Reconceptualising toddler aggression : a thesis presented in partial fulfilment of the requirements for the degree of Master of Education at Massey University, Palmerston North, New Zealand

This study used sorting techniques and Multidimensional Scaling analyses (MDS) to interrogate the comprehensiveness of a toddler aggression construct - Aggressive Behavior (AGG) - as empirically defined by the Child Behavior Checklist for Two and Three-year-olds (CBCL/2-3). MDS provided a way of unravelling the latent dimensional structures of the checklist item set and creating an inter-item semantic-like map. This map acted as a tool in the summary of patterns in sets of archival CBCL toddler data to reveal latent coherence or dimensional consistency across toddlerhood with specific regard to the aggression or aggressive-like behaviour construct – the main research goal of the present study. First New Zealand participants (N=70, x=30 years) completed four independent semantic-like matching tasks by sorting CBCL/2-3 checklist items according to their "face value". MDS algorithms transformed individual data into a map and hierarchical trees (h-trees) showing inter-item proximities. After validation of the map clusters sets of archival CBCL data were represented and interpreted in the 5-dimensional MDS solution (P=5) as vectors using PROFIT analysis. A measure of the stability of the vector components in terms of the amount of common variance captured across 24 to 42 months - of – age. demonstrated better fit than CBCL subscale stability for the first three dimensions. Candidates for dimensional stability across toddlerhood indicated by the MDS analyses and map were suggested. Replication of the toddler map. the second objective, involved creating an expanded item set that included items from the CBCL/4-18. The new Combined item set was then sorted following identical procedures by a different group (N=49, x=30). PROFIT analyses of archival 4-18 data on the rotated Combined configuration was compared with stability of Achenbach's CBCL/4-18 subscales between 60-months- and 72-months-of-age but correlations were no better than chance. Additional analyses were undertaken that revealed the archival CBCL/4-18 items had little variance when interpreted in the MDS solution. This study succeeded in identifying alternative candidates for continuity of aggressive - like behaviour across toddlerhood in patterns in raw CBCL data that may contribute to the reported CBCL/2-3 Aggressive Behavior construct stability. Three alternative constructs are suggested: a construct which features high frustration, anger and resistance to control - believed to interact with punitive or restrictive parenting practices, and central in theories of the development of coercive parent-child relationships; a construct which appears to index insecure attachment styles; and a construct reflecting toddlers' developing ability to control their attention and behaviour

Estimating the R-curve from residual strength data

A method is presented for estimating the crack-extension resistance curve (R-curve) from residual-strength (maximum load against original crack length) data for precracked fracture specimens. The method allows additional information to be inferred from simple test results, and that information can be used to estimate the failure loads of more complicated structures of the same material and thickness. The fundamentals of the R-curve concept are reviewed first. Then the analytical basis for the estimation method is presented. The estimation method has been verified in two ways. Data from the literature (involving several materials and different types of specimens) are used to show that the estimated R-curve is in good agreement with the measured R-curve. A recent predictive blind round-robin program offers a more crucial test. When the actual failure loads are disclosed, the predictions are found to be in good agreement

Fracture Testing with Surface Crack Specimens

Recommendations are given for the design, preparation, and static fracture testing of surface crack specimens. The recommendations are preceded by background information including discussions of stress intensity factors, crack opening displacements, and fracture toughness values associated with surface crack specimens. Cyclic load and sustained load tests are discussed briefly

A relation between semiempirical fracture analyses and R-curves

The relations between several semiempirical fracture analyses (SEFA) and the R-curve concept of fracture mechanics are examined and the conditions for equivalence between a SEFA and an R-curve are derived. A hypothetical material is employed to study the relation analytically. Equivalent R-curves are developed for several real materials using data from the literature. For each SEFA there is an equivalent R-curve whose magnitude and shape are determined by the SEFA formulation and its empirical parameters. If the R-curve is indeed unique, then the various empirical parameters cannot be constant, and vice versa. However, for one SEFA the differences are small enough that they may be within the range of normal data scatter for real materials

Method for estimating crack-extension resistance curve from residual strength data

A method is presented for estimating the crack extension resistance curve (R curve) from residual strength (maximum load against initial crack length) data for precracked fracture specimens. The method allows additional information to be inferred from simple test results, and that information is used to estimate the failure loads of more complicated structures. Numerical differentiation of the residual strength data is required, and the problems that it may present are discussed

Stress intensity and crack displacement for small edge cracks

The weight function method was used to derive stress intensity factors and crack mouth displacement coefficients for small edge cracks (less than 20 percent of the specimen width) in common fracture specimen configurations. Contact stresses due to point application of loads were found to be small but significant for three-point bending and insignificant for four-point bending. The results are compared with available equations and numerical solutions from the literature and with unpublished boundary collocation results

Crack growth measured on flat and curved surfaces at cryogenic temperatures

Multiple element continuity gage measures plane stress crack growth plus surface crack growth under plane strain conditions. The gage measures flat and curved surfaces and operates at cryogenic temperatures