Formability tests

Banabic D (2000) Forming limits of sheet metal. In Banabic D, Bunge HJ, Pohlandt K, Tekkaya AE (eds) Formability of metallic materials plastic anisotropy, formability testing, forming limits. Springer, Heidelberg/Berlin... 

There are two types of formability tests intrinsic and simulative. Intrinsic tests measure the basic material properties. They provide comprehensive data that are... 

Bhattacharyya et al. [26] showed that wood fibre-polypropylene composites are indeed formable. The sheets they manufactured used pinus radiate fibres along with polypropylene powder, for a total through thickness of 1.3 mm. Two types of composites were made, layered and homogeneous with polypropylene and wood fibres mixed during formation. Results showed a tensile modulus increase of up to 250% with a 25-30% fibre mass fraction. Several formability tests were studied, dome forming with matched die and cup drawing being most relevant. For both... 

Plan of experiments and geometrical details of the formability tests performed on truncated conical and pyramidal shapes with initial drawing angle and increasing drawing angle h) with depth... 

At the end of the nineteenth century, due to the development of the sheet forming technology, sheet metal formability became a research topic. Starting from that time, different tests have been proposed. AH of them are based on the measure of the maximum deformation that a sheet metal sample can reach. 

Formability (Damage), Fig. 6 (a) Shape of the specimens used in the Nakazima test (Nakazima and Kikuma 1967) (b) a set of specimens for a complete KLD (Courtesy by GOM company)... 

Formability (Damage), Fig. 11 Cup and cone shape in broken parts in a tensile test (along the shear bands)... 

The structure of an expert system for the analysis of sheet metal formability is illustrated by Fig. 10 (Lee et al. 1988). Besides software packages of finite element analysis and CAD, computer-aided process design also requires databases with FLDs for various working conditions. Experimental testing is a very valuable input for these databases, but it is also rather expensive. 

The punch height at fracture H) which is influenced by limit strain and strain distribution of a material has been used as a measure of stretch-bend formability. The conditions are selected in such a manner that the fracture takes place in the region of punch contact. All the testings are performed in the dry condition [59]. 

In both tests, the cup height at fracture (or, preferably, maximum load or punch force) is employed as the measure of stretchability or formability index. The preferred criterion for measuring this point is the maximum load. When this is not possible, the onset of a visible neck or fracture can be used, but this yields a slightly different value [1, 2). 

The problems with the Olsen and Erichsen tests are their inability to address formability in the plane-strain conditions, where approximately 85% of all fractures in automotive panels occur. This resulted in the development of stretchability tests that uses a much larger-diameter punch, a lock bead to prevent drawing-in, plane-strain stretch condition, and more rigorously defined test conditions. 

An alternative method of this test has been developed. The punch travel between the initial contact with the specimen and the onset of a drop in the punch load, which is associated with the formation of a visible crack, is determined and used instead of the ratio of diameters. This value, termed the formability index, correlates with the uniform elongation and, thus, with the n value for low-carbon steels. 

R Thompson. The LDH Test to Evaluate Sheet Metal Formability—Final Report of the LDH Committee of the North American Deep Drawing Research Group, SAE Technical Paper 930815, 1993. 

K10] Mechanical tests Hardness, formability, tensile and torsion properties... 

Traditional tensile, compression, and flexural tests are being supplemented by newer and more exacting requirements that include much more action in formability, instrumented impact, pressure, thermal environment simulation, and fatigue and fracture testing that can provide product life prediction. Data from these exhaustive tests are fed back to designers using finite element analysis and to customers as proof of quality. 

Formability of the polymer sheet blanks was evaluated by means of tensile tests and bi-axial circular (50mm) and elliptical (50/32mm) hydraulic bulge tests. The tensile tests were performed in a mechanical testing machine while the hydraulic bulge tests were performed in a universal sheet metal testing machine. Testing speed was constant and set to 5mm/min in both cases. 

Since PPS is crystalline we should expect it to produce blends with much better chemical resistance than amorphous materials such as PAES. It should also allow very substantial cost reduction and can improve melt flow. Union Carbide filed patents on PEEK/PPS blends as early as 1982 [15]. Kureha has developed materials with improved compatibility, melt flow, formability and mechanical properties [16] Ticona has filed patents on improved PEEK/PPS blends and the most recent patent provides a good summary of the historical developments [17]. Solvay has filed patents on PEEK/PPS blends for use in bearing surfaces - under the conditions tested the blends perform as well as pure PEEK compounds [18]. It is possible that this technology is used in some of Solvay s Avaspire grades. 

These are Al-Mg-Si alloys. They show an excellent formability, machinabihty, weldability and corrosion resistance. A1 6061, 6013 and 6063 are widely used. A1 6063 is well known for its excellent extrudibility and appUcations in automotive frames. Alloy 6061 and 6013 show excellent resistance to marine corrosion in loop tests... 

To draw a crude comparison with isotropic materials, such as sheet metals, this depth of cup constitutes an equivalent draw ratio (blank diameter/cup diameter) of approximately 2.9. Given that the theoretical maximum draw ratio for isotropic materials is about 2.7, this result compares very favorably, although it must be stated that a superior ratio value does not necessarily indicate superior performance for sheet forming. Thinning and surface finish must also be taken into account, and it should be pointed out that in this case the surface finish is clearly very poor due to matrix migration. Another measure of relevance is the areal draw ratio , the ratio of the final component area to the raw blank area. For woven fabrics, this has been found to be limited to 1.03, although in this cup the ratio is 1.51, demonstrating far superior formability. The material s resilience to local failure was also tested. A sharp draw punch nose radius, which would be expected to cause failure with sheet steel at very small draw ratios, was not observed in the... 

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