Final Report

Simon Tang & Brian Hagan

Introduction

For our project, we chose to use a wheel. For me (Simon Tang), I could have chosen to do a part on the Honda CBX engine (I am modeling the engine in my CAD class). However, I really wanted to do something out of the ordinary. I consulted my partner and we both agreed to do this. To find the actual wheel to model, many junk yards and auto stores were gone to. Finally a rim was donated to us by Zippos on Route 18.

After actually getting the rim, we began to work on the project. Brian Hagan was in charge of the Ansys analysis and I was in charge of modeling. I downloaded the trial version of Wildfire 3.0 Pro/Engineer and modeled the entire rim. We than wanted to do Ansys analysis. I put the .prt file into the school version at Rutgers and found out that the file would not open. The School Version only works with standard version files or school files.

The Rim than needed to be done all over again on the school version. This took a lot of time to do. However, once finished Ansys would be able to work.

For the rest of the report both Brian Hagan and I will be inputting the information that we have obtained and learned. We both enjoyed this project very much. We also enjoyed the input from Professor Zhang for our project. We also found out that he will be leaving Rutgers this semester and both wished to work with him on our Senior design project. We hope for the best for him and thank him for the opportunity to really get to work on a real world applicable project.

Thank You!

GeometryThe rim donated to us was the Zenetti Five Rim. The size was 18” x 8”. This first value is the rim diameter and the second

value is the rim width. Please look to fig.1 to see it in application. In fig.2 you can see what each number and letter means. For this specific rim that we modeled, the rim code is specifically: 18 x 8J(20)5-114.3. Each car has a different hub to mount the rim. These codes are specific for each different type of car.

The largest manufactured Zenetti Five rim goes up to 22”. This rim is chrome plated for a nice luxury look. The rim is usually placed on expensive SUV’s like the Cadillac Escalade or luxury sedans like the BMW 6 series or Mercedes Benz CL series. We had to use 18” since that was the size of the donated rim. We would have liked to modeled a 20”, since that works better with the car we chose to mount it on. However, there is only a 2” difference.

It seems that Zenetti have stopped making the 18” rims for the Five. They are on sale on certain websites. However, on the Zenetti website, they are not there. We would also have liked to modeled rims for racing applications, but those are very expensive. This rim is specifically for on road street use, so every application that we used on this wheel, for example load identification and rotational force, was taken to be for street use. It would be nice to apply racing applications to a racing rim to see an analysis.

fig.2

fig.1

Figure 1 and Figure 2 are a reference for wheel size and bolt patterns for car applications.

MaterialThe material that the Zenetti Five rim is made out of is A356-T6. This is a Aluminum Silicon Alloy. On matweb.com they have

all of the mechanical properties of this material. The composition contains Aluminum, Silicon, Copper, Magnesium, Manganese, Iron, and Zinc.

A356-T6 is used for many automotive applications. On some GM trucks the engine heads are made out of this material. The same goes for engine blocks. Please look at fig.1 and fig.2 for images of those parts.

A356-T6 is the ideal metal for casting and for machining. Comparing this aluminum alloy to others, for example – 242-T77 or 319-T5, which are also used for automobile applications, the A356-T6 stands on top. It has the strongest properties, easiest to cast, good for machining, and meets all the requirements for everything needed for automobile applications. If you look at fig.3, there is a comparison of all three metals and as you can see A356-t6, is the best choice. And if you look at fig.4 you can also see a chart of it comparing to the requirments.

For another used aluminum alloy, applied on to airplanes, A356-T6 is still chosen. Comparing this aluminum to the use of A380, A356-T6 is used for sand casting and permanent mold casting.

