Product Engineering and Performance Testing in Relation to Strength Design of Furniture

This article contains a narrative description of the history, current status, and possible future progress of the product engineering, strength design, and performance testing of furniture. Product engineering is covered both in general and from a furniture perspective. Strength design of furniture forms the essential part of the article.Reliability concepts are depicted in general both in their application to furniture and in their incorporation into standards for performance testing. The major objective of reliability and performance testing is to improve the durability and safety of furniture products and to predict failure or unexpected problems associated with them.Testing and evaluation are needed to obtain safe and reliable furniture and should provide pertinent expected performance information to manufacturers and customers alike. Both the history of development of strength design and its current stage of development are treated, along with suggestions for its use in improvement of furniture construction. In conclusion, an integrated methodology for the production of high strength furniture in view of current technological improvements is outlined

Pelvic organ prolapse and collagen-associated disorders

Contains fulltext : 109010.pdf (publisher's version ) (Open Access)INTRODUCTION AND HYPOTHESIS: Pelvic organ prolapse (POP) and other disorders, such as varicose veins and joint hypermobility, have been associated with changes in collagen strength and metabolism. We hypothesized that these various disorders were more prevalent in both POP patients and their family members. METHODS: In this study, the prevalence of various collagen-associated disorders, including POP, was compared between POP patients (n = 110) and control patients (n = 100) and their first and second degree family members. RESULTS: POP patients reported a higher prevalence of varicose veins, joint hypermobility and rectal prolapse and were more likely to have family members with POP as compared to the control group (p < 0.01). In contrast, the family members of the POP group did not report a higher prevalence of collagen-associated disorders compared to the family members of the control group (p = 0.82). CONCLUSIONS: POP and other collagen-associated disorders may have a common aetiology, originating at the molecular level of the collagens.1 maart 201

LOWER TOLERANCE LIMIT APPROACH TO EQUATION-BASED RATIONAL DESIGN VALUES FOR T-SHAPED MORTISE AND TENON JOINTS

A nonlinear regression expression was fitted to the test data obtained from a study of the bending moment capacity of 320 rectangular T-shaped mortise and tenon furniture joints consisting of 64 configurations of five specimens each. A statistical lower tolerance limit approach was then used to explore the degree to which these values should be reduced when used for design purposes and the confidence that a user might have in these reductions. The procedure followed was to apply statistical lower tolerance limit techniques to the ratios obtained by dividing each test value by its corresponding estimated value. To gain insight into the relationship of a specific confidence–proportion level and its corresponding reduction factor on the percentage of an estimated value that could be used for design purposes, lower tolerance limits were computed for four confidence–proportion levels. The results illustrate a statistical technique that can be used to determine reduction factors and the impact of the selection of any of the given confidence–proportion levels on design values.

LOWER TOLERANCE LIMIT APPROACH TO EQUATION-BASED RATIONAL DESIGN VALUES FOR L-SHAPED MORTISE AND TENON JOINTS

Statistical lower tolerance limits (LTLs) were computed for the ratios obtained by dividing the test values for 360 L-shaped rectangular mortise and tenon joints consisting of 72 different configurations of five specimens each by the corresponding values estimated by a nonlinear-regression expression fitted to the test data. LTLs were computed for the resulting ratios at the 75∣75, 90∣75, 75∣90, and 90∣90 confidence∣proportion levels. At these levels, the corresponding LTLs amounted to 88.1%, 87.4%, 75.8%, and 74.9%, respectively, of the estimates. The percentages of values that fell below the above stated LTLs were 24.2%, 23.3%, 8.3%, and 7.5%. On average, 53% of the test values below a given tolerance limit fell in the range of 90-99% of that limit. Differences between 75∣75 and 90∣75 limits as well as between 75∣90 and 90∣90 limits were sufficiently small that the greater confidence level appears desirable. This study is too limited in scope to suggest the appropriate confidence∣proportion level that might be used in determining design values for joints as a percentage of estimated values, but it does raise the question and emphasizes the importance of determining what percentage of failure is acceptable along with what level of confidence is appropriate for furniture design.  

LOWER TOLERANCE LIMIT APPROACH TO EQUATION-BASED RATIONAL DESIGN VALUES FOR L-SHAPED MORTISE AND TENON JOINTS

Statistical lower tolerance limits (LTLs) were computed for the ratios obtained by dividing the test values for 360 L-shaped rectangular mortise and tenon joints consisting of 72 different configurations of five specimens each by the corresponding values estimated by a nonlinear-regression expression fitted to the test data. LTLs were computed for the resulting ratios at the 75∣75, 90∣75, 75∣90, and 90∣90 confidence∣proportion levels. At these levels, the corresponding LTLs amounted to 88.1%, 87.4%, 75.8%, and 74.9%, respectively, of the estimates. The percentages of values that fell below the above stated LTLs were 24.2%, 23.3%, 8.3%, and 7.5%. On average, 53% of the test values below a given tolerance limit fell in the range of 90-99% of that limit. Differences between 75∣75 and 90∣75 limits as well as between 75∣90 and 90∣90 limits were sufficiently small that the greater confidence level appears desirable. This study is too limited in scope to suggest the appropriate confidence∣proportion level that might be used in determining design values for joints as a percentage of estimated values, but it does raise the question and emphasizes the importance of determining what percentage of failure is acceptable along with what level of confidence is appropriate for furniture design.  

EFfect of Adhesive Type and Tenon Size on Bending Moment Capacity and Rigidity of T-Shaped Furniture Joints Constructed of Turkish Beech and Scots Pine

Tests were carried out to determine the effect of wood species, adhesive type, and tenon width and length on static bending moment capacity and rigidity of T-shaped mortise and tenon furniture joints. For this purpose, 320 round-edged mortise and tenon joint specimens were constructed—half of Scots pine (Pinus sylvestris L.) and half of Turkish beech (Fagus orieantalis L.)—and subjected to static bending loads. Tenons varied 30-60 mm wide and 20-45 mm long. Joint specimens were assembled with 65% solid polyvinyl acetate and polyurethane adhesives. Results of the tests indicated that the joints became stronger and stiffer as either tenon width or tenon length increased. Results also indicated that tenon length had a more significant effect on moment capacity of joints than tenon width, whereas tenon width had a more significant effect on joint rigidity than tenon length. Bending moment capacity of the joints ranged from a low of 125 Nm for joints with tenons 30 mm wide x 20 mm long to a maximum of 393 Nm for joints with tenons 60 mm wide x 45 mm long. Rigidity of the joints ranged from a low of 2278 Nm/rad for joints with tenons 30 mm wide x 20 mm long to a maximum of 5733 Nm/rad for joints with tenons 60 mm wide x 40 mm long. An empirically derived expression was developed to predict average ultimate bending moment capacity