Tool wear analysis in sheet metal stamping

This thesis advances the understanding of die wear in sheet metal stamping. It was found that transient conditions exist at the die radius, resulting in severe contact pressures that are critical to the wear behaviour. The findings challenge applicability of traditional wear tests and models for sheet metal stamping processes.

Deformation and frictional heating in relation to wear in sheet metal stamping

In the automotive industry, press production rates often need to be reduced in order to minimize tool wear issues and successfully stamp advanced high strength steels. This indicates that heating affects may be important. This paper examines friction and deformational heating at the die radius during sheet metal stamping, using finite element analysis. The results show that high temperatures, of up to 130°C, can occur at the die radius surface. Such behavior has not been previously reported in the literature, for what is expected to be ‘cold’ sheet metal stamping conditions. It will be shown that the temperature rise is due to the increased contact stresses and increased plastic work, associated with stamping AHSS. Consequently, new insights into the local contact conditions in sheet metal stamping were obtained. The outcomes of this work may impact the wear models and tests employed for future tool wear analyses in sheet metal stamping.

Sliding distance, contact pressure and wear in sheet metal stamping

This paper directly examines the contact sliding distance experienced during a typical sheet metal stamping process-an area that has largely been neglected in the literature. A method to numerically quantify the sliding distance is proposed. The sliding distance predicted from this method, and the contact pressure obtained from numerical simulation, allow the recently identified time-dependent contact conditions on the die and blank surfaces to be completely characterized. Consequently, a new insight into the wear/galling that occurs at the die radius in sheet metal stamping is gained. The results show that the region close to zero degrees on the die radius is likely to experience the most wear, with the identified transient stage contributing to a large proportion of the total wear. Additionally, the region on the blank surface often observed to be heavily burnished - the die impact line - is estimated to experience the highest wear severity due to the transient contact conditions. The proposed method to numerically quantify the sliding contact conditions can be applied as a general approach to study any other two-body sliding contact situations.

Effects of temperature in relation to sheet metal stamping

The demand to reduce the use of lubricants and increase tool life in sheet metal stamping has resulted in increased research on the sliding contact between the tool and the sheet materials. Unlubricated sliding wear tests for soft carbon steel sliding on D2 tool steel were performed using a pin-on-disk tribometer. The results revealed that temperature has an influencing role in the wear of tool steel and that material transfer between tool and sheet can be minimized at a certain temperature range in sheet metal stamping.

Springback data from stamping and simulating the forming of advanced high strength steel

This dataset is comprised of a spreadsheet of simulation result files, cross-section geometries of stamped parts, strain results of cross-section of stamped parts, simulation data (strain stress displacement energies), and variation data of material properties of a single coil. This data is a collection of both experimental and simulation results from industrial and laboratory stamping of advanced high strength steels (AHSS). The steels that were stamped were a typical high-strength low-alloy (HSLA) steel, a transformation-induced plasticity (TRIP) steel, a super HSLA steel, and a dual phase (DP) steel. The selected part was an automatic Ford Falcon front cross-member component using the Ford Geelong stamping plant. The variation of the material and stamped parts was also collected.

Prediction of FLD of sheet metals based on crystal plasticity model

 In some advanced sheet metal forming processes such as the incremental forming process, a local fracture strain after necking is very important. In order to accurately predict necking and fracture phenomena, a crystal plasticity model is introduced in the finite element analysis of tensile tests. A tensile specimen is modeled by many grains that have their own crystalline orientation. And each of the grains is discretized by many elements. Using this analysis, necking behavior of a tensile specimen can be predicted without any initial imperfections. A damage model is also implemented to predict sudden drops of load carrying capacity after necking and to reflect the void nucleation and growth of the severely deformed region. From an analysis of the tensile test, the necking behavior is well predicted. Finally, analyses are carried out for various strain paths, and FLDs up to necking and fracture are predicted.

Forming behaviour analysis and constitutive modelling of Ti-6Al-4V at room temperature.

 A constitutive model was proposed in this thesis and a promising approach for accurate prediction of forming behaviour of high strength titanium alloy sheet metal forming at room temperature is presented. Outcomes showed a potential solution of cold roll forming of this material for aerospace and automotive structural applications.

An audio signal based model for condition monitoring of sheet metal stamping process

Tool condition monitoring is an important factor in ensuring manufacturing efficiency and product quality. Audio signal based methods are a promising technique for condition monitoring. However, the influence of interfering signals and background noise has hindered the use of this technique in production sites. Blind signal separation (BSS) has the potential to solve this problem by recovering the signal of interest out of the observed mixtures, given that the knowledge about the BSS model is available. In this paper, we discuss the development of the BSS model for sheet metal stamping with a mechanical press system, so that the BSS techniques based on this model can be developed in future. This involves conducting a set of specially designed machine operations and developing a novel signal extraction technique. Also, the link between stamping process conditions and the extracted audio signal associated with stamping was successfully demonstrated by conducting a series of trials with different lubrication conditions and levels of tool wear.

Sheet Metal Examples

A wall in the Sheet Metal Department at the New York Trade School shows many examples of duct work, pipe, and decorative metal work that students learn to produce. Black and white photograph that is starting to fade.

Graduate of the Sheet Metal Department, Thomas Carlough

A 1946 graduate of the Sheet Metal Department, Thomas Carlough is pictured at work at the Triangle Sheet Metal Works, Inc. Original caption reads, "Thomas Carlough - Sheet Metal 1946. The Sheet Metal Draftsman lays out the duct work etc, for the ventilation and Air Conditioning of buildings." Black and white photograph with caption adhered to reverse.