The construct of mental toughness is in a state of evolution and refinement. The current study proposed to investigate; (1) the importance of mental toughness attributes from a Classical Martial Arts context, (2) the trainability of the mental toughness attributes from a Classical Martial Arts context, (3) and the extent to which classical martial artists perceive that attributes converge under broader, overarching sub-categories. The current study used a two-phase approach to evaluate the perceptions of mental toughness in 174 non-competition based classical martial artists. Phase One used a survey (a) to assess the perceived importance and trainability of mental toughness, (b) to evaluate unique CMA (CMA) mental toughness components, and (c) to determine underlying factors via factor analysis. Phase Two used interviews to enhance study perspectives of 20 randomly selected CMA participants. Phase One survey results support (a) the inclusion of all items as important to the mental toughness construct, (b) the trainability of all but 4 items, and (c) anticipation, learning attitude, and ethics as three unique CMA mental toughness components. The factor analysis supports the use of a six-factor model, which accounts for 60% of the variance, to explain CMA toughness. Phase Two promotes the use of several key themes as important to mental toughness in the CMA¬- conviction, commitment, conditioning, readiness to perform, distraction control, and shifting focus of attention. Phase Two also provides insight into the context specific application of the six-factor model. Previous perspectives on attribute importance, trainability, and general dimensions of mental toughness are supported by the current study. Variations exist between dimensions in the current study and those found previously. However, these differences are noted to exist more in context applications than in the essential meanings. / Ph. D.

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Cordierite was adhered to molybdenum using various metallic interlayers of copper, nickel, and chromium. The development of a coating adhesion test methodology was required to choose between interface designs. An indentation method was chosen because of ease in testing and availability of fracture mechanics interpretations of test data. The interfacial fracture toughness was determined from indentation load vs. crack length data by examining the residual stress and critical buckling load of the ceramic coatings. The interfacial fracture toughness values obtained using a slightly different indentation analysis agree with those in the literature. Quantitative chemical analysis of the interface microstructure was used to explain differences in interfacial fracture toughness values for samples with different metallic interlayer designs. The best interface design for adhering cordierite glass-ceramic coatings to molybdenum was found to be molybdenum / 2 μm copper / 4 μm chromium / cordierite. / Master of Science

This study investigated the validity of scores of a workplace-based measure of mental toughness, the Mental Toughness Situational Judgment Test (MTSJT). The goal of the study was to determine if MTSJT scores predicted supervisor ratings 1) differentially compared to other measures of mental toughness, grit, and resilience, and 2) incrementally beyond cognitive ability and conscientiousness. Further, two machine learning algorithms – elastic nets and random forests – were used to model predictions at both the item and scale level. MTJST scores provided the most accurate predictions overall when model at the item level via a random forest approach. The MTSJT was the only measure to consistently provide incremental validity when predicting supervisor ratings. The results further emphasize the growing importance of both mental toughness and machine learning algorithms to industrial/organizational psychologists. / Doctor of Philosophy / The study investigated whether the Mental Toughness Situational Judgment Test (MTSJT)– a measure of mental toughness directly in the workplace, could predict employees' supervisor ratings. Further, the study aimed to understand if the MTSJT was a better predictor than other measures of mental toughness, grit, resilience, intelligence, and conscientiousness. The study used machine learning algorithms to generate predictive models using both question-level scores and scale-level scores. The results suggested that the MTSJT scores predicted supervisor ratings at both the question and scale level using a random forest model. Further, the MTJST was a better predictor than most other measures included in the study. The results emphasize the growing importance of both mental toughness and machine learning algorithms to industrial/organizational psychologists.

Mental toughness (MT) has been shown to predict outcomes across a variety of high-stress contexts such as athletics, the military, and the workplace. Despite this, researchers have struggled to reach consensus regarding how best to conceptualize and measure MT. Specifically, MT assessments have focused on measuring general MT rather than domain-specific MT. The current study proposes a measurement model of MT grounded in social-cognitive theory and introduced an assessment of MT within a situational judgment test framework to assess MT in the workplace. Participants completed a battery consisting of the new measure as well as measures intended to establish construct validity. Factor analyses suggested a three-factor solution fit the data best. Furthermore, cross-structure analyses indicated that the new assessment avoided common-method bias in responding, as evident by weak correlations with measures of other constructs. / Master of Science / Mental toughness (MT) has been shown to be a resource that buffers against the negative effects of distress and predicts outcomes across a variety of settings, including the workplace. However, widely used self-report MT questionnaires have numerous issues, such as a lack of context. The current study addressed a number of these issues by creating a measure of MT wherein respondents were given a workplace situation and asked the likelihood that they would respond in a variety of manners, thereby assessing MT as relevant to the workplace context. Three factors of MT were most prominent – task persistence, emotional control, and utilization of feedback. The measure introduced in the current study had small associations with existing self-report measures of MT, personality, and distress, suggesting that the new method of measuring MT avoided some issues inherent to self-report responding. This research laid promising groundwork for the future assessment of MT in the workplace.

