2. CHAIN DYNAMICS
A study of phenomena that occur during chain use.
2.1 CHAINS UNDER TENSION A chain can transmit tension, but usually cannot transmit pushing forces. There are actually a few special chains that can push, but this discussion focuses on tension. In the following section we will explain how the chain acts under tension.
2.1.1 Elastic Stretch, Plastic Deformation, and Breakage Tensile Strength
How will the chain behave when it is subjected to tensile loading? There is a standardized test to determine the tensile strength of a chain. Here’s how it works: The manufacturer takes a new, five-link-or-longer power transmis- sion chain and firmly affixes both ends to the jigs (Figure 2.1). Now a load or tension is applied and measurements are taken until the chain breaks (JIS B 1801-1990). Chain Elongation As a chain is subjected to increasing stress or load, it becomes longer. This relationship can be graphed (Figure 2.2). The vertical axis shows increas- ing stress or load, and the horizontal axis shows increasing strain or elonga- tion. In this stress-strain graph, each point represents the following: O-A: elastic region A: limit of proportionality for chains; there is not an obvious declining point, as in mild steel A-C: plastic deformation B: maximum tension point C: actual breakage
O
Elongation
Figure 2.2 Stress-Strain Graph
Figure 2.1 Typical Chain in Tensile Test
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