Modeling dynamic anisotropic behaviour and spall failure in commercial aluminium alloys AA7010

This paper presents a finite strain constitutive model to predict a complex elastoplastic deformation behaviour involves very high pressures and shockwaves in orthotropic materials of aluminium alloys. The previous published constitutive model is used as a reference to start the development in this work. The proposed formulation that used a new definition Mandel of stress tensor to define Hill’s yield criterion and a new shock equation of state (EOS) of generalised orthotropic pressure is further enhanced with Grady spall failure model to closely predict shockwave propagation and spall failure in chosen commercial materials. This hyperelastic-plastic constitutive model is implemented as 1᨞᨟ᨠᨡ 1 1 1 a new material model in the Lawrence Livermore National Laboratory (LLNL)-DYNA3D code of UTHM’s version, named Material Type 92 (Mat92). The implementation of a new EOS that is modified to match the generalised orthotropic pressure including the spall failure is also discussed in this paper. The capability of the proposed constitutive model to capture the complex behaviour of the selected material is validated against range of Plate Impact Test data at 234, 450 and 895 ms impact velocities

Plastic anisotropic and damage evolution analysis of recycled aluminium alloy AA6061 at high rate of strain

Aluminium alloys have been widely used in many applications, and its usage is increasing yearly due to its distinctive properties. Nevertheless, it required high energy consumption and pollution during the production of primary sources. This leads to the attention in producing secondary sources to substitute the primary aluminium. Recycling of aluminium alloys adopted in automotive structures is a great option to save thousands of energy and prevent tons of CO2from being released to the atmosphere. Numerous investigations must be conducted to establish the mechanical behaviour before the specific applications can be identified. However, there is a challenge for such recycled aluminium to achieve the same application as the primary sources due to material properties degradation related to damage. It is still an open study area to be explored for a better understanding of the behaviours of recycled aluminium. Thus, in this work, the Taylor Cylinder Impact test is used to investigate anisotropic-damage behaviour of recycled aluminium alloy AA6061 undergoing high-velocity impact from 190m/s to 300 m/s using two length-to-diameter (L/D) ratios. The recovered samples are observed under an optical microscope (OM) andscanning electron microscope (SEM). A strong strain rate dependency can be seen as the damage evolution is increasing as the impact velocity increase. Further, the corresponding digitized footprints analysis exhibit plastic anisotropic and localized plastic strain in such recycled material. This can be clearly observed from the development of a non-symmetrical footprint within the impact surface. This test is the first to explore the deformation behaviour of recycled materials using high-velocity cylinder impact in a high rate of strain deformation regime

Torsion vehicle model test for automotive vehicle

Torsion vehicle model test of Simple Structural Surfaces (SSS) model for automotive vehicle sedan is proposed in this paper to demonstrate the importance of providing continuous load path within the vehicle structures. The proposed approach is relatively easy to understand as compared to Finite Element Method (FEM). The results prove that the proposed vehicle model test is capable to show that a satisfactory load paths can five a sufficient structural stiffness within the vehicle structure. It is clearly observed that the global torsion stiffness reduces significantly when only one panel is removed from the complete SSS model. The results also five a food agreement with respect to the theoretical hypothesis as the structure is less stiff in torsion in an open section condition. The SSS model and the corresponding torsion test is obviously useful to give an overview of vehicle structural integrity. It can be potentially integrated with FEM to speed up the design process of automotive vehicle

Modelling shock waves in composite materials using generalised orthotropic pressure

Excellent mechanical properties of composite materials have numerous engineering applications, especially in aerospace structures. The main characteristics are due to their strength-to-weight ratio and lowcost of manufacturing. Therefore, the understanding and an ability to predict the formation and propagation of shock waves in such materials are important. This paper investigates the ability of the constitutive model generalised for orthotropic materials to predict a complex elastoplastic deformation behaviour which involves very high pressures and shockwaves in composite materials. The formulation consists of a stress tensor formulated based on the combination between Mandel stress tensor and a new pressure generalised for orthotropic materials. The formulation is further combined with a shock equation of state (EOS) to define a new orthotropic EOS. The implementation of this newly orthotropic EOS in the Laboratory (LLNL)-DYNA3D code of UTHM’s version is presented in this paper for potential implementation in the other hydrocode. The formulation is then tested against plate impact test data of carbon fibre-reinforced epoxy composites along the through-thickness and longitudinal directions including the results obtained by Vignjevic’s model (Vignjevic et al. in J Appl Phys 104(4):044904, 2008). A good agreement is obtained in each test

Characterization of anisotropic damage behaviour of recycled aluminium alloys AA6061 undergoing high velocity impact

It is impossible to ignore the realm of the topics related recycling aluminium scraps. The recycled form of this material can be a good replacement for the primary resources due to the economic and environmental benefits. Numerous investigation must be conducted to establish the mechanical behaviour before the specific applications can be identified. In this research, Taylor Cylinder Impact tests used to investigate anisotropic damage behaviour in recycled aluminium alloy is presented. To be specific, by performing Taylor Cylinder Impact test at velocities ranging from 190m/s to 300m/s, anisotropic and damage characteristics can be observed in the samples as a function of the large stress, strain, and strain-rate gradient. The application of Taylor Cylinder Impact test as a technique to validate both the constitutive and dynamic fracture responses in such materials is also discussed. The structure of recycled aluminium AA6061 including the damage initiation and evolution are observed under optical microscope (OM) and scanning electron microscope (SEM). The results revealed that the damage evolution of the material change with the increasing impact velocity. Further, the digitised footprint analysis showed a pronounced anisotropic characteristic of the recycled aluminium AA6061