Strain index

The Strain Index is determined from data obtained using the pendulum impact device. 

Material Bonding Index x 102 Brittle Fracture Index Strain Index x 102... 

The bond strain in this chapter, as in most other places in this book, is defined as the difference between the observed bond lengths and the bond lengths calculated from the theoretical bond valences. A bond strain index that measures this strain is defined in eqn (12.1). 

Lattice-induced strains clearly cause the bonds to violate the network equations and their presence may be indicated by a large value of the bond strain index (BSI) defined in eqn (12.1) (Preiser et al. 1999, <73 in table 1) ... 

Generally, only powders that form hard compacts under an applied pressure without exhibiting any tendency to cap or chip can be considered as readily compactible. The compactibility of pharmaceutical powders can be characterized by its tensile strength and indentation hardness, which can be used to determine three dimensionless parameters strain index, bonding index, and brittle fracture index. 

Pharmaceutical compacts are complex structures that present difficult challenges when measuring their mechanical properties. Hiestand was a pioneer who quantified the compaction properties of pharmaceutical powders and (105-109) the result of his work are indices known as the Hiestand Tableting Indices. These indices are dimensionless numbers used to describe the mechanical properties and consolidation behavior of materials under compression and decompression. The three main Hiestand Tableting Indices are the bonding index, brittle fracture index BFl), and strain index. 

Hiestand Tableting Indices Likelihood of failure during decompression depends on the ability of the material to relieve elastic stress by plastic deformation without undergoing brittle fracture, and this is time-dependent. Those which relieve stress rapidly are less likely to cap or delaminate. Hiestand and Smith [Powder Technol., 38, 145 (1984)] developed three pharmaceutical tableting indices, which are applicable for gener characterization of powder com-pactiability. The strain index (SI) is a measure of the elastic recovery following plastic deformation, the bonding index (BI) is a measure of plastic deFormation at contacts and bond survival, and the brittle fracture index (BFI) is a measure of compact brittleness. 

Fliestand and Smith (1984) proposed three indices referred to as Tabletting Indices. The three indices are a strain index, bonding index and the BFI, which was described in the section on Capping. The strain index is a measure of the strain present in a material following compaction and is a measure of elastic recovery calculated by a dynamic indentation hardness test. The bonding index is a measure of the material s ability to deform plastically and form bonds and is the ratio of a compact s tensile strength and indentation hardness. 

An ordinal rating is assigned for each of the variables according to the exposure data. The proposed strain index is the product of these six multipliers assigned to each of the variables. 

There are some disorders of the distal upper extremity that should not be predicted by the strain index, such as hand-arm vibration syndrome (HAVS) and hypothenar hammer syndrome. 

The strain index has not been developed to predict increased risk for distal upper-extremity disorders to uncertain etiology or relationship to work. Examples include ganglion cysts, osteoarthritis, avascular necrosis of carpal bones, and ulnar nerve entrapment at the elbow. 

The proposed concept of the strain index is a semiquantitative job analysis methodology that results in a numerical score that is believed to correlate with the risk of developing distal upper-extremity disorders. The SI score represents the product of six multipliers that correspond to six task... 

These ratings, applied to model variables, are presented in Table 23. The multipliers for each task variable related to these ratings are shown in Table 24. The strain index score as the product of till six multiphers is defined as follows ... 

Application of the strain index involves five steps ... 

Moore, J. S., and Gaig, A. (1995), The Strain Index A Proposed Method to Analyze Jobs for Risk of Distal Upper Extremity Disorders, American Industrial Hygiene Association Journal, Vol. 56, pp. 443-458. 

Ayoub et al. [1987] developed a quantitative stress-strain index, called the job severity index (lSl),from empirical task analysis and epidemiologic data for manual materials handling tasks. This index computes the ratio of job task physical demands to person physical capacities from several interacting variables. The appHcation of the JSl is also detailed in Ayoub and Mital [1991]. Also, Kondraske [1995] defines a quantitative measure of stress that can be applied to individual performance resources. In this measure, defined as the ratio of resource utilization to resource availability, an adverse effect maybe noted when the stress level exceeds a threshold, which may be different for different types of performance resources (e.g., strength, range of motion, etc.). 

Ayoub et al. (1987) developed a quantitative stress-strain index, called the job severity index (JSI), from empirical task analysis and epidemiologic data for manual materials handling tasks. This index computes the ratio of job task physical demands to person physical capacities from several interacting... 

---