Experimental and Finite Element Analysis of Tong Load Slip Versus Clamping Force

Abstract

Tong type mechanisms have been used in industry to lift many types of loads where the clamping force generated in the tong mechanism along with friction and indentation prevent the load from slipping out of the tongs. There are several types of tong designs, lifted load geometries and levels of hardness resulting in numerous variations of clamping forces and grip/load geometries which makes the design of the tong mechanisms extremely challenging. The purpose of this work is to develop a Finite Element Analysis (FEA) simulation of the grip behavior under the multitude of variables that occur in the practical use of tongs to lift loads. Variables include tong mechanism geometry and load size resulting in different tong grip angles relative to the lifted load and resulting clamping force. Other variables include the hardness of the lifted load and the style of grips. With an FEA simulation methodology developed, a multitude of different variables affecting tong effectiveness can be evaluated. To verify the FEA simulation, a series of actual laboratory tests were conducted. These tests measured the load slip force as a function of clamping force, grip geometry, and load and grip hardness. Also measured was the grip indentation into the load and deflection versus slip force. A comparison of the results of the FEA simulation and the experimental tests is given. In some cases the correlation is good and in others more work is needed. A plan for further improvement of the FEA simulation technique is given.