Geraint J. Williams

Hole Expansion of Aluminum Alloys for the Automotive Industry

The introduction of Aluminum alloys in the automotive industry due to their high strength‐to‐weight ratio has brought with it a number of technical hurdles which require overcoming in order that their full potential may be realized. One of the issues that require addressing is that of edge cracking, a phenomenon which is particularly difficult to predict. This is often observed during the initial drawing operation in a traditional automotive stamping plant. A useful measure of a materials susceptibility to edge cracking is the Hole Expansion Ratio. Currently there is a standard (ISO 16630) which provides for holes to be expanded by a conical punch, where the original hole is introduced via punching. This reflects the traditional processing route within the automotive industry. Investigations have been conducted using both conical and flat‐topped punches, as well as using drilling and reaming, and CNC machining to introduce the initial hole for comparison with the standard punched route in order to underst...

Influence of Rivet Tip Geometry on the Joint Quality and Mechanical Strengths of Self-Piercing Riveted Aluminium Joints

Due to the drive from legislations, fuel efficiency, and CO2 emission, the application of aluminium lightweight structures in automotive industry have been increased significantly. Self piercing riveting (SPR) has been one of the major joining technologies for aluminium structures due to its advantages to some traditional joining technologies. There are some standard parameters that will influence the joint quality and mechanical strengths of an SPR joint. However, even for the same parameters used, sometimes the joint quality and mechanical strengths of SPR joints could still be significantly different, which may cause joint failure or strength reduction. One reason found is the variation of rivet specifications between different batches. In this paper, the influence of rivet tip geometry on the joint quality and mechanical strengths was studied. The results showed that rivets with sharper tips flared more during riveting process, and joints with sharper rivets had higher lap shear strength; however, the influence of rivet geometry on T peel strength could be different for different rivets, and rivet tip geometry did not have an obvious influence on joint fatigue strengths.

The effect of setting velocity on the static and fatigue strengths of self-piercing riveted joints for automotive applications

In order to reduce vehicle weight to increase fuel efficiency and reduce C02 emission, more and more automotive manufacturers are now using lightweight materials, such as aluminium, to build part of or the whole body-in-white structure. Due to the advantages over other joining techniques, self-piercing riveting (SPR) is a main joining technique for aluminium structures. In this paper, the effect of setting velocity/force on the joint quality and performance was studied. It was found that in the range studied, the increase of setting velocity increased the static lap shear strength but reduced the static T peel strength of the SPR joints. The results also suggested that the setting velocity did not have significant influence on the lap shear fatigue strength, but the T peel fatigue strength of the joints was increasing with the increase of setting velocity until it reached certain value. An increase in the setting velocity led to a decrease in the rivet head height and an increase in the interlock. In this study, the results showed that the static lap shear strength of SPR joints increased after corrosion and the setting velocity in the range studied did not have obvious influence on the change of lap shear strength after corrosion.

Experimental Evaluation of Springback in Aluminium Alloys Using Optical Measurement and Numerical Analysis

The aim of this paper is to establish an efficient and effective means of understanding the springback behaviour of a 5xxx‐O and a 6xxx‐T61 series aluminium alloy. The tooling used for investigating the springback is a small U‐channel stamping draw die using two die radii of 8 or 12 mm and a punch radius of 12 mm. The samples were drawn to depths of 50 or 75 mm with a minimum of 5 samples being drawn for each condition. The U‐channel samples were then evaluated using an optical scanning technique and the springback values were calculated using a numerical analysis as developed by one of the authors. The comparison of the sidewall springback, sidewall curl and flange springback under different conditions is conducted and the effect of the draw depth and die radius on the final springback is shown. Statistical analyses of both the drawing condition and the scanning technique are conducted to understand the effect of process variation on the results obtained. The 6xxx series shows higher springback values wh...

T1268 Gut Bio-Regulation in Health and Disease: Fermentonomic Insights – A Pilot Study

Background: Resident colonic bacteria, principally anaerobes and firmicutes, ferment undigested fibre, leading to the formation of volatile organic compounds (VOC). These are passed in faeces but also possibly absorbed and excreted in the urine. We hypothesised that the “fermentation profile” (FP), as seen in faeces and urine, may differ in health and in inflammatory bowel disease (IBD), and in the latter may change as the patient responds to treatment. Aim: Pilot study to determine if FP in faeces and urine can be recognised and reliably measured and to examine if there were identifiable differences in health and IBD. Methods: Healthy volunteers n=2; Longitudinal study of IBD patients: ulcerative colitis (UC) n=1, studied when acutely ill and when better on treatment; Crohns disease (CD) n=1, at the beginning and during the course of Infliximab therapy. Samples of faeces and urine were analysed fresh and after storage for 2 weeks. VOC were released by heating (thermal desorption, TD) separated by gas chromatography (GC) and identified by mass spectroscopy (MS). The noise in GC data was cleaned using Clearview software ©Markes. Results: Initial technical developments were made using horse, cow and chicken faeces: each showed a very large number of peaks, some shared. Volunteers within-run variability: <15% for faeces but <10% for urine, reflecting its more uniform nature. Data from urine VOC is presented here. All individuals showed a wide range of peaks, which could be grouped into 5 broad categories (expressed as % of total compounds present). IBD patients showed higher levels of TAK but lower levels of TOA. The IBD VOC profile changed with improvement on treatment: CD: HB Index fell from 4 to 0 at week 6; the TOA and PG levels fluctuated. UC: SCA Index fell from 4 to 3; VOC profile showed changes similar to those in CD and in addition, loss of high molecular weight compounds. Conclusion: We have observed: 1 Clear differences in VOC profiles between healthy volunteers and IBD patients 2 Improvement in IBD during treatment was associated with change in VOC profile. We believe the study of FPs using TD-GC/MS offers new insights into gut health which have clinical relevance.

The Effect of Specimen Dimensions on Obtained Tensile Properties of Sheet Metals

A pilot study has been carried out to examine the effect of specimen dimensions on the obtained tensile properties of aluminium and steel sheet. The materials used were DP600 grade steel and AA5754 grade aluminium sheet. Four types of dog-bone samples with varying dimensions were tested for both materials. Standard tensile test procedures were performed using a universal test machine together with contacting extensometry. The GOM Aramis photogrammetric 2D strain mapping technique was also applied. The results suggest that for both steel and aluminium sheet materials, differing specimen dimensions have little effect on the obtained mechanical properties. Depending on the gauge length of extensometer chosen and the position at where necking occurred on the sample, the extensometry results and 2D strain mapping results slightly differed towards to the end of stress-strain curve. The failure mode between the chosen grades of steel and aluminium samples was observed to differ, as did the percentage of failures that occurred within the gauge length. All steel samples fractured across the specimen perpendicularly to the test direction; whilst fracture of aluminium samples occurred approximately 30 degrees from the perpendicular.