A VCAD system that can handle product measurement data
Structure analysis using actual product measurement data

Structure analysis using the VCAD system

During the design and manufacturing stages for a new product, there is a need to exactly determine what form the final product should take to fulfill in its purpose. This can mean having to redesign and remake the product, an expensive and time-wasting process. Much better is to have preliminary production and testing procedures that will accurately reflect the mechanical and dimensional requirements of the final product.

Numerical simulation can be applied to determine the exact design to satisfy the requirements of a new product development cycle. Additionally, structure analysis using a CAD system to evaluate product strength with quantitative results for such factors as material strain and stress can be used instead of conventional experiments.

However, the model data used to make a numerical simulation cannot define¡¡the material property of a product but only its shape or surface. The material property is assumed to be uniform and without any defects, though a real product actually has many minute hollows and uneven material distribution. This is why there are always discrepancies between experimental and the numerical analyses.

The VCAD system uses structure analysis for the measurement data of a calculation model. The data measured by X-ray CT scanning include the internal structure and material distribution as well as the model shape. This makes it possible for numerical simulations with the VCAD system to provide the same results as those achieved through experimental analysis.

For an example of structure analysis we have used the motorcycle break caliper part shown in Fig 1. This motorcycle part immobilizes the break pad to press the break disk. It is manufactured by aluminum casting.

Fig.1 The break caliper of a motorcycle
Structure analysis with CAD data
Fig.2 CAD data model

Fig.2  CAD data model

A three-dimensional solid CAD data model of the break caliper case is shown in Fig. 2.

CAD data can define only the surface of the model shape; the internal structure and internal material distribution remain undefined and the assumption is that the material distribution is uniform throughout.

Fig. 3 is a model created with the ¡ÈV-Struct¡É structure analysis software which can be downloaded from this site.

Aluminum is defined for the material property. Areas A and B are fixed in space in the x,y,z directions and the displacement is defined by area C. These points were chosen because the case is fixed with bolts in areas A and B, and the brake pad in area C.

Fig.4 (a) shows the maximum principal stress distribution. Note that the stress becomes larger around the areas where the case is secured with bolts.

Pre- and post-processors are provided with ¡ÉV-Struct¡É so that it can generate a dual grid mesh from three-dimensional solid CAD data and provide boundary conditions with a graphical user interface.

Fig.3 Boundary conditions for structure analysis Maximum principal stress distribution Displacement distribution for the deformed shape
(a) Maximum principal stress distribution (Mpa) (b) Displacement distribution for the deformed shape (mm¡¦magnification¡§30 times)
Fig.3  Boundary conditions for structure analysis Fig.4nbsp;nbsp;Structural analysis result with Cad data

Structure analysis based on measurement result

(1)  Measurement of the actual product

An X-ray CT scanning device is used to measure the break caliper case. Fig.5 shows the tomograms which are taken by dividing the product into 306 cross sections (at about 0.5mm pitch). These tomograms are converted into three-dimensional VCAD data by using the VCAD software ¡ÈV-Cat,¡É which can be downloaded from this site.

¡ÈV-Cat¡É can extract the information from the X-ray CT scan or MRI tomograms and transfer a variety of information on the material into the VCAD framework, which already contains information on the complex internal structure and material distribution. The VCAD framework is an ideal platform to use and save this kind of information.

Fig.5 X-ray CT scan measurement results

Fig.5  X-ray CT scan measurement results

(2)  Detecting casting defects

Fig.6 shows the result of the X-ray CT scan measurements.

Many minute hollows called casting pores can be seen to be distributed over portions of the object. VCAD data can grasp quantitatively the size of each pore and theist relative position. Large pores several mm in width are shown in Fig.6. VCAD data makes it possible to detect the hidden defects of a product while it is still in the casting stage.

Fig.6 Casting pores are evident in this X-ray CT scan

Fig.6  Casting pores are evident in this X-ray CT scan

(3)  Structure analysis using measurement data

The ¡ÈV-Cat¡É results are applied to the three dimensional model to make a structure analysis. This model can be generated from the X-ray CT scan measurement data.

Fig.7 shows the result of the structure analysis using the VCAD software ¡ÈV-Struct.¡É The same boundary conditions are given for this model as were applied to the three-dimensional solid CAD data model. The VCAD system can be operated easily, from the extraction of measurement data to structure analysis. While most other systems can be guided or automatically preceded on the computer in the same way, the extraction process of measurement data and the definition of the boundary conditions are generally excluded.

(a) Maximum principal stress distribution (Mpa) (b) Displacement distribution for the deformed shape (mm¡¦magnification¡§30 times)
(a)  Maximum principal stress distribution (Mpa) (b)  Displacement distribution for the deformed shape (mm¡¦magnification¡§30 times)

Fig.7¡¡Structure analysis result with measurement data

The VCAD system and the future

We have presented an example of structure analysis as it is applied to the break caliper case shown in Fig.7.¡¡The VCAD system includes various kinds of simulation tools such as for heat fluid analysis and manufacturing process simulations for casting and stamping. It also has a utility program to produce the CAM data (NC data) for machining products.

Not all of the VCAD programs are currently available on our download site as most are still undergoing development, but we will introduce newly developed software as soon as it becomes available.

The VCAD system will eventually be able to provide computer-based assistance for all stages of the manufacturing process from design, measurement and simulation to, in the very near future, machining.