Recently I had an amazing reunion with my friends and mentors, Dwight Yoder and Steve Jordan, in Sanibel Island, FL. Our wives, Carolyn, Donna, and Anne joined us in this remarkable event. Steve and Dwight have been my friends and mentors my entire professional life.

In 1977 Steve and his business partners, Mike Apostal and Chuck Ritter, founded Jordan, Apostal, Ritter Associates Engineering Mechanics Consultants in Davisville, RI.  JAR began to do engineering mechanics consulting for the AMOCO Research Center in Tulsa, OK. JAR and AMOCO were two of the first companies to utilize the finite element method to model the lower part of the drill string, called the bottom hole assembly, to predict directional drilling for the oil and gas industry. JAR’s work with AMOCO led to Steve, Mike and Chuck creating Drilling Resources Development Corporation in Tulsa, now DRD Technology, to work with AMOCO to develop a drilling simulator to model the entire drilling process in real time. Steve hired Dwight and me in 1981 to join DRD, and our work with AMOCO led to software development for other oil and gas companies. Ultimately DRD developed its own commercial suite of software tools for the oil and gas industry, Wellplan™, which we sold worldwide.

Because of a relationship with John Swanson, founder of Ansys, JAR and Drilling Resources Development Corporation became Ansys Support Distributors in 1984. JAR later became Ansys East in the 1990’s. Steve, Mike and Chuck also founded Concurrent Engineering Corporation in Minneapolis, MN in the 1990’s, which later became Ansys Minneapolis. Earlier in his career Steve worked with several of the pioneers of the early finite element industry including Richard Gallagher of Bell Aerosystems, Cornell University and University of AZ; Richard MacNeal of MSC (NASTRAN); Pedro Marcal and Bob Melosh of MARC Analysis; and David Hibbitt of Hibbitt, Karlsson, and Sorenson, developer of ABAQUS. Steve offered me the opportunity to have a career in the field of engineering simulation, and he mentored me closely my first two decades at DRD.

Dwight has also been my friend and mentor my entire career. In 1995 DRD sold Wellplan to Landmark Graphics, a division of Halliburton. Dwight and I were colleagues at DRD until 1995 when Dwight left DRD to become a Vice President at Landmark Graphics. Dwight later returned to work at DRD before leaving DRD a second time to pursue other interests. Dwight remains a minority owner of DRD. Dwight and Carolyn are god parents to Anne’s and my daughters, Renee and Morgan.

This Sanibel reunion was the first in-person one for Dwight, Steve, and me in 26 years, and the experience was as if we had never been apart.  What a reunion!

Many companies use Ansys to reduce chance of injury and death when an accident occurs such as the overturning of a tractor or the rear impact crash of a car into the back of a trailer. An effective method to minimize danger to vehicle occupants during an accident is to ensure that that the structure absorbs sufficient energy through plastic deformation during the accident impact.

Many vehicles have Roll Over Protection Systems (ROPS) to reduce injury to operators. Figure 1 shows a Bobcat skid steer loader including its ROPS, which is the black cage structure surrounding the driver.

Manufacturers in the earth-moving and agricultural equipment industries design ROPS structures in accordance with the standards ISO 3471 and SAE J2194, respectively. These standards specify physical tests involving sequential pushes in the lateral, vertical, and longitudinal directions while ensuring that the structure absorbs sufficient energy through plastic deformation in each push direction. In addition, there are limitations on the structure deformation to ensure that the structure does not infringe on the volume occupied by the operator, referred to as the Deflection Limited Volume (DLV).

A cost-effective ROPS design approach is to use engineering simulation to design a vehicle to meet energy absorption and deformation requirements. This type of engineering simulation is difficult, however, and many finite element products are not able to accurately calculate the energy absorption during the tests. The challenges are that the finite element code must be able to represent a nonlinear stress strain curve that extends far into the plastic range; quickly and reliably converge as the structure experiences large deformation, plastic strain, and nonlinear contact; and accurately calculate energy absorption. Ansys Mechanical is very well suited for this type of simulation.

The tractor-trailer industry relies on rear impact guards to absorb energy when a car runs into the back of a trailer. Figure 2 shows the rear impact a Chevrolet Malibu crashing into the rear impact guard of a trailer.

DRD recently teamed up with Wilson Trailer of Sioux City, IA to use Ansys Mechanical for design of trailer rear impact guards. Wilson Trailer uses a test method from the Transport Canada Motor Vehicle Safety called Test Method 223. Test Method 223 requires 5-inch displacement loads to be applied at 3 locations of the rear impact guard as shown in Figure 3 and then removed, and the guard must absorb at least 20,000 Joules energy for each load application.

When we simulate a ROPS test or a rear impact guard test in Ansys, we must accurately track the energy absorption as illustrated in Figure 4, which is a component of Test Method 223.

The Ansys Workbench graphical user interface does not have a built-in button to calculate the absorbed strain energy, however, it’s very easy to perform this calculation using a commands object. Figure 5 shows the content of a commands object to calculate absorbed energy and where it belongs in the model tree.

Note that for convenience the commands object calculates the strain energy in two systems of units, lbf-in and Joules, and stores the values into parameters that start with the character string “my_”. When the commands object has been executed Ansys will display all parameters and their values for parameter names starting with “my_” in the commands object details window as shown in Figure 6.