FATIGUE LIFE ESTIMATION IN RESISTANCE SPOT WELDS: INITIATION AND EARLY GROWTH PHASE

Abstract— The main objective of this research is to develop a model of fatigue crack initiation and early crack growth in resistance spot welds that is specimen independent. This objective is achieved by examining the stress state around a resistance spot weld. A general expression for the structural stress around the weld is formulated that is dependent only on the loading immediately surrounding the weld. As such, it is specimen independent.
An additional objective is to explore the feasibility of applying this fatigue crack initiation model of life estimation using structural response data from finite element analysis (FEA). This numerical technique is often used for evaluating structural integrity of assemblies. Limited verification examples show that the structural stress range as calculated from FEA reaction load data is capable of describing fatigue crack initiation and early crack growth in cyclically loaded resistance spot welds.     

Agonist action at D2(long) dopamine receptors: ligand binding and functional assays

Clinical pathways are being introduced by hospitals to reduce costs and control unnecessary variation in care. We studied 766 inpatients to measure the impact of a perioperative clinical pathway for patients undergoing knee replacement surgery on hospital costs. One hundred twenty patients underwent knee replacement surgery before the development of a perioperative clinical pathway, and 63 patients underwent knee replacement surgery after pathway implementation. As control groups, we contemporaneously studied 332 patients undergoing radical prostatectomy (no clinical pathway in place for these patients) and 251 patients undergoing hip replacement surgery without a clinical pathway (no clinical pathway and same surgeons as patients having knee replacement surgery). Total hospitalization costs (not charges), excluding professional fees, were computed for all patients. Mean (+/-SD) hospital costs for knee replacement surgery decreased from $21,709 +/- $5985 to $17,618 +/- $3152 after implementation of the clinical pathway. The percent decrease in hospitalization costs was 1.56-fold greater (95% confidence interval 1.02-2.28) in the knee replacement patients than in the radical prostatectomy patients and 2.02-fold greater (95% confidence interval 1.13-5.22) than in the hip replacement patients. If patient outcomes (e.g., patient satisfaction) remain constant with clinical pathways, clinical pathways may be a useful tool for incremental improvements in the cost of perioperative care. Implications: Doctors and nurses can proactively organize and record the elements of hospital care results in a clinical pathway, also known as "care pathways" or "critical pathways." We found that implementing a clinical pathway for patients undergoing knee replacement surgery reduced the hospitalization costs of this surgery.