Simcenter Testing Solutions Simcenter Testlab Virtual Prototype Assembly

Direct YouTube link: https://youtu.be/TYodfARcHZQ


The Simcenter Testlab Virtual Prototype Assembly (VPA) software is used to predict the noise or vibration performance of an assembled dynamic system.  The user creates components based on structural Frequency Response Functions (FRFs) and load functions (spectrums, orders, waterfalls, etc). Using a graphical interface, multiple components can be connected directly or with stiffness modules as shown in Figure 1.
 
The loads and FRFs can be derived by simulation or test data.  The total system performance can be calculated and understood.

This article describes how to use the VPA software: 
1. Background
2. Components
   2.1 Structural Components
   2.2 Loads 
   2.3 Test Scenarios
3. Getting Started
4. Example
5. VPA Definition
6. VPA Assembly

1. Background

The reduced availability of physical prototypes, together with the increase in complexity brought by the electrification put the validation of the noise and vibration (NVH) attributes at risk. Addressing NVH issues late in the product development cycle is expensive and creates delays in product launches.

SImcenter Testlab Virtual Prototype Assembly (VPA) is a solution designed to overcome the challenges faced by NVH engineers.  This is done by creating virtual prototypes to assess in early project phases the noise and vibration target performance and set more realistic sub-system design targets.  This solution is not only designed for test engineers, but also for simulation engineers, since it is possible to use and combine both data types. 

This solution is based on the Dynamic Substructuring (DS) concept and benefits from the FRF Based Substructuring (FBS) theory. The Dynamic Substructuring technique is often applied to complex structures to determine their structural dynamics. The complex structure is divided in substructures or sub-systems that are characterized separately and after assembled to predict or evaluate the assembled dynamics. This approach permits not only the evaluation of the components separately, calculating their impact on the whole assembly, but also the opportunity to create virtual prototypes assessing the target performance at critical conditions. Furthermore, several components’ combinations can be evaluated on different test conditions.
 
Six types of components are used in Simcenter Testlab Virtual Prototype Assembly:

2.1 Structural Components (defined by FRFs):

• Body Receiver: Defined as the system receiver where the target points are present. For a strongly coupled system, a Blocked Forces model is used and, in this case, the FRF’s between the Input Degree of Freedom (DOF) Ids and to the Response (Target) points are needed. For this case, the effect on the loads of the interaction of source and receiver is taken into account. For weakly coupled system, just the FRFs between Input and Response are needed. The total assembled transfer functions are required for the noise prediction. These are calculated from the combined information from the individual components. An example of a Body Receiver component is a vehicle body, ship structure, tractor body, etc.
• Connectors: Used to model bushing or system mounts. These components are usually characterized by the dynamic stiffness curves between Inputs and Outputs DOF Ids. They can incorporate one or multiple Degrees of Freedom (DOF) – translational and rotational. Even multiple mounts can be stored in a single connector component.
• Passive Components: Structural parts between the sources and receivers of a mechanical structure. To publish such component in the VPA Definition application the FRF’s between Input DOFs and Output DOFs is needed. Also, the driving points for Input and Output DOFs are needed. The number of input and outputs can be different. 
• Active Components: These components will store the FRF’s of the source. If the Loads are characterized at the interface/connection, the Blocked Forces model will be used, hence the FRF’s between connections points should be available. If, the Loads are defined as Pseudo Forces, at the source center for example, the FRF’s between Input and Output DOFs are needed and the FRF’s between the Output points (connection points).

2.2 Loads

Load components are designed to store force excitations (orders, spectrum, autopower, waterfalls) that are applied to the system.  These forces can be blocked forces, pseudo forces, or free velocities.  These forces will pair with the Active Components, creating the system excitation.

More information on the how to use block forces properly in the knowledge article: Blocked Forces versus Contact Forces in Transfer Path Analysis (TPA).

2.3 Test Scenarios

The Test Scenarios can also be interpreted as the operating conditions of the product. This component will provide the dependencies values for a certain test conditions, such as motor rpm, speed, torque, position, etc.

3.  Getting Started

The Simcenter Testlab Virtual Prototype Assembly software uses two add-ins: VPA Definition and VPA Assembler as shown in Figure 2.
 

• [H] represents the FRF matrixes
• [K] the Dynamic Stiffness of the mounts and bushings
• {F} the Forces from the EDU