Mechanical Properties of Materials
Hydraulic Press
Problem Scenario
Your company, Medallions, Inc., has been in the business of making small, “coin-size” medallions for the past 10 years. Over time, the business has grown from a small garage-sized operation to a company employing more than 150 people.
The vice president (VP) for manufacturing met with you and the other technicians to brief you on a new medallion that has been ordered and will go into prototype production within the next 60 days. This metal medallion will be three inches in diameter, which is two to three times larger than any medallion that the company now manufactures.
The VP told you and your team that there is a disassembled press in storage that could be adapted to produce the new medallion. He also told you that there is a hand sketch of the assembly for the press in the files. He asked you and your team to locate the disassembled press and make a written report with recommendations for adapting the old press for production of the prototype medallion. He also requested that you make an updated CAD drawing of the assembly.
Upon going to the storage area, you are able to locate, with the aid of the hand sketch, the hydraulic ram and all components of the frame. You are not able to locate the bolts that hold the cross member to the support frame. You notice that the cross member attached to the hydraulic ram is cracked. The rating on the hydraulic ram is 220 T.
Performance Expectations
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◆ Each student will be evaluated on the quality of the team’s written report and recommendations, including CAD drawings.
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◆ Instructors will test and evaluate individual student performance on the discipline-specific content of workshops and participation in class activities.
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◆ Students will have opportunities for self-evaluation, peer evaluation, and team evaluation.
Page 130 Student Handout
©2001 SC ATE Center of Excellence Page 131 Student Handout Engineering Technology Core Engineering Technology Core: An integrated study of physics, mathematics, communications, and engineering technology
Objectives
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◆ Create a stress/strain curve, and identify appropriate points on the curve (yield point, ultimate strength).
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◆ Use stress/strain and shear/bending concepts to design a hydraulic press to form a metal part.
Setting the Stage
In the section on mechanics, you studied the cause and effect of force and motion. The application of a force produced linear or rotational motion. In this study, you did not consider the effect of the application of a force on the size or shape of the object itself. When a force is applied to an object, the force is distributed over the whole of the object and that force may cause the object to deform.
Objects subject to a force are said to be under stress. The amount of stress is the ratio of the applied force to the cross sectional. The ratio of the change in length to the original length is
called strain. For materials, the stress-strain diagram is used to characterize the material. A stress-strain diagram is an experimentally determined graph for a given material. From the stress-strain diagram, it is possible to divide material into two broad categories or characteristics — ductile and brittle materials.
Ductile materials are characterized by their ability to yield and thus change shape and length permanently. Thus, they can be formed into shape. Brittle materials are characterized by the fact that a rupture occurs without a noticeable change in length. Brittle materials cannot be formed into shapes.
©2001 SC ATE Center of Excellence Engineering Technology Core
NOTES
©2001 SC ATE Center of Excellence Engineering Technology Core
NOTES
©2001 SC ATE Center of Excellence Engineering Technology Core
NOTES
©2001 SC ATE Center of Excellence Engineering Technology Core
NOTES
©2001 SC ATE Center of Excellence Engineering Technology Core
NOTES
©2001 SC ATE Center of Excellence Engineering Technology Core
South Carolina Advanced Technological Education Center of Excellence SC Technical College System,
Dr. James L. Hudgins, Executive Director Dr. Dianne Brandstadter, Associate Executive Director
Elaine L. Craft, Center Director and Principal Investigator Dr. James C. Wood, Principal Investigator, Curriculum Lynn G. Mack, Principal Investigator, Faculty Development
Dr. Helen S. Edens, Curriculum Specialist Barbara S. Gainey, Editor
The Engineering Technology Core curriculum was written and refined by SC ATE technical college faculty curriculum writing teams, with review by a National Peer Review Panel and industry focus groups.
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©2001 SC ATE Center of Excellence Engineering Technology Core