice of interest in many manufacturing industries due to its wide range of applications. Materials such as copper, aluminum, steel, and many others formed various complex shapes through this process. However, the forming process could sometimes result in process defects, which could strongly influence the formed parts' geometric accuracy. The twist defect is one of them, which incrementally twists the forming sheet with a small angle at each forming step. In this paper, twist phenomena in the SPIF process have been investigated both numerically and experimentally. In the experiment, Aluminum Alloy (AA5052) was used to form a truncated pyramid shape, and a room temperature tensile test has been conducted to achieve the material's tensile properties. Then, the material property used in the simulation study of the SPIF using LS-DYNA software, where twist defect, stresses, strain, and thickness distribution are studied. The results from simulation and experiment show significant similarity against the expected results and this conveys that the proposed FE model of the SPIF process can be used to investigate the presence of twist, distributions of stress and strain, and thinning locations in the formed part.

Abstract: FRP laminates are used in several industries such as automobile, aircraft’s, spacecraft’s, defense and etc.., where high strength-to-weight ratio is the primary criteria. FRP laminates offer high design and material tailoring properties but are highly susceptible to delamination and debonding under out-of-plane low velocity impact which induces barely visible impact damage (BVID) inside the structures. A lot of research investigation is going on related to damage resistance behavior of FRP laminates under out-of-plane impact loading. But very less concentration is paid to the FRP laminates behavior under in-plane low impact loading. In this numerical analysis in-plane low velocity impact loading is carried out on a bidirectional plain woven glass fiber reinforced epoxy laminate (GFRP) using LS-DYNA. A hemispherical impactor of mass 5kg and diameter of 10mm is impacted at 0.5, 1.0 and 1.5m/sec velocity on [(0⁰/90⁰)/(+45⁰/-45⁰)/(+45⁰/-45⁰)/(0⁰/90⁰)]_S layup design. Two boundary conditions complete edge and corner constraining boundary conditions are considered for numerical analysis. Force vs. time, energy vs. time, displacement vs. time plots are used to evaluate the analysis.

Abstract: Braided composites have been widely used in aerospace and automotive structures due to their light weight and high strength. Unlike metal or laminated composite material, the complex braided structure brings a lot of challenges when conducting numerical simulation. In this paper, a finite element analysis based meso-mechanical modeling for the two dimensional triaxially braided composite was developed. This mesoscale modeling method is capable of considering the detailed braiding geometry and architecture as well as the mechanical behavior of fiber tows, matrix and the fiber tow interface. Furthermore, a multiscale model combined both macroscale and mesoscale approaches and it is realized within LS-DYNA environment through Interface_components and Interface_linking. This combined multiscale modeling approach enables the full advantage of both the macroscale and mesoscale approaches, which can describe the details of local deformation and the global overall response features of the entire structure with the minimum computational expense. The evaluation and verification of the mesoscale approach and combined multiscale modeling method is through a notched coupon tensile tests conducted by Kohlman in both axial and transverse direction. The multiscale modeling method captures the response feature accurately so it has the ability to analyze large scale structures.

Abstract: This study compared the ballistic performance of alumina (Al₂O₃)/ zirconia (ZrO₂) functionally graded material (FGM) specimens with various levels of thickness and ZrO₂ content and a pure Al₂O₃ single-layer ceramic composite (PCM). Ballistic tests were conducted with 0.3-inch armor-piercing (AP) projectiles, and finite element code LS-DYNA was used to examine energy absorption, stress distribution, and ceramic cone failure in the specimens. The findings are as follows: First, regarding energy absorption per unit of areal density, the 5% FGMs had the highest ballistic performance, which increased by up to 8%. By contrast, the ballistic performance of the 15% FGMs declined significantly to lower than that of the PCM. Second, the capability of the ceramic cone to withstand stress damage and projectiles was significantly greater in the 5% FGMs than in the 15% FGMs. Third, the wave impedance variations increased with the ZrO₂ content in each layer, thereby enhancing the interactions between impact waves and aggravating ceramic damage. Thus, the intensities of transmission and reflection waves in the 15% FGMs increased, thereby causing reductions in its ballistic performance.

Abstract: In this paper, in-plane dynamic crushing test of E-Glass hexagonal array systems has been carried out numerically, using LS-DYNA FE software package. Two array systems of woven E-Glass/epoxy hexagonal were studied; single column array system and multi-column array system. The volume of material used in all models was constant. The significant effects of changing arrays’ sequences and number of E-Glass layers in the hexagonal cells on the energy absorption capability are investigated. To validate the FEM, a single 45º hexagonal was modelled and crushed in X1 direction; the obtained numerical results were compared with the experimental results in terms of energy absorption capability, deformation modes and load-displacement curves, showing good agreement. Results obtained from single column array system showed that 1×4 array exhibited the higher energy absorption capability, whereas in multi-column array system, 4×3 array had the maximum value of energy absorbing compared to the whole studied models in this paper. As a conclusion, the multi-column array system has a higher energy absorption capability compared to the single column array system.

Abstract: The mechanical response of a middle strength rock, namely Pietra sandstone, is assessed both numerically and experimentally under unconfined compressive loading condition. Two experimental approaches, based on different specimens’ arrangements, have been conducted on Pietra Serena sandstone to determine its unconfined compressive strength (UCS). This parameter greatly influences the boreability of rocks and a precise method for obtaining this parameter is thus always required. The experimental tests have been replicated in LS-DYNA in conjunction with an advanced material model, called the Karagozian and Case Concrete (KCC) model, to benchmark the results and, therefore, to conclude which experimental approaches yield the most reliable results.

Abstract: The capability of the explicit numerical methods to simulate accurately the real cutting process is investigated in this research work. Smoothed particle hydrodynamics - SPH, classical Lagrangian finite element method - FEM and Multi-Material Arbitrary Lagrangian Eulerian - ALE methods are chosen for the modeling and simulation of the orthogonal metal cutting process of AISI H13 in LS-DYNA. The cutting tool is modeled as a rigid FEM body that incrementally penetrates into the flexible deformable workpiece. At each numerical model, the dynamic elastoplastic behavior of the workpiece material is investigated by taking into account the Johnson-Cook (J-C) constitutive strength material model. The influence of the J-C parameter values found in literature to the models is explored. The obtained numerical SPH, FEM and ALE results of the estimated cutting and thrust forces, stress, plastic strain and thermal distributions are compared with results found in the literature. This comparison, leads to valuable conclusions for the performance of the three methods, concerning the approximation accuracy, model development complexity and computational time demands. Based on these conclusions the SPH method is chosen to simulate the experimentally performed orthogonal cut of AISI 1045. The obtained SPH numerical results outline its advantages among the other explicit simulation methods.

Abstract: Steel Corrosion affects severely on the life and durability of RC structures. In order to investigate the relationship between partial corrosion of RC beams and its cracking morphology and flexural capacity, based on experimental data, RC partial corrosion beam models are simulated using finite element software to model the flexural cracks and capacity of corroded RC beam under different corrosion rates. The results of compared analysis with experiment are presented: with the increase of the corrosion rate, the cracking region is almost consistent, the number of cracks reduces gradually, crack spacing becomes more unequal, bending stiffness and yield strength greatly reduce, ultimate flexural capacity and energy absorption capacity deteriorates, numerical simulation results are in good agreement with experiment.