fig.1

fig.4

Alloy Requirement 242 - T77 319-T5 A356-T6

Performance      

Ultimate Tensile Strength 

35 ksi / 245 MPa

30 ksi /205 MPa

30 ksi /205 MPa

40 ksi/ 280 MPa

Tensile Yield Strength  31 ksi / 215 MPa

23 ksi / 157 MPa

26ksi / 178 MPa

31 ksi / 215 MPa

Ductility (% Elongation) 1.6% 2% 1.5% 6%

Brinell Hardness (BHN) 80 75 80 80

Fatigue Strength  10^8 cycles

8.5 ksi / 60 MPa

10.5 ksi /74 MPa

11 ksi / 77 MPa

8.5 ksi / 60 MPa

 Pressure Tightness(1= Excellent,

5= Poor)1 3 2 1

Manufacturability        

Castability/Fluidity  (1= Excellent,

5= Poor)1 3 2 1

Machinability(1= Excellent,

5= Poor)3 2 3 3

fig.3 – Aluminum Alloy Comparison

For A380, it is only for high pressure casting. Because it is only used for high pressure casting, do to it’s environment, A380 forms pours, which allows water and other things to enter the aluminum. This affects heat treating after the aluminum casting. However, for A356-T6, since it is only sand cast or permanent mold cast, it is heat treated after casting and because it can be heat treated, it gets better and similar properties of the A380. This makes it a perfect replacement for A380.

fig.2

Curb Weight MT: 3339Curb Weight AT: N/AGround Clearance: Not ListedHeight: 52.1Length: 169.8Top Type (Standard): Hard FixedTop Type (Optional): Not ApplicableTrack (Front): 60.4Track (Rear): 60.8Weight Distribution AT (Front): N/AWeight Distribution AT (Rear): N/AWeight Distribution MT (Front): 53Weight Distribution MT (Rear): 47Wheelbase: 104.3Width: 71.5Doors (Standard): 2Doors (Maximum): 2

Courtesy of Yahoo! Autos

http://autos.yahoo.com/nissan_350z_coupe_base-specs/?p=ext

In order to properly identify the load distribution, a car must be selected. For demonstrative purposes, a 2007 Nissan 350Z was selected. Its specifications are as follows:

Load

Assuming a 53/47 weight distribution, it is safe to say that the largest amount of weight supported by a single tire will be half of 53% of the total weight (because 2 tires will be supporting the heavier half of the car). The resultant of this calculation is 884.8 lbf. This force then will be acting on the bearings of the rim which distribute the weight of the car to the rim. In addition, an equal force must be applied in the opposite direction to support the load. This force will be simplified to a single upward normal force acting on the bottom of the rim. In actuality, the weight of the car is supported by the tension of the pneumonic tire fitted along the edges of the rim. While the tension remains constant throughout the tire, the direction varies from top to bottom. In the bottom half of the tire, the rubber bulges slightly where it comes in contact with the ground. This causes the forces to be dispensed outward perpendicular to the tire’s surface. The two sides of the tire bulge out equally, so the outward components cancel out. The resultant is an upward tension which is higher then the downward tension, a difference equal to the weight of the car.

Method & Improvements

Another force included in the analysis is a pressure force. Because the rim would be fitted with a standard pneumonic tire housing a certain pressure, a pressure element must be included. Again, the magnitude of this pressure is dependent on the tire; however an estimated pressure of 40 psi will be used for demonstrative purposes. This pressure is distributed throughout the surface of the outside ring portion of the rim.

In addition to the force elements, a rotational velocity was also added. Again, this value is dependent of outside factors such as speed and tire thickness. Because of this, more assumptions were made, this time to the tires specifications. Assuming that the tire will add an additional 2 inches to the diameter and the car’s velocity is 60 mph, an estimate of 916 RPM was found and added to the simulation.

Along with these forces and rotational velocity, support elements were added to simulate the rims connection with the car. Two different supports were added, one to represent the hub the rim rests on and another to represent the bolts holding the rim in place. Cylindrical supports were used in both cases, with little difference between the two. The bolt support was fixed in all directions, including axial, radial, and tangential. The hub support however was limited only to tangential movement, allowing the rim to rotate. In a more realistic scenario the hub is the element spinning, but in order to study the behavior of the rim this factor is ignored.

Another force included in the analysis is a pressure force. Because the rim would be fitted with a standard pneumonic tire housing a certain pressure, a pressure element must be included. Again, the magnitude of this pressure is dependent on the tire; however an estimated pressure of 40 psi will be used for demonstrative purposes. This pressure is distributed throughout the surface of the outside ring portion of the rim.

After the simulated loads were applied to the geometry, several stress analysis figures were generated. The initial rim design had a maximum stress of 3.347E03 and a minimum stress of 4.67E-01. This maximum stress occurred at the center of a spoke closest to the normal force. Because there is a rotational element, the analysis only applies to a certain point in time, and the stresses are redistributed over time. Still, this doesn’t change the fact that the maximum stress will always occur in the lowest spoke, so the analysis is not affected. The minimum stress occurs on the outside edge of the bearings where the rim is bolted down. Because the forces, supports, and rotation are idealized and don’t include any variation in magnitude or direction (that may occur, for example, due to imperfections in the surface fitted car is driving on) the stresses may vary slightly from there true values.

Along with stress, the deformation was also examined. The maximum deformation occurred at the outer edge of the rim closest to the normal force exerted by the ground along the thin outer portion of the rim, where it deformed by 0.676E-03 inches. This is most likely because the outer edge is the thinnest portion of the rim, which makes it the most sensitive to deformation. There were areas where the deformation was negligible located around the inner portion of the rim.

After the geometry was improved, the stresses decreased greatly. By increasing the thickness of the spokes to a little less then twice their thickness, (from 0.69 in to 1.25 in), the max stresses which were located in the spokes decreased greatly. The new max stress of 1.594E03 PSI demonstrates more then a 50% decrease in total stress. The location of this maximum stress also changed, moving from the spoke to the outer portion of the rim. Deformation also decreased as well. While the location of the deformation did not change too greatly, the total amount was also reduced by half. The new maximum deformation was 3.123E-03 inches, still occurring along the outer edge closest to the ground’s normal force. After the improvements, a safety factor of 15 was achieved, demonstrating it can be used for civilian use.

Things We Should Have DoneAfter our presentation, it was brought to our attention that torque was needed: a moment applied to the central

cylindrical support should be included. A moment of 19.7 lb-in was calculated to be applied to the rim from the center. This was added in a later analysis (please look to fig.1 to see image of added torque) and similar results to the stress and deformation were obtained. However, the sheer stress results, which was not heavily focused on in our original project, was different. Please look to fig.2 and fig.3 to see the shear analysis. We also decreased shear by a factor of 2. The shear in the normal wheel was 1025 psi, while the improved wheel shear became 566.4 psi. This is a great improvement. This would make the rim even more safer than it already was. Again this would be a lot better for heavier cars.

We could have also taken into account the weight of both team members. A car cannot drive itself. We did not think about this until after the presentation. Brian Hagan’s weight is 180 lbs and Simon Tang’s weight is 170 lbs. This would increase the total weight from 3339 lbs of the 350z to 3689 lbs. Even though the weight increased, this wouldn’t really affect our project. Our values would have increased by a small increment.

Fig. 1 Fig. 2 Fig. 3

ConclusionWe made the spokes thicker and the inner wall thicker because the maximum stresses were on

those components. For the car to reduce it’s stress and deformation levels it would not be necessary on a 350Z, since the car is not heavy enough to cause anything to fail. Although for cars like the Cadillac escalade, those improvements will be very handy and if a car was heavy enough, than necessary.

One thing that increased was the minimum stress. This could be due to the increase in weight. Since we added more material, the stress caused by the rotational element increased. This could be due to the increase in moment of inertia due to the increase in weight. However, the increase in minimum stress is still significantly low.

For fatigue, if the rim were to ever fail, major accidents could happen and people’s lives could be lost. In this case the max stress reached up to 3437 psi, this is still significantly lower than the fatigue strength, which is 8700 psi. If we put a heavier car and/or faster rotational speed on to the wheel, the max stress would than increase, which could possibly cause fatigue. In this case, the improvements of thickening the inner walls and the spokes would be very necessary.

We added a torque into the final report. Seeing the values of the shear stress after the presentation allowed us to get a better understanding of the entire project. With our improvements we even got to decrease the shear by a marginal amount.

In the end, with our improvements we got to decrease shear, stress, and deformation. This would be necessary for a heavy vehicle. However, for the 350z, get different rims. Finally, we would like to thank Dr. Zhang again for this opportunity to work on a real world applicable project. We wish you the best and thank you again.

Referenceshttp://www.finishing.com/309/92.shtml

http://www.sfsa.org/tutorials/eng_block/GMBlock_11c.htm

http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MAC3560T6S

http://www.mse.mtu.edu/classes/my4130/databank/aluminum/a356.html

http://www.zenetti.com/html/2007/index.php?section=wheels&wheelID=1&carID

http://coewww.rutgers.edu/classes/mae/mae342/online_res/ANSYS%20Quick%20Start%20Tutorial.htm

http://autos.yahoo.com/nissan_350z_coupe_base-specs/?p=ext

http://www.elec-toolbox.com/Formulas/Motor/mtrform.htm

http://enkei.com/Wh.Definitions.html