A customer (Pacific Steel Casting Company in Berkeley, California) in the steel industry has submitted a request for the design of a hook for lifting hot-metal ladles. These hooks are upgrades of equipment from the old (1934) Pacific Steel Casting facility (hence the dimensions in U.S. Customary units) originally located at that site. I have formulated the following problem statement. Please refer to the figures for details.
Problem statement: Design a hook for lifting hot-metal ladles with a maximum weight of 150 tons (1 ton=2000 lbf). The hook should be compatible with the ladle details given in Figure 1. The hook eye should receive an 8-inch diameter pin for attaching to the crane. The thickness of the hook should not exceed 6 inches.
In the analysis, the hook should have the general configuration as shown in Figure 2. As per customer instructions, the structural steel for the hook should be one of the steels shown in Table 1. Be sure to analyze the stresses at Sections A-A, B-B, and C-C of the hook. In addition, assume uniaxial, noneccentric loading producing loads only in the plane of the hook. Since the steels in Table 1 appear to be fairly ductile use the maximum shear stress yield criterion. Also, because weight is not really an important consideration, but safety is, use a factor of safety, FS, of 4.
Don't forget to use a curved beam analysis at section A-A and to apply stress concentration factors at the hole near section C-C. Also, be sure to consider that the length dimension of the hook must be sufficient to allow the ladle to be tipped to its maximum extent. Based on your knowledge of manufacturing processes, suggest (in general, details are not necessary) a possible fabrication process for the hook.
a) Schematic of teeming ladle and hooks b) Details of ladle used for design
Figure 1 Overall views of the teeming ladle with hooks. a) Schematic and b) Details
Table 1: Characteristics of candidate structural steels
| ASTM Spec. |
Description |
Carbon C |
Manganese Mn |
Other |
Yield Strength (psi) |
Ultimate Tensile Strength (psi) |
Relative Cost |
| A36 |
Carbon Steel |
0.29 |
1 |
--- |
36,000 |
60,000 |
1 |
| A441 |
HSLA Steel |
0.22 |
1.25 |
0.02 V |
50,000 |
70,000 |
1.15 |
| A242 |
HSLA Steel |
0.15 |
1.1 |
0.05 V, 0.3 Cu |
50,000 |
70,000 |
1.25 |
| A514 |
Alloy Steel |
0.15 |
0.8 |
Ni-Cr-Mo |
100,000 |
120,000 |
2 |
Figure 1 Overall views of the teeming ladle with hooks. a) Schematic and b) Details
a) Details of hook used for design b) Details of ladle used for design
Figure 2 Details of ladle hook and ladle. a) Hook and b) Ladle
1) Define engineering design. Illustrate the engineering design process/activity and elaborate on each important step/concept.
2) From the expression, "Build a better mousetrap and the world will beat a path to your door," write a goal/problem statement and a set of at least six specifications that you would apply to a solution. Suggest at least three concepts, complete with sketches, to satisfy this statement.
3) Define what is ethics in the field of engineering and explain what is meant by ethical dilemma.
4) Convert a mass of 250 lbm to a) lbf , b) slug, c) kg.
5) Express a 68 kg mass in units of slugs and lbm. How much does this mass weigh in lbf and N on a) earth, b) moon and c) in earth orbit?
6) Convert a gear reducer torque of 20,000 in-lb to a) N-m and b) N-mm
7) What do the following initialisms stand for: a) ips; b) fps; c) cgs; d) SI? What are the three base units in each system? What is a derived unit in each system.
8) Name three of the several groups of machine elements and identify one engineering application for each group you name.
9) Provide two examples of each: a) design for failure and b) design not to fail. Explain what is important to the engineer and user for each example.
10) What is the trajectory of an un-struck golf ball?