Introduction to Low-velocity impact analysis
The differentiation between low-velocity impact and high-velocity impact analyses is typically based on the speed or velocity at which the impact occurs. While there isn’t a universally defined threshold, the distinction is generally made based on the relative velocities involved and the resulting effects on the materials and structures. Low velocity impact typically refer to relatively slower and less energetic events. These impacts occur at speeds where the kinetic energy involved is relatively lower. Examples include minor collisions, accidental drops, or low-speed vehicle impacts. The velocities involved in low-velocity impacts are typically below a certain threshold, which can vary depending on the context and industry. However, it is generally considered to be within the range of a few meters per second (m/s) to several tens of meters per second.
It’s important to note that the specific threshold for differentiating low and high-velocity impacts can vary depending on the industry, specific application, or engineering standards. The context and purpose of the analysis play a significant role in determining whether an impact is considered low or high velocity. Engineers and researchers in each field establish criteria and thresholds based on their expertise and the specific requirements of the problem at hand.
Workshop 1 : Low velocity impact simulation to the hybrid core sandwich structure
Core sandwich structures are produced using face sheets made of Epoxy-Glass fiber reinforced with aluminum alloy cores. This design concept allows sandwich structures to optimize their specific bending stiffness and strength while enhancing their ability to absorb energy. To simulate the behavior of composites during impact, Hashin failure criteria has been employed. The explicit procedure is deemed suitable for this analysis, particularly when the sandwich panel experiences collapse during the impact.
Workshop 2: Low velocity impact simulation of reinforced RC slab with CFRP strips
This tutorial explores the behavior of reinforced concrete (RC) slabs strengthened with CFRP (carbon fiber-reinforced polymer) strips under low velocity impact using Abaqus software. Reinforced concrete slabs are commonly used in construction projects and are designed to withstand vertical static and dynamic loads. However, the design process often overlooks the effects of impulsive dynamic loads such as impact. The response of RC slabs to impact loading is still not fully understood, but research in this field continues due to its relevance in various applications. These include reinforced concrete structures designed to withstand accidental scenarios like rock falls, vehicle or ship collisions with buildings, bridges, or offshore facilities, as well as structures used in high-threat or high-hazard environments like military fortifications or nuclear facilities. Consequently, significant efforts have been made to develop design procedures that enhance the impact resistance and performance of reinforced concrete structures.
In this study, the concrete slab is represented as a three-dimensional component using the CDP (Concrete Damage Plasticity) material model. The CFRP strips, on the other hand, are modeled as three-dimensional shell components with elastic properties, coupled with Hashin’s damage criteria. The reinforcing bars are modeled as wire components using an elastic-plastic material model.
The simulation utilized a dynamic explicit step with surface-to-surface contact. The contact between the concrete and CFRP is treated as perfect contact, and an embedded region constraint is applied to the reinforcing bars within the concrete. Fixed boundary conditions are applied to the slab, and an initial velocity is assigned to the rigid body. The mesh used in the simulation has a positive impact on the propagation of tensile and compressive damage, as well as other obtained results.
Workshop 3 : Low-velocity impact simulation and damage assessment of glass fiber aluminum laminates
This tutorial examines the simulation of the response to low-velocity impacts and the damage mechanism of glass fiber aluminum laminates (GLARE) in Abaqus software. GLARE is a type of material commonly used in aircraft structures and is often exposed to low velocity impact events. The objective of this study is to analyze the dynamic response and damage mechanism of GLARE when subjected to single and repeated low-velocity impacts. The simulation involves the use of two aluminum plates at the top and bottom, with four glass fiber plates in the middle.
To predict the deformation and damage caused by a rigid projectile on aluminum plates, the Johnson-Cook plasticity and damage model was employed. As for the glass fiber, it was represented using engineering constant elasticity and Hashin’s damage criterion specifically for fibers. The dynamic explicit procedure was deemed suitable for this type of analysis. In the contact area, cohesive behavior was implemented to account for stiffness, damage, and tangential behavior. If the impact energy exceeds the predefined value in the cohesive contact, delamination occurs between the surfaces. It is important to have a fine mesh in the impact zone. Following the simulation, outputs such as stress, strain, damage, and other relevant data can be obtained.
Workshop 4 : Damage investigation caused by low-velocity impact on reinforced concrete beam
This tutorial examines the investigation of damage caused by low-velocity impact on a reinforced concrete beam in Abaqus. Reinforced concrete structures have been widely utilized for many years, but our understanding of their behavior when subjected to impact loads is still limited. Existing design codes employ an equivalent static approach to offer general design principles for structures under impact loads. The impact force and displacement of reinforced concrete beams can be estimated using common spring-mass models, such as single degree of freedom (SDOF) or two degrees of freedom (2DOF). In this study, the concrete beam is represented as a three-dimensional component, while the steel beams are represented as wire elements, and the projectile is modeled as a rigid body.
The steel material is represented in the model as an elastic-plastic material with ductile damage properties. When it comes to the concrete material, its modeling is crucial, but the available material models in Abaqus’ library are not suitable for accurately predicting damage and failure. Therefore, in this simulation, the Johnson-Holmquist material model is employed. For this type of analysis, the dynamic explicit procedure is considered appropriate.
The beams are implemented as embedded regions within the concrete host, and surface-to-surface contact with penalty contact behavior is utilized to define contact interactions. An initial velocity is assigned to the projectile to initiate the impact. It’s worth noting that the quality of the mesh used in the simulation significantly affects the results.
Following the simulation, valuable information such as damage, stress, strain, and load diagrams can be obtained.
- What do we learn from this package?
- Teaching plan and Prerequisites and Next steps
- Package specification
You can watch demo here.
- Introduction and problem description
- Description of modeling steps
- Result and discussion
- Introduction and problem description
- Description of modeling steps
- Result and discussion
- Introduction and problem description
- Description of modeling steps
- Result and discussion
- Introduction and problem description
- Description of modeling steps
- Result and discussion
- Introduction and problem description
- Description of modeling steps
- Result and discussion
- Introduction and problem description
- Description of modeling steps
- Result and discussion
Workshop 5: Repetitive low-velocity impact simulation on the composite panel
This tutorial focuses on investigating the effects of low velocity impact on a composite panel consisting of three glass layers and two epoxy layers using Abaqus. The three glass layers are represented as three-dimensional solid components, while the two epoxy layers are also modeled as three-dimensional solid parts. On the other hand, the rigid projectile and supporter are represented as shell components in the simulation.
In order to model the epoxy’s behavior as a cohesive material, the traction elasticity type is employed, utilizing a damage criterion known as the traction separation law. When it comes to modeling the glass behavior under impact loads, Abaqus offers several material models specifically designed for this type of simulation. Some of these material models can be accessed through a subroutine code or input file capability.
To ensure efficiency and stability in the model, the dynamic explicit step is employed, along with the mass scale technique to reduce simulation time. It is assumed that the glass and glue interfaces have ideal or perfect contact. The general contact algorithm is selected to account for all contacts within the contact domain. The bottom rigid plate is assigned fixed boundary conditions, while an initial velocity is assigned to the projectile. It is important to have a fine mesh in order to obtain accurate results.
After the initial simulation, all results, including stress, strain, damage, and failure, become available. In the second simulation, the results from the first analysis are used as the initial conditions for the second model. In this second model, the material is already damaged from the start, allowing for the observation of additional outputs.
Workshop 6: Low-velocity impact simulation on the CFRP-AL Foam-CFRP panel
This tutorial focuses on investigating the effects of low-velocity impact on a CFRP-AL Foam-CFRP panel using Abaqus. The CFRP (Carbon Fiber Reinforced Polymer) layers are represented as three-dimensional solid components, with each layer having a distinct fiber direction. The Aluminum-Foam, serving as the core part, is modeled as a three-dimensional solid component. Finally, the projectile is represented as a three-dimensional shell component in the simulation.
Foam core sandwich structures, consisting of two strong and rigid face sheets separated by a lightweight core, possess two notable advantages that make them appealing for various applications. Firstly, the core’s presence between the face sheets increases the overall moment of inertia of the structures without adding much weight. As a result, these structures efficiently resist bending and buckling loads. Secondly, they exhibit exceptional energy absorption capabilities, making them suitable for applications such as armor systems. This is attributed to the high porosity and compressibility of the foam core.
The impact characteristics of foam core sandwich structures are crucial for their implementation in structural components, as these structures are susceptible to damage from external objects during service. Metal foam structures, known for their impact-absorbing properties, can be considered as passive safety systems in transportation. They have significant potential for development as a means to reduce fatalities, injuries, and the associated economic and social impacts.
To model the CFRP material, an elastic data approach with a fail stress parameter and Hashin’s damage criterion are selected. For modeling the behavior of metal foam under impact loads, the Crushable Foam model with hardening is utilized. The dynamic explicit step is deemed appropriate for this type of analysis. Surface-to-surface contact with friction is chosen as the contact property between the rigid projectile and the upper CFRP plate. Cohesive interactions, defined by stiffness parameters and damage criteria, are employed between the CFRP sheets and the foam core. Fixed boundary conditions are applied to two sides of the panel, while an initial velocity is assigned to the rigid impactor. It is important to have a fine mesh in order to obtain accurate results.
After the simulation, various results such as stress, strain, damage, and failure of the CFRP, as well as displacement, are available for analysis.
It would be helpful to see Abaqus Documentation to understand how it would be hard to start an Abaqus simulation without any Abaqus tutorial.
Gang –
The 6 workshops are awesome!
Experts Of CAE Assistant Group –
Thanks for review!
Ottilie –
Has this tutorial package provided a detailed explanation of low-velocity impact simulation in Abaqus? I would like to learn more about the methods and practical examples in this field.
Experts Of CAE Assistant Group –
Sure. it includes step-by-step video training along with related files