Creating Intrusion in Engineering Using Hypercrash and Hypermesh

Altair HyperCrash® is an application of highly tuned pre-processing technology focused on automating the creation of high-fidelity models for crash analysis and safety evaluation. It provides an exhaustive and procedure-oriented toolset to improve and simplify the complex problems of creating a quality crash model.

• Pre-processor for the creation of high-fidelity models for vehicle crash analysis and safety evaluation
• Management of highly complex models (sub-modeling and files)
• Dummy positioning, seat belt routing, and seat deforming
• Airbag folding, including reference geometry generation
• Mesh quality module, model, and penetration checker

This article will discuss how Hypercrash and Hypermesh can help us with such simulations and produce meaningful results. 

What is Intrusion in Engineering?

In the field of automotive engineering, footwell intrusion describes a situation in which an automobile engine or other vehicle component penetrates the space normally allocated for the feet of the front seat occupants. Automotive crash testing agencies such as Euro NCAP and IIHS consider levels of footwell intrusion when conducting assessments. Vehicles that display excessive deformation of the footwell are screened and redesigned. 

Intrusion determines how much a part protrudes toward a particular location. If we take the dashboard intrusion of a car, we want to find out how far the dashboard will get intruded towards the passenger during a collision. This will account for the safety of the passenger, and severe injuries can be avoided.

Safety Rules And Regulations:

Numerous articles pop up daily describing how a new car model from popular companies like FORD, TATA, MAHINDRA, and TESLA has received a 5-Star rating. On the flip side, you may also have noticed that some of the top companies have been ordered by NHTSA to recall their models for violating compliance rules and regulations with regard to passenger safety standards.

What does it mean when a car receives a 5-Star rating?

According to the NHTSA, using crash test results, the 5-Star Safety Ratings programme assesses how well-built a vehicle is. Because these make up the majority of crashes on American roads, NHTSA performs frontal, side, pole, and rollover tests.

Like American car manufacturers, the Bharat New Vehicle Safety Assessment Program (BNVSAP) is a proposed New Car Assessment Program for India. Following the footsteps of Global NCAP, BNVSAP has laid out a new structure for Indian Car manufacturers to follow to harmonize India's vehicle safety standards with global standards. 

The Global New Car Assessment Programme (Global NCAP), in a nutshell, has adopted the vision of “long-term aspiration for a world free from road fatalities and serious injuries,” with its mission statement as “To promote vehicle safety technologies with proven effectiveness and encourage their accelerated use across the globe.” 

The Role Of FEA in Predicting Intrusion in Engineering

The automotive industry needs to design and develop new car models faster than ever because of increasing competition and customer demand. In the automotive industry, predictive technology such as Finite Element Analysis (FEA) has become the must-have tool to predict a car's performance during the early design stage. The benefits of predictive tools include:

• Reducing product development time
• Reducing the number of design cycles
• Eliminating a large portion of physical testing

Let’s explore how the procedure for defining a dashboard intrusion for the frontal crash will be demonstrated using Hypermesh and Hypercrash. It is assumed that the rest of the  Boundary Conditions and Analysis settings have been set to perform Frontal Crash simulation.                          

There are three methods that have been discussed. The first method is to create a skew and a node to discover the intrusion, and the second is to create a spring element. The above-mentioned methods are performed pre-processing part of FEA. The third method is performed in the Post-processing phase using the Measure option.

But first, we must also know about the protocol guidelines in order to decide what a violation is against the rules and regulations. According to Protocol guidelines published on the GLOBAL NCAP website for automotive manufacturers, upon its impact on Frontal Crash Test, the car model has set some Criteria and Limit Values as mentioned below. Refer to the document “ADULT FRONTAL IMPACT OCCUPANT PROTECTION ASSESSMENT” for more detailed information. The important points required here are summarized below as:

3.1.6 Foot/Ankle

Higher performance limit Pedal rearward displacement is 100mm

Lower performance limit Pedal rearward displacement is 200mm

Notes:

1. Pedal displacement is measured for all pedals with no load applied to them.
2. If any of the pedals are designed to release from their mountings during the impact completely, no account VERSION 1.0 - AUGUST 2017 6 is taken of the pedal displacement provided that release occurred in the test and that the pedal retains no significant resistance to movement is taken of the pedal displacement provided that release occurred in the test and that the pedal retains no significant resistance to movement.
3. If a mechanism is present to move the pedal forwards in an impact, the resulting position of the pedal is used in the assessment.
4. The passenger’s foot/ankle protection is not currently assessed.

Defining Intrusion in Hypermesh

According to Hypermesh Radios, Handbook guidelines, Skew is one type of reference coordinate system that helps define local quantities w.r.t to the global coordinate system. Here the origin of the skew remains in a fixed position even if it is a fixed or moving skew. In a moving skew, the orientation of the node of interest is recomputed every time with that of the origin coordinates of the skew. To find out intrusion 2 nodes are created, and moving skews are assigned to them. There the travel of the node is computed from global coordinates and presented in the local coordinates. Thus overall travel of the node of interest is obtained.

Creating Skew

Right-click in the solver tab > Skew > Move.

Now the tab will be opened where we need to define the origin and the planes.

The first node we select defines the origin, and the other two can be selected accordingly. For example, if I want to make the skew similar to the global coordinate as shown in the figure below,  where the y-axis points towards the left and the x-axis point toward up, I will select the origin first, and then I will select the node at the top to follow the y-direction and the node at the top of the origin as my x-axis. There is no need to follow the global axis as we define the local coordinate here. For a better understanding of these concepts, I have mentioned them here. Similarly, you will have the option to define the skew with respect to the z-axis and y-axis selection. The choice will totally depend on the user as long as he keeps a record of it and interprets results accordingly. 

To define the intrusion, create a new output block, rename it Intrusion, and specify the skew and the node required.

If a node id is given, it can be defined directly by specifying the node number.

It should be noted that the option to define the skew will be visible only after defining the nodes.

With this, we finish a simple method to define the intrusion.

After running the simulation, we get the distance between the skew and the node from the T01 graph that's been displaced, and the intrusion of the node can be found by deducting the final distance from the node and skew to the initial distance between the node and the skew.

Defining Intrusion in HyperCrash

Creating Skew

Right-click on the Browser page > Create new > System > Skew.

Put the cursor on the coordinates of origin and give a right-click. Use the pick node option and specify the origin.

To specify the X-axis coordinated, Use the “Along vector N1-N2 option.

Make the selection as shown below.

The same option can be used to define the Y-axis coordinates. With this, a skew has been created, as shown below. To view the skew tick the skew box under the system.

Now It should be called into the data history. To create a data history Right-click on the browser page > D-H > Data history > TH of nodes. From here, specify the node id mentioned in the question and the skew we have created.

With this, we have defined intrusion in Hypercrash.

The other method to find out the intrusion is to create a spring element between two nodes and we will be getting a direct value for the intrusion from the T01 graph in the form of elongation.

Hypermesh

A node has to be identified as per the given question and this can be done using the temp node option and thereby specifying the node id to it. The second point can be chosen as it will be aligned in a straight line on the cross member. Also, a new component has to be created to organise the spring into that collector when it has been created. Rename the collector as spring.

A spring element can be created in 1D panel > Springs >Select the two nodes where we need to measure the intrusion.

Now a new property card for the spring has to be created.

Select the card image as P4_SPRING.

Assign a value of 0.001 N/mm to the stiffness(K1)  and mass in the card.

Now, this property has to be assigned to the component that's been created earlier.

Now, these have to be called into the output block. This can be done by creating a new output block, renaming it as intrusion, changing the Entity IDs to element, and selecting the spring that was created.

Hypercrash

 

Right-click on the browser page > Create New > Property > Line > Spring and rename the card as Spring_Intrusion.

Assign a value of 0.001 to the stiffness(K1)  and mass in the card.

Now to create a spring go to Mesh Editing > Element > Create.

Rename the part as intrusion and click ok. Now choose the element type as spring and a window will open where we need to select the property (Spring_intrusion) that we have defined and click ok.

Finally, select the nodes and click save. If we have the specific node id, we can initially highlight the node from the tool shown below.

Now, after selecting, we have created the spring that's required to find out the intrusion.

Now, these have to be called in data history; that can be done by right-clicking to the browser page > Create New > Data history > TH of springs.

Select Eid and then click Save.

A sample image of the plot of the Resultant Elongation Experienced by spring element is shown below. The Graph can show exact data on how the elongation is created along the simulation timeline.

Hyperview-Measurement

Another method to measure the displacement would be using the Measure option from Hyperview. Load the h3d file to input, and navigate to the measure option. Select the 2 nodes from distance measurement in the area of interest. Now track the change in distance as the simulation proceeds towards the last steps. In the reference images shown below, the distance measured changes from 742 mm to 724mm. A decrease in measurement here indicates the intrusion. From calculations, you can find out the exact value of intrusion.

With this, we came to the end of this article which saw different ways to define the intrusion.