The goal of this tutorial is to illustrate modeling of dynamic loading originating from lowering a mass via a pulley assembly.

Purpose

The primary goal of this tutorial is to illustrate how to model dynamic loading originating from a pulley assembly depicted in Figure 1.

Figure 1: Geometry of the pulley assembly

Initially, the entire the pulley assembly is at rest and the mass at joint 4 is being supported by a cable going through two pulleys and attached to the winch located at joint 1.

Winching (lowering) of the mass using a constant speed (1ft/sec) of the winch and the associated dynamic effects will be modeled. The dynamic effects will be introduce primarily at the beginning and the end of the winching operation when the speed of the winch changes from 0ft/sec to 1ft/sec and vice versa.

Model Description

The modeling is based on the following assumptions:

• The qualitative response is the primary focus and therefore no specific dimensions and properties were shown in Figure 1. If needed, these properties can be obtained directly from the attached model file.
• The cable is not being modeled as moving over the pulleys. Instead, it is directly connected to the pulleys (joints 2 and 3) represented as springs. These springs resist load normal to the cable at the middle point of contact, but not tangentially. There is no consideration of the radius of the pulley.
• Winching (lowering of the mass) is modeled by applying strain load to the vertical cable. This moves the mass downward. Dynamical behavior of the mass is captured. Dynamics of the cable itself is not,presumably it is insignificant.
• Time history load case is used to increase this strain linearly in time, which would correspond to a constant speed of winching.

Discussion of Results

Attachments

• model
• report