The aim of the thesis was to study the susceptibility for brittle failures and the fracture process of duplex stainless steels at sub-zero temperatures (°C). In the first part of the thesis plates of hot-rolled duplex stainless steel with various thicknesses were used to study the influence of delamination (also known as splits) on the fracture toughness. The methods used were impact and fracture toughness testing. Light optical microscopy and scanning electron microscopy were used to investigate the microstructure and fracture surfaces. It was concluded that the delaminations caused a loss of constraint along the crack front which resulted in a stable fracture process despite the presence of cleavage cracks. These delaminations occurred when cleavage cracks are constrained by the elongated austenite lamellae. The pop-in phenomenon which is frequently observed in duplex stainless steels during fracture toughness testing was shown to occur due to these delaminations. The susceptibility for pop-in behaviour during testing increased with decreasing plate thickness. The toughness anisotropy was also explained by the delamination phenomenon.In the second part of the thesis duplex stainless steel weld metals from lean duplex and super duplex were investigated. For the lean duplex weldments with different nickel contents, tensile, impact and fracture toughness testing were conducted from room temperature to sub-zero temperatures. The result showed that increased nickel content decreased the susceptibility for critical cleavage initiation at sub-zero temperatures. The super duplex stainless steel weldment was post weld heat treated. The fracture sequence at low temperature was critical cleavage fracture initiation after minor crack-tip blunting and ductile fracture. Energy-dispersive X-ray spectroscopy investigation of the weld metals showed that substitutional element partitioning is small in the weld metal. However, for the post weld heat treated weldments element partitioning occurred which resulted in decreased nickel content in the ferrite. / <p>QC 20131108</p>

In order to investigate the viability of friction stir welding for use in Naval construction, mode one elastic-plastic fracture toughness of friction stir processed HSLA-65 was determined using current ASTM 1820 and BS 7448 standards. Double-sided welds were used to achieve 12.7 mm thick samples. A constant feed rate of 100 mm/min was used for all welds. To explore the effect of weld parameters on toughness, welds were produced using two rotational speeds: 340 RPM and 490 RPM. The weld centerline, advancing side hardened region (ASHR), and TMAZ/HAZ regions were sampled, in addition to un-welded parent material. All elastic-plastic fracture toughness values were thickness dependent. For welds produced at 340 RPM, toughness ranged from 33% to 75% below parent material. By increasing the rotational speed to 490 RPM, weld toughness was likewise less than the parent material, but increased 12% to 50% relative to welds produced at 340 RPM. The lowest measured toughness was in the ASHR samples for both parameters. This region of the weld exhibited mixed mode stress-strain conditions and toughness 75% and 62% less than parent material. Toughness values for all samples failed to meet qualification requirements of both ASTM 1820 and BS 7448 due to non-uniform crack extension. Irregular crack extension was caused by the through thickness change in tensile properties due to welding and the affect this had on the plastic zone size compared to the thickness. Increased weld toughness from 340 RPM to 490 RPM was attributed to microstructural differences as a result of increased rotational speed. In addition, higher crack extensions were observed in the second weld pass relative to the first for both rotational speeds. This was attributed to weld tempering of the first pass by the second. The ASHR samples exhibited the highest crack extensions. In this location, the weld microstructure consisted of Widmanstatten ferrite, a microstructure known to be detrimental to toughness.

Forty ovine femurs were harvested and allocated into four testing groups; Fast-Normal, Fast- Decalcified, Slow-Normal, Slow-Decalcified. Contralateral pairings were used within these groups for closer comparison. Dynamic testing apparatus was designed and built allowing rates of strain similar to road traffic accidents to be investigated. These strain rates were achieved by using a pneumatic actuator to apply the load. Slow rate loading was achieved by testing with a commercially available mechanical testing machine at a rate of strain similar to that created by walking. Bone quality was altered by ultrasonically assisted decalcification in EDTA. Levels of mineral dissolution equivalent to the loss of bone mineral density (BMD) of a 75 year old woman were targeted. Whole bone was used for these experiments to facilitate comparison with real fracture radiographs obtained from NHS database. Fracture patterns and degree of comminution were similar between experimental and patient data. Bone is often analysed as a simple beam (engineers bending theory). This method of stress analysis was compared with a method that recognised the change in cross section over the length of the bone. Accounting for this had a highly significant effect on the calculated flexural modulus (p<0.0005).The length to depth ratio of whole bone indicates that shear forces cannot be ignored. The effect of the contribution from shear force on the deflection was investigated. After accounting for deflections due to shear, calculated normal strains agreed with literature values. Deflection due to shear was found to make a significant contribution to the deflection The effect of storage (freezing) on the mechanical properties at high strain rate was evaluated: no significant differences were found for force and deflection at failure. The main body of testing gave the following results: Normal quality bone, rate compared showed significant differences for Ultimate Stress, Ultimate Strain, Yield Strain, Flexural Modulus and Toughness. Demineralising bone resulted in no statistically significant differences between the loading rates for the Stress at failure. Yield Strain, Ultimate Strain, Flexural Modulus and Toughness did show significant differences. The fast loading tests showed significant differences when comparing quality for Stress at failure but not at Yield. Significant differences were found when comparing toughness. Slow loading tests showed significant differences between bone qualities for Stress at failure in contralateral pairs. No significant differences were found for strain or toughness. These results indicate that bone of normal quality can withstand higher than normal stresses for short durations. This ability is lost in demineralised bone. The high loading rate tests revealed closely matched strains at failure for both bone qualities, lending support to the strain based failure theory for bone at traumatic strain rates.

The primary objective of this study is to test the applicability to plastics of a fracture toughness testing tool developed for metals. The intent is to study pre-test conditioning of several plastic materials and the effect of the depth of the razor notch cut in the chevron notched fracture toughness test specimens. The study includes the careful preparation of samples followed by conditioning in various environments. Samples were subjected to laboratory air for a specific duration or to a controlled temperature-humidity condition as per the ASTM D1870. Some of the samples were subjected to vacuum conditioning under standard test specifications. Testing was conducted using the conventional three-point bend test as per ASTM D5045-95. ASTM E1304, which sets a standard for short rod and bar testing of metals and ceramics provides some basis for conducting chevron notched four-point bend tests to duplicate the toughness tool. Correlation of these results with the ASTM test samples is determined. The four-point bend test involves less specimen machining as well as time to perform the fracture toughness tests. This study of fracture toughness testing has potential for quality control as well as the fracture property determination.