Service Life Under Dynamic Load

Torque, impact, dynamic flexural moments tolerable load cycles 

Left Strength of tooth root strength, temperature of the gear, various lubncation conditions Right Tooth stress (tooth flank strength), local tooth flank temperature, oil lubrication 

Pc = stress at the pitch point n = specified load/stress cycles 

In addition to this strength calculation approach, results from friction, wear and lubrication investigations, all being long-term investigations, are available as so-called wear intensity for long-term calculations in the dynamic range [117], 

There are several damage phenomena observed in fiber composites  

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Ex vivo pushout tests indicate that the ceramic-metal bond fails before the ceramic-tissue bond and is the weak link in the system (Kohn and Ducheyne, 1992). There is therefore reason for concern about the weak ceramic-metal bond and integrity of that interface over a lengthy service life of functional loading. Material function under dynamic loading represents a critical parameter and a much-needed research area (Koeneman et al., 1990 Lemons, 1988). 

A statement can be made with regard to the expected service life under a certain dynamic load which is below 3% of the lap shear value (0.08 MPa divided by 2.5 MPa = 0.032 = 3.2%), see Section 6.2.2. Limits of Elastic Bonding . 

For a large number of plastics components, such as machine elements, pipes and vehicle parts, the problem of durability under dynamic load turns out to be the limit of service life lines under the influence of media, increased temperature, lubricants, climates and processing. Figure 1.62. 

Adhesive joints are frequently expected to perform satisfactorily under service conditions which include dynamically and statically applied loads and exposure to hostile environments such as water, organic solvents, etc and, in many instances, combinations of these conditions may be experienced. It is therefore of prime importance for the adhesives technologist to be able to develop and recommend adhesive systems which will possess an adequate service life under the operating conditions which are to be experienced by the bonded structure. This, in turn, leads to the need to understand the mechanisms of failure and to develop test methods for (i) developing and selecting adhesive systems and (ii) predicting quantitatively the expected service life. 